Recoil pad

A recoil pad is a piece of rubber, foam, leather, or other soft material usually attached to the buttstock of a rifle or shotgun. Recoil pads may also be worn around the shoulder with straps, placing the soft material between the buttstock and the shoulder of the person firing the gun. The purpose of this device is to provide additional padding between the typically hard buttstock surface and the user's shoulder, to reduce the amount of felt recoil of the firearm, and to prevent slippage on the shooter's clothing while aiming.


Excelsior-Henderson Motorcycle

Excelsior-Henderson Motorcycle was a motorcycle manufacturing company located in Belle Plaine, Minnesota in the late 1990s.
History.
The company was originally founded as Hanlon Manufacturing Company by Daniel Hanlon during early 1993 in Burnsville, Minnesota, United States. The company secured the rights of motorcycle names previously used by the former Excelsior-Henderson company, that was owned by Ignatz Schwinn of the Schwinn company. The company proceeded to design and manufacture OEM proprietary motorcycles with design originality of the former Excelsior and Henderson motorcycles.
Factory.
From 1997 to 1998, the company constructed a factory in Belle Plaine, Minnesota. The factory was equipped for a capacity of 10,000 motorcycles per year, and, with a few minor assembly and finishing line changes, would have had a capacity of 20,000. In 2009, the factory was converted to the headquarters of Cambria, a company specializing in quartz surfaces.
Production.
Excelsior-Henderson introduced it first production model, the Super X, in December 1998, and commenced production in early 1999. The company developed the Super X motorcycle as a new proprietary motorcycle, including a new engine, frame, and all related drive and styling components, adopting styling from the earlier Excelsior-Henderson motorcycles from the 1905-1931 timeframe. The company established 140 dealers throughout the United States. The motorcycles averaged an MSRP around $18,500. Via the assembly line, the company produced for retail sale approx. 1900 motorcycles in various configurations; 1161 units in model year 1999, and 720 units in model year 2000. In total, the company produced an estimated 1950 motorcycles, which would include motorcycles produced and not designed for retail dealer sales; such as dealer promotional bikes, test prototypes and non-assembly line produced motorcycles.
Chapter 11 Bankruptcy.
Excelsior-Henderson, having spent $100 million in capital over a seven year period and still several years from profitability, was unable to raise additional capital by late 1999. Therefore, on December 21, 1999, Excelsior-Henderson filed for reorganization under Chapter 11, Title 11, United States Code. As an outcome of the process, certain assets of the company were sold to a Florida investment group, which later filed for reorganization and no longer exists. Production of motorcycles never recommenced. According to former employees, the company’s failures can be attributed to ineptitude in growing a dealer network, micromanaging, and an unwillingness to accept and incorporate suggestion. Gary Fields, Deputy Commissioner of Minnesota’s Department of Trade and Economic Development, said that the state would be less likely to fund another startup based on the failures of Excelsior-Henderson.
Current Status.
On 16 December 2020, Cycle World reported Excelsior-Henderson's intellectual property had been purchased by Bajaj, a major manufacturer of motorcycles in India.


Slot-die coating

Slot-die coating is a coating technique for the application of solution, slurry, or extruded thin films onto typically flat substrates such as glass, metal, paper, fabric or plastic foils. The process was first developed for the industrial production of photographic papers in the 1950's. It has since become relevant in numerous commercial processes and nanomaterials related research fields.
Slot-die coating produces thin films via solution processing. The desired coating material is typically dissolved or suspended into a precursor solution or slurry (sometimes referred to as "ink") and delivered onto the surface of the substrate through a precise coating head known as a slot-die. The slot-die has a high aspect ratio outlet controlling the final delivery of the coating liquid onto the substrate. This results in the continuous production of a wide layer of coated material on the substrate, with adjustable width depending on the dimensions of the slot-die outlet. By closely controlling the rate of solution deposition and the relative speed of the substrate, slot-die coating affords thin material coatings with easily controllable thicknesses in the range of 10 nanometers to hundreds of micrometers after evaporation of the precursor solvent.
Commonly cited benefits of the slot-die coating process include its pre-metered thickness control, non-contact coating mechanism, high material efficiency, scalability of coating areas and throughput speeds, and roll-to-roll compatibility. The process also allows for a wide working range of layer thickness and precursor solution properties such as material choice, viscosity, and solids content. Commonly cited drawbacks of the slot-die coating process include its comparatively high complexity of apparatus and process optimization relative to similar coating techniques such as blade coating and spin coating. Furthermore, slot-die coating falls into the category of coating processes rather than printing processes. It is therefore better suited for coating of uniform, thin material layers rather than printing or consecutive buildup of complex images and patterns.
Coating apparatus.
Typical components.
Slot-die coating equipment is available in a variety of configurations and form factors. However, the vast majority of slot-die processes are driven by a similar set of common core components. These include:
Depending on the complexity of the coating apparatus, a slot-die coating system may include additional modules for e.g. precise positioning of the slot-die over the substrate, particulate filtering of the coating solution, pre-treatment of the substrate (e.g. cleaning and surface energy modification), and post-processing steps (e.g. drying, curing, calendering, printing, slitting, etc.).
Industrial coating systems.
Slot-die coating was originally developed for industrial use and remains primarily applied in production-scale settings. This is due to its potential for large-scale production of high-value thin films and coatings at a low operating cost via roll-to-roll and sheet-to-sheet line integration. Such roll-to-roll and sheet-to-sheet coating systems are similar in their intent for large-scale production, but are distinguished from each other by the physical rigidity of the substrates they handle. Roll-to-roll systems are designed to coat and handle flexible substrate rolls such as paper, fabric, plastic or metal foils. Conversely, sheet-to-sheet systems are designed to coat and handle rigid substrate sheets such as glass, metal, or plexiglass. Combinations of these systems such roll-to-sheet lines are also possible.
Both industrial roll-to-roll and sheet-to-sheet systems typically feature slot-dies in the range of 300 to 1000 mm in coating width, though slot-dies up to 4000 mm wide have been reported. Commercial slot-die systems are claimed to operate at speeds up to several hundred square meters per minute, with roll-to-roll systems typically offering higher throughput due to decreased complexity of substrate handling. Such large-scale coating systems can be driven by a variety of industrial pumping solutions including gear pumps, progressive cavity pumps, pressure pots, and diaphragm pumps depending on process requirements.
Roll-to-roll lines.
To handle flexible substrates, roll-to-roll lines typically use a series of rollers to continually drive the substrate through the various stations of the process line. The bare substrate originates at an "unwind" roll at the start of the line and is collected at a "rewind" roll at the end. Hence, the substrate is often referred to as a "web" as it winds its way through the process line from start to finish. When a substrate roll has been fully processed, it is collected from the rewind roll, allowing for a new, bare substrate roll to be mounted onto the unwind roller to begin the process again. Slot-die coating often comprises just a single step of an overall roll-to-roll process. The slot-die is typically mounted in a fixed position on the roll-to-roll line, dispensing coating fluid onto the web in a continuous or patch-based manner as the substrate passes by. Because the substrate web spans all stations of the roll-to-roll line simultaneously, the individual processes at these stations are highly coupled and must be optimized to work in tandem with each other at the same web speed.
Sheet-to-sheet lines.
The rigid substrates employed in sheet-to-sheet systems are not compatible with the roll-to-roll processing method. Sheet-to-sheet systems rely instead on a rack-based system to transport individual sheets between the various stations of a process line, where transfer between stations may occur in a manual or automated manner. Sheet-to-sheet lines are therefore more analogous to a series of semi-coupled batch operations rather than a single continuous process. This allows for easier optimization of individual unit operations at the expense of potentially increased handling complexity and reduced throughput. Furthermore, the need to start and stop the slot-die coating process for each substrate sheet places higher tolerance requirements on the leading and trailing edge uniformity of the slot-die step. In sheet-to-sheet lines, the substrate may be fixed in place as the substrate passes underneath on a moving support bed (sometimes referred to as a "chuck"). Alternatively, the slot-die may move during coating while the substrate remains fixed in place.
Lab-scale development tools.
Miniaturized slot-die tools have become increasingly available to support the development of new roll-to-roll compatible processes prior to the requirement of full pilot- and production-scale equipment. These tools feature similar core components and functionality as compared to larger slot-die coating lines, but are designed to integrate into pre-production research environments. This is typically achieved by e.g. accepting standard A4 sized substrate sheets rather than full substrate rolls, using syringe pumps rather than industrial pumping solutions, and relying upon hot-plate heating rather than large industrial drying ovens, which can otherwise reach lengths of several meters to provide suitable residence times for drying.
Because the slot-die coating process can be readily scaled between large and small areas by adjusting the size of the slot-die and throughput speed, processes developed on lab-scale tools are considered to be reasonably scalable to industrial roll-to-roll and sheet-to-sheet coating lines. This has led to significant interest in slot-die coating as a method of scaling new thin film materials and devices, particularly in the sphere of thin film solar cell research for e.g. perovskite and organic photovoltaics.
Common coating modalities.
Slot-die hardware can be applied in several distinct coating modalities, depending on the requirements of a given process. These include:
The dynamics of proximity coating have been extensively studied and applied over a wide range of scales and applications. Furthermore, the concepts governing proximity coating are relevant in understanding the behavior of other coating modalities. Proximity coating is therefore considered to be the default configuration for the purposes of this introductory article, though curtain coating and tensioned web over slot die configurations remain highly relevant in industrial manufacturing.
Key process parameters.
Film thickness control.
Slot-die coating is a non-contact coating method, in which the slot-die is typically held over the substrate at a height several times higher than the target wet film thickness. The coating fluid transfers from the slot-die to the substrate via a fluid bridge that spans the air gap between the slot-die lips and substrate surface. This fluid bridge is commonly referred to as the coating meniscus or coating bead. The thickness of the resulting wet coated layer is controlled by tuning the ratio between the applied volumetric pump rate and areal coating rate. Unlike in self-metered coating methods such as blade- and bar coating, the slot-die does not influence the thickness of the wet coated layer via any form of destructive physical contact or scraping. The height of the slot-die therefore does not determine the thickness of the wet coated layer. The height of the slot-die is instead significant in determining the quality of the coated film, as it controls the distance that must be spanned by the meniscus to maintain a stable coating process.
formula_1
Slot-die coating operates via a pre-metered liquid coating mechanism. The thickness of the wet coated layer (formula_2) is therefore significantly determined by the width of coating (formula_3), the volumetric pump rate (formula_4), and the coating speed, or relative speed between the slot-die and the substrate during coating (formula_5). Increasing the pump rate increases the thickness of the wet layer, while increasing the coating speed or coating width decreases the wet layer thickness. The coating width is typically a fixed value for a given slot-die process. Hence, pump rate and coating speed can be used to calculate, control, and adjust the wet film thickness in a highly predictable manner. However, deviation from this idealized relationship can occur in practice due to non-ideal behavior of materials and process components; for example when using highly viscoelastic fluids, or a sub-optimal process setup where fluid creeps up the slot-die component rather than transferring fully to the substrate.
formula_6
The final thickness of the dry layer after solvent evaporation (formula_7) is further determined by the solids concentration of the precursor solution (formula_8) and the volumetric density of the coated material in its final form (formula_9). Increasing the solids content of the precursor solution increases the thickness of the dry layer, while using a more dense material results a thinner dry layer for a given concentration.
Film quality control.
As with all solution processed coating methods, the final quality of a thin film produced via slot-die coating depends on a wide array of parameters both intrinsic and external to the slot-die itself. These parameters can be broadly categorized into:
Coating window parameters.
Under ideal conditions, the potential to achieve a defect-free film via slot-die is entirely governed by the coating window of the a given process. The coating window is a multivariable map of key process parameters, describing the range over which they can be applied together to achieve a defect-free film. Understanding the coating window behavior of a typical slot-die process enables operators to observe defects in a slot-die coated layer and intuitively determine a course of action for defect resolution. The key process parameters used to define the coating window typically include:
The coating window can be visualized by plotting two such key parameters against each other while assuming the others to remain constant. In an initial simple representation, the coating window can be described by plotting the relationship between viable pump rates and coating speeds for a given process. Excessive pumping or insufficient coating speeds result in defect spilling of the coating liquid outside of the desired coating area, while coating too quickly or pumping insufficiently results in defect breakup of the meniscus. The pump rate and coating speed can therefore be adjusted to directly compensate for these defects, though changing these parameters also affects wet film thickness via the pre-metered coating mechanism. Implicit in this relationship is the effect of the slot-die height parameter, as this affects the distance over which the meniscus must be stretched while remaining stable during coating. Raising the slot-die higher can thus counteract spilling defects by stretching the meniscus further, while lowering the slot-die can counteract streaking and breakup defects by reducing the gap that the meniscus must breach. Other helpful coating window plots to consider include the relationship between fluid capillary number and slot-die height, as well as the relationship between pressure across the meniscus and slot-die height. The former is particularly relevant when considering changes in fluid viscosity and surface tension (i.e. the effect of coating various materials with significantly different rheology), while the latter is relevant in the context of applying a vacuum box at the upstream face of the meniscus to stabilize the meniscus against breakup.
Downstream process effects.
In reality, the final quality of a slot-die coated film is heavily influenced by a variety of factors beyond the parameter boundaries of the ideal coating window. Surface energy effects and drying effects are examples of common downstream effects with a significant influence on final film morphology. Sub-optimal matching of surface energy between the substrate and coating fluid can cause dewetting of the liquid film after it has been applied to the substrate, resulting in pinholes or beading of the coated layer. Sub-optimal drying processes are also often noted to influence film morphology, resulting in increased thickness at the edge of a film caused by the coffee ring effect. Surface energy and downstream processing must therefore be carefully optimized to maintain the integrity of the slot-die coated layer as it moves through the system, until the final thin film product can be collected.
External effects.
Slot-die coating is a highly mechanical process in which uniformity of motion and high hardware tolerances are critical to achieving uniform coatings. Mechanical imperfections such as jittery motion in the pump and coating motion systems, poor parallelism between the slot-die and substrate, and external vibrations in the environment can all lead to undesired variations in film thickness and quality. Slot-die coating apparatus and its environment must therefore be suitably specified to meet the needs of a given process and avoid hardware- and environment-derived defects in the coated film.
Applications.
Industrial applications.
Slot-die coating was originally developed for the commercial production of photographic films and papers. In the past several decades it has become a critical process in the production of adhesive films, flexible packaging, transdermal and oral pharmaceutical patches, LCD panels, multi-layer ceramic capacitors, lithium-ion batteries and more.
Research applications.
With growing interest in the potential of nanomaterials and functional thin film devices, slot-die coating has become increasingly applied in the sphere of materials research. This is primarily attributed to the flexibility, predictability and high repeatability of the process, as well as its scalability and origin as a proven industrial technique. Slot-die coating has been most notably employed in research related to flexible, printed, and organic electronics, but remains relevant in any field where scalable thin film production is required.
Examples of research enabled by slot-die coating include:


Balancing machine

A balancing machine is a measuring tool used for balancing rotating machine parts such as rotors for electric motors, fans, turbines, disc brakes, disc drives, propellers and pumps. The machine usually consists of two rigid pedestals, with suspension and bearings on top supporting a mounting platform. The unit under test is bolted to the platform and is rotated either with a belt-, air-, or end-drive. As the part is rotated, the vibration in the suspension is detected with sensors and that information is used to determine the amount of unbalance in the part. Along with phase information, the machine can determine how much and where to add or remove weights to balance the part.
Hard-bearing vs. soft-bearing.
There are two main types of balancing machines, hard-bearing and soft-bearing. The difference between them, however, is in the suspension and not the bearings.
In a hard-bearing machine, balancing is done at a frequency lower than the resonance frequency of the suspension. Thus the suspension's resulting displacement is caused by the centrifugal force generated by the unbalance of the rotor. In a soft-bearing machine, balancing is done at a frequency higher than the resonance frequency of the suspension. The suspension's displacement is dictated by the distance of the rotor's principal axis of inertia relative to the rotor's rotational axis defined by the rotor bearings. Both types of machines have various advantages and disadvantages. A hard-bearing machine is generally more versatile and can handle pieces with greatly varying weights, because hard-bearing machines are measuring centrifugal forces and require only a one-time calibration. Only five geometric dimensions need to be fed into the measuring unit and the machine is ready for use. Therefore, it works very well for low- and middle-size volume production and in repair workshops.
A soft-bearing machine is not so versatile with respect to amount of rotor weight to be balanced. The preparation of a soft-bearing machine for individual rotor types is more time consuming, because it needs to be calibrated for different part types which makes the process accuracy dependent on the operator's knowledge and skill. With measuring equipment capable of storing the setup calibration parameters, the need for recalibration becomes unnecessary as long as the original rotor setup on the balancing machine at the time of its calibration is duplicated. Thus use of dedicated fixture for each type of rotor may come at additional cost but offers the advantage of better balancing process accuracy and less dependent on the machine operator's skill level. With the machine setup a little bit more tedious, it is generally more suitable for high-production volume and high-precision balancing tasks. The latter being required when the rotor has a high service speed, or critical application (see ISO 201940 for recommended balancing tolerance.)
Hard- and soft-bearing machines can be automated to remove weight automatically, such as by drilling or milling, but hard-bearing machines are more robust and reliable. Both machine principles can be integrated into a production line and loaded by a robot arm or gantry, requiring very little human control.
How it works.
With the rotating part resting on the bearings, a vibration sensor is attached to the suspension. In most soft-bearing machines, a velocity sensor is used. This sensor works by moving a magnet in relation to a fixed coil that generates voltage proportional to the velocity of the vibration. Accelerometers, which measure acceleration of the vibration, can also be used.
A photocell (sometimes called a phaser), proximity sensor, or encoder is used to determine the rotational speed, as well as the relative phase of the rotating part. This phase information is then used to filter the vibration information to determine the amount of movement, or force, in one rotation of the part. Also, the time difference between the phase and the vibration peak gives the angle at which the unbalance exists. Amount of unbalance and angle of unbalance give an unbalance vector.
Calibration is performed by adding a known weight at a known angle. In a soft-bearing machine, trial weights must be added in correction planes for each part. This is because the location of the correction planes along the rotational axis is unknown, and therefore it is unknown how much a given amount of weight will affect the balance. By using trial weights, a known weight at a known angle is added, and getting the unbalance vector caused by it.
Other balancing machine types.
Static balancing machines differ from hard- and soft-bearing machines in that the part is not rotated to take a measurement. Rather than resting on its bearings, the part rests vertically on its geometric center. Once at rest, any movement by the part away from its geometric center is detected by two perpendicular sensors beneath the table and returned as unbalance. Static balancers are often used to balance parts with a diameter much larger than their length, such as fans. The advantages of using a static balancer are speed and price. However a static balancer can only correct in one plane, so its accuracy is limited.
A blade balancing machine attempts to balance a part in assembly, so minimal correction is required later on. Blade mass balancing is typically done for short blades, while long blades may require moment weighing in one or two axes. Long blades that are also wide may require its axial moment to be measured to optimize hub stress distribution. Blade balancers are used on parts such as fans, propellers, and turbines. On a blade balancer, the weight and/or moment of each blade to be assembled is entered into a balancing software package. The software then sorts the blades and attempts to find the blade arrangement with the least amount of unbalance. Lesser amount of unbalance correction weight in the final balancing process means lesser (concentrated) stress to the rotor assembly.
Portable balancing machines are used to balance parts that cannot be taken apart and put on a balancing machine, usually parts that are currently in operation such as turbines, pumps, and motors. Portable balancers come with displacement sensors, such as accelerometers, and a photocell, which are then mounted to the pedestals or enclosure of the running part. Based on the vibrations detected, they calculate the part's unbalance. Many times these devices contain a spectrum analyzer so the part condition can be monitored without the use of a photocell and non-rotational vibration can be analyzed.


Extrusion coating

Extrusion coating is the coating of a molten web of synthetic resin onto a substrate material. It is a versatile coating technique used for the economic application of various plastics, notably polyethylene, onto paperboard, corrugated fiberboard, paper, aluminium foils, cellulose, Non-wovens, or plastic films.
Process.
Coating.
The actual process of extrusion coating involves extruding resin from a slot die at temperatures up to 320°C directly onto the moving web which may then passed through a nip consisting of a rubber covered pressure roller and a chrome plated cooling roll. The latter cools the molten film back into the solid state and also imparts the desired finish to the plastic surface. The web is normally run much faster than the speed at which the resin is extruded from the die, creating a coating thickness which is in proportion to the speed ratio and the slot gap.
Laminating.
Extrusion laminating is a similar process except that the extruded hot molten resin acts as the bonding medium to a second web of material.
Co-extrusion.
Co-extrusion is, again, a similar process but with two, or more, extruders coupled to a single die head in which the individually extruded melts are brought together and finally extruded as a multi-layer film.
Uses.
The market for extrusion coating includes a variety of end-use applications such as liquid packaging, photographic, flexible packaging, mill and industrial wrappings, transport packaging, sack linings, building, envelopes, medical/hygiene, and release base.


Label printer

A label printer is a computer printer that prints on self-adhesive label material and/or card-stock (tags). A label printer with built-in keyboard and display for stand-alone use (not connected to a separate computer) is often called a label maker. Label printers are different from ordinary printers because they need to have special feed mechanisms to handle rolled stock, or tear sheet (fanfold) stock. Common connectivity for label printers include RS-232 serial, Universal Serial Bus (USB), parallel, Ethernet and various kinds of wireless. Label printers have a wide variety of applications, including supply chain management, retail price marking, packaging labels, blood and laboratory specimen marking, and fixed assets management.
Mechanisms.
Label printers use a wide range of label materials, including paper and synthetic polymer ("plastic") materials. Several types of print mechanisms are also used, including laser and impact, but thermal printer mechanisms are perhaps the most common.
There are two common types of thermal printer.
There are three grades of ribbon for use with thermal transfer printers. Wax is the most popular with some smudge resistance, and is suitable for matte and semi-gloss paper labels. Wax/resin is smudge resistant, suitable for semi-gloss paper and some synthetic labels. Resin alone is scratch and chemical resistant, suitable for coated synthetic labels.
When printing on continuous label stock, there is a tendency for the print location to shift slightly from label to label. To ensure registration of the print area with the target media, many label printers use a sensor that detects a gap, notch, line or perforation between labels. This allows the printer to adjust the intake of label stock so that the print aligns correctly with the media.
Types.
Label printer capabilities vary between home, corporate and industrial-oriented models.


Continuous design

Evolutionary design, continuous design, evolutive design, or incremental design is directly related to any modular design application, in which components can be freely substituted to improve the design, modify performance, or change another feature at a later time.
Informatics.
In particular, it applies (with the name continuous design) to software development. In this field it is a practice of creating and modifying the design of a system as it is developed, rather than purporting to specify the system completely before development starts (as in the waterfall model). Continuous design was popularized by extreme programming. Continuous design also uses test driven development and refactoring.
Martin Fowler wrote a popular book called "Refactoring", as well as a popular article entitled "Is Design Dead?", that talked about continuous/evolutionary design. James Shore wrote an article in IEEE titled "Continuous Design".
Industrial design.
Modular design states that a product is made of subsystems that are joined together to create a full product. The above design model defined in electronics and evolved in industrial design into well consolidated industrial standards related to platform concept and its evolution.


TMEIC

  is a joint venture between Toshiba and Mitsubishi Electric headquartered in Tokyo, Japan, specializing in industrial electric and automation systems for industrial plants. The company develops and produces power electronics apparatus, electric motors, drives, and uninterruptible power supplies. TMEIC has worldwide operations with approximately 2000 employees.
History.
Tokyo Electric Company, the predecessor of Toshiba Corporation, was founded in 1896.
Mitsubishi Electric Corporation was founded in 1921.
In 1999, Toshiba and Mitsubishi Electric established TMA Electric Corporation (TMAE), a joint venture specializing in rotating machinery.
In 2000, Toshiba and General Electric Company formed Toshiba GE Automation Systems (TGAJ) operating in sales and engineering of industrial plant systems.
Toshiba and Mitsubishi Electric have decided to unify TMAE, TGAJ and their industrial systems division to form a joint venture named Toshiba Mitsubishi-Electric Industrial Systems Corporation (TMEIC).
TMEIC started business on October 1, 2003.


Facing (machining)

Facing in machining can be used in two different areas: facing on a milling machine and facing on a lathe. Facing on the milling machine involves various milling operations, but primarily face milling. On the lathe, facing is commonly used in turning and boring operations. Other operations remove material in ways similar to facing, for example, planing, shaping, and grinding, but these processes are not labeled by the term "facing."
Facing lathe operation.
Facing on the lathe uses a facing tool to cut a flat surface perpendicular to the work piece's rotational axis. A facing tool is mounted into a tool holder that rests on the carriage of the lathe. The tool will then feed perpendicularly across the part's rotational axis as it spins in the jaws of the chuck. A user will have the option to hand feed the machine while facing, or use the power feed option. For a smoother surface, using the power feed option is optimal due to a constant feed rate. Facing will take the work piece down to its finished length very accurately. Depending on how much material needs to be taken off, a machinist can choose to take roughing or finishing cuts. Factors that affect the quality and effectiveness of facing operations on the lathe are speeds and feeds, material hardness, cutter size, and how the part is being clamped down.
Face milling operation.
Facing on a milling machine is the process of cutting a flat surface perpendicular to the axes of the milling cutter. This process removes the material by rotating the facing tool in the counterclockwise direction as the table feeds the work piece across the cutter. Face milling can be achieved with an end mill, but is often done with a face mill, shell mill or a fly cutter. Face milling can be done in both manual machining and CNC machining. To obtain a smoother surface finish it is best to let the machine feed the table. Newer manual milling machines and CNC machines will have this option, but older milling machines will not. When available, use the machine feed instead of manually feeding the part. This will provide an optimal surface finish due to the constant feed maintained by the mill. Hand feeding the table will allow human error into the process. Machinists also have the option to take roughing cuts and finish cuts. Factors that affect the quality and effectiveness of facing operations on the mill are speeds and feeds, material hardness, cutter size, and how the part is being clamped down.
Spotfacing is the facing of spots (localized areas), such as the bearing surfaces on which bolt heads or washers will sit.


Foundry model

The foundry model is a microelectronics engineering and manufacturing business model consisting of a semiconductor fabrication plant, or foundry, and an integrated circuit design operation, each belonging to separate companies or subsidiaries.
Integrated device manufacturers (IDMs) design and manufacture integrated circuits. Many companies, known as fabless semiconductor companies, only design devices; merchant or pure play foundries only manufacture devices for other companies, without designing them. Examples of IDMs are Intel, Samsung, and Texas Instruments,
examples of pure play foundries are GlobalFoundries, TSMC, and UMC, and examples of fabless companies are AMD, Nvidia, and Qualcomm.
Integrated circuit production facilities are expensive to build and maintain. Unless they can be kept at nearly full use, they will become a drain on the finances of the company that owns them. The foundry model uses two methods to avoid these costs: fabless companies avoid costs by not owning such facilities. Merchant foundries, on the other hand, find work from the worldwide pool of fabless companies, through careful scheduling, pricing, and contracting, keep their plants in full use.
History.
Companies that both designed and produced the devices were originally responsible for manufacturing microelectronic devices. These manufacturers were involved in both the research and development of manufacturing processes and the research and development of microcircuit design.
The first pure play semiconductor company is the Taiwan Semiconductor Manufacturing Corporation, a spin-off of the government Industrial Technology Research Institute, which split its design and fabrication divisions in 1987, a model advocated for by Carver Mead in the U.S., but deemed too costly to pursue. The separation of design and fabrication became known as the foundry model, with fabless manufacturing outsourcing to semiconductor foundries.
Fabless semiconductor companies do not have any semiconductor fabrication capability; and contract production with a merchant foundry manufacturer. The fabless company concentrates on the research and development of an IC-product; the foundry concentrates on manufacturing and testing the physical product. If the foundry does not have any semiconductor design capability, it is a pure-play semiconductor foundry.
An absolute separation into fabless and foundry companies is not necessary. Some companies continue to exist that perform both operations and benefit from the close coupling of their skills. Some companies manufacture some of their own designs and contract out to have others manufactured or designed, in cases where they see value or seek special skills. The foundry model is a business vision that seeks to optimize productivity.
MOSIS.
The very first merchant foundries were part of the MOSIS service. The MOSIS service gave limited production access to designers with limited means, such as students, university researchers, and engineers at small startups. The designer submitted designs, and these submissions were manufactured with the commercial company's extra capacity. Manufacturers could insert some wafers for a MOSIS design into a collection of their own wafers when a processing step was compatible with both operations. The commercial company (serving as foundry) was already running the process, so they were effectively being paid by MOSIS for something they were already doing. A factory with excess capacity during slow periods could also run MOSIS designs to avoid having expensive capital equipment stand idle.
Under-use of an expensive manufacturing plant could lead to the financial ruin of the owner, so selling surplus wafer capacity was a way to maximize the fab's use. Hence, economic factors created a climate where fab operators wanted to sell surplus wafer-manufacturing capacity and designers wanted to purchase manufacturing capacity rather than try to build it.
Although MOSIS opened the doors to some fabless customers, earning additional revenue for the foundry and providing inexpensive service to the customer, running a business around MOSIS production was difficult. The merchant foundries sold wafer capacity on a surplus basis, as a secondary business activity. Services to the customers were secondary to the commercial business, with little guarantee of support. The choice of merchant dictated the design, development flow, and available techniques to the fabless customer. Merchant foundries might require proprietary and non-portable preparation steps. Foundries concerned with protecting what they considered trade secrets of their methodologies might only be willing to release data to designers after an onerous nondisclosure procedure.
Dedicated foundry.
In 1987, the world's first dedicated merchant foundry opened its doors: Taiwan Semiconductor Manufacturing Company (TSMC). The distinction of 'dedicated' is in reference to the typical merchant foundry of the era, whose primary business activity was building and selling of its own IC-products. The dedicated foundry offers several key advantages to its customers: first, it does not sell finished IC-products into the supply channel; thus a dedicated foundry will never compete directly with its fabless customers (obviating a common concern of fabless companies). Second, the dedicated foundry can scale production capacity to a customer's needs, offering low-quantity shuttle services in addition to full-scale production lines. Finally, the dedicated foundry offers a "COT-flow" (customer owned tooling) based on industry-standard EDA systems, whereas many IDM merchants required its customers to use proprietary (non-portable) development tools. The COT advantage gave the customer complete control over the design process, from concept to final design.
Foundry sales leaders by year.
2009–2007.
As of 2009, the top 17 semiconductor foundries were:
2008–2006.
As of 2008, the top 18 pure-play semiconductor foundries were:
2007–2005.
As of 2007, the top 14 semiconductor foundries include:
For ranking in worldwide:
2004.
As of 2004, the top 10 pure-play semiconductor foundries were:
Financial and IP issues.
Like all industries, the semiconductor industry faces upcoming challenges and obstacles.
The cost to stay on the leading edge has steadily increased with each generation of chips. The financial strain is being felt by both large merchant foundries and their fabless customers. The cost of a new foundry exceeds $1 billion. These costs must be passed on to customers. Many merchant foundries have entered into joint ventures with their competitors in an effort to split research and design expenditures and fab-maintenance expenses.
Chip design companies sometimes avoid other companies' patents simply by purchasing the products from a licensed foundry with broad cross-license agreements with the patent owner.
Stolen design data is also a concern; data is rarely directly copied, because blatant copies are easily identified by distinctive features in the chip,
placed there either for this purpose or as a byproduct of the design process. However, the data including any procedure, process system, method of operation or concept may be sold to a competitor, who may save months or years of tedious reverse engineering.


Wafer-level packaging

Wafer-level packaging (WLP) is a process where packaging components are attached to an integrated circuit (IC) "before" the wafer – on which the IC is fabricated – is diced. In WSP, the top and bottom layers of the packaging and the solder bumps are attached to the integrated circuits while they are still in the wafer. This process differs from a conventional process, in which the wafer is sliced into individual circuits (dice) before the packaging components are attached.
WLP is essentially a true chip-scale package (CSP) technology, since the resulting package is practically of the same size as the die. Wafer-level packaging allows integration of wafer fab, packaging, test, and burn-in at wafer level in order to streamline the manufacturing process undergone by a device from silicon start to customer shipment. There is no single industry-standard method of wafer-level packaging at present.
A major application area of WLPs are smartphones due to the size constraints. For example, the Apple iPhone 5 has at least eleven different WLPs, the Samsung Galaxy S3 has six WLPs and the HTC One X has seven. Functions provided WLPs in smartphones include sensors, power management, wireless, etc. In fact, it has recently been rumored that the iPhone 7 will use fan-out wafer-level packaging technology in order to achieve a thinner and lighter model.
Wafer-level chip scale packaging (WL-CSP) is the smallest package currently available on the market and is produced by OSAT (Outsourced Semiconductor Assembly and Test) companies, such as Advanced Semiconductor Engineering (ASE). A WL-CSP or WLCSP package is just a bare die with a redistribution layer (RDL, interposer or I/O pitch) to rearrange the pins or contacts on the die so that they can be big enough and have sufficient spacing so that they can be handled just like a ball grid array (BGA) package.
There are two kinds of wafer level packaging: fan-in and fan-out. Fan-in WLCSP packages have an interposer that is the same size as that of the die, where as fan-out WLCSP packages have an interposer that is larger than the die, similar to conventional BGA packages, the difference being that the interposer is built directly atop the die, instead of the die being attached to it and reflowed using the flip chip method. This is also true in fan-in WLSCP packages. In both cases, the die with its interposer may be covered in encapsulating material such as epoxy.
In February 2015, it was discovered that a WL-CSP chip in the Raspberry Pi 2 had issues with xenon flashes (or any other bright flashes of longwave light), inducing the photoelectric effect within the chip. Thus, careful consideration concerning exposure to extremely bright light will need to be given with wafer-level packaging.


Cell casting

Cell casting is a method used for creating poly(methyl methacrylate) (PMMA) sheets. Liquid monomer is poured between two flat sheets of toughened glass sealed with a rubber gasket and heated for polymerization. Because the glass sheets may contain surface scratches or sag during the process, this traditional method has some disadvantages: among other problems, the PMMA sheets may contain variations in thickness and surface defects. For many applications it has since been replaced by other methods for making PMMA such as extrusion, which gives uniform surface features. However, for applications where strength is critical cell casting techniques are still employed in conjunction with stretching, which produces a stronger overall material.
"Cell Casting - A process in which a casting liquid is poured between two plates, usually glass, that have a gasket between them to form a cell to contain the casting liquid; then the resin solidifies, usually through polymerization or crosslinking." - A. Brent Strong


Semi-solid metal casting

Semi-solid metal casting (SSM) is a near net shape variant of die casting. The process is used today with non-ferrous metals, such as aluminium, copper, and magnesium, but also can work with higher temperature alloys for which no currently suitable die materials are available. The process combines the advantages of casting and forging. The process is named after the fluid property thixotropy, which is the phenomenon that allows this process to work. Simply, thixotropic fluids flow when sheared, but thicken when standing. The potential for this type of process was first recognized in the early 1970s. There are three different processes: "thixocasting", "rheocasting", "thixomolding". "SIMA" refers to a specialized process to prepare aluminum alloys for thixocasting using hot and cold working .
SSM is done at a temperature that puts the metal between its liquidus and solidus temperature. Ideally, the metal should be 30 to 65% solid. The semi-solid mixture must have a low viscosity to be usable, and to reach this low viscosity the material needs a globular primary surrounded by the liquid phase. The temperature range possible depends on the material and for aluminum alloys can be as much as 50 °C, but for narrow melting range copper alloys can be only several tenths of a degree.
Semi-solid casting is typically used for high-end applications. For aluminum alloys, typical parts include structural medical and aerospace parts, pressure containing parts, defense parts, engine mounts, air manifold sensor harnesses, engine blocks, and oil pump filter housings.
Processes.
There are a number of different techniques to produce semi-solid castings. For aluminum alloys the more common processes are "thixocasting" and "rheocasting".
With magnesium alloys, the most common process is "molding".
Thixocasting.
Thixocasting utilizes a pre-cast billet with a non-dendritic microstructure that is normally produced by vigorously stirring the melt as the bar is being cast. Induction heating is normally used to re-heat the billets to the semi-solid temperature range, and die casting machines are used to inject the semi-solid material into hardened steel dies. Thixocasting is being performed commercially in North America, Europe and Asia. Thixocasting has the ability to produce extremely high quality components due to the product consistency that results from using pre-cast billet that is manufactured under the same ideal continuous processing conditions that are employed to make forging or rolling stock. The main disadvantage is that it is expensive due to the special billets that must be used, although facilities with in house magnetohydrodynamic continuous casting capabilities can recycle 100% of in-house returns. Other disadvantages include a limited number of alloys, and for facilities without in-house magnetohydrodynamic casting capability scrap cannot be directly reused.
Rheocasting.
Unlike thixocasting, which re-heats a billet, rheocasting develops the semi-solid slurry from the molten metal produced in a typical die casting furnace. This is a big advantage over thixocasting because it results in less expensive feedstock, in the form of typical die casting alloys, and allows for direct recycling. However, rheocasting also poses process control issues such that after an initial surge of activity, very little material is processed via rheocasting.
Thixomolding.
For magnesium alloys, thixomolding uses a machine similar to injection molding. In a single step process, room temperature magnesium alloy chips are fed into the back end of a heated barrel through a volumetric feeder. The barrel is maintained under an argon atmosphere to prevent oxidation of the magnesium chips. A screw conveyor located inside the barrel feeds the magnesium chips forward as they are heated into the semi-solid temperature range. The screw rotation provides the necessary shearing force to generate the globular structure needed for semi-solid casting. Once enough slurry has accumulated, the screw moves forward to inject the slurry into a steel die.
Strain-induced melt-activated (SIMA).
In the SIMA method the material is first heated to the SMM temperature. As it nears the solidus temperature the grains recrystallize to form a fine grain structure. After the solidus temperature is passed the grain boundaries melt to form the SSM microstructure. For this method to work the material should be extruded or cold rolled in the half-hard tempered state. This method is limited in size to bar diameters smaller than ; because of this only smaller parts can be cast.
Advantages.
The advantages of semi-solid casting are as follows:
High consolidation pressures are used to produce high integrity parts, and temperatures required to die-cast semi-solid metal are lower than normal casting; conventional tool steel materials are typically used in production applications. The lack of suitable high temperature die materials limits the casting of high melting point metals, such as tool steel and stellite, only to experimental applications. Other advantages include ease of automation, consistency, production rates equal to or better than die casting rates, no air entrapment, low shrinkage rates, and uniform microstructure.
Disadvantages.
Production facilities do require a higher degree of control over process conditions, but standard die casting machines are very suitable for production albeit with higher final injection pressures and lower injection velocities.
While selling thixocast scrap can be costly, facilities with on-site magneto-hydrodynamic continuous casting capabilities are able to completely recycle all in-house material returns.
Because thixotropy (semi-solid state) is a middle state in physical or rheological sense, this process is relatively insensitive to ambient temperature since small heat losses cause only minor changes in fraction solid.


Saab Aeronáutica Montagens

Saab Aeronáutica Montagens SA is a Brazilian aeronautical company which has operated since 2018 as a subsidiary company of the Sweden aerospace conglomerate Saab AB. The Brazilian aerospace engineering company, Akaer Engenharia SA, has a shareholding in this company.
Saab Aeronáutica Montagens is producing empennage, air brakes, the wingbox, the rear fuselage, and the forward fuselage for their mainline product: Saab JAS 39 Gripen. The manufacturer hopes that in the future this assembly line will be used to manufacture these parts for aircraft that may be sold to other countries.


Confirmed line item performance

The Confirmed Line Item Performance (CLIP) is one of the diagnostic metrics for perfect order fulfillment which defines the supply chain delivery reliability measurement between facilities within a supply chain.
Those facilities may belong to one company or span over several companies. CLIP is an analog measurement taking the portion of fulfillment into account using customer commit date as reference date. This intends a usage within a supply chain part with a fixed-period demand pattern (e.g. daily or weekly) and a permanent material flow (e.g. between production and distribution center), which is later on again split to be sent to different customers and locations.
Definition.
CLIP shows the relation between the sum of the deliveries and excess deliveries compared to the sum of orders and actual backlog by part number for the considered period of time. In aggregation of all part numbers (identifier for production control, calculation, shipment and other purposes products), it shows the status of order fulfillment. Excess delivery (pre- plus over-delivery) for one product (specified by its part number) does not compensate for the backlog of another product.
The definitions for backlog, pre-delivery, over-delivery and excess delivery for a single product are as follows:
To determine the confirmed line item performance two "virtual" quantities are introduced: the virtually committed order and the virtual delivery. The virtually committed order for a product p consists of the actual order for the considered delivery week (DW) plus any backlog of this product accumulated up to that week.
The virtual delivery for a product consists of the actually delivered chips within the considered delivery week plus any excess deliveries of this product accumulated up to that week.
The confirmed line item performance of one product p for a delivery week is calculated as the ratio of the virtual delivery to the virtually committed order. If there are more chips delivered than ordered, the CLIP of the respective product is 100%.
The CLIP of the whole site is calculated as the average CLIP of all products with a virtually committed order. Each product is counted separately (by part number). There is no weighting by volume applied.
Aggregation.
CLIP is being measured for every part number. The CLIP value of a certain “bundle“ (location, PL, Segment etc.) of part numbers is calculated by averaging the CLIP values of the individual part number in that “bundle“. Each part number in an aggregation (“bundle”) is counted as 1, irrespective of how big the volume of production for that part number is.
The lateness compared to the confirmed date is taken into account. In every period p the backlog of previous periods is not fulfilled the CLIP performance is worsened signaling the receiver an open demand.


Ultrasonic consolidation

Ultrasonic Consolidation (UC) or Ultrasonic Additive Manufacturing (UAM) is a low temperature additive manufacturing or 3D printing technique for metals.
The process works by scrubbing metal foils together with ultrasonic vibrations under pressure in a continuous fashion, i.e., sheet lamination classification in additive manufacturing. Melting is not the formation mechanism. Instead, metals are joined in the solid-state via disruption of surface oxide films between the metals, i.e. ultrasonic metal welding mechanisms. CNC contour milling is used interchangeably with the additive stage of the process to introduce internal features and add detail to the metal part. UAM has the ability to join multiple metal types together, i.e., dissimilar metal joining, with no or minimal intermetallic formation and allows the embedment of temperature sensitive materials at relatively low temperature—typically less than 50% of the metal matrix melting temperature.
History.
The Ultrasonic Consolidation or Ultrasonic Additive Manufacturing process was invented and patented by Dawn White. In 1999, White founded Solidica Inc. to sell commercial UAM equipment—Form-ation machine suite. Near 2007, the Edison Welding Institute (EWI) and Solidica began a collaboration to re-design the weld tooling to remedy bond quality limitations and to expand the weldable metals of the process—so called very high power UAM. In 2011, Fabrisonic LLC was formed to commercialize the improved UAM process—SonicLayer machine suite. A SonicLayer 4000 system was simultaneously deployed at the Ohio State University.
Process.
As with most other additive manufacturing processes UC creates objects directly from a CAD model of the required object. The file is then "sliced" into layers which results in the production of a .STL file that can be used by the UC machine to build the required object, layer by layer.
The general manufacturing process is:
Mechanism of the metallurgical bond formation between foils can be explained by microscopic deformation of micro-asperities on the top foil. The sonotrode surface is usually textured so as to facilitate the grip of the top foil subjected to vibrations. The resultant rough imprint on the top foil surface affects bonding of the subsequent layer. The contact area between the upper and lower foils expands when the micro-asperities are crushed by the ultrasonic oscillations.


Motor-CAD

Motor-CAD is an Electromagnetic and Thermal analysis package for electric motors and generators, developed and sold by Motor Design Ltd. It was initially released in 1999.
Modules are available for brushless permanent magnet motors (BPM), outer rotor BPM motors, induction motors, permanent magnet dc machines, switched reluctance motors, synchronous machines and claw pole machines.
An integrated ultra fast finite element module (EMag) provides accurate electromagnetic and electrical performance predictions.
The thermal module (Therm) combines lumped circuit and finite element thermal calculations for optimising the cooling system of the machine.
Cooling methods modelled include natural convection (Totally enclosed non ventilated - TENV), forced convection (Totally enclosed fan cooled - TEFC), through ventilation, water jackets, submersible, wet rotor and wet stator, spray cooling, radiation and conduction.
A wide range of housing types can be modelled.
The Lab module works with the EMag and Therm modules to help develop new design concepts. It provides efficiency mapping and duty cycle / drive cycle transient outputs within a few minutes.
Thermal analysis of electric machines is regarded as a more challenging area of analysis than electromagnetic analysis in the construction of the model and the accuracy achievable.
Thermal analysis of electrical machines is becoming ever more important due to the increasing drive for energy efficiency and compact design machines. This is particularly true for the aerospace and automotive sectors where size, weight and efficiency are driving the design of machines.
The design approach often taken is to consider both electromagnetic and thermal aspects of a machines design at the early stages in machine design, where Motor-CAD allows this to be done.
Other possible thermal modelling techniques include computational fluid dynamics. Motor-CAD has been shown to give results with a similar accuracy in a fraction of the time.


FSI International

FSI International, Inc. (FSI) is an American manufacturing company based in Chaska, Minnesota, that supplies processing equipment used to manufacture microelectronics, including semiconductor devices.
History.
The company's history began with the establishment of Fluoroware, Inc. in 1966, a company that made fixtures to hold the silicon wafers in place during the various processes involved in producing semiconductor devices. When asked to design a drying apparatus, the principals of Fluoroware agreed to do so and established FSI International in 1973 to market this new product.
The company's offerings expanded to meet the market need for equipment used in the fabrication of microelectronics. In the 1990s, the company relocated from its original facility overlooking Hazeltine Lake to a larger site nearby.
In 1999, FSI International announced an agreement to acquire YieldUP International Corp. In October 2012, Tokyo Electron acquired FSI International, Inc. and renamed the division TEL FSI.
Products.
FSI International supplied surface conditioning technology solutions, using wet, cryogenic and other chemistry techniques to clean, strip or etch the surfaces of silicon wafers. The company also engaged in microlithography systems for photoresist, light-sensitive, and etch-resistant films. The company provides upgrade, replacement and other support services.
The five main series of equipment produced by the company are: ZETA, MERCURY, ORION, ANTARES, and POLARIS, and in earlier years, the company also produced the SATURN and NEPTUNE processing systems. Some of the products of the company are spray cleaning systems, single wafer cleaning systems, cryogenic processing systems, and immersion cleaning systems.


Vericut

Vericut (publicly capitalized VERICUT), is a software program used for simulating CNC machining. It is used to simulate tool motion and the material removal process, detecting errors or areas of inefficiency in NC programs. It was developed by CGTech Inc. and first released in 1988.
History.
Vericut was designed by CGTech Inc. in 1988. The software was first developed to run in Unix workstations and was later ported to Windows. Since its initial launch, Vericut has been installed and is used by Fortune 500 and other notable companies including Boeing, Airbus, General Motors, and Israel Aircraft Industries As of 2009, Vericut has been used by more than 2000 companies worldwide. In 2011, CGTech was ranked as the largest independent NC verification and simulation software provider based on revenue, with over 9,000 installed seats.
Features.
Vericut is standalone software but also integrates with CAD, CAM, and PLM systems including CATIA, Siemens NX, PowerMILL, EdgeCAM, Mastercam and Hypermill. It uses a three-axis through five-axis simulation motion to simulate milling and drilling operations. The simulation is displayed on a graphics screen as a solid 3D model of the raw stock, simulating the programmed cutting motions and then displaying the finished part.
Machine tool simulation.
Vericut software is customizable and includes a selection of machine tools. Machine models can also be built from scratch, using a CAD system or by defining such in the software. It contains a component tree to manage the kinematics of a machine. Vericut simulates machine tools in their entirety as they would appear in a shop and shows the removal of material at the workpiece level. It also simulates NC machine controls and automatically checks for collisions and over travel of machine tools to reduce the probability of a machine crash.
The machine simulation feature detects all machine components for near-misses and collisions. Near miss zones can be set up by users around components to check for close calls and over-travel errors. Machine movements are simulated in review mode while stepping or playing backwards.
NC program optimization.
Vericut has NC program optimizing capabilities. It automatically determines the safe feed rate for each cut based on programmed feed rates, reducing cycling time. The optimization is said to reduce the amount of scrapped parts, broken tools, and cutter deflection.


TO-126

TO-126 is a type of semiconductor package for devices with three pins, such as transistors. The package is rectangular with a hole in the middle to allow for easy mounting to a board or a heat sink. On one side of the package typically a metal sheet is exposed, with the transistor die bonded to the other side of the metal sheet inside the package. This allows for an efficient heat transfer from the transistor die to an external heat sink but also implies that the metal sheet is electrically connected to the die (for a bipolar junction transistor usually the collector is connected to this metal sheet).
History and origin.
The JEDEC TO-126 descriptor is derived from the original full name for the package: Transistor Outline Package, Case Style 126. In the updated JEDEC outline system, the package is numbered as TO-225AA.
STMicroelectronics refers to this package style as SOT-32.


Reflow soldering

Reflow soldering is a process in which a solder paste (a sticky mixture of powdered solder and flux) is used to temporarily attach one or thousands of tiny electrical components to their contact pads, after which the entire assembly is subjected to controlled heat. The solder paste reflows in a molten state, creating permanent solder joints. Heating may be accomplished by passing the assembly through a reflow oven, under an infrared lamp, or (unconventionally) by soldering individual joints with a desoldering hot air pencil.
Reflow soldering with long industrial convection ovens is the preferred method of soldering surface mount technology components or SMT to a printed circuit board or PCB. Each segment of the oven has a regulated temperature, according to the specific thermal requirements of each assembly. Reflow ovens meant specifically for the soldering of surface mount components may also be used for through-hole components by filling the holes with solder paste and inserting the component leads through the paste. Wave soldering however, has been the common method of soldering multi-leaded through-hole components onto a circuit board designed for surface-mount components.
When used on boards containing a mix of SMT and plated through-hole (PTH) components, through-hole reflow, when achievable by specifically modified paste stencils, may allow for the wave soldering step to be eliminated from the assembly process, potentially reducing assembly costs. While this may be said of lead-tin solder pastes used previously, lead-free solder alloys such as SAC present a challenge in terms of the limits of oven temperature profile adjustment and requirements of specialized through-hole components that must be hand soldered with solder wire or cannot reasonably withstand the high temperatures directed at circuit boards as they travel on the conveyor of the reflow oven. The reflow soldering of through-hole components using solder paste in a convection oven process is called intrusive soldering.
The goal of the reflow process is for the solder paste to reach the eutectic temperature at which the particular solder alloy undergoes a phase change to a liquid or molten state. At this specific temperature range, the molten alloy demonstrates properties of adhesion. Molten solder alloy behaves much as water, with properties of cohesion and adhesion. With sufficient flux, in the state of liquidus, molten solder alloys will exhibit a characteristic called "wetting."
Wetting is a property of the alloy when within its specific eutectic temperature range. Wetting is a necessary condition for the formation of solder joints that meet the criteria as "acceptable" or "target" conditions, while "non-conforming" is considered defective according to IPC.
The reflow oven temperature profile is suited for characteristics of a particular circuit board assembly, the size and depth of the ground plane layer within the board, the number of layers within the board, the number and size of the components, for example. The temperature profile for a particular circuit board will allow for reflow of solder onto the adjoining surfaces, without overheating and damaging the electrical components beyond their temperature tolerance. In the conventional reflow soldering process, there are usually four stages, called "zones", each having a distinct thermal profile: "preheat", "thermal soak" (often shortened to just "soak"), "reflow", and "cooling".
Preheat zone.
Preheat is the first stage of the reflow process. During this reflow phase, the entire board assembly climbs towards a target soak or dwell temperature. The main goal of the preheat phase is to get the entire assembly safely and consistently to a soak or pre-reflow temperature. Preheat is also an opportunity for volatile solvents in the solder paste to outgas. For paste solvents to be properly expelled and the assembly to safely reach pre-reflow temperatures the PCB must be heated in a consistent, linear manner. An important metric for the first phase of the reflow process is the temperature slope rate or rise vs time. This is often measured in degrees Celsius per second, °C/s. Many variables factor into a manufacturer's target slope rate. These include: target processing time, solder paste volatility, and component considerations. It is important to account for all these process variables, but in most cases sensitive component considerations are paramount.
“Many components will crack if their temperature is changed too quickly. The maximum rate of thermal change that the most sensitive components can withstand becomes the maximum allowable slope”. However, if thermally sensitive components are not in use and maximizing throughput is of great concern, aggressive slope rates may be tailored to improve processing time. For this reason, many manufacturers push these slope rates up to the maximum common allowable rate of 3.0 °C/s. Conversely, if a solder paste containing particularly strong solvents is being used, heating the assembly too fast can easily create an out of control process. As the volatile solvents outgas they may splatter solder off the pads and onto the board. Solder-balling is the main concern of violent outgassing during the preheat phase. Once a board has been ramped up to temperature in the preheat phase it is time to enter the soak or pre-reflow phase.
Thermal soak zone.
The second section, thermal soak, is typically a 60 to 120 second exposure for removal of solder paste volatiles and activation of the fluxes, where the flux components begin oxide reduction on component leads and pads. Too high a temperature can lead to solder spattering or balling as well as oxidation of the paste, the attachment pads and the component terminations. Similarly, fluxes may not fully activate if the temperature is too low. At the end of the soak zone a thermal equilibrium of the entire assembly is desired just before the reflow zone. A soak profile is suggested to decrease any delta T between components of varying sizes or if the PCB assembly is very large. A soak profile is also recommended to diminish voiding in area array type packages.
Reflow zone.
The third section, the reflow zone, is also referred to as the “time above reflow” or “temperature above liquidus” (TAL), and is the part of the process where the maximum temperature is reached. An important consideration is peak temperature, which is the maximum allowable temperature of the entire process. A common peak temperature is 20–40 °C above liquidus. This limit is determined by the component on the assembly with the lowest tolerance for high temperatures (the component most susceptible to thermal damage). A standard guideline is to subtract 5 °C from the maximum temperature that the most vulnerable component can sustain to arrive at the maximum temperature for process. It is important to monitor the process temperature to keep it from exceeding this limit. Additionally, high temperatures (beyond 260 °C) may cause damage to the internal dies of SMT components as well as foster intermetallic growth. Conversely, a temperature that isn’t hot enough may prevent the paste from reflowing adequately.
Time above liquidus (TAL), or time above reflow, measures how long the solder is a liquid. The flux reduces surface tension at the juncture of the metals to accomplish metallurgical bonding, allowing the individual solder powder spheres to combine. If the profile time exceeds the manufacturer’s specification, the result may be premature flux activation or consumption, effectively “drying” the paste before formation of the solder joint. An insufficient time/temperature relationship causes a decrease in the flux’s cleaning action, resulting in poor wetting, inadequate removal of the solvent and flux, and possibly defective solder joints. Experts usually recommend the shortest TAL possible, however, most pastes specify a minimum TAL of 30 seconds, although there appears to be no clear reason for that specific time. One possibility is that there are places on the PCB that are not measured during profiling, and therefore, setting the minimum allowable time to 30 seconds reduces the chances of an unmeasured area not reflowing. A high minimum reflow time also provides a margin of safety against oven temperature changes. The wetting time ideally stays below 60 seconds above liquidus. Additional time above liquidus may cause excessive intermetallic growth, which can lead to joint brittleness. The board and components may also be damaged at extended temperature over liquidus, and most components have a well-defined time limit for how long they may be exposed to temperatures over a given maximum. Too little time above liquidus may trap solvents and flux and create the potential for cold or dull joints as well as solder voids.
Cooling zone.
The last zone is a cooling zone to gradually cool the processed board and solidify the solder joints. Proper cooling inhibits excess intermetallic formation or thermal shock to the components. Typical temperatures in the cooling zone range from 30–110 °C (86–212 °F). A fast cooling rate is chosen to create a fine grain structure that is most mechanically sound. Unlike the maximum ramp-up rate, the ramp–down rate is often ignored. The ramp rate is less critical above certain temperatures, however, the maximum allowable slope for any component should apply whether the component is heating up or cooling down. A cooling rate of 4 °C/s is commonly suggested. It is a parameter to consider when analyzing process results.
Etymology.
The term "reflow" is used to refer to the temperature above which a solid mass of solder alloy is certain to melt (as opposed to merely soften). If cooled below this temperature, the solder will not flow. Warmed above it once more, the solder will flow again—hence "re-flow".
Modern circuit assembly techniques that use reflow soldering do not necessarily allow the solder to flow more than once. They guarantee that the granulated solder contained in the solder paste surpasses the reflow temperature of the solder involved.
Thermal profiling.
Thermal profiling is the act of measuring several points on a circuit board to determine the thermal excursion it takes through the soldering process.
In the electronics manufacturing industry, SPC (Statistical Process Control) helps determine if the process is in control, measured against the reflow parameters defined by the soldering technologies and component requirements.
Modern software tools allow a profile to be captured, then automatically optimized using a mathematical simulation, which greatly reduces the time needed to establish optimal settings for the process.
References.
http://www.idc-online.com/technical_references/pdfs/electronic_engineering/Electronics_Manufacture_Intrusive_Reflow.pdf


Results of the 1990 Ontario general election by riding

The following are the results by riding (electoral district) of the 1990 Ontario general election, that was held on September 6, 1990.
Constituency results.
Ottawa-Carleton.
Total votes: 38,074
Total votes: 35,376
Total votes: 32,328
Total votes: 30,446
Ottawa East
Total votes: 26,218
Total votes: 29,695
Total votes: 30,185
Total votes: 33,422
Eastern Ontario.
Total votes: 27 347
Total votes: 29,174
Total votes: 28 282
Ronald Gerow (CoR) 1128 (4.0%)
Total votes: 26 807
Total votes: 34 330
Total votes: 39 833
Total votes: 27 752
Total votes: 29 691
Total votes: 30 198
Total votes: 29 082
Central Ontario.
Total votes: 30,429
Total votes: 31,447
Total votes: 38,056
Total votes: 33 031
Total votes: 35 740
Total votes: 41,888
Total votes: 41 572
Total votes: 37 398
Total votes: 32 089
Total votes: 34 889
Durham & York Region.
Total votes: 35,096
Total votes: 33 476
Total votes: 43,678
Total votes: 36 284
Total votes: 51 221
Total votes: 27 173
Total votes: 61 562
Total votes: 33,437
Scarborough.
Total votes: 30 118
Total votes: 27,262
Total votes: 32 915
Total votes: 29 119
Total votes: 30 056
Total votes: 28 027
North York & East York.
Total votes: 28,483
Total votes: 23 755
Total votes: 26 364
Total votes: 25 454
Total votes: 33,947
Total votes: 27,725
Total votes: 29 848
Total votes: 29 207
Total votes: 20 059
Toronto.
Total votes: 24 645
Total votes: 19 548
Total votes: 33 451
Total votes: 23 806
Total votes: 25 337
Total votes: 17 417
Total votes: 22 729
Total votes: 29 956
Total votes: 29 706
Etobicoke & York.
Total votes: 35 178
Total votes: 31 660
Total votes: 26 270
Total votes: 33 810
Total votes: 21 384
Total votes: 24 949
Brampton, Mississauga & Halton.
Total votes: 33,462
Total votes: 39 985
Total votes: 32 520
Total votes: 38 523
Total votes: 27,503
Total votes: 31 684
Total votes: 33 442
Total votes: 32 652
Total votes: 47 584
Total votes: 31,304
Hamilton-Wentworth & Niagara.
Total votes: 25 358
Total votes: 28 336
Total votes: 37 629
Total votes: 32 777
Total votes: 34,141
Total votes: 29 939
Total votes: 23 972
Total votes: 29 835
Total votes: 27,478
Total votes: 32 202
Total votes: 34 111
Total votes: 33 692
Midwestern Ontario.
Total votes: 36 474
Total votes: 28 785
Total votes: 36 176
Total votes: 39 701
Total votes: 29 070
Total votes: 33 640
Total votes: 36 537
Total votes: 36 195
Total votes: 36 504
Total votes: 31 802
Total votes: 38 883
Total votes: 30 646
Southwestern Ontario.
Total votes: 31,138
Total votes: 34 047
Total votes: 30 116
Total votes: 29 358
Total votes: 27,675
Total votes: 34 765
Total votes: 43 770
Total votes: 41 115
Total votes: 38 382
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Northeastern Ontario.
Total votes: 14 017
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Total votes: 16 955
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Total votes: 38 713
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Northwestern Ontario.
Total votes: 26,551
Total votes: 20 106
Total votes: 12,785
Total votes: 27 798
Total votes: 12 751


Cold foil printing

Cold foil printing, also known as cold foil stamping, is a modern method of printing metallic foil on a substrate in order to enhance the aesthetic of the final product. Cold foil printing can be done two ways: the older dry lamination process common in the offset printing industry, or the newer, more versatile wet lamination process, which is dominant in the flexo label industry.
How it works.
Cold foil dry lamination.
Using a standard printing plate, an image is printed onto a substrate with the use of an ultraviolet-curable cold foil adhesive. An ultraviolet dryer then cures the adhesive, which becomes tacky. Foil spools from an unwind and is nipped to a substrate. Foil sticks to the tacky adhesive on the substrate, and an image with a bright foil surface is created. Foil that does not adhere to the adhesive remains on a thin polyester liner, and waste is directed to a rewind spool. Because the adhesive is applied on press like a conventional ink, no expensive stamping die has to be created.
Once printed, the surface of cold foil images may be varnished, laminated, or encapsulated in order to provide a hard-wearing, durable surface.
Substrates.
Some printing substrates are unsuitable for cold foil transfer. The best results are obtained on glossy coated papers and papers with a smooth surface. Weights from about 80 to 500 g/m^2 are possible.
Benefits.
The process does not require stamping tools, but instead uses printing plates, which are cheaper and can be made in a few hours. In contrast, delivery time for an engraved or etched stamping tool can be up to two weeks. More importantly for the designer, gradients and halftone images can be introduced.
History.
Hot foil stamping.
Cold foil evolved from hot foil stamping. Hot foil stamping is mostly used offline when foil is required on a preprinted substrate, such as in the manufacture of greeting cards and special occasion ribbons. Hot foil is economical but very slow. The types of graphics that can be applied are usually limited to text and bold images. Hot foil is not usable with heat-sensitive substrates such as polyethylene, vinyl, or shrink film.
Cold foil evolution.
Cold foil takes the idea of hot foil stamping and makes it more convenient and cost-effective. The cold foil functions like an additional ink and is actually a UV-curable, very fast lamination adhesive and can be bonded in-line in a single run using a printing plate for either flexographic web printing or offset sheet-fed printing. It can be applied precisely with high resolution, even for fine structures such as raster gradients and thin lines. Typeface is legible from about 5 points upwards and has excellent edge definition. Cold foil printing needs smooth surface substrates for excellent image quality.
Cold foil indexing.
As the cold foil market evolves, major players in the printing industry are finding ways to make the process even more cost-effective. By indexing cold foil, printers can reduce foil waste, reduce their presses' downtime, and in turn maximize their presses' efficiency.
Uses.
Cold foil is most commonly used on products that call for a strong "shelf appeal", such as household consumables, cigarette cartons, wine labels, and cosmetic packaging. It provides a luxurious metallic look on higher added-value label applications.


Assemble-to-order system

In applied probability, an assemble-to-order system is a model of a warehouse operating a build to order policy where products are assembled from components only once an order has been made.
The time to assemble a product from components is negligible, but the time to create components is significant (for example, they must be ordered from a supplier).
Research typically focuses on finding good policies for inventory levels and on the impact of different configurations (such as having more shared parts). The special case of only one product is an assembly system, the case of just once component is a distribution system.
Model definition.
Single period model.
This case is a generalisation of the newsvendor model (which has only one component and one product). The problem involves three stages and we give one formation of the problem below
We use the following notation
In the final stage when demands are known the optimization problem faced is to
and we can therefore write the optimization problem at the first stage as
with x0 representing the starting inventory vector and "c" the cost function for acquiring the components.
Continuous time.
In continuous time orders for products arrive according to a Poisson process and the time required to produce components are independent and identically distributed for each component. Two problems typically studied in this system are to minimize the expected backlog of orders subject to a constraint on the component inventory, and to minimize the expected component inventory subject to constraints on the rate at which orders must be completed.


Welding joint

In metalworking, a welding joint is a point or edge where two or more pieces of metal or plastic are joined together. They are formed by welding two or more workpieces according to a particular geometry. There are five types of joints referred to by the American Welding Society: butt, corner, edge, lap, and tee. These configurations may have various configurations at the joint where actual welding can occur.
Butt welds.
Butt welds are welds where two pieces of metal to be joined are in the same plane. These welds require only some preparation and are used with thin sheet metals that can be welded with a single pass. Common issues that can weaken a butt weld are the entrapment of slag, excessive porosity, or cracking. For strong welds, the goal is to use the least amount of welding material possible.
Butt welds are prevalent in automated welding processes, such as submerged-arc welding, due to their relative ease of preparation. When metals are welded without human guidance, there is no operator to adjust non-ideal joint preparation. Because of this necessity, butt welds can be utilized for their simplistic design to be fed through automated welding machines efficiently.
Types.
There are many types of butt welds, but all fall within one of these categories: single-welded butt joints, double-welded butt joint, and open or closed butt joints. A single welded butt joint is the name for a joint that has only been welded from one side. A double-welded butt joint is created when the weld has been welded from both sides. With double welding, the depths of each weld can vary slightly. A closed weld is a type of joint in which the two pieces that will be joined are touching during the welding process. An open weld is the joint type where the two pieces have a small gap in between them during the welding process.
Square butt joints.
The square groove is a butt welding joint with the two pieces being flat and parallel to each other. This joint is simple to prepare, economical to use, and provides satisfactory strength but is limited by joint thickness. The closed square butt weld is a type of square-groove joint with no spacing in between the pieces. This joint type is common with gas and arc welding.
For thicker joints, the edge of each member of the joint must be prepared to a particular geometry to provide accessibility for welding and to ensure the desired weld soundness and strength. The opening or gap at the root of the joint and the included angle of the groove should be selected to require the least weld metal necessary to give needed access and meet strength requirements. Only metal up to 4.5mm thick is usually used for square butt joints.
V-joints.
Single V welds are similar to a bevel joint, but instead of only one side having the bevelled edge, both sides of the weld joint are beveled. In thick metals, and when welding can be performed from both sides of the work piece, a double-V joint is used. When welding thicker metals, a double-V joint requires less filler material because there are two narrower V-joints compared to a wider single-V joint. Also the double-V joint helps compensate for warping forces. With a single-V joint, stress tends to warp the piece in one direction when the V-joint is filled, but with a double-V-joint, there are welds on both sides of the material, having opposing stresses, straightening the material.
J-joints.
Single-J butt welds are when one piece of the weld is shaped like a "J" that easily accepts filler material and the other piece is square. A J-groove is formed either with special cutting machinery or by grinding the joint edge into the form of a J. Although a J-groove is more difficult and costly to prepare than a V-groove, a single J-groove on metal between a half an inch and three-quarters of an inch thick provides a stronger weld that requires less filler material. Double-J butt welds have one piece that has a "J" shape from both directions and the other piece is square.
U-joints.
Single-U butt welds are welds that have both edges of the weld surface shaped like a J, but once they come together, they form a U. Double-U joints have a U formation on both the top and bottom of the prepared joint. U-joints are the most expensive edge to prepare and weld. They are usually used on thick base metals where a V-groove would be at such an extreme angle that it would cost too much to fill.
Tee-Joints.
The Tee Weld Joint is formed when two bars or sheets are joined perpendicular to each other in the form of a "T" shape. This weld is made from the resistance butt welding process. It can also be performed by Extrusion Welding. Usually two flat pieces of poly are welded at 90 degrees to each other, and extrusion welded on both sides.
Others.
Thin sheet metals are often flanged to produce edge-flange or corner-flange welds. These welds are typically made without the addition of filler metal because the flange melts and provides all the filler needed. Pipes and tubing can be made from rolling and welding together strips, sheets, or plates of material.
Flare-groove joints are used for welding metals that, because of their shape, form a convenient groove for welding, such as a pipe against a flat surface.
Selection of the right weld joint depends on the thickness and process used. The square welds are the most economical for pieces thinner than 3/8”, because they don’t require the edge to be prepared. Double-groove welds are the most economical for thicker pieces because they require less weld material and time. The use of fusion welding is common for closed single-bevel, closed single J, open single J, and closed double J butt joints. The use of gas and arc welding is ideal for double-bevel, closed double-bevel, open double-bevel, single-bevel, and open single-bevel butt welds.
Below are listed ideal joint thicknesses for the various types of butt. When the thickness of a butt weld is defined it is measured at the thinner part and does not compensate for the weld reinforcement.
Cruciform.
A "" is a specific joint in which four spaces are created by the welding of three plates of metal at right angles. Cruciform joints suffer fatigue when subjected to continuously varying loads.
In the American Bureau of Shipping Rules for Steel Vessels, cruciform joints may be considered a double barrier if the two substances requiring a double barrier are in opposite corners diagonally. Double barriers are often required to separate oil and seawater, chemicals and potable water, etc.
Plate edge preparation.
In common welding practices, the welding surface must be prepared to ensure the strongest weld possible. Preparation is needed for all forms of welding and all types of joints. Generally, butt welds require very little preparation, but some is still needed for the best results. Plate edges can be prepared for butt joints in various ways, but the five most common techniques are oxyacetylene cutting (oxy-fuel welding and cutting), machining, chipping, grinding, and air carbon-arc cutting or gouging. Each technique has unique advantages to their use.
For steel materials, oxyacetylene cutting is the most common form of preparation. This technique is advantageous because of its speed, low cost, and adaptability. Machining is the most effective for reproducibility and mass production of parts. The preparation of J or U joints is commonly prepared by machining due to the need for high accuracy. The chipping method is used to prepare parts that were produced by casting. The use of grinding to prepare pieces is reserved for small sections that cannot be prepared by other methods. Air carbon arc cutting is common in industries that work with stainless steels, cast iron, or ordinary carbon steel.
Prior to welding dissimilar materials, one or both faces of the groove can be buttered. The buttered layer can be the same alloy as the filler metal or a different filler metal that will act as a buffer between the two metals to be joined.


Manufacturing readiness level

The manufacturing readiness level (MRL) is a measure to assess the maturity of manufacturing readiness, similar to how technology readiness levels (TRL) are used for technology readiness. They can be used in general industry assessments, or for more specific application in assessing capabilities of possible suppliers.
The Government Accountability Office (GAO) has described it as best practice for improving acquisition outcomes. It was developed by the United States Department of Defense (DOD), who adopted the usage of MRLs in 2005. However, GAO continued to note inconsistent application across DOD components. In 2011, consideration of manufacturing readiness and related processes of potential contractors and subcontractors was made mandatory as part of the source selection process in major acquisition programs.
MRLs are quantitative measures used to assess the maturity of a given technology, component or system from a manufacturing perspective. They are used to provide decision makers at all levels with a common understanding of the relative maturity and attendant risks associated with manufacturing technologies, products, and processes being considered. Manufacturing risk identification and management must begin at the earliest stages of technology development, and continue vigorously throughout each stage of a program’s life-cycles.
Manufacturing readiness level definitions were developed by a joint DOD/industry working group under the sponsorship of the Joint Defense Manufacturing Technology Panel (JDMTP). The intent was to create a measurement scale that would serve the same purpose for manufacturing readiness as Technology Readiness Levels serve for technology readiness – to provide a common metric and vocabulary for assessing and discussing manufacturing maturity, risk and readiness. MRLs were designed with a numbering system to be roughly congruent with comparable levels of TRLs for synergy and ease of understanding and use.
Why manufacturing readiness?
MRLs are assessed to:
Immature manufacturing processes may lead to the following problems:
Assessing technology readiness levels does leave some major transition questions unanswered:
Manufacturing readiness assessments (MRAs) address these unanswered questions in order to reduce manufacturing risk. However, it still does not address the question of whether the product is reliable or maintainable.
Definitions.
The following has been adopted by the DOD as appropriate in assessing manufacturing readiness levels:
Dimensions in Assessing Readiness.
MRLs are assessed in multiple dimensions (referred to as "threads" within DOD):
Examples.
Several traditional non-proprietary non-confidential examples are described below illustrating the use of MRL methodology in joining manufacturing.


Standard Sanitary Manufacturing Company

The original Standard Sanitary was formed when James West Arrott of James West Arrott Insurance company in Pittsburgh, Pennsylvania took over a bankrupt hooper company that could not pay their insurance premiums. Along with Francis Torrance (they were related as they married the Waddell sisters) they learned about the enamelization of porcelain in Europe and brought that technique to America by first making bathtubs and then toilets and sinks. It was in the late 1890’s that Standard Sanitary was combined with other plumbing manufacturers to form the Standard Sanitary Manufacturing Company.
The Standard Sanitary Manufacturing Company was an American manufacturer of bathroom fixtures. It was formed in 1875 by the merger of the Ahrens and Ott Manufacturing Company, the Standard Manufacturing Company, the Dawes and Myler Manufacturing Company, and 6 other plants which were consolidated to form the Standard Manufacturing Company, headquartered in Pittsburgh, with Theodore Ahrens (Jr.) as its first president. He held this position, and others, until 1934.
In 1929, the company merged with the American Radiator Company to form the American Radiator and Standard Sanitary Corporation.


CNC machine tool monitoring by AE sensors

A machine tool monitoring system is a flow of information and system processing in which the information selection, obtaining data, processing of information and decision making on the refined information are integrated. The aim of tool condition monitoring is to detect early the disturbances in the machining process and wear of machine tool components.
The condition of tool has been researched extensively in the past and have focused on detection of tool wear, tool breakage and the estimation of remaining tool life. It is very important for on-line identification of tool condition in machining process for enhanced productivity, better quality of parts and lower costs for unmanned, automated manufacturing systems.
Techniques of machine tool monitoring.
Machine tool monitoring can be done with or without additional sensors. Using additional sensors, monitoring can be done by measuring:
Sensor-less machine tool monitoring is done by measuring internal drive signals such as:
Combined measuring of multiple quantities is also possible.
Acoustic emission sensor.
Machine tool monitoring is explained with Acoustic Emission (AE) sensors. An AE sensor is commonly defined as the sound emitted as an elastic wave by a solid when it is deformed or struck, caused by the rapid release of localized stress energy. Therefore, it is an occurrence phenomenon which releases elastic energy into the material, which then propagates as an elastic wave. The detection frequency range of acoustic emission is from 1 kHz to 1 MHz.
Rapid stress-releasing events generate a spectrum of stress waves starting at 0 Hz and typically falling off at several MHz. AE can be related to an irreversible release of energy. It can also be generated from sources not involving material failure including friction, cavitation and impact. The three major applications of AE sensors phenomena are: a) Source location - determine the locations of occurrence of an event b) Material mechanical performance - evaluate and characterize materials/structures; and c Health monitoring – monitors the safety operation.
How an AE sensor monitors machine tool.
An AE sensor works on the principle of measuring the high-frequency energy signals produced during cutting process. It also measures the AE energy resulting from the fracture when a tool breaks. It is best suited to applications where the level of background AE signal is low compared to the sound of tool breakage. This makes the AE sensor ideal for breakage detection of small drills and taps. It is easy to install on both new and existing machines.
An AE sensor detects force proportional monitoring signals even in machining operations, which generate very small cutting forces. In combination with true power, it increases the reliability of breakage monitoring. It is used especially with solid carbide tools, or very small tools on large machines and multi spindles. Most of the sensors have to be attached to the machine tool surface. However, there are alternative methods of AE wave transmitting. A rotating, wireless AE sensor consists of a rotating sensor and a fixed receiver. An AE sensor can also receive the acoustic waves via a jet of cooling lubricant, which can be connected directly to the tool or workpiece.
The machine tool monitoring systems commonly use sensors for measuring cutting force components or quantities related to cutting force (power, torque, distance/displacement and strain). AE sensors are relatively easy to install in existing or new machines, and do not influence machine integrity and stiffness. All systems suppliers also use acoustic emission sensors, especially for monitoring small tools and for grinding.
All sensors used in machine tool monitoring systems are well adjusted to harsh machine tool environments. The difficulties in designing reliable machine tool monitoring can be related to the complexity of the machining process itself, which may have one or more of the following characteristics, apart from the changes of the machine tool itself.