Gashing

Gashing is a machining process used to rough out coarse pitched gears and sprockets. It is commonly used on worm wheels before hobbing, but also used on internal and external spur gears, bevel gears, helical gears, and gear racks. The process is performed on "gashers" or universal milling machines, especially in the case of worm wheels. After gashing the gear or sprocket is finished via hobbing, shaping, or shaving.
Equipment.
"Gashers" are large, heavy-duty machine tools. They have horizontal and vertical slideways, precise indexing, large diameter ballscrews, and spindle drive motors up to . They are usually controlled via computer numerical control (CNC) or a microprocessor. While they are usually used for rough cutting, they are also sometimes used for finishing. For example, gashers are used for the production of large roller-chain sprockets.
Process.
Gashing was first used to rough out worm wheels using a universal milling machine, but then dedicated gashers were built to rough out other types of gears. Because the processes is carried out on two different machines the process differs.
Universal milling machine.
The process uses a milling cutter with a cross-section that is slightly smaller than the final cross-section of the cut; it has the same diameter as the worm. The cutter is then angled to the "gashing angle". The gashing angle is calculated from the lead and pitch diameter of the worm; often tables are available with the gashing angles for common diameters and leads. The cutter is centered over the blank and then plunged into it to the proper depth. The cutter is finally withdrawn and the blank indexed to the next tooth space and cut. This is repeated until all of the tooth spaces have been cut.
Note that a standard endmill with rounded corners can be used instead if a special milling cutter is unavailable. The endmill should be the pitch diameter.
Note that is process cannot be used on a small worm wheel that mate with a multiple threaded worm.
Gasher.
The process is similar to that outlined for the universal milling machine except a gashing angle is not used. When gashing spur gears, racks, or bevel gears the cutter is plunged into the workpiece and then moved linearly in the proper direction. If a helical gear is being roughed out, then the table rotates and moves along the vertical axis to interpolate the helical path.
The two most common cutting tools are formed milling cutters and cutters with indexable carbide inserts. For very large gears a cutter might be replaced with two slitting cutters that cut triangular slugs from the blank.


Continuous-flow manufacturing

Continuous-flow manufacturing, or repetitive-flow manufacturing, is an approach to discrete manufacturing that contrasts with batch production. It is associated with a just-in-time and kanban production approach, and calls for an ongoing examination and improvement efforts which ultimately requires integration of all elements of the production system. The goal is an optimally balanced production line with little waste, the lowest possible cost, on-time and defect-free production.
This strategy is typically applied in discrete manufacturing as an attempt to handle production volumes comprising discrete units of product in a flow which is more naturally found in process manufacturing. The basic fact is that in most cases, discrete units of a solid product cannot be handled in the same way as continuous quantities of liquid, gas or powder.
Discrete manufacturing is more likely to be performed in batches of product units that are routed from process to process in the factory. Each process may add value to the batch during a run-time or work-time. There is usually some time spent waiting for the process during a queue-time or wait-time. The larger the batch, the longer each unit has to wait for the rest of the batch to be completed, before it can go forward to the next process. This queue-time is waste, "Muda", and represents time lost that is not value-added in the eyes of the customer. This waste is one of the most important elements targeted for reduction and elimination in lean manufacturing.
Reducing the batch size in discrete manufacturing is therefore a desirable goal: it improves the speed of response to the customer, whilst improving the ratio of value-added to non value-added work. However, it should be balanced against the finite capacity of resources at the value-adding processes. Capacity is consumed by changeover whenever a process is required to perform work on a different part or product model than the preceding one. Time consumed in changeover is also considered waste, and it reduces the amount of resource capacity that is available to perform value-adding work. Reducing batch sizes can also increase handling time, risk and complexity in planning and controlling production.
The paradigm aim is to achieve single-piece flow where a single discrete unit of product flows from process to process. In effect, the batch quantity is one. If there is no change in part or product model, then this objective needs to be balanced against the additional handling time, and the work-centres that perform the process will typically have to be arranged in close proximity to one another in a flow-line. This is often a characteristic of Repetitive-flow manufacturing and most manual assembly work is performed this way in the modern factory.
If there is a change in part or product model, then the process engineer should also consider to balance the changeover time with run-time. If the changeover time is long, as it might be on a machine, batch size reduction is typically preceded with setup reduction techniques such as Single-Minute Exchange of Die.
One methodology for Repetitive-flow manufacturing is Demand Flow Technology which combines the principles of Repetitive-flow and demand-driven manufacturing. The production planning and control is linked to a pull signal that is triggered from a customer order or consumption of finished goods stock. A pull signal can also link a process to the down-stream, and synchronize the flow to the demand of the customer.


Pattern (casting)

In casting, a pattern is a replica of the object to be cast, used to prepare the cavity into which molten material will be poured during the casting process.
Patterns used in sand casting may be made of wood, metal, plastics or other materials. Patterns are made to exacting standards of construction, so that they can last for a reasonable length of time, according to the quality grade of the pattern being built, and so that they will repeatably provide a dimensionally acceptable casting.
Patternmaking.
The making of patterns, called patternmaking (sometimes styled pattern-making or pattern making), is a skilled trade that is related to the trades of tool and die making and moldmaking, but also often incorporates elements of fine woodworking. Patternmakers (sometimes styled pattern-makers or pattern makers) learn their skills through apprenticeships and trade schools over many years of experience. Although an engineer may help to design the pattern, it is usually a patternmaker who executes the design.
Materials used.
Typically, materials used for pattern making are wood, metal or plastics. Wax and Plaster of Paris are also used, but only for specialized applications. Sugar pine wood is the most commonly used material for patterns, primarily because it is soft, light, and easy to work. Honduras mahogany was used for more production parts because it is harder and would last longer than pine. Once properly cured, it is about as stable as any wood available, not subject to warping or curling. Once the pattern is built, the foundry does not want it changing shape. True Honduras mahogany is harder to find now because of the decimation of the rain forests, so now there is a variety of woods marketed as mahogany. Fiberglass and plastic patterns have gained popularity in recent years because they are water proof and very durable. Metal patterns are long lasting and do not succumb to moisture, but they are heavier, more expensive and difficult to repair once damaged.
Wax patterns are used in a casting process called investment casting. A combination of paraffin wax, bees wax and carnauba wax is used for this purpose.
Plaster of Paris is usually used in making master dies and molds, as it gains hardness quickly, with a lot of flexibility when in the setting stage.
Design.
Sprues, gates, risers, cores, and chills.
The patternmaker or foundry engineer decides where the "sprues", "gating" systems, and "risers" are placed with respect to the pattern. Where a hole is desired in a casting, a "core" may be used which defines a volume or location in a casting where metal will not flow into. Sometimes "chills" may be placed on a pattern surface prior to molding, which are then formed into the sand mould. Chills are heat sinks which enable localized rapid cooling. The rapid cooling may be desired to refine the grain structure or determine the freezing sequence of the molten metal which is poured into the mould. Because they are at a much cooler temperature, and often a different metal from what is being poured, they do not attach to the casting when the casting cools. The chills can then be reclaimed and reused.
The design of the feeding and gating system is usually referred to as "methoding" or "methods design". It can be carried out manually, or interactively using general-purpose CAD software, or semi-automatically using special-purpose software (such as AutoCAST)
Types of Patterns.
Patterns are made of wood, metal, ceramic, or hard plastics and vary in complexity.
A single piece pattern, or loose pattern, is the simplest. It is a replica of the desired casting—usually in a slightly larger size to offset the contraction of the intended metal. Gated patterns connect a number of loose patterns together with a series of runners that will be detached after shake-out. Segmented or multi-piece patterns create a casting in several pieces to be joined in post-processing.
Match plate patterns are patterns with the top and bottom parts of the pattern, also known as the cope and drag portions, mounted on opposite sides of a board. This adaptation allows patterns to be quickly moulded out of the molding material. A similar technique called a cope and drag pattern is often used for large castings or large production runs: in this variation, the two sides of the pattern are mounted on separate pattern plates that can be hooked up to horizontal or vertical machines and moulded with the molding material. When the parting lines between the cope and drag are irregular, a follow board can be used to support irregularly shaped, loose patterns.
Sweep patterns are used for symmetric molds, which are contoured shapes rotated around a center axis or pole through the molding material. A sweep pattern is a form of skeleton pattern: any geometrical pattern that creates a mold by being moved through the molding material.
Skeleton pattern comes into play when the entire setup made of wood or metal is costlier. It is made usually as a part with some gaps left unfilled and those unfilled parts are filled or covered by loam sand or clays. Strickle board or Strike-off board is used to scrape the excess clay if applied to the gaps.
E.g. Turbine Casing, Soil and Water pipe bends, valve bodies and boxes.
Allowances.
To compensate for any dimensional changes which will happen during the (solid) cooling process, allowances are usually made in the pattern.
Liquid Shrinkage.
Almost all metals shrink volumetrically during solidification, this is known as liquid shrinkage.
Another way of saying that is almost all metals undergo a volume increase upon melting, or liquidus temperature.
Typical "volume shrinkage" is in the range between 3.5% to 10.0% depending on the alloy.
Some graphitic cast irons, when cast in heavier sections, under well controlled conditions, can exhibit a slight positive yield.
Type Metal is also known, and used, for its ability to hold a true and sharp cast, and retain correct dimensions after cooling.
Normally when making engineering cast parts the "method" is designed along with the pattern - being the riser size, number of risers, and location of risers. Additionally downsprue(s), runner bar(s), and ingate(s) are also designed in "the method". The "method" thus ensures the molten metal is delivered, the mould filled correctly, and the risers filled to "feed" the "shrinking volume" of liquid to the casting during solidification. This "method" is done by a "methods engineer", who may be a patternmaker (with additional training), a founding engineer, or metallurgist who is familiar with concept of volume increase / volume loss associated with melting and casting / solidification. Example: Assume steel at 7.85 density (solid) and 6% shrinkage, or better said, a 6% volume increase when molten. A mould has been made to cast a 100 kg block, based on the solid density of steel. The liquid density of steel is only 94% that of its solid density value - about 7.38 when liquid. Thus when the 100 kg block (solid calculation) is filled with liquid it contains a mass of only 94 kg. The 6 kg, has to be supplied from a "riser" or "feeder" during solidification - thus the solid object now has a mass of 100 kg.
The method is a system to deal with the volume loss during solidification. This (technically) is not an allowance.
This extra size that is given on the pattern for metal contraction is called "the contraction allowance".
These values are typically between 0.6% and 2.5%.
This is accounted for using a contraction rule, which is an oversized rule. Contraction rules are generally available for the common industrially cast alloys. Alternately, the Patternmaker will simply add a nominated percentage to all dimensions.
An example of this allowance - if a bush were required to be 1500mm O/D, 1000mm I/D and 300mm high using a 2% contraction rule: The Patternmaker would make the pattern 1530mm O/D, (as it will contract in), 1020 I/D (as material tend to contract towards the Centre or Centre of gravity ) - important to note that allowance is added even to the inside diameter as material tend to contact towards the Centre. The core used is either made up of collapsible sand or it is given enough hollow space at the centre of the core to allow metal to expand. Finally, the height dimension would be 306mm.
The contraction amount can also be varied slightly by the sand system being used for the mould and any cores, for example clay-bonded sand, chemical bonded sands, or other bonding materials used within the sand. Exact values can vary between different foundries due to the sand systems being used. Each foundry, by gauging its own patterns and castings, can refine its own contraction allowances.
Shrinkage and Contraction can again be classified into "liquid shrinkage" and "solid contraction".
Liquid shrinkage is the reduction in volume during the process of solidification (liquid to solid), the liquid shrinkage is accounted for by risers.
Solid contraction is the reduction in dimensions during the cooling of the (solid) cast metal. Contraction allowance takes into account only the solid contraction.
Draft allowance.
When the pattern is to be removed from the sand mold, there is a possibility that any leading edges may break off, or get damaged in the process. To avoid this, a taper is provided on the pattern, so as to facilitate easy removal of the pattern from the mold, and hence reduce damage to edges. The taper angle provided is called the "Draft angle". The value of the draft angle depends upon the complexity of the pattern, the type of molding (hand molding or machine molding), height of the surface, etc. Draft provided on the casting is usually 1 to 3 degrees on external surfaces (5 to 8 internal surfaces).
Finishing or Machining allowance.
The surface finish obtained in sand castings is generally poor (dimensionally inaccurate), and hence in many cases, the cast product is subjected to machining processes like turning or grinding in order to improve the surface finish. During machining processes, some metal is removed from the piece. To compensate for this, a machining allowance (additional material some times referred to as green) should be given in the casting. the amount of finish allowance depends on the material of the casting, size of casting, volume of production, method of molding, etc.
Shake allowance.
Usually during removal of the pattern from the mold cavity, the pattern is rapped all around the faces, in order to facilitate easy removal. In this process, the final cavity is enlarged. To compensate for this, the pattern dimensions need to be reduced. There are no standard values for this allowance, as it is heavily dependent on the personnel. This allowance is a negative allowance, and a common way of going around this allowance is to increase the draft allowance. Shaking of the pattern causes an enlargement of the mould cavity and results in a bigger casting.
Distortion allowance.
During cooling of the mould, stresses developed in the solid metal may induce distortions in the cast. This is more evident when the mould is thinner in width as compared to its length. This can be eliminated by initially distorting the pattern in the opposite direction.
Demand.
Patterns continue to be needed for sand casting of metals. For the production of gray iron, ductile iron and steel castings, sand casting remains the most widely used process. For aluminum castings, sand casting represents about 12% of the total tonnage by weight (surpassed only by die casting at 57%, and semi-permanent and permanent mold at 19%; based on 2006 shipments). The exact process and pattern equipment is always determined by the order quantities and the casting design. Sand casting can produce as little as one part, or as many as a million copies.
Although additive manufacturing modalities such as SLS or SLM have potential to replace casting for some production situations, casting is still far from being completely displaced. Wherever it provides suitable material properties at competitive unit cost, it will remain in demand.


Rotary table

A rotary table is a precision work positioning device used in metalworking. It enables the operator to drill or cut work at exact intervals around a fixed (usually horizontal or vertical) axis. Some rotary tables allow the use of index plates for indexing operations, and some can also be fitted with dividing plates that enable regular work positioning at divisions for which indexing plates are not available. A rotary fixture used in this fashion is more appropriately called a dividing head (indexing head).
Construction.
The table shown is a manually operated type. Powered tables under the control of CNC machines are now available, and provide a fourth axis to CNC milling machines. Rotary tables are made with a solid base, which has provision for clamping onto another table or fixture. The actual table is a precision-machined disc to which the work piece is clamped (T slots are generally provided for this purpose). This disc can rotate freely, for indexing, or under the control of a worm (handwheel), with the worm wheel portion being made part of the actual table. High precision tables are driven by backlash compensating duplex worms.
The ratio between worm and table is generally 40:1, 72:1 or 90:1 but may be any ratio that can be easily divided exactly into 360°. This is for ease of use when indexing plates are available. A graduated dial and, often, a vernier scale enable the operator to position the table, and thus the work affixed to it with great accuracy.
A through hole is usually machined into the table. Most commonly, this hole is machined to admit a Morse taper center or fixture.
Use.
Rotary tables are most commonly mounted "flat", with the table rotating around a vertical axis, in the same plane as the cutter of a vertical milling machine. An alternate setup is to mount the rotary table on its end (or mount it "flat" on a 90° angle plate), so that it rotates about a horizontal axis. In this configuration a tailstock can also be used, thus holding the workpiece "between centers."
With the table mounted on a secondary table, the workpiece is accurately centered on the rotary table's axis, which in turn is centered on the cutting tool's axis. All three axes are thus coaxial. From this point, the secondary table can be offset in either the X or Y direction to set the cutter the desired distance from the workpiece's center. This allows concentric machining operations on the workpiece. Placing the workpiece eccentrically a set distance from the center permits more complex curves to be cut. As with other setups on a vertical mill, the milling operation can be either drilling a series of concentric, and possibly equidistant holes, or face or end milling either circular or semicircular shapes and contours.
A rotary table can be used:
Additionally, if converted to stepper motor operation, with a CNC milling machine and a tailstock, a rotary table allows many parts to be made on a mill that otherwise would require a lathe.
Applications.
Rotary tables have many applications, including being used in the manufacture and inspection process of important elements in aerospace, automation and scientific industries. The use of rotary tables stretches as far as the film and animation industry, being used to obtain accuracy and precision in filming and photography.


Coordinate-measuring machine

A coordinate measuring machine (CMM) is a device that measures the geometry of physical objects by sensing discrete points on the surface of the object with a probe. Various types of probes are used in CMMs, the most common being mechanical and laser sensors, though optical and white light sensor do exist. Depending on the machine, the probe position may be manually controlled by an operator or it may be computer controlled. CMMs typically specify a probe's position in terms of its displacement from a reference position in a three-dimensional Cartesian coordinate system (i.e., with XYZ axes). In addition to moving the probe along the X, Y, and Z axes, many machines also allow the probe angle to be controlled to allow measurement of surfaces that would otherwise be unreachable.
Description.
The typical 3D "bridge" CMM allows probe movement along three axes, X, Y and Z, which are orthogonal to each other in a three-dimensional Cartesian coordinate system. Each axis has a sensor that monitors the position of the probe on that axis, with typical accuracy in the order of microns. When the probe contacts (or otherwise detects) a particular location on the object, the machine samples the axis position sensors, thus measuring the location of one point on the object's surface, as well as the 3-dimensional vector of the measurement taken. This process is repeated as necessary, moving the probe each time, to produce a "point cloud" which describes the surface areas of interest. The points can be measured either manually by an operator or automatically via Direct Computer Control (DCC) or automatically using scripted programs; thus, an automated CMM is a specialized form of industrial robot.
A common use of CMMs is in manufacturing and assembly processes to test a part or assembly against the design intent. The measured points can be used to verify the distance between features. They can also be used to construct geometric features such as cylinders and planes etc. for GD&T such as roundness, flatness and perpendicularity can be assessed.
Technical facts.
Parts.
Coordinate-measuring machines include three main components:
Availability.
These machines are available as stationary or portable.
Accuracy.
The accuracy of coordinate measurement machines are typically given as an uncertainty factor as a function over distance. For a CMM using a touch probe, this relates to the repeatability of the probe and the accuracy of the linear scales. Typical probe repeatability can result in measurements of within .001mm or .00005 inch (half a ten thousandth) over the entire measurement volume. For 3, 3+2, and 5 axis machines, probes are routinely calibrated using traceable standards and the machine movement is verified using gauges to ensure accuracy.
Specific parts.
Machine body.
The first CMM was developed by the Ferranti Company of Scotland in the 1950s as the result of a direct need to measure precision components in their military products, although this machine only had 2 axes. The first 3-axis models began appearing in the 1960s (DEA of Italy / LK of the UK) and computer control debuted in the early 1970s but the first working CMM was developed and put on sale by Browne & Sharpe in Melbourne, England. (Leitz Germany subsequently produced a fixed machine structure with moving table.
In modern machines, the gantry-type superstructure has two legs and is often called a bridge. This moves freely along the granite table with one leg (often referred to as the inside leg) following a guide rail attached to one side of the granite table. The opposite leg (often outside leg) simply rests on the granite table following the vertical surface contour. Air bearings are the chosen method for ensuring friction free travel. In these, compressed air is forced through a series of very small holes in a flat bearing surface to provide a smooth but controlled air cushion on which the CMM can move in a near frictionless manner which can be compensated for through software. The movement of the bridge or gantry along the granite table forms one axis of the XY plane. The bridge of the gantry contains a carriage which traverses between the inside and outside legs and forms the other X or Y horizontal axis. The third axis of movement (Z axis) is provided by the addition of a vertical quill or spindle which moves up and down through the center of the carriage. The touch probe forms the sensing device on the end of the quill. The movement of the X, Y and Z axes fully describes the measuring envelope. Optional rotary tables can be used to enhance the approachability of the measuring probe to complicated workpieces. The rotary table as a fourth drive axis does not enhance the measuring dimensions, which remain 3D, but it does provide a degree of flexibility. Some touch probes are themselves powered rotary devices with the probe tip able to swivel vertically through more than 180 degrees and through a full 360 degree rotation.
CMMs are now also available in a variety of other forms. These include CMM arms that use angular measurements taken at the joints of the arm to calculate the position of the stylus tip, and can be outfitted with probes for laser scanning and optical imaging. Such arm CMMs are often used where their portability is an advantage over traditional fixed bed CMMs- by storing measured locations, programming software also allows moving the measuring arm itself, and its measurement volume, around the part to be measured during a measurement routine. Because CMM arms imitate the flexibility of a human arm they are also often able to reach the insides of complex parts that could not be probed using a standard three axis machine.
Mechanical probe.
In the early days of coordinate measurement (CMM), mechanical probes were fitted into a special holder on the end of the quill. A very common probe was made by soldering a hard ball to the end of a shaft. This was ideal for measuring a whole range of flat face, cylindrical or spherical surfaces. Other probes were ground to specific shapes, for example a quadrant, to enable measurement of special features. These probes were physically held against the workpiece with the position in space being read from a 3-axis digital readout (DRO) or, in more advanced systems, being logged into a computer by means of a footswitch or similar device. Measurements taken by this contact method were often unreliable as machines were moved by hand and each machine operator applied different amounts of pressure on the probe or adopted differing techniques for the measurement.
A further development was the addition of motors for driving each axis. Operators no longer had to physically touch the machine but could drive each axis using a handbox with joysticks in much the same way as with modern remote controlled cars. Measurement accuracy and precision improved dramatically with the invention of the electronic touch trigger probe. The pioneer of this new probe device was David McMurtry who subsequently formed what is now Renishaw plc. Although still a contact device, the probe had a spring-loaded steel ball (later ruby ball) stylus. As the probe touched the surface of the component the stylus deflected and simultaneously sent the X,Y,Z coordinate information to the computer. Measurement errors caused by individual operators became fewer and the stage was set for the introduction of CNC operations and the coming of age of CMMs.
Optical probes are lens-CCD-systems, which are moved like the mechanical ones, and are aimed at the point of interest, instead of touching the material. The captured image of the surface will be enclosed in the borders of a measuring window, until the residue is adequate to contrast between black and white zones. The dividing curve can be calculated to a point, which is the wanted measuring point in space. The horizontal information on the CCD is 2D (XY) and the vertical position is the position of the complete probing system on the stand Z-drive (or other device component).
Scanning probe systems.
There are newer models that have probes that drag along the surface of the part taking points at specified intervals, known as scanning probes. This method of CMM inspection is often more accurate than the conventional touch-probe method and most times faster as well.
The next generation of scanning, known as noncontact scanning, which includes high speed laser single point triangulation, laser line scanning, and white light scanning, is advancing very quickly. This method uses either laser beams or white light that are projected against the surface of the part. Many thousands of points can then be taken and used not only to check size and position, but to create a 3D image of the part as well. This "point-cloud data" can then be transferred to CAD software to create a working 3D model of the part. These optical scanners are often used on soft or delicate parts or to facilitate reverse engineering.
Probing systems for microscale metrology applications are another emerging area. There are several commercially available coordinate measuring machines (CMM) that have a microprobe integrated into the system, several specialty systems at government laboratories, and any number of university-built metrology platforms for microscale metrology. Although these machines are good and in many cases excellent metrology platforms with nanometric scales, their primary limitation is a reliable, robust, capable micro/nano probe. Challenges for microscale probing technologies include the need for a high aspect ratio probe giving the ability to access deep, narrow features with low contact forces so as to not damage the surface and high precision (nanometer level). Additionally microscale probes are susceptible to environmental conditions such as humidity and surface interactions such as stiction (caused by adhesion, meniscus, and/or Van der Waals forces among others).
Technologies to achieve microscale probing include scaled down version of classical CMM probes, optical probes, and a standing wave probe among others. However, current optical technologies cannot be scaled small enough to measure deep, narrow feature, and optical resolution is limited by the wavelength of light. X-ray imaging provides a picture of the feature but no traceable metrology information.
Optical probes and/or laser probes can be used (if possible in combination), which change CMMs to measuring microscopes or multi-sensor measuring machines. Fringe projection systems, theodolite triangulation systems or laser distant and triangulation systems are not called measuring machines, but the measuring result is the same: a space point. Laser probes are used to detect the distance between the surface and the reference point on the end of the kinematic chain (i.e.: end of the Z-drive component). This can use an interferometrical function, focus variation, light deflection or a beam shadowing principle.
Portable coordinate-measuring machines.
Whereas traditional CMMs use a probe that moves on three Cartesian axes to measure an object's physical characteristics, portable CMMs use either articulated arms or, in the case of optical CMMs, arm-free scanning systems that use optical triangulation methods and enable total freedom of movement around the object.
Portable CMMs with articulated arms have six or seven axes that are equipped with rotary encoders, instead of linear axes. Portable arms are lightweight (typically less than 20 pounds) and can be carried and used nearly anywhere. However, optical CMMs are increasingly being used in the industry. Designed with compact linear or matrix array cameras (like the Microsoft Kinect), optical CMMs are smaller than portable CMMs with arms, feature no wires, and enable users to easily take 3D measurements of all types of objects located almost anywhere.
Certain nonrepetitive applications such as reverse engineering, rapid prototyping, and large-scale inspection of parts of all sizes are ideally suited for portable CMMs. The benefits of portable CMMs are multifold. Users have the flexibility in taking 3D measurements of all types of parts and in the most remote/difficult locations. They are easy to use and do not require a controlled environment to take accurate measurements. Moreover, portable CMMs tend to cost less than traditional CMMs.
The inherent trade-offs of portable CMMs are manual operation (they always require a human to use them). In addition, their overall accuracy can be somewhat less accurate than that of a bridge type CMM and is less suitable for some applications.
Multisensor-measuring machines.
Traditional CMM technology using touch probes is today often combined with other measurement technology. This includes laser, video or white light sensors to provide what is known as multisensor measurement.
Standardization.
To verify the performance of a coordinate measurement machine, the ISO 10360 series is available. This series of standards define the characteristics of the probing system and the length measurement error:
The ISO 10360 series consists of the following parts:


Reproduction auto part

A reproduction part, or repro, is a part that has been independently manufactured to meet original equipment manufacturer's (OEM) specifications by a third party manufacturer. This is usually done to meet demand for spare parts no longer produced by the manufacturer. While some reproductions may be indistinguishable from the originals, most are close imitations.


ITW Mima Packaging Systems

ITW Mima Packaging Systems is the European marketing division of ITW's Specialty Systems businesses, manufacturing fully automatic stretch wrapping machines in Finland, semi-automatic and automatic machines in Bulgaria and manufacturing film in Belgium and Ireland.
Overview.
Mima was founded in 1976 in the United States, to manufacture stretch wrapping machinery it was acquired by ITW in 1986. Alongside this, Matti Haloila started his own company in Finland and manufactured HaloilaHaloila - Etusivu semi-automatic stretch wrappers from 1976. In 1983 Haloila launched an automatic, rotating ring stretch wrapper with the brand name Octopus.
Haloila became part of the Illinois Tool Works (ITW) in 1995, shortly after this, ITW acquired the stretch film business from Mobil and ITW Mima Packaging System was formed. ITW Mima Packaging Systems manufacture stretch films in Belgium and Ireland and stretch wrappers in Bulgaria and Finland.
In 2006 Mima launched the Octopus Twin a wrapping machine capable of wrapping 150 pallets per hour. ITW Mima delivered their 3000th Octopus stretch wrapper in 2008.
The Octopus is also currently being manufactured for the US market in Canada by ITW Muller.
Other Haloila’s wrapping machines include the Cobra, Ecomat and Rolle.
ITW Mima Packagings Systems is a member of the Process and Packaging Machinery Association (PPMA)


Via fence

A via fence, also called a picket fence, is a structure used in planar electronic circuit technologies to improve isolation between components which would otherwise be coupled by electromagnetic fields. It consists of a row of via holes which, if spaced close enough together, form a barrier to electromagnetic wave propagation of slab modes in the substrate. Additionally if radiation in the air above the board is also to be suppressed, then a strip pad with via fence allows a shielding can to be electrically attached to the top side, but electrically behave as if it continued through the PCB.
Modern electronics have components and sub-units at high densities to achieve small size. Typically, many functions are integrated on to the same board or die. If these are not properly shielded from each other, many problems can result including poor frequency response, noise performance, and distortion.
Via fences are used to shield microstrip and stripline transmission lines, guard edges of printed circuit boards, shield functional circuit units from each other, and to form the walls of waveguides integrated into a planar format. Via fences are cheap and easy to implement, but use up board space and are not as effective as solid metal walls.
Purpose.
Planar technologies are used at microwave frequencies and make use of printed circuit tracks as transmission lines. As well as interconnections, these lines can be used to form components of functional units such as filters and couplers. Planar lines readily couple to each other when in close proximity, an effect called parasitic coupling. The coupling is due to fringing fields spreading from the edges of the line and intersecting adjacent lines or components. This is a desirable feature within the unit where it is made use of as part of the design. It is not desirable, however, that the fields couple to adjacent units. Modern electronic devices are usually required to be small. That, and the drive to keep down costs, leads to a high degree of integration and circuit units in less than desirable proximity. Via fences are one method that can be used to reduce parasitic coupling between such units.
Amongst the many problems that can be caused by parasitic coupling are reducing bandwidth, degrading passband flatness, reducing amplifier output power, increasing reflections, worsening noise figure, causing amplifier instability, and providing undesirable feedback paths.
In stripline, via fences running parallel to the line on either side serve to tie together the groundplanes, so preventing the propagation of parallel-plate modes. A similar arrangement is used to suppress unwanted modes in metal-backed coplanar waveguide.
Structure.
A via fence consists of a row of via holes, that is, holes that pass through the substrate and are metallised on the inside to connect to pads on the top and bottom of the substrate. In a stripline format both the top and bottom of the dielectric sheet are covered with a metal ground plane so any via holes are automatically grounded at both ends. In other planar formats such as microstrip there is a ground plane only at the bottom of the substrate. In these formats it is the usual practice to connect the top pads of the via fence with a metal track (see figure 2). This still does not completely fence off the field as can be done in stripline. In stripline the field can only propagate between the ground planes, but in microstrip it is able to leak over the top of the via fence. Nevertheless, connecting the top pads improves isolation by . In some technologies it is more convenient to form the fence from conducting posts rather than vias.
Isolation can be further improved by placing a metal wall on top of the via fence. These walls commonly form part of the device enclosure. The large holes in the via fences seen in figures 1 and 5 are screw holes for clamping these walls in place. The wall casting belonging to this circuit is shown in figure 3.
The design of the fence needs to consider the size and spacing of the vias. Ideally, vias should act as short circuits, but they are not ideal and a via equivalent circuit can be modelled as a shunt inductance. Sometimes, a more complex model is required such as the equivalent circuit shown in figure 4. "L"1 is due to the inductance of the pads and "C" is the capacitance between them. "R" and "L"2 are, respectively, the resistance and inductance of the via hole metallisation. Resonances must be considered, in particular the parallel resonance of "C" and "L"2 will allow electromagnetic waves to pass at the resonant frequency. This resonance needs to be placed outside the operating frequencies of the equipment concerned. Spacing of the fences needs to be small in comparison to a wavelength (λ) in the substrate dielectric so as to make the fence appear solid to impinging waves. If too large, waves will be able to pass through the gaps. A common rule of thumb is to make the spacing less than λ/20 at the maximum operating frequency.
Applications.
Via fences are used primarily at RF and microwave frequencies wherever planar formats are being applied. They are used in printed circuit technologies such as microstrip, ceramic technologies such as low temperature co-fired ceramic, monolithic microwave integrated circuits, and system-in-a-package technology. They are especially important in isolating circuit units operating at different frequencies.
Also called via stitching, via fences can be used around the edge of a printed circuit board, an example can be seen in figure 5. This may be done to prevent electromagnetic interference with other equipment, or even to block radiation re-entering from elsewhere on the same circuit.
Via fences are also used in post-wall waveguide, also known as laminated waveguide (LWG). In LWG, two parallel via fences form the sidewalls of a waveguide. Between them, and the upper and lower groundplanes of the substrate, is an electromagnetically isolated space. There is no electrical conductor within this space, but electromagnetic waves can exist within the enclosed dielectric material of the substrate and their direction of propagation is guided by the LWG. This technology is typically used at millimetre band frequencies and consequently dimensions are quite small. Furthermore, good isolation requires that the vias are closely spaced. Typically, isolation is required between guides, that is per fence. A typical W band  fence specification meeting this requirement in LWG is vias spaced between centres. This can be challenging to manufacture, and a higher density of vias is sometimes achieved by constructing the fence from two staggered rows of vias.
Advantages and disadvantages.
Via fences are cheap and convenient. When used on planar formats they require no additional processes to manufacture. On a printed circuit for instance, they are made in the same process that creates the track patterns. However, via fences are not able to approach the isolation achievable with unbroken metal walls.
Via fences use up a lot of valuable substrate real estate and so will increase the overall size of the assembly. Via fences too close to the line being guarded can degrade the isolation otherwise achievable. In stripline, a rule of thumb is to place the fences at least four times the trace to groundplane distance away from the line being guarded.


Insertion mount machine

An insertion mount machine or inserter is a device used to insert the leads of electronic components through holes in printed circuit boards.
Machine configuration.
An insertion mount machine often has a rotary table on a X- and Y-axis positioning system which moves the board to the necessary position for the component's insertion into the board. The machine can be configured to be standalone machine.
Axial insertion.
An axial inserter takes axial leaded through-hole components from reels which are fed into dispensing heads that cut the parts onto a chain in the order of insertion; transferred from the sequence chain to the insertion chain, which brings the component underneath the insertion head which then cuts the leads of the component to the correct length for lead length and insertion span; bends the leads 90°; and inserts the component leads into the board while a clinch assembly underneath cuts and bends the leads towards each other.
Radial insertion.
A radial inserter takes radial leaded through-hole components from a reels which are fed into dispensing heads that cut the component from the reel and place it onto the chain in sequence of the order of insertion. The component is brought to a component transfer assembly behind the insertion head and is transferred to the insertion head, then inserted into the board while a clinch assembly underneath cuts and bends the leads opposite to each other.
Dual in-line package insertion.
A dual in-line (DIP) inserter takes integrated circuits from tubes which are loaded into magazines. A shuttle mechanism picks the needed component needed from the magazines and drops it into a transfer assembly. The insertion head picks the component from the transfer assembly and inserts the IC into the board while a clinch assembly underneath cuts and bends the leads either inward for sockets or outward for ICs.
Due to the transition from insertion mount technology (through-hole) to surface-mount technology of integrated circuits, these machines are no longer being newly manufactured.
Obsolete configurations.
Axial inserters used to consist of a stand-alone sequencer machine which cut and sequenced the parts onto a reel. That reel was then transferred over to a standalone axial inserter to insert the components. This is all done on one machine today.


Operating weight

Operating weight is a measure of the total weight of a vehicle or machine when it is in use, including all necessary components such as the driver or operator, fuel, and any additional equipment or tools required for its operation.


Master production schedule

A master production schedule (MPS) is a plan for individual commodities to be produced in each time period such as production, staffing, inventory, etc. It is usually linked to manufacturing where the plan indicates when and how much of each product will be demanded. This plan quantifies significant processes, parts, and other resources in order to optimize production, to identify bottlenecks, and to anticipate needs and completed goods. Since a MPS drives much factory activity, its accuracy and viability dramatically affect profitability. Typical MPSs are created by software with user tweaking.
Due to software limitations, but especially the intense work required by the "master production schedulers", schedules do not include every aspect of production, but only key elements that have proven their control effectivity, such as forecast demand, production costs, inventory costs, lead time, working hours, capacity, inventory levels, available storage, and parts supply. The choice of what to model varies among companies and factories. The MPS is a statement of what the company expects to produce and purchase (i.e. quantity to be produced, staffing levels, dates, available to promise, projected balance).
The MPS translates the customer demand (sales orders, PIR’s), into a build plan using planned orders in a true component scheduling environment. Using MPS helps avoid shortages, costly expediting, last minute scheduling, and inefficient allocation of resources. Working with MPS allows businesses to consolidate planned parts, produce master schedules and forecasts for any level of the Bill of Material (BOM) for any type of part.
How an MPS works.
By using many variables as inputs the MPS will generate a set of outputs used for decision making. Inputs may include forecast demand, production costs, inventory money, customer needs, inventory progress, supply, lot size, production lead time, and capacity. Inputs may be automatically generated by an ERP system that links a sales department with a production department. For instance, when the sales department records a sale, the forecast demand may be automatically shifted to meet the new demand. Inputs may also be inputted manually from forecasts that have also been calculated manually. Outputs may include amounts to be produced, staffing levels, quantity available to promise, and projected available balance. Outputs may be used to create a Material Requirements Planning (MRP) schedule.
A master production schedule may be necessary for organizations to synchronize their operations and become more efficient. An effective MPS ultimately will:
MPS issues:
Production plan.
An example of a master production schedule for "product A".


Lot number

A lot number is an identification number assigned to a particular quantity or lot of material from a single manufacturer. Lot numbers can typically be found on the outside of packaging. For cars, a lot number is combined with a serial number to form the Vehicle Identification Number.
The lot number enables tracing of the constituent parts or ingredients as well as labor and equipment records involved in the manufacturing of a product. This enables manufacturers and other entities to perform quality control checks, calculate expiration dates, and issue corrections or recall information to subsets of their production output. It also gives consumers an identifier that they can use in contacting the manufacturer and researching the production of goods received. For example to trace back the origin of fish or meat, in case of a public health problem.
Some lot numbers are generated with the use of date and time stamps to help identify a specific lot.


Overstock

Overstock, excessive stock, or excess inventory arise when there is more than the "right quantity" of goods available for sale, or when "the the potential sales value of excess stock, less the expected storage costs, does not match the salvage value". It arises as a result of poor management of stock demand or of material flow in process management. Excessive stock is also associated with loss of revenue owing to additional capital bound with the purchase or simply storage space taken. Excessive stock can result from over delivery from a supplier or from poor ordering and management of stock by a buyer for the stock. Excess or unnecessary inventory is listed as one of the seven wastes or "muda" in Taiichi Ohno's Toyota production system.
When referring to overstock merchandise in the form of consumer goods in a retail operation, the term refers to goods that have never been purchased by a customer but that are considered excessive stock from shelves and/or warehouses. Excessive stock is typically discarded of in the following ways: returned to the manufacturer or original distributor; liquidated to companies that then resell it on the secondary wholesale or retail market; sold at an extreme discount to existing customers; or sold to salvage companies which then process metals and components of value.
Techniques such as supply chain management and lean manufacturing are intended to avoid the excessive development of inventory.
Economic implications.
The initial damage caused by excessive stock is an early exhaustion of cash flow, which leads to the subsequent loss of disposable capital available for investing. If a company has too much overstock inventory on its books, it may affect sales to the point where the company has to go out of business. Although this is rare, when overstock inventory is not properly managed and becomes too large a percentage of total inventory, it can result in bankruptcy.
With perishable supplies, excessive stock can cause the loss of millions of currency units as the product's freshness may deteriorate to such an extent that it cannot be sold, as is the case with dairy products, fresh baked goods, flowers, produce, fish, and meat. It is also true of consumables such as oil, gasoline, paints, and medications. Time-sensitive items such as periodical literature are similarly at risk.
Sales of excess inventories.
Crandall and Crandall reported 238,000 responses to a web search for "excess inventories" in 2003, with a majority of websites offering to buy or sell "excess inventories" in specific sales categories.


Machine operator efficiency

In lean manufacturing, machine operator efficiency (MOE) is the performance of an employee who operates industrial machinery. The operator's efficiency is measured as the time spent producing product divided by the time the operator is on duty. For example: if an operator is assigned to run a CNC machine tool for seven hours, but they only have four hours' worth of continuous uninterrupted output of workpieces—their MOE rating is 57% (4 divided by 7) for this seven-hour period of time.
There is a similar lean manufacturing KPI called overall equipment effectiveness (OEE). The major difference between OEE and MOE is that the OEE rating is on the machine and the MOE is on the person.
MOE is a measure of operator performance only, regardless of the type of machine or the speed of the machine they are working on. MOE only measures the operator's ability to keep the machine running continuously (load and unload parts faster that the automatic cycle time of the machine). The MOE rating of an operator will travel with them as they moves from one machine to another. This is easily accomplished because the MOE rating is a universal calculation of time and not reliant on the complex OEE calculations of loading, availability, performance, and quality.
Industrial dashboards can be used to display statistics for MOE ratings on each operator. To boost overall profitability for a manufacturing plant, machine operators are sometimes compensated with a salary bonus based on their MOE ratings.


DFM analysis for stereolithography

In design for additive manufacturing (DFAM), there are both broad themes (which apply to many additive manufacturing processes) and optimizations specific to a particular AM process. Described here is DFM analysis for stereolithography, in which design for manufacturability (DFM) considerations are applied in designing a part (or assembly) to be manufactured by the stereolithography (SLA) process. In SLA, parts are built from a photocurable liquid resin that cures when exposed to a laser beam that scans across the surface of the resin (photopolymerization). Resins containing acrylate, epoxy, and urethane are typically used. Complex parts and assemblies can be directly made in one go, to a greater extent than in earlier forms of manufacturing such as casting, forming, metal fabrication, and machining. Realization of such a seamless process requires the designer to take in considerations of manufacturability of the part (or assembly) by the process. In any product design process, DFM considerations are important to reduce iterations, time and material wastage.
Challenges in stereolithography.
Material.
Excessive setup specific material cost and lack of support for 3rd party resins is a major challenge with SLA process:. The choice of material (a design process) is restricted by the supported resin. Hence, the mechanical properties are also fixed. When scaling up dimensions selectively to deal with expected stresses, post curing is done by further treatment with UV light and heat. Although advantageous to mechanical properties, the additional polymerization and cross linkage can result in shrinkage, warping and residual thermal stresses. Hence, the part shall be designed in its 'green' stage i.e. pre-treatment stage.
Setup and process.
SLA process is an additive manufacturing process. Hence, design considerations such as orientation, process latitude, support structures etc. have to be considered.
Orientation affects the support structures, manufacturing time, part quality and part cost. Complex structures may fail to manufacture properly due to orientation which is not feasible resulting in undesirable stresses. This is when the DFM guidelines can be applied. Design feasibility for stereolithography can be validated by analytical as well as on the basis of simulation and/or guidelines
Rule-based DFM considerations.
Rule-based considerations in DFM refer to certain criteria that the part has to meet in order to avoid failures during manufacturing. Given the layer-by-layer manufacturing technique the process follows, there isn't any constraint on the overall complexity that the part may have. But some rules have been developed through experience by the printer developer/academia which must be followed to ensure that the individual features that make up the part are within certain 'limits of feasibility'.
Printer constraints.
Constraints/limitations in SLA manufacturing comes from the printer's accuracy, layer thickness, speed of curing, speed of printing etc. Various printer constraints are to be considered during design such as:
Support structures.
A point needs support if:
While printing, support structures act as a part of design hence, their limitations and advantages are kept in mind while designing. Major considerations include:
Part deposition orientation.
Part orientation is a very crucial decision in DFM analysis for SLA process. The build time, surface quality, volume/number of support structures etc. depend on this. In many cases, it is also possible to address the manufacturability issues just by reorienting the part. For example, an overhanging geometry with shallow angle may be oriented to ensure steep angles. Hence, major considerations include:
Plan-based DFM considerations.
Plan-based considerations in DFM refer to criteria that arise due to process plan. These are to be met in order to avoid failures during manufacturing of a part that may be satisfy the rule-based criteria but may have some manufacturing difficulties due to sequence in which features are produced.
Geometric tailoring.
Geometric Tailoring bridges the mismatch of material properties and process differences described above. Both functionality and manufacturability issues are addressed. Functionality issues are addressed through 'tailoring' of dimensions of the part to compensate the stress and deflection behavior anomalies. Manufacturability issues are tackled through identification of difficult to manufacture geometric attributes (an approach used in most DFM handbooks) or through simulations of manufacturing processes. For RP-produced parts (as in SLA), the problem formulations are called material-process geometric tailoring (MPGT)/RP.
First, the designer specifies information such as: Parametric CAD model of the part; constraints and goals on functional, geometry, cost and time characteristics; analysis models for these constraints and goals; target values of goals; and preferences for the goals.
DFM problem is then formulated as the designer fills in the MPGT template with this information and sends to the manufacturer, who fills in the remaining 'manufacturing relevant' information. With the completed formulation, the manufacturer is now able to solve the DFM problem, performing GT of the part design. Hence, the MPGT serves as the digital interface between the designer and the manufacturer.
Various Process Planning (PP) strategies have been developed for geometric tailoring in SLA process.
DFM frameworks.
The constraints imposed by the manufacturing process are mapped onto the design. This helps in identification of DFM problems while exploring process plans by acting as a retrieval method. Various DFM frameworks are developed in literature. These frameworks help in various decision making steps such as:
External links.
Dfm2U Live


Virtual machining

Virtual machining is the practice of using computers to simulate and model the use of machine tools for part manufacturing. Such activity replicates the behavior and errors of a real environment in virtual reality systems. This can provide useful ways to manufacture products without physical testing on the shop floor. As a result, time and cost of part production can be decreased.
Applications.
Virtual machining provides various benefits:
Future research works.
Some suggestions for the future studies in virtual machining systems are presented as:


Integrated circuit layout

In integrated circuit design, integrated circuit (IC) layout, also known IC mask layout or mask design, is the representation of an integrated circuit in terms of planar geometric shapes which correspond to the patterns of metal, oxide, or semiconductor layers that make up the components of the integrated circuit. Originally the overall process was called tapeout, as historically early ICs used graphical black crepe tape on mylar media for photo imaging (erroneously believed to reference magnetic data—the photo process greatly predated magnetic media).
When using a standard process—where the interaction of the many chemical, thermal, and photographic variables is known and carefully controlled—the behaviour of the final integrated circuit depends largely on the positions and interconnections of the geometric shapes. Using a computer-aided layout tool, the layout engineer—or layout technician—places and connects all of the components that make up the chip such that they meet certain criteria—typically: performance, size, density, and manufacturability. This practice is often subdivided between two primary layout disciplines: analog and digital.
The generated layout must pass a series of checks in a process known as physical verification. The most common checks in this verification process are
When all verification is complete, layout post processing is applied where the data is also translated into an industry-standard format, typically GDSII, and sent to a semiconductor foundry. The milestone completion of the layout process of sending this data to the foundry is now colloquially called "tapeout". The foundry converts the data into mask data and uses it to generate the photomasks used in a photolithographic process of semiconductor device fabrication.
In the earlier, simpler, days of IC design, layout was done by hand using opaque tapes and films, an evolution derived from early days of printed circuit board (PCB) design -- tape-out.
Modern IC layout is done with the aid of IC layout editor software, mostly automatically using EDA tools, including place and route tools or schematic-driven layout tools.
Typically this involves a library of standard cells.
The manual operation of choosing and positioning the geometric shapes is informally known as "polygon pushing".


Capacitive displacement sensor

Capacitive displacement sensors "are non-contact devices capable of high-resolution measurement of the position and/or change of position of any conductive target". They are also able to measure the thickness or density of non-conductive materials. Capacitive displacement sensors are used in a wide variety of applications including semiconductor processing, assembly of precision equipment such as disk drives, precision thickness measurements, machine tool metrology and assembly line testing. These types of sensors can be found in machining and manufacturing facilities around the world.
Basic capacitive theory.
Capacitance is an electrical property which is created by applying an electrical charge to two conductive objects with a gap between them. A simple demonstration is two parallel conductive plates of the same profile with a gap between them and a charge applied to them. In this situation, the Capacitance can be expressed by the equation:
Where "C" is the capacitance, ε0 is the permittivity of free space constant, "K" is the dielectric constant of the material in the gap, "A" is the area of the plates, and "d" is the distance between the plates.
There are two general types of capacitive displacement sensing systems. One type is used to measure thicknesses of conductive materials. The other type measures thicknesses of non conductive materials or the level of a fluid.
A capacitive sensing system for conductive materials uses a model similar to the one described above, but in place of one of the conductive plates, is the sensor, and in place of the other, is the conductive target to be measured. Since the area of the probe and target remain constant, and the dielectric of the material in the gap (usually air) also remains constant, "any change in capacitance is a result of a change in the distance between the probe and the target." Therefore, the equation above can be simplified to:
Where α indicates a proportional relationship.
Due to this proportional relationship, a capacitive sensing system is able to measure changes in capacitance and translate these changes in distance measurements.
The operation of the sensor for measuring thickness of non-conductive materials can be thought of as two capacitors in series, with each having a different dielectric (and dielectric constant). The sum of the thicknesses of the two dielectric materials remains constant but the thickness of each can vary. The thickness of the material to be measured displaces the other dielectric. The gap is often an air gap, (dielectric constant = 1) and the material has a higher dielectric. As the material gets thicker, the capacitance increases and is sensed by the system.
A sensor for measuring fluid levels works as two capacitors in parallel with constant total area. Again the difference in the dielectric constant of the fluid and the dielectric constant of air results in detectable changes in the capacitance between the conductive probes or plates.
Applications.
Precision positioning.
One of the more common applications of capacitive sensors is for precision positioning. Capacitive displacement sensors can be used to measure the position of objects down to the nanometer level. This type of precise positioning is used in the semiconductor industry where silicon wafers need to be positioned for exposure. Capacitive sensors are also used to pre-focus the electron microscopes used in testing and examining the wafers.
Disc drive industry.
In the disc drive industry, capacitive displacement sensors are used to measure the runout (a measure of how much the axis of rotation deviates from an ideal fixed line) of disc drive spindles. By knowing the exact runout of these spindles, disc drive manufacturers are able to determine the maximum amount of data that can be placed onto the drives. Capacitive sensors are also used to ensure that disc drive platters are orthogonal to the spindle before data is written to them.
Precision thickness measurements.
Capacitive displacement sensors can be used to make very precise thickness measurements. Capacitive displacement sensors operate by measuring changes in position. If the position of a reference part of known thickness is measured, other parts can be subsequently measured and the differences in position can be used to determine the thickness of these parts. In order for this to be effective using a single probe, the parts must be completely flat and measured on a perfectly flat surface. If the part to be measured has any curvature or deformity, or simply does not rest firmly against the flat surface, the distance between the part to be measured and the surface it is placed upon will be erroneously included in the thickness measurement. This error can be eliminated by using two capacitive sensors to measure a single part. Capacitive sensors are placed on either side of the part to be measured. By measuring the parts from both sides, curvature and deformities are taken into account in the measurement and their effects are not included in the thickness readings.
The thickness of plastic materials can be measured with the material placed between two electrodes a set distance apart. These form a type of capacitor. The plastic when placed between the electrodes acts as a dielectric and displaces air (which has dielectric constant of 1, different from the plastic). Consequently, the capacitance between the electrodes changes. The capacitance changes can then be measured and correlated with the material's thickness.
Capacitive sensors circuits can be constructed that are able to detect changes in capacitance on the order of a 10−5 picofarads (10 attofarads).
Non-conductive targets.
While capacitive displacement sensors are most often used to sense changes in position of conductive targets, they can also be used to sense the thickness and/or density of non-conductive targets as well. A non-conductive object placed in between the probe and conductive target will have a different dielectric constant than the air in the gap and will therefore change the Capacitance between probe and target. (See the first equation above) By analyzing this change in capacitance, the thickness and density of the non-conductor can be determined.
Machine tool metrology.
Capacitive displacement sensors are often used in metrology applications. In many cases, sensors are used “to measure shape errors in the part being produced. But they also can measure the errors arising in the equipment used to manufacture the part, a practice known as machine tool metrology”. In many cases, the sensors are used to analyze and optimize the rotation of spindles in various machine tools, examples include surface grinders, lathes, milling machines, and air bearing spindles. By measuring errors in the machines themselves, rather than simply measuring errors in the final products, problems can be dealt with and fixed earlier in the manufacturing process.
Assembly line testing.
Capacitive displacement sensors are often used in assembly line testing. Sometimes they are used to test assembled parts for uniformity, thickness or other design features. At other times, they are used to simply look for the presence or absence of a certain component, such as glue. Using capacitive sensors to test assembly line parts can help to prevent quality concerns further along in the production process.
Comparison to eddy current displacement sensors.
Capacitive displacement sensors share many similarities to eddy current (or inductive) displacement sensors; however capacitive sensors use an electric field as opposed to the magnetic field used by eddy current sensors This leads to a variety of differences between the two sensing technologies, with the most notable differences being that capacitive sensors are generally capable of higher resolution measurements, and eddy current sensors work in dirty environments while capacitive sensors do not.


Power electronic substrate

The role of the substrate in power electronics is to provide the interconnections to form an electric circuit (like a printed circuit board), and to cool the components. Compared to materials and techniques used in lower power microelectronics, these substrates must carry higher currents and provide a higher voltage isolation (up to several thousand volts). They also must operate over a wide temperature range (up to 150 or 200 °C).
Direct Bonded Copper (DBC) substrate.
DBC substrates are commonly used in power modules, because of their very good thermal conductivity. They are composed of a ceramic material tile with a sheet of copper bonded to one or both sides by a high-temperature oxidation process (the copper and substrate are heated to a carefully controlled temperature in an atmosphere of nitrogen containing about 30 ppm of oxygen; under these conditions, a copper-oxygen eutectic forms which bonds successfully both to copper and the oxides used as substrates). The top copper layer can be preformed prior to firing or chemically etched using printed circuit board technology to form an electrical circuit, while the bottom copper layer is usually kept plain. The substrate is attached to a heat spreader by soldering the bottom copper layer to it.
A related technique uses a seed layer, photoimaging, and then additional copper plating to allow for fine lines (as small as 50 micrometres) and through-vias to connect front and back sides. This can be combined with polymer-based circuits to create high density substrates that eliminate the need for direct connection of power devices to heat sinks.
One of the main advantages of the DBC vs other power electronic substrates is their low coefficient of thermal expansion, which is close to that of silicon (compared to pure copper). This ensures good thermal cycling performances (up to 50,000 cycles). The DBC substrates also have excellent electrical insulation and good heat spreading characteristics.
Ceramic material used in DBC include:
Active Metal Brazed (AMB) substrate.
AMB consists of a metal foil soldered to the ceramic baseplate using solder paste and high temperature (800 °C – 1000 °C) under vacuum. Although AMB is electrically very similar to DBC, it is typically suited for small production lots due to the unique process requirements.
Insulated Metal substrate (IMS).
IMS consists of a metal baseplate (aluminium is commonly used because of its low cost and density) covered by a thin layer of dielectric (usually an epoxy-based layer) and a layer of copper (35 μm to more than 200 μm thick). The FR-4-based dielectric is usually thin (about 100 μm) because it has poor thermal conductivity compared to the ceramics used in DBC substrates.
Due to its structure, the IMS is a single-sided substrate, i.e. it can only accommodate components on the copper side. In most applications, the baseplate is attached to a heatsink to provide cooling, usually using thermal grease and screws. Some IMS substrates are available with a copper baseplate for better thermal performances.
Compared to a classical printed circuit board, the IMS provides a better heat dissipation. It is one of the simplest ways to provide efficient cooling to surface mount components.


LSP Technologies

LSP Technologies, Inc. (also known as LSPT) located in Dublin, Ohio. The company provides laser peening surface enhancement services and equipment, and other laser technologies.
History.
The company founder, "Jeff Dulaney", earned his Ph.D. in Physics at the University of Pittsburgh in 1986, then worked at Battelle Columbus Laboratory from 1987 to 1994 as a physicist in the laser department. He helped design and build the first industrial laser shock peening system for "Wagner Laser Technologies" in the early 1990s. Dr. Dulaney acquired Battelle’s laser shock peening patent rights and formed LSP Technologies, Inc. in February 1995. "Dr. Allan Clauer", an original patent holder of the laser peening process, and a Battelle inventor of the laser shock peening process, joined LSPT as Vice-President later in 1995.
In 1996 to 1999, LSPT assembled and delivered three high power ND: Glass laser peening systems to General Electric Aviation in Cincinnati, Ohio. LSPT also won several Small Business Innovation Research (SBIR) awards for laser peening, laser bond inspection, and laser land mine neutralization. In March 2003 LSPT began production laser peen processing on 4th stage IBR in Pratt & Whitney’s F119 engine for the F-22 Raptor. In 2009 LSPT began laser peening production services for power generation and forging industries. In 2012, LSPT delivered a laser bond inspection system to the Boeing Company in Seattle, WA.
LSPT is an AS9100 certified company for Laser Processing Services and Equipment Design.
Inventions.
LSPT holds over 54 patents in laser peening, and many more on laser bond inspection and laser applications.


Disc cutter

A disc cutter is a specialised, often hand-held, power tool used for cutting hard materials, ceramic tile, metal, concrete, and stone for example. This tool is very similar to an angle grinder, chop saw, or even a die grinder, with the main difference being the cutting disc itself (a circular diamond blade, or resin-bonded abrasive cutting wheel for a disc cutter vs. an abrasive grinding wheel for an angle grinder). This tool is highly efficient at cutting very hard materials, especially when compared to hand tools.
Discs.
Often cutting discs, also known as cut-off wheels, are made from a solid abrasive disc. These discs are often used for cutting metal; they are composed of an abrasive mix of grit and adhesive that is formed into a thin, rigid disc with fiber webbing running through it for strength. Some discs used for cutting ceramic tile or stone are made from a solid disc with an edge coated with diamond grit. The most common size for these cutting wheels is inches in diameter; however they can range from 2 to 16 inches in diameter with a thickness range from .045 in. to .125 in. Type 1 discs are flat, and type 27 discs have a raised hub. These wheels are strong but are not immune to breaking. If a cutting wheel breaks while in use, fragments could injure the operator or nearby co-workers. To avoid breaking cutting discs, never exceed the maximum speed (RPM) specified on the disc, and do not overload the disc by cutting with excess force or jamming the wheel into your workpiece.
Applications.
Many manual cutting tasks require a hand-held grinder using a cutting wheel. Metal fabrication is one of the most common uses for cutting wheels. Cutting sheet metal, sizing metal stock for welding, cutting a weld to re-weld it, and cutting and notching steel pipe are just a few examples. Die grinders and chop saws are other common tools used with cutting discs.
Smaller projects and smaller or more precise cuts may require a die grinder equipped with a cutting wheel. These cutting wheels or discs are extremely thin and often less than 2 inches in diameter. Because they are so thin, they are commonly made of metal and have a diamond-coated edge as the abrasive. This type of disc cutter is good for sheet metal and for lightweight or thin materials. Thicker or heavier materials will need a larger disc cutter.
For long straight cuts on sheet metal or for light cut-off work, a standard circular saw is used with a -inch cutting wheel. These cutting discs are made just like the smaller wheels of an angle grinder, with resin bonded abrasive material, or are of metal with a diamond-coated edge.
A cutoff saw is used for cutting larger items, like heavy metal stock, metal studs, and for cutting large metal pipe. The cutting discs for this tool are usually 10 or 12 inches in diameter, with a composition like that of the smaller wheels mentioned above. When cutting heavy materials the cutting discs may require lubrication or coolant to prevent overheating. The cutoff saw is for making clean straight 90 degree cuts through the material.


BOD bottle

BOD Bottle or an incubation bottle is a main apparatus used for the Biological Oxygen Demand (BOD) test. During the five-day BOD or BOD5 test process, the BOD bottle is used for incubating diluted samples under the 20 °C or 68 °F of temperature.
Structure.
The bottle is normally designed to have a special shoulder radius to push out all air from the inside of the bottle when a sample solution is being filled. According to Method 5210 in "Standard Methods for the Examination of Water and Wastewater", the BOD bottle should include a ground-glass stopper and a flared mouth which form a water seal preventing the air from the outside of the bottle coming in. Method 5210 also recommends to use a paper, a foil or a plastic cup to cap over the mouth of the bottle reducing the evaporation during the incubation. Generally, the side of the BOD bottle is permanently screened with white writing area, and is printed with a specific number; both for the aid of the sample identification.
There are two kinds of stopper: the Glass Pennyhead and the Glass Robotic stopper.
There are many BOD bottle sizes. The dose of the mixture of the solution (nutrient, mineral and buffer solution) is related to the size of the bottle. For the Standard Methods 5210, the BOD bottle “having 60 mL or greater capacity (300-mL)” is mentioned as one of the apparatus for the BOD test. A 60 mL BOD bottle is available and listed as "often convenient" by EPA (Environmental Protection Agency) Method 405.1. However, EPA Method 405.1 was written in 1974 and is no longer an EPA-approved method per 40CFR Part 136.
Materials.
Glass is a material being specified in the Standard Methods 5210 of the BOD5 test. The glass bottles are manufactured from Type 1 borosilicate glass.
A black BOD bottle is coated with PVC plastic that blocks visible light. Black bottles are used in marine photosynthesis projects which needs to compare oxygen levels in light and dark conditions.
It is a carbon-coated polyethylene terephthalate (PET) bottle that is solely manufactured by Environmental Express in Charleston, SC. The bottle is lightweight, unbreakable, and recyclable. Since the bottle is designed for single-use, it eliminates any potential for cross-contamination between samples. The bottle does not require any resources nor energy for cleaning and rinsing as it is disposable. CBOD bottle is also claimed to be cheaper, and cause less contamination in the sample solution than the conventional- BOD bottle.


National Production Authority

The National Production Authority (NPA) was an agency of the United States government which developed and promoted the production and supply of materials and facilities necessary for defense mobilization. It was part of the Department of Commerce.
The agency was created by Department Order 123, issued September 11, 1950, under authority of the Defense Production Act of 1950 and Executive Order 10161 (issued September 9, 1950). The organization's function was to ensure the needs of the civilian economy were adequately represented in defense mobilization efforts, and that small businesses were participating in defense contracts.
In 1951, after the escalation of the Korean War, the NPA was placed under the control of the Defense Production Administration in the Office of Defense Mobilization.
The NPA was abolished by Department Order 152, issued October 1, 1953. Its functions were dispersed among a number of successor agencies, including the Business and Defense Services Administration (1953–1970); the Bureau of Domestic Commerce (1970–1972); the Domestic and International Business Administration (1972–1977); the Industry and Trade Administration (1977–1980); and the International Trade Administration (1980–present).


Sterling Armaments Company

The Sterling Engineering Company Ltd was an arms manufacturer based in Dagenham, famous for manufacturing the Sterling submachine gun (L2A3), ArmaLite AR-18 and Sterling SAR-87 assault rifles and parts of Jaguar cars. The company went bankrupt in 1988.
During World War II, engineers George Lanchester and George William Patchett oversaw the manufacture of the Lanchester submachine gun. Patchett afterwards went on to design the Patchett machine carbine which, after a competitive trial in 1947, was adopted by the British Army in 1953 as the L2A1 Sterling submachine gun, replacing the Sten gun. The weapon was later upgraded to the L2A3, the Sterling Mk IV.
The Sterling brand name was revived in 2016 by James Edmiston, a former director of the original company. It is however a dormant company, according to accounts filed with Companies House, with no stated plans to do any business beyond engraving services.


Wright Cadet

The Wright Cadet was a low floor midibus body built on the DAF/VDL SB120 chassis by Wrightbus between 2000 and 2006. It was sold via VDL dealer Arriva Bus & Coach. Of the 681 produced, 366 were for Arriva subsidiaries including eight for its Netherlands subsidiary. Bus Éireann purchased 35.
Volvo Merit.
The SB120/Cadet combination was also sold through Volvo Buses for a time following the withdrawal from sale of its own B6BLE chassis in 2002 without a direct replacement. Cadets sold through Volvo were marketed as the Volvo Merit, although they were identical to Cadets sold through Wrightbus.


List of semiconductor fabrication plants

This is a list of semiconductor fabrication plants. A semiconductor fabrication plant is where integrated circuits (ICs), also known as microchips, are manufactured. They are either operated by Integrated Device Manufacturers (IDMs) who design and manufacture ICs in-house and may also manufacture designs from design-only (fabless firms), or by pure play foundries who manufacture designs from fabless companies and do not design their own ICs. Some pure play foundries like TSMC offer IC design services, and others, like Samsung, design and manufacture ICs for customers, while also designing, manufacturing and selling their own ICs.
Open plants.
Operating fabs include:
Number of open fabs currently listed here:
Closed plants.
Number of closed fabs currently listed here:
References.
Samsung capacity


Operational maintenance

Operational maintenance is the care and minor maintenance of equipment using procedures that do not require detailed technical knowledge of the equipment’s or system’s function and design. This category of operational maintenance normally consists of inspecting, cleaning, servicing, preserving, lubricating, and adjusting, as required. Such maintenance may also include minor parts replacement that does not require the person performing the work to have highly technical skills or to perform internal alignment.
As the term implies, operational maintenance, is performed by the operator of the equipment. Its purpose is threefold: (1) to make the operator aware of the state of readiness of the equipment; (2) to reduce the delays that would occur if a qualified technician had to be called every time a simple adjustment were needed; and (3) to release technicians for more complicated work
This form of preventative maintenance can be performed in any setting where machines, equipment, or vehicles are used. This may include manufacturing plants and factories, as well as automotive shops. In many commercial buildings, heating and cooling engineers perform operational maintenance tasks on furnaces, boilers, and air conditioners.
Some operational maintenance responsibilities can be as simple as inspecting the machine to spot any changes or issues. This allows the operator to detect a potential danger, such as loose fasteners or debris that could contribute to an accident. Basic cleaning, including removing debris or excess grease from a machine, is also considered part of operational maintenance.
Depending on the type of equipment in use, operators may also be responsible for replacing worn out filters or cartridges, or removing and replacing a worn belt, cutting tool, or grinding stone. Operational maintenance may entail keeping machinery well lubricated to reduce the risk of friction or failure. Many basic machine adjustments needed during the course of operation also fall within this category of preventative maintenance.


Interference fit

An interference fit, also known as a pressed fit or friction fit, is a form of fastening between two tightfitting mating parts that produces a joint which is held together by friction after the parts are pushed together.
Depending on the amount of interference, parts may be joined using a tap from a hammer or "pressed" together using a hydraulic ram. Critical components that must not sustain damage during joining may also be cooled significantly below room temperature to shrink one of the components before fitting. This method allows the components to be joined without force and produces a shrink fit interference when the component returns to normal temperature. Interference fits are commonly used with aircraft fasteners to improve the fatigue life of a joint.
Introducing interference between parts.
These fits, though applicable to shaft and hole assembly, are more often used for bearing-housing or bearing-shaft assembly. This is referred to as a 'press-in' mounting.
Tightness of fit.
The tightness of fit is controlled by amount of interference; the allowance (planned difference from nominal size). Formulas exist to compute allowance that will result in various strengths of fit such as loose fit, light interference fit, and interference fit. The value of the allowance depends on which material is being used, how big the parts are, and what degree of tightness is desired. Such values have already been worked out in the past for many standard applications, and they are available to engineers in the form of tables, obviating the need for re-derivation.
As an example, a shaft made of 303 stainless steel will form a tight fit with allowance of . A slip fit can be formed when the bore diameter is wider than the rod; or, if the rod is made 12–20μm under the given bore diameter.
An example:
The allowance per inch of diameter usually ranges from (0.1–0.25%), (0.15%) being a fair average. Ordinarily the allowance per inch decreases as the diameter increases; thus the total allowance for a diameter of might be , 0.2%), whereas for a diameter of the total allowance might not be over i.e., 0.11–0.12%). The parts to be assembled by forced fits are usually made cylindrical, although sometimes they are slightly tapered. Advantages of the taper form are: the possibility of abrasion of the fitted surfaces is reduced; less pressure is required in assembling; and parts are more readily separated when renewal is required. On the other hand, the taper fit is less reliable, because if it loosens, the entire fit is free with but little axial movement. Some lubricant, such as white lead and lard oil mixed to the consistency of paint, should be applied to the pin and bore before assembling, to reduce the tendency toward abrasion.
Assembling.
There are two basic methods for assembling an oversize shaft into an undersized hole, sometimes used in combination: force and thermal expansion or contraction.
Force.
There are at least three different terms used to describe an interference fit created via force: press fit, friction fit, and hydraulic dilation.
Press fit is achieved with presses that can press the parts together with very large amounts of force. The presses are generally hydraulic, although small hand-operated presses (such as arbor presses) may operate by means of the mechanical advantage supplied by a jackscrew or by a gear reduction driving a rack and pinion. The amount of force applied in hydraulic presses may be anything from a few pounds for the tiniest parts to hundreds of tons for the largest parts.
The edges of shafts and holes are chamfered (beveled). The chamfer forms a guide for the pressing movement, helping to distribute the force evenly around the circumference of the hole, to allow the compression to occur gradually instead of all at once, thus helping the pressing operation to be smoother, to be more easily controlled, and to require less power (less force at any one instant of time), and to assist in aligning the shaft parallel with the hole it is being pressed into. In the case of train wheelsets the wheels are pressed onto the axles by force.
Thermal expansion or contraction.
Most materials expand when heated and shrink when cooled. Enveloping parts are heated (e.g., with torches or gas ovens) and assembled into position while hot, then allowed to cool and contract back to their former size, except for the compression that results from each interfering with the other. This is also referred to as shrink-fitting. Railroad axles, wheels, and tires are typically assembled in this way. Alternatively, the enveloped part may be cooled before assembly such that it slides easily into its mating part. Upon warming, it expands and interferes. Cooling is often preferable as it is less likely than heating to change material properties, e.g., assembling a hardened gear onto a shaft, where the risk exists of heating the gear too much and drawing its temper.