Modified atmosphere

Modified atmosphere packaging (MAP) is the practice of modifying the composition of the internal atmosphere of a package (commonly food packages, drugs, etc.) in order to improve the shelf life. The need for this technology for food arises from the short shelf life of food products such as meat, fish, poultry, and dairy in the presence of oxygen. In food, oxygen is readily available for lipid oxidation reactions. Oxygen also helps maintain high respiration rates of fresh produce, which contribute to shortened shelf life. From a microbiological aspect, oxygen encourages the growth of aerobic spoilage microorganisms. Therefore, the reduction of oxygen and its replacement with other gases can reduce or delay oxidation reactions and microbiological spoilage. Oxygen scavengers may also be used to reduce browning due to lipid oxidation by halting the auto-oxidative chemical process. Besides, MAP changes the gaseous atmosphere by incorporating different compositions of gases.
The modification process generally lowers the amount of oxygen (O2) in the headspace of the package. Oxygen can be replaced with nitrogen (N2), a comparatively inert gas, or carbon dioxide (CO2).
A stable atmosphere of gases inside the packaging can be achieved using active techniques, such as gas flushing and compensated vacuum, or passively by designing “breathable” films.
History.
The first recorded beneficial effects of using modified atmosphere date back to 1821. Jacques Étienne Bérard, a professor at the School of Pharmacy in Montpellier, France, reported delayed ripening of fruit and increased shelf life in low-oxygen storage conditions. Controlled atmosphere storage (CAS) was used from the 1930s when ships transporting fresh apples and pears had high levels of CO2 in their holding rooms in order to increase the shelf life of the product. In the 1970s MA packages reached the stores when bacon and fish were sold in retail packs in Mexico. Since then development has been continuous and interest in MAP has grown due to consumer demand.
Theory.
Atmosphere within the package can be modified passively or actively. In passive MAP, the high concentration of CO2 and low O2 levels in the package is achieved over time as a result of respiration of the product and gas transmission rates of the packaging film. This method is commonly used for fresh respiring fruits and vegetables. Reducing O2 and increasing CO2 slows down respiration rate, conserves stored energy, and therefore extended shelf life. On the other hand, active MA involves the use of active systems such as O2 and CO2 scavengers or emitters, moisture absorbers, ethylene scavengers, ethanol emitters and gas flushing in the packaging film or container to modify the atmosphere within the package.
The mixture of gases selected for a MA package depends on the type of product, the packaging materials and the storage temperature. The atmosphere in an MA package consists mainly of adjusted amounts of N2, O2, and CO2. Reduction of O2 promotes delay in deteriorative reactions in foods such as lipid oxidation, browning reactions and growth of spoilage organisms. Low O2 levels of 3-5% are used to slow down respiration rate in fruits and vegetables. In the case of red meat, however, high levels of O2 (~80%) are used to reduce oxidation of myoglobin and maintain an attractive bright red color of the meat. Meat color enhancement is not required for pork, poultry and cooked meats; therefore, a higher concentration of CO2 is used to extend the shelf life. Levels higher than 10% of CO2 are phytotoxic for fruit and vegetables, so CO2 is maintained below this level. N2 is mostly used as a filler gas to prevent pack collapse. In addition, it is also used to prevent oxidative rancidity in packaged products such as snack foods by displacing atmospheric air, especially oxygen, therefore extending shelf life. The use of noble gases such as helium (He), argon (Ar) and xenon (Xe) to replace N2 as the balancing gas in MAP can also be used to preserve and extend the shelf life of fresh and minimally processed fruits and vegetables. Their beneficial effects are due to their higher solubility and diffusivity in water, making them more effective in displacing O2 from cellular sites and enzymatic O2 receptors.
There has been a debate regarding the use of carbon monoxide (CO) in the packaging of red meat due to its possible toxic effect on packaging workers. Its use results in a more stable red color of carboxymyoglobin in meat, which leads to another concern that it can mask evidence of spoilage in the product.
Effect on microorganisms.
Low O2 and high CO2 concentrations in packages are effective in limiting the growth of Gram negative bacteria, molds and aerobic microorganisms, such as "Pseudomonas" spp. High O2 combined with high CO2 could have bacteriostatic and bactericidal effects by suppression of aerobes by high CO2 and anaerobes by high O2. CO2 has the ability to penetrate bacterial membrane and affect intracellular pH. Therefore, lag phase and generation time of spoilage microorganisms are increased resulting in shelf life extension of refrigerated foods. Since the growth of spoilage microorganisms are suppressed by MAP, the ability of the pathogens to grow is potentially increased. Microorganisms that can survive under low oxygen environment such as "Campylobacter jejuni", "Clostridium botulinum", "E. coli", "Salmonella", "Listeria" and "Aeromonas hydrophila" are of major concern for MA packaged products. Products may appear organoleptically acceptable due to the delayed growth of the spoilage microorganisms but might contain harmful pathogens. This risk can be minimized by use of additional hurdles such as temperature control (maintain temperature below 3 degrees C), lowering water activity (less than 0.92), reducing pH (below 4.5) or addition of preservatives such as nitrite to delay metabolic activity and growth of pathogens.
Packaging materials.
Flexible films are commonly used for products such as fresh produce, meats, fish and bread seeing as they provide suitable permeability for gases and water vapor to reach the desired atmosphere. Pre-formed trays are formed and sent to the food packaging facility where they are filled. The package headspace then undergoes modification and sealing. Pre-formed trays are usually more flexible and allow for a broader range of sizes as opposed to thermoformed packaging materials as different tray sizes and colors can be handled without the risk of damaging the package. Thermoformed packaging however is received in the food packaging facility as a roll of sheets. Each sheet is subjected to heat and pressure, and is formed at the packaging station. Following the forming, the package is filled with the product, and then sealed. The advantages that thermoformed packaging materials have over pre-formed trays are mainly cost-related: thermoformed packaging uses 30% to 50% less material, and they are transported as rolls of material. This will amount in significant reduction of manufacturing and transportation costs.
When selecting packaging films for MAP of fruits and vegetables the main characteristics to consider are gas permeability, water vapor transmission rate, mechanical properties, transparency, type of package and sealing reliability. Traditionally used packaging films like LDPE (low-density polyethylene), PVC (polyvinyl chloride), EVA (ethylene-vinyl acetate) and OPP (oriented polypropylene) are not permeable enough for highly respiring products like fresh-cut produce, mushrooms and broccoli. As fruits and vegetables are respiring products, there is a need to transmit gases through the film. Films designed with these properties are called permeable films. Other films, called barrier films, are designed to prevent the exchange of gases and are mainly used with non-respiring products like meat and fish.
MAP films developed to control the humidity level as well as the gas composition in the sealed package are beneficial for the prolonged storage of fresh fruits, vegetables and herbs that are sensitive to moisture. These films are commonly referred to as modified atmosphere/modified humidity packaging (MA/MH) films.
Equipment.
In using form-fill-seal packaging machines, the main function is to place the product in a flexible pouch suitable for the desired characteristics of the final product. These pouches can either be pre-formed or thermoformed. The food is introduced into the pouch, the composition of the headspace atmosphere is changed within the package; it is then heat sealed. These types of machines are typically called pillow-wrap, which horizontally or vertically form, fill and seal the product. Form-fill-seal packaging machines are usually used for large scale operations.
In contrast, chamber machines are used for batch processes. A filled pre-formed wrap is filled with the product and introduced into a cavity. The cavity is closed and vacuum is then pulled on the chamber and the modified atmosphere is inserted as desired. Sealing of the package is done through heated sealing bars, and the product is then removed. This batch process is labor-intensive and thus requires a longer period of time; however, it is relatively cheaper than packaging machines which are automated.
Additionally, snorkel machines are used to modify the atmosphere within a package after the food has been filled. The product is placed in the packaging material and positioned into the machine without the need of a chamber. A nozzle, which is the snorkel, is then inserted into the packaging material. It pulls a vacuum and then flushes the modified atmosphere into the package. The nozzle is removed and the package is heat sealed. This method is suitable for bulk and large operations.
Products.
Many products such as red meat, seafood, minimally processed fruits and vegetables, salads, pasta, cheese, bakery goods, poultry, cooked and cured meats, ready meals and dried foods are packaged under MA. A summary of optimal gas mixtures for MA products is shown in the following table.
Modified Atmosphere Packaging for different food products and optimal gas mixtures


Punch down tool

A punch down tool, punchdown tool, IDC tool, or a Krone tool (named after the Krone LSA-PLUS connector), is a small hand tool used by telecommunication and network technicians. It is used for inserting wire into insulation-displacement connectors on punch down blocks, patch panels, keystone modules, and surface mount boxes (also known as biscuit jacks).
Description and use.
Most punch down tools are of the impact type, consisting of a handle, an internal spring mechanism, and a removable slotted blade. To use the punch down tool, a wire is pre-positioned into a slotted post on a punch block, and then the punch down tool is pressed down on top of the wire, over the post. Once the required pressure is reached, an internal spring is triggered, and the blade pushes the wire into the slot, simultaneously cutting the insulation and securing the wire. The tool blade does not cut through the wire insulation to make contact, but rather the sharp edges of the slot in the contact post itself slice through the insulation.
However, the punch down tool blade also is usually used to cut off excess wire, in the same operation as making the connection; this is done with a sharp edge of the punch down tool blade trapping the wire to be cut against the plastic punch block. If this cutoff feature is heavily used, the tool blade must be resharpened or replaced from time to time. Tool blades without the sharp edge are also available; these are used for continuing a wire through a slotted post to make connections with another slotted post ("daisy-chained" wiring).
For light-duty use, there are also less-expensive punch down tools with fixed blades and no impact mechanism. These low-cost tools are more time-consuming for making reliable connections, and can cause muscle fatigue when used for large numbers of connections.
To accommodate different connector types, 66, 110, BIX and krone blocks require different blades. Removable blades for 66 or 110 are almost always double-ended. Some blades have one end that only inserts the wire for daisy-chain wiring from post to post, and another end that inserts wire and trims the excess length for termination at a post. Other blades have a cutting 66 blade on one end and a cutting 110 blade on the other. Krone blades require a separate scissor-like mechanism for trimming the wire.


Trailer brake controller

A brake controller is usually an original equipment manufacturer or aftermarket-installed device or module. It is mounted to the tow vehicle's driver's-side dashboard area, and engages a trailer's electrical braking system either time delayed, or in proportion to the tow vehicle's brake engagement when slowing down or coming to a halt. A brake controller is not needed with a trailer surge braking system unless using modern electric over hydraulic devices. The trailer in this case usually has either electric friction brakes or electric-hydraulic trailer brake actuators.
Most basic brake controllers will generally have a plus-minus gain adjustment. The tow vehicle operator sets the gain as high as possible but without the trailer brakes locking up after making a few test stops. The heavier the trailer, the higher the gain adjustment is set and therefore the less chances of wheel lock-up.
A wide range of trailers contain trailer brakes (for example, larger boat trailers, horse trailers, covered utility trailers, enclosed trailers, travel trailers including small and longer tent trailers and car carriers). Smaller trailers may not contain trailer brakes (for example, basic utility trailers). It is recommended that, if the total trailer weight is over a couple thousand kilograms, the trailer have some sort of braking system, and the tow vehicle be equipped with a brake controller.
Types.
There are different types of brake controllers currently or previously on the market.
Air-actuated electric brake controller.
This controller uses the air pressure of the brake system on a vehicle with pneumatic brakes to provide a current to control the electric brakes of a trailer.
Hydraulic actuated electric controller.
This controller uses the hydraulic pressure of the brake system on a vehicle with hydraulic brakes to provide a current to control the electric brakes of a trailer. Some truck manufacturers offers this as an OEM option, like Ford with its Ford TowCommand.
Pedal-mounted pressure pad proportional controller.
A separate sensor is mounted on the brake pedal to connect to the controller.
Proportional brake controller.
Senses the deceleration of the vehicle through a pendulum or similar device to apply a suitable current for braking of the trailer.
Surge brake.
When the tow vehicle slows down the trailer pushes against it, an actuator applies force to its master cylinder and the hydraulic pressure is transferred to the brakes
Time-delayed brake controller.
Applies brake current with a ramp-up over time to a certain level set by the driver.


CNC plunge milling

CNC plunge milling, also called z-axis milling, is a CNC milling process. In this process, the feed is provided linearly along the tool axis while doing CNC processing.
Plunge milling is effective for the rough machining process of complex shape or free form shapes like impeller parts. In multi axis plunge milling, the optimization of plunge cutter section selection and generating the tool path for free form surface is very important to improve the efficiency and effectiveness.
In plunge milling, after each plunge the milling cutter is offset by some value and then the material surface is removed in the form of lunula. The material removal rate is computed by area of lunula and the feed rate. At the entry and exit of milling cutter, the radial offset has not any influence on the condition of surface.
At the maximum cutting velocity, the surface obtained is clean whatever the feed rate per tooth on entry but on exit the high value of feed rate gives the deteriorated surface. The surface roughness value always increases with feed rate in plunge milling. The simulation of dynamic uncut chip thickness which is generated by plunge milling can be done by tracking the position of plunge cutter center. This simulation shows the regenerative effect with variation of phase difference.
Then the model of uncut chip thickness and cutting force coefficient with cutting edge radius are entered into time domain model. Finally, with the help of time domain solution the stability of machine and vibrations are estimated.
The cutting parameters play a key role in plunge milling. The cutting force and machine stability both are influenced by machining parameters. Frequency domain model can be used to estimate the machining stability.
Advantages of CNC plunge milling.
The plunge milling has following advantage over conventional milling-


Freeform surface machining

Freeform surface or complex surfaces are widely manufactured nowadays. The industries which most often manufactures free-form surfaces are basically aerospace, automotive, die mold industries, bio medical and power sector for turbine blades manufacturing. Generally 3 or 5 axis CNC milling machine is used for this purpose. The manufacturing process of free form surface is not an easy job as the tool path generation in present CAM technology is generally based on geometric computation so tool path are not optimum. The geometry can also be not described explicitly so errors and discontinuities occurrence in the solid structure cannot be avoided. Free-form surfaces are machined with the help of different tool path generation method like adaptive iso-planar tool path generation, constant scallop tool path generation, adaptive iso-parametric method, iso-curvature, isophote and by other methods. The different methods are chosen based on the parameters which is needed to be optimized.
Optimization of free-form surface machining.
CAM software generally creates a tool path without considering any mechanics process. These causes risk of tool damage, tool deflection and errors on surface finish. By minimizing the forces we can increase tool life. Different optimization method can be used considering process parameters like feed rate, spindle speed, steps, tool diameter, magnitude and preset maximum force. The optimization can be done for minimum machining time, minimum tool travel, minimum production cost or for good surface finish. Efficiency of surface machined is also considered by maximum scallop height and by gouging. Gouging are the main reason for discrepancies of surface accuracy and texture specification. It also causes damage to part,s surface and machine tool. Scallop height tolerance help us in measuring the quality of free-form surface. Selection of proper topology result in minimum path length. In CAM software choosing NURBS to create surface is considered to be good method for presenting surface as it is accepted by both IGES and STEP files of CAM software.


CNC riveting

CNC riveting is a CNC process used for obtaining permanent mechanical fastening of geometrical shapes, ranging from simple to complex shapes, such as aircraft fuselages. This is done in a shorter duration of time with a high riveting rate. The process is fast, robust, and is flexible in nature; thus improving its usage and providing reliability to the riveted joint along with the final product quality. CNC riveting can be used for a variety of operations ranging from riveting and fastening belts, skin panels, shear ties, and other internal fuselage components.
The CNC Riveting machines generally consist of a solid frame made of welded steel and aluminum frames used for protection fitted with polycarbonate panes. The dynamic drive of the coordinates axes is achieved by a recirculating ball and screw, servo motors and motion control units that make the high-speed movement possible. For the mounting of the riveting units, solid C Frames are used. The riveting program can be given various parameters and these can be changed or altered as desired to be CNC programs as per the requirement.
CNC riveting machine variants.
CNC duct riveting cell.
A CNC controlled automatic riveting work cell with a knee type design drill machine that has sixty-inch throat depth with four positions on the upper head. This machine can apply sixteen pounds of upset force. This machine is equipped with dual drill spindles, one for carrying out drilling and other for deburring. It was developed for the fabrication of tubular assemblies, which are fed into the throat of the machine over an eight-inch square lower knee. The CNC controlled four axis positioning system presents the part to the machine that carries out the riveting.
CNC riveting machines with stationary machine table.
These CNC machines act as stand-alone workstations for heavy and bigger workpieces. They are simple in design and require work holding fixtures only, so the clamping and component query devices are much more affordable.
CNC riveting machines with Indexing Tables.
These special purpose CNC riveting machines have different sizes of indexing tables that be composed of different coordinate axes and riveting machines. These machines have different versions for the particular application and are configured accordingly. The coordinate system has linear units and recirculating ball screws, and an index table that is electrically operated with a brake motor. It has two to four fixed indexing stations, and the index table are NC flexible rotary indexing tables which are actuated by two hand controls or by a pedal switch. The machine has an automatic tool changer.
CNC riveting machines with transfer system.
These CNC riveting machines are made for use in manufacturing lines. The fixtures are coded and interfaces are customized to make the connection of several CNC riveting machines and linking them with other manufacturing systems, making it possible to obtain a high degree of automation.
Multiple axes CNC riveting cell.
This is the latest technological development in automated fastening. This technology is versatile and can be used for riveting of high curvature fuselage panels to low curvature wing panels, bulkheads, floor etc. The tooling changeover is minimized thus part throughput is maximized.
Advantages.
The main advantages of this type of CNC riveting machine are that it can use a variable minimum distance between rivets, and rivets of different length or heights can be used. High flexibility and change over time due to programmable memory. It can process many workpieces and different rivets can be used in one operation. Picking and placing operations are done in parallel with the primary operation time, saving money. Menu based navigation makes the programming fluid. High acceleration rate with high positioning accuracy.


Automatic tool changer

In machining, an automatic tool changer (ATC) is used in computerized numerical control (CNC) machine tools to improve the production and tool carrying capacity of the machine. ATCs change tools rapidly, reducing non-productive time. They are generally used to improve the capacity of the machines to work with a number of tools. They are also used to change worn out or broken tools. They are one more step towards complete automation.
Description.
Simple CNC machines work with a single tool. Turrets can work with a large number of tools. But if even more tools are required, then an ATC is needed. The tools are stored in a magazine. This allows the machine to work with a large number of tools without operator intervention.
The main parts of an automatic tool changer are the base, the gripper arm, the tool holder, the support arm, and the tool magazines.
Although the ATC increases the reliability, speed, and accuracy of a machine, it creates more challenges compared to manual tool change. For example, the tooling used must be easy to center, be easy for the changer to grab, and there should be a simple way to provide the tool's self-disengagement. Tools used in ATC are secured in tool holders specially designed for this purpose.
Types of tool changers.
Depending on the shape of the magazine, an ATC can be of two types: 1) Drum Type changers are used when the number of tools is lower than 30. The tools are stored on the periphery of the drum.
2) Chain type changers are used when the number of tools is higher than 30 (The number is different depending on the design and manufacturer. It is important to note that the number of tools for the drum type is fewer than the chain type). But the tool search speed will be lower in this case.
Automatic tool changer mechanism.
After receiving the tool change command, the tool to be changed will assume a fixed position known as the "tool change position". The ATC arm comes to this position and picks up the tool. The arm swivels between the machine turret and the magazine. It will have one gripper on each of the two sides. Each gripper can rotate 90°, to deliver tools to the front face of the turret. One will pick up the old tool from the turret and the other will pick up the new tool from the magazine. It then rotates 180° and places the tools into their needed position.
Tool changers on sheet metal working machinery.
ATCs were first used on chip-removal machines, such as mills and lathes. Systems for automatic rearrangement of tools have also been used on sheet metal working machinery. Panel benders have an integrated CNC-controlled device that allows punches to be moved according to the size of the part. Automated tool changes on press brakes were limited to machines integrated on a robotic bending cell. Typically a 6-axis robot used for handling sheet metal blanks is also in charge of changing punches and dies between different batches.
Since the 2020s automatic tool changers have appeared on non-robotic press brakes. The most common configuration is a tool rack on the side of the press brakes, with a shuttle picking up tools and positioning them where needed. This reduces physical strain on the operator and increases overall productivity.
Functions of a tool changer.
The use of automatic changers increases the productive time and reduces unproductive time. It provides the storage of the tools which are returned automatically to the machine tool after carrying out the required operations, increases the flexibility of the machine tool, makes it easier to change heavy and large tools, and permits the automatic renewal of cutting edges.


Burn-in oven

Burn-in ovens in electronics device fabrication, are designed for dynamic and static burn-in of integrated circuits and other electronic devices, including laser diodes. Typical sizes are from under ten to over , with air or nitrogen configurations. Operating temperatures can go over , and can use both single and multiple temperature settings.
Burn-in oven applications can be used in numerous different applications such as high-dissipation forward bias, high-temperature reverse bias, dynamic and static burn-in of microprocessors and other semiconductor devices.
Burn-in ovens are considered a type of batch oven. Other types of batch ovens are bench/laboratory, reach-in, walk in/truck in, and clean process.
One company builds systems designed for burn-in of low power laser diodes up to 1A and high power laser diodes up to 300A.


Color LaserWriter

The Color LaserWriter was a line of PostScript four-color laser printers manufactured by Apple Computer, Inc. in the mid-1990s. These printers were compatible with PCs and Apple's own Macintosh line of computers; these printers were also able to connect to large networks by way of the use of an 10baseT Ethernet port. Two models were released.
Color LaserWriter 12/600 PS.
A PostScript printer, the Color LaserWriter 12/600 PS color laser printer was intended for small business and consumers with high printing requirements. The Windows-compatible driver was of interest due to its ability generate Postscript files (.ps) for later printing.
This printer was released one year before its replacement with the Color LaserWriter 12/660 PS, which had the same specifications as the 12/600 PS, but was sold at a lower price.
Color LaserWriter 12/660 PS.
The Color LaserWriter 12/660 PS is a color laser printer introduced by Apple in October 1996. The printer became a workhorse used in Kinko's copy stores across the United States. The printer's weight, size, speed of printing, and high cost of purchase, operation, and maintenance were its chief drawbacks.


Alumel

Alumel is an alloy consisting of approximately 95% nickel, 2% aluminium, 2% manganese, and 1% silicon. This magnetic alloy is used to make the negative conductors of ANSI Type K (chromel-alumel) thermocouples and thermocouple extension wire. Alumel is a registered trademark of Concept Alloys, Inc.


Engineer's blue

Engineer's blue (also known as scraping blue, Prussian blue, or simply bluing) is a highly pigmented paste used to assist in the mating of two or more components.
History.
Joseph Whitworth popularized the first practical method of making accurate flat surfaces, during the 1830s, by using engineer's blue and scraping techniques on three trial surfaces. Prior to his scraping technique, the same three plate method was employed using polishing techniques, giving less accurate results. This improvement led to an explosion of development of precision instruments using these flat surface generation techniques as a basis for further construction of precise shapes.
Preparation.
Engineer's blue is prepared by mixing Prussian blue with a non-drying oily material (for example, grease). The coloured oil is rubbed onto a reference surface, and the workpiece is then rubbed against the coloured reference; the transfer (by contact) of the pigment indicates the position of high spots on the workpiece or conversely highlight low points. This method has been used to test the flatness of surfaces and the trueness of a bearing assembly.
The fitter may be told to "blue it up" when using this piece of equipment.
Use in toolmaking.
Prussian blue is widely used by tool makers when the core and cavity of a mould is matched during final assembly. It is also used in other tooling applications, especially during assembly, such as stamping tools and pressure die casting tools. A thin coating of Prussian blue is applied (usually with a paint brush) on the "insert", regardless of the shape or contour, of the mould or tool before the matching is done with the mating part. If the Prussian blue (generally called just "blue") appears evenly on the mating area, it is considered, by the tool makers, as "good matching", indicating a good final product from the tool. Usually no tool would be transferred to testing or production without "blue matching", (a term generally used by tool makers in Asia). Prussian blue is considered as an integral part of precision tool making.


Types of press tools

Press tools are commonly used in hydraulic, pneumatic, and mechanical presses to produce the sheet metal components in large volumes. Generally press tools are categorized by the types of operation performed using the tool, such as blanking, piercing, bending, forming, forging, trimming etc. The press tool will also be specified as a blanking tool, piercing tool, bending tool etc.
Classification of press tools.
Blanking tool.
In blanking, metal obtained after cutting is not a scrap if it is usable.
Piercing tool.
Piercing involves cutting of clean holes with a resulting scrap slug. The operation is called die cutting and can also produce flat components where the die, the shaped tool, is pressed into a sheet material employing a shearing action to cut holes. This method can be used to cut parts of different sizes and shapes in sheet metal, leather and many other materials.
Cut off tool.
It is a shearing operation in which blanks are separated from a sheet metal strip by cutting the opposite sides of the part in sequence.
Parting off tool.
This is similar to a cutoff tool, in that a discrete part is cut from a sheet or strip of metal along a desired geometric path. The difference between a cutoff and a parting is that a cutoff can be nestled perfectly on the sheet metal, due to its geometry. With cutoffs, the cutting of sheet metal can be done over one path at a time and there is practically no waste of material. With partings, the shape can not be nestled precisely. Parting involves cutting the sheet metal along two paths simultaneously. Partings waste a certain amount of material, that can be significant.
Trimming tool.
When cups and shells are drawn from flat sheet metal the edge is left wavy and irregular, due to uneven flow of metal. Shown is flanged shell, as well as the trimmed ring removed from around the edge. While a small amount of Material is removed from the side of a component in trimming tool.
Shaving tool.
Shaving removes a small amount of material around the edges of a previously blanked stampings or piercing. A straight, smooth edge is provided and therefore shaving is frequently performed on instrument parts, watch and clock parts and the like. Shaving is accomplished in shaving tools especially designed for the purpose.
it is also required proper die clearance
Forming tool.
Forming is the operation of deforming a part in curved profile.
Forming tools apply more complex forms to work pieces. The line of bend is curved instead of straight and the metal is subjected to plastic flow or deformation.
Drawing tool.
Drawing tools transform flat sheets of metal into cups, shells or other drawn shapes by subjecting the material to severe plastic deformation. Shown in fig is a rather deep shell that has been drawn from a flat sheet. It is an axial elongation through the application of axial force.
This type of Press tool is used to perform only one particular operation therefore classified under stage tools.
Progressive tool.
A progressive tool differs from a stage tool in the following respect: in a progressive tool the final component is obtained by progressing the sheet metal or strip in more than one stage. At each stage the tool will progressively shape the component towards its final shape, with the final stage normally being cutting-off.
Compound tool.
The compound tool differs from progressive and stage tools by the arrangement of the punch and die. It is an inverted tool where blanking and piercing takes place in a single stage and also the blanking punch will act as the piercing die. that means punch will be to the bottom side of the tool and piercing punches to top side of the tool.The burr forms only one side.
Combination tool.
In a combination tool two or more operations such as bending and trimming will be performed simultaneously. Two or more operations such as forming, drawing, extruding, embossing may be combined on the component with various cutting operations like blanking, piercing, broaching and cut off takes place- it can perform a cutting and non cutting operations in a single tool.
General press tool construction.
The general press tool construction will have following elements:-
Cutting force in press tool.
In general, cutting force can be calculated using the formula:
CF =L x T x ζmax
Cutting force will be in Newton (N)
Where,
L = Cut length in mm,(perimeter of profile to be cut)
Ex: 40 mm square to be cut will have cut length of 160 mm
T = Sheet metal thickness in mm,
ζmax = Maximum shear strength of sheet metal in MPa
Stripping force.
Stripping force is the force required to eject the strip from the punches, which helps the strip to go forward for the next operation Stripping force will be usually 10 to 20 % of cutting force (CF)
Press force.
The Press force is the cutting force added to the stripping force:
Press Force = Cutting force + Stripping force


ISI mark

The ISI mark is a standards-compliance mark for industrial products in India since 1950. The mark certifies that a product conforms to an Indian standard (IS) developed by the Bureau of Indian Standards (BIS), the national standards body of India. The ISI mark is by far the most certification mark in the Indian subcontinent. The "ISI" is an initialism of "Indian Standards Institution", the name of the national standards body at 1 January 1978, when it was renamed to the Bureau of the Indian Standards. The ISI mark is mandatory for a certain products to be sold in India, such as many of the electrical appliances like switches, electric motors, wiring cables, heaters, kitchen appliances, etc., and other products like Portland cement, LPG valves, LPG cylinders, automotive tyres, etc. In the case of most other products, ISI marks are optional.
Counterfeiting.
It is very common in India to find products with fake ISI marks. That is, industrial traders cheat customers by affixing ISI marks on the product without actually certified. Fake ISI marks usually do not carry
For example, if a kitchen grinder's box has a small ISI mark on it with the ISI code of the appliance's wire, one can conclude that the wire is BIS-certified but the appliance itself is not an BIS-certified product. Counterfeiting ISI marks is a punishable offence by the law, but enforcement is uncommon.
References.
9. ISI Mark Certification Process, Documents Required, and list of the Products under BIS Certification Scheme - Aleph INDIA
10. ISI/BIS Certification: A Gateway to the Indian Market, ISI mark certification mandatory Products- Brand Liaison


AETHRA Componentes Automotivos

AETHRA is a Brazilian company, founded in 1974 in Minas Gerais, that applies technology to develop and manufacture automotive systems to the global market.
AETHRA is present in the industrial sector over 30 years. Since early foundation, Hammer Indústria de Autopeças Ltda, started to produce stamped components, establishing as auto parts supplier in the Brazilian market. With increasing market demands, Aethra expanded to new units to meet both the development of automotive components for new Auto vehicles, and the manufacture of tooling for the production of stamped components.
Emerging from such intensive investments, AETHRA became one of the largest tooling construction companies in Latin America, also including surface parts, and has attained in the manufacturing of stamped components either small, medium and large-sized, also AETHRA began to supply assemblies and develop new products, promoting the continuous growth of its activities in engineering, tooling and mass production expansion.
In 2003, AETHRA has included in its production the assembly of complete truck cabins. AETHRA has become major player in vehicle development in the Brazilian market, offering everything from engineering services with modern CAD / CAM / CAE workstations, as well as in the construction of soft-toolings, prototypes, 5D laser cutting, development of final tooling, welding lines, assembling and mass production with JIT logistics in several automotive production poles in Brazil.


Wafer-scale integration

Wafer-scale integration (WSI) is a rarely used system of building very-large integrated circuit (commonly called a "chip") networks from an entire silicon wafer to produce a single "super-chip". Combining large size and reduced packaging, WSI was expected to lead to dramatically reduced costs for some systems, notably massively parallel supercomputers. The name is taken from the term very-large-scale integration, the state of the art when WSI was being developed.
Overview.
In the normal integrated circuit manufacturing process, a single large cylindrical crystal (boule) of silicon is produced and then cut into disks known as wafers. The wafers are then cleaned and polished in preparation for the fabrication process. A photographic process is used to pattern the surface where material ought to be deposited on top of the wafer and where not to. The desired material is deposited and the photographic mask is removed for the next layer. From then on the wafer is repeatedly processed in this fashion, putting on layer after layer of circuitry on the surface.
Multiple copies of these patterns are deposited on the wafer in a grid fashion across the surface of the wafer. After all the possible locations are patterned, the wafer surface appears like a sheet of graph paper, with grid lines delineating the individual chips. Each of these grid locations is tested for manufacturing defects by automated equipment. Those locations that are found to be defective are recorded and marked with a dot of paint (this process is referred to as "inking a die" and more modern wafer fabrication techniques no longer require physical markings to identify defective die). The wafer is then sawed apart to cut out the individual chips. Those defective chips are thrown away, or recycled, while the working chips are placed into packaging and re-tested for any damage that might occur during the packaging process.
Flaws on the surface of the wafers and problems during the layering/depositing process are impossible to avoid, and cause some of the individual chips to be defective. The revenue from the remaining working chips has to pay for the entire cost of the wafer and its processing, including those discarded defective chips. Thus, the higher number of working chips or higher "yield", the lower the cost of each individual chip. In order to maximize yield one wants to make the chips as small as possible, so that a higher number of working chips can be obtained per wafer.
Lowering cost.
The significant fraction of the cost of fabrication (typically 30%-50%) is related to testing and packaging the individual chips. Further cost is associated with connecting the chips into an integrated system (usually via a printed circuit board). Wafer-scale integration seeks to reduce this cost, as well as improve performance, by building larger chips in a single package – in principle, chips as large as a full wafer.
Of course this is not easy, since given the flaws on the wafers a single large design printed onto a wafer would almost always not work. It has been an ongoing goal to develop methods to handle faulty areas of the wafers through logic, as opposed to sawing them out of the wafer. Generally, this approach uses a grid pattern of sub-circuits and "rewires" around the damaged areas using appropriate logic. If the resulting wafer has enough working sub-circuits, it can be used despite faults.
Challenges.
Most yield loss in chipmaking comes from defects in the transistor layers or in the high-density lower metal layers.
Another approach – silicon-interconnect fabric (Si-IF) – has neither on the wafer. Si-IF puts only relatively low-density metal layers on the wafer, roughly the same density as the upper layers of a system on a chip, using the wafer only for interconnects between tightly-packed small bare chiplets.
Production attempts.
Many companies attempted to develop WSI production systems in the 1970s and 1980s, but all failed. Texas Instruments and ITT Corporation both saw it as a way to develop complex pipelined microprocessors and re-enter a market where they were losing ground, but neither released any products.
Gene Amdahl also attempted to develop WSI as a method of making a supercomputer, starting Trilogy Systems in 1980 and garnering investments from Groupe Bull, Sperry Rand and Digital Equipment Corporation, who (along with others) provided an estimated $230 million in financing. The design called for a 2.5" square chip with 1200 pins on the bottom.
The effort was plagued by a series of disasters, including floods which delayed the construction of the plant and later ruined the clean-room interior. After burning through about of the capital with nothing to show for it, Amdahl eventually declared the idea would only work with a 99.99% yield, which wouldn't happen for 100 years. He used Trilogy's remaining seed capital to buy Elxsi, a maker of VAX-compatible computers, in 1985. The Trilogy efforts were eventually ended and "became" Elxsi.
In 1989 Anamartic developed a wafer stack memory based on the technology of Ivor Catt, but the company was unable to ensure a large enough supply of silicon wafers and folded in 1992.
Wafer-scale devices in production.
Cerebras Systems processor.
On August 19, 2019, American computer systems company Cerebras Systems presented their development progress of WSI for deep learning acceleration. Cerebras' Wafer-Scale Engine (WSE-1) chip is 46,225mm2 (215mm × 215mm), around 56× larger than the largest GPU die. It is manufactured by TSMC using their 16nm process. The WSE-1 features 1.2 trillion transistors, 400,000 AI cores, 18GB of on-chip SRAM, 100Pbit/s on-wafer fabric bandwidth, and 1.2Pbit/s I/O off-wafer bandwidth. The price and clock rate have not been disclosed. In 2020, the company's product, the CS-1, was tested in computational fluid dynamics simulations. Compared to the Joule Supercomputer at NETL, the CS-1 was 200 times faster, while using much less power.
In April 2021, Cerebras announced the WSE-2, with twice the number of transistors and 100% claimed yield, which is achieved by designing a system in which any manufacturing defect can be bypassed. The Cerebras CS-2 system, which incorporates the WSE-2, is in serial production.


Shielding gas

Shielding gases are inert or semi-inert gases that are commonly used in several welding processes, most notably gas metal arc welding and gas tungsten arc welding (GMAW and GTAW, more popularly known as MIG (Metal Inert Gas) and TIG (Tungsten Inert Gas), respectively). Their purpose is to protect the weld area from oxygen, and water vapour. Depending on the materials being welded, these atmospheric gases can reduce the quality of the weld or make the welding more difficult. Other arc welding processes use alternative methods of protecting the weld from the atmosphere as well – shielded metal arc welding, for example, uses an electrode covered in a flux that produces carbon dioxide when consumed, a semi-inert gas that is an acceptable shielding gas for welding steel.
Improper choice of a welding gas can lead to a porous and weak weld, or to excessive spatter; the latter, while not affecting the weld itself, causes loss of productivity due to the labor needed to remove the scattered drops.
If used carelessly, shielding gasses can displace oxygen, causing hypoxia and potentially death.
Common shielding gases.
Shielding gases fall into two categories—inert or semi-inert. Only two of the noble gases, helium and argon, are cost effective enough to be used in welding. These inert gases are used in gas tungsten arc welding, and also in gas metal arc welding for the welding of non-ferrous metals. Semi-inert shielding gases, or active shield gases, include carbon dioxide, oxygen, nitrogen, and hydrogen. These active gases are used with GMAW on ferrous metals. Most of these gases, in large quantities, would damage the weld, but when used in small, controlled quantities, can improve weld characteristics.
Properties.
The important properties of shielding gases are their thermal conductivity and heat transfer properties, their density relative to air, and the ease with which they undergo ionization. Gases heavier than air (e.g. argon) blanket the weld and require lower flow rates than gases lighter than air (e.g. helium). Heat transfer is important for heating the weld around the arc. Ionizability influences how easy the arc starts, and how high voltage is required. Shielding gases can be used pure, or as a blend of two or three gases. In laser welding, the shielding gas has an additional role, preventing formation of a cloud of plasma above the weld, absorbing significant fraction of the laser energy. This is important for CO2 lasers; Nd:YAG lasers show lower tendency to form such plasma. Helium plays this role best due to its high ionization potential; the gas can absorb high amount of energy before becoming ionized.
Argon is the most common shielding gas, widely used as the base for the more specialized gas mixes.
Carbon dioxide is the least expensive shielding gas, providing deep penetration, however it negatively affects the stability of the arc and enhances the molten metal's tendency to create droplets (spatter). Carbon dioxide in concentration of 1-2% is commonly used in the mix with argon to reduce the surface tension of the molten metal. Another common blend is 25% carbon dioxide and 75% argon for GMAW.
Helium is lighter than air; larger flow rates are required. It is an inert gas, not reacting with the molten metals. Its thermal conductivity is high. It is not easy to ionize, requiring higher voltage to start the arc. Due to higher ionization potential it produces hotter arc at higher voltage, provides wide deep bead; this is an advantage for aluminium, magnesium, and copper alloys. Other gases are often added. Blends of helium with addition of 5–10% of argon and 2–5% of carbon dioxide ("tri-mix") can be used for welding of stainless steel. Used also for aluminium and other non-ferrous metals, especially for thicker welds. In comparison with argon, helium provides more energy-rich but less stable arc. Helium and carbon dioxide were the first shielding gases used, since the beginning of World War 2. Helium is used as a shield gas in laser welding for carbon dioxide lasers. Helium is more expensive than argon and requires higher flow rates, so despite its advantages it may not be a cost-effective choice for higher-volume production. Pure helium is not used for steel, as it causes an erratic arc and encourages spatter.
Oxygen is used in small amounts as an addition to other gases; typically as 2–5% addition to argon. It enhances arc stability and reduces the surface tension of the molten metal, increasing wetting of the solid metal. It is used for spray transfer welding of mild carbon steels, low alloy and stainless steels. Its presence increases the amount of slag. Argon-oxygen (Ar-O2) blends are often being replaced with argon-carbon dioxide ones. Argon-carbon dioxide-oxygen blends are also used. Oxygen causes oxidation of the weld, so it is not suitable for welding aluminium, magnesium, copper, and some exotic metals. Increased oxygen makes the shielding gas oxidize the electrode, which can lead to porosity in the deposit if the electrode does not contain sufficient deoxidizers. Excessive oxygen, especially when used in application for which it is not prescribed, can lead to brittleness in the heat affected zone. Argon-oxygen blends with 1–2% oxygen are used for austenitic stainless steel where argon-CO2 can not be used due to required low content of carbon in the weld; the weld has a tough oxide coating and may require cleaning.
Hydrogen is used for welding of nickel and some stainless steels, especially thicker pieces. It improves the molten metal fluidity, and enhances cleanness of the surface. It is added to argon in amounts typically under 10%. It can be added to argon-carbon dioxide blends to counteract the oxidizing effects of carbon dioxide. Its addition narrows the arc and increases the arc temperature, leading to better weld penetration. In higher concentrations (up to 25% hydrogen), it may be used for welding conductive materials such as copper. However, it should not be used on steel, aluminum or magnesium because it can cause porosity and hydrogen embrittlement; its application is usually limited only to some stainless steels.
Nitric oxide addition serves to reduce production of ozone. It can also stabilize the arc when welding aluminium and high-alloyed stainless steel.
Other gases can be used for special applications, pure or as blend additives; e.g. sulfur hexafluoride or dichlorodifluoromethane.
Sulfur hexafluoride can be added to shield gas for aluminium welding to bind hydrogen in the weld area to reduce weld porosity.
Dichlorodifluoromethane with argon can be used for protective atmosphere for melting of aluminium-lithium alloys. It reduces the content of hydrogen in the aluminium weld, preventing the associated porosity. This gas, however, is being used less because it has a strong ozone depletion potential.
Applications.
The applications of shielding gases are limited primarily by the cost of the gas, the cost of the equipment, and by the location of the welding. Some shielding gases, like argon, are expensive, limiting its use. The equipment used for the delivery of the gas is also an added cost, and as a result, processes like shielded metal arc welding, which require less expensive equipment, might be preferred in certain situations. Finally, because atmospheric movements can cause the dispersion of the shielding gas around the weld, welding processes that require shielding gases are often only done indoors, where the environment is stable and atmospheric gases can be effectively prevented from entering the weld area.
The desirable rate of gas flow depends primarily on weld geometry, speed, current, the type of gas, and the metal transfer mode being utilized. Welding flat surfaces requires higher flow than welding grooved materials, since the gas is dispersed more quickly. Faster welding speeds, in general, mean that more gas needs to be supplied to provide adequate coverage. Additionally, higher current requires greater flow, and generally, more helium is required to provide adequate coverage than argon. Perhaps most importantly, the four primary variations of GMAW have differing shielding gas flow requirements—for the small weld pools of the short circuiting and pulsed spray modes, about 10 L/min (20 ft3/h) is generally suitable, while for globular transfer, around 15 L/min (30 ft3/h) is preferred. The spray transfer variation normally requires more because of its higher heat input and thus larger weld pool; along the lines of 20–25 L/min (40–50 ft3/h).


Draw bench

A draw bench is a machine used to do cold work on a metal, such as changing the shape of the metal without applying heat and applying only pressure.
Machine construction.
It consists of a chain drive, driven by a motor and a set of gears. The other end of the machine consists of a die mounted on a thick steel plate. The workpiece is inserted through the die and clamped on a trolley which then is hooked onto the chain for pulling across.
Die.
The die is usually made of tungsten carbide with a steel housing. The die can be made to any desired shape (round, square, rectangular, triangular, half round, L-shaped, oval etc.).


Filler (packaging)

Fillers (or filling machines) are used for packaging, mainly for food/beverage but for other products as well. These are used to fill either a bottle or a pouch, depending on the product.
There are several types of fillers used by the packaging industry. The type of Food or beverage filling machines to be used is usually determined by the type of product to be filled, speed requirements, quality and shelf life expectations, resources availability, technology feasibility and many other variables. Type of food products may range from solid to semi-solids, from liquids to frozen, from hot to cold, from free flowing to highly viscous products etc. This wide range of product characteristics also suggests that filling machines with great flexibility and versatility are the most valuable. There are various filling technologies for liquid and dry products and product filling machines can be rotary or inline, intermittent or continuous motion, semi-automatic or fully automatic with various filling technologies to cater for the huge range of product variables and user requirements, each offering unique advantages. The following are the most common:


Roll bender

A roll bender is a mechanical jig having three rollers used to bend a metal bar into a circular arc. The rollers freely rotate about three parallel axes, which are arranged with uniform horizontal spacing. Two outer rollers, usually immobile, cradle the bottom of the material while the inner roller, whose position is adjustable, presses on the topside of the material.
Roll bending may be done to both sheet metal and bars of metal. If a bar is used, it is assumed to have a uniform cross-section, but not necessarily rectangular, as long as there are no overhanging contours, i.e. positive draft. Such bars are often formed by extrusion. The material to be shaped is suspended between the rollers. The end rollers support the bottomside of the bar and have a matching contour (inverse shape) to it in order to maintain the cross-sectional shape. Likewise, the middle roller is forced against the topside of the bar and has a matching contour to it.
Operation.
After the bar is initially inserted into the jig, the middle roller is manually lowered and forced against the bar with a screw arrangement. This causes the bar to undergo both plastic and elastic deformation. The portion of the bar between the rollers will take on the shape of a cubic polynomial, which approximates a circular arc. The rollers are then rotated moving the bar along with them. For each new position, the portion of the bar between the rollers takes on the shape of a cubic modified by the end conditions imposed by the adjacent sections of the bar. When either end of the bar is reached, the force applied to the center roller is incrementally increased, the roller rotation is reversed and as the rolling process proceeds, the bar shape becomes a better approximation to a circular arc. During the rolling process, the force applied to the center roller is incrementally increased to gradually bring the arc of the bar to the desired radius.
Plastic and elastic deformation.
The plastic deformation of the bar is retained throughout the process. However, the elastic deformation is reversed as a section of bar leaves the area between the rollers. This spring-back needs to be compensated in adjusting the middle roller to achieve a desired radius. The amount of spring back depends upon the elastic compliance (inverse of stiffness) of the material relative to its ductility. Aluminum alloys, for example, tend to have high ductility relative to their elastic compliance, whereas steel tends to be the other way around. Therefore aluminum bars are more amenable to bending into an arc than are steel bars.


Mastercam

Mastercam is a suite of Computer-Aided Manufacturing (CAM) and CAD/CAM software applications developed by CNC Software, LLC. Founded in Massachusetts in 1983, CNC Software are headquartered in Tolland, Connecticut.
Mastercam is CNC Software's main product. It started as a 2D CAM system with CAD tools that let machinists design virtual parts on a computer screen and also guided computer numerical controlled (CNC) machine tools in the manufacture of parts. Mastercam has been ranked by CIMdata Inc. as the most widely used CAM package in the world since 1994.


Fractional job scheduling

Fractional job scheduling is a variant of optimal job scheduling in which it is allowed to break jobs into parts and process each part separately on the same or a different machine. Breaking jobs into parts may allow for improving the overall performance, for example, decreasing the makespan. Moreover, the computational problem of finding an optimal schedule may become easier, as some of the optimization variables become continuous. On the other hand, breaking jobs apart might be costly.
Variants.
There are several variants of job scheduling problems in which it is allowed to break jobs apart. They can be broadly classified into preemption and splitting.
Job scheduling with preemption.
Various problems have been studied in job scheduling with preemption. One of them is generalized multiprocessor scheduling (GMS). It has two variants.
In both variants, the goal is to find a schedule that minimizes the makespan subject to the preemption constraints.
For identical machines, Shchepin and Vakhania prove that with at most formula_3 total preemptions, the problem is NP-hard, whereas McNaughton shows a linear-time algorithm with formula_4 preemptions.
For uniform machines, a polynomial algorithm by Gonzalez and Sahni yields at most formula_5 preemptions. Shachnai, Tamir, and Woeginger proved NP-hardness for the case where the number of preemption is strictly less than formula_5. They also presented a PTAS for GMS with a global preemption bound, and another PTAS for GMS with job-wise preemption bound when the number of machines is a fixed constant.
Soper and Strusevitch study the special case in which at most one preemption is allowed. They show that makespan minimization is polynomial for two machines.
Many papers study other variants of preemptive scheduling. For example, Liu and Cheng consider single-machine scheduling with job release and delivery dates, where there is no firm bound on the number of preemptions, but each preemption requires spending time on "job setup".
Some works like Blazewicz "et al." or Deng "et al." study preemptive scheduling for jobs with parallelism where jobs must be processed simultaneously on several processors.
Job scheduling with splitting.
Various objectives have been studied. There are many variants including different setup times. In machine scheduling, the "setup time" refers to the time required to prepare a machine for a specific job or task. Sequence-dependent setup time is a situation where the setup time required for a job depends on the job that came before it, rather than being constant for all jobs (independent job setup time).
Serafini assumes unbounded splittings and preemptions and gives polynomial-time algorithms that minimize the maximum tardiness and the maximum weighted tardiness, for uniform and unrelated machines.
Xing and Zhang allow unbounded splittings, and give polynomial algorithms for many optimality criteria (such as makespan, lateness, tardiness, and more), with identical, uniform, and unrelated machines. For the case with independent job setup time, they give a formula_7 approximation algorithm.
Son et al. study makespan minimization on a single machine with a machine-availability constraint with a lower bound on the length of each part of a job that is split.
For identical machines, Shim and Kim suggest a branch and bound algorithm with the objective to minimize total tardiness with independent job setup time. Yalaoui and Chu propose a heuristic to the same problem, with the objective to minimize the makespan. Kim et al. suggest a two-phase heuristic algorithm with the objective of minimizing total tardiness. With the objective to minimize the makespan, Kim studies another variant with family setup time in which no setup is required when parts from the same job are produced consecutively. And, Wang et al. include a learning property that improves the processing time of a job according to the learning effect. The learning has to be restarted if one job is split and processed by a different machine.
For uniform machines, Kim and Lee study a variant with dedicated machines (there are some dedicated machines for each job), sequence-dependent setup times, and limited set-up resources (jobs require setup operators that are limited) with the objective to minimize the makespan. Krysta, Sanders, and Vöcking study makespan minimization using the k-splittable variant, a variant where each job is allowed to be split into most formula_8 different machines. They show that this variant and another more general variant where each job has its own splitability parameter, are NP-hard. They give some approximation algorithms, but their main result is a polynomial-time algorithm for both problems, for a fixed number of machines. They show that allowing a bounded number of splittings reduces the complexity of scheduling.
In all these works, there is no global bound on the number of splitting jobs.


Takaoka plant

The Toyota Takaoka Assembly Plant, also known as Takaoka Plant, was built in Toyota City, Aichi, Japan in 1966 to build the first Toyota Corolla (series KE10). Production officially began January 1967 where production was transferred from the Toyota Motomachi plant.
The location continues to build the Corolla, and was the manufacturing location for past and current models that included the Toyota Publica, Toyota Sprinter, Toyota Carina, Toyota Tercel, Toyota Cynos and the Toyota Prius. Its current size is and employs 3,150 people. This number of employees is from December 2011, and excludes fixed-term employees and short-term employees.
It also serves as a support location for various Toyota assembly locations internationally.


Programming station

A programming station is a terminal or computer that allows a machine operator to control a machine remotely, rather than being on the factory or shop floor. The programming station usually provides all the functionality including management and diagnostics that are found on the main control station.


Slag (welding)

Welding slag is a form of slag, or vitreous material produced as a byproduct of some arc welding processes, most specifically shielded metal arc welding (also known as stick welding), submerged arc welding, and flux-cored arc welding. Slag is formed when flux, the solid shielding material used in the welding process, melts in or on top of the weld zone (also known as Dross). Slag is the solidified remaining flux after the weld area cools.
Flux.
Welding flux is a combination of carbonate and silicate materials used in welding processes to shield the weld from atmospheric gases. When the heat of the weld zone reaches the flux, the flux melts and outgasses. The gases produced push the atmospheric gas back, preventing oxidation (and reactions with nitrogen).
The melted flux covers the molten metal in the weld zone. Flux materials are chosen so that the density of the melted flux / slag is lower than that of the metal being welded, so that the flux floats to the very top of the weld puddle and leaves pure or nearly pure metal to solidify below.
Flux materials may also contribute to metal behavior in the molten metal, with physical or chemical alterations to the molten metal.
The flux cover also helps thermally insulate the weld and reduce the cooling rate.
Inclusions.
It is possible for areas of slag to become embedded within the solidified metal, if it did not float to the top of the molten metal for some reason. These are called inclusions and are a form of welding defect. Inclusions may be visible on the surface after cleaning, or may be completely contained within the metal, in that case they can only be detected on X-rays of the weld, requiring grinding or drilling to remove (followed by re-welding that section).
Processes.
Four welding processes use flux in slag-producing manners:
Removal of slag.
Slag does not contribute to strength or protection of metals after the welding process; it is waste material. Removal of the slag is necessary for four reasons:
Removal is usually done using manual or power tools. Manual tools may include a welding or chipping hammer, which has a pointed tip on one end to break up large chunks of slag efficiently, or wire brushes. Power tools include angle grinders with grinder disks or wire brush wheels.


NSK Ltd.

, also known in some markets as NSK Automation, is a large manufacturer of bearings globally and the largest in Japan. The company produces industrial machinery bearings, precision machinery and parts, and automotive bearings and components.
The company is listed on the Tokyo Stock Exchange, is a component of the Nikkei 225 stock index, and has over 144 overseas operations in 29 countries.
Present day business.
30,577 employees form a worldwide technology network consisting of over 65 production plants in 14 countries. Approximately three million new bearings are manufactured per day (from miniature bearings with a one-millimetre bore to bearings with a diameter of five meters).


Laser engraving

Laser engraving is the practice of using lasers to engrave an object. Laser marking, on the other hand, is a broader category of methods to leave marks on an object, which in some cases, also includes color change due to chemical/molecular alteration, charring, foaming, melting, ablation, and more. The technique does not involve the use of inks, nor does it involve tool bits which contact the engraving surface and wear out, giving it an advantage over alternative engraving or marking technologies where inks or bit heads have to be replaced regularly.
The impact of laser marking has been more pronounced for specially designed "laserable" materials and also for some paints. These include laser-sensitive polymers and novel metal alloys.
The term laser marking is also used as a generic term covering a broad spectrum of surfacing techniques including printing, hot-branding and laser bonding. The machines for laser engraving and laser marking are the same, so that the two terms are sometimes confused by those without knowledge or experience in the practice.
Laser engraving mechanisms.
Laser engraving is the process of selectively removing microscopic layers of material, thus creating visible marks on the treated surface. Depending on the materials, the laser-material interactions can be different. On harder surfaces, the mechanism of action is primarily the ablation where the focused beam of laser dislodges microscopic particles from the substrate. Engraving can achieve depth of 100μm and beyond, whereas laser marking is typically shallower.
The choice of lasers is important for the quality of the mark. To create a clean mark, short bursts of high quality laser pulses are preferable, since they are able to transfer large amounts of energy without causing significant heating and melting of the sample.
Laser engraving machines.
A laser engraving machine consists of three main parts: a laser, a controller, and a surface. The laser is a drawing tool: the beam emitted from it allows the controller to trace patterns onto the surface. The controller determines the direction, intensity, speed of movement, and spread of the laser beam aimed at the surface. The surface is chosen to match the type of material the laser can act on.
There are three main genres of engraving machines. The most common is the X–Y table where, usually, the workpiece (surface) is stationary and the laser optics move around in two dimensions, directing the laser beam to draw vectors. Sometimes the laser is stationary and the workpiece moves. Sometimes the workpiece moves in one axis and the laser in the other. A second genre is for cylindrical workpieces (or flat workpieces mounted around a cylinder) where the laser effectively traverses a fine helix while on–off laser pulsing produces the desired raster image. In the third genre, both the laser and workpiece are stationary and galvo mirrors move the laser beam over the workpiece surface. Laser engravers using this technology can work in either raster or vector mode.
The point where the laser beam touches the surface should be on the focal plane of the laser's optical system and is usually synonymous with its focal point. This point is typically small, perhaps less than a fraction of a millimetre (depending on the optical wavelength). Only the area inside this focal point is significantly affected when the laser beam passes over the surface. The energy delivered by the laser changes the surface of the material at the focal point. It may heat up the surface and subsequently the material, or perhaps the material may fracture (known as "glassing" or "glassing up") and flake off the surface. Cutting through the paint of a metal part is generally how material is laser engraved.
If the surface material is vaporised during laser engraving, ventilation through the use of blowers or a vacuum pump are almost always required to remove the noxious fumes and smoke arising from this process, and for removal of debris on the surface to allow the laser to continue engraving.
A laser can remove material very efficiently because the laser beam can be designed to deliver energy to the surface in a manner which converts a high percentage of the light energy into heat. The beam is highly focused and collimated—in most non-reflective materials like wood, plastics and enamel surfaces, the conversion of light energy to heat is more than {x%} efficient. However, because of this efficiency, the equipment used in laser engraving may heat up rather quickly. Elaborate cooling systems are required for the laser. Alternatively, the laser beam may be pulsed to decrease the amount of excessive heating.
Different patterns can be engraved by programming the controller to traverse a particular path for the laser beam over time. The "trace" of the laser beam is carefully regulated to achieve a consistent removal depth of material. For example, criss-crossed paths are avoided to ensure that each etched surface is exposed to the laser only once, so the same amount of material is removed. The speed at which the beam moves across the material is also considered in creating engraving patterns. Changing the intensity and spread of the beam allows more flexibility in the design. For example, by changing the proportion of time (known as "duty-cycle") the laser is turned on during each pulse, the power delivered to the engraving surface can be controlled appropriately for the material.
Since the position of the laser is known exactly by the controller, it is not necessary to add barriers to the surface to prevent the laser from deviating from the prescribed engraving pattern. As a result, no resistive mask is needed in laser engraving. This is primarily why this technique is different from older engraving methods.
A good example of where laser engraving technology has been adopted into the industry norm is the production line. In this particular setup, the laser beam is directed towards a rotating or vibrating mirror. The mirror moves in a manner which may trace out numbers and letters onto the surface being marked. This is particularly useful for printing dates, expiry codes, and lot numbering of products travelling along a production line. Laser marking allows materials made of plastic and glass to be marked "on the move". The location where the marking takes place is called a "marking laser station", an entity often found in packaging and bottling plants. Older, slower technologies such as hot stamping and pad printing have largely been phased out and replaced with laser engraving.
For more precise and visually decorative engravings, a "laser table" (also known as an "X–Y" or "XY" table) is used. The laser is usually fixed permanently to the side of the table and emits light towards a pair of movable mirrors so that every point of the table surface can be swept by the laser. At the point of engraving, the laser beam is focused through a lens at the engraving surface, allowing very precise and intricate patterns to be traced out.
A typical setup of a laser table involves the fixed laser emitting light parallel to one axis of the table aimed at a mirror mounted on the end of an adjustable rail. The beam reflects off the mirror angled at 45 degrees so that the laser travels a path exactly along the length of the rail. This beam is then reflected by another mirror mounted to a movable trolley which directs the beam perpendicular to the original axis. In this scheme, two degrees of freedom (one vertical, and one horizontal) for etching can be represented.
In other laser engraving devices such as "flat table" or "drum engraving", the laser beam is controlled to direct most of its energy a fixed penetration depth into the material to be engraved. In this manner, only a particular depth of material is removed when the engraving takes place. A simple machined stick or angle-iron can be used as a tool to help trained technologists adjust the engraver to achieve the required focusing. This setup is preferred for surfaces which do not vary in height appreciably.
For surfaces that vary in height, more elaborate focusing mechanisms have been developed. Some are known as "dynamic auto focus systems". They adjust the lasing parameters in real time to adapt to the changes to the material as it is being etched. Typically, the height and depth of the surface are monitored with devices tracking changes to ultrasound, infrared, or visible light aimed at the engraving surface. These devices, known as "pilot beams" or "pilot lasers" (if a laser is used) help guide the adjustments made to the lens of the laser in determining the optimal spot to focus on the surface and remove material effectively.
"X–Y" laser engraving machines may operate in vector and raster mode.
Vector engraving follows the line and curve of the pattern to be engraved, much like a pen-based plotter draws by constructing line segments from a description of the outlines of a pattern. Much early engraving of signs and plaques (laser or otherwise) used pre-stored font outlines so that letters, numbers or even logos could be scaled to size and reproduced with exactly defined strokes. Unfortunately, "fill" areas were problematic, as cross-hatching patterns and dot-fills sometimes exhibited moiré effects or uber-patterns caused by the imprecise calculation of dot spacings. Moreover, rotations of a font or dynamic scaling often were beyond the capabilities of the font-rendering device. The introduction of the PostScript page-description language now allows much greater flexibility—now virtually anything that can be described in vectors by PostScript-enabled software like CorelDRAW or Adobe Illustrator can be outlined, filled with suitable patterns, and laser-engraved.
Raster engraving traces the laser across the surface in a back-and-forth slowly advancing linear pattern that will remind one of the printhead on an inkjet or similar printer. The pattern is usually optimized by the controller/computer so that areas to either side of the pattern which aren't to be engraved are ignored and the trace across the material is thus shortened for better efficiency. The amount of advance of each line is normally less than the actual dot-size of the laser; the engraved lines overlap just slightly to create a continuity of engravure. As is true of all rasterized devices, curves and diagonals can sometimes suffer if the length or position of the raster lines varies even slightly in relation to the adjacent raster scan; therefore exact positioning and repeatability are critically important to the design of the machine. The advantage of rasterizing is the near effortless "fill" it produces. Most images to be engraved are bold letters or have large continuously engraved areas, and these are well-rasterized. Photos are rasterized (as in printing), with dots larger than that of the laser's spot, and these also are best engraved as a raster image. Almost any page-layout software can be used to feed a raster driver for an X–Y or drum laser engraver. While traditional sign and plaque engraving tended to favour the solid strokes of vectors out of necessity, modern shops tend to run their laser engravers mostly in raster mode, reserving vector for a traditional outline "look" or for speedily marking outlines or "hatches" where a plate is to be cut.
Materials that can be engraved.
Natural materials.
The marking of organic materials like wood is based on material carbonisation which produces darkening of the surface and marks with high contrast. Directly "burning" images on wood were some of the first uses of engraving lasers. The laser power required here is often less than 10 watts depending on the laser being used as most are different. Hardwoods like walnut, mahogany and maple produce good results. Softwoods can be judiciously engraved but tend to vaporise at less-consistent depths. Marking softwood requires the lowest power levels and enables the fastest cut speeds, while active cooling (e.g. a fan with sufficient airflow) inhibits ignition. Hard papers and fiberboard work well; linty papers and newsprint are like softwoods. Fur is not engraveable; finished leathers though can be laser-engraved with a look very similar to hot-branding. Certain latex rubber compounds can be laser engraved; for example these can be used to fabricate inking-stamps.
Paper masking tape is sometimes used as a pre-engraving overcoat on finished and resiny woods so that cleanup is a matter of picking the tape off and out of the unengraved areas, which is easier than removing the sticky and smoky surround "halos" (and requires no varnish-removing chemicals).
Plastics.
Each plastic has specific material properties, especially the light absorption spectrum. The laser irradiation can generate direct chemical modifications, melting or evaporation of the material. Plastics are rarely seen in their pure state because several additives are used such as colorants, ultraviolet retardants, release agents, etc. These additives impact the result of laser marking.
Standard cast acrylic plastic, acrylic plastic sheet, and other cast resins generally laser very well. A commonly engraved award is a cast acrylic shape designed to be lasered from the back side. Styrene (as in compact disc cases) and many of the thermoforming plastics will tend to melt around the edge of the engraving spot. The result is usually "soft" and has no "etch" contrast. The surface may actually deform or "ripple" at the lip areas. In some applications this is acceptable; for example date markings on 2-litre soda bottles do not need to be sharp.
For signage and face plates, etc., special laser-marked plastics were developed. These incorporate silicate or other materials which conduct excess heat away from the material before it can deform. Outer laminates of this material vaporise easily to expose different coloured material below.
Other plastics may be successfully engraved, but orderly experimentation on a sample piece is recommended. Bakelite is said to be easily laser-engraved; some hard engineering plastics work well. Expanded plastics, foams and vinyls, however, are generally candidates for routing rather than laser engraving. Plastics with a chlorine content (such as vinyl, PVC) produce corrosive chlorine gas when lasered, which combines with Hydrogen in the air to produce vaporised hydrochloric acid which can damage a laser engraving system. Urethane and silicone plastics usually don't work well—unless it is a formulation filled with cellulose, stone or some other stable insulator material.
Many light switchplates from companies such as Leviton or Lutron can be laser engraved. Again, experimentation may be necessary to develop the correct laser settings to result in engraving the surface rather than melting it. Often the laser engraving is followed by backfilling with paint on the engraved surface to produce more contrast between the engraved surface and the surrounding surface.
Kevlar can be laser-engraved and laser-cut. However, Kevlar does give off extremely hazardous fumes (cyanide gas) when it is vaporised.
Metals.
Metals are heat resistant and thermally conductive, making them more difficult to engrave than other materials. Due to their thermal conductivity, pulsed, rather than continuous wave lasers, are preferred in laser engraving applications. High peak power, low pulse duration lasers are able to ablate material off a metal engraving surface without delivering enough energy to melt the surface.
The best traditional engraving materials started out being the worst laser-engravable materials. This problem has now been solved using lasers at shorter wavelength than the traditional 10,640 nm wavelength CO2 laser. Using Yb:Fiber Lasers, Nd:YVO4 or at 1,064 nm wavelength, or its harmonics at 532 and 355 nm, metals can now easily be engraved using commercial systems.
Coated metals.
The same conduction that works against the spot vaporisation of metal is an asset if the objective is to vaporise some other coating away from the metal. Laser engraving metal plates are manufactured with a finely polished metal, coated with an enamel paint made to be "burned off". At levels of 10 to 30 watts, excellent engravings are made as the enamel is removed quite cleanly. Much laser engraving is sold as exposed brass or silver-coated steel lettering on a black or dark-enamelled background. A wide variety of finishes are now available, including screen-printed marble effects on the enamel.
Anodized aluminum is commonly engraved or etched with laser machines. With power less than 40W this metal can easily be engraved with clean, impressive detail. The laser bleaches the color exposing the white or silver aluminum substrate. Although it comes in various colors, laser engraving black anodized aluminum provides the best contrast of all colors. Unlike most materials engraving anodize aluminum does not leave any smoke or residue.
Spray coatings can be obtained for the specific use of laser engraving metals, these sprays apply a coating that is visible to the laser light which fuses the coating to the substrate where the laser passed over. Typically, these sprays can also be used to engrave other optically invisible or reflective substances such as glass and are available in a variety of colours. Besides spray coatings, some laser-markable metals come pre-coated for imaging. Products such as this transform the surface of the metal to a different color (often black, brown or grey).
Stone and glass.
Stone and glass do not vaporise or melt easily. As a result, this makes them generally a better candidate for other means of engraving, most notably sandblasting or cutting using diamonds and water. But when a laser hits glass or stone, something else interesting happens: it fractures. Pores in the surface expose natural grains and crystalline "stubs" which, when heated very quickly, can separate a microscopic sized "chip" from the surface because the hot piece is expanding relative to its surroundings.
So lasers are indeed used to engrave on glass, and if the power, speed and focus are just right, excellent results can be achieved. One should avoid large "fill" areas in glass engraving because the results across an expanse tend to be uneven; the glass ablation simply cannot be depended on for visual consistency, which may be a disadvantage or an advantage depending on the circumstances and the desired effect. As of 2021, recent advances in UV Laser technology now supply 10W (or greater) of UV lasing energy and produce significantly better engraving results on glass than prior, lower powered iterations of UV laser marking systems (i.e. 3W) or classic laser marking systems. The newer UV systems engrave cleanly and clearly without a high degree of micro-fracturing on the mark surface. Since modern 10W UV laser systems heat the surrounding substrate less than other laser marking systems, glass substrates are significantly less prone to fracturing from the laser marking process. High quality fill engravings on thin glass and crystal substrates are now regularly reproducible at high-volume in full production environments.
Jewelry.
The demand for personalized jewelry has made jewellers more aware of the benefits of the laser engraving process.
Jewellers found that by using a laser, they could tackle an engraving task with greater precision. In fact, jewellers discovered that laser engraving allowed for more precision than other types of engraving. At the same time, jewellers discovered that laser applied engravings had a number of other desirable features. These features include the customization, personalization, and sheer beauty of these engravings.
At one time jewellers who attempted to do laser engraving did need to use large pieces of equipment. Now the devices that perform laser engraving come in units. Some entrepreneurs have placed such units in mall kiosks. That has made laser engraving jewelers much more accessible. The makers of machines for laser engraving jewellers have developed some very specialized equipment. They have designed machines that can engrave the inside of a ring. They have also created machines that have the ability to engrave the back of a watch.
A laser can cut into both flat and curved surfaces such as the surfaces on jewelry. That points out the reason why jewellers have welcomed all the adaptations for the creation of laser engraved jewelry.
Fine art.
Laser engraving can also be used to create works of fine art. Generally, this involves engraving into planar surfaces, to reveal lower levels of the surface or to create grooves and striations which can be filled with inks, glazes, or other materials. Some laser engravers have rotary attachments which can engrave around an object. Artists may digitize drawings, scan or create images on a computer, and engrave the image onto any of the materials cited in this article.
Trophies, Plaques and Awards.
The relatively low cost of laser engraving, driven by automation and inexpensive materials, makes it an ideal solution for personalization of trophies and awards. Whereas hand engraving may be a viable solution for more expensive champion’s trophies, laser customization lends itself to team and participation trophies which are often ordered in quantity and carry relatively low margins.
Many also prefer the legibility afforded by a laser, which often delivers a crisper appearance than other methods at a much lower cost.
Laserable materials, whether plastic or FlexiBrass, are available in a variety of colors, adding to the popularity of laser personalization for trophies and plaques. The two most popular combinations are gold lettering on a black background and black lettering on a gold background. While the same color combinations are common for plaques as well, the variety of colors used in plaque engraving is more varied.
Laser etched mirrors.
As with regular etched mirrors, the initial focus of laser engraving machines was to etch an image onto the glass surface of the mirror. When power, focus and speed are optimized, similar results to sandblasting or chemical etching can be achieved.
In a new form of mirror engraving the laser pulsates through the reflective silver layer at the rear of the mirror. As a result, the glass side of a laser engraved mirror remains intact, maintaining the full reflective qualities of the original mirror.
After the engraving process in finished, the rear of the mirror needs to be "filled" with a new coating to bring out the lasered detail. When a photograph or text is laser engraved, a rear coating of solid black will lend monochromatic images the greatest definition. Coloured coatings can supply chromaticity.
Industrial applications.
Direct laser engraving of flexographic plates and cylinders.
Direct laser engraving of flexographic printing cylinders and plates has been an established process since the 1970s. This first began with the use of a carbon dioxide laser used to selectively ablate or evaporate a variety of rubber plate and sleeve materials to produce a print-ready surface without the use of photography or chemicals. With this process there is no integral ablation mask as with direct photopolymer laser imaging (discussed below). Instead a high-power carbon dioxide laser head burns away, or ablates, unwanted material. The aim is to form sharp relief images with steep first relief and contoured shoulder supported edges to give a high-standard of process color reproduction. A short water wash and dry cycle follows, which is less complex than in the post-processing stages for direct laser imaging or conventional flexo platemaking using photopolymer plates. After engraving, the photopolymer is exposed through the imaged black layer and washed out in the traditional photopolymer process requiring photography and chemicals (as discussed in the next section).
Before the year 2000, lasers only produced lower-quality results in rubber-like materials due to their rough structure. In the 2000s, fiber lasers were introduced, giving a much-increased engraving quality directly into black polymeric materials. At the Drupa 2004, the direct engraving of polymer plates was introduced. This had also an effect on the rubber developers who, in order to stay competitive, developed new high quality rubber-like materials. The development of suitable polymeric compounds has also allowed the engraving quality achievable with the fiber lasers to be realized in print. Since then, direct laser engraving of flexo-printing forms is seen by many as the modern way to make printing forms for it is the first truly digital method.
As a competitive process, more recent laser systems have been introduced to selectively engrave the thin opaque black layer of a specially produced photopolymer plate or sleeve.
Direct photopolymer laser imaging.
Closely related is the direct imaging of a digital flexo plates or sleeves "in the round" on a fast-rotating drum or cylinder. This is carried out on a platesetter integrated within a digital prepress workflow that also supports digital proofing. Again, this is a filmless process, which removes one of the variables in obtaining the fine and sharp dots for screened effects, including process color printing.
With this process, the electronically generated image is scanned at speed to a photopolymer plate material that carries a thin black mask layer on the surface. The infrared laser-imaging head, which runs parallel to the drum axis, ablates the integral mask to reveal the uncured polymer underneath. A main ultraviolet exposure follows to form the image through the mask. The remaining black layer absorbs the ultraviolet radiation, which polymerizes the underlying photopolymer where the black layer has been removed. The exposed digital plate still needs to be processed like a conventional flexo plate. That is, using solvent-based washout with the necessary waste recovery techniques, although some water-washable digital plates are in development. This technology has been used since 1995 and is only now becoming more widely used around the world as more affordable equipment becomes available. Trade sources say there are around 650 digital platesetters installed in label, packaging and trade platemaking houses.
Laser engraving of anilox rolls.
Prior to 1980 anilox rolls were produced by a variety of mechanical processes. These metal anilox rolls were sometimes sprayed with ceramic to prolong their life in the flexographic printing press. During the 1980s laser engraving systems were produced which used a carbon dioxide laser to engrave the required cell pattern directly into the polished ceramic surface. Since then Q-switched YAG lasers were used for a period as they provided a more focusable laser beam as well as increased pulsing frequencies capable of engraving the finer cell configuration demanded by the ever-evolving flexographic printing process. Since approximately the year 2000 the direct anilox laser engraving process has been dominated by the use of fibre lasers which provide the high powers of the carbon dioxide lasers together with the finely focusable beam of the YAG lasers. Optical systems providing the rapid switching of multiple beams have allowed the fibre laser system to be dominant in this market. This technology has become known as Multi-Beam-Anilox or MBA.
Sub-surface laser engraving (SSLE).
Sub-surface laser engraving is the process of engraving an image in a transparent solid material by focusing a laser below the surface to create small fractures. Such engraved materials are of high-grade optical quality (suitable for lenses, with low dispersion) to minimize distortion of the beam. BK7 glass is a common material for this application. Plastics are also used, but with far less desirable results when compared to the engraving done in optical crystal.
Since its commercial application in the late 1990s, SSLE has become more cost-effective with a number of different sized machines ranging from small (~US$35,000–60,000) to large production-scale tables (>US$250,000). Although these machines are becoming more available, it is estimated that only a few hundred are in operation worldwide. Many machines require very expensive cooling, maintenance and calibration for proper use. The more popular SSLE engraving machines use the Diode Pumped Solid State or DPSS laser process. The laser diode, the primary component which excites a pulsed solid state laser, can easily cost one third of the machine itself and functions for a limited number of hours, although a good quality diode can last thousands of hours.
Since 2009, use of SSLE has become more cost effective to produce 3D images in souvenir 'crystal' or promotional items with only a few designers concentrating on designs incorporating large or monolithic sized crystal. A number of companies offer custom-made souvenirs by taking 3D pictures or photos and engraving them into the crystal.


Thermal interface material

A thermal interface material (often abbreviated as TIM) is any material that is inserted between two components in order to enhance the thermal coupling between them. A common use is heat dissipation, in which the TIM is inserted between a heat-producing device (e.g. an integrated circuit) and a heat-dissipating device (e.g. a heat sink). At each interface, a thermal resistance exists and impedes heat dissipation. In addition, the electronic performance and device lifetime can degrade dramatically under continuous overheating and large thermal stress at the interfaces. Therefore, there have been intensive efforts to develop improved TIMs, with the aim of minimizing the thermal boundary resistance between layers and enhancing thermal management performance, as well as tackling application requirements such as low thermal stress between materials of different thermal expansion coefficients, low elastic modulus or viscosity, flexibility, and reusability. Popularly used categories of TIMs include: