Reconfigurable manufacturing system

A reconfigurable manufacturing system (RMS) is one designed at the outset for rapid change in its structure, as well as its hardware and software components, in order to quickly adjust its production capacity and functionality within a part family in response to sudden market changes or intrinsic system change.
From 1996 to 2007 Yoram Koren received an NSF grant of $32.5 million to develop the RMS science-base and its software and hardware tools, which were implemented in the automotive, aerospace, and engine factories.
The term reconfigurability in manufacturing was likely coined by Kusiak and Lee.
The RMS, as well as one of its components—the reconfigurable machine tool (RMT)—were invented in 1998 in the Engineering Research Center for Reconfigurable Manufacturing Systems (ERC/RMS) at the University of Michigan College of Engineering. The RMS goal is summarized by the statement: "Exactly the capacity and functionality needed, exactly when needed".
Ideal reconfigurable manufacturing systems possess six core RMS characteristics: modularity, integrability, customized flexibility, scalability, convertibility, and diagnosability. A typical RMS will have several of these characteristics, though not necessarily all. When possessing these characteristics, RMS increases the speed of responsiveness of manufacturing systems to unpredicted events, such as sudden market demand changes or unexpected machine failures.. The RMS facilitates a quick production launch of new products, and allows for adjustment of production quantities that might unexpectedly vary. The ideal reconfigurable system provides exactly the functionality and production capacity needed, and can be economically adjusted exactly when needed. These systems are designed and operated according to Yoram Koren's RMS principles.
The components of RMS are CNC machines, reconfigurable machine tools, reconfigurable inspection machines and material transport systems (such as gantries and conveyors) that connect the machines to form the system. Different arrangements and configurations of these machines will affect the system's productivity. A collection of mathematical tools, which are defined as the RMS science base, may be utilized to maximize system productivity with the smallest possible number of machines.
Rationale for RMS.
Globalization has created a new landscape for industry, one of fierce competition, short windows of market opportunity, and frequent changes in product demand. This change presents both a threat and an opportunity. To capitalize on the opportunity, industry needs to possess manufacturing systems that can produce a wide range of products within a product family. That range must meet the requirements of multiple countries and various cultures, not just one regional market. A design for the right mix of products must be coupled with the technical capabilities that allow for quick changeover of product mix and quantities that might vary dramatically, even on a monthly basis. Reconfigurable manufacturing systems have these capabilities.
RMS System Architecture and Operation.
The system architecture of a typical RMS is shown below.
The system is composed of stages: 10, 20, 30, 40, etc. Each stage consists of identical machines, such as CNC milling machines, or RMT machines. The system produces one product, for example, an automotive engine block or a cylinder head. The manufactured product moves on the horizontal conveyor. Then Gantry-10 grips the product and brings it to one of CNC-10. When CNC-10 finishes the processing, Gantry-10 moves it back to the conveyor. The conveyor moves the product to Gantry-20, which grips the product and load it on the RMT-20, and so on. Inspection machines are placed at several stages, and at the end of the manufacturing system.
RMS is defined as a “system designed at the outset for rapid changes in its structure.” In practice this feature is implemented by designing an open space with an access to the gantry at each stage. These spaces enable matching rapidly higher market demand by adding machines in these spaces, which increases production rate to match the demand.
The product may move during its production in many production paths. Three paths are shown in the figure. Although the CNC machines at each stage are identical, in practice there are small variations in the precision of identical machines, which create accumulated errors in the manufactured product. The magnitude of the error depends on the path in which the product moved; each path has its own “stream-of-variations” (a term coined by Y. Koren).
RMS characteristics.
Ideal reconfigurable manufacturing systems possess six core characteristics: modularity, integrability, customized flexibility, scalability, convertibility, and diagnosability. These characteristics, which were introduced by professor Yoram Koren in 1995, apply to the design of whole manufacturing systems, as well as to some of its components: reconfigurable machines, their controllers, and system control software.
Modularity refers to the modules that reconfigurable manufacturing systems consist of"." At the system level the machines are modules. At the machine level the axes of motion are modules (see the RMT Figure). The system control may be composed of control modules. Modules are easier to maintain and update.
Integrability is the ability to rapidly integrate modules by mechanical, informational, and control interfaces that enable module integration and communication.  At the system level the machines are the modules that are integrated via material transport systems (such as conveyors and gantries) to form a reconfigurable manufacturing system.
Customization allows the design of system flexibility just around a product family, obtaining thereby customized-flexibility, as opposed to the general flexibility of FMS. Customization allows a reduction in the investment cost without sacrificing performance.
Convertibility is the ability to easily transform the functionality of existing systems, machines, or controls to suit new production requirements. Examples included changing a machine in the system to another type of machine to respond to  a new required functionality, or  switching spindles on a milling machine (e.g., from low-torque high-speed spindle for aluminum to high-torque low-speed spindle for titanium).
Scalability is the ability to easily change production capacity by adding (or reducing) manufacturing resources. Scalability of a manufacturing system is increased by adding machines to expand the system production rate to match a sudden market growth. Adding machines requires extending the reach of the station gantries.
Diagnosability is the ability to automatically detect and diagnose the source of the manufactured product quality or precision defects. This automatic diagnosis  allows rapid correction of the defects. The RMS must be designed with product inspection machines embedded at optimal locations in the system.
RMS principles.
Reconfigurable manufacturing systems operate according to a set of basic principles formulated by professor Yoram Koren and are called Koren's RMS principles. The more of these principles applicable to a given manufacturing system, the more reconfigurable is that system. The RMS principles are:
RMS and FMS.
Reconfigurable manufacturing systems (RMS) and flexible manufacturing systems (FMS) have different goals. FMS aims at increasing the variety of parts produced. RMS aims at increasing the speed of responsiveness to market changes and customer's demand. RMS is also flexible, but only to a limited extent—its flexibility is confined to only that necessary to produce a part family. This is the "customized flexibility" or the customization characteristic, which is not the general flexibility that FMS offers. The customized flexibility enables higher production rates. Other important advantages of RMS are rapid scalability to the desired volume, and convertibility, which are obtained within reasonable cost to manufacturers. The best application of FMS is found in production of small sets of products [see Wikipedia].
RMS science base.
The RMS technology is based on a systematic approach to the design and operation of reconfigurable manufacturing systems. The approach consists of key elements, the compilation of which is called the RMS science base. These elements are summarized below.


Water jet cutter

A water jet cutter, also known as a water jet or waterjet, is an industrial tool capable of cutting a wide variety of materials using an extremely high-pressure jet of water, or a mixture of water and an abrasive substance. The term abrasive jet refers specifically to the use of a mixture of water and an abrasive to cut hard materials such as metal, stone or glass, while the terms pure waterjet and water-only cutting refer to waterjet cutting without the use of added abrasives, often used for softer materials such as wood or rubber.
Waterjet cutting is often used during the fabrication of machine parts. It is the preferred method when the materials being cut are sensitive to the high temperatures generated by other methods; examples of such materials include plastic and aluminium. Waterjet cutting is used in various industries, including mining and aerospace, for cutting, shaping, and reaming.
History.
Waterjet.
While using high-pressure water for erosion dates back as far as the mid-1800s with hydraulic mining, it was not until the 1930s that narrow jets of water started to appear as an industrial cutting device. In 1933, the Paper Patents Company in Wisconsin developed a paper metering, cutting, and reeling machine that used a diagonally moving waterjet nozzle to cut a horizontally moving sheet of continuous paper. These early applications were at low pressure and restricted to soft materials like paper.
Waterjet technology evolved in the post-war era as researchers around the world searched for new methods of efficient cutting systems. In 1956, Carl Johnson of Durox International in Luxembourg developed a method for cutting plastic shapes using a thin stream high-pressure water jet, but those materials, like paper, were soft materials. In 1958, Billie Schwacha of North American Aviation developed a system using ultra-high-pressure liquid to cut hard materials. This system used a pump to deliver a hypersonic liquid jet that could cut high-strength alloys such as PH15-7-MO stainless steel. Used to cut honeycomb laminate for the Mach 3 North American XB-70 Valkyrie, this cutting method resulted in delaminating at high speed, requiring changes to the manufacturing process.
While not effective for the XB-70 project, the concept was valid and further research continued to evolve waterjet cutting. In 1962, Philip Rice of Union Carbide explored using a pulsing waterjet at up to to cut metals, stone, and other materials. Research by S.J. Leach and G.L. Walker in the mid-1960s expanded on traditional coal waterjet cutting to determine the ideal nozzle shape for high-pressure waterjet cutting of stone, and Norman Franz in the late 1960s focused on waterjet cutting of soft materials by dissolving long-chain polymers in the water to improve the cohesiveness of the jet stream. In the early 1970s, the desire to improve the durability of the waterjet nozzle led Ray Chadwick, Michael Kurko, and Joseph Corriveau of the Bendix Corporation to come up with the idea of using corundum crystal to form a waterjet orifice, while Norman Franz expanded on this and created a waterjet nozzle with an orifice as small as that operated at pressures up to . John Olsen, along with George Hurlburt and Louis Kapcsandy at Flow Research (later Flow Industries), further improved the commercial potential of the water jet by showing that treating the water beforehand could increase the operational life of the nozzle.
High pressure.
High-pressure vessels and pumps became affordable and reliable with the advent of steam power. By the mid-1800s, steam locomotives were common and the first efficient steam-driven fire engine was operational. By the turn of the century, high-pressure reliability improved, with locomotive research leading to a sixfold increase in boiler pressure, some reaching . Most high-pressure pumps at this time, though, operated around .
High-pressure systems were further shaped by the aviation, automotive, and oil industries. Aircraft manufacturers such as Boeing developed seals for hydraulically boosted control systems in the 1940s, while automotive designers followed similar research for hydraulic suspension systems. Higher pressures in hydraulic systems in the oil industry also led to the development of advanced seals and packing to prevent leaks.
These advances in seal technology, plus the rise of plastics in the post-war years, led to the development of the first reliable high-pressure pump. The invention of Marlex by Robert Banks and John Paul Hogan of the Phillips Petroleum Company required a catalyst to be injected into the polyethylene. McCartney Manufacturing Company in Baxter Springs, Kansas, began manufacturing these high-pressure pumps in 1960 for the polyethylene industry. Flow Industries in Kent, Washington set the groundwork for commercial viability of waterjets with John Olsen’s development of the high-pressure fluid intensifier in 1973, a design that was further refined in 1976. Flow Industries then combined the high-pressure pump research with their waterjet nozzle research and brought waterjet cutting into the manufacturing world.
Abrasive waterjet.
While cutting with water is possible for soft materials, adding an abrasive turned the water jet into a modern machining tool for all materials. This began in 1935 when the idea of adding an abrasive to the water stream was developed by Elmo Smith for liquid abrasive blasting. Smith’s design was further refined by Leslie Tirrell of the Hydroblast Corporation in 1937, resulting in a nozzle design that created a mix of high-pressure water and abrasive for the purpose of wet blasting.
The first publications on modern abrasive waterjet (AWJ) cutting were published by Mohamed Hashish in the 1982 BHR proceedings showing, for the first time, that waterjets with relatively small amounts of abrasives are capable of cutting hard materials such as steel and concrete. The March 1984 issue of the Mechanical Engineering magazine showed more details and materials cut with AWJ such as titanium, aluminium, glass, and stone. Mohamed Hashish was awarded a patent on forming AWJ in 1987. Hashish, who also coined the new term "abrasive waterjet", and his team continued to develop and improve the AWJ technology and its hardware for many applications. A critical development was creating a durable mixing tube that could withstand the power of the high-pressure AWJ, and it was Boride Products (now Kennametal) development of their ROCTEC line of ceramic tungsten carbide composite tubes that significantly increased the operational life of the AWJ nozzle. Current work on AWJ nozzles is on micro abrasive waterjets so that cutting with jets smaller than in diameter can be commercialized.
Working with Ingersoll-Rand Waterjet Systems, Michael Dixon implemented the first production practical means of cutting titanium sheets—an abrasive waterjet system very similar to those in widespread use today. By January 1989, that system was being run 24 hours a day producing titanium parts for the B-1B largely at Rockwell's North American Aviation facility in Newark, Ohio.
Today, there are two different types of Abrasive Waterjets:
Abrasive Water Suspension Jet (AWSJ) cutting.
The Abrasive Water Suspension Jet (AWSJ) - often called “Slurry Jet” or “Water Abrasive Suspension (WAS) jet” - is a specific type of abrasive water jet, which is used for waterjet cutting. In contrast to the abrasive water injector jet (AWIJ), the abrasive water suspension jet (AWSJ) is characterised by the fact that the mixing of abrasive and water takes place before the nozzle. This has the effect that, in contrast to AWIJ, the jet consists of only two components: the water and the abrasive.
Since there are only 2 components (water and abrasive) in the AWSJ, the acceleration of the abrasive grains by the water takes place with a significantly increased efficiency compared to the AWIJ. The abrasive grains become faster with the WASS than with the WAIS for the same hydraulic power of the system. Therefore, comparatively deeper or faster cuts can be made with the AWSJ.
AWSJ cutting, in contrast to the AWIJ cutting process described below, can also be used for mobile cutting applications and cutting underwater, in addition to machining demanding materials. Examples include bomb disposal s well as the dismantling of offshore installations or the dismantling of reactor pressure vessel installations in nuclear power plants.
Abrasive Water Injector Jet (AWIJ) cutting.
The AWIJ is generated by a water jet that passes through a mixing chamber (a cavity) after exiting the water nozzle and enters a focusing tube at the exit of the mixing chamber. The interaction of the water jet in the mixing chamber with the air inside creates negative pressure, the water jet entrains air particles. This negative pressure is used for the pneumatic transport of the abrasive into the chamber (the abrasive is led to a lateral opening (bore) of the mixing chamber by means of a hose).
After contact with the abrasive material in the mixing chamber with the water jet, the individual abrasive grains are accelerated and entrained in the direction of the focusing tube. The air used as a carrier medium for transporting the abrasive into the mixing chamber also becomes part of the AWIJ, which now consists of three components (water - abrasive - air). In the focusing tube, which is (should be) optimised in its length for this purpose, the abrasive is further accelerated (energy transfer from the water to the abrasive grain) and the AWIJ ideally leaves the focusing tube at the maximum possible abrasive grain speed.
Waterjet control.
As waterjet cutting moved into traditional manufacturing shops, controlling the cutter reliably and accurately was essential. Early waterjet cutting systems adapted traditional systems such as mechanical pantographs and CNC systems based on John Parsons’ 1952 NC milling machine and running G-code. Challenges inherent to waterjet technology revealed the inadequacies of traditional G-Code. The accuracy depends on varying the speed of the nozzle as it approaches corners and details. Creating motion control systems to incorporate those variables became a major innovation for leading waterjet manufacturers in the early 1990s, with John Olsen of OMAX Corporation developing systems to precisely position the waterjet nozzle while accurately specifying the speed at every point along the path, and also utilizing common PCs as a controller. The largest waterjet manufacturer, Flow International (a spinoff of Flow Industries), recognized the benefits of that system and licensed the OMAX software, with the result that the vast majority of waterjet cutting machines worldwide are simple to use, fast, and accurate.
Operation.
All waterjets follow the same principle of using high-pressure water focused into a beam by a nozzle. Most machines accomplish this by first running the water through a high-pressure pump. There are two types of pumps used to create this high pressure; an intensifier pump and a direct drive or crankshaft pump. A direct drive pump works much like a car engine, forcing water through high-pressure tubing using plungers attached to a crankshaft. An intensifier pump creates pressure by using hydraulic oil to move a piston forcing the water through a tiny hole. The water then travels along the high-pressure tubing to the nozzle of the waterjet. In the nozzle, the water is focused into a thin beam by a jewel orifice. This beam of water is ejected from the nozzle, cutting through the material by spraying it with the jet of speed on the order of Mach 3, around . The process is the same for abrasive waterjets until the water reaches the nozzle. Here abrasives such as garnet and aluminium oxide, are fed into the nozzle via an abrasive inlet. The abrasive then mixes with the water in a mixing tube and is forced out the end at high pressure.
Benefits.
An important benefit of the water jet is the ability to cut material without interfering with its inherent structure, as there is no "heat-affected zone" (HAZ). Minimizing the effects of heat allows metals to be cut without warping, affecting tempers, or changing intrinsic properties. Sharp corners, bevels, pierce holes, and shapes with minimal inner radii are all possible.
Water jet cutters are also capable of producing intricate cuts in material. With specialized software and 3-D machining heads, complex shapes can be produced.
The kerf, or width, of the cut can be adjusted by swapping parts in the nozzle, as well as changing the type and size of the abrasive. Typical abrasive cuts have a kerf in the range of , but can be as narrow as . Non-abrasive cuts are normally , but can be as small as , which is approximately that of a human hair. These small jets can permit small details in a wide range of applications.
Water jets are capable of attaining accuracy down to and repeatability down to .
Due to its relatively narrow kerf, water jet cutting can reduce the amount of scrap material produced, by allowing uncut parts to be nested more closely together than traditional cutting methods. Water jets use approximately per minute (depending on the cutting head's orifice size), and the water can be recycled using a closed-loop system. Waste water usually is clean enough to filter and dispose of down a drain. The garnet abrasive is a non-toxic material that can be mostly recycled for repeated use; otherwise, it can usually be disposed of in a landfill. Water jets also produce fewer airborne dust particles, smoke, fumes, and contaminants, reducing operator exposure to hazardous materials.
Meatcutting using waterjet technology eliminates the risk of cross contamination since the contact medium is discarded.
Versatility.
Because the nature of the cutting stream can be easily modified the water jet can be used in nearly every industry; there are many different materials that the water jet can cut. Some of them have unique characteristics that require special attention when cutting.
Materials commonly cut with a water jet include textiles, rubber, foam, plastics, leather, composites, stone, tile, glass, metals, food, paper and much more. "Most ceramics can also be cut on an abrasive water jet as long as the material is softer than the abrasive being used (between 7.5 and 8.5 on the Mohs scale)". Examples of materials that cannot be cut with a water jet are tempered glass and diamonds. Water jets are capable of cutting up to of metals and of most materials, though in specialized coal mining applications, water jets are capable of cutting up to using a nozzle.
Specially designed water jet cutters are commonly used to remove excess bitumen from road surfaces that have become the subject of binder flushing. Flushing is a natural occurrence caused during hot weather where the aggregate becomes level with the bituminous binder layer creating a hazardously smooth road surface during wet weather.
Availability.
Commercial water jet cutting systems are available from manufacturers all over the world, in a range of sizes, and with water pumps capable of a range of pressures. Typical water jet cutting machines have a working envelope as small as a few square feet, or up to hundreds of square feet. Ultra-high-pressure water pumps are available from as low as up to .
Process.
There are six main process characteristics of water jet cutting:
Temperature is not much of a factor because the water used also acts as a coolant.
Edge quality.
Edge quality for water jet cut parts is defined with the quality numbers Q1 through Q5. Lower numbers indicate rougher edge finish; higher numbers are smoother. For thin materials, the difference in cutting speed for Q1 could be as much as 3 times faster than the speed for Q5. For thicker materials, Q1 could be 6 times faster than Q5. For example, thick aluminium Q5 would be and Q1 would be , 5.8 times faster.
Multi-axis cutting.
In 1987, Ingersoll-Rand Waterjet Systems offered a 5-axis pure-water waterjet cutting system called the Robotic Waterjet System. The system was an overhead gantry design, similar in overall size to the HS-1000.
With recent advances in control and motion technology, 5-axis water jet cutting (abrasive and pure) has become a reality. Where the normal axes on a water jet are named Y (back/forth), X (left/right) and Z (up/down), a 5-axis system will typically add an A axis (angle from perpendicular) and C axis (rotation around the Z-axis). Depending on the cutting head, the maximum cutting angle for the A axis can be anywhere from 55, 60, or in some cases even 90 degrees from vertical. As such, 5-axis cutting opens up a wide range of applications that can be machined on a water jet cutting machine.
A 5-axis cutting head can be used to cut 4-axis parts, where the bottom surface geometries are shifted a certain amount to produce the appropriate angle and the Z-axis remains at one height. This can be useful for applications like weld preparation where a bevel angle needs to be cut on all sides of a part that will later be welded, or for taper compensation purposes where the kerf angle is transferred to the waste material – thus eliminating the taper commonly found on water jet-cut parts. A 5-axis head can cut parts where the Z-axis is also moving along with all the other axes. This full 5-axis cutting could be used for cutting contours on various surfaces of formed parts.
Because of the angles that can be cut, part programs may need to have additional cuts to free the part from the sheet. Attempting to slide a complex part at a severe angle from a plate can be difficult without appropriate relief cuts.


Ujiarpur Assembly constituency

Ujiarpur Assembly constituency is an assembly constituency in Samastipur district in the Indian state of Bihar. The constituency was formed following the Delimitation Order of 2008.
Overview.
As per Delimitation of Parliamentary and Assembly constituencies Order, 2008, No. 134 Ujiarpur Assembly constituency is composed of the following: Ujiarpur community development block; Sultanpur Ghataho,
Chakbahauddin, Mokhtiyarpur Salkhani, Panr, Harishankarpur, Kewanta, Nagargama, Pagra, Nawada, Basariya gram panchayats and Dalsinghsarai notified area of Dalsinghsarai CD Block.
Ujiarpur Assembly constituency is part of No. 22 Ujiarpur (Lok Sabha constituency).
Election results.
2015.
In the 2015 state assembly elections, Alok Kumar Mehta of RJD won the newly constituted Ujiarpur seat.


Electronic packaging

Electronic packaging is the design and production of enclosures for electronic devices ranging from individual semiconductor devices up to complete systems such as a mainframe computer. Packaging of an electronic system must consider protection from mechanical damage, cooling, radio frequency noise emission and electrostatic discharge. Product safety standards may dictate particular features of a consumer product, for example, external case temperature or grounding of exposed metal parts. Prototypes and industrial equipment made in small quantities may use standardized commercially available enclosures such as card cages or prefabricated boxes. Mass-market consumer devices may have highly specialized packaging to increase consumer appeal. Electronic packaging is a major discipline within the field of mechanical engineering.
Design.
Electronic packaging can be organized by levels:
The same electronic system may be packaged as a portable device or adapted for fixed mounting in an instrument rack or permanent installation. Packaging for aerospace, marine, or military systems imposes different types of design criteria.
Electronic packaging relies on mechanical engineering principles such as dynamics, stress analysis, heat transfer and fluid mechanics. High-reliability equipment often must survive drop tests, loose cargo vibration, secured cargo vibration, extreme temperatures, humidity, water immersion or spray, rain, sunlight (UV, IR and visible light), salt spray, explosive shock, and many more. These requirements extend beyond and interact with the electrical design.
An electronics assembly consists of component devices, circuit card assemblies (CCAs), connectors, cables and components such as transformers, power supplies, relays, switches, etc. that may not mount on the circuit card.
Many electrical products require the manufacturing of high-volume, low-cost parts such as enclosures or covers by techniques such as injection molding, die casting, investment casting, and so on. The design of these products depends on the production method and require careful consideration of dimensions and tolerances and tooling design. Some parts may be manufactured by specialized processes such as plaster- and sand-casting of metal enclosures.
In the design of electronic products, electronic packaging engineers perform analyses to estimate such things as maximum temperatures for components, structural resonant frequencies, and dynamic stresses and deflections under worst-case environments. Such knowledge is important to prevent immediate or premature electronic product failures.
Design considerations.
A designer must balance many objectives and practical considerations when selecting packaging methods.
Packaging materials.
Sheet metal.
Punched and formed sheet metal is one of the oldest types of electronic packaging. It can be mechanically strong, provides electromagnetic shielding when the product requires that feature, and is easily made for prototypes and small production runs with little custom tooling expense.
Cast metal.
Gasketed metal castings are sometimes used to package electronic equipment for exceptionally severe environments, such as in heavy industry, aboard ship, or deep under water. Aluminum die castings are more common than iron or steel sand castings.
Machined metal.
Electronic packages are sometimes made by machining solid blocks of metal, usually aluminum, into complex shapes. They are fairly common in microwave assemblies for aerospace use, where precision transmission lines require complex metal shapes, in combination with hermetically sealed housings. Quantities tend to be small; sometimes only one unit of a custom design is required. Piece part costs are high, but there is little or no cost for custom tooling, and first-piece deliveries can take as little as half a day. The tool of choice is a numerically controlled vertical milling machine, with automatic translation of computer-aided design (CAD) files to toolpath command files.
Molded plastic.
Molded plastic cases and structural parts can be made by a variety of methods, offering tradeoffs in piece part cost, tooling cost, mechanical and electrical properties, and ease of assembly. Examples are injection molding, transfer molding, vacuum forming, and die cutting. Pl can be post-processed to provide conductive surfaces.
Potting.
Also called "encapsulation", potting consists of immersing the part or assembly in a liquid resin, then curing it. Another method puts the part or assembly in a mold, and potting compound is poured in it, and after curing, the mold is not removed, becoming part of the part or assembly. Potting can be done in a pre-molded potting shell, or directly in a mold. Today it is most widely used to protect semiconductor components from moisture and mechanical damage, and to serve as a mechanical structure holding the lead frame and the chip together. In earlier times it was often used to discourage reverse engineering of proprietary products built as printed circuit modules. It is also commonly used in high voltage products to allow live parts to be placed closer together (eliminating corona discharges due to the potting compound's high dielectric strength), so that the product can be smaller. This also excludes dirt and conductive contaminants (such as impure water) from sensitive areas. Another use is to protect deep-submergence items such as sonar transducers from collapsing under extreme pressure, by filling all voids. Potting can be rigid or soft. When void-free potting is required, it is common practice to place the product in a vacuum chamber while the resin is still liquid, hold a vacuum for several minutes to draw the air out of internal cavities and the resin itself, then release the vacuum. Atmospheric pressure collapses the voids and forces the liquid resin into all internal spaces. Vacuum potting works best with resins that cure by polymerization, rather than solvent evaporation.
Porosity sealing or impregnation.
Porosity Sealing or Resin Impregnation is similar to potting, but doesn't use a shell or a mold. Parts are submerged in a polymerizable monomer or solvent-based low viscosity plastic solution. The pressure above the fluid is lowered to a full vacuum. After the vacuum is released, the fluid flows into the part. When the part is withdrawn from the resin bath, it is drained and/or cleaned and then cured. Curing can consist of polymerizing the internal resin or evaporating the solvent, which leaves an insulating dielectric material between different voltage components. Porosity sealing (Resin Impregnation) fills all interior spaces, and may or may not leave a thin coating on the surface, depending on the wash/rinse performance. The main application of vacuum impregnation porosity sealing is in boosting the dielectric strength of transformers, solenoids, lamination stacks or coils, and some high voltage components. It prevents ionization from forming between closely spaced live surfaces and initiating failure.
Liquid filling.
Liquid filling is sometimes used as an alternative to potting or impregnation. It's usually a dielectric fluid, chosen for chemical compatibility with the other materials present. This method is used mostly in very large electrical equipment such as utility transformers, to increase breakdown voltage. It can also be used to improve heat transfer, especially if allowed to circulate by natural convection or forced convection through a heat exchanger. Liquid filling can be removed for repair much more easily than potting.
Conformal coating.
Conformal coating is a thin insulating coating applied by various methods. It provides mechanical and chemical protection of delicate components. It's widely used on mass-produced items such as axial-lead resistors, and sometimes on printed circuit boards. It can be very economical, but somewhat difficult to achieve consistent process quality.
Glob-top.
Glob-top is a variant of conformal coating used in chip-on-board assembly (COB). It consists of a drop of specially formulated epoxy or resin deposited over a semiconductor chip and its wire bonds, to provide mechanical support and exclude contaminants such as fingerprint residues which could disrupt circuit operation. It is most commonly used in electronic toys and low-end devices.
Chip on board.
Surface-mounted LEDs are frequently sold in chip-on-board (COB) configurations. In these, the individual diodes are mounted in an array that allows the device to produce a greater amount of luminous flux with greater ability to dissipate the resulting heat in an overall smaller package than can be accomplished by mounting LEDs, even surface mount types, individually on a circuit board.
Hermetic metal/glass cases.
Hermetic metal packaging began life in the vacuum tube industry, where a totally leak-proof housing was essential to operation. This industry developed the glass-seal electrical feedthrough, using alloys such as Kovar to match the coefficient of expansion of the sealing glass so as to minimize mechanical stress on the critical metal-glass bond as the tube warmed up. Some later tubes used metal cases and feedthroughs, and only the insulation around the individual feedthroughs used glass. Today, glass-seal packages are used mostly in critical components and assemblies for aerospace use, where leakage must be prevented even under extreme changes in temperature, pressure, and humidity.
Hermetic ceramic packages.
Packages consisting of a lead frame embedded in a vitreous paste layer between flat ceramic top and bottom covers are more convenient than metal/glass packages for some products, but give equivalent performance. Examples are integrated circuit chips in ceramic Dual In-line Package form, or complex hybrid assemblies of chip components on a ceramic base plate. This type of packaging can also be divided into two main types: multilayer ceramic packages (like LTCC and HTCC) and pressed ceramic packages.
Printed circuit assemblies.
Printed circuits are primarily a technology for connecting components together, but they also provide mechanical structure. In some products, such as computer accessory boards, they're all the structure there is. This makes them part of the universe of electronic packaging.
Reliability evaluation.
A typical reliability qualification includes the following types of environmental stresses:
Hygrothermal test is performed in chambers with temperature and humidity. It is an environmental stress test used in evaluating product reliability. The typical hygrothermal test is 85˚C temperature and 85% relative humidity (abbr. 85˚C/85%RH). During the test, the sample is periodically taken out to test its mechanical or electrical properties. Some research works related to hygrothermal test can be seen in the references.


Head restraint

Head restraints (also called headrests) are an automotive safety feature, attached or integrated into the top of each seat to limit the rearward movement of the adult occupant's head, relative to the torso, in a collision — to prevent or mitigate whiplash or injury to the cervical vertebrae. Since their mandatory introduction in some countries beginning in the late 1960s, head restraints have prevented or mitigated thousands of serious injuries.
A patent for an automobile "headrest" was granted to Benjamin Katz, a resident of Oakland, California, in 1921. Additional patents for such devices were issued in 1930 and in 1950, and subsequently. The major U. K. supplier of head restraints, Karobes, filed patents in the late 1950s and was still competitive in 1973 when British tests evaluated the quality of these devices.
Optional head restraints began appearing on North American cars in the mid-1960s, and were mandated by the U.S. National Highway Traffic Safety Administration (NHTSA) in all new cars sold in the U.S. after January 1, 1969. The U.S. regulation, called Federal Motor Vehicle Safety Standard 202, requires that head restraints meet one of the following two standards of performance, design, and construction:
An evaluation performed by NHTSA in 1982 on passenger cars found that "integral" head restraints—a seat back extending high enough to meet the height requirement—reduces injury by 17 percent, while adjustable head restraints, attached to the seat back by one or more sliding metal shafts, reduce injury by 10 percent. NHTSA has said this difference may be due to adjustable restraints being improperly positioned.
Reason for discomfort.
Headrests are uncomfortable when they push the head forward. In such case there is effectively no gap behind the head and the headrest, or more technically, there's a 'negative' backset (or gap) as the headrest interferes with their natural neutral posture. Data shows that 16% of the population will experience headrest discomfort because of this issue. The rest of the population experiences no discomfort because there is no contact with the headrest, i.e. there is a gap between the head and headrest.
Headrests are designed this way because the regulated specs for headrests are set for the 'average' body posture. When the U.S. National Highway Traffic Safety Administration (NHTSA) revised the standard which governs head restraints for all new cars manufactured after 2008, it established for the first time a requirement for the fore-aft position, or "backset". The backset requirements was set at a 55mm (2.1 in) gap behind the head of the "average" body posture. By definition, not everyone has the 'average' posture. The specs will therefore cause issues for this 16% subset of the population.
Whiplash protection.
The focus of preventive measures to date has been on the design of car seats, primarily through the introduction of head restraints, often called headrests. This approach is potentially problematic given the underlying assumption that purely mechanical factors cause whiplash injuries — an unproven theory. So far the injury reducing effects of head restraints appears to have been low, approximately 5–10%, because car seats have become stiffer in order to increase crashworthiness of cars in high-speed rear-end collisions which in turn could increase the risk of whiplash injury in low-speed rear impact collisions. Improvements in the geometry of car seats through better design and energy absorption could offer additional benefits. Active devices move the body in a crash in order to shift the loads on the car seat.
For the last 40 years, vehicle safety researchers have been designing and gathering information on the ability of head restraints to mitigate injuries resulting from rear-end collisions. As a result, different types of head restraints have been developed by various manufacturers to protect their occupants from whiplash.
Below are definitions of different types of head restraints.
Head restraint — refers to a device designed to limit the rearward displacement of an adult occupant's head in relation to the torso in order to reduce the risk of injury to the cervical vertebrae in the event of a rear impact. The most effective head restraint must allow a backset motion of less than 60 mm to prevent the hyperextension of the neck during impact.
Integrated head restraint or fixed head restraint — refers to a head restraint formed by the upper part of the seat back, or a head restraint that is not height adjustable and cannot be detached from the seat or the vehicle structure except by the use of tools or following the partial or total removal of the seat furnishing”.
Adjustable head restraint — refers to a head restraint that is capable of being positioned to fit the morphology of the seated occupant. The device may permit horizontal displacement, known as tilt adjustment, and/or vertical displacement, known as height adjustment.
Active head restraint — refers to a device designed to automatically improve head restraint position and/or geometry during an impact.
Automatically adjusting head restraint — refers to a head restraint that automatically adjusts the position of the head restraint when the seat position is adjusted.
A major issue in whiplash prevention is the lack of proper adjustment of the seat safety system by both drivers and passengers. Studies have shown that a well designed and adjusted head restraint could prevent potentially injurious head-neck kinematics in rear-end collisions by limiting the differential movement of the head and torso. The primary function of a head restraint is to minimize the relative rearward movement of the head and neck during rear impact. During a rear-end collision, the presence of an effective head restraint behind the occupant's head can limit the differential movement of the head and torso. A properly placed head restraint where one can sufficiently protect one's head lower the chances of neck injury by up to 43% during a rear-end collision.
In contrast to a properly adjusted head restraint, research suggests that there may be an increased risk of neck injuries if the head restraint is incorrectly positioned. More studies by manufacturers and automobile safety organizations are currently undergoing to examine the best ways to reduce head and torso injuries during a rear-end impact with different geometries of the head restraint and seat-back systems.
In most passenger vehicles where manually adjustable head restraints are fitted, proper use requires sufficient knowledge and awareness by occupants. When driving, the height of the head restraint is critical in influencing injury risk. A restraint should be at least as high as the head's center of gravity, or about 9 centimeters (3.5 inches) below the top of the head. The backset, or distance behind the head, should be as small as possible. Backsets of more than 10 centimeters (about 4 inches) have been associated with increased symptoms of neck injury in crashes.
Due to low public awareness of the consequence of incorrect positioning of head restraints, some passenger vehicle manufactures have designed and implemented a range of devices into their models to protect their occupants.
Some current systems are:
The Insurance Institute for Highway Safety (IIHS) and other testing centers around the world have been involved in testing the effectiveness of head restraint and seat systems in laboratory conditions to assess their ability to prevent or mitigate whiplash injuries. They have found that over 60% of new motor vehicles on the market have “good” rated head restraints.


Jig grinder

A jig grinder is a machine tool used for grinding complex shapes and holes where the highest degrees of accuracy and finish are required.
The jig grinder is very similar to a jig borer, in that the table positioning and spindles are very accurate (far more so than a manual milling machine or lathe). It is almost exclusively used by tool and die makers in the creation of jigs or mating holes and pegs on dies. There are usually many peripheral elements to a large jig grinder, including separate hydraulic motors, air compressors, and various cooling systems for both the hydraulic circuit and supplying coolant to the work and machine itself.
The machine operates by a high speed air spindle rotating a grinding bit. The air spindles are removable and interchangeable to achieve varying surface speeds. Some spindles are fixed speed (60,000 rpm), others are adjustable (30,000-50,000 rpm), and still others are very high speed (175,000 rpm). The machines have a standard X-Y table with the notable exception of knee travel. All axes are indexed to 0.0001" via a vernier scale on the handwheels, with higher accuracy available with the use of measuring bars. The machine head has two vertical travels, one rough head adjustment and the other a precise spindle adjustment. To change the diameter of the hole to be ground the air spindle can be offset from the axis of the rotary head by a slide in a similar manner to a boring head for a milling machine, allowing a hole of any size to be ground with the same tooling (up to the machine's capacity). This offset can be adjusted while running and can typically outfeed about 0.100", again with an accuracy of 0.0001" on the handwheel or greater, for very precise hole, peg and surface grinding. A well-kept jig grinder will reliably position work to a higher degree of accuracy than is possible with handwheels alone. These features are all critical in positioning a hole and peg system a precise distance from a reference surface or edge.
The most important factor on a jig grinder is the dual-spindle configuration. The main spindle is roughly positioned with between 1" or 2" of travel for setup, and then the 0.100" of outfeed is used during machine operation to outfeed into the work. A spacer bar may be used between the grinder and main spindle, allowing large (9" radius or larger) work to be completed. The main spindle has a wide range of speeds to ensure proper grinder feed rates are maintained.
On October 19, 2022, the United States Department of Justice charged four individuals and two companies with violating U.S. export laws by attempting to smuggle a jig grinder, which is a dual use, export-controlled item, to Russia.


Gear cutting

Gear cutting is any machining process for creating a gear. The most common gear-cutting processes include hobbing, broaching, milling, grinding, and skiving. Such cutting operations may occur either after or instead of forming processes such as forging, extruding, investment casting, or sand casting.
Gears are commonly made from metal, plastic, and wood. Although gear cutting is a substantial industry, many metal and plastic gears are made without cutting, by processes such as die casting or injection molding. Some metal gears made with powder metallurgy require subsequent machining, whereas others are complete after sintering. Likewise, metal or plastic gears made with additive manufacturing may or may not require finishing by cutting, depending on application.
Processes.
Broaching.
For very large gears or spline, a vertical broach is used. It consists of a vertical rail that carries a single tooth cutter formed to create the tooth shape. A rotary table and a Y axis are the customary axes available. Some machines will cut to a depth on the Y axis and index the rotary table automatically. The largest gears are produced on these machines.
Other operations such as broaching work particularly well for cutting teeth on the inside. The downside to this is that it is expensive and different broach sticks are required to make different sized gears. Therefore, it is mostly used in very high production runs.
Hobbing.
Hobbing is a method by which a "hob" is used to cut teeth into a blank. We gear hobbing with a master hob or index hob on CNC gear hobbing machines who cut, gears, wheels, pinions, shafts and worms. The cutter and gear blank are rotated at the same time to transfer the profile of the hob onto the gear blank. Used very often for all sizes of production runs, but works best for medium to high. The hobbing features for gears are straight, helical, straight bevel, face, crowned, worm, cylkro and chamfering.
Milling or grinding.
Spur may be cut or ground on a milling machine or jig grinder utilizing a numbered gear cutter, and any indexing head or rotary table. The number of the gear cutter is determined by the tooth count of the gear to be cut.
To machine a helical gear on a manual machine, a true indexing fixture must be used. Indexing fixtures can disengage the drive worm, and be attached via an external gear train to the machine table's handle (like a power feed). It then operates similarly to a carriage on a lathe. As the table moves on the X axis, the fixture will rotate in a fixed ratio with the table. The indexing fixture itself receives its name from the original purpose of the tool: moving the table in precise, fixed increments. If the indexing worm is not disengaged from the table, one can move the table in a highly controlled fashion via the indexing plate to produce linear movement of great precision (such as a vernier scale).
There are a few different types of cutters used when creating gears. One is a rack shaper. These are straight and move in a direction tangent to the gear, while the gear. They have six to twelve teeth and eventually have to be moved back to the starting point to begin another cut.
Shaping.
The old method of gear cutting is mounting a gear blank in a shaper and using a tool shaped in the profile of the tooth to be cut. This method also works for cutting internal splines.
Another is a pinion-shaped cutter that is used in a gear shaper machine. It is basically when a cutter that looks similar to a gear cuts a gear blank. The cutter and the blank must have a rotating axis parallel to each other. This process works well for low and high production runs.
Finishing.
After being cut the gear can be finished by shaving, burnishing, grinding, honing or lapping.
Further reading.
A guide to cutting; by Zuber Beekhory


Glass-filled polymer

Glass-filled polymer (or glass-filled plastic), is a mouldable composite material. It comprises short glass fibers in a matrix of a polymer material. It is used to manufacture a wide range of structural components by injection or compression moulding. It is an ideal glass alternative that offers flexibility in the part, chemical resistance, shatter resistance and overall better durability.
Materials.
Either thermoplastic or thermosetting polymers may be used. One of the most widely used thermoplastics is a polyamide polymer nylon.
The first mouldable composite was Bakelite. This used wood flour fibres in phenolic resin as the thermoset polymer matrix. As the fibres were only short this material had relatively low bulk strength, but still improved surface hardness and good mouldability.
A wide range of polymers are now produced in glass-filled varieties, including polyamide (Nylon), acetal homopolymers and copolymers, polyester, polyphenylene oxide (PPO / Noryl), polycarbonate, polyethersulphone
Bulk moulding compound is a pre-mixed material of resin and fibres supplied for moulding. Some are thermoplastic or thermosetting, others are chemically cured and are mixed with a catalyst (polyester) or hardener (epoxy) before moulding.
Applications.
Compared to the native polymer, glass-filled materials have improved mechanical properties of rigidity, strength and may also have improved surface hardness.
Compared to sheet materials.
Bulk glass "filled" materials are considered distinct from fibreglass or fibre-reinforced plastic materials. These use a substrate of fabric sheets made from long fibres, draped to shape in a mould and then impregnated with resin. They are usually moulded into shapes made of large but thin sheets. Filled materials, in contrast, are used for applications that are thicker or of varying section and not usually as large as sheet materials.


Fused filament fabrication

Fused filament fabrication (FFF), also known as fused deposition modeling (with the trademarked acronym FDM), or "filament freeform fabrication", is a 3D printing process that uses a continuous filament of a thermoplastic material. Filament is fed from a large spool through a moving, heated printer extruder head, and is deposited on the growing work. The print head is moved under computer control to define the printed shape. Usually the head moves in two dimensions to deposit one horizontal plane, or layer, at a time; the work or the print head is then moved vertically by a small amount to begin a new layer. The speed of the extruder head may also be controlled to stop and start deposition and form an interrupted plane without stringing or dribbling between sections. "Fused filament fabrication" was coined by the members of the RepRap project to give an acronym (FFF) that would be legally unconstrained in its use.
Fused filament printing is now the most popular process (by number of machines) for hobbyist-grade 3D printing. Other techniques such as photopolymerisation and powder sintering may offer better results, but they are much more costly.
The 3D printer head or 3D printer extruder is a part in material extrusion additive manufacturing responsible for raw material melting or softening and forming it into a continuous profile. A wide variety of filament materials are extruded, including thermoplastics such as "acrylonitrile butadiene styrene" (ABS), "polylactic acid" (PLA), "polyethylene terephthalate glycol" (PETG), "polyethylene terephthalate" (PET), high-impact "polystyrene" (HIPS), "thermoplastic polyurethane" (TPU) and "aliphatic polyamides" (nylon).
History.
Fused deposition modeling was developed by S. Scott Crump, co-founder of Stratasys, in 1988. With the 2009 expiration of the patent on this technology, people could use this type of printing without paying Stratasys for the right to do so, opening up commercial, DIY, and open-source (RepRap) 3D printer applications. This has led to a two-orders-of-magnitude price drop since this technology's creation. Stratasys still owns the trademark on the term "FDM".
Process.
3D printing, also referred to as additive manufacturing (AM), involves manufacturing a part by depositing material layer by layer. There is a wide array of different AM technologies that can do this, including material extrusion, binder jetting, material jetting and directed energy deposition. These processes have varied types of extruders and extrude different materials to achieve the final product.
Material extrusion.
Fused filament fabrication uses material extrusion to print items, where a feedstock material is pushed through an extruder. In most fused filament fabrication 3D printing machines, the feedstock material comes in the form of a filament wound onto a spool.
The 3D printer liquefier is the component predominantly used in this type of printing. Extruders for these printers have a cold end and a hot end. The cold end pulls material from the spool, using gear- or roller-based torque to the material and controlling the feed rate by means of a stepper motor. The cold end pushes feedstock into the hot end. The hot end consists of a heating chamber and a nozzle. The heating chamber hosts the liquefier, which melts the feedstock to transform it into a liquid. It allows the molten material to exit from the small nozzle to form a thin, tacky bead of plastic that will adhere to the material it is laid on. The nozzle will usually have a diameter of between 0.3 mm and 1.0 mm. Different types of nozzles and heating methods are used depending upon the material to be printed.
Different types of nozzles have different ways of replacing them. The most common used nozzles are the V6 nozzles made popular by E3D and MK8 nozzles. Changing the nozzle must be done while hot, to avoid plastic leaks.
Printing.
FFF begins with a software process which processes an STL file (Standard Triangle Language), orienting the model for the build process and mathematically slicing the model according to the processing parameters selected. If required, support structures may be generated.
The nozzle can be moved in both horizontal and vertical directions, and is mounted to a mechanical stage, which can be moved in the xy plane.
As the nozzle is moved over the table in a prescribed geometry, it deposits a thin bead of extruded plastic, called a ‘‘road’’ which solidifies quickly upon contact with the substrate and/or roads deposited earlier. Solid layers are generated by following a rasterizing motion where the roads are deposited side by side within an enveloping domain boundary.
Stepper motors or servo motors are typically employed to move the extrusion head. The mechanism used is often an X-Y-Z rectilinear design, although other mechanical designs such as deltabot have been employed.
Once a layer is completed, the platform is lowered in the z direction in order to start the next layer. This process continues until the fabrication of the object is completed.
For successful bonding of the roads in the process, thermal control of the deposited material is necessary. The system can be kept inside a chamber, maintained at a temperature below the melting point of the material being deposited.
Although as a printing technology FFF is very flexible, and it is capable of dealing with small overhangs by the support from lower layers, FFF generally has some restrictions on the slope of the overhang, and cannot produce unsupported stalactites.
Myriad materials are available, such as Acrylonitrile Butadiene Styrene (ABS), Polylactic acid (PLA), Polycarbonate (PC), Polyamide (PA), Polystyrene (PS), lignin, rubber, among many others, with different trade-offs between strength and temperature properties. In addition, even the color of a given thermoplastic material may affect the strength of the printed object. Recently a German company demonstrated for the first time the technical possibility of processing granular PEEK into filament form and 3D printing parts from the filament material using FFF technology.
During FFF, the hot molten polymer is exposed to air. Operating the FFF process within an inert gas atmosphere such as nitrogen or argon can significantly increase the layer adhesion and leads to improved mechanical properties of the 3D printed objects. An inert gas is routinely used to prevent oxidation during selective laser sintering.
Physics of the process.
During extrusion the thermoplastic filament is introduced by mechanical pressure from rollers, into the liquefier, where it melts and is then extruded. Flow geometry of the extruder, heating method and the melt flow behavior of a non-Newtonian fluid are of main consideration in the part. The rollers are the only drive mechanism in the material delivery system, therefore filament is under tensile stress upstream to the roller and under compression at the downstream side acting as a plunger. Therefore, compressive stress is the driving force behind the extrusion process.
The force required to extrude the melt must be sufficient to overcome the pressure drop across the system, which strictly depends on the viscous properties of the melted material and the flow geometry of the liquefier and nozzle. The melted material is subjected to shear deformation during the flow. Shear thinning behavior is observed in most of the materials used in this type of 3-D printing. This is modeled using power law for generalized Newtonian fluids.
The temperature is regulated by heat input from electrical coil heaters. The system continuously adjusts the power supplied to the coils according to the temperature difference between the desired value and the value detected by the thermocouple, forming a negative feedback loop. This is similar to ambient heating of a room.
Applications.
Commercial applications.
FFF and the other technologies of additive manufacturing by material extrusion (EAM) techniques are commonly used for prototyping and rapid manufacturing. Rapid prototyping facilitates iterative testing, and for very short runs, rapid manufacturing can be a relatively inexpensive alternative. EAM is also used in prototyping scaffolds for medical tissue engineering applications. Moreover, EAM with multi extrusion have become very popular to fabricate biomimetic composites. FFF is also applied in manufacturing within other sectors, including aerospace, automotive, construction, electronics, energy, pharmaceuticals, sports,
textiles, and toys.
Free applications.
There are multiple projects in the open-sourced community aimed at processing post-consumer plastic waste into filament. These involve machines used to shred and extrude the plastic material into filament such as recyclebots.
Several projects and companies are making efforts to develop affordable 3D printers for home desktop use. Much of this work has been driven by and targeted at DIY/enthusiast/early adopter communities, with additional ties to the academic and hacker communities.
RepRap is one of the longest running projects in the desktop category. The RepRap project aims to produce a free and open source hardware (FOSH) 3D printer, whose full specifications are released under the GNU General Public License, and which is capable of replicating itself by printing many of its own (plastic) parts to create more machines. RepRaps have already been shown to be able to print circuit boards and metal parts. Fab@Home is the other opensource hardware project for DIY 3D printers.
Because of the FOSH aims of RepRap, many related projects have used their design for inspiration, creating an ecosystem of related or derivative 3D printers, most of which are also open source designs. The availability of these open source designs means that variants of 3D printers are easy to invent. The quality and complexity of printer designs, however, as well as the quality of kit or finished products, varies greatly from project to project. This rapid development of open source 3D printers is gaining interest in many spheres as it enables hyper-customization and the use of public domain designs to fabricate open source appropriate technology. This technology can also assist initiatives in sustainable development since technologies are easily and economically made from resources available to local communities.
Development.
Customer-driven product customization and demand for cost and time savings have increased interest in agility of manufacturing process. This has led to improvements in rapid prototyping technologies. The development of extruders is going rapidly because of the open source 3-D printer movement caused by products like RepRap. E3D and BondTech are the most known extruder manufacturers currently on the market. Consistent improvements are seen in the form of increased heating temperature of liquefiers, better control and precision of prints, and improved support for a wide variety of materials. Besides the improved hardware, the ability to calibrate the extruder according to the hardware setup has come a long way.
Cost of 3D printer.
The cost of 3D printers has decreased dramatically since about 2010, with machines that used to cost now costing less than . For instance, as of 2017, several companies and individuals are selling parts to build various RepRap designs, with prices starting at about / .
The open source Fab@Home project has developed printers for general use with anything that can be extruded through a nozzle, from chocolate to silicone sealant and chemical reactants. Printers following the project's designs have been available from suppliers in kits or in pre-assembled form since 2012 at prices in the range.
The LulzBot 3D printers manufactured by Aleph Objects are another example of an open-source application of fused deposition modeling technology. The flagship model in the LulzBot line, the TAZ printer takes inspiration for its design from the RepRap Mendel90 and Prusa i3 models. The LulzBot 3D printer is currently the only printer on the market to have received the "Respects Your Freedom" certification from the Free Software Foundation.
As of September 2018 RepRap style printers are readily available in kit form through online retailers. These kits come complete with all parts needed to make a functioning printer, often including electronic files for test printing as well as a small quantity of PLA filament.
Filaments used for printing with FDM printers are also substantially more cost-effective than their SLA resin counterparts. If we use 3DBenchy as a benchmark for comparing both technologies, it would cost roughly $0.20 to print such a model with an FDM machine, whereas the same object would cost almost $1.00 if created with resin.
Materials.
Plastic is the most common material for 3d printing via FFF and other EAM variants. Various polymers may be used, including acrylonitrile butadiene styrene (ABS), polycarbonate (PC), polylactic acid (PLA), high-density polyethylene (HDPE), PC/ABS, polyethylene terephthalate (PETG), polyphenylsulfone (PPSU) and high impact polystyrene (HIPS). In general, the polymer is in the form of a filament fabricated from virgin resins. Additionally, fluoropolymers such as PTFE tubing are used in the process due to the material's ability to withstand high temperatures. This ability is especially useful in transferring filaments.
The many different variants of EAM, i.e. of material Extrusion based Additive Manufacturing allow dealing with many additional material types, summarised in the table below. Several material classes can be extruded and 3d printed:
Print head kinematics.
The majority of fused filament printers follow the same basic design. A flat bed is used as the starting point for the print workpiece. A gantry above this carries the moving print head. The gantry design is optimized for movement mostly in the horizontal X & Y directions, with a slow climb in the Z direction as the piece is printed. Stepper motors drive the movement through either leadscrews or toothed belt drives. It is common, owing to the differences in movement speed, to use toothed belts for the X,Y drives and a leadscrew for Z. Some machines also have X axis movement on the gantry, but move the bed (and print job) for Y. As, unlike laser cutters, head movement speeds are low, stepper motors are universally used and there is no need to use servomotors instead.
Many printers, originally those influenced by the RepRap project, make extensive use of 3D printed components in their own construction. These are typically printed connector blocks with a variety of angled holes, joined by cheap steel threaded rod. This makes a construction that is cheap and easy to assemble, easily allows non-perpendicular framing joints, but does require access to a 3D printer. The notion of 'bootstrapping' 3D printers like this has been something of a dogmatic theme within the RepRap designs. The lack of stiffness in the rod also requires either triangulation, or gives the risk of a gantry structure that flexes and vibrates in service, reducing print quality.
Many machines now use box-like semi-enclosed frames of either laser-cut plywood, plastic, pressed steel sheet and more recently aluminum extrusions. These are cheap, rigid and can also be used as the basis for an enclosed print volume, allowing temperature control within it to control warping of the print job.
A handful of machines use polar coordinates instead, usually machines optimized to print objects with circular symmetry. These have a radial gantry movement and a rotating bed. Although there are some potential mechanical advantages to this design for printing hollow cylinders, their different geometry and the resulting non-mainstream approach to print planning still keeps them from being popular as yet. Although it is an easy task for a robot's motion planning to convert from Cartesian to polar coordinates, gaining any advantage from this design also requires the print slicing algorithms to be aware of the rotational symmetry from the outset.
Extruder mount to rest of machine.
The ways extruders are mounted on the rest of the machine have evolved over time into informal mounting standards. Such factor standards allow new extruder designs to be tested on existing printer frames, and new printer frame designs to use existing extruders. These informal standards include:
Delta robot printers.
A different approach is taken with 'Rostock' or 'Kossel' pattern printers, based on a delta robot mechanism. These have a large open print volume with a three-armed delta robot mounted at the top. This design of robot is noted for its low inertia and ability for fast movement over a large volume. Stability and freedom from vibration when moving a heavy print head on the end of spindly arms is a technical challenge though. This design has mostly been favored as a means of gaining a large print volume without a large and heavy gantry.
As the print head moves the distance of its filament from storage coil to head also changes, the tension created on the filament is another technical challenge to overcome to avoid affecting the print quality.


Model-based enterprise

Model-based enterprise (MBE) is a term used in manufacturing, to describe a strategy where an annotated digital three-dimensional (3D) model of a product serves as the authoritative information source for all activities in that product's lifecycle.
A key advantage of MBE is that it replaces digital drawings. In MBE, a single 3D model contains all the information typically found on in an entire set of engineering drawings, including geometry, topology, dimensions, tolerances, materials, finishes, and weld call-outs.
MBE was originally championed by the aerospace and defense industries, with the automotive industry following. It has been adopted by many manufacturers around the world, in a wide range of industries. Significant benefits for manufacturers include reduced time to market and savings in production costs from improved tool design and fabrication, fewer overall assembly hours, less rework, streamlined development and better collaboration on engineering changes.
There are two prerequisites to implementing MBE: The first is the creation of annotated 3D models, known as a Model-based definitions (MBD). This requires the use of a CAD system capable of creating precise solid models, with product and manufacturing information (PMI), a form of 3D annotation which may include dimensions, GD&T, notes, surface finish, and material specifications. (The mechanical CAD systems used in aerospace, defense, and automotive industries generally have these capabilities.) The second prerequisite is transforming MBDs into a form where they can be used in downstream lifecycle activities. As a rule, CAD models are stored in proprietary data formats, so they must be translated to a suitable MBD-compatible standard format, such as 3D PDF, JT, STEP AP 242, or ANSI QIF
The core MBE tenet is that models are used to drive all aspects of the product lifecycle and that data is created once and reused by all downstream data consumers. Data reusability requires computer interpretability, where an MBD can be processed directly by downstream applications, and associativity of PMI to specific model features within the MBD.
History.
Historically, engineering and manufacturing activities have relied on hardcopy and/or digital documents (including 2D drawings) to convey engineering data and drive manufacturing processes. These documents required interpretation by skilled practitioners, often leading to ambiguities and errors.
In the 1980s, improvements in 3D solid modeling made it possible for CAD systems to precisely represent the shape of most manufactured goods—however, even enthusiastic adopters of solid modeling technology continued to rely upon 2D drawings (often CAD generated) as the authority (or master) product representation. 3D models, even if geometrically accurate, lacked a method to represent dimensions, tolerances, and other annotative information required to drive manufacturing processes.
In the early-to-middle 2000s, the ASME Y14.41-2003 Digital Product Data Definition Practices and ISO 16792:2006 Technical product documentation—Digital product definition data practices standards were released, providing support for PMI annotations in 3D CAD models, and introducing the concept of MBD (or, alternatively, digital product definition)
The model-based enterprise concept first appeared about 2005. Initially it was construed broadly, referring to the pervasive use of modeling and simulation technologies (of almost any type) throughout an enterprise. In the late 2000s, An active community advocating development of MBE grew, based on the collaborative efforts of the Office of the Secretary of Defense, Army Research Laboratory, Armament Research Development Engineering Center (ARDEC), Army ManTech, BAE Systems, NIST, and the NIST Manufacturing Extension Partnership (MEP). The "MBE Team" included industry participants such as General Dynamics, Pratt & Whitney Rocketdyne, Elysium, Adobe, EOS, ITI TranscenData, Vistagy, PTC, Dassault Systemes Delmia, Boeing, and BAE Systems.
Over time, based on community feedback, MBE became more narrowly construed, referring to the use of MBD data to drive product lifecycle activities. In 2011, the MBE Team published these definitions:
By 2015, with improvements to ASME Y14.41 and ISO 16792, and the development of open CAD data exchange standards capable of adequately representing PMI, MBE started to become more widely adopted by manufacturers.


Wiring pencil

A wiring pencil (often sold under the trade names of Roadrunner or Verowire) is a tool for making electrical connections.
A small reel of insulated copper wire is mounted at the top of the tool. The wire runs down the center of the wiring pencil and through a hardened tip, which is small enough to move between the pins of 0.1" pitch DIL chip allowing connections to be wrapped and the wire to be led across the circuit board to the next point it's needed.
The wire is coated with a polymer lacquer (commonly referred to as enamel, but not glass based). Once wrapped the connections are soldered, the heat of this burning the lacquer away and completing the joint. Insulated wire is normally 38 SWG (0.15mm), ground connections are sometimes made with uninsulated wire which is slightly heavier (33 SWG, 0.25mm).
A well ventilated area and/or fume extraction are very important when carrying out this process due to the toxic fumes. Sometimes, where there are many wires, plastic comb-like structures are used for wire management.


Sendzimir process

Sendzimir process (named after Tadeusz Sendzimir) is used to galvanize a steel strip by using a small amount of aluminum in the zinc bath and producing a coating with essentially no iron-zinc alloy. The process guarantees high resistance and durability characteristics. About 75% of hydrogen was needed in the original Sendzimir process but all the newer nonoxidizing methods of degreasing require only 7–15%.
The rolling of hot steel slabs using a Sendzimir mill requires a much smaller operational area than a continuous hot strip mill.
This milling process is not recommended for heavy duty running surfaces such as crane rail.


Seiko Instruments

 (SII) is a Japanese company, which develops and commercializes semiconductor, micromechatronics, and precision machining technologies. It is one of business units of Seiko Group Corporation (f/k/a Seiko Holdings).
Headquartered in the Makuhari business district, Mihama-ku, Chiba City, Chiba Prefecture, Japan, the company manufactures and sells electronic components (crystal oscillators, micromechatronics devices, piezo inkjet printheads, microbatteries, supercapacitors), precision parts, analysis and measurement instruments, machine tools, factory automation systems, printers, etc.
In 1937 , literally the second workshop for manufacturing Seiko timepieces, was established in Kamedo, Kōtō, Tokyo as a spin-off of the watch manufacturing division from , so had been making the Seiko watches until 2020. The company changed its name to Seiko Instruments & Electronics Ltd. in 1983 and to the current name in 1997. Its Suwa Plant in Suwa, Nagano Prefecture spun off as in 1959 is now known as .
On January 26, 2009, Seiko Instruments and Seiko Holdings announced that the two companies will be merged on October 1, 2009 through a share swap. Seiko Instruments became a wholly owned subsidiary of Seiko Holdings on the date that had been announced before.
Seiko had delegated a large portion of the manufacturing in its watch business to SII. Watches manufactured by SII were sold through the Seiko Watch Corporation, a subsidiary of Seiko Holdings Corporation. On April 1, 2020, the company transferred its watch business including its watch manufacturing subsidiaries Morioka Seiko Instruments, Ninohe Tokei Kogyo, Seiko Instruments Singapore, etc. to Seiko Watch.


Believe Pictures

Believe Pictures is a production company founded by partners Brian Bird, and Michael Landon, Jr. They have created (or co-created) major films such as "The Last Sin Eater", the "Love Comes Softly" film series and Saving Sarah Cain, which won a 2008 CAMIE Award.
Most of the releases went to Fox Faith for home video distribution.


Request for waiver

In a manufacturing environment, a request for waiver (RFW) is a request for authorization to accept an item which, during manufacture or after inspection, is found to depart from specified requirements, but nevertheless is considered suitable for use "as is" or after repair by an approved method.
In ECSS standard a RFW is defined as "unplanned  departure", as opposite to Request for Deviation (RFD) which is defined as "planned departure", being "departure" defined as the "inability of a product to  meet one of its functional performance or technical requirements". In both cases, no changes are applied to engineering documentation.
In accordance with MIL-HDBK-61A, the term "waiver" is no longer used, because the processing rules for a RFW are identical to those for a deviation, and the terms deviation and waiver were often confused.
A deviation from the contractual performance requirements or approved drawings should be submitted as a RFD. An RFD is a specific written authorization to depart from a particular requirement of an item's approved configuration documentation for a specific number of units or period of time. A deviation does not change configuration documentation.
Deviations are requested by contractors prior to manufacture, during manufacture, or after an item has been submitted for Customer inspection and acceptance. To be tendered for delivery or to be installed in an item to be tendered for delivery, deviant items must be suitable for use.


Servo Robot Group

SERVO-ROBOT Group is a company that develops and creates intelligent sensing and digital vision systems to simplify manufacturing process automation such as welding. Therefore, the main activity is to build intelligent sensing systems based on precision measurement with laser beams and other intelligent sensing devices applicable to various industries such as automotive, railroad, pipe and tube, aerospace, shipbuilding, fabricated structures, windmill towers manufacturing, etc.
Founded in 1983, SERVO-ROBOT has established its world headquarters, production plant and research and development center in the St-Bruno Industrial Park, south of Montreal, Quebec, Canada. More than 95% of SERVO-ROBOT's products are exported outside of Canada every year.
Applications.
Innovations developed in patents mentioned in the above section resulted in concrete solutions easily applicable to markets ranging from automotive to aerospace which has helped many companies and factories to become more productive and reach their Six Sigma constant improvements goals.
External links.
Robotic Industry Association
Manufacturing Talk


Energy Manufacturing Co. Inc

Energy Manufacturing Co., Inc. is an American manufacturing company based in Monticello, Iowa. Established in 1944, the company produces a variety of hydraulic cylinders, hydraulic pumps, valves, and power systems.
History.
In the early 1940s B.J. Pasker ran a blacksmith shop in New Vienna, Iowa. In this shop his son, Jerry, produced farm wagons made from discarded automobile spindles and rims. During this period, Pasker also developed a hydraulically powered front loader which mounted to farm tractors. In 1944 Jerry Pasker outgrew the blacksmith shop and sought a larger facility for his operations.
Energy in Monticello Iowa.
Jerry Pasker moved to South Cedar Street in Monticello, Iowa and was introduced to Harold Sovereign, who sold John Deere tractors and equipment. Pasker and Sovereign formed a partnership known as Industrious Farmer Equipment Company, and moved the business to the vacant second floor of Sovereign's dealership on South Cedar Street. In 1946 the business again outgrew its facility. To accommodate the expansion, Pasker purchased the property of an auto dealership on Main Street. During that time the company manufactured hydraulic components, wagon hoists, truck hoists, valves and hydraulic cylinders. In 1948 the company's name was changed to Energy Farm Equipment Company. In 1962 the business incorporated to become Energy Manufacturing Company, Inc., by which it is still known.
Jerry Pasker was killed in a 22 July 1964 airplane crash in Winnipeg, Manitoba, Canada; the company presidency then passed to LaVon Pasker.
Energy Manufacturing after Jerry Pasker.
In 1976 Energy completed construction of a new plant on in the Monticello Industrial park. In 1985 Energy Manufacturing Company was sold to CGF Industries of Topeka, Kansas. CGF also purchased an Omaha Nebraska company called "Williams Machine and Tool". In 1997 Energy was purchased by Lincolnshire Partners and in 1999 Energy was purchased by Textron, Inc. Textron ran the company for 5 years until Energy was acquired by an investment group. On November 15, 2005 Energy added to the facility office space for administrative and manufacturing support.
Energy 2005 - 2013.
Energy designs and manufactures custom welded hydraulic cylinders. It also designs and manufactures hydraulic valves, pumps, powerpacks and power systems. Energy's cylinders are used in construction, road machinery, forestry, man lift and hoist, industrial bailer, waste compacting, and agricultural industries. Energy manufactures a wide variety of hydraulic cylinders; welded, tie-rod, ram-type, rephasing, telescopic, and position-sensing. Energy has designed and manufactured hydraulic cylinders with bores from less than one inch (2.5 cm), up to 11 inches (28 cm). Cylinders have been manufactured with strokes up to 15 feet (4.5 cm). Energy has designed cylinders with working pressures as high as 10,000 psig (690 bar).
Energy Manufacturing sold.
On May 30, 2013 Ligon Industries LLC acquired Energy Manufacturing Co. Inc.. Ligon Industries, LLC was founded in 1999, and is located in Birmingham, Alabama. In addition to Energy Manufacturing, Ligon holds 13 other manufacturing companies, seven of which are in the fluid power industry. Ligon is the largest independent manufacturer of hydraulic cylinders in North America.