Just in time manufacture


By assuming such responsibilities, the control system greatly reduces the incidences where operator error results in off-specification batches. Such a reduc tion in error is essential to implement just-in-time production practices, where each batch of product is manufactured at the last possible moment. When a batch (or batches) are made todav for shipment by overnight truck, there is insufficient time for producing another batch to make up for an off-specification batch.  [c.753]

To minimize the cost of manufacture, one approach is to minimize the manufacturing throughput" time, sometimes called just in time or the Toyota lean manufacturing process.  [c.451]

Manufactured Components Varies Fast. The just in time requirements of manufactures demand quick dependable deliveries. Truck.  [c.511]

These ideas, interestingly described by Goldratt and Cox, provide flexible production and cater for customer requirements. They have become known as just in time (JIT) manufacture, but are often overlooked by many that think that investment in computer-controlled equipment is the only way to go. The concept, simplify before you automate, can provide significant improvements in production and can point the way to later advanced manufacturing where  [c.67]

The concentration of monomer within the coating decreases approximately exponentially with distance from the growth interface. With this decrease in monomer concentration, the rates of initiation and propagation reactions also decrease. Moving back into the polymer from the growth interface, through the reaction zone where polymer is being manufactured, a region in which the polymer formation is essentially complete is gradually entered. Because initiation is of higher order in monomer concentration, it tends to occur closer to the growth interface than does propagation. Under conditions prevailing during a typical deposition, the characteristic depth of the reaction zone is a few hundred nanometers, and the maximum concentration of monomer, ie, the concentration at the growth interface, is of the order of a few tenths percent by weight. Thus the parylene polymerization takes place just behind the growth interface in a medium that is best described as a slightly swollen, soHd polymer.  [c.433]

A typical formula for a proteia-based adhesive iacludes a aatural proteia that has beea solubilized by means of sodium hydroxide and then dispersed ia water. This ionized protein then is mixed with a defoamer, hydrated lime which acts as the cross-linking agent, sodium siUcate, various chemical denaturants, and biocides. These last materials are added because proteins are also nutrients for microbes. Fillers are also added in order to modify viscosity. Depending upon the formulation, the pot life of such an adhesive can be from several hours to several days. The adhesive is typically appHed by a roU coater and is normally heat cured in a press. The formula just described is typical of those used for the manufacture of plywood where the critical features include the moisture content of the wood, lack of foam in the coating, a material which is roU coatable, appropriate shelf life, and finally, resistance to moisture. The moisture content is critical to adhesive bond performance in that the physical properties of wood (qv) are substantially affected by the amount of water it contains. If plywood is made in such a fashion that the wood is either very dry or very wet during bonding, the plywood, when it changes moisture content during use, will change its size enough that it may delaminate. Protein-based adhesives are normally ranked by their resistance to moisture. Blood or blood—soybean-blend adhesives are considered to be the most water resistant, followed by casein or casein—soybean blends. The adhesive of least water resistance is based upon soybeans or animal hide glue.  [c.234]

Technology. The key piece of equipment in a hydrogen fluoride manufacturing plant is the reaction furnace. The reaction between calcium fluoride and sulfuric acid is endothermic (1400 kj /kg of HF) (334.6 kcal/kg), and for good yields, must be carried out at a temperature in the range of 200°C. Most industrial furnaces are horizontal rotating kilns, externally heated by, for example, circulating combustion gas in a jacket. Other heat sources are possible, eg, supplying the sulfuric acid value as SO and steam (qv), which then react and condense, forming sulfuric acid and releasing heat.  [c.196]

Manufacture. Phosphoms pentachloride is manufactured by either batch or continuous processing. In the former, the phosphoms trichloride usually dissolves in carbon tetrachloride before being treated with chlorine. A mixture of ca one part of phosphoms trichloride to one part of carbon tetrachloride is introduced to a water-jacketed vessel that contains an efficient stirrer and a tight cover with a redux condenser. The chlorine is passed into the vessel below the Hquid level, and crystals of phosphoms pentachloride form in the Hquid. When the reaction is completed, the suspension of crystals of phosphoms pentachloride in the carbon tetrachloride is drawn out of the vessel and the crystals are filtered and then dried by circulating hot water through the jacket of the filter. The clarified carbon tetrachloride is returned to the reaction vessel.  [c.371]

Cryogenic Gases. Some of the most sophisticated pipeline technology deals with the transport of Hquefied gases with very low boiling points, ie, cryogenic gases such as oxygen (—182.96 C), argon (—185.TC), nitrogen (—195.8 C), hydrogen (—252.8" C), and heHum (—268.9" C). These gases are Hquefied by modem cryogenic methods and shipped in cylinders or special storage vessels for bulk Hquid transport and storage (see Cryogenics). However, development of a system for piping them as Hquids has been brought about by the needs of the space program, superconducting magnets, and other high technology areas. The use of Hquid hydrogen as a rocket fuel and Hquid oxygen as the oxidant has resulted in piping these cryogenic materials to launching and test sites the use of Hquid helium to cool superconducting magnets led to the development of vacuum-jacketed, Hquid nitrogen-shielded piping systems (qv). Most of the lines have been relatively small-diameter systems however, similar but unshielded vacuum-jacketed lines up to 356-mm dia (19) and 8184 kPa (1200 psi), which would qualify as pipeline-sized piping, can be manufactured. CVI, Inc. (Columbus, Ohio) produces pipe for Hquid helium consisting of an inner line of stainless steel that is wrapped with aluminized Mylar and glass fiber paper and may be shielded by a patented aluminum extmsion cooled with Hquid nitrogen or cold helium gas the extmsion shield is also wrapped with superinsulating paper. This assembly is completely enclosed, tested, and factory sealed in a vacuum jacket with a stainless steel outer pipe, as shown in Eigure 1 (20). Piping systems based on similar technology are also designed for transfer of Hquid oxygen, Hquid nitrogen, and Hquid hydrogen Hquefied natural gas has also been transferred in vacuum-jacketed piping. Thus far, transfer lines are short by comparison with the longer-range pipelines for other appHcations, but many thousands of vacuum-jacketed piping installations in the 30—150-m range have been installed, with one system over 8 km in length.  [c.46]

Pump manufacturers pubflsh data indicating a minimum required net positive suction head (NPSHR) to ensure that suction pressure is adequate and that pumps do not cavitate. A user must therefore calculate the available net positive suction head (NPSHA) by going through the system losses analysis. The NPSHA should always be greater than the NPSHR plus a safety margin. A recommended margin added to NPSHA is 1.5 m (5 ft) or 35% over NPSHR, whichever is greater (53). There are several good reasons for this. The NPSHR pubflshed in manufacturers curves is based on pump tests. These tests, in accordance with HI Standards (9), defines NPSHR as equal to the value at which the pump actually loses 3% of its developed head. However, the incipient cavitation, ie, when first cavitation bubbles just begin to form, starts significantly before a 3% drop in head occurs. The value of the incipient NPSH is difficult to determine in commercial testing. Sophisticated research methods have been appHed (54), but despite extensive research there is no single accepted method to predict incipient cavitation for different pump types or different specific speeds. Figure 17 illustrates the phenomenon of incipient cavitation as it progresses toward fiiUy cavitating pump and eventual loss of performance at 3% head drop (55).  [c.301]

Greases are used as lubricants strictly because they are easily confined in a housing greases have no additional lubricating properties over the oils used to blend them. Good greases are blended with special additives (just as good oils are) that can enhance their wear protection and rust protection characteristics. Greases have a paste consistency and can be very soft or very hard. The National Lubricating Grease Institute (NLGI) has estabhshed a scale for the consistency of greases that ranges from 00 (the softest) to 6. Technically, the consistency of a grease is determined by measuring the penetration of a weighted cone into the surface of a grease a larger penetration indicates a softer grease. Unfortunately, the penetration value gives no indication about the lubricating properties of a grease two greases can have the same consistency, but one may be blended with a high-viscosity, highly refined oil and have only 6 percent thickener, while the other may be blended with a low-viscosity, low-quality oil but have as much as 20 percent thickeners. Manufacturers may only label a grease container as 2 lithium grease, which is not sufficient information. A complete specification sheet, however, is provided upon request. Larger manufacturers also publish a digest, in booklet form, that contains technical data on all their products.  [c.2539]

In a new compressor, the wires should not be used because the stress problems should be solved in a fundamental design manner without having to resort to fixes. When the manufacturer designs the blades, the vibrational characteristics for both rotor and stator blades should be established. The basic bending resonances and the higher orders to which the blades may be excited should be established. Care should be taken to avoid any direct excitation sources, such as splitter vane or stator and guide vane passing frequencies. If possible, any fundamental and lower order resonances should be at least three to four times higher than any of the running speed. The manufacturer should supply a Campbell diagram to demonstrate that the compressor is free of direct excitations. When resonances do exist in the operating range, the vendor should demonstrate his understanding of the stress level and provide some assurance to the user that the compressor will not have premature blade failures. One method to convey the information is with a Goodman diagram. Some users ask for Goodman diagrams for all stages, regardless of any resonant interferences, to demonstrate that a conservative design concept was used throughout the blading design. While stress levels in the rotor blading are by far the most severe, resonances can occur in the stator blades that have been known to fail when excited by one of the compressor s operating frequencies. This is a rare occurrence, but must still be considered. Most reported failures are caused by rubs or foreign object damage. Regardless of the cause, if a stator blade should break and drop into the gas path where it can be struck by the rotor blades, the wreck is just as traumatic as a direct rotor blade failure.  [c.251]

The effect of extrusion conditions on the impact strength of tubular film has also been studied and found to be related to molecular orientation. Polyethylene molecules in the melt have a very short relaxation time (a measure of the time taken for molecules to coil after release of an orienting stress). Thus in the tubular film process only molecules that have been oriented just before the melt freezes will remain in the oriented state. Because of this the order in which drawing down and transverse stretching of the film occur will affect the impact strength. These factors can be adjusted by varying freeze-line distance, blow ratio and output rate, the shape of the bubble giving a guide to the sequence of events. In recent years the technology of film manufacture has been extended by the appearance of ethylene-propylene rubber modified LDPE and also linear low-density polyethylene. Both materials can show high levels of toughness.  [c.236]

These values coupled with the flow rate and wet bulb temperature allow the selection of a cooling tower. Those new to cooling towers should make several selections at different wet bulb temperatures to test how wet bulb relates to cooling tower size. It becomes clear that the tower size increases as the wet bulb rises and that the size increase becomes dramatic as the approach is in the less than ten degrees area. This exercise demonstrates how to oversize a cooling tower... just use an inflated design wet bulb temperature. This is better than artificially inflating the flow rate and possibly over sizing the spray nozzles. Increasingly, manufacturers offer software to make selections easier.  [c.67]

Although there have been for many years a number of moulding methods (such as hand lay-up of glass fibres in polyester and compression moulding of thermosets or rubber) in which the plastic material is manufactured at the same time as it is being shaped into the final article, it is only recently that this concept has been applied in an injection moulding type process. In Reaction Injection Moulding (RIM), liquid reactants are brought together just prior to being injected into the mould. In-mould polymerisation then takes place which forms the plastic at the same time as the moulding is being produced. In some cases reinforcing fillers are incorporated in one of the reactants and this is referred to as Reinforced Reaction Injection Moulding (RRIM)  [c.302]

A similar procedure must be followed in industrial ventilation in the future. If the end user wants target class 1, the manufacturer must produce it. If the producer fails to deliver target class 1, the end user can ask the producer to make changes in the system such that the target can be achieved. In the worst case the producer will have to change the whole system. Specifying the different targets is just like selecting materials. The end user selects the lAQ, thermal conditions, energy efficiencies, and other efficiencies. Fulfilling all requirements in industrial ventilation is, of course, more difficult than in materials production, because industrial ventilation is affected by many different items that may be outside the hands of the contractor. In any case, all relevant items should be attached to the contract.  [c.358]

The review team should comprise, as appropriate, representatives of the purchasing, manufacturing, servicing, marketing, inspection, test, reliability, QA authorities, etc. as a means of gathering sufficient practical experience to provide advance warning of potential problems with implementing the design. The number of people attending the design review is unimportant and could be as few as the designer and his/her supervisor, provided that the supervisor is able to impart sufficient practical experience and there are no other personnel involved at that particular design stage. There is no advantage gained in staff attending design reviews who can add no value in terms of their relevant experience, regardless of what positions they hold in the company. The representation at each review stage may well be different - it may be just the designer and his/her supervisor at the conceptual review and representation from manufacturing, servicing, etc. at the final review.  [c.258]

Let s look at some of the cost drivers for a specific industry, namely the aerospace industry. First, let s lead up to that situation by looking at what happens with other industries. Generally, in any industry, we must consider the cost of energy, whatever material goes into the process we are dealing with, and the equipment necessary to process energy and material. Specifically, in the aerospace industry, metal-removal operations are strong cost drivers, and composite materials are just the opposite because with them there is virtually no such thing as material removal. High part count is also a big cost driver, and composite structures counter that problem by naturally and inexpensively combining segments of structures or structural elements. Fewer parts mean fewer fasteners, another very significant cost driver both in purchase price and installation cost (think of the cost of drilling thousands of carefully aligned holes in a structure ). Material utilization is another high cost driver, and composite materials are countering that in two different ways (1) in terms of the types of efficient manufacturing operations of composites buildup  [c.411]

Let s look at some of the cost drivers for a specific industry, namely the aerospace industry. First, let s lead up to that situation by looking at what happens with other industries. Generally, in any industry, we must consider the cost of energy, whatever material goes into the process we are dealing with, and the equipment necessary to process energy and material. Specifically, in the aerospace industry, metal-removal operations are strong cost drivers, and composite materials are just the opposite because with them there is virtually no such thing as material removal. High part count is also a big cost driver, and composite structures counter that problem by naturally and inexpensively combining segments of structures or structural elements. Fewer parts mean fewer fasteners, another very significant cost driver both in purchase price and installation cost (think of the cost of drilling thousands of carefully aligned holes in a structure ). Material utilization is another high cost driver, and composite materials are countering that in two different ways (1) in terms of the types of efficient manufacturing operations of composites buildup  [c.411]

The 29Q,0QQ-square-foot Miller SQA building was designed by William McDonough, FAIA to be a state-of-the art "green" building. Miller SQA, a wholly owned subsidiary of Herman Miller, Inc., is a remanufacturer, manufacturer, and vendor of office furniture that provides "just in time" furniture products for small businesses and nonprofit institutions. The building is a manufacturing plant, warehouse, and headquarters housing approximately 600 workers in a manufacturing plant and 100 workers in the office portion. The SQA building also has a lunchroom rest areas at each end of the manufacturing area and a fitness center, including a full-si e basketball court.  [c.198]

Zemplen helped his students in many ways. I remember an occasion in the difficult postwar period. The production of the famous Hungarian salami, interrupted by the war, was just in the process of being restarted for export. The manufacturer wanted a supportive analysis from the well-known professor. Zemplen asked for a suitable sample of some hundreds of kilograms, on which the whole institute lived for weeks. When it was gone he rightly could offer an opinion that the product was quite satisfactory. After the war, grain alcohol was for a long time the only available and widely used laboratory solvent, and, not unexpectedly, it also found other uses. Later, when it was denatured to prevent human consumption, we devised clever ways for its purification. The lab also manufactured saccharine, which was  [c.52]

Sensors based on microelectronics and photonics advances, along with gains in materials and interfacial science, are certain to provide higher performance sensor systems. The feasibiHty of much higher performance in terms of size, power consumption, and selectivity than that available as of the 1990s is demonstrated by biological sensors. The revolution in microelectronics manufacturing technologies nevertheless shows a growing trend toward diminutive cost as weU as size. In the particularly difficult case of chemical sensing, considerable development is expected to be necessary in order to match the sensing abiHties of an animal, such as a dog, to pick just one familiar example, but progress in that direction is expected.  [c.392]

Polymeric flocculants are high molecular weight organic chains with ionic or other functional groups incorporated at intervals along the chains. Because these compounds have characteristics of both polymers and electrolytes, they are frequently called poly electrolytes. They may be of natural or synthetic origin. All synthetic polyelectrolytes can be classified on the basis of the type of charge on the polymer chain. Thus, polymers possessing negative charges are called anionic while those carrying positive charges are cationic. Certain compounds carry no electrical charge and are called nonionic polyelectrolytes. Because of the great variety of monomers available as starting material and the additional variety that can be obtained by varying the molecular weight, charge density, and ionizable groups, it is not surprising that a great assortment of polyelectrolytes are available to the wastewater plant operator. Extensive use of any specific polymer as a flocculant is of necessity determined by the size, density, and ionic charge of the colloids to be coagulated. As other factors need to be considered (such as the coagulants used, pH of the system, techniques and equipment for dissolution of the poly electrolyte, and so on), it is mandatory that extensive jar testing be performed to determine the specific polymer that will perform its function most efficiently. These results should be verified by plant-scale testing. Types of polymers vary widely in characteristics. Manufacturers should be consulted for properties, availability, and cost of the polymer being considered. Dry polymer and water must be blended and mixed to obtain a recommended solution for efficient action. Solution concentrations vary from fractions of a percent up. Preparation of the stock solution involves wetting of the dry material and usually an aging period prior to application. Solutions can be very viscous, and close attention should be paid to piping size and length and pump selections. Metered solution is usually diluted just prior to injection to the process to obtain better dispersion at the point of application. Two types of systems are frequently combined to feed polymers. The solution preparation system includes a manual or automatic blending system with the polymer dispensed by hand or by a dry feeder to a wetting jet and then to a mixing-aging tank at a controlled ratio. The aged polymer is transported to a holding tank where metering pumps or rotodip feeders dispense the polymer to the process. It is generally advisable to keep the holding or storage time of polymer solutions to a minimum, one to three days or less, to prevent deterioration of the product. Selection must be made after determination of the polymer however, type 316 stainless steel or plastics are generally used. The solution preparation system may be an automatic batching system that fills the holding tank with aged polymer as required by level probes.  [c.116]

There is nothing more important and necessary in facing a dynamic new century than to be able to compete effectively in the arena of real life and to be able to offer the knowledge and skills demanded to succeed. We have undergone amazingly fast technological development in the relatively short period of two centuries since the industrial revolution. There is no single aspect of our life which has not been touched and fundamentally changed by it. Progress is not only continuing but is accelerating. Just recall some of what happened in our own 20th century the general use of electricity, dawn of the atomic age, fundamental changes in transportation (think about cars, planes, etc.) in communications (telephone, radio, television, satellite systems, FAX), the multitude of emerging new miracles of electronics, the enormous impact of the computer in all aspects of our life. We take all of them for granted as we near the end of the century. Whereas Science laid the foundations through developing fundamental knowledge, it was application by technology (engineering, manufacturing) which led to practical uses resulting in our highly technological oriented society. Of course, human knowledge and endeavor are broader in scope than just science or technology, and the arts and humanities much enrich our life. In life the most significant foundation for all of us is education and training which allow to be prepared for a productive and rewarding life. Nobody will be able to compete effectively at any level of the work force without the education and skills needed in the 21st century, which  [c.238]

Powder Glass-Ceramic Processing. The manufacture of glass-ceramics from powdered glass, using conventional ceramic processes such as spraying, sHp-casting, or extmsion, extends the range of possible glass-ceramic compositions by taking advantage of surface crystalliza tion In these materials, the reUct surfaces of the glass grains serve as the nucleating sites for the crystal phases. The glass composition and processing conditions are chosen such that the glass softens prior to crystallization and undergoes viscous sintering to full density just before the crystallization process is completed.  [c.319]

Monoca/cium Phosphates. Monocalcium phosphate (MCP) is generally made as a composition equivalent to the monohydrate, Ca(H2P0 2 20. The monohydrate is manufactured by several methods. Phosphoric acid and hydrated lime may be mixed in a pan or other heavy-duty mixer that allows the rapid escape of steam. The product is a paste that is dried and sized. The reaction may also be carried out in a more dilute system in conventional mixing equipment to produce a pumpable slurry that is then spray dried to give a lighter and more rapidly soluble product. Both methods, typically mnning at a CaO/P20 mole ratio just above 1.0, result in the presence of free acid and dicalcium phosphate as well as unreacted lime particles. Free acid causes caking and MCP is often aged or cured to allow for more complete reaction of the acid. Commercial MCP monohydrate usually contains several percent of dicalcium phosphate, which is acceptable in baking powder as an anticaking agent. MCP may also be manufactured by crystallization from solution. MCP made by this method may contain a small amount of free acid from entrained mother Hquor. Thorough washing of an MCP filter or centrifuge cake with water results in partial conversion to dicalcium phosphate.  [c.342]

At various stages during the post-development process, the coatings are rinsed. One of the most important reasons for rinsing is to reduce chemical carryover from one treatment bath to another, which increases solution lifetime. The most important washing occurs at the end of the processing, just before drying. The purpose of this washing is to eliminate all soluble compounds from the coated gelatin layers. Efficient removal of certain compounds is essential for good keeping properties and image permanence. Thiosulfate and argentothiosulfate complexes have particularly damaging effects on the keeping properties of the final print or film. Residual thiosulfate eventually reacts with the silver image in black-and-white products to produce silver sulfide and thereby confer a yellowish brown appearance or tone to the image. Inadequately removed silver thiosulfate complexes gradually decompose and are converted to silver sulfide with an accompanying yellow stain. For photographic materials coated on water-impermeable bases, such as glass plates and film, efficient washing can remove unwanted soluble residues almost completely. However, it is difficult to completely desorb and remove thiosulfate and argentothiosulfate complexes from the paper supports and baryta layers of reflection-print paper products. Resin-coated paper bases have made possible the manufacture of print materials having washing properties similar to those of films and plates.  [c.457]

Colorants can be introduced into the fiber by adding dyes and pigments in salt preparation, during polymerization, or into the molten polymer just before spinning (148) (see CoLORANTS FORPLASTics Dyes, application and evaluation). Pigmented fibers are referred to as mass-dyed, dope-dyed, solution-dyed, or producer-colored. Inorganic pigments are used more than the organics, especially where high color, light-, and crock fastness are required, such as in upholstery and carpet for automotive interiors. The organic pigments have higher chroma, but are not as colorfast to heat and light (see Pigments). Nylon-6 can accommodate more pigments than nylon-6,6 because of its lower melt processing temperatures. Like Ti02, the pigments must be dispersible and heat stable in polymer and fiber manufacturing (149). A common and efficient approach to adding pigment to the base polymer in spinning is first to disperse the pigment as a concentrate in a carrier polymer, usually a lower melting copolymer. The concentrates range from 25 to 50% pigment content and are offered as a single color or a compounded color blend in pellet or flake form. The flake can be blended with the base polymer flake at a specified loading and charged to the feed hopper of the spinning process or remelted in a vessel that allows it to be metered directly into the molten polymer prior to spinning. QuaUty pigmented fibers are spun with processes equipped with mixing screws and volumetric or gravimetric automatic feeders. Typical pigments for nylon are carbon black, red iron oxide, aluminum cobalt blue, and phthalocyanine blue and green. Carbon black enhances nylon s resistance to photodegradation. A number of light-stable pigments that are also environmentally friendly are available (150).  [c.257]

Carbon tetrachloride was one of the first organic chemicals produced on a large scale. In the 1890s, commercial manufacturing processes were being investigated by the United Alkali Co. in England. At the same time it was also produced in Germany, exported to the United States, and retailed as a spotting agent under the trade name Carbona. Large-scale production of carbon tetrachloride in the United States began about 1907. By 1914, aimual production fell just short of 4500 metric tons and was used primarily for dry cleaning and for charging fire extinguishers. During World War I, U.S. production of carbon tetrachloride expanded greatiy its use was extended to grain fumigation and the mbber industry. In 1934 it was supplanted as the predominant dry-cleaning agent in the United States by perchloroethylene, which is much less toxic and more stable. During the years immediately preceding World War II, trichloroethylene began to displace carbon tetrachloride from its then extensive market in the United States as a metal degreasing solvent. Carbon tetrachloride is more difficult to recover from degreasing operations, more readily hydrolyzed, and more toxic than trichloroethylene. The demands of World War II stimulated production and marked the beginning of its use as the starting material for chlorofluoromethanes, by far the most important appHcation for carbon tetrachloride.  [c.529]

In another approach, the out-of-dust time of enamels was reduced by using a polyfunctional isocyanate, such as isophorone diisocyanate trimer, as an additive to an alkyd enamel just before spraying. The isocyanates react with the hydroxyl groups of an alkyd and give faster drying. Two-package urethane coatings having hydroxy-functional acryHcs and polyisocyanates have been widely used. Many painters have decided that they do not want to use isocyanate systems because some have experienced respiration difficulties after spraying. AH manufacturers are therefore developing nonisocyanate cross-linking systems. Systems having toxic ha2ards as low as possible are the goal. Painters also need to be trained to handle them. The toxic ha2ard of  [c.358]

Filament Winding. Bodies of revolution such as cylinders and spherical sheHs can be manufactured economically by filament winding (24). Continuous fiber bundles or tows are wound onto a rotating mandrel. The fibers may be impregnated with resin (most frequently a thermoset) just before being wound onto the mandrel (wet winding) or may be preimpregnated with a partiaHy cured matrix (dry winding). The positioning of the fibers is achieved by a feeder arm located in front of the rotating mandrel. The wrap angle, that is the angle between the fiber and the axis of the mandrel, can usuaHy be varied between 0 and almost 90°, thereby enabling multidirectional components to be reali2ed relatively easHy. Once the winding process is finished the whole fixture is cured in an oven in order to yield the desired mechanical properties and stmctural integrity. The mandrel is then removed by dissolving (for salt- and sand-based mandrels), melting (for low melting point aHoys), or coHapsing and dismantling (for steel mandrels). Recently, attempts have been made to filament wind thermoplastic-based composites. The preimpregnated tow or roving is heated by a laser or a hot-air blower just before being wound onto the mandrel. Although this procedure is stiH in its infancy and more work is required in order to optimi2e the technique, it does offer great potential because the need for a subsequent curing process is removed. Filament winding requires a considerably greater financial investment than do conventional hand lay-up techniques. However, increased expense is in part offset by the greater reproducibHity of the resulting parts as weH as by the higher production rate.  [c.8]

Agglomeration Kinetics A change in particle size of a particulate material due to agglomeration is aldn to a change in chemical species, and so analogies exist between agglomeration and chemical Idnetics and the unit operations of size enlargement and chemical reaction. The performance of a granulator or compactor may be described by the extent of agglomeration of a species, typically represented by a loss in number of particles. Let (xi, Xo, , xj represent a hst of attributes such as average particle size, porosity, strengm, surface properties, and any generic quahty metric and associated variances. Alternatively, (xi, X9,. . . , xj might represent the concentrations or numbers of certain size or density classes, just as in the case of chemical reac tors. The proper design of a chemical reactor or an agglomcrator then rehes on understanding and controlhng the evolution (both time and spatial) of the feed vector X to the desired produc t vector Y. Inevitably, the reactor or granulator is contained within a larger plant-scale process chain, or manufacturing circuit, with overall plant performance being dictated by the interac tions between individual unit operations. For successfiil plant design and operation, there are four natural levels of scrutiny (Fig. 20-62). Conceptually, the design of chemical reactors and agglomeration processes differ in that the former deals with chemical transformations whereas the latter deals primarily with physical transformations with the mechanisms or rate processes of agglomeration controlled by a set of key physicochemical interactions.  [c.1875]

Probabilistic methods have gained increased interest in engineering as judged from the growing community of reliability engineers and from the increasing number of conferences on the subject (Ditlevsen, 1997). Some practitioners in the UK, however, either seem to lose confidence with statistical and probabilistic methods or are just not aware of them. At present, only larger companies seem to be aware of their importance (Howell, 1999). Some advocates of a statistical approach to engineering design even claim that this is why large chunks of manufacturing have moved to countries like Japan who embrace the use of such techniques. A comment in 1995 by Margetson gives an indication of the situation related to the UK  [c.33]

The General Electric Laboratory has a special place in the history of industrial research in America initially directed by the chemist Willis Whitney from 1900, it was the first American industrial laboratory to advance beyond the status of a troubleshooting addendum to a factory (Wise 1985). The renowned GE scientists, William Coolidge and Irving Langmuir (the latter a Nobel prizewinner for the work he did at GE) first made themselves indispensable by perfecting the techniques of manufacturing ductile tungsten for incandescent light bulbs, turning it into coiled filaments to reduce heat loss and using inert gases to inhibit blackening of the light bulb (Cox 1979). Langmuir s painstaking research on the interaction of gases and metal surfaces not only turned the incandescent light bulb into a practical reality but also provided a vital contribution to the understanding of heterogeneous catalysis (Gaines and Wise 1983). A steady stream of scientifically intriguing and commercially valuable discoveries and inventions continued to come from the Schenectady laboratory, many of them relating to materials as to the tungsten episode, a book published for Coolidge s 100th birthday and presenting the stages of the tungsten story in chronological detail (including a succession of happy accidents that were promptly exploited) claims that an investment of just 116,000 produced astronomical profits for GE (Liebhafsky 1974).  [c.8]

Chemical engineering, as a tentative discipline, began at about the same time as did physical chemistry, in the 1880s, but it took rather longer to become properly established. In fact, the earliest systematic attempt to develop a branch of engineering focused on the large-scale manufacture of industrial chemicals took place at Boston Tech, the precursor of the Massachusetts Institute of Technology, MIT. According to a recent account of the early history of chemical engineering (Cohen 1996), the earliest course in the United States to be given the title chemical engineering was organized and offered by Lewis Norton at Boston Tech in 1888. Norton, like so many other Americans, had taken a doctorate in chemistry in Germany. It is noteworthy that the first hints of the new discipline came in the form of a university teaching course and not, as with physical chemistry, in the form of a research programme. In that difference lay the source of an increasingly bitter quarrel between the chemical engineers and the physical chemists at Boston Tech, just about the time it became MIT.  [c.32]

Increasing environmental concerns in the I970 s brought an end to the use of chromates except for a few very large facilities where they were removed from the discharge water at site treatment facilities. Without chromates, the low pH water was very corrosive and many cooling towers and piping systems were ruined in short time. Substitutes have never lived up to chromates for effectiveness and cost. Wood towers didn t escape intense environmental scrutiny. The potential hazards of wood treatment chemicals became more apparent causing revised formulations and tighter controls both leading to increased costs. Asbestos also came into disfavor and was quickly phased out of cooling towers as the manufacturers became more aware of the potential health and financial liabilities. Type 304 stainless steel (SST) became more popular as the corrosion potential increased. Manufacturers simply substituted stainless steel for galvanized steel components. Due to cost constraints, just the cold water basin was typically upgraded to SST. There were some unfortunate occasions where galvanized and stainless steels were fastened together below the water line causing rapid deterioration of the galvanized steel at the joint from galvanic corrosion. Anyone considering mixing these materials must pay attention to the surrounding materials, particularly the fasteners. Such joints should never occur below the overflow level of the cooling tower.  [c.77]

We should spend just a few minutes talking about the Rotary Drum Precoat Filter. This machine is used to polish solutions having traces of contaminating insolubles, so it is not a dewatering machine per se, but its use is often integrated into the process. To polish the solution the drum deck is precoated with a medium of a known permeability and particle size that retains the fines and produces a clear filtrate. The following materials are used to form the precoat bed Diatomaceous Earth (or Diatomite) consisting of silicaceous skeletal remains of tiny aquatic unicellular plants Perlite consisting of glassy crushed and heat-expanded rock from volcanic origin Cellulose consisting of fibrous light weight and ash less paper like medium Special ground wood is becoming popular in recent years since it is combustible and reduces the high cost of disposal. There are nowadays manufacturers that grind, wash and classify special timber to permeabilities which can suit a wide range of applications. These materials when related to precoating are wrongly called filter-aids since they do not aid filtration but serve as a filter medium in an analogy to the filter cloth on a conventional drum filter. The Precoat Filter is similar in appearance to a conventional drum filter but its construction is very different. The scraper blade on conventional drum filters is stationary and serves mainly to deflect the cake while it is back-blown at the point of discharge. The scraper on a precoat filter, which is also called "Doctor Blade", moves slowly towards the drum and shaves-off the blinding layer of the contaminants together with a thin layer of the precoating material. This movement exposes continuously a fresh layer of the precoat surface so that when the drum submerges into the tank it is ready to polish the solution. The blade movement mechanism is equipped with a precision drive having an adjustable advance rate of 1 to 10 mm/hr. The selected rate is determined by the penetration of fines into the precoat bed which, in turn, depends on the permeability of the filter aid. Once the entire precoat is consumed the blade retracts at a fast rate so that the filter is ready for a new precoating cycle. The cake discharges on conventional drum filters by blow-back hence a section of the main valve s bridge setting is allocated for this purpose. On precoat filters the entire drum deck is subjected to vacuum therefore there are two design options  [c.522]

In some cases your choice may be limited to a single source since no other subcontractor may market what you need. On other occasions you may be spoilt for choice. With some proprietary products you are able to select particular options so as to tailor the product or service to your requirements. It remains a proprietary product, as the subcontractor has not changed anything just for you. The majority of products and services you will purchase from subcontractors, however, is likely to be from catalogs. The designer may have already selected the item and quoted the part number in the specification. Quite often you are buying from a distributor rather than the manufacturer and so need to ensure that both the manufacturer and the distributor will meet your requirements.  [c.320]

We just cannot expect situations like golf clubs and tennis rackets for all consumer products because all products do not have those same built-in characteristics of the competitive edge. When we consider a car, we must be realistic and acknowledge that the car must have a price low enough for people to afford. Think back to the days of Henry Ford he made a car that could be sold for about 250, so that everyone could afford to have one. This affordability was the real beauty of his mass-production techniques. Everyone could afford to have a car, and then almost everyone did have one. In contrast, before Henry Ford, only the rich could afford an automobile. As soon as we get to the trade-off where composite materials will effectively compete in the automotive market place, we will see tremendously broader applications, but there are problems along the way. The manufacturing cost must be improved in order for those applications to ever come about.  [c.465]

We just cannot expect situations like golf clubs and tennis rackets for all consumer products because all products do not have those same built-in characteristics of the competitive edge. When we consider a car, we must be realistic and acknowledge that the car must have a price low enough for people to afford. Think back to the days of Henry Ford he made a car that could be sold for about 250, so that everyone could afford to have one. This affordability was the real beauty of his mass-production techniques. Everyone could afford to have a car, and then almost everyone did have one. In contrast, before Henry Ford, only the rich could afford an automobile. As soon as we get to the trade-off where composite materials will effectively compete in the automotive market place, we will see tremendously broader applications, but there are problems along the way. The manufacturing cost must be improved in order for those applications to ever come about.  [c.465]


See pages that mention the term Just in time manufacture : [c.30]    [c.148]    [c.466]    [c.460]    [c.7]    [c.272]    [c.70]    [c.53]    [c.797]    [c.279]   
Plant Engineer's Handbook (2001) -- [ c.69 ]