DIMENSIONAL CONTROL

Greater dimensional control and thinner tapes in multilayer ceramics are the driving forces for techniques to prepare finer particles. Metal organic decomposition and hydrothermal processing are two synthesis methods that have the potential to produce submicrometer powders having low levels of agglomeration to meet the demand for more precise tape fabrication. 

Interferometric systems, usually heflum-neon lasers, offer precise distance measurement over a scale of distances <100 m and in an indoor environment. Such devices are suitable for dimensional control of machine tools (see Machining MATERIALS, ELECTROCHEMICAL). 

Other Uses. The production of finished shapes from iron powder by compacting and sintering utilizes about 100,000 t of iron powder aimuaHy copper powder (2—10 wt %) is normally added as a sintering aid. Addition of 2% tin powder or equal amounts of tin and copper powder considerably lowers the sintering temperature and time of sintering at a cost saving. The tin addition also improves dimensional control. Iron powder plus 10 wt % powdered lead—tin metal is pressed and siatered to make pistons for use ia automotive hydrauHc brake cylinders. 

Leaney, P. G. 1996a Design for Dimensional Control. In Huang, G. Q. (ed.). Design for X -Concurrent Engineering Imperatives. London Chapman Hall. 

It appears that HIP was independently invented, also in 1955, at the Battelle Memorial Institute in Columbus, Ohio, under contract to the Atomic Energy Commission and with the immediate objective of bonding nucelar fuel elements with precise dimensional control. 

New machining techniques are constantly being introduced. Conventional workpiece materials have improved progressively through close control of manufacturer and heat treatment, and new materials have been fostered by the aeronautic and space industries. The results have been ever improving output, dimensional control and surface finish. The continuous development of cutting fluids has enabled these increasingly severe conditions to be accommodated. 

Not all product components are subjected to a load in fact most are not subjected to loads requiring an engineering analysis via engineering equations, etc. Experience in the material behavior on similar products and/or similar performance requirements are all that is needed. In these products designers become involved in their processing features that will prevent or reduce internal stresses, with elements that will lead to consistent and economical production, with appearance and dimensional control, etc. 

TS plastic products that are injection, transfer, or compression molded combine thick and thin sections relatively easily since the hardening process is a chemical reaction (Chapter 6). Annular shapes are best made by compression to gain best dimensional control and freedom from distortion. In the compression process, the molding compound is compressed and reduced to the plastic state in the mold. During this process, portions of the material may lie in hard forms in the mold while other portions are flowing rapidly with great force. 

The TPs change dimensions rapidly as they approach the cold flow point. Great care must be taken in the selection of critical dimensional control products for applications such as machines and instruments. Critical dimen-... 

The extrusion process has fewer process control problems with TPs than does injection molding but has greater problems in dimensional control and shape. During... 

Electrochemistry is the basis of many important and modem applications and scientific developments such as nanoscale machining (fabrication of miniature devices with three dimensional control in the nanometer scale), electrochemistry at the atomic scale, scanning tunneling microscopy, transformation of energy in biological cells, selective electrodes for the determination of ions, and new kinds of electrochemical cells, batteries and fuel cells. 

Common problems like insufficient filling-packing and poor dimensional control are often related to the gate size and design. Similarly, gate location is another important factor. They should be located in areas having heaviest cross-section of the part to assure fill-out and elimination of sink marks. Also their position should not facilitate the residual molded stress formation in the part, knit line formation. 

The mnning meter scale is the first control parameter for the dimensional control of the tire tread. The scale consists of evaluating electronics with a display screen. The scale is part of the quality control system and is integrated in the power line carrier (PLC) system. 

Chemical and electrochemical techniques have been applied for the dimensionally controlled fabrication of a wide variety of materials, such as metals, semiconductors, and conductive polymers, within glass, oxide, and polymer matrices (e.g., [135-137]). Topologically complex structures like zeolites have been used also as 3D matrices [138, 139]. Quantum dots/wires of metals and semiconductors can be grown electrochemically in matrices bound on an electrode surface or being modified electrodes themselves. In these processes, the chemical stability of the template in the working environment, its electronic properties, the uniformity and minimal diameter of the pores, and the pore density are critical factors. Typical templates used in electrochemical synthesis are as follows ... 

In the description of the product considerable attention should be paid to the container and valves and associated issues. Materials of construction, dimensional controls, container suppliers, valves and their suppliers, and the design limitations of the container should be discussed. 

The study of the basaltic dykes in evaporites demonstrates that dissolution and precipitation of phosphate minerals is a key process for the control of REE mobility and REE fractionation. In the present case, all REE found in secondary apatite in the basalt and in the salt are derived from the dissolution of primary magmatic apatite during basalt corrosion. This loss of REE from the basalt to the salt was not sufficient to lower significantly the REE concentrations of the basalt and it could only be detected by the analysis of the salt. The absolute quantity of REE transferred from the basalt into the salt, however, cannot be quantified because we have no three-dimensional control on the REE concentrations around the basalt apophy sis. 

The Rotosil process employed by Heraeus and Heraeus-Amersil is used for the production of tubular or cylindrical shapes. It permits greater uniformity and dimensional control than the previous process. The quartz is washed in hydrofluoric acid and distilled water to remove impurities which can promote crystallization during manufacture. The sand is then placed in a rotating horizontal steel tube where it is held at the circumference by centrifugal force. A carbon arc is passed slowly down the center of the drum to fuse the sand. A modification, using open rotating molds on a vertical axis, allows formation of cmcibles, beakers, and bowls. 

As illustrated in Figure 10.2, many composite applications utilize a caul plate or pressure intensifier. Caul plates result in a greatly improved part surface finish compared with a bag surface, improved dimensional control, and improved radius quality. Caul plates are also used to reduce ply movement during processing of honeycomb reinforced parts. Caul plates may be semi-rigid or rigid in nature. Semi-rigid caul plates, which are the most common type, are typically constructed of thin metal, composite, or rubber materials so they are flexible in... 

Rigid caul plates are typically constructed of thick metal or composite materials. Thick caul plates are used on very complex part applications or cocured parts where dimensional control is critical. Many rigid caul plates result in a matched die configuration similar to compression or resin transfer molding. Parts processed in this manner are extremely challenging because resin pressure is much more dependant on tool accuracy and the difference in thermal expansion between the tool and the part. Tool accuracy is critical to ensure no pinch points are encountered that would inhibit a tool from forming to the net shape of the part. 

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