Precision Parts

As already outlined, the low shrinkage of ARBOFORM on demoulding enables high-precision fittings to be manufactured. This cannot be achieved by normal synthetic plastics. 

---

Ethylene oxide (qv) was once produced by the chlorohydrin process, but this process was slowly abandoned starting in 1937 when Union Carbide Corp. developed and commercialized the silver-catalyzed air oxidation of ethylene process patented in 1931 (67). Union Carbide Corp. is stiU. the world s largest ethylene oxide producer, but most other manufacturers Hcense either the Shell or Scientific Design process. Shell has the dominant patent position in ethylene oxide catalysts, which is the result of the development of highly effective methods of silver deposition on alumina (29), and the discovery of the importance of estabUshing precise parts per million levels of the higher alkaU metal elements on the catalyst surface (68). The most recent patents describe the addition of trace amounts of rhenium and various Group (VI) elements (69). 

PBT has tended to replace polyamides in a number of precision parts due to its better dimensional stability. 

Dial indicators Figure 54.15 shows a common dial indicator, which is also called a mnout gage. A dial indicator is an instmment with either jeweled or plain bearings, precisely finished gears, pinions, and other precision parts designed to produce accurate measurements. It is possible to take measurements ranging from one-thousandth (0.001 inch or one mil) to 50 millionths of an inch. 

Heat-resistant parts, precision parts, miniature connectors... 

Chartered Metal Industries Toolroom in Singapore produces a wide range of standard and customized products to support manufacturers in the metal industries. Their production includes high-volume, batch-run precision parts, prototype components, subassemblies, tooling, fixtures, and gauges. 

Coils, rewind rollers for radio and videocassettes, stereo cassette parts, tape decks... Precision parts for measurement and control technology. .. 

After the (im)precision part of the uncertainty we now want to estimate the trueness (bias) part. For that we... 

Precision parts, electric connectors Vectra Zylon Twaron Liquid crystalline polymers DuPont, USA Toyobo, Japan Akzo, Netherlands... 

Experimental data show that, at temperatures from about 100 to about 200 °C, co 1 at wavelengths from 2500 to 3200 A50,51. The value cannot be exactly unity toward the long wave end of this region because there is a small fluorescence of acetone even at these temperatures52. The exact point at which fluorescence ceases to be excited is indeterminate and should be slightly temperature dependent. There is no fluorescence at 2537 A. The quantum yield of fluorescence seems never to have been determined with high precision, partly because it is low and the intensity very weak. The value is certainly less than 0.01 under the experimental conditions cited. Hence within the experimental error one may state... 

Finishing by cutting, grinding, lapping, polishing, drilling for precision parts with optimised surfaces. 

Applications Wear parts, precision parts Cutting tools, wear parts, ball bearings, seals, engine parts (valves, turbo charger rotors) Mainly used for evaluation of materials, prototypes with simple geometries, cutting tools... 

Ball bearings, wear parts, precision parts Materials with no or very low additive content Refractories Same as SSN/GPSN... 

To mold micron-scale precision parts with shot weights of only 0.0022 g, electrical operating IMMs are being used. Those who desire precise shot size (dosing) can buy electric injection machines with servomotors capable of very accurate screw positioning. With hydraulic IMMs, molders can install a valve gate that shuts when the correct amount of plastic has been injected into the mold. 

A direct mechanical connection with the spindle drive is required to provide the proper relationship for feeding or threading operations. The lead screw is a precision part and is usually only used for threading operations to avoid unnecessary wear. 

One practical consequence of these data is that particular care must be paid to the precise part of the plant being used. In samphng a kilo, for example, you may get a very incorrect impression if you happen to taste some bottom leaves or, conversely, some flowering tips. Another consequence is that the more potent the plant, the more striking the difference between the flowering tops and the leaves. 

It is sometimes convenient when describing very dilute solutions to employ the designation ppm (sometimes spelled p.p.m.). This is an abbreviation for parts per million, or more precisely, parts of solute per million parts of solution, a weight/volume designation. Let us examine the case in which we have prepared a 0.0001% w/v solution of some salt. This concentration may be written as 0.0001 g salt/100 mL. Let us convert this ratio to one of whole numbers ... 

Bar- and rod-shaped parts with straight or shouldered outer and inner contours, different profiles Precision parts ready to be installed as a result of cold forming... 

Coining This injection-compression process produces high pressure, stress-free precision parts... 

---