Cold press molding method

Figure 9. Cold press molding method [from Ref. 28],...

This process is an economical press molding method for manufacturing an intermediate number of parts, such as 200 to 2,000. It uses low-pressure, room-temperature curing resins, and inexpensive molds. Cold press is similar to compression molding except that the resin curing action occurs via its own exothermic heat of reaction (after resins are mixed with catalyst, etc.). Pressures are moderate, usually 20 to 50 psi. Thus molds can be made of relatively inexpensive metals, plaster, or reinforced plastics. The edges need not be trimmed. Ribs, bosses, and other fairly complex shapes are not easily produced. Two good mold surfaces are obtained. 

Several different processes can be used to produce a laminate. In what is called the hand application process, for example, glass-fiber mats are impregnated with unsaturated polyester resins. The impregnated mats are then removed from the mold by hand and pressed between rollers. The final molding is effected by cold pressing. The method is suitable for small numbers of objects with large surface areas (e.g., boat hulls). 

Thermoformed decorative inserts and labels have been molded into cold-press molded parts however, threaded metal inserts cannot be molded-in. Threaded inserts can be glued or tapped in place, but not into bosses, which are impractical. Molded-in holes, core pulls, slides, undercuts, and ribs are, likewise, imfeasible. Holes need to be drilled and their location can be held to 0.030 in. The same assembly methods used for parts made firom compression molding can be used for those made from this process. 

Cold Press Molding. This process is an economical method for manufacturing intermediate voliunes of products, using low pressure, room temperature cure and inexpensive molds (1). Glass-fiber preform or mat is placed between the matching molds, and liquid resin is added. Gel coats may be employed and woven roving may be added for strength. The mold is closed and the resin permeates the fabric and ciues, accelerated by its exothermic heat. Pressures are moderate... 

In cavity-compression molding the cold powder or mold material is placed under pressure in a heated mold. The process is also called hot pressing. Glass-fiber-reinforced, unsaturated polyester resins are processed by the heated-cavity-compression molding method. The vulcanization of rubber can also be carried out using this method. High-fidelity records are pressed out of the thermoplasts PVC or poly(ethylene-co-vinyl acetate), while cheaper records are injection molded. 

Colver (1918), 10, 319 442-483, 671 (Various methods of obtaining high d casts of HE are reviewed, eg, direct or press casting, chilled molds or shells, cold core expl, and centrifugation) h) Anon, ChemAge 1, 385—6 ... 

All shaping methods (also called molding ) mentioned are well-known in the ceramic industry [244, 247], Selection criteria depend on economical and technical requirements. Simple shaped parts mainly produced by uniaxial pressing, cold isostatic pressing, casting and especially injection moulding are favoured for components with complex geometry [263]. 

In compression molding, the mixture in the mortar is transferred to special pressing equipment, holding the proper compression mold (see Fig. 11.2). The method requires a replacement factor (see Sect. 11.5.1) specifically valid for this compression method. In both cold methods the quality of mixing active substance and grated base is very critical for sufficient content imiformity of the suppositories. Although no investigations are available, it is obvious that this process is most critical with low-dosed active substances and definitely has to be validated. 

This high-temperature-resistant polymer can be easily processed by conventional methods, including extrusion and injection molding. It can be joined by screw assemblies, snap-fit, press-fit, cold or hot heading, spin-welding, and heat-bonding. See Chapter 6 for more information about the adhesion treatment of ETFE. 

Wax has long been molded into cakes (8 to 12 lb) by means of a modified plate and frame press having plates through which cold water flows. This involves much manual labor, and accordingly continuous methods of molding are being developed. One method involves automati-... 

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