Mold unit

After mixing, doughs are immediately divided and rounded, rested briefly, then molded. Molded units are rapidly fro2en ia blast (or other) free2ers uatil reaching a core temperature of about —7 to —5°C. Units are boxed and stored at — 18°C, then shipped to end users. End users slowly thaw these products in 2°C retarders over 16—18 h, proof, and bake the products as needed (37—41). 

Engraved mold Unit cost low Labor cost low Investment moderate Limited Unrestricted Not critical Good durability No extra operations Best for simple lettering and texture. 

In addition to high-speed photography, which was used to obtain the results discussed above, other methods have been used to visualize flow, for example, the tracer method.279"281 A typical experimental device consists of a capillary viscometer connected to a mold, which is a simple model of plunger-type injection molding unit.279 A special device was used to introduce tracers of different colors in regular succession. After sample solidification, it is possible to examine the position of the various colors on the surface (Fig. 4.47 a) or through the volume by cutting sections (Fig. 4.47 b). It can be seen that the tracers are positioned symmetrically near the surfaces and that they have a V-type shape, with the tip oriented toward the stream. 

Disadvantages include higher initial mold cost, the need for both injection and blow molding units and lower volume production. 

Ram and piston injection molding units are used in the rubber iudustry [57]. The rubber stock is fed to a heated cyliuder, which is heated to the required temperature aud from there is forced by a hydraulic ram through a nozzle, mold runners, and... 

Injection equipment consists essentially of two parts the injection and clamping units. The injection unit melts the polymer and injects it in the mold. The vast majority of modern injection presses use a reciprocating screw. As in an extruder, the screw rotates, melts the polymer and pumps it. Furthermore, in most injection molding units, the whole screw can also axially move forward, acting like a plunger to inject the resin into the mold cavity through runners and gates. 

Two-shot molding Unit cost hig labor cost high investment moderate to high Limited Somewhat restricted Not critical Good durability Two molding operations Gocxl where maximum abrasion resistance necessary... 

Time a resin spends in a given processing machine (an extmder, injection molding unit, etc.) and is subjected to heat and stress. 

The extruder operates at melt temperatures of 360 to -100°F. The temperature is regulated by external cooling, RPM adjustment, or barrel tolerance. Higher melt plastics such as PET and PC, and contaminants such as aluminum and copper become a filler in the melted resins. The molding unit consists of linear molds mounted on a turret that rotate through a... 

This process can also be performed with a screw extruder. There are two ways of doing this. One, the screw-transfer method, uses a plasticating extruder, which not only replaces the preheat and preform portions of the cycle but also loads the pot. Another way of providing the material to be molded is to use a screw injection-molding unit. 

Times for each of the cycle portions in Fig. 9-9 are relative. Optimum drying cycle time for the injection cycle is about 1.5 s. This drying cycle time includes opening of the molds, movement of the mold unit, and close time. Basically, plasticated polymer (after an injection delay) is injected into the mold (injection), where it is brought to holding pressure and conditioned. After the injection... 

Rubber modified—moldings United States 2,275,957 1942 Rubber Production Assoc. 

Flame-retardant moldings United States 4,151,218 1979 Monsanto... 

Thermoplastic molding United States 4,243,766 1981 General Electric... 

Aminoplast binder and modifier for moldings United States 2,838,468 PAPER MODIFIER 1958 Monsanto... 

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