Processing mold design

Mold temperatures range from 155 to 170°C both for polyester and epoxide resin compounds, with molding pressures ranging from 5 to 100 MPa depending on the type of compound to be processed, mold design and temperature. Cure time in the mold (excluding pre-heat time) is usually of the order of 10-30 s per millimetre of wall thickness for both types of compound. 

Injection Molding Guide for Thermoplastic Rubber—Processing, Mold Design, Equipment, Advanced Elastomer Systems LP, Akron, Ohio, 1997. 

Developments. A variety of process modifications aimed at improving surface finish or weld line integrity have been described. They include gas assisted, co-injection, fusible core, multiple Hve feed, and push—pull injection mol ding (46,47). An important development includes computer-aided design (CAD) methods, wherein a proposed mold design is simulated by a computer and the melt flow through it is analy2ed (48). 

MOLDEST Provides product design, mold design, and injection molding process control by Fujitsu Ltd., Tokyo, Japan. 

In addition to the process parameters, there are large numbers of factors that decide the success of an injection molding operation. Mold design, product design, position, and size of gates, type and positioning of runners, etc., are extremely important factors to be taken care of. A detail consideration regarding these factors has been discussed below [213]. 

To meet the products functional needs the wall thickness of the part can be varied. However, to obtain optimum processing cycles and reduce the chance of sink- and flow-mark formation, wall thickness should be kept as uniform as possible. Where variation in wall thickness is unavoidable, gradual transitions in the wall thickness should be provided to ease the polymer melt flow transitions. Part design, mold design, and gate location should work together to allow the material from heavier section into thinner walls for best appearance and process latitude. 

Beall, G. L. Rotational Molding Design, Materials, Tooling and Processing. (1998) Hanser Gardner Publications, Cincinnati. 

Fig. 1.9 Conceptual breakdown of polymer compounding, blending, and reactive polymer processing (27). Designer pellets are processed in extruders or injection molding machines to form products, with the possibility of further structuring or destructuring .

Because mold filling is a complex process, flow visualization studies have been useful and necessary, both for the actual mold design and for the mathematical simulation of the process. The first important experimental contributions were made by Gilmore and Spencer (8,9) whose work forms the basis of a review chapter by Beyer and Spencer (10). Ballman et al. (11-13) conducted mold filling experiments in the early 1960s. A decade later, a time that marks the beginning of serious efforts to solve... 

The largest volume of fluoroelastomers (about 60% of total) is processed by compression molding. A blank (preform) is placed into a preheated mold, compressed, and cured at the appropriate temperature (see above) for a time established empirically. A good estimate for the curing time in the mold is the value of Co from the measurements by oscillating disk rheometer. In the mold design, it is necessary... 

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