Design for RRIM

Disadvantages of direct fill are the possibility of causing blemishes opposite the entry point, because the material makes a 90° turn over a sharp edge (which can cause bubbles or scarring). The mixture will be free of bubbles only if the wall thickness at the entry point is less than one-eighth of the diameter of the entry area. If the mixing head cannot be flush-mounted, the sprue should be as short as possible, to allow mold release to be sprayed into the sprue cavity. 

Short fiber-reinforced systems are particularly vulnerable to formation of weld lines because the fibers tend to align with the direction of the flow. When flow fi-onts join, there is no fiber crossover or homogeneity, and the problem is intensified with faster reaction and gelling times. To minimize this, consider locating the gate closest to the largest obstruction to the flow. Computerized moldflow analysis can help predict where problems may occur. 

In structural molding, the glass mat should fill the entire mold cavity leaving no empty areas between mat and mold wall. The mat therefore 

Different methods are used for assembling, joining, or finishing RP to RP products as well as RP to other materials. It is important to both 

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