Hi-Tech produces complex, tight tolerance components and assemblies that start off as a Near Net Shape and finish with a Conforming part.
Hi-Tech produces molded components in which the molded part is not the final geometry, referred to as Near Net Shape Molding. Certain geometry from the final part design is removed for a variety of reasons. After molding, the component is machine to generate the final part design.
Some of the reasons geometry is removed are:
1 – Elimination of knit lines.
2 – Addition of undercuts.
3 – Geometry and Tolerances
4 – Reduce tooling cost, low part volume
Molded knit lines in fiber filled materials are a source of significant reduction in mechanical properties (40-60% reduction in tensile properties). Mounting locations will often result in knit lines, if molded in. Machining holes for mounting locations will greatly reduce the potential for knit lines which may resulting in premature failure.
The example component has radial holes at an angle. To put this action into the Injection Mold Tooling would require several slide actions that represent significant tooling cost. The O-ring groove on the inside of the part would require an expensive collapsible core. The .080 of material opposite the mounting hole will be significantly weaker, if the mounting hole is molded in.
The Near Net Shape part design or “As Molded” design will require secondary machining operations, but will make the injection mold tooling significantly less expensive. The mounting hole locations will not have weak points.
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