Design Considerations for the Process

from Wikipedia

It is important when designing products for injection molding that you consider how they will be formed in the machine, how they will be taken out of the machine, and the structure of the final product. Some important guidelines are:

• Use approximately uniform wall thicknesses throughout your designs.
• Keep walls thin - typically between 1/32" and 1/10". This allows for proper cooling and reduces cost by minimizing use of material. Thin walls also reduce problems with material shrinkage. Although some unevenness will occur due to shrinkage, walls as thick as 1/5" can be used. Keep wall thickness at least wall length / 50. Keep 90 deg walls under 0.25" high.
• Keep thickness of ejection pin surface wall at least .07".
• To strengthen parts, instead of using thicker walls, use additional structures such as ribs. Use fillets at the base of ribs.
• When using a rib make it about half the main wall thickness.
• Round corners and edges wherever possible.
• For easy release of the part from the mold, add a slight taper to the sides (typically ~ 2 deg) - especially for textured walls and walls higher than 0.25".
• Avoid undercuts that are impossible to remove from the mold.
• Lighter colors hide flow patterns better than dark colors.
• Where walls meet at a 90 angle, round inside and outside to at least .05" radius - sharper outside corners can create molding problems and sharper inside corners will increase tooling cost.
• Keep holes at least .015" from edges.

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