Plastic Injection Molding Design Considerations
Plastic Injection Molding Design Guidelines
- Use an approximately uniform wall thickness throughout your design.
- 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
shapes that are impossible to remove from the mold. Lighter colors
hide flow patterns better than dark colors. Choose the right material
from the table. Drawing dimensions should be of the final
part - material shrinkage will automatically be considered in the
design of the mold. Use raised text instead of recessed text when
possible. 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. It should not be possible to fully
hide a 0.3" diameter ball anywhere inside the material.
