Injection Molded Plastic Part Design Guidelines
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Injection Molded Plastic Part Design Guidelines
For a new part design engineers to design a plastic part for a plastic injection molding, there can
be a knowledge gap in making sure the CAD model is properly designed for this manufacturing
process. There are certain, very specific design features that must be considered in the design
stage in order to avoid moldability issues that can produce undesirable results in the molded
parts. If they’re not considered from the beginning of the design process, and they’re not
discovered until the Design For Manufacturability (DFM) review, design changes can add time
and cost to an injection molding project.
Draft angle is one example. If a part does not have draft angle designed into it where needed, it
may not eject from the mold cleanly and smoothly, and the part will have to be redesigned with
proper draft angle.
To help avoid costly and time-consuming design mistakes, we created a plastic injection molding
design guide. It provides information on the most important design requirements so they can be
incorporated at the initial design stage. The sample tips below illustrate the type of information
provided in the complete guide. Download the complete design guide by filling out the form
below.
Bosses find use in many part designs as points for attachment and assembly. The most common
variety consists of cylindrical projections with holes designed to receive screws, threaded inserts,
or other types of fastening hardware. Generally, the outside diameter of bosses should remain
within 2.0 to 2.4 times the outside diameter of the screw or insert.
It is suggested avoiding bosses that merge into sidewalls because they can form thick sections
that lead to sink. Proper bosses should be positioned away from the sidewall, and if needed, use connecting ribs for support. Try using open boss designs for bosses near a standing wall.
