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Design Recommendations
It is recommended that
the designer always keeps in mind the inherent nature of thermoformed
components: they are nearly uniform in wall thickness and exhibit
few undercuts or reentrant shapes. In keeping with these basic limitations,
the following are specific design recommendations:
- Observe the depth-of-draw
limitations of the thermoforming process to be used. In general,
shallow drafts are more easily produced than deep ones and result
in more uniform wall thickness of the finished component.
- Avoid undercuts
because they complicate tooling. They require movable or collapsible
tool members.
- Never specify sharp
corners. They hamper the flow of material into the mold, result
in excessive thining of materials, and cause concentration of
stress.
- Sidewalls should
have some draft to facilitate easy removal of the workpiece
from the mold.
- Metal inserts are
not feasible becuase the thin walls of thermoformed parts are
not sufficiently strong to hold an insert.
- Thermoformed parts
may lack rigidity. Corrugations, prefeably in two directions,
or an embossed pattern can add remarkably to their rigidity.
Source: Bralla,
Design for Manufacturability Handbook.
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