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Flip to reveal answersName four rules a moulded shape must obey.
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All 4 Flashcards — Design for process
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Question
Name four rules a moulded shape must obey.
Answer
Draft on every face so it releases, uniform wall thickness so it cools evenly, radii at internal corners, and no undercuts the tool cannot open past.
Question
Why does a thick section cause a sink mark?
Answer
It cools more slowly than the thin wall beside it and shrinks after the surface has set, pulling the skin in. The fix is a rib at the same wall thickness.
Question
What is an undercut and what does it cost?
Answer
A feature the tool cannot open past, such as a hook on an internal face. It needs a side-action or lifter, or a window in the wall beneath it.
Question
Why must the process be chosen before the detail design?
Answer
A part designed for machining is a different shape from the same part designed for moulding, so choosing afterwards means redrawing the product.
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Full study notes for Design for process
Topic 12.1 hub
Design for manufacture
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