Key principles.
Generous
Internal corners minimum 0.5× wall thickness radius.
Smaller OK
External corners can be smaller (0.25× wall) but rounded.
Stress concentration
Sharp internal corners concentrate stress 3-5×.
Fillets help
Material flows better around radii. Sharp corners cause flow problems.
Sharp corners crack
Mold sharp corners crack and erode. Round corners last.
Same
No cost premium for rounded corners. Same machining or EDM time.
FAQ
Stress concentration, mold flow, tool life. No cost premium. Always round.
0.5× wall thickness ideal. 0.25× minimum acceptable.
Can be smaller. 0.25× wall thickness typical.
Rare — when assembly mating requires square corner. Use chamfer instead.
Note "all corners R0.5" or specific radii on drawing.
Add fillets in CAD model. Standard practice. Avoids manual fillet creation downstream.
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