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Spur gear and mirroring
marko_vukovic
Member Posts: 9 ✭
I wanted to create a quadruple helix gear by creating a double spur gear and then mirroring it. In addition, there is an axle going through the gear. The problem is that the mirroring fails sometimes. You can see it all here
https://cad.onshape.com/documents/e74757e357c7adabc40fca04/w/89877e5cbd9ca3395a87e2bc/e/927542888320be3287fa1d4a?renderMode=0&uiState=671fd9546497d73a0afdf23d
As is, the mirror operation fails. But if I do any of the following, the gear is mirrored correctly:
- change the pitch circle diameter to 20mm
- suppress the extrude operation to create the axle
- create straight instead of helix gear
Can anybody shed some light on this behaviour?
0
Answers
Move the Mirror feature before the extrude. Your extrude is splitting the body into 2 so the mirror does not know which one to use for the boolean operation.
OK, that does solve the problem. But I do not think the explanation stands. When I change the diameter or create a straight gear, I still have two bodies that mirror knows how to handle. And I have just noticed that mirroring against the top plane also also works, but not mirroring against the extruded face.
It is correct practice to do it that way whether the explanation stands or not 😊
I have simplified the test model further and I do not create the axle, I just bore through the gear. I know that it might still be "the best practice" to first mirror and then bore through, but it still looks to me like there is something wrong with the extruded gear face in this case since mirroring against the top plane works just fine. That "something" is apparently triggered by the gear parameters (tooth count, pitch circle diameter and helical gear) because it works just fine for some of them but not for the others.