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helical sweep
ChuckKey
Member Posts: 43 ✭✭✭
In public "Face Cam" , 2015-12-16, the cam face in question is made by a helical sweep of a rectangle lying in a radial plane. The bottom end of this face meets an arc produced by removing a radial extrusion. However much fiddling is done, the geometry prevents these two surfaces from blending as well as might be desired. Altering the sweep shape so that the generating edge is not normal to the axis might give some improvement, but would be a matter of trial and error. In the machine shop the cam face would be produced by a cylindrical milling cutter with its axis radial to the cam, moving in the helical path. This would blend properly, but I don't know how to get that effect in Onshape. Ideas?
The top end of the helical sweep meets a flat face normal to the axis. It does not seem to be possible to fillet these two surfaces.
The top end of the helical sweep meets a flat face normal to the axis. It does not seem to be possible to fillet these two surfaces.
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NeilCooke
Moderator, Onshape Employees Posts: 5,370 
I was intrigued so I had a go too. https://cad.onshape.com/documents/7a6281525b4b43a78e7af3c8/w/4880723f76814c84bce71034/e/3e0508b1ac7c4ab9badd1bf9
The issue here is that the contact between the helix and the milling cutter is not coincident with the part axis, but normal to the helix, so you can't simply sweep a horizontal line along the helix to get the shape. I had to measure the angle of the helix (sketch 5), find the tangency point using that angle (approximation), then simulate the contact between the cutter and the helix before sweeping that shape. The fillets are an approximation too, but the whole part is very close to what it would be in real life. See the comments in the doc.Senior Director, Technical Services, EMEAI5 -
OptionsChuckKey
Member Posts: 43 ✭✭✭
At first I thought the new 'wrap' function solved this issue. Having realised that thickness works radially on the target cylinder, I don't think it helps so much with my problem. Milling the cam profile with a radially presented milling cutter of non-zero diameter does not produce radial surfaces.
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https://cad.onshape.com/documents/a7f8fe0390d043ed9e37c751/w/30a323cd906f42e6917dae75/e/cd2dd3531ee94b08afa1bf05
Twitter: @onshapetricks & @babart1977
The issue here is that the contact between the helix and the milling cutter is not coincident with the part axis, but normal to the helix, so you can't simply sweep a horizontal line along the helix to get the shape. I had to measure the angle of the helix (sketch 5), find the tangency point using that angle (approximation), then simulate the contact between the cutter and the helix before sweeping that shape. The fillets are an approximation too, but the whole part is very close to what it would be in real life. See the comments in the doc.
Any ideas?