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How to Extrude along a surface of cylinder while making a 90 degree twist
elias_uusitalo
Member Posts: 4 ✭
I would like create a a cut similiar to this.
Here is my progress so far but i have come to a impasse
The twist to be made is around 90degrees and the hole is around 8mm wide along the whole cut.
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Answers
A 1/4 spiral, a center line, a loft between these, a thicken of the lofted surface, rounds at the ends.
how do i make this spiral?
Here is one way to do it but there are other methods you could use
https://cad.onshape.com/documents/3174b1d03a5e77a98721a766/w/3453809b6684350966aee4e8/e/4d5b8ff0284c5986e964e48b
@GWS50 if you look at the geometry produced by the method you used it doesn't produce cylindrical faces at the ends of the thicken, or in the middle of the sweep which is what the cutter would do if this were a machined part, or would be required to match a cylindrical pin in an injection molded part. You need some kind of body sweep operation to handle this geometry.
See this other forum thread for details. I don't know if @Konstantin_Sh ever finished the body sweep tool from this discussion but it was being worked on at one point.
Is this what you're looking for? It's done with a wrap.
https://cad.onshape.com/documents/e1437c11e27dfdbe8eeef114/w/8e22d667f2ff4ead531b4c80/e/516fa85108e036da7adad29a
Wrap feature for sure
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Here is a version with 2 lofted surfaces….still not perfect as a cutter would make but better
https://cad.onshape.com/documents/3174b1d03a5e77a98721a766/w/3453809b6684350966aee4e8/e/4d5b8ff0284c5986e964e48bThis is one of those easy-to-machine but hard-to-model features that make machine shops roll their eyes at designers. The problem with the wrap feature is that it has a local context for tangency and normalcy but the 4 axis slotting operation that would be required for this part is rolling a 12mm cylinder through your part. The way to do this is to think purely in terms of the machining operation. First model the centerline of your cutting operation somehow, which wrap is useful for, but then doing a thicken operation that will match the cutter diameter, then adding in cylinder primitives at the end points of the toolpath.
Here's a photo of the interferences you'll encounter using wrap alone:
An example using some ruled surface operations and some solid primitives featurescripts courtesy of @EvanReese (though you could do this with sketch extrudes on mate connectors as well)
And a link to my doc to see how I did it.
https://cad.onshape.com/documents/82582ec2491e30f28cd4bacf/w/357f8fc6ebeac95345155eb7/e/6e6a3b0d521a696c46c1efb2
@Derek_Van_Allen_BD
Yes, as you say it's hard to get this stuff right in CAD. I've modeled cams in Solidworks, which has a native swept solid feature. However, the surfaces it created were atrocious. "Hand building" is probably a better solution, but it sure would be nice if there were better tools.
On a similar note I cringe to myself whenever I model a face chamfer as an edge break knowing that the machine shop I'm sending the part to has a 3 axis CNC and my 45° chamfers end up being some kind of random almost 45 angle because the chamfer tool doesn't snap to a floor plane. Maybe if I get more into the Onshape CAM studio and start having to deal with my own messes I'll write a machinable chamfer featurescript.
I made this video a long time ago, there may be improvements that make my method obsolete…
Out of curiosity I looked up how Solidworks does it these days and they specify the following constraints on their solid sweep operation:
Which if you ask me is such a cop-out. Where's my degree 5 spline surface support, dassault? The main thing I want to use this tool for is bottle feed screw augers that rotate the bottle as it translates on the assembly line. There's no challenge if I write a body sweep tool locked to rotationally symmetric analytical geometry. Then I really could just rely on surface sweeps and booleans on the ends.
@Derek_Van_Allen_BD Love that solution for a machinable version!
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www.theonsherpa.com
Here is something that Konstantin did many moons ago
https://cad.onshape.com/documents/39369c7fe89d343a835363dc/w/4c259cbc4e31028ea24d5754/e/b0228ac5cf7949b4a73c17a8