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Help with patterning extrude cut along helix?

Eleanor_CoffinEleanor_Coffin Member Posts: 43 ✭✭
edited August 2021 in Using Onshape
Hi all, I'm looking for some help with patterning a cut along a helix path. Screenshot below to show what I'm working with. The preview it shows is the result that I want, but it's erroring out and won't complete the pattern.

Some extra info: My sketch plane is 1mm offset from the surface. My original extrude is thru all, both sides. I'm patterning along a helix that is tangent to the sketch plane (at the 1mm offset).

I know I can pattern the sketch and extrude each cut individually, but I feel like there has to be a better approach. Any advice? Thanks!


Best Answer

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    bradley_saulnbradley_sauln Moderator, Onshape Employees, Developers Posts: 373
    Answer ✓
    If @John_P_Desilets suggestion doesn't work you can always create a part to be a cutting tool and perform a part pattern with the remove option.
    Engineer | Adventurer | Tinkerer
    Twitter: @bradleysauln


Answers

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    John_P_DesiletsJohn_P_Desilets Onshape Employees, csevp Posts: 241
    @Eleanor_Coffin Have you tried checking apply per instance? 
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    bradley_saulnbradley_sauln Moderator, Onshape Employees, Developers Posts: 373
    Answer ✓
    If @John_P_Desilets suggestion doesn't work you can always create a part to be a cutting tool and perform a part pattern with the remove option.
    Engineer | Adventurer | Tinkerer
    Twitter: @bradleysauln


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    kevin_o_toole_1kevin_o_toole_1 Onshape Employees, Developers, HDM Posts: 565
    Seems likely this issue is not with the pattern, but the boolean. Subtracting a box which is exactly tangent to a cylindrical face is not valid geometry in Onshape (there's a non-manifold edge created at the contact point), and I imagine it's not the result you want – you to subtract material all the way through that inside face.

    If this is the issue, you can fix it by adding a second direction to the extrude, extending out a bit in the other direction, so the boolean will drill through the rest of the material in that curved face.
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    Eleanor_CoffinEleanor_Coffin Member Posts: 43 ✭✭
    @bradley_sauln This worked perfectly, thank you!

    As an academic exercise, answers to the other two suggestions:

    @John_P_Desilets Yes, I did try that. The pattern preview disappears when I check Apply per instance.

    @kevin_o_toole_1 I considered that too. That's why I offset the sketches 1mm from the helix's surface. My extrude settings were set to Remove, Through all, Symmetric as well, in an effort to avoid that issue.

    Thanks all for your advice!
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