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Old 4th January 2018, 06:24 PM   #1
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Junior member
Join Date: Jan 2018
Posts: 4
Default Subtraction problem; leftover triangles.

I'm trying to build some objects to 3D print. The shape I want is a hollow tube with a protruding lip, with longitudinal sections removed at 90 degree positions so that it has enough flex to clip into a hole.

So, I create either a rectangle or a polygon, offset it from the origin and revolve it through 360 degrees to make my hollow tube. I then create a primitive cuboid wider than the tube and position it such that it intersects with the tube on opposite sides. I then cut and paste this cuboid and rotate the copy though 90 degrees. I can then subtract the the cuboids from the tube to leave the shape I want.

It looks like it almost works but I get leftover triangles at odd positions on the surface of the removed volume. I've attached a screenshot.

Am I doing something wrong? I've made sure all my surfaces are single sided and that the normals are pointing the right way. I have a license for version 7 but I'm using a trial of version 8 at the moment.

Looking through the forums I see that there are quite a few similar issues with subtraction and the advice is generally to construct the object differently. I'm happy to do this but can't work out how to achieve the result I'm looking for by other means. Suggestions appreciated.


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