Hello, using Rhino 5. I have a ring design with a spiral curve that has been piped. I need the pipe to intersect itself so there are no gaps between it’s sections. The problem is that when I try to cut out the inner part of the ring (the part that will touch the finger), to make it flat, I’m getting a boolean error because the pipe intersects itself. I’ve googled and searched these forums and the solutions say to build self-intersecting polysurfaces in multiple parts and then join them. The problem is that this piped spiral has 54 revolutions, and it tapers in thickness, so that would be very difficult. The polysurface is valid, but self-intersecting.
Is there a Rhino tool that I’m not aware of that will take a polysurface’s exterior shape and delete all interior geometry, thereby creating “3d printable” object that is solid on the inside?
In the 2nd picture attached, the orange cylinder is the cutter.
If there is no such tool or solution I was thinking of making the spiral have fewer revolutions, a small gap between the sections and then filling the space with a swept rail, but that’s not ideal for the design of the ring.
Since you don’t have Rhino8, ShrinkWrap will not be available to you.
You can try doing the boolean unions piece by piece. Each time, try it normally first, but if it fails, try moving the one of the two pieces by a very small amount (say, 0.002mm) in one direction (x, y, or z) and try again. If that fails, move the piece by the same amount in another direction (if you moved it in the x direction, do y this time). If you fail in all three directions, repeat process again and move the piece 0.002mm again in all three directions. Keep moving the piece until get a successful union. Then take that resulting piece and try to union another piece to it in the same manner, moving the new piece by small amounts in all the directions until you get a successful union. Keep doing that until you’ve unioned all the pieces and then you can cut out the center with the big cutter for the ring size.
Slicer software can usually handle overlapping geometry so you don’t necessarily need to provide a fused single object. I’ve had hundreds of SLS pieces printed with overlapping mesh geometry
If you have to have a closed solid, it is feasible to create something similar to your design that may well be close enough to what you need.
Create a spiral with half as many revolutions and pipe it. Copy the pipe and rotate it about the centre of the ring by half the angle occupied by one revolution of the spiral. Then boolean union the two pipes. Provided the two pipes overlap cleanly (in spite of the taper) you will create a solid which your central cylindrical cutter can boolean difference.
