Casting Glass from 3D Printed Molds • Hacker News Board

Re: Casting Glass from 3D Printed Molds

#21

Post by b_tterc_p » Tue, Aug 06, 2019, 2:30 PM UTC

bariumbitmap wrote: post #20

> Once you have a model, the problem you need to solve is how to make a model with no undercuts. Undercuts will make it impossible to remove the 3D printed positive Is there a mathematical term for solids with this property? It reminds me of the vertical line test, but in 3D. https://en.wikipedia.org/wiki/Vertical_line_test

Convex perhaps?

Re: Casting Glass from 3D Printed Molds

#22

Post by dezork » Tue, Aug 06, 2019, 2:40 PM UTC

bariumbitmap wrote: post #20

> Once you have a model, the problem you need to solve is how to make a model with no undercuts. Undercuts will make it impossible to remove the 3D printed positive Is there a mathematical term for solids with this property? It reminds me of the vertical line test, but in 3D. https://en.wikipedia.org/wiki/Vertical_line_test

I would call it self-occluding.

Re: Casting Glass from 3D Printed Molds

#23

Post by FreeFull » Tue, Aug 06, 2019, 2:51 PM UTC

b_tterc_p wrote: post #21

bariumbitmap wrote: post #20

> Once you have a model, the problem you need to solve is how to make a model with no undercuts. Undercuts will make it impossible to remove the 3D printed positive Is there a mathematical term for solids with this property? It reminds me of the vertical line test, but in 3D. https://en.wikipedia.org/wiki/Vertical_line_test

Convex perhaps?

There are non-convex shapes that don't have undercuts. I think convexity implies that you don't have undercuts, though.

Re: Casting Glass from 3D Printed Molds

#24

Post by alittletoolate » Tue, Aug 06, 2019, 3:04 PM UTC

Here is another artist who uses the technique.

https://mtyka.github.io/art/2016/12/11/lostpla-casting-glass...

Re: Casting Glass from 3D Printed Molds

#25

Post by wgj » Tue, Aug 06, 2019, 4:34 PM UTC

bariumbitmap wrote: post #20

> Once you have a model, the problem you need to solve is how to make a model with no undercuts. Undercuts will make it impossible to remove the 3D printed positive Is there a mathematical term for solids with this property? It reminds me of the vertical line test, but in 3D. https://en.wikipedia.org/wiki/Vertical_line_test

In die casting, you have to do a little better than the vertical line test and stay within the specified draft angle. A vertical wall would be a 0 degree draft angle, and not suitable for casting most materials.

Re: Casting Glass from 3D Printed Molds

#26

Post by dreamcompiler » Tue, Aug 06, 2019, 7:43 PM UTC

bariumbitmap wrote: post #20

> Once you have a model, the problem you need to solve is how to make a model with no undercuts. Undercuts will make it impossible to remove the 3D printed positive Is there a mathematical term for solids with this property? It reminds me of the vertical line test, but in 3D. https://en.wikipedia.org/wiki/Vertical_line_test

I'd call it "monotonically expanding" along some particular direction vector.