The Mk2 iron man arc reactors have 10 sections of plastic located in a ring around the outside of the arc. currently these were placed into the mold separately, but that was a bit of a faff. I figured they should each be on a sprue and connected to the centre of the arc. The whole item can be lifted out of the laser as one piece and placed into the mold, and I'll cut the sprues off afterwards. So I devised this test pattern to work out how big the sprues should be.
0.25mm sprue is completely gone, which ties in with my 0.2mm laser kerf.
0.50mm is just about thick enough
0.75mm works well on all the different materials and is still quite sturdy so I'll be using that size.