Two steps forward, 1.9 steps back

26 OCT 2

I've spent the last three months developing a new process using an engineering resin that has less shrinkage than the ABS-like resin I was using before. Here's what they look like:

But I don't think these will ever ship. :( One, the fancy resin isn't helping with the alignment problems like I initially thought and is super fussy, doesn't like to stick to the build plate. Two, I think I have a different solution for the shrinkage: It looks like if I wait a couple of days after printing and washing before I cure them, the type balls don't shrink nearly as much.

This shows shrinkage (in mm/100) on the Y axis, # of days on the X. I printed six balls and cured them immediately, the next day printed the same six and waited 5 days to cure them, then I occasionally measured them all over the last few months. The left plot is average shrinkage of the inner diameter of the center hole (what's been causing so much trouble), right is the inner diameter of the shell. Blue is the cured-immediately group, green is the delayed cure. I'm not sure what's going on exactly; I'd assumed there would be the same amount of shrinkage either way and the early curing was dragging that out, that delaying the curing let us get the shrink over with faster, but that doesn't seem to be the case. It looks like the resin prefers to have some time to settle down after printing, finish its cross-linking presumably, and then it's more stable.

This will take more testing and calibration before I can open the store back up but it's looking promising. It will also slow down production, and I'm okay with that--I've spent a lot of time this summer printing and rinsing and curing and testing and now most of that is sitting in the trash can.