UV Photopolymer Resins

 It has been a moment since I last logged into this site...So welcome back to me....

I have been working with 3d printed resins now for a minute. Had a lot of mixed results and learned some tricks.

1st off, I have noticed that the "wax" resins don't reproduce fine detail and are generally better for heavy parts like thick shank men's rings. I have only cast a few rings from one companies "cast-able wax resin" I can say that I'm not impressed though it does work for some things. It is interesting that they are combining polyethylene and acrylate based materials. 

All of the resins seem to be very hygroscopic and or susceptible to the moisture or lack of it in the air. Like lets post cure the resin in glycerin to keep the air away.So environmental variables are a big factor in getting good prints. Going back to the hygroscopic issue... us casters want to take an object and put in a mixture of WATER and investment could be acid binding gypsum based or phosphate bond refractory stuff and then we are going to put it under a vacuum....

So as James Binnion states in his Santa Fe symposium papers “A New Method for Preparing 3D Acrylic Photo polymer Patterns for Investment Casting,”  if you have not read this paper take the time to read it! It appears that uncured material from the print is inside the layers of the print and the vacuum pulls it out and then it combines with the uncured investment. Then it degrades the investment surface and any sharp geometries will tend to get broken during the burnout process.... Go read James' Report there will be a test... its called life.....

Before I discovered this published work I was experimenting and thought after looking at printed models under a microscope, the surfaces appear to be open structures and I started experimenting with ways to seal the surface. I already had experience with issues related to RTV molding of printed parts and I started to use acrylic spray paint. It worked really well to keep the parts from having enough teeth to grab the surface of the part during the molding process so, I tried it on a couple of castings.

It worked really well for the most part. I found that the heavier I painted the parts the better it worked, my only guess at this point and after reading James paper is that I was sealing the model so that the vacuum could not pull the uncured material out.




It was working but still not perfect, here are some cast results as well...

This one had a lot of break down at the intersection of the bezels...

This one was better but still had some minor issues

and a little break down in the point.

Granted all of the parts were cast in gypsum investment that I added 20 grams of boric acid per liter of water and cast in a centrifugal caster. So.... too many variables to actually know for sure...

Who knows might be a Vacuum Kiln in my near future...