Obtaining very transparent parts by replacing PDMS with glass


#1

So I was reading this paper: http://pubs.rsc.org/en/content/articlelanding/2016/lc/c6lc00153j#!divAbstract

One aspect they comment on is the role of surface roughness of the window in transparency of 3D printed parts. I’ve noticed that my parts are never that transparent (see Fig 2A (left) in the article). This lab, however, was able to obtain remarkably transparent parts by replacing the build plate with polished silanized glass.

Would this be possible with the ember? i.e. does PR48 adhere to glass more than the PEGDA resin they were using?

Thoughts in general?


#2

Washing your parts in IPA is what ruins the transparency. You can get transparent parts using Ember by skipping the IPA wash and instead curing under UV light in an inert atmosphere. I’ve done it by piping nitrogen into one of these. The key is that the oxygen level has to be below 50 ppm.

I haven’t printed with PEGDA or used silanized glass, but whole point of using PDMS is that it provides an oxygen inhibition zone right above it, which prevents resin from curing onto the window. If you were to use most kinds of glass, pretty much any resin would attach to it the same way it attaches to the build head. If it didn’t, all stereolithography printers would use glass, as it’s far cheaper, more durable, and easier to deal with than PDMS. But if silanized glass can be used instead, that would be pretty groundbreaking.


#3

Owen,
Isn’t washing in IPA just a way to remove excess resin. By not washing the parts you just end up curing the ‘goop’ that’s stuck to the surface. This makes any sort of dimensional control impossible.
Works for ‘art pieces’ and ‘show and tell’, not for lens, mating pieces, or highly detailed parts.

Now if you can clean the parts with IPA and then apply a very fine, very thin layer of clear resin that fills the line layers but nothing else…


#4

I admit that my nitrogen-cured part was in fact an “art piece”! Things get more complicated if you want tight tolerances. It may be possible to blow off excess resin with canned air before curing (goggles required!), or wash in IPA and apply a super-thin layer of resin.