To further comment on trapped volumes and building techniques to overcome, my
experience with Allied Signal EXactomer 5201AR (SLA500/Argon Ion Vinyl Ether
Resin) showed improved tolerance to trapped volumes compared to Ciba SL5180
Epoxy resin.
Viscosities of both were about the same, but the surface tension of the
5201AR seemed to be lower, resulting in improved recoating performance (more
liquid resin movement per sweep and lower z-waits). Lower surface tension
also permits consistent .005 inch layers in the SLA500 without layer
dewetting (as seen with SL5180 epoxy).
The downside is the stuff is more difficult to post-process than epoxy (and
acrylates for that matter). Parts often are tacky if not diligently washed,
while additional curling and distortion are more likely if post cure (UV
and/or thermal) is not carefully controlled.
I have built parts head-to-head in epoxy and vinyl ether in the SLA500, and
had some unavoidable trapped volumes succeeed in vinyl and were a ROYAL PAIN
(but eventually succeeded) in Epoxy.
Overall, part orientation is still the most infuential variable to the SLA
trapped volume problem (in my book), but may not always be the total
solution.
Steve Deak
Hasbro Toy Group
Cincinnati, OH
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