Build Your Own SLA/SLS

Thank you. Does any of your advice change if I tell you there is a plexiglass layer beneath the vat film?

sure does

flexvats work so well because when the FEP film is under tension it acts like a flat plate during the exposure. After the exposure as the build plate rises the fep film will bulge slightly upwards at points where the model is touching the film, when the fep film lifts it creates peeling edges at any point the part touches the film, these peeling edges allow the part being printed to separate from the fep easily (I have printed a part successfully using a flexvat that I forgot to lock down, the vat didn't even move).

The problem with fep film sitting on an acrylic window is that if the film is under any tension at all it will stick to the acrylic due to vacuum so when the build plate rises the fep does not bulge upwards so you do not get the peeling effect, you might even have a suction problem depending on the surface area of the layer being printed.

I am testing an acrylic window for a new vat design that looks like this to help with the vacuum problem:


HTL

Thanks! Any idea why it has worked quite a few times, but now does not? The part that is frustrating me is not that it fails, but that it is erratic! Unpredictable!

HTL, Jon has one of my test vats that is the self-sourced LIttleRP2 style http://imgur.com/a/yoYyl and the underplate does have perimeter venting, it does not have the raised masked edge that your current V5 testing vats do however. The vat is running low tension on it as in my testing I have found the higher tension can contribute to uneven layer lines with the part shifting due to higher stresses of a shallower release angle, however at the cost of lower film life, risk of localized distortion etc.

Jon, if you add a base "add sole base" option and reprint does the part fail in the same place?

I think the issue may be that the FunToDo is harsher to FEP than some other resins, it definitely destroys PDMS and that the film may have lost some of it's non stick qualities from simple use. The small attachment base in comparison to the flared feature on the part simply can't hold on in the presence of increased stickiness of the film + larger cross section of the part. You are just seeing the issue earlier on in the life of the film as there was less margin to begin with, so not saying the film is toast, but that the part likely needs better adhesion to the build plate, either through perforation / roughening or more surface area on the bottom of the part (CW base support).

At Brad's suggestion, I started using B9 Creator to add supports to my structures. I reoriented one, after which it printed correctly twice. Another one printed correctly 4-5 times. I also discovered a few stray support feet in the vat, which could well explain a few of the failures. I have not been draining the vat each time (nor counting the feet!). So. Back to reliability.