Need suggestions

[odino]

Hi
first post after presentation

I'm building a bottom-up SLA printer together with some friends. Direct projection, no mirror at the moment.
In this alpha/test machine I have a vat with a teflon film (not completly transparent... a little opaque but still works great. The UV pass well and the resin cures well) and under the vat a glass to prevent the resin goes down to the projector in case it breaks the teflon film.
As build plate I use a plate of metal sheet with holes.

In my first tests (about 20 i think now) the first layer adhere perfectly on the build plate (so well that I have to use a knife to remove after the printer).
But after some layes (about 10) the new layer don't stink on the previus but on the film (but if I peel of the piece with mi bare finger from the film it come out easily). I know when it adhere on the previus layer because I hear the "snap" sound of the new layer peels of from the film when the z axis lift up for prepare the new exposure.

I was wondering... my telfon film is not good enough? Or I make some mistake about the starting height (in the last test the bottom plate touch the film. Completly tight).

At the moment I use FunToDo resin.
7 second of exposure for first 3 layer. 4.5 second for the other. 0.3mm LH.
I know these are high times, but I try this to make some test. But it didn't work...

I'll post some photo as soon as possibile.

Sorry for my bad english :\

[PacManFan]

You should read up on some different Vat separation techniques. Most bottom - up printers use a tilt mechanism to help release the current slice from the vat bottom. This helps to peel away the slice. Others rely on a layer of PDMS. There are also slide & twist mechanisms , or very flexible vat bottoms.

[odino]

Hi thanks for reply

These are options that I have suggest to my comrades. But now they want absolutly avoid something like tilt or slide system. They said "it's noisy"...
I told them to make some adjustment but they don't want to change the project at the moment and try as much as we can to follow this way... soo hard to deal with them...

Can you suggest me where I can buy some PDMS (If I remember correctly PDMS should be Sylgard elastomer) or FEP adhesive backed tape? Even if the shop are located in USA or outside the europe...

[Phife]

Ive done lots of experiments with PDMS and adhesive backed FEP on glass and lexan. Neither one is really ideal. Best simple, passive, quiet release method ive found so far is the Flex Vat. Still much more research to be done in the release methods. Nothing has proven to be 100% effective.

[odino]

mmm
So flex vat should be the way...
What's you actual configuration Phife?
When I think about flex vat in my mind I see something made with a single film o FEP (I have found 0.05mm from Germany but I think is too much thin) or something made from a tablet protector film (if I remember correctly these protector film were made by PET... today is shopping day. I'll go to a shop and search for this protector film).
Th table protector film could be a nice one maybe. Quiet strong e flexy maybe.