Flex bottom VAT

Various topics related to Vat design, construction and coatings.
Finhead
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Joined: Fri Jan 31, 2014 12:56 pm

Flex bottom VAT

Postby Finhead » Mon Jul 14, 2014 11:53 am

Some have asked about the Flex bottom VAT that I had been messing around with. The first version worked but not 100% as it was too flexible and would sag with the weight of the resin, I cured this by clamping a piece of glass under the FEP/poly combination which worked but made for a few ripples on the edges.
This is my new prototype I cut on the CNC yesterday, the welding on the VAT walls are not that great as I didn't have the proper gas for what I was doing. :/

Pictures should be pretty self explanatory if you have any questions ask away. It's comprised of 3 pieces the VAT mounting base which has the ring to stretch the FEP, the VAT bottom clamp and the top clamp/walls. The FEP is clamped between the aluminum pieces with a little silicone bead around the edge and screwed in place with 18 6-32 machine screws. Which will then be pulled down over the base ring with 6 1/4" bolts until stretched nice and taunt, the ring was made rather tall so it could be stretched further as the film ages and or stretches out more.

As I say this is a prototype so the base is just MDF coated in Urethane resin to seal it off and make it far stronger, I will be testing how well it works today/tonight once my printer has been completed (rebuilt to remove the mirror) and report back.

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Glacian22
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Re: Flex bottom VAT

Postby Glacian22 » Mon Jul 14, 2014 2:48 pm

Looks good! I've been playing around with a similar design, but so far I've just been using adhesive instead of a clamp.

Finhead
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Joined: Fri Jan 31, 2014 12:56 pm

Re: Flex bottom VAT

Postby Finhead » Mon Jul 14, 2014 5:40 pm

Glacian22 wrote:Looks good! I've been playing around with a similar design, but so far I've just been using adhesive instead of a clamp.


Yes my first version was using something like that, it just did not stretch the FEP near enough and would allow the resin to pool in the center making for odd cure or no cure near the center.

Happy to report this works better than I hoped it would, peel is effortless and the model finished with no issues at all related to the peel. I am not going to post the result since my exposure times are all out of wack now since I took the mirror out of the light path it's over curing by quit a margin. But I will try again at a more standard setting and see if I can post a image tonight. This mod and getting rid of the mirror are the 2 best things I have done for this printer so far. :)

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258cj7
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Location: Kentucky, USA

Re: Flex bottom VAT

Postby 258cj7 » Mon Jul 14, 2014 9:32 pm

Wow, Great idea! I tried to stretch some fep but couldn't get it taught enough.
Is there any danger of the fep rupturing and leaking resin resin onto the projector? How thick is the film?

dangre
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Location: SW Michigan

Re: Flex bottom VAT

Postby dangre » Mon Jul 14, 2014 10:28 pm

If I may ask, where do you get your FEP from and what thickness?
Dan - mUVe 1 DLP

Finhead
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Re: Flex bottom VAT

Postby Finhead » Mon Jul 14, 2014 10:43 pm

258cj7 wrote:Wow, Great idea! I tried to stretch some fep but couldn't get it taught enough.
Is there any danger of the fep rupturing and leaking resin resin onto the projector? How thick is the film?


All props should go to HP_ as he was the one that came up with this and showed me his design. I just built my own version and posted to help anyone interested in it. :)

I don't think the FEP would rip or puncture from the normal use of the lift/peel. Now if you get anything in the VAT that is sharp it will for sure puncture the VAT bottom. The FEP is very strong and stretches quit a lot before it will break and really there is no stress on it besides the peel action which is minimal the way it works.

That being said I am always worried about "what if" so I have a piece of .020" polycarbonate silicone to the very bottom of the VAT base (the blue MDF piece) so if it did happen to break it would simply fill that area and not go everywhere, at least that is the plan for just in case. ;)

The FEP is .0035" from McMaster Carr it is the adhesive type with the adhesive removed from the build area after it was clamped/siliconed in place, just used a little acetone to remove it. Only reason I used this was because it was all I had on hand and they wont ship to Canada so it's hard for me to get. I am getting a friend to get some .005" to me soon so I will be experimenting with that soon.
http://www.mcmaster.com/#fep-film/=sua9fi

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PacManFan
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Re: Flex bottom VAT

Postby PacManFan » Mon Jul 14, 2014 11:36 pm

Thanks for the tips! I had been thinking about making a vat bottom just out of FEP. I have a very thin layer of polycarbonate now with adhesive FEP. The thin layer of poly gives it a good flex during separation.

Finhead
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Re: Flex bottom VAT

Postby Finhead » Tue Jul 15, 2014 12:47 am

PacManFan wrote:Thanks for the tips! I had been thinking about making a vat bottom just out of FEP. I have a very thin layer of polycarbonate now with adhesive FEP. The thin layer of poly gives it a good flex during separation.


Yes that is actually exactly what I had for my first prototype, it worked pretty well but the plastic will eventually start to stretch and not want to come back to shape so I ditched that Idea for just FEP. It might have worked had I made a design like this so I could re tension it but I knew this would work so just went for this instead.

EdgE
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Re: Flex bottom VAT

Postby EdgE » Thu Jul 17, 2014 4:45 pm

Tnxs, great writing, I think this thread is the real discussion, where it's all about...
Pacman, how will your FEP-only vat look like?
Not affraid of sharp prints, sticking through the foil?
I'm also dreaming of these kind of solutions... (Getting enough air under the foil, very thin foil so no shadow images, etc etc)

I was also thinking about this, especially after seeing the 'Almetec Master Plus' printer.
That's a very nice solution! Also because of a very thin layer of resin, which will be 'refreshed' after every layer.
And especially that refreshing looks important to me. 'Re-shaking' the resin during building could also be a key factor...
Especially after long builds, it's good the shake te resin. That's what I'm currently trying out.

Since I'm logging all my prints, including photo's, I discover, that the resin is degrading a lot over a couple of days (without refilling the vat).
Maybe stupid and every one knows already... But in my case, the resin will stay in the vat, in an almost dark printer. And ofcourse, I'm shaking/stiring the resin before a new print. Every time these prints with 'older' resin will have worse quality. First I thought my printer was not very good designed, or both mirrors are creating this issue, but now I'm quite confinced that the degradation will be the issue. The resin is shifting and the light liquid on top will faporize and the 'dlp-resin' looses it's quality. (I still need to prove this, I'll let you know when I'm sure...) ;)
What are your idea's about this?
Last edited by EdgE on Fri Jul 18, 2014 1:55 am, edited 1 time in total.

Finhead
Posts: 276
Joined: Fri Jan 31, 2014 12:56 pm

Re: Flex bottom VAT

Postby Finhead » Thu Jul 17, 2014 4:53 pm

Edge this is a FEP only design unless you accidently wrote Pacman instead of Finhead. ;)

I have let the resin sit for 2 weeks at a time with a stir it's fine for printing. When I was using mirror design it was a issue fie sure, some of the resin that refused yo cure with my folded design Is now curing without iissue.IMO the folded design is limited and complicates the print process too much.