FEP vat challenge

Various topics related to Vat design, construction and coatings.
HTL
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FEP vat challenge

Postby HTL » Tue Jan 06, 2015 10:43 am

I decided to look into building a flex bottom vat because I was tired of redoing the sylgard/qsil vat coatings like everybody else. However, the prices I saw for FEP on a per square foot basis were pretty outrageous. So I did what I usually do, I lurked around the usual places until I found a deal...

I recently scored a (very) considerable amount of type A (general purpose) 5 mil (0.005 Inch/0.127 mm) transparent FEP and I am willing to part with some of it for the cost of postage and an envelope.

This is the deal, the first 10 registered users of buildyourownsla.com (see note below) who contact me (HTL) via private message with their name and a mailing address will get 2 - 9" X 12" (228mm x 304mm) sheets of FEP sent to them for the cost of the postage and envelope (about $5.00 US, see the notes below). What I would like for you to do is to use the FEP to create a FEP based vat or rigs, fixtures or tooling associated with FEP vats and submit photos and info to this forum on or before April 15 2015. At that time the people who submitted designs will get a chance to vote on whose design is best. Each designer will get 2 votes 1 vote will be for themselves (I believe you should think your design is best regardless) and 1 vote will be for your second best choice. The design that wins will get 10 - 9" X 12" (228mm x 304mm) sheets of FEP.

I know the reward is not that big but this is about coming up with vat designs and features that everyone can use.

Notes:

You have to have registered as a member of buildyourownsla.com on or before 1/1/2015.

Paying for postage: Send me a private message containing your forum user name, your name and a mailing address and I will send you instructions on how to pay for the postage/envelope in a return private message or email if you prefer. To send a private message log in to the forum, click on "Members" in the upper right corner of the screen, click on my user name (HTL) then click on "Send private message". Please note that it may take me a day or two to respond to your private message.

Members who have built FEP vats and have shown them or provided information about their vats in one of the forums should send me their forum user name, a link to the post and a mailing address in a private message, you will be sent the FEP, if you want it, for the cost of the postage and envelope even if the first 10 slot are taken.

This offer closes when the first 10 slots are taken.

Anyone trying to game this offer to get FEP will be ignored and declared to be a villainous rapscallion.

This is the same material I used to make my flexvat.

This is the stuff: http://www2.dupont.com/KIV/zh_CN/assets ... K26941.pdf

HL

HTL
Posts: 101
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Re: FEP vat challenge

Postby HTL » Thu Jan 15, 2015 9:56 pm

I want to clear something up.

If you decide to take advantage of the FEP vat challenge you are only entitled to 2 sheet of FEP (1 unit in the shopping cart). I reserve the right to refuse any FEP challenge purchase and refund the purchase amount for any FEP challenge purchase that does not comply.

https://www.youtube.com/watch?v=Lh8dcvj-0NA

Henry Locke

klambson
Posts: 9
Joined: Wed Dec 03, 2014 3:33 pm

My answer to the FEP vat challenge

Postby klambson » Mon Mar 02, 2015 1:19 am

Hello, I've attached a diagram of the flexvat I've built with the material HTL sent me. Before I get into the details, my gratitude and hat-tip to that gentleman...he's been very generous in his contributions to help further the DLP printing revolution.

The graphic and pix should explain most of it. Here are my notes:
Made with the smaller diameter and bell-end (although a coupling fitting would work as well) of 8” blue PVC, approximately 1/4” thick wall. The “outer ring” is cut in sections, heated and conformed to the inner ring before being glued. It serves to bulk-up the clamp section. I used one-part silicone sealant as a gasket material, but there may be better materials for this. My design goals: no laser cutting, simple machining, hardware store parts (the tensioning clamp is a mirror bracket I modified), use both sides of FEP without having to dismantle completely, easy tensioning, no center sag, future modification: rotate vat with each layer, possibly as part of the peel or to promote even wear...

lambson flexvat design.jpg


flex vat and first prints.jpg
first prints...Maker Juice G+


Plans for version 2: rather than outer tabs for the bolts, I'll use much longer sections for better surface-area adhesion to the inner clamp ring and greater surface area for gasket material to hold the FEP. I'll also add more bolts for more even tension pressure (I've got 8 total, with all 8 clamping the FEP and half those serving to hold down the tension ring.) Investigate effective lids for vat for resin storage...will help to reduce labor and resin waste that occurs from frequent cleaning.

I like the round design; it offers a greater reservoir volume. Was getting unreliable prints until I added a circular piece of 0.10" acrylic with gentle foam "springs" pushing it up against the bottom of the FEP/tensioning descender. Also, I drilled small vent holes in the acrylic so when the FEP is drawn up as the build platform raises, the vacuum, if any, is released.

dangre
Posts: 116
Joined: Wed Jun 25, 2014 4:20 pm
Location: SW Michigan

Re: FEP vat challenge

Postby dangre » Mon Mar 02, 2015 9:56 am

Bravo,
I like your take on the flex vat idea. I also would like to thank the assistance of Henry for his knowledge and sharing. I will publish my FEP comparison soon. May I ask what projector and exposure times you are using?
Dan - mUVe 1 DLP

klambson
Posts: 9
Joined: Wed Dec 03, 2014 3:33 pm

Re: FEP vat challenge

Postby klambson » Mon Mar 02, 2015 12:25 pm

The projector: Acer's H6510BD. For 100 micron layers, exposure set to 7500ms with the exception of the first two layers, and those get 20 second burns. A note about the one-part silicone sealant as a gasket material: It needs to be trimmed so the edge is slightly less than flush because as the tension ring descends, it can work to pull on the gasket if it catches. It's pretty soft stuff, not sure if it's optimal. Got some shoe goo to try. Henry's approach for making a gasket is best, where he made a mold and used a two part rubber/silicone that can have a higher durometer if desired. It's tidier, removable, and one could make it with a lip to help it maintain its form if desired. I was lazy...

I'm also getting mild waves in the Z, and I think it's because there's a slight misalignment between my stepper and the ball screw. I thought the damper and rigid bearing/rails would be enough to counter that, but no so.

HTL
Posts: 101
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Re: FEP vat challenge

Postby HTL » Mon Mar 02, 2015 8:56 pm

Very nice vat, very nice prints.

HTL

klambson
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Joined: Wed Dec 03, 2014 3:33 pm

Re: FEP vat challenge

Postby klambson » Mon Mar 02, 2015 9:55 pm

Thanks Henry. Something I forgot to mention (and apologies to anyone to whom this may have occurred earlier)...

If you want to quantify vat/FEP tension, use a tool that indicates frequency. I used a drum-tuning app for my smart phone (guitar tuners don't work). Since we've essentially constructed a tambourine, you can gently thump on it, get a frequency reading and base your adjustments on that. I did find, for example, that no matter how tight I tensioned the FEP, it seemed to relax over a day or two and return to a steady state (sorry, I've lost the notes...you'll need to get your own readings anyway).

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sgraber
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Re: FEP vat challenge

Postby sgraber » Tue Mar 03, 2015 3:21 pm

In your experience, how important is tensioning the FEP?
Research Chemist
MakerJuice UV SLA Resins

klambson
Posts: 9
Joined: Wed Dec 03, 2014 3:33 pm

Re: FEP vat challenge

Postby klambson » Tue Mar 03, 2015 4:00 pm

Putting the FEP under tension seems to accomplish a few things in my design:

1. It helps form a seal. Most of the resin never makes it to the outer gasket because the FEP is stretched tight by a rounded tension ring. This is reassuring when 20 bucks in resin hovers over a $500 projector.

2. Wrinkles, in my experience, aren't pressed out by the weight of the resin. When I flipped my FEP to use the other side, I didn't get a perfect re-stretch. Subsequent prints had a wave. Not good.

3. I suspect having a loose FEP sheet would make cleaning more difficult because it wouldn't resist wiping pressure as strongly. Who knows...could be a non-issue.

Having established those points, if you support your FEP film with an undercarriage of glass or *acrylic, I suspect the FEP doesn't need to be crazy-tight like I have mine.

*good acrylic source: Walmart photo/document frames.

dangre
Posts: 116
Joined: Wed Jun 25, 2014 4:20 pm
Location: SW Michigan

Re: FEP vat challenge

Postby dangre » Tue Mar 03, 2015 4:15 pm

Graber,
No tension - no consistency - poor results.
FEP will deform a lot under just a bit of temperature increase if not tensioned properly. Just the weight of the resin on untensioned FEP will make it bow. I was pulling my hair out once when my previously perfectly working machine would not adhere to the build plate no matter what I changed. The only thing I did differently was change the FEP. I saw that it was sagging a bit so I added a bit more tension and it printed fine ever after. I now always listen for a good, tight tone when changing out FEP and retensioning. I do not use a substrate under my FEP (.005") but I see it might be a good thing for larger parts. I will never (did I just say that?) go back to any other method. ;)
Dan - mUVe 1 DLP