DIY Rotating Vacuum Exposure Frame

[mimosatexas]

I am beginning to build a large format freestanding and rotating Vacuum Exposure Frame, similar to this: http://www.digitsmith.com/attachments/3843d1234370169-vacuum-frame-exposure-unit-60-x-80-vacuum_frame_3.jpg

What I have figured out so far:

• Taking from what I have learned when I built my other exposure unit, I will be having a local metal fabricator weld two 2"x2" metal frames, 52" x 80" each.  One will hold the blanket, one will hold the glass.
• I am going to use 3/8" tempered glass unless I can find an affordable source for Starfire, but while people mentioned getting Starfire for around $10 per square foot in another thread I started, no one actually linked to a source, and every glass company I have talked to quoted closer to $30 per square foot.
• The glass will be held in place by a bunch of wide l brackets with self-adhesive weather stripping both between the frame and on the inside of the brackets to cushion the glass and to make replacement easy. http://doorentrydirect.com/images/shopimages/gianni/em100m_300.gif
• I am going to use 3 large hinges from lowe's to connect the frames like this: http://i01.i.aliimg.com/wsphoto/v0/1419269131_1/Free-Shipping-Antique-Copper-Finished-304-Stainless-Steel-Hinges-font-b-Door-b-font-hinge-Antique.jpg
• I will be using car hood struts from autozone to support the blanket frame when the unit is in the horizontal position like this: http://galleryplus.ebayimg.com/ws/web/350692406717_1_0_1/1000x1000.jpg
• I will be using toggle clamps to secure and compress the lids together like these: http://ecx.images-amazon.com/images/I/41dF9K6T1SL._AA160_.jpg
• For the blanket, I will be using 4mm neoprene foam, nylon backed, from here: http://www.hookloopoutlet.com/neoprene-sheets--nylon---smooth-skin.html
• I will be using a Gast pump I picked up used for a steal: http://www.gastmfg.com/product_detail.aspx?ProductID=117&ProductTypeID=20
• For the support structure, I will be building it out of plywood and 2x4's with heavy duty casters for easy moving.  I have a few ideas for the rotation system, but I will likely use a huge bolt with some roller bearings I already have from another project, and some kind of stop/lock to keep it in position.

Things I need help with:

• Sourcing some kind of gasket material like you see on the professional units to seal the lids together.  I have tried basically every weatherstripping available at lowe's and home depot and none work very well, and all would fail on a unit this large.  I am looking for the half circle rubber style material that basically looks like a semi-inflated bike tire.
• Any tips on how to make the rotation fluid when switching between horizontal and vertical.  Any photos or videos of how the professional units work would be helpful.
• Any tips on how to connect the pump to the blanket or the frame.  The system I am currently using on my other unit is clunky, basically using brass pip fittings and valves drilled through the frame with sealant.  Even with teflon tape, they don't seem to hold the best vacuum.

I'll post photos of my progress as I build.

[ScreenFoo]

The gasket material I started using is just the same closed cell neoprene most everyone uses for blankets, in a rectangular cross section tape.  McMaster Carr sells it by the roll, IIRC I paid 25 bucks for a 25' roll of 1/2"x1" x-section. 

Starfire is something I looked into too--then I started asking around for 'low-iron' glass, or failing that, the glass that 'doesn't look green on the edge' might get your supplier clicking.  It's still not cheap, but I got quotes around 150 for around 10 sq ft. in town here.  Them trademarks cost some money.     

[mimosatexas]

When I called for quotes I made a point to say low-iron first, but they all default to starfire as soon as I describe it as not being green.  I even had some rep tell me "all glass is green", and for him I had to actually name drop Starfire, then he got weird.

I thought about just using neoprene or foam tape, but I was thinking the other stuff must be superior since it is used on all of the units I have seen online.

[Binkspot]

Have the frame fabbed out of aluminum, steel tubing will be heavy IMO. That's 44 linear feet of 2"x2" tubing.

Pillow block bearing will work well and can be bolted to the stand. The fabricator can weld a short shaft onto each side of the frame that will slide into the bearings. They are self centering so alignment is not critical.

You will need a locking mechanism to hold the frame vertical or horizontal depending on the task at hand.

Have the shop weld a 3/8" half coupling in the frame to connect the vac pump to. With the 3/8" coulpling it gives you options to thread fittings into it like a barb fitting or hose end

[mimosatexas]

Great info!

For the pillow block bearing, would you suggest a specific size or should pretty much anything work?  Here is what I found quickly: http://www.amazon.com/b?ie=UTF8&node=220003011

For locking, I was thinking of having a block on the stand that stopped it for each position (probably with a strip of some kind of rubber to absorb any shock from the frame touching it), then have some kind of simple catch that can be pushed or rotated on the other side of the block to hold the frame in place.

Any suggestions for keeping the thing from slamming down if i lose my grip on it somehow while changing position or will the bearing prevent quick changes like that?

[Binkspot]

Bearing is exactly what I'm talking about. They will move effortlessly.

If it was me I would have a disc out of 3/8" plate about 12" dia welded on one of the shafts between the frame and bearing. I would make a friction with a heavy bolt, spring and block of nylon to control the speed of it like a brake. I would also drill two holes in it 90 degrees apart to put a spring pin in to lock it up and down. Hard to explain but I would also cut a slot the the disk to put a bolt or pin in as a positive stop if it was to get away from you.

If you have access to a fab shop and a little creativity the posiabilties are endless.

[PhilR]

For the gasket I'd suggest looking into automotive door sealing gaskets. They come in a very wide variety of profiles.

[starchild]

Hey mimosa are you aware of  t-slot extrusions? It's the aluminum exterior material that you see on M&R equipment.. You get a modern industrial look without the welding and cost is lower.. Hinges, latches, panels and everything else to construct your unit and achieve a modern industrial look with no special tools..


http://www.8020.net/T-Slot-1.asp

http://www.8020.net/Solution-1.asp


http://catalogs.8020.net/app.php?RelId=6.1.7.4

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[jvanick]

8020 is great, easy to work with, and it's strong too...

check their ebay store at '8020 garage sale' ... they sell 'blem' extrusions there, which are normally a bent corner, or scratch here and there...

I built a 4'x4' CNC machine out of it a few years back, and it's still running as good today as the day I built it.
(even holds accuracy to .003")

-J

[mimosatexas]

Wow, great concept, and I wasn't aware of it.  I actually have another project I'm working on where this would solve a few problems I've been struggling with (parallel lift large format one armed bandit with interchangeable tops for printing different substrates).

I'll compare a quote for their stuff with my local welder.  Thanks!

[ScreenFoo]

I could only guess that there are gaskets that could be better, but the shop here is at over 5000', and we have been pulling 20" of mercury with that seal for years.  Automotive ones should be good as well, being chemical and UV resistant.