www.TK560.com

[crashmann]

After a great deal of discussion on the boards, I have decided to go with a single hole platen. There will be a hole right in the middle of the platen, with a floor flange mounted directly below. There will be no plenum space. The plastic holding frame will come down 1/2" below the surface of the platen, hopefully creating a tight seal. I can run a hose from the floor flange to the ball valve, and keep the rest of the existing plumbing.



To start the project, I bought a sheet of 1/8" aluminum and hammered down the sides to create an edge 1 1/2" tall. The next trick was to figure out a way to mount it to the forming table. Wood blocks to the rescue!





Check out the photo gallery below for my progress to date. I'll be drilling out the single hole tonight and mounting the floor flange with silicone sealant. Then just screw into the wood blocks from below the table to hold the platen in place. It should be ready for pulling vacuum tomorrow night!

http://tk386.com/vac_table_platen_upgrade

I hope to add a two stage vacuum option similar to ANH Trooper's setup as well. More plumbing...

Charlie

[ANH trooper]

Looking good Charlie

Just be careful when pulling multiple moulds, the hole must be covered (as you probably have guessed).

I found my single hole table to get better pulls than a pegboard type, but that was with a shop vac. I have gone for a pegboard platen now that I am going to use a hi-vac, so we will see how it goes. Won't be problem though if I want to change it for a single hole.

Good luck with the conversion!

[Christian Van Horn]

Hey Crashmann! That looks sweet! I built my table with WAY too much xtra airspace that just sucks up precious vacuum. This takes everything out of the picture that doesnt need to be there. I am attempting to run a platten like this; two shop vacs in series thru a 1 1/2" valve and a 10 CFM vacuum pump seperately plumbed (no valve) into the same platten. as soon as the plastic seals against the platten and the vacs take the vacuum up to around 5 inchs of mercury, I slam the valve CLOSED and let the vacuum pump continue to deepen the pull. I'm dieing to see more pics of your progress, especially how you fastened the floor flange to the plate. Bolts? Just silicone? How did you seal the platten corners? Is it even necessary? Also, I take it that the sponge rubber seal around the base in the pics isnt there for anything but a cushion? Any progress you post is GREATLY appreciated! Thanks, Chris
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I GOT HELP! DAMN THIS THING WORKS!

[ANH trooper]

The sponge strip is there to help make a good seal with the holding frames, at least that is what I have used it for on my table. Personally, I think it's asking a lot of the plastic to seal itself on the edge of the platen (even though it might, every precaution should be taken to cover any possible leaks).

[crashmann]

The new platen works fantastic!!! I am seeing 29" of mercury at the platen!

I've got pictures to upload to my photo album, and video to process into a short clip. (pictures are now up at: http://tk386.com/vac_table_platen_upgrade )

I'm still learning the new procedure, and in my first five pulls, I've actually forgotten to open the valve to the surge tank. The platen has been evacuated only by the pump, and it is incredible!

I was using 1/4" wire mesh as a spacer, and the plastic was sucked around the mesh and would not let go.



Also, the plastic was drawn into every crevice of the molds and the gap between the riser and the mold. Extracting the molds from the plastic has been very challenging!



The black foam strip is supposed to help with the sealing the plastic clamping frame to the table. Also to help cushion the landing when the frame came over, otherwise it makes a loud bang as you slam it down. If the multi-hole platen was sealing against the plastic at the edge properly, the foam strip would be unnecessary.

With the new platen, the foam is just for cushioning. The plastic seals directly against the platen, just be sure to leave room around the edge to allow good contact. I did not seal the corners of the aluminum, but I did consider gooping in some JB Weld epoxy from the inside. I may go back and add that later. Also, I need to file down the corners to take the sharp pokey edge off, otherwise they may puncture the plastic.

The floor flange was mounted to the platen using 1/4" screws and nuts. I used Shoo-Goo for a sealant between the floor flange and the aluminum platen. Silicone caulk would also work very well. I had to sand the mounting surface of the floor flange smooth on the belt sander since it was very bumpy when cast at the manufacturer.



And here's the top side. I was going to grind down the bolts, but they actually help elevate the wire mesh to promote air flow to the hole. The bolts are staying!



I am really excited about this platen design, and I hope everyone upgrades to this style. You do not need a plenum space, just some wire mesh under your molds. I bought some window screen material to place on top of the 1/4" mesh, and that should make it easier to work with. Then I have to tighten up my molds and fill in the dings.

Whoo-hoo!

Charlie

[ANH trooper]

I'm glad it has worked out for you mate! I have always been in favour of the single hole as all the suction is directed to the hole and the plastic tries to suck under your mould, rather than just straight down.

I think you have just convinced me to go back to a single hole platen after a few disappointing pulls on my pegboard type platen.

Can't wait to see your video clip Charlie, and of course some piccies

BTW, what CFM rating is your pump?

[crashmann]

I'm using a Gast 1065 rotary vane vac pump. The spec sheets claims it will pull 8 cubic feet per minute, and the way I've seen the plastic get sucked down, I believe it!

I'm sorry to hear the multi hole design did not work out for you Paul. I think it's the porous nature of the MDF that is causing you to lose vacuum. If you check out Chris' ProtoForm construction log (http://chrislee.tv/vacform/index.html), you can see made an aluminum multi-hole platen with wire mesh separating the layers:

http://chrislee.tv/vacform/vacformprogress3/vacformprogress3.html

That's a really cool design, and the rounded corners of the platen will definitely prevent holes from being poked through the plastic. However, it seemed like a lot more work than I was ready to do...

Also, with a solid platen, you can work with different sizes of plastic, and use a bell jar for de-gassing silicone molds!

Good luck with going back to the single hole design, and of course, continue to post pics of your beautiful rig!

Charlie

[Christian Van Horn]

WOW! Now thats a vacuum! Thats what I'm talkin' 'bout! Congrats Crashmann on your design, and your now being able to go into the plastic coated screen manufacturing market. I think everything you've done on this new platen is perfect, with the exception of having the bolts protrude above. I might try elevator bolts above with nuts and washers below. Since I am only pulling one part at a time from my platen, the elevator bolts and some pennys should be my only spacers. I'm buying the aluminum tomorrow. My frames are 1" thick, so a platen 1 1/2" high should allow 1/2" of contact and wrap around. This should be enough for a good seal. I always believed that the piping hot HIPS plastic should seal perfectly without the foam. Just touch the hot plastic with a textured glove for an instant... instant added texture into the plastic, as this stuff really softens up.

As far as platens with plenum space and/or pegboard constructed from MDF I think you are really onto something about it's porosity. I was unable to get more than 10" mercury out of my box after taking several DAYS to seal every possibility of leakage. I swore I was sucking air RIGHT THRU THE MDF! Zero plenum makes perfect sense. Why would anyone want xtra air for their vacuum system to deal with? Thank you for this design. I really owe you one!
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I GOT HELP! DAMN THIS THING WORKS!

[TK 109]

JEEZ! it looks like you painted everything white. nice work, indeed.


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-Alex

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[Christian Van Horn]

Just a quick note to say that I finished the new aluminum platen, and pulled 29" of mercury on my first attempt! WOW! I had drilled some 3/16" vacuum holes in one area of the MDF mold, and the vacuum pump actually sucked the .100 HIPS right clean thru. I have now molded .100 and .125 HIPS with the same results...perfect. This is a 10cfm VACUUM PUMP ONLY, no tank, no shop vacs, nothing. Crashmann, YOU ARE THE MANN!!!

I have to mold .030 PET-G next... I'm worried that its gonna suck right down thru the pump! Thanks again, Chris
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I GOT HELP! DAMN THIS THING WORKS!

[crashmann]

That's great news Chris! I'm glad to hear the new platen design worked for you. It's also encouraging to hear you've pulled great detail using only the pump, and no surge tank. Nice!

You can probably change your signature now... I don't think you "need help" anymore

Do you have any pictures of the finished results?

As my friend Mike likes to say PPOIDH (Post pictures or it didn't happen )

Charlie

[Christian Van Horn]

Hey Charlie! You're right, I have to change that signature. As for pics, I can take them, but I have neither the means nor the knowledge to post them. If you send me your email address I can email 'em to ya tonight. Thanks again, Chris nomasfilms@comcast.net
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I GOT HELP! DAMN THIS THING WORKS!

[jegner]

Wow! Great news on the new platen. I've got a pump I got from Stomper, and I should just try connecting it directly, as I still don't have a decent tank. The CFM is less than the Gast, but it's worth a try. Your experiment has got me to thinking... Give it a try!

Jim

[TK 109]

hmm

maybe i should give this platen a shot. all i have is a shop vac. is that cool? i was actually thinking of making a box, and having all the heads sealed to the box, and have a single hose come off, resulting in better pulls. (just an idea i've heard from a few threads). i got three shop vacs i can use...
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-Alex

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[Christian Van Horn]

Hey Alex! I'm no expert, but from what I've seen this new aluminum platen should work as well or better than the best "box" type platen you can build. Crashmann's design saved my skin. I followed his thinking, and made my best pull ever on my first try. Built the whole platen in one day, not including shopping. The simplest designs are often the hardest to come up with. I wouldnt have thought that a seal this good was possible without some sort of foam or weather stripping. Charlie showed me the light! Chris
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I GOT HELP! DAMN THIS THING WORKS!