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My modified Protoform

 
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Transformer
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Joined: 27 Nov 2008
Posts: 6
Location: Canada

PostPosted: Sun Jan 01, 2012 4:23 pm    Post subject: My modified Protoform Reply with quote

I have tried to post this twice, hope it works this time. My sons have a plastics business, mainly acrylic fabrication, and I thought a vacuum former would fit in with their short run fabrication business. I got the plans and kit and built the 2x4 Protoform machine pretty well according to plan. The machine worked fine and they were able to pick up a steady if irregular flow of business for it. Over the years, and the machine has been in operation for quite a few years, I have made modifications to the machine which I want to pass along. (My sons are moving their shop and dropped the machine off the fork lift so I have it in my garage to get it functioning again – but it will never be as pretty as many of the machines I have seen on this site.)
https://picasaweb.google.com/lh/photo/aXMwUDYAcakHC3IAKGCTudrStPKfN1p-cFImElsFAyM?feat=directlink

1. I installed a thermometer (ebay), seen at the top right at oven height. In spite of skepticism it has worked quite well in timing the heating cycle. The operator will also look at sag and will use a kitchen timer, but the thermometer has proven to work just as well.

2. Below the controls are 2 ball valves. The left one is the normal one for vacuum and the one on the right is for blow back. I ran in compressed air, which ties into the vacuum line. When I turn off vacuum I can introduce compressed air to help lift the finished piece off the mold. It has proven to be a worthwhile modification, but certainly not a game changer. It works well on some molds and not on others.

https://picasaweb.google.com/lh/photo/dq9yyh1w-LZ2FKCO7IgIIdrStPKfN1p-cFImElsFAyM?feat=directlink

3. Air lift of sheet holding frame. I installed air cylinders to raise and lower the sheet holding frame. The lever to the right of the normal controls raises and lowers the frame. The black knob below is a regulator that controls air pressure on the up cycle. The up motion has been trouble free. The first time I lowered the frame it came down at smash up speed, due to the weight of the frame and air pushing down. To solve this problem I installed what I call blow off valves (do not know their proper name) at the base of each cylinder. These valves control the rate of air escape, and thus the speed at which the frame descends. These valves also allow you to tune the system so the frame descends level. It all works fine – with operator education. The frame is now essentially free floating, not controlled in its right and left movement by the manual lift system. This is the reason for the white UHMW plastic strips attached to the uprights of the frame. They limit right and left movement of the frame.

https://picasaweb.google.com/lh/photo/BBxydX4_zzrKD7mcbeZdm9rStPKfN1p-cFImElsFAyM?feat=directlink

4. The problem with the air lift system is that it is either up or down and an in between stop is needed so sheets can be loaded and unloaded. I modified the now unused manual lifting system to stop the upward movement of the frame. This is the purpose of the second levered switch. It operates and air cylinder attached to the original frame lifter, which stops the assent of the frame at a level where material can be on and off loaded. Throw the switch and the frame continues its upward movement to the oven. It is not a very elegant solution, but it works well in practice.

https://picasaweb.google.com/lh/photo/NhIqNCv-W_h0Hc3O3rR4-trStPKfN1p-cFImElsFAyM?feat=directlink
Lever on the left moves frame up and down, one on right activates mid way stop. Don’t know who put the labels on.

https://picasaweb.google.com/lh/photo/M7tiR5eBy6xwC8OVZa_pu9rStPKfN1p-cFImElsFAyM?feat=directlink
Frame stopper in off position.
https://picasaweb.google.com/lh/photo/UHhGoa8mPuJ-_ojSLcJ0NdrStPKfN1p-cFImElsFAyM?feat=directlink
Now the hook on the arm will stop the upward movement of the frame.

5. Now that the manual lift is eliminated so is the switch which turns the oven on and off. I have now located this switch at the point where the frame reaches its highest point. This is a new modification not yet tested in actual use.

https://picasaweb.google.com/lh/photo/aw2XLCBN9DrlI0TBq7HU9NrStPKfN1p-cFImElsFAyM?feat=directlink
Hope this picture conveys some info.

6. The weakest point of this machine, operating it in a business environment, has been the sheet clamping system. I have tried many systems to speed up loading and unloading and this is where I am at now. I have hinged the top sheet holding frame to the lower frame. I made the hinges so the space between the frame can be adjusted for different thickness of sheets and different clamping pressure. The hinge is two tubes at 90 degrees, and an L shaped rod threaded on one end. The nut adjusts to suit the material. The other 3 sides are still manually clamped using Boeing aircraft clamps, the kind you put on with a special pair of pliers, or small vice grips. Improvement here is an ongoing but fun challenge.

https://picasaweb.google.com/lh/photo/OPHef8T5wsxcElPC6OTLntrStPKfN1p-cFImElsFAyM?feat=directlink

6. The last modification does not involve vacuum forming, and I have no pictures, but I will try and give you a wordy description. In the shop they are frequently required to cut acrylic (Plexiglas) to a specific shape. This was being done using a template and double sided tape. The tape was applied to the underside of the template, this was pressed onto a blank, and then the blank was routed to shape using a table mounted router and a top bearing bit which followed the template. You could do at most ten pieces before the tape got too contaminated to stick and then you had to replace the tape. So we used the Protoform to do vacuum hold down. Single sided foam tape was applied to the underside of the template to provide a gasket. Then an air fitting was fitted to the top of the template. A vacuum line was run off the tank of the Protoform. You set the template on a blank, attach the vacuum line, and the template and the blank are sucked togeather, and off to the router. We also installed a pressure switch which controlled the level of vacuum and only turned on the pump when it was needed. It all worked very well, however now with CNC routers is seldom used.

Thanks to everyone on this site for ideas I have picked up.




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jdougn
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Joined: 18 Mar 2009
Posts: 714
Location: Louisville KY area

PostPosted: Mon Jan 02, 2012 8:19 am    Post subject: Reply with quote

I looked at the some of the picts in the "Dennis" gallery. Nice looking work. Too bad the machine got dropped. I really like the idea of using controllers to raise & lower the plastic carrier so it was interesting to see what you'd worked out there. Hope you get it back up and running soon!
dn
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DougN - Just in case you're wondering, I got my "rating" legitimately... by posting aimless drivel, useless advice, and pointless questions.
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IMMark
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Joined: 18 Nov 2010
Posts: 189
Location: Columbus, Ohio

PostPosted: Mon Jan 02, 2012 11:00 am    Post subject: Reply with quote

Thanks for taking the time to post.
I am interested in the use of the thermometer.
Do you have any additional info. Is there a probe that goes into the oven area, how does it work?
Also, any more detail on the hinge for the frame. I would like to "upgrade" that area on my machine as well.
Thanks again
Mark
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kayaker43
Expert


Joined: 13 Jun 2007
Posts: 175

PostPosted: Mon Jan 02, 2012 10:01 pm    Post subject: Reply with quote

Transformer, thanks for sharing. I played a lot with air cylinders and many others have too. I found that restricting the exhaust as you did is better than restricting the intake to control speed because it gives a less spongy system.

I was never happy with it enough to include in the plans. The problem is fussiness of adjustment to keep it even and the need to keep tweaking it. Also a problem with cocking remains if the mold is off center. I found it best to keep the lift linkage attached to maintain level operation but if you cut off the handle it loses half its torsional stiffness. If you leave the handle on it works great but becomes a safety hazard. I also considered the safety implications of a giant air powered mousetrap.

When its all over, I thought it just complicated the machine without improving it.

I concluded the manual linkage is just as fast and more reliable for a machine this size. Can't deny the cool factor and sometimes that's enough reason to do something.
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Doug Walsh
www.build-stuff.com
Hobby-Vac and Proto-Form machine plans

Also other plans books and videos for people who like to build things
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Transformer
Newbie


Joined: 27 Nov 2008
Posts: 6
Location: Canada

PostPosted: Tue Jan 10, 2012 6:24 pm    Post subject: Reply with quote

Yes thermometer is a probe type. Probe is between the calrods and about 2.5" below them. Another advantage of the thermometer is that it is visual and in a noisy shop that is a plus.

On the hinge if I can figure out how to get pictures in the message I will try and take some more. On the bottom section of the frame I welded a short horizontal length of 1/4 tube. On the upper angle iron frame, the part that comes on and off, I welded a very short vertical length of tube. Then I bent a 1/4 rod to 90 degrees, threaded one end and fitted it in the 2 tubes. The nut on the threaded section provides the adjustable spacing between the 2 sections of the frame. Hope this helps.
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IMMark
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Joined: 18 Nov 2010
Posts: 189
Location: Columbus, Ohio

PostPosted: Thu Jan 12, 2012 8:36 am    Post subject: Reply with quote

Thanks...I really like the idea of the thermometer, I will have to pick one up.
I think I have a good idea on the the hinge as well. Thanks again for posting!
Mark
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