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Finally 2x2 table tweaking questions

 
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onedge30
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Joined: 22 Nov 2006
Posts: 19
Location: Florida

PostPosted: Mon May 27, 2013 2:13 pm    Post subject: Finally 2x2 table tweaking questions Reply with quote

Hello, all.

I have gone back and read thru several threads and have not found answers to these few questions. Please pardon me if I have missed them elsewhere.

I am building the basic 2x2 Thurston James Design. Most of the parts sat for 4 years while life just flew by, but now I am pulling it all together.

On the vacuform platen surface, what about using a nice bead of silicone around the edge to form the seal? Instead of the weather stripping.

Building the frame, how much of a space did you allow on the hinge side? Did you put 3M grip tape around the entire frame top and bottom?

The oven, has anyone every insulated it with fiberglass insulation on the bottom and sides? Did this lead to better heat or just faster break down of the concrete board?

The oven, has anyone found a thermostat regulator or dimmer for the electric running to the elements of the oven? Or do most just have an on/off switch?

Thank you for everyone's great posts and builds.

Cheers,

Jeff
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IMMark
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Joined: 18 Nov 2010
Posts: 189
Location: Columbus, Ohio

PostPosted: Wed May 29, 2013 8:39 am    Post subject: Reply with quote

Hi Jeff
I can address the "dimmer" switch..look into infinity switches...they are used on electric home ovens in the kitchen, and work well.
Mark
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crashmann
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Joined: 27 Sep 2005
Posts: 501

PostPosted: Thu May 30, 2013 11:31 pm    Post subject: Reply with quote

Hi Jeff,

I can answer a couple of your questions:

Regarding silicone on the forming platen, are you suggesting adding that around the perimeter to encourage a better seal? If you have a metal platen surface, it probably wouldn't hurt to try it out. If it doesn't work, you can always just peel it off Smile The best thing is to ensure the surface is at least 1/2" higher than where the clamping frame holds the plastic. The hinge for the frame will stay in a fixed position, so you can really lean down on the front edge to get a good seal.

For the flip flop frame, check out my dimensions for the 32"x24" on this page:
http://tk386.com/vactable/

It looks like I had 6" from the edge of the clamping frame to the pivot point. This provided enough distance to reach the edge of the oven. I did not use any grip tape inside the clamping frame. Instead I used cam clamps from Rockler Woodworking:
http://www.rockler.com/product.cfm?page=10602



The eye bolt spread apart from the cam clamp pulling on it, so be sure to have plenty of spares on hand. Or, if you have a friend with a welder, weld the loop shut. Also, the black plastic washer got torn up on the slot, so you should add a metal washer underneath.

I did not try insulating the oven. I don't think you'll prevent much heat loss by adding insulation on the sides and bottom, and I suspect it may contribute to the Hardibacker board cracking sooner.

My oven just used an on/off switch and ran at the full 20 amps on a 120 volt AC circuit. Be sure to pre-heat the oven before pulling that first sheet, or you may ruin the first pull of the day.

Hopefully this answers your questions and you can get your project rolling again!

Charlie
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onedge30
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Joined: 22 Nov 2006
Posts: 19
Location: Florida

PostPosted: Wed Sep 18, 2013 6:12 pm    Post subject: Reply with quote

Thanks guys. I have some finished pictures to share. I hope I do this right, it has been a long time since I have posted picture to a board. Embarassed

I did use silicone for the edge seal. Seems to work well.

Frame spacing worked out. The hinge side of the frame, I may have goofed and not left enough room for the plastic sheets!!!!! Shocked I am trying to work thru this issue.

That is what I was thinking with the concrete board breaking down faster if insulated. So, no insulation.

I have an on/off switch for the oven. Works fine. Have a new problem. Used and extension cord to wire the oven. It is only a 14 gauge. It is warm during use and the heating coils do not get red, so, I am thinking of getting a larger gauge cord and replacing the 14g hoping for better heat.



Oh this vac pump is a beast!!! It will pull a 27 in vac in like 45 seconds in the tank!!! OMG!!! A little over kill.







You can see that the first sheet I tried to pull did not get hot enough. But the second did just fine. 30 min heat time is not good. (this is .080 HIPS) After trying to change the cord, I may have to think this over.

I really wanted to post some photos so that anyone else can see my variation. Everyone's posts with pictures have been so helpful in my completion of this project!!! (Hmmm, I rotated the photos in photobucket, but they came thru un-rotated. Question ) Laughing Very Happy Very Happy
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Fredo
Master


Joined: 21 Mar 2007
Posts: 251
Location: Kingdom of Nye Area 51

PostPosted: Thu Sep 19, 2013 9:51 am    Post subject: Reply with quote

Most of these TJ type VF, though under powered, will do the job if the oven gets hot enough.. If after you check and find out you're putting out 2400 watts, your next step is to insulate.. Start with the floor.. Fiberglass will work on the backside of the floor... If it cracks, it cracks.. It was never meant to be used like this to begin with.. The radiated heat of the oven floor itself, not only that of the coils heat the plastic.. A cheap IR point and read thermometer is a great tool to see how your evenly your plastic is heating... It pays for itself..
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it would be reasonable to shoot back with your own gun...The Dalai Lama..Seattle 2001
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crashmann
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Joined: 27 Sep 2005
Posts: 501

PostPosted: Fri Oct 11, 2013 1:38 pm    Post subject: Reply with quote

onedge30 wrote:
I have an on/off switch for the oven. Works fine. Have a new problem. Used and extension cord to wire the oven. It is only a 14 gauge. It is warm during use and the heating coils do not get red, so, I am thinking of getting a larger gauge cord and replacing the 14g hoping for better heat.


You'll definitely want to upgrade the extension cord. I used a 12 gauge 25 foot cord on my 32"x24" oven and it also got a little warm at the outlet, but it was also carrying a 20 amp load!

Jim used 10 gauge wire for his oven power cord and put a plug on the end.

I see Harbor Freight sells 10 gauge extension cords. They are expensive, but that's better than a fire because of a cheap cable!

http://www.harborfreight.com/25-ft-10-gauge-triple-tap-extension-cord-66495.html

Charlie
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DarthVader1
Expert


Joined: 04 Nov 2007
Posts: 193
Location: Phenix City, AL

PostPosted: Wed Feb 19, 2014 10:49 pm    Post subject: Reply with quote

I've being having pretty much the same problem all these years with my TJ designed VF machine. Not heating enough, and unable to use for vac-form, forced to use my kitchen oven (which takes more time for me, and waste of a lot of plastic) to to the castings I've being making since 2009.

I should try a 10 gauge extension to see how it goes.
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jegner
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Joined: 30 May 2003
Posts: 2144
Location: Texas, USA

PostPosted: Wed Apr 09, 2014 2:36 pm    Post subject: Reply with quote

I would upgrade to much thicker gauge wire for the oven. 5 to 10 minutes to initial oven preheat cycle, and 2-3 minutes per sheet is all it should take.
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