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TK560's vacuum forming machine down for repairs

 
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jegner
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Joined: 30 May 2003
Posts: 2134
Location: Texas, USA

PostPosted: Mon Jun 27, 2005 7:44 am    Post subject: TK560's vacuum forming machine down for repairs Reply with quote

Well, the vac-former finally needed to be repaired. The holding frame used strips of that non-skid material to 'grip' the plastic, has finally fallen off. Now, each pull just slips away from the holding frame. I'll need to rework the texture material. I'm thinking some sort of JB Weld epoxy mixed with sand. Paint that on, and let it dry and that sould be the end of this problem. We have lost several pulls to this issue. Now its time to fix it.
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BAD_CALVIN
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Joined: 16 Jun 2005
Posts: 8

PostPosted: Mon Jun 27, 2005 11:35 am    Post subject: Reply with quote

that or just scoring it, whatever is easier. Is it doing it in the same spot every time?
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jegner
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Joined: 30 May 2003
Posts: 2134
Location: Texas, USA

PostPosted: Fri Jul 01, 2005 8:22 am    Post subject: Reply with quote

Well, I've reworked some of the issues I had been having with the holding frames, and vacuum source. The holding frames now sport an improved grip material. Before, I was using some 'off-the-shelf' non-skid material for steps made by 3M. Good stuff, and had the right amount of 'bite' but over time the adhesive that held it to the holding frames weakened by the heat, finally reached a point where it no longer held. I wound up with several bad pulls because of this. Now, I have applied JBWeld, an engine epoxy to the holding frame, and sprinkled playsand to the wet epoxy. The result appears to be a stronger 'bite' to the plastic. The JBWeld is suppose to withstand temps. up to 300 Degrees C. so thats twice what I need it for.

I'll test it this weekend and let everyone know how it goes.

Also, the vacuum set up has changed. Before I was using a 3hp shop-vac to do all the work. Now I have a 6.5hp sho-vac. Initial test were inconclusive as to any difference between the two, so more test are necessary. I have tried to run the two in parallel, one shop-vac sucking through the other, but my tests have been inconsistent. There may be a method or trick to get it to pull better.

The 6.5 shop vac has a large collection chamber, and that space may need to be reduced with a plug of MDF cut to just fit inside. This would reduce the volume inside the shop vac. I have seen dual vac setups in other books I have, and they say to make a box as small as possible to get a better vacuum. hmmm.
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yanvaq



Joined: 13 Jul 2005
Posts: 1
Location: bay area calif

PostPosted: Wed Jul 13, 2005 12:32 am    Post subject: Reply with quote

Hi I just stumbled on to your site abuot your vac former impressive.
however I do this for a living and would point out that you dont vacform any thing it is a misnomer that seems to keep going around .
what actualy happens is that you evacuate the air out from under the plastic and tha ambeant air pressure pushes the plastic down around the mold . so technically you are pressure forming nuf said . 2 shop vacs probably will not make the parts pull tighter only faster you need more inches of murcury than they can generate . if you hahe a gaust pump it will do the trick you just need a 10 to 20 gallon storrage tank and the proper valve that will work with vacumme . you dont have enough vac thats why you are having to use risers but they may be a good idea any way. if youn cap the ends of the tube shaped parts with domes they will release better . if you e-mail me I can give you the info for a special casting resin that I use for production mold that have thousands of pulls and are still going strong . again vary impressive
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nateman7097



Joined: 30 Jul 2005
Posts: 4

PostPosted: Sat Jul 30, 2005 3:37 am    Post subject: Reply with quote

You should try using regular vehicle weather stripping. The rubber surface shouldn't allow the plastic to slide around when you are moving the frame. The sand could in turn scratch up your glossy finish and cause you more work. I have also never had a positive experience with JB weld or OXY weld..
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