Vac Form Question

Discussion in 'Replica Costumes' started by HighlanderFX, Sep 8, 2015.

  1. HighlanderFX

    HighlanderFX Well-Known Member RPF PREMIUM MEMBER

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    What does it mean when I get little fins on the sides of my vac formed object? My vac form table right now is 12" x 18" with the object being 10" x 8" respectively. I suspect that the reason for the fins is due to the plastic being stretched too much? So if I change my table to 18" x 18" would that fix it?



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  2. collinE83

    collinE83 Well-Known Member

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    I noticed a few things contributed to this happening for me and the chances of the fin effect happening was reduced as I adjusted each.

    Factors can be: plastic too thick, not heating plastic hot enough, vacuum too weak, square vac table while forming over a round buck.

    Each of these kind of tie into each other. The thinner the plastic, the easier it is for the vacuum to pull it over the piece. The stronger the vacuum, the thicker the plastic can be to pull. The hotter you can the plastic, the easier it stretches and forms. etc.

    I do notice the fins happen the most in the corners of the square table I'm using. Basically, if you think about vac forming a round piece inside of a square frame, the sides of the square frame are going to be closer to the object than the corners. The sides will pull tighter and prevent bunching of the plastic. However, the plastic in the corner isn't pulled as right, being further away from the buck. You're going to have more plastic in the corners, which means it's going to bunch up more around the object in the corresponding corners or slack areas.

    I recommend making sure to have thin enough plastic, make sure you're heating it hot enough, make sure the vacuum has a good enough seal to make the suction stronger, and lastly, see if there's anything that you could add on your frame so instead of a square frame, you have a more circular frame, it'll pull more evenly around the object. Hope that helps.
     
  3. HighlanderFX

    HighlanderFX Well-Known Member RPF PREMIUM MEMBER

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    Thanks for the tips Collin! I'll give them a try and see if that fixes things.
     
  4. clonesix

    clonesix Sr Member

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    the effect is called "webbing" and it is caused by the buck being taller than wide. The material has stretched so much to cover the vertical distance, that it is unable to "shrink" back to its original size before being sucked down onto the table. It also happens when two objects on the table are too close to one another, and there is a web between the two.


    To fix this, you need an object to push the hot plastic down onto the table before it has a chance to stretch under the power of the vacuum. You can use a piece of wood or plastic, just don't burn yourself.
     
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  5. HighlanderFX

    HighlanderFX Well-Known Member RPF PREMIUM MEMBER

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    Got it. Thanks!
     
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