Vacuum forming machine problem

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  1. #1
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    Default Vacuum forming machine problem

    Hello guys,

    I hope im in the good section.

    Machine spec
    7 cfm vacuum pump
    10gal air tank

    So I have a problem with my vacuum molding machine. My problem is when I going down with my hot plastic sheet and I open the main valve the plastic doesn’t go all the way down only on the side of the part I want to mold (sixth pic).

    I open my main valve when I read minus 25 on the gauge. I try to figure out. Is it because my pump is connect to the gauge and to the tank with a T fitting and a ½ hose. The tank is connect to the main valve with a T with a 1 inch hose and the valve to the plate (like you see on pictures fourth and fifth).

    Update, i add a seal around the platen but i still have the same problem.

    I really don’t know. Hope you guys can you help me

    Vacuum forming machine problem-img_2522-jpgVacuum forming machine problem-img_2523-jpgVacuum forming machine problem-img_2525-jpgVacuum forming machine problem-img_2526-jpgVacuum forming machine problem-img_2529-jpgVacuum forming machine problem-img_2531-jpgVacuum forming machine problem-img_2542-jpg

    Regards
    Simon

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  2. #2
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    Default Re: Vacuum forming machine problem

    Possible causes:
    1.- The plastic sheet solidifies too soon.
    2.- The porosity of the base material is not enough and there is a large pressure differential between the top and bottom of the table top.
    3.- You might need a bigger vacuum tank.

    If the plastic sheet is still moldeable when this happens, then try opening a bunch of small holes around the edges of the part or mill a slot half way (not the complete thickness of the table top material) around the part. If this solves the problem, change the table top material or its thickness.

    Regards,

    kreutz

    Last edited by kreutz; 11-14-2014 at 03:09 PM.


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    Default Re: Vacuum forming machine problem

    thanks for you advice,

    before the platen i have now (hole 1/16 of an inch) i use one xith 1/4 of an inch got the same result. Under the platen i have a 1/4 thick mdf.

    I will try to add a steel mesh under the platen.

    For my tank i saw a bigger machine with the same set up 10gal tank.

    thanks



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    Default Re: Vacuum forming machine problem

    I also think the tank capacity is ok.
    Some people have used peg boards on the table, although I think the peg board's holes are too big.



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    Default Re: Vacuum forming machine problem

    I used that thinking im a genius but yes its too big



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    Default Re: Vacuum forming machine problem

    What is the plastic you are using?



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    Default Re: Vacuum forming machine problem

    Vacuum forming machine problem-vactable-jpg
    above is a flopper from another site see how the heating elements go to the edge and the whole thing distributes the heat to all the plastic?

    When looking at the heating area on your unit , it looks to me your just heating in strips without dispersion. If that is the case then you'll never heat up the sides of the plastic to mold to your platen and seal up correctly.
    look on the discussion board @ tk560 in the vacuforming section and you will see a lot of different setup that work and different ways to get there using inexpensive materials.

    also rounding the platen will help seal the plastic to the platen for good draw here is my platen for my 2'x2' pieces. rounded corners and rounded sides for the plastic to adhere to. works great
    Vacuum forming machine problem-dscf4424-jpg

    this is the (my first version of kick panel with speakers in them) molded part with a 3 inch draw on the speaker part of the panel using textured 1/8 abs.
    Vacuum forming machine problem-dscf4428-jpg



    Quote Originally Posted by simnic View Post
    Hello guys,

    I hope im in the good section.

    Machine spec
    7 cfm vacuum pump
    10gal air tank

    So I have a problem with my vacuum molding machine. My problem is when I going down with my hot plastic sheet and I open the main valve the plastic doesn’t go all the way down only on the side of the part I want to mold (sixth pic).

    I open my main valve when I read minus 25 on the gauge. I try to figure out. Is it because my pump is connect to the gauge and to the tank with a T fitting and a ½ hose. The tank is connect to the main valve with a T with a 1 inch hose and the valve to the plate (like you see on pictures fourth and fifth).

    Update, i add a seal around the platen but i still have the same problem.

    I really don’t know. Hope you guys can you help me

    Vacuum forming machine problem-img_2522-jpgVacuum forming machine problem-img_2523-jpgVacuum forming machine problem-img_2525-jpgVacuum forming machine problem-img_2526-jpgVacuum forming machine problem-img_2529-jpgVacuum forming machine problem-img_2531-jpgVacuum forming machine problem-img_2542-jpg

    Regards
    Simon


    Last edited by keastab; 12-15-2014 at 12:31 PM.


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    Default Re: Vacuum forming machine problem

    I would be inclined to agree that the heating of the sheet is non uniform. It is crucial to have even heat distribution over the whole sheet and also I`d say looking at the photo of the moulded piece that the material is wet. By wet I mean hydroscopic materials like ABS absorb water and when heated up to Vac forming temperatures it boils causing and orange peel effect at best and like chronic acne at worst. You need to dry it out in a warm dry place for a day or more depending on how wet it is. Poor vacuum is also a possibility, have you enough vent holes through the bottom of the mounting board ? For detail within the mould you really need to have through holes (witness holes) around all the edges . Also the mounting board needs to rise to 1/2 " above the sheet level to create a temporary seal so that you don`t exhaust your vacuum before the sheet has pulled down fully over the mould. I Used a plywood base board with a neoprene gasket around the perimeter with a central hole ( 2" Dia ) through to the mould with the mould bolted or screwed to the base board with a thin washer between the base ( usually on the mounting bolts or screws ) and underside of the mould to allow air flow. As you are no doubt aware vacuum forming is something of a black art and every tool is different and has different possible problems. Your immediate problem is heating though. Best of luck and post again if you need more pointers )



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    Default Re: Vacuum forming machine problem

    When I look through your setup, I am struck by how slowly you move air. A 10 gallon tank should work IF you have the hoses and mold bade with adequate flow potential. Your hole sizing in the platen needs to be something in the order of #21 holes in 3/4 inch spacing BARE MINIMUM. I use dedicated mold bases so I minimise sheet goods waste. Go over to the TK560 site and look op the threads on troubleshooting and mold lock.... LOTS of good stuff there.



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