Vacuum forming machine problem

[simnic]

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.

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).

I really don’t know. Hope you guys can you help me and sorry for my bad english.

Regards

Simon

 

[trooper]

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.

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).

I really don’t know. Hope you guys can you help me and sorry for my bad english.

Regards

Simon


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simon,
im looking at the pics you posted, I don't see any frame for your plastic sheet, am I missing it some where ? I also don't see any air holes in your platen.
the problem is, if what im seeing is correct, there is no where for the air to be vacuumed from around the buck. also, the plastic needs to be in some kind of frame if you are not using one.

 

[simnic]

Hello,

sorry about that i add some pic to show you. I try with different platen one with hole 1/4 of an inch an now im trying one with 1/16 of an inch (second pic). On the first pic you see the one inch fitting under the platen and the third you see the frame who hold the plastic sheet. Now im using 0,075 of an inch and i try with 0,030 of an inch.

 

[Bandiet]

Hello,

sorry about that i add some pic to show you. I try with different platen one with hole 1/4 of an inch an now im trying one with 1/16 of an inch (second pic). On the first pic you see the one inch fitting under the platen and the third you see the frame who hold the plastic sheet. Now im using 0,075 of an inch and i try with 0,030 of an inch.


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Hi Simon... just a quick question, is there any form of seal between your platten and the frame, from the pics it seems as if the paper clamps you're using would leave a space between the two.

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[simnic]

Nope, i dont have a seal, i think about it. My frame is pretty tight with the platen. I just add silicone around the platen. But i dont put a seal.

I try to see on other project and i saw any seal. What kind of seal i should use?

 

[Bandiet]

I used a strip of foam called a seal strip... you get them in various widths and lengths, it's used to seal off windows and doors to prevent drafts. It's very similiar to two way tape, but obviously only has adhesive on one side.



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[Bandiet]

Some more picd of the foam I used...



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[flimzy]

another trick to getting even pull air flow on the bed is to have a sheet of aluminium or steer mesh. this kind give the best air flow. this also give continues pull all around the edge of your pattern.

 

[simnic]

Perfect I will go to the hardware store and buy some. I will do another test later.

Thank you for your advices, ill keep you update

 

[simnic]

Hello guys,

so i add a seal but not a steer mesh under the platen. Nothing change, i still have not enough vacuum. i dont what to think now. Im starting to think is that my gauge.

But i have a question, is it only the tnak who take off all the air or the pump have to finish the job after the tank?

 

[Bandiet]

Sorry bud... was hoping that would at the very least improve the pull.

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[Philly]

As a quick test disconnect the vacuum pump and attach a normal vacuum cleaner to see what happens. Or reduce the volume under the platen so the vacuum has less air to move.

 

[simnic]

I will try that

 

[simnic]

So i try, i have a small home vacuum. Its better but not perfect. The plastic still doesnt go all the way down on the object to mold.

maybe my plastic is to thick, i thing sure my vacuum is not enought powerful.

But i still try to figure out why the air tank is not enough powerful. Do you you know how much vacuum an air tank can handle? minus 30 or more?

 

[Philly]

I think it's more to do with moving more air as fast fast as possible. Those levers don't help with the speed of getting to full vacuum.

 

[simnic]

What i dont understand, the setup with the air tank working on much larger machine. So its maybe how the hose are plug or maybe my gauge cause without vacuum pressure you can it show minus 10

 

[TazMan2000]

Is the plastic hot enought? Try heating up the plastic in an oven. Mount the frame over some coffee mugs or something that can withstand the heat.
Are you certain there is a perfect seal around your base?

TazMan2000

 

[simnic]

I will add more silicone around the base.

But the clamp on the frame create space below the frame. The seal help but maybe it still have some air passing there

 

[jayroth]

the plastic was not heated enough. Even a weak vacuum could have made a better pull than what is in the picture, assuming properly heated plastic.

 

[Scratchy]

When I built my three vacuum plattens, I sealed the inside with a combination of polyurethane caulk and epoxy, and I also have foam weather stripping between the plattens and the frame where contact is made. I folded a piece of window screen and placed it between the form and the platten for better airflow, I run these with the aid of my shop vac, I have the hose connect directly center, and under the form. So far I formed one pull, it was a 1/8" (3mm) piece of ABS and I warmed this in my kitchen oven at 450-500 degrees.