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View Full Version : Help! Vacuum forming 1/8" ABS



amdp
05-27-2015, 09:06 PM
Ok guys I have tried 5 times and failed all 5 times on forming 1/8" ABS. I made my own machine which holds a 24x24 inch piece of material. Heaters are above. The problem I am having is it won't suck down tight to my mold. My mold is 8.5" tall, 15"wide and 15" deep. I am using a small shop vac and compressor pump turned into a vacuum pump. I have attached a picture so you can see the end result. What can I be doing differently? Do I not have enough vacuum? Is the material too thick?

underthetire
05-27-2015, 09:26 PM
How much vacuum can you draw?

svenakela
05-27-2015, 09:37 PM
First of all, 8.5 " is pretty tall for such thick sheet of ABS. You need to heat it up a lot, I would say when the sheet is hanging down equally much as the plug is tall your getting close to wha't needed. I vacuum form details in that are about 2-3 inches high and l let thinner sheets than yours soften up until it drops about 4 inches.

BW56
05-28-2015, 01:11 AM
I don't think a shop vac will pull material that thick with any detail. I built a vacuum chuck for milling using an old paint pot as a reservoir/coolant separator and an ac vacuum pump from Harbor Freight. I can pull 20+ inches of vacuum if I need to. Depending on your vent hole locations I would think it could work for you. I use a 1/4 turn ball valve to apply vacuum, quick connect hoses, and a bleeder valve to adjust the vacuum and let the pump run continuously. Buy the extended warranty and build a better taller exhaust and filter to recover the oil it spits out. Ps i build molds for the electronic packaging industry and they do it like you are trying, just on a much smaller scale and they use an air box over and push air on the plastic with higher pressures. Its called carrier tape.

svenakela
05-28-2015, 04:52 AM
It will if the sheet is soft (hot) enough. Speed is needed to get the sheet down before it starts to harden again, flow is better than low vacuum.

Ironman84
05-28-2015, 09:12 AM
I'm not sure about the shop vac, I don't think that is a wise choice. One thing I haven't noticed others saying is with your set up, speed is definitely a factor. With that being said I would recommend heating your mold to a temperature that will help the ABS from cooling down once it comes in contact with it. I built vacuum molds for Bell jet ranger interior for 11 yrs. also try some .080 or close material thickness as a test piece. Hope that helps.

Ironman84
05-28-2015, 09:22 AM
After looking at the picture again your table is not big enough for that tall of a mold. Did you go 1 1/2 times the height. Also your frame needs to clear the table so you can pull down past it for a good seal. Get rid of shop vac. You can get a 15-20 gal tank and pull a vac on it and use it to support your compressor just don't have too many things going on at once.

BW56
05-28-2015, 10:53 AM
I'm not sure about the shop vac, I don't think that is a wise choice. One thing I haven't noticed others saying is with your set up, speed is definitely a factor. With that being said I would recommend heating your mold to a temperature that will help the ABS from cooling down once it comes in contact with it. I built vacuum molds for Bell jet ranger interior for 11 yrs. also try some .080 or close material thickness as a test piece. Hope that helps.

What he said. The people i work with fight the mold temperature of being to cool and stop freezing the plastic and not being cool enough to set the plastic. An air box over it all has an advantage of more pressure if needed over a vacuum.These guys do blow out aluminum air boxes once in a great while on higher cycled older air boxes.

svenakela
05-28-2015, 03:12 PM
I totally agree with the table size, it looks very small. And as mentioned the plastic sheet is very thick for such a setup.

But, vacuum forming with a shop vac is not a problem. There are many people doing vacuum forming with house hold vac's and they do pretty big molds. I actually av a large vacuum table for larger molds that I connect to my central vac in the workshop and forms 2' x 2' shapes without a problem. I think the main problem here is the thickness of the plastic and a pretty aggressive shape on the plug in combination.

Like Ironman84 says, try a thinner sheet.