[theLoneStar]

Just cant get the material to pull down tight. Not sure what to do, allready on second sheet of ABS and no real improvment.

I think I have plenty of heat, watch the temp with infrared thermal thermometer, to adout 350 degrees ferinhieght.

I just finished building a 24'' x 42'' machine. playing on 1/8 ABS the specs of the machine are:
11pcs straight tube elements 600 watts set in 5 zones
holes in base plate 1/4 and 3'' grid also v groved grid lines
1'' x 24 x 42 vacuum chamber
second platten brought up level to material ( with grid & 1/4 holes )
1500 watt 240 vacuum , and 12 gal 5.5 Shop vac,
Neopreem gaskets under material frame and in it.

I also tried a vacuum pump and tank system and results where worse.

[joeavaerage]

Hi,
even with a perfect vacuum the max pressure you can exert is 14.7psi. A single stage shop vac might get to about 3/4 an atmoshpere, say 11psi in the time you have while the material is still
flexible. Maybe that is just not enough force to deform the material into the shape you want.

The problem with using a tank, and in this application is more correctly called a ballast, is that if you turn the pump on it will take a long time to pump down, by which time the
material has cooled and will not deform. If however you have the ballast pumped down to ultimate vacuum prior and then suddenly applied it to the workpiece....that might work.

Craig

[routalot]

I've only made tooling for vacuum forming and not handled the process myself but the successful operations did benefit from much bigger tanks than you are showing.At one business the tank was 20 feet long and 8 feet diameter and lived outside.It was kept evacuated all the time.The other business had twin tanks that were primarily for the autoclave and they were of similar size,which meant that evacuating the required zone was practically instant.In both cases the operators used their experience to decide the number and location of the holes through the tool and I never heard of a failure to form.An alternative might be the sort of pump that CNC routers use,where the flow rate is enormous and there wouldn't be the delay of a much smaller pump with a high vacuum capacity but no time to get there before the material stiffens.How do you measure the temperature of the material being formed?