Not really on the bench but on the floor... My heater unit for the female tooled vacuum former is finally producing the heat I need. I have had the chamber and pump working for a while now but always struggled with the heat.
There are 3 parts to vacuum forming and if any one part fails, the whole thing fails.
Those 3 parts are -
1. heat. I can now get well over 200 degrees C. So whilst 110 degrees C works for ABS, I need 150 degrees C for polycarb and 180 degrees C for perspex.
2. seal. I have spend some serious coin on this system and seals were about $150. I ended up buying sheets of a high temperature rubber and cutting them out myself. They could have made them for me at twice the price. I have recently spend over $500 on frames and this heating box.
3. suction. Most people use shop vacuum cleaners for suction. I have a 9cfm vacuum pump and 30 litre chamber that I can connect to my large chamber to act as a surge tank. Because my goal is to be able to pull thick plastic, I needed way more than the -6"Hg of a typical vacuum cleaner. I have managed to get a full -30"Hg on a smaller test rig where I was able to form 5mm thick perspex. I have also been able to pull 6mm polycarb.
Basically, this heater is a rework of @x-robots patio heater design, but using a 3 ring gas burner and a fan. Both the burner and the fan are 250mm Dia. The burner has adjustable air intakes and ball valves but I did not want to be reaching inside the hot box to make an adjustment, so I went to a local gas fitter and had him make up an elbow and ball valve extension that sits flush with the outside. I can now turn the heat down via the single ball valve.
The rig is 800mm (internal) box made from16mm MDF with a 0.6mm aluminium flume going from 250mm to about 750mm at about 700mm high.
The burner sits on the base centred below the flume. Previously I was struggling to get 150 degrees C. My engineer friend suggested fan forced air to created higher temps. So I added a fan I had made a few years ago for another project and got amazingly hot temps.
I have run 2 tests this morning and very impressed with the results. Heating time is a quite a bit faster than electric heaters and is hot all the way to the edge of the frame. My electric fan forced heater could only really do 250mm surface. This should do the full 800mm.
So I am just waiting now for a frame to come back from being welded up. Then I should be able to heat up some plastic.
Yes I am doing this outside.
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