So way back when i bought a vacuum pump from a private seller on ebay.
I'd spent some time looking at pumps on ebay and they seemed to come in 2 types - dry vane and ones that involved oil somewhere. Dry vane seemed like less to worry about so I bid and won one of those.
I'd never vacuum veneered before but I had done some using clamping panels and cauls etc. it wasn't very successful as there were places that had little pressure.
Mt very first vacuum bag - an ordinary poly bag sealed with clear silicone
And an early version of the pump setup. Think i may have tested it using just the pump but soon decided it needed a vacuum reservoir to allow the pump to rest. Non return mole wrench valve
That first test out of the bag
It wasn't stuck that well. I'd used cascamite glue which was the same stuff I'd used for hand clamping so in my mind it was not the right stuff for this. I can remember cascamite from school woodwork days and it was really strong but this stuff isn't
On to building a better pump setup. I used a relay to switch the pump so i could trigger it with microswitches.
Microswitches. I saw something on youtube once where a syringe was used as a pneumatic cylinder. i connected the vacuum pipe to the place where the needle fits and a spring to the extended plunger. The vacuum in the syringe pulls the plunger in against the spring until the microswitch is triggered to turn the pump off. As pressure falls (air leaks in) the spring wins and the other switch turns the pump back on.
The clamp is on the pipe to the workpiece just for testing.
One thing that took some solving was a simple non return valve near the pump as the pump itself does not have one. The pump is a major leak if you turn it off. The thing in the air line above the spring was a non return + flow regulator device. It worked but was a huge resistance in the line as not made for vacuum pressures.
Top view in its first built version
Here is a recent version. The calor cylinder is sealed with araldite and a 6mm connector drilled into it. the pump now has a small plastic non return valve near it which is happy to work at vacuum pressures. i've also added a small vacuum gauge so i can see what the pressures are.
I did do another test using PVA
No problems this time.