vacuum press

[peter mikk]

for anybody interested, i have just finished making a vacuum press, very simple, just used an old compressor head+motor and thick clear pvc doubled over and clamped between boards for the bag. $cost$$ 50.00 ( alreday had pump+motor) had ample vacuum to pull down large curved veneer job. I was quoted around $1000 for an entry level unit.

[Eastie]

This is something I've been considering doing for a while. I too found the price of off-the-shelf units a bit steep. I might see if I can kill two birds with one stone and buy a new blue tongue compressor for 4wd and knock up a bag system for it ?

[journeyman Mick]

Sounds great, a couple of questions:
1) did you just hook up to the intake side of the compressor? Or did you reverse the rotation.
2) how did you connect your pipe/hose to the bag?
3) Do you need to keep the unit running to sustain the vacuum?
4) Did you use anything (ie: shade cloth) behind the work to make sure no air pockets formed? I've seen mention of special material in commercial bag units to ensure even evacuation of air.
5) Any chance of some pictures of your setup in action?

Mick

[AlexS]

Peter & others,

Vacuum bags made like this are amazingly difficult to puncture. An easier way to seal the edges is by using yellow-tac that comes in a strip specifically for this purpose. The pressure pulls it together, but when you've finished, a quick rip separates the edges. You can use it over & over.

You can by vacuum mats made of ridged rubber. I've also heard of string being used, but haven't tried it.

Incidentally, assuming you're gettingabout 70% vacuum, this is equivalent to about 7 tonnes per square metre. Hardly surprising it's effective.:D

[John Saxton]

Peter can you post a pic?

[peter mikk]

i will try to organise a picture, i haven't got a digital camera, but as soon as i have i will post a pic.
i will also sketch a pic on how i clamped the plastic down to form a bag. if you look at a cross section starting from top you see a section of timber (70x35) the pvc sheet then black self adhesive foam strip this is clamped to the bottom pvc sheet that is over another timber beam. a copper pipe is put through this join with foam under, and a bit of a carve out for the pipe. this set up is on three sides, with the forth side being the plastic folded over.
i used a vacuum hose from a car brake booster to connect the pipe to the compressor.

i am about to try to make it cut in and out on an auto vacuum switch, and try and experiment with the right amout of pressure, rather than leaving it on during drying. ( was slow revs). I will also try to use a car a/c compressor as this has a 12v clutch that should be easy to set up to cut in and out.

[MikeThePom]

Peter,
Did you ever get the auto vacuum switch idea to work ? I realise the post was some time ago but I have just 'obtained ' a vacuum pump that moves 4CFM and down to 150mBar (or so I was told) and am looking to build a vacuum press system so any ideas / tips so that I don't have to reinvent the wheel would be great.

Regards

Mike

[joez]

Hi Mike,

When I was researching vacuum presses with the guys at cloudmaker, I asked them if their vacuum pumps switch off and I was told that thier pumps dont turn off. Their reasoning was that its all the starting and stopping that stresses and eventually wears out the pump etc...

You should trying finding out more about the pump, you might find you'll be better off running it continously.


Joe

[AlexS]

The pump I've used ran continuously with no problems - often left running overnight.
One advantage with this system is that if you can't hear the pump, you know something's wrong.

[graemet]

Carbatec have an ad in this months AWW for a manual vacuum press using the vacuum pump from a vacuvin wine bottle resealer to get the suction. They even use the vacuvin rubber stopper to connect it! At $129 you could probably hook it up to an electric pump quite reasonably. Cheers Graeme