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John really good link there. Also in setting up your zones using a quality manifold and setting up one to two inline reserve tanks that are emptied first before the part is "clamped" to the board will increase the initial clamping force for holding the part. Really good advice in the article I would strongly suggest folks read it. -Michael
Yes I plan to have a vacuum chamber and a number of 'zones'. I got one of the 8CFM pumps from ebay. If it doesn't work for the table I'll use it for vacuum bagging anyway.
I'll let you know how it goes in due course.
Hi,
Can anyone advise about hoses to connect the system together? I designed it expecting 5/8" ID hose. It concerns me though, that once a vacuum is being pulled the hoses could squash shut. Are there special types of hose I need to get? If not, I was thinking to use the engine breather / radiator hose for cars.
Actually I'm curious how any hose soft enough to bend easily can support a vacuum inside without squashing closed?
With a vacuum inside a circular hose you've got inwards pointing radial forces, so a circle is the strongest shape to use. Bending the hose is not the same, as you're applying the force in different directions.Quote:
Originally Posted by Tenson
Bear in mind that at best the difference in pressure from your vacuum approaches atmospheric presssure. This is much smaller than for example an air compressor where over 10 times atmospheric pressure is common.
Hmm.. also thinking about it the outside area of the hose will limit the pressure that can be exerted on it by atmosphere.
Alright, I'm off to buy some radiator hose!
Hi Tenson
If you are going to try this with your newly acquired e-bay pump i would just buy some nylon reinforced pipe the same diameter as your pump inlet, i have used mine with 10mm clear(home brew supplies) plastic and not had it flattening when i have been vacuum bagging. coupling to the vacuum bed would be better done with plastic plumbing waste.
regards
Mike
What is nylon re-enforced pipe? You mean the sort with ribs like a vacuum cleaner has?
My pump has 5/8" inlet and so does my bed. Feed to the bed is via steel tubes so I just need to connect those to the vacuum chamber and chamber to the pump. 1m length either side should do.
Something like this:- Clive
Attachment 10854
Hi Tenson
The reinforcement is actually more for strength with internal pressure, 5/8 bore should be OK as long as it's a straight'ish run, too sharp a bend and it might flatten but i would imagine you will have enough leakage to prevent that.
Regards
Mike
Well first trial just now using 5/8" radiator hose from Halfords (£2.99/m). Hose was 5m long 'cos i didn't cut it yet and it didn't flatten.
I connected the pump directly to one of the 4 steel tubes feeding the bed. This has 6 holes in it to the bed. The holes are 16mm each and I have not cut any channels in the bed to distribute the vacuum yet. I put a few bits of MDF on top and they got sucked down pretty strongly! I can slide them around but it takes a far bit of force to pull them directly up. I'm pleased for a first try.
Next I will make channels in the bed to give a much larger vacuum surface area and connect all 4 sections with a vacuum chamber.