CNC Vacuum table

[evilvet]

Gents,

JSR/ D_Hall & co had a thread going a while ago on vacuum pumps; I read that one and a few others. I need some advice form those more technically minded than I.

I have a job offer that requires CNC machining of multiple small parts that can only be realistically held via a vacuum table setup. I have the table itself under control. The issue is to source/build a vacuum pump that won't consume the entire profit of the job.

1.
Must pull 5-6cfm to give a solid hold down
2.
QUIET - There is enough noise in here already with the spindle, coolant pumps etc.
3.
Cheap. Enough said.

Can someone offer me a solution like:
Convert an old bar fridge compressor
A tyre inflator hacked
A vac pump from an EM that is being scrapped

Appreciate any thoughts.

Thanks

[Zeus]

A fridge compressor is ideal, not great volume, but I've pulled 30mmHg is seconds on a 500mL container. Quiet as too, and if there's not enough volume, put them in parallel.

[jackssmirkingrevenge]

How cheap is water down under

http://www.mrs-scientific.com/item/Bran ... 432_1.html

[Zeus]

Not with our water restrictions mate, also, PM incoming Jack, got an off topic question for you.

[evilvet]

Care to elaborate on the fridge idea ??

[Zeus]

Yeah, just solder on a connector on the vacuum side of several compressors, join them up with hoses and tees. You'll get a pretty strong vacuum at full draw (I measured 26" of Hg with one leaky compressor), and reasonable volume. Even consider a vacuum accumulator so you can get it to seal quickly.

Just make sure to oil the compressors, mine's been going for a year on 20w50 engine oil, so they're tough.

[jackssmirkingrevenge]

Agreed with the above, fridgies are quiet and as long as you keep volumes to a minimum one should be able to keep up with your needs.

[Brian the brain]

If you have a large tank ( or cannon?)
laying around..you could do with just one fridgy.

Have it pump out all the air and close it off with a ballvalve.
Then hook the vacumised tank to your table and open the valve.

Should work...

[Technician1002]

Fridge compressors are low volume pumps (low BTU heat volume). For high volume, use a higher BTU rated pump, like from a window AC unit.

[matti]

How about air ejectors, "pneumatic vacuum generators", we use one small that was cheap (5 euros) and its used for holding small pieces in welding fixtures.. Needs only air from compressor, but its not silent if you don't use silencer with it.
Here is example of ejector: http://www.directindustry.com/prod/air- ... 81279.html

[evilvet]

Hi

Are these venturi style vacuum grips, i.e. they rely on the constant flow of compressed air in the horizontal plane to generate a vacuum, or more precisely an area of low pressure, in the vertical chamber ?

If so, they won't meet my needs as I don't have a large enough continuous supply of HPA.

Thanks anyway.

It looks like I will finish up buying one of these
here

I don't suppose an electric brake booster pump from a heavy ute / small truck would do the trick ??

[jackssmirkingrevenge]

Here's a thought:



Some things I ripped off a machine at work before it was scrapped.

The compressor might be useful, I'll see if I can give it a whirl this evening and if it suits you needs I'll just ask you to cover shipping costs from epoxyland.

[evilvet]

Thanks Jack.
I was chasing up a lab rat mate who was upgrading his HPLC, it had a nice little vacuum on it but no result as yet.

Does epoxyland run on 240v or 115v ?

Ta

[jackssmirkingrevenge]

I was chasing up a lab rat mate who was upgrading his HPLC, it had a nice little vacuum on it but no result as yet.

Do you mean as part of the degassing system? In my experience these pumps tend to be quite feeble, I don't think it would be up to the task you expect of it.

Does epoxyland run on 240v or 115v ?

Same as Australia

[jackssmirkingrevenge]

No go I'm afraid, it doesn't seem to have a specific inlet port :-/ good as a compressor but not as a vacuum pump.