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Lazyman
3617 posts
and
28 followers
in over 2 years
in over 2 years
Venturi vs Pump Vacuum Systems
I picked up a pretty nice 2nd hand Gast vacuum pump on the relatively cheap a few years back through FBM, along with vacuum chucks and manifolds and gauges for my lathe. It works well as long as I get a good seal between the piece and vacuum chuck. I do not use it that often, but when I do, my biggest complaint is that the Gast pump is not exactly quiet. It is not really loud either but the droning can get a little annoying when using it for longer lengths of time. It is always a relief to turn it off after use and I might actually use it more often if not for the droning. I was wondering if a venturi vacuum generator with my 10 gal. CA Air compressor might be a little less annoying and still effective. Of course, the compressor may cycle on occasionally too but it is pretty quiet as compressors go. I am also thinking about using vacuum clamping fixtures for things such as my CNC machine, vacuum chambers and maybe even some vacuum press applications at some point which both can to be longer running than turning on the lathe.
I am looking for impressions, experience, pros and cons, etc. related to both vacuum generations methods. A couple of basic questions I have are how much air it actually takes from the compressor to maintain a maximum vacuum? Is my 10 gall vacuum so small that it may cycle on every few minutes or what? I recognize that how good your seal is and that different applications and fixtures will make a difference how often the compressor has to cycle on but I am just trying to get sort of a relative idea. Not sure that the CNC is really right for vacuum system like that. Many of those that I have seen actually use suction (shop vac or DC) rather than vacuum so may require more volume than other more localized vacuum based work holding. The difference I suppose is that that on vacuum based fixtures, once you establish the vacuum and you get a good seal, it does not take much extra to hold them. The suction based approach, to be more of a brute force work holding and the suction has to be high and constant because you often do not have a complete seal.
Any thoughts?
I am looking for impressions, experience, pros and cons, etc. related to both vacuum generations methods. A couple of basic questions I have are how much air it actually takes from the compressor to maintain a maximum vacuum? Is my 10 gall vacuum so small that it may cycle on every few minutes or what? I recognize that how good your seal is and that different applications and fixtures will make a difference how often the compressor has to cycle on but I am just trying to get sort of a relative idea. Not sure that the CNC is really right for vacuum system like that. Many of those that I have seen actually use suction (shop vac or DC) rather than vacuum so may require more volume than other more localized vacuum based work holding. The difference I suppose is that that on vacuum based fixtures, once you establish the vacuum and you get a good seal, it does not take much extra to hold them. The suction based approach, to be more of a brute force work holding and the suction has to be high and constant because you often do not have a complete seal.
Any thoughts?
--Nathan, TX. Hire the lazy man. He may not do as much work but that's because he will find a better way.
6 Replies
I have a venturi system I use for both veneering and vacuum pot work.
The venturi is nice for less noise as you point out, It only runs when there is a demand.
Of course the airflow makes noise just like using your air hose to blow stuff off (full flow)
These are rated in CFM requirement and you can find a variety where one should match up with your compressors capability. You should have an accumulator on the vacuum side (I use two 10" sections of 3" pvc arranged like SCUBA tanks). I probably would not use a venturi if there is significant leakage expected just because I have the sound of my compressor kicking off every so often.
Advantage over a pump is they can be very fast.
The venturi is nice for less noise as you point out, It only runs when there is a demand.
Of course the airflow makes noise just like using your air hose to blow stuff off (full flow)
These are rated in CFM requirement and you can find a variety where one should match up with your compressors capability. You should have an accumulator on the vacuum side (I use two 10" sections of 3" pvc arranged like SCUBA tanks). I probably would not use a venturi if there is significant leakage expected just because I have the sound of my compressor kicking off every so often.
Advantage over a pump is they can be very fast.
Splint, is yours a specific brand/package or did you sort of assemble it from parts yourself? When you say that it only runs on demand, are you saying it has a sensor or valve that only runs the venturi when the pressure drops below a threshold?
--Nathan, TX. Hire the lazy man. He may not do as much work but that's because he will find a better way.
Yeah. a pressure (vacuum) switch that can be adjusted for the trip point. Also has hysteresis built in.
I just used a kit from veneersupplies, but you can buy complete systems or just parts.
I just used a kit from veneersupplies, but you can buy complete systems or just parts.
I’ve got a Venturi that I use on my lathe, as well a one I built form a kit to do work holding. In truth, I don’t use the one for work holding but rarely. But it works well. The one I use on the lathe works just great. I’ve got no practical experience with proper vacuum pumps in the shop to speak of.
Ryan/// ~sigh~ I blew up another bowl. Moke told me "I made the inside bigger than the outside".
Oilless vacuum pumps are the noisiest. 2 stage HVAC vacuum pumps are fairly quiet and will provide the deepest vacuum.
I used them at work a lot. We also hooked up a micron gauge for that last inch of Mercury. 15 micron was the target.
If I was out to buy one, I wouldn't be afraid of what Harbor Fright has.
I used them at work a lot. We also hooked up a micron gauge for that last inch of Mercury. 15 micron was the target.
If I was out to buy one, I wouldn't be afraid of what Harbor Fright has.
I want to do right, but not right now. Gillian Welch
Good info, Harry. Thanks.
--Nathan, TX. Hire the lazy man. He may not do as much work but that's because he will find a better way.
