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Subject: Re: What vacuum pump would you recommend?


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Message Thread:

What vacuum pump would you recommend?

Paul Downs  Member


We've got a Thermwood CS45 with 5x10 bed. It came with a Busch 15HP pump rated at 330CFM and 29" Hg. Both machines have been in service since 2005, and get regular maintenance (we run them 5-8 hours a day.) My guys tell me that the vacuum pump has started intermittently shutting down - this seems to be related to temperature in the shop. We have fans blowing on it all the time while it runs. They also tell me that it has always had problems holding down some sheets.

I'm thinking of replacing this pump. Spent some time looking at alternatives this morning and came away confused. My questions:

1. Is this pump big enough? If not, what size would you recommend?

2. Is 13 years its expected life? We've been faithful about oil and filter changes.

3. If I replace it, what type of pump would you recommend? Screw? Or possibly a rotary claw? I'm not clear which would be more reliable and/or energy efficient.

4. Favorite manufacturer?

Thanks for your help!

9/24/18       #2: What vacuum pump would you recommen ...
Robb Parker  Member


Paul, We run Busch vacuum pumps for our Homag CNC. It is approximately the same age as yours is. However, ours has 2- R5 series pumps that are 12 hp a piece. We don't have problems with hold down but I can't imagine having less vacuum, especially small parts.

I was told that Busch is one of the best out there. They are rotary vein, we have never replaced the veins but am told they are a wear item. We are very good about oil and filters also. Only issue we had is with a motor that puked. Kept kicking circuit breaker. Found a motor shop that rebuilt motor for about $350.00 I recall. Cheap fix.

They do run HOT. Great in winter, not so much in summer.

9/24/18       #3: What vacuum pump would you recommen ...

With vacuum you have to understand at what level of vacuum you have at 330 cfm. You need to see the curve.

I recently changed from 2 10 hp Becker Dry vane to a 25 hp Kaeser screw. There is no comparison. The screw goes to a deeper vacuum and holds it much longer.

Right now there are some 25-40 hp liquid ring pumps on the market. If I was looking now I’d get one of these. A dealer I know had a good deal on the kaeser with low hours which is why I went that way.

Good luck

Used pump

9/26/18       #4: What vacuum pump would you recommen ...

Paul, those are good pumps. Check your Vanes, there easy to check and easy to replace if needed, you only need to measure them and make sure there in tolerance. Next check to make sure the vaccuum releif valve is set correctly, there are a couple great youtube vids on it, also easy to do. We were fighting ours a little and reset the releif valve and its running like a champ again. Checked our vains and they have hardly any where after running 30 hrs a week for 11 yrs. The price of the veins will knock you over though if you have to have them.

9/29/18       #5: What vacuum pump would you recommen ...

I have no idea what the best pump is. I've had 3 on 3 different machines. A 10hp Becker on a 4x8 grid table. Was OK most of the time but using gaskets is a PIA. Next was a Siemens Elmo water cooled, nothing but problems on a P2P. Current one Quincy 40hp screw. 1999 model still works fine but separators and oil are expensive when they need changing.
I'm not sure you can hold very small parts on a spoil board with any pump. We onion skin parts less than a certain size. The software does this automatically. If you have a lot of very small parts to run it is worth it to make a dedicated gasketed fixture.

9/30/18       #6: What vacuum pump would you recommen ...


If your pump is cutting out, you have a problem somewhere for sure as that shouldn't happen. If the pump you have is running properly you have tons of vacuum.

Everyone thinks you need 12 pumps all lined up and they all need to be 40 hp each. But this is not the case at all, 1 or 2 pumps is tons of vacuum.
I am not familiar with your cnc, but you said you have a 5x10 table, how often do you cut 5x10 sheets? maybe you cut bigger sheets all the time , but a lot of people cut only 4x8 sheets on a 5x10 machine, you have 50 sq ft of table but you only need 32 sq ft of vacuum. Shut down the extra 18 ft that you don't need. Like I said I don't know your machine, but many tables have zones you can turn on and off, some machines have plugs you can use to isolate areas, or you can be creative and tape poly on your spoil board or use a piece of laminate or plastic sign material to cover the area where you don't need vacuum.

Another big problem for a lot of people is the condition of the spoil board, number one is it machined regularly, if it has a bunch of tracks in it, and if your operator is cutting to deep then the tracks are just wasting vacuum. Is your spoil board clean, what do you do to prep it in between sheets? There are not many sweeps or dust collection systems that clean the board sufficiently to just through a new sheet down and cut again. I recommend a quick vacuum, I use a metal wand with a brush that has wheels in it. I have a port that ties into the dust collector, it is very quick.

If you have to cut a bunch of tiny parts then like others said, onion skin , or isolate one small corner of your table and cut those parts separately.

9/30/18       #7: What vacuum pump would you recommen ...


Sorry I forgot to mention, the pumps I like are the ones made by Becker.

10/1/18       #8: What vacuum pump would you recommen ...
Puzzleman Member

Hello Paul.

I have had problems as you describe of the vacuum just shutting down in the middle of a run. It only happens during the summer months. We too tried blowing air on the pump to keep it from overheating. I tried so many things like checking the wiring looking for shorts or hot spots where the wiring would potentially overheat.

Got so frustrated with the situation, I actually called an electrician in. Found out that the problem was the starter switch. Replaced it with a heavy duty model and everything has worked just like it should. No more spontaneous shutdowns. Worked all summer as it should.

10/1/18       #9: What vacuum pump would you recommen ...
Dropout Member

We had the same starter issue.

Now using a 30 HPSullair rotary screw that I bought at auction for $1400.00. Has run for 5 years with only normal maintenance.

10/1/18       #10: What vacuum pump would you recommen ...

My experience is it's easy to add more pump power but that's not the only way to increase holding power.

We had a new custom 5X8 CNC made in china and had 20, yes 20 independendent vacuum zone actuated by M codes. We went from 2 10HP Becker pumps to one.

Cutting strategy is more important that shear vacuum.

You need a combination of Nesting - Cutting Strategy and coding to make your vacuum needs drop.

1.Nest your parts so the largest parts are cut last.
2. If they are too small to be cut in one pass then onion skin the last couple of parts.
3. Use a cutting strategy that uses all the remaining uncut board to hold your current part.

4. Turn off the zones under the parts already cut. The leaks made by the part already cut is what causes the need for such huge amounts of vacuum.

In afterthought 20 zones appeared to be overkill. The added $ was minimal even after replacing all 20 valves that were way undersized from the manufacturer.

We are adding a soft start to the one pump we are running to decrease wear and cost of electricity. We will turn the pump off unless we are cutting.

10/1/18       #11: What vacuum pump would you recommen ...

Bob that sounds like the hard way with software as well as hardware issues to deal with over time.

Most standard software would not control that. Most nested machines have 4 zones. I believe the electricity saved would be eaten up by the increase in the cost of the machine, the added programming and maintaining all those zone valves.

We have one pump, it works, nothing moves. We onion skin small parts.

10/1/18       #12: What vacuum pump would you recommen ...

Yes, I was really just stating that most of the Vac power goes to leaks caused by kerf. (CFM)

More manufacturers should put in automatic zones. 8 to 10 would probably be fine. I only know of one that is doing it now , Felder on their upper level machines. Hopefully more will do so in the future.

I have written our CAM system and it only took me about 3 hours to incorporate the zoning into our post so I assume most software companies could add that to their posts fairly easy.

Just lean thinking. I hate waste!

An extra 15 to 40HP running all day, as most do, is a lot of waste to me. Most just close of the Valve between sheets so the relief valve is activated. This is the hardest you can work a pump. Lots of wear, lots of heat.

I was testing to see if I wanted to get in the business of putting together an integrated Hardware Software System for flat panel. This was our test system. It has worked out quite well other than the learning curve of working with the Chinese and OSAI.
I am not sure I have the time to pursue this additional venture. If I dont, I hope the existing manufacturers pick up on it and go with it.

FYI: We are cutting closet parts. We are cutting 1 1/4" X 12" toe kicks without onion skinning. One pass :-) Cutting strategy is sometimes more powerful than vacuum.

10/1/18       #13: What vacuum pump would you recommen ...

As I mentioned earlier we use a Kaeser screw. If your system doesn’t leak it turns itself off after a short period when not in use.

10/2/18       #15: What vacuum pump would you recommen ...

its only software
we use one pump copy becker 250(5kw)
almost no any part move
cut 85% of the board in one pass with 6mm diameter tool (15m /min)
only last 15% onion skin
any size ,even 30mm*300mm parts
no move
you must always cut parts order from corner inside ,always from the inner side ,near the corner,
the point its ,part should always connect to main board all the cut until the end of the cut
our software do it automatic
after the nesting

10/15/18       #16: What vacuum pump would you recommen ...
Salce Smith  Member


Hello, i think 2 sets of 7.5kw Becker vacuum pump is enough for mainly jobs.


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