Compressor aux air tank?

[arizonabuckeye]

I have a decently sized wood shop ~3500 sqft. - professional door maker - recently I have been having problems with my air compressor keeping up with our 5 axis cnc. The air supply goes through about 75 ft of 3/4" copper tubing before hitting the machine. The problem is this - after the compressor has been off for a period of time and I kick off the machine it pulls air and errors out the machine then the compressor kicks on. My guys are asking for a new compressor but I am thinking an auxiliary air tank close to the 5-axis would solve the problem. My thinking is that when the lines get low pressure there is not enough in the lines to supply the machine but boosting capacity close to the machine would provide enough buffer to keep the machine running and allow the compressor to catch up. We also talked about going to a 1" line to the 5-axis.

Any thoughts?

 

[Bretny]

Theres prob not alot of pressure loss in 75' 3/4in copper. Can you turn the in/out pressure up onthe compressor?

Aux tank may not help due to longer times at lower pressure. But if its the initial surge in air thats setting the error it may.

 

[MacMcMacmac]

If your compressor is keeping up with demand otherwise, this sounds like a perfect scenario for another tank for local storage. Make sure to include a safety valve in it. I'd probably put a check valve in the line before it as well. Might as well keep the air to yourself if you're far away from the source. This will also help to minimize the extra running the compressor would need to do to keep both tanks full all the time if your high demand is intermittent.

 

[bochnak]

Run full pressure in main line, then use a regulator right at CNC machine. That will boost CFM.

What is the CFM and PSI that this CNC requires?

 

[sberry]

How big is all this stuff and what demand? 3/4 is a lot of line with a small comp and relatively low demand.

 

[cvairwerks]

Is the cnc tripping due to low air or is it getting an electrical fault and tripping out?

 

[MattT]

recently I have been having problems with my air compressor keeping up with our 5 axis cnc.

So it was working OK and has started faulting on low pressure recently? If so then something has changed. Incorrect pressure switch settings, at the machine or compressor, and restricted filter elements would be the first things to check.

Regards the aux tank, start by checking pressure at the machine upstream of the filters. If you see pressure fluctuations there as the machine cycles then the tank should help.

 

[stonesfan68]

Storage must have a pressure band to be effective. What is the required pressure of the CNC? What is the on-line pressure of the compressor?

This is one way of calculating the required storage to deliver x flow rate at a given pressure for a certain length of time.

V = (T x C x Pa)/ (P1 - P2)

V, Receiver volume, ft3
T, Time, minutes
C, intermittent demand, ft3/min
Pa, absolute atmospheric pressure (14.7 PSIA for sea-level)
P1, initial receiver pressure
P2, final receiver pressure

Start with P1-P2 = 10 PSIG and go from there. The bigger the pressure difference the smaller the receiver needs to be. You’ll also need to install a pressure reducing valve at the discharge of the receiver (unless the CNC has one already) to keep the air receiver at a higher pressure than what the CNC requires.

 

[The Tool Tyrant]

I have a decently sized wood shop ~3500 sqft. - professional door maker - recently I have been having problems with my air compressor keeping up with our 5 axis cnc. The air supply goes through about 75 ft of 3/4" copper tubing before hitting the machine. The problem is this - after the compressor has been off for a period of time and I kick off the machine it pulls air and errors out the machine then the compressor kicks on. My guys are asking for a new compressor but I am thinking an auxiliary air tank close to the 5-axis would solve the problem. My thinking is that when the lines get low pressure there is not enough in the lines to supply the machine but boosting capacity close to the machine would provide enough buffer to keep the machine running and allow the compressor to catch up. We also talked about going to a 1" line to the 5-axis.

Any thoughts?

Our CNC's require 80 psi, and the pressure is regulated at the machine via a standard pressure regulator. I would have to assume if your's is similar and if so, then I would guess that your compressor cut-in pressure is set too low.
The 75' of 3/4Ø line should be more than sufficient, unless you have a large draw off the line before it hits your CNC.

 

[Lwel9226]

If your compressor is keeping up with demand otherwise, this sounds like a perfect scenario for another tank for local storage. Make sure to include a safety valve in it. I'd probably put a check valve in the line before it as well. Might as well keep the air to yourself if you're far away from the source. This will also help to minimize the extra running the compressor would need to do to keep both tanks full all the time if your high demand is intermittent.

This sounds like a good solution to me....
3/4 in. should be enough air but, if you decide to go to larger line to the second tank,
don't stop at 1in. go to 1 1/2 or 2in. The supply line will add extra volume....
And use check valve going into the extra tank as Mac suggested....

LynnW

 

[Lwel9226]

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