Air compressor pressure

[Marc Nicoloudis]

Good Day Everyone!


Was hoping for some advice regarding my air compressor.


I am working on a cnc router that requires roughly 100psi to operate a pnuematic valve that opens and closes a chuck. All is well holding the 100 psi for the first operation, however when it goes to perform the next operation, the pressure has dropped to 50 psi, and does not have time to recover fast enough to perform the second operation, which happens roughly 2 seconds later.


Can anyone pont me in the right direction as to how to achieve a more linear psi range during tool changes?


Would plumbing in a large aux tank help out or is this strictly a HP issue? THanks,
Marc

[Mike Heidrick]

Describe your compressor for us. Tank size, cfm, type of pump, etc.

Also are you only doing two cylcles?

Adding larger tank will only give you more air before the compressor starts and then it will take longer to compress more air to the regulated pressure.

[Rich Engelhardt]

The pneumatic valve (or the CNC router it's attached to if it's a whole unit) should have specific air requirements as far a how much air is required (listed in SCFM or CFM).

And +1 to what Mike posted.

[daryl moses]

Sounds like you need a larger compressor and tank...........

[Al Launier]

What are the specifics of your compressor and have you checked for leaks in the compressor?

[Anthony Whitesell]

Where are you measuring the air pressure? At the tool or at the tank? Definitely need details on the compressor and on the plumbing from the tank to the machine.

What is the time between these two operations?

Depending on the responses, one solution may be a small tank near the CNC machine, or a large 1 to 1 1/2" diameter supply pipe between the source and load, and possibly increasing the on/off settings of the compressor to recharge sooner. Send us some info and we can help some more.

[Jerome Stanek]

You could put a reserve storage tank just before the CNC that would hold enough air to allow your compressor to catch up

[Marc Nicoloudis]

6.3 gal tank at 40psi rated at 3.80cfm, at 90pst rated at 2.35 cfm

[Marc Nicoloudis]

The pneumatic actuator(Tool CHanger) is calling for 80-100 psi.
I had originally purchased this small compressor because it was going to be dedicated to the machine, and ran super quiet. It operates the tool changer fine the first time, but I did not anticipate the second cycle.

[Marc Nicoloudis]

Pressure is being monitored about 1 foot away from the tool, about as close as it can be, and I can watch it build and hold to 110, then it drops off the tool, and the pressure drops to 50, taking about 3-4 seconds to rise back up to 110. In the meantime, the router is programmed to almost immediately go pick up another tool, but the compressor does not have quite enough time in between.

Just 2 cycles, as the compressor has plenty of time to catch up while the router is cutting, before needing to pick up a different tool.

A sure fire way to fix this problem is with a nice($$) screw compressor, but was hoping this could be achieved another way, seeing as how it needs the boost of pressure for such a small amount of time. If an aux tank were an option, how could I calculate the volume of air needed to withstand a 60 psi drop like that?

Also, just for the heck of it, I hooked it up to my 6hp 30 gallon compressor, and it did the same thing.

[Marc Nicoloudis]

Thank you for all of the replies, much appreciated!

[Anthony Whitesell]

Where is the pressure gauge you are reading?

At what pressure does the compressor turn off at? At what pressure does it turn on?

I assume that since you mentioned "dedicated to the machine". The compressor is right under the table so the hose is short. Is that correct?

Is there a rating for the air consumption on the tool changer (SCFM)?

[Garth Almgren]

Is there a way for you to add more delay into the CNC programming between the tool changes? Just have the program pause for the 3-4 seconds it takes to recover the air pressure?

[Sean Tracey]

30 gallons is quite a bit. The cnc manual should tell you air requirements in flow rate, pressure and volume. If the valve you refer to is actually a pneumatic cylinder, you might be able to find the air volume required per cycle.

Also, you describe a valve that operates a chuck. I have seen cnc tool changers and there is a tool holder that contains the tool with a knob on top of it that a pneumatically operated draw bar grabs. The old tool holder is taken to a dock and released by operating the pneumatic cylinder that pulls or pushes on the draw bar depending on whether the tool is being ejected or picked up and grabbed. I wonder if this is what you are talking about or something else.

It may be that the hose or tubing you are using to connect from the compressor to the CNC and the fittings are restricting the air flow to the tool changer. In other words, the air can't get from the tank to the cnc fast enough because the flow is choked. Your description seems to indicate this as a posibility. Most portable compressors would be set up with 1/4" quick disconnects for hand tools like nailers, so you would probably have them on both ends of the hose which is very restrictive.

It would help if you determined how long it takes the compressor to recover. If it recovers quickly, then it may mean little air was used, but the restriction made the pressure drop since the rate the air is used was rapid.

A sufficiently large hose and piping to the machine is required and quick disconnects can reduce flow by a large amount. Just eliminating the quick disconnects if they are installed may do the trick. Also, hose length can really kill air flow.

Also, the regulators on portable compressors are usually really small, really cheap regulators. The regulator on the compressor may be too small to allow sufficient flow rate to the cnc. So you would need a system with a sufficiently sized regulator.

[Tom Deutsch]

Sounds like that machine take a BIG gulp of air for each "hit." I'm no pneumismatist (ha ha) but my first suspicion would be air volume delivery. Make sure you have, what, at least a 3/4 inch diameter opening from the tank, through the regulator/filters, through the hose and all fittings (no choke points). Just a stab.