VF4 Air requirement doubt.

I have this question on the air requirement for these VMCs ( VF1and VF4)

It says clearly on the specs sheet that it requires 4 cubic feet per min

how many tool changes per minute is considered while arriving at this figure.

For instance if I dont make any tool changes at all , the only air usage would be for the spindle lube....

Would somebody throw some light on this....( I chose a compressor based on the no of machines I have like 4mcs multiplied by 4 cfm = 16 cfm for 4 VMCs ,But I find that I have overestimated....the 4 machines comsume much less than 16 CFM...)

Thanks
MJM

I don't know what the tool change rate that Haas uses to rate the CFM requirement. I would guess that it is pretty modest. I think the air blast at tool change uses a pretty good amount of air.

Air consumption can be a moving target. A lot depends on how much blow off your operators do. I tend to run other air operated equipment at the same time. Things like air impact wrenches, air cylinders, Air/Oil boosters for hydraulic clamping, and Sugino air operated drill units. This all adds onto the air suck.

I would rather have a little too much air than not quite enough.

I don't know if that was any help but that is some of the things that need to be considered.

Personally I would go with a 5HP Screw to run that many machines.

ymmv

Thanks ARB

Its like this. ( you just opened the flood gate)

apart from these 4 Haas machines I have 3 other VMCs

When we added the last 2 haas machines 2 years back we had had a 10 hp compressor
( reciprocating) . WE found we didnt have enough air power so we went in for a 15 hp screw compressor.( with a delivery of 56 CFM)

the calculation I made then was based on the HAAS spec. Since I didnt have precise air requirement calculations I worked like this

7 VMCs = 7 x 4 CFM= 28 CFM
Cleaning guns every where + 4 impact wrenches + a few pneumatic deburring tools etc
for all of these I estimated 15 CFM ( call it a gut feel figure based on what our old compressor rated for 30 cfm was delivering)

I landed up with 42 cfm , I chose the next higher rated screw compressor because you dont keep buying screw compressors just like that.. what we bought needed to serve us for 5 years at least....

Now I have 56CFM ( 15 hp motor) . ( but the requirement is close to 30 cfm only)
The problem now is that I'm using more power .

We got the basic model without the VFD . to save power we need to cycle on and off.
but that results in some 15 starts and stops in an hour. Not recomended.
And now its running in load unload mode with the motor running continuously...
the motor current during the unloaded time is wasted electricity.

( I 'm now working on increasing the storage)....to go back to cycle on off mode...

And all because I based my calculation on the HAAS SPEC.

SO just How much does the machine alone need ( leave out the cleaning and all other pneumatic devices that every body uses..


Thanks ARB

For what it's worth, just to get me running I used a compressor rated at 4.5cfm (30 gallon tank) on my VF-2ss. That poor thing was running nearly constently. It shut off at 135psi and turned on at 100psi. It would run for roughly 15 minutes, shut off for about 2 minutes then start the cycle all over again. On some short programs with 3-4 tool changes, I would have to take a break periodically and let the compressor catch up. Also, if I just kept hitting ATC Forward, the machine would eventually alarm out due to low air pressure after about 15-18 changes.

Based on that, I'd take a wild guess that 5-6cfm would be more appropriate if doing lots of tool changes. That's only a guess though.

Thanks MAtt

'Also, if I just kept hitting ATC Forward, the machine would eventually alarm out due to low air pressure after about 15-18 changes.'

sure gives an idea...

You know what .. I intend doing precisely that to find out tomorrow ...( holiday)

Thanks again.

MJM

It's not just volume of air you can produce, but flow. I installed the air supply for our EC-400 a couple years ago. We have a good sized shop, 6 CNC's , tons of other equipment. 2 large air compressors outside feeding everything. Tons of air. When the tech came to complete the installation, he informed me that the pallet would not index because of insufficient air supply. I had to redo the air connection leaving out the quick release fittings I used at the final connection. They had a 1/4" ID and that would not flow enough air. Some machines consume a large volume of air momentarily, such as the EC-400 does when changing pallets.
I ended up using 1/2" copper plumbed straight to the machine.

Can you bump up the pressure in a storage tank and regulate the output as needed to stop the cycling.

the max pressure available is 7 bar. (@ 56 CFM)

In fact its another option ......the manufacturer says I could try changing the pulley kit and slow down the compressor .

Where by I will reduce the CFM to about 30 but will then have the option of going up to a higher pressure of 12 bar.

The Max I need is just 7 bar For the HAAS the other VMCs work at 6 bar .....

As for the piping we already have 1 inch mainlines and down to 1/2 inch for the branches.(Volume is not a problem).

Thanks for the inputs...
MJM