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Haas Tool release button override to a user defined M code


Jul 13, 2015
Hello, don't ask me why, but I would like to connect additional wire from tool release button on spindle (Z axis) inside machine and not the one on keyboard to an optional M code relay like this:

If you understand, I'd like to use let's say M21 to behave exactly as if you press on the Tool release button inside machine (on spindle)...

I know there is M82 and M86 for Tool clamp and Tool unclamp function, but the problem is it waits for the operation to complete (signal that the machine really did unclamp/clamp the tool). So it does not behave exactly as if you pressed on tool release button.

Sometimes air valves or drawbar mechanism on this old machine sticks and won't open secondary valve so you have to press it a couple of times so it does (when machine is very cold and didn't work for longer period of time), but I don't want to mess with real problem and fix the machine, I just want to do "simple fix" by making a small program which will do what I manually do when it sticks (press on tool release button as many times as necessary so it unsticks).

Anyways, the question here is: how to connect this wire to a relay to do what I want?
You say old Haas but, I don't know how old that means. You probably have M-code relays on the IO board. Splice the wires from the switch area and run them to the relay you want to use and you're done. You may also have a connection from the spindle release button that runs back to the IO board. You could make the connection there.

It's probably easier and faster to fix the sticking piston.
I agree with above. Sounds like a. Make work project without solving the real issue.

It’s it’s easy to dismantle the pistons. Solenoids are cheap to replace (cheaper than you time fooling around!)
And a little grease goes a long was on a sticky taper(get something with a high resistance to washing. Be been using lathe chuck grease lately and it works great, 1 light smear a day into a tool holder chuck eze grease)
I/O cable 550 P23-1 is the remote tool unclamp. Parallel this connection with the M## relay to ground it. Relays have NO, NC and Arm connections.
Ok, I've tried fixing it, no luck. I tried putting small amount of air tool (compressor) oil to lines, both to machine and left and right of the tool release solenoid. No luck. Then I removed and totaly disassembled tool release solenoid valve and Schroder bellows right next to it, cleaning it and it still does what it does...
What else could it be?
Could it be somehow caused by tool release piston assembly and drawbar? Why does it stick like that, when you press tool release button (or a small plastic button on top of the tool release solenoid valve to actuate it) the tool release piston drops down on the first stage, just gets off the upper drawbar limit switch, but doesn't go down to the lower limit switch until it unsticks...

Heres the video:
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I have not had this problem but, I have watched these videos. It sounds like a combination of the valves and/or the tool release piston needing rebuilds.

Possible the piston is getting cocked in the bore. Is there much wear on the post that goes up through the spring?
Ok I think I've found where problem lies but I'm still not sure.

I've noticed that when you turn spindle orient on (M19) little pin (about 12mm in diameter) which signals the machine that spindle is in orient position (by using limit switch with small wheel on top of it which slides on that pin or out of it) releases air through O-ring around that pin...

I'm not sure if it's enough air loss to cause problems but that definitely doesn't happen on other similar machine.

I've also disassembled tool release piston, cleaned it, lubricated and reassembled. And I repeated that procedure 3 times. It didn't help at all.
I've also removed inlet air pipe to air precharge valve on the back of the spindle and poured small amount of compressor fine oil to that pipe, tightened it back and cycled tool release multiple times in order to try to see if something inside that valve was stuck and didn't work properly, but it also didn't help.

So only thing I'm thinking of doing now is to somehow disassemble this M19 pin with it's block and see if I could clean it and replace O-ring but it looks to me it's gonna be tough to do as there is very little space to remove it and I'm also not certain if it can be removed as I think now.

It looks to me it's held by 4 bolts on top of that block but I'm not sure if it's in one piece with rest of the mechanism (spindle encoder block and solenoid block)...

Any advice for this situation would be much appreciated.

Thanks in advance.
Actually I think I'm wrong although this might be a small problem, but I think it's not causing this because when you just press on Tool release button it doesn't orient spindle and this air loss through M19 block wouldn't be a problem.

The problem I think now, could be a precharge valve because comparing tool change with other machine where this is working properly, the precharge valve opens first and drops pin down a little (letting it off the upper tool clamp switch) and then main valve opens and drops tool release piston all the way down...

On this machine when it sticks, the precharge valve doesn't move the pin down immediately but with delay and while it struggles to open it makes a buzzing or humming sound, it moves the pin off the upper tool clamp switch a moment too late, so I think this precharge valve is the culprit.

Can it be fixed somehow?
Did you watch those videos I linked previously? He talks about this. They sell rebuild and replacement kits for those valves because of this exact problem.
Okay I've fixed it.

First off, I had to totally disassemble TRP mechanism, clean the cylinder and piston thoroughly, polish them (cylinder had smaller scratchmarks on couple of places at the top of travel), lubricate everything using small amount of compressor fine oil and reassemble.

Secondly, the precharge air pressure was too weak and when I tried to increase it first time I thought I hit the maximum setting but I was wrong, it just was much harder to rotate adjustment knob so I managed to increase air pressure for precharge to a good enough value so it finally worked properly. I'm not sure what was the buzzing sound, I think it was from precharge valve/solenoid but it also could be from TRP as it was unable to move properly, maybe it just vibrated on top of its travel and produced this sound... but anyways when I adjusted the valve correctly it immediately stopped buzzing and now works fine, as it should.

Only problem which left is with the M19 pin block which leaks air on the O-ring but it seems it doesn't affect tool changes which now go smoothly so I won't touch it at this moment.

Anyways, thanks for all your help guys!!
I'm glad you got it fixed this far. Again, referencing the CNC Repairman videos and website above: they have the shot-pin rebuild kit with new O-rings and snap ring for like $14. I'd order one and just get it over with while you're in there.