SQT 200 MY milling prob

Hi all I hope someone can help. My problem is that the milling shaft on a SQT 200MY is not engaging and disengaging properly. Both prox swithes are working fine. It started off just being the disengage had a problem. I removed the middle cover on face of turret, removed prox swithes, still on monting bracket, cleaned them and flushed the drive unit with oil as best I could. Then replaced swithes and ran. Seemed to work for a bit, but back to same problem. The air supply is set properly and the shaft moves pretty easily back into place when I have had to help it retract after an alarm. Thanks for any info and guidance.

Is the turret out of alignment radially?

If the coupling binds on that bore in the turret when it tries to engage or disengage from a tool you'll have problems.

What's the alarm? Mill spindle sensor malf or something like that?

The turret is aligned, the milling drive shaft won't retract with out any tool in it. The alarm is 239 Milling Coupling Sensor Malfunction. I think that alarm is being generated because the shaft is not retracting far enough to hit the prox switch on top. After it alarms I can manually push the shaft back up and it will make the prox switch. It kinda seems like maybe the shaft is gunked up or something? I have flushed the unit from every spot I can find.

Well, my experience is limited but having replaced (or had someone replace I should say) here's what I know of SQT milling heads.

With regular use they need a rebuild / replace every couple years and they are labor intensive to remove. I replaced the mill head, drive shaft and rear bearings. I think parts were around $2500.

If you need another, Spindles Plus (Mike Moles) rebuilds them and, lucky for me, they had one on the shelf. I just sent my core when the job was done.

The alarm comes from exceeding a set time to trip one of the prox switches. Same deal for turret clamp and parts catcher extend/retract etc.

Have you tried removing the air supply from the machine and manually moving the drive coupler in and out by hand. Feel for binding or grit or anything that could keep it from retracting?

Thanks for the info. And yes i have tried moving by hand, I even snaked the cover off the top of mill drive unit(that was fun). I manually engaged the drive by pushing on the shaft with a rod. I was able to push it in but could feel the resistance from the spring, so I don't think the spring is bad. once i let go it would retract enough to disengage the live tool, but not near enough to make the prox switch. I removed the prox switch mount with the prox switches attached to it, then flushed the unit until clean. I tricked the prox switches to run the drive unit while flushing and removed quite a bit of crap. Then I ran the live tool without a holder and when it tried to retract and fell short I pushed it up while it turned. The shaft came back down some when I quit pushing on it??? Not sure where to go next. Thanks for your input.

Try Mazak tech support, those guys are pretty good. I generally get a call back within 30 minutes.

1-800-331-9151

The mill drive is extended under air pressure and retracted by spring pressure. It is still possible that it is gunked up at the end of the stroke, especially if the air used in the system had moisture and/or dirt. The spring can get corroded and weakened over time. You should also consider the solenoid air valve. It may not be closing all the way and still allowing some air pressure to hold the drive in the extended position. Also, if the air valve has a silencer on the exhaust, then that may have become dirty and when that happens, it becomes a flow restriction on the exhaust side which will restrict the drive from retracting.

Just an update. I got ambisious yesterday and pulled the milling head from our Mazak SQT200MY. It turns out the drive shaft was pretty gunked up, but after a good cleaning it is as good as new. Thanks for all your help.