Turret probles with a mazak QT-250

We have a QT-250 that periodically strips the gear from the servo motor that indexes the turret. The gear is milled into the shaft and turns a pricey 3 piece curvic
that has the other part of the gear train cut into it.
Needless to say, the pieces from gear A travel around gear B and makes a 5000 dollar repair job.
This has happened > 4 times in the years I've worked where I work.
Anyone have similar issues with Quick Turns? Resolution?
Wes
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On Thu, 12 Feb 2009 17:36:03 -0500, snipped-for-privacy@lycos.com wrote:

I have rebuilt 3-4 250's with and without live tooling in the last 8 months.
Sounds like this one has no live tooling and has a hydraulic motor for indexing?
All of the live tooling machines have a belt drive to the shaft that indexes the tooling
No matter it has to be mis-aligned or starts before the turret is unclamped.
If you need any help you can always call me@714-334-4261 I work on Mazaks a few days every week.
Dave B
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No provision for live tooling. This is an electric servo motor.

That sounds like our multiplexes.

Whenever I set these up, I make sure the MRJ2 indexer doesn't show any significant change in motor angle when we clamp.

Thanks for the kind offer.
Wes

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On Thu, 12 Feb 2009 17:58:54 -0500, snipped-for-privacy@lycos.com wrote:

I have noticed diffrences between the machines out of Japan vesus Florence. When I go there on Saturday I will take a look and see if anything obvious comes to mind.
Dave B
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I've been to Florence once for training. I saw some big mills with Eagle Picher on them machining base castings. I didn't work at the machining side of EP but I once worked for EP for a couple decades. I got a smile seeing that American Iron was helping to make Mazaks.
Wes
PS sorry about misspelling problems in header. Damn spell check doesn't check that ;(
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On Thu, 12 Feb 2009 18:21:45 -0500, snipped-for-privacy@lycos.com wrote:

Sheesh! and I am worse.........lol. I am going to my customer who has about 12 Mazak's not to Florence.
I want to see if the 250's with hydraulic index motoer are out of Japan.
DB
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snipped-for-privacy@lycos.com wrote:

I don't know the 250 specifically; but I have a couple QT's that routinely eat up a lot of my repair time. It sounds like the index motor is starting before the turret is fully unclamped. The couplings are still holding the turret while the gears are trying in vain to rotate it. Or maybe it's trying to clamp before the motor is finished positioning. Either of those should give some visible or audible clues if you watch the machine carefully.
Unclamp confirmation before indexing is just a prox switch, which may be out of adjustment, or may even be caked with chips and crud, and giving intermittent too-early indication that it's safe to index. Clean and adjust the prox in that case, or maybe replace it. If the clamping starts too early, before the motor's done its job, that might be an "in position width" setting on the servo that's not fussy enough. Check the details and parameters of that particular drive. Wear and backlash can make it necessary to have the servo wait a bit after cycling, before it tells the PLC that it's happy with where it's at, and allows clamping to start.
Mazak uses big bushings on most of its machines, rather than bearings, to support the turret shaft when its unclamped. If these get worn, there might just be too much resistance to rotation, which can also kill the gears. Unclamp the turret (or catch the machine just right in mid-index with the E-stop button), and see if you can rotate the turret easily by hand. If not, then maybe the gears can't turn it either. Be sure you know how to recover from an interrupted index before trying this, or you'll hate me in the morning.
KG
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This machine was here before I was. Another tech called Mazak and they said our parameters in the MRJ2 controller were not correct as in full speed a head, full torque, ect.
The machine was purchased in 97 or so and I wasn't there. Looking at files where other techs saved the parameters to disk doesn't come up with a parameter set that is marketly different than what we have.
It may turn out that at some point in time the MRJ2 indexer was replaced and default settings were used. Maybe the hdd failed, who knows, no institutional memory.
I did check for an early unclamp signal.
I'd love to see a parameter file for the controller from a QT-250. One night the evening tech got a smart guy, the next time a script reader. Tech support is a very variable quantity.
Thanks,
Wes
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