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Mori Seiki SL4 Z axis frozen

JZZ30

Aluminum
Joined
Dec 20, 2007
Location
CA
Hopefully someone can help with this, as I am pretty stuck at this point.

Recently purchased Mori Seiki SL-4 with Fanuc 6TB. Was running prior to purchase, but sat for a few months before it was recently powered up.

On startup, zero return for X works ok, including when it starts close to end of travel (reversing, then going forward again). Z worked ok once, but on another power up, it seemed to have barreled past the normal travel limit, then shut down with a bang. After that, it shows 421 and sometimes also 423 errors. I took off the way cover and tried to turn the ball screw. It would move slightly in either direction, but everything was still frozen for the most part. The Z servo was removed and checked, and everything seems ok. Even with the servo out, the ball screw feels the same "stuck".

The turret assembly is unfortunately sitting over the mounting block on the end of the ball screw, so it is not accessible. This is making it pretty tough to release the ball screw from the turret to see if it is the ball screw or the turret that is actually locked up.

The machine looks to have traveled even further than this at some point in the past, as the heavy cover on the end of the Z ways is dented out from some previous incident.

What to do or check at this point? Anybody have any experience with this particular machine and anything like this???
 
I'm thinking that you have jammed the ballnut against the thrust bearing housing. Getting them apart will be a purely mechanical job to twist the screw apart.

At one time there should have been a urethane "bumper" to on the thrust bearing housing to soften the hit if a switch failure allowed the axis to go beyond the hard limit switch. If this has happened before, combined with age the bumper could be gone or if still there be nearly hard as a rock.

Once you get this backed off, you need to carefully examine and test the reference decel switch and the hard overtravel switch and the dogs that actuate them.
 
Hope this helps! All the Z switches and homing proximity switch and dogs are under the cover [about 5ft long] on top of the fanuc cabinet at the back of the machine. This is for my 1983 machine yours will be the same or close if it has 6TB. Also their is a Feed box on the end Z ball screw then the servo motor that could be why its hard to turn even with the servo motor off.


mori Z.jpg
 
Thanks Vancbiker and twr for your responses. Also thanks for all of your great support here,
I've learned a lot from your posts for many years now!

I'm thinking that you have jammed the ballnut against the thrust bearing housing. Getting them apart will be a purely mechanical job to twist the screw apart.

At one time there should have been a urethane "bumper" to on the thrust bearing housing to soften the hit if a switch failure allowed the axis to go beyond the hard limit switch. If this has happened before, combined with age the bumper could be gone or if still there be nearly hard as a rock.

Once you get this backed off, you need to carefully examine and test the reference decel switch and the hard overtravel switch and the dogs that actuate them.

Great info. I did feel like everything was jammed full right against something, but wasn't sure where the "end" might be, or what would happen when that was reached. What you suggest makes sense, with the nut basically tightened all the way down against the end block.

I've attached a picture of the end cover that had been bent previously. It also shows where the carriage is presently stuck. One thing though, if it is full right against the bearing housing now, this previous overtravel damage almost doesn't make sense. But then again, who knows what could have happened in the mysterious past to bend that plate! Could be one of those wrongly interpreted clues that makes diagnosis even worse sometimes LOL :willy_nilly:

I'll need to try to get a pipe wrench on there towards the headstock end where the threads stop and give it a good yank. The measly channel lock pliers aren't up to getting any serious torque on that large and slippery of a shaft.

Definitely need to look into putting a good end bumper in there no matter what. Good tip that it might be missing altogether at this point. :cool:


Hope this helps! All the Z switches and homing proximity switch and dogs are under the cover [about 5ft long] on top of the fanuc cabinet at the back of the machine. This is for my 1983 machine yours will be the same or close if it has 6TB. Also their is a Feed box on the end Z ball screw then the servo motor that could be why its hard to turn even with the servo motor off.

Thanks for that diagram. I had seen it before, but the useless reference of where that actually was didn't help LOL! I looked everywhere from the front of the machine and saw no traces of limit switches anywhere, and haven't investigated since. Good info on the rear service panel, I didn't even realize that was "a thing" until you mentioned it here.

The panel was a little tweaked on the lower headstock side, so it was wedged in and was a pain to get out. Gotta straighten that sheetmetal before it goes back in, but no biggie there. After that, the access was nice, as I was able to clean out more of the chips and gunk that was built up in there. I think the machine was last fully cleaned in nineteen seventy never. I'm sure it is happy to get a good once over before I start its next era of owner neglect :rolleyes5:

I attached a picture of the switches in relation to the dogs and the carriage. The locations are as to-scale as I could get them, but maybe not so much. Looks like it's not yet at the machine's limit area??

I think I'll order new switches anyways, as a preventative move. As per Vanbiker, carefully is the key word here once this thing is moving again on Z. :eek:

Any good sources for them offhand? I saw ZC-Q22 as the OMRON part number/crossreference.

2017-04-24 17.30.45.jpg2017-04-24_17.28.25.jpg
 
This is for my 1983 machine yours will be the same or close if it has 6TB. Also their is a Feed box on the end Z ball screw then the servo motor that could be why its hard to turn even with the servo motor off.


This is a ~1980, so yes it is a 6TB.

I actually have the servo off right now, so I think there is pretty much no load from the headstock end of that screw. Entertaining story on that, I looked at the housing and decided (convinced myself) that the oil in there would not be related to the servo motor's mounting. I won't describe what happened when then oring seal popped loose at the bottom... Luckily I was quick and shoved the motor back on and got a bolt on and stopped the river of oil. Still, what a mess!! :angry:

Oring was slightly damaged, but I think a generic viton should fit. That's some pretty tight clamping on there, so it seems like a slightly larger thickness ring should be ok (.125 vs the ~.080 that was on there).

A side note. It doesn't seem like the servo is clocked in any particular position? I hope that is true for when I put it back in.
 
Did you take the front or chuck side way cover off Z axis? I don't remember but i thought the servo was keyway to the feed box? Vanc can correct me but it may matter if the motor is not in the same spot or it maybe just a matter of rehome the Z axis. When you removed the motor did you remove the pulse coder with it or did you take it off and then the motor? Its hard to tell from the Z axis picture but that looks close to where mine is at home but it doesn't take much and it would be passed the switch.

When you first tried to home Z axis did you move the jog lever towards the chuck or the tail stock? If it was shut off with the Z axis close to the home switch or at the home switch and you moved the jog lever towards the tailstock it likely blew passed. Best way to shut it down is a few inchs away from X and Z home then when you turn it back on is jog Z axis towards the chuck it will move a few inches then reverse towards the tailstock on its own and home, same with the X axis jog towards the lathe center line and it will reverse on its own to home X axis or aleast on a 1983 model.
 
This is basically where things are at right now. I just noticed that the back tall panel had overtraveled past the edge of the machine and bent itself on that pin hinge thing. Not sure if that happened just now or before, however.

2017-04-24 19.22.59.jpg2017-04-24 19.23.17.jpg2017-04-24 19.24.08.jpg2017-04-24 19.24.42.jpg2017-04-24 19.25.11.jpg
 
By the way the stainless sliding tin at the back only fits correct one way but will go on 2 ways, one way the sliding tin goes passed the edge of the machine a few inches the other way it slides out 5 or 6 inches so much sure you put the panels back on the way they came off. Also i seem to remember they is a cutout on the top edge of the one panel to clear something maybe that pin??? Sitting at home and can't think of why right now.
 
Clean the screw off and put some rags around it before you put a wrench on it. Hell i turned mine screw by hand with gloves on but it was not that easy with the servo and feed box still mounted!!! When i first got mine it had a Z axis servo problem thanks to Vanc and few other members i got it fixed. I also remember after looking at your picture i only had the pulse coder off my servo not the hole motor. I did remove all the brushes and cleaned the armature with the correct stone and reinstalled the brushes Damm getting old sucks i don't remember shit anymore!!!
 
After you get this fixed i would remove the coolant block and aluminum clover off the back end of turret and check a lube the X axis switches and clean the inside, I know mine looked like it had not been apart in 30 years CALL NO MAINTENANCE!!!
 
Location where I'll probably need to grab with a wrench

You might go look a bit further. IIRC the far end of the screw has flats or a square so you can crank it out of a crash.

BTW, the mounting ring for the servo motor is eccentric so you can adjust the lash in the gears. If you did not mark it before removal, you'll need to adjust that on re-assembly.
 
Clean the screw off and put some rags around it before you put a wrench on it. Hell i turned mine screw by hand with gloves on but it was not that easy with the servo and feed box still mounted!!! When i first got mine it had a Z axis servo problem thanks to Vanc and few other members i got it fixed. I also remember after looking at your picture i only had the pulse coder off my servo not the hole motor. I did remove all the brushes and cleaned the armature with the correct stone and reinstalled the brushes Damm getting old sucks i don't remember shit anymore!!!

I read about your adventures with that a few years back, and it was exciting to see an ending with a solution LOL!!! From that thread I had inspected all the brushes. Some were short (9mm or so), but not so bad. I dumped them in my ultrasonic cleaner and they are shiny new :cool: but I also have some new ones on the way just to prevent future problems. Blasted everything on the motor out with air and then some contact cleaner, and flushed out all the black carbon crud.

Yeah I first tried to turn it by hand, and it has a little bit of springy turn, but of course was not going to do any functional turning. Tried the channel locks and it didn't make much difference. I figured to check other stuff before resorting to neanderthal gorilla tactics and possibly breaking something. Vancbiker, there aren't any flats that I can see, even all the way towards where the motor is. Can't access that anyways since it's like an internal compartment area on the machine. If there are flats it may be on the side that is currently stuck under the turret. That makes sense though, since the turret would be close to the spindle for most crashes.

After you get this fixed i would remove the coolant block and aluminum clover off the back end of turret and check a lube the X axis switches and clean the inside, I know mine looked like it had not been apart in 30 years CALL NO MAINTENANCE!!!

The terrible condition of the lower Z way indicates that there might be a problem with the lube. At least that one channel. Some oil was pumping into at least one of the X ways while it has been on, so at least I know the lube system is functioning. I'll definitely heed your advise and check all of the lube passages before this thing goes back together. Hopefully there aren't any clogs in any super inaccessible areas, that would royally suck some giant donkey balls.

Do you know if these are viable replacements for the original switches?
Omron ZC-Q2255 Enclosed Limit Switch
 
You might go look a bit further. IIRC the far end of the screw has flats or a square so you can crank it out of a crash.

BTW, the mounting ring for the servo motor is eccentric so you can adjust the lash in the gears. If you did not mark it before removal, you'll need to adjust that on re-assembly.

Duly noted. The ring hasn't moved but I marked it in case of future installation blunders ;)

The motor gear meshing position shouldn't be an issue, correct? It doesn't seem like it would be.
 
If you start checking the lube system with air and blowing through only use about 10/15 psi as most the lube brass fittings are only pressed into the casting NOT threaded into the casting. I would start by removing one line at a time at the back of the machine at the connector-block and check the metering valves [ their is about 25 lines back there] when you have the line off you can blow though it at that time to check if it's blocked.
 
As far as the pipe wrench thing- turn up a split collar and clamp it on the od of the screw and ralph on that collar with the pipe wrench or put some flats on the collar. that way you won't trash the screw. Good luck with this!!
 
So an update... No luck so far :(

The screw is pretty much not going to turn enough to do anything. In any case it is turning freely and smoothly (albeit just a small amount), all the way from the motor side to the tailstock side bearing. Also inside the ball screw nut housing it is turning nicely. In a nutshell, no bearing or ball screw issues.

The ball screw nut housing does seem to be all the way up against the end bearing housing, as per Vancbiker's thinking. I was finally able to fish a mirror deep in there enough to get a look. But as mentioned, that screw wasn't going to turn hard enough to pop it loose.

So I became fed up and decided I would bully this situation and try to wedge up the whole carriage enough to lift it off of the indexing pin on the ball screw nut housing. Z gibs are now off (and were in great condition at least, no rust). I unbolted the four bolts holding the ball screw nut housing to the bottom of the carriage.

At this point, the whole assembly should just be sitting on the ways with nothing stopping it from lifting up. Or at least so I thought???? My plan was to get it up maybe an 3/4inch on some blocks and to slide it to the left so I could assess what was going on with the ball screw nut. So I tried to use a big pry bar just to micro-peek-lift the whole thing to see how unruly and heavy it was and.... NOTHING. It's like a solid assembly stuck to the chassis basically. :(

How much does this weigh?? I thought it wouldn't be much over 1000 or 1200 lbs but am I wrong here?? :confused:

Maybe it's galled/rust locked to the ways? One other thing I didn't think of before (hopefully not stupidly!) is that I only have four of the leveling pads on there right now. I didn't finish making the two center ones yet. Could the whole thing be twisting enough to bind up and jam?? Doesn't seem like this could be the case.

In any case I'll finish turning those last two leveling pads asap and get them in there, just so they are done.

The machine isn't leveled or anything, it was just recently set on the pads after pulling out the 4x4s that were under it. I might just try to get it close on that too since nothing else is going on.

One more thing to note, the lower cavity inside the X ways was totally submerged with pumped way oil. I think however it gets to the ways might be clogged, which might be how the lower Z way became so freaking scarred and galled up. I wonder if this is also related to this stuck situation!!2017-04-26_22.37.42.jpg2017-04-26_22.38.21.jpg
 
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Dumb question but didn't you move the Z axis with the Z axis motor at first then it got stuck where it is now? Or it was stuck there when you bought it? Also to lift that turret you will need a chain fall or cherry picker that sucker has some weight to it my guess would be about 1000 pounds at least.
 
Dumb question but didn't you move the Z axis with the Z axis motor at first then it got stuck where it is now? Or it was stuck there when you bought it? Also to lift that turret you will need a chain fall or cherry picker that sucker has some weight to it my guess would be about 1000 pounds at least.

It did zero return ok one time. Then I was randomly messing with it a bit. The next time I tried to zero return it, the X was ok, but the Z went fast and stopped with a big bang.

I think if it's up to 1500 lbs a prybar should easily make it budge at least little. You can easily lift a 4000 or 5000 lbs lathe a tiny bit with a prybar, so I can't see the turret assembly being so solidly unmovable??? Who knows but this is starting to piss me off lol

Trying to find one of my extra low height scissor jacks and try that.
 








 
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