Mazak QT20 ralligning tail stock, Phil??

Phil, first off thank you very much for the info on realligning the turret, it drills like a dream, #10 drill with 6" of flute, dead nuts, on size 4" deep.

Not just for machtool, he was just very helpful last time. I have a whole pile of tailstock jobs coming up and this tailstock is way way way out of whack. Its pretty consistant at .0255 out. Wheather its 4" long or 13 inches long I need to program in a .0255 taper to get a concentric shaft. I'm hoping its the same as the turret with the tapered pins.

I haven't looked at the schematics yet, and the manuals offer no help, so any advice would be greatly appreciated. No politics though.

Thanx

depends on the age...
the newer (95 or better maybe)....have and ecentric quill ...undo the wiper and there are some bolts loosen them and loosen the arm that holds the rod that trips the location prox swithes this allows you to turn the quill to make the adjustment....but...
you only got 20 thou or so to play with in the tailstock ,,if it's more than than that you have to straighten out the head stock first.....
open the door all the way there is a row of bolts that hold the front cover just inside the door on the "firewall"...
then take the end cover on the spindle end and you will find another bolt pattern that holds the other end of the front cover....you do not have to remove door to get this cover off...
once you have cover off the spindle mount is right there...6 - m16 holding head down (m14 wrench)...i allways loosen all 6 then snug them back down and take a .015 cut, if whoever set this up last time had the jack screws good and tight the thing will go right back to within a few thou.....if not....there is a set of push me pull you bolts to make your adjustment's back and forth (an m6 and an m8 wrench i think)....i gave up trying to use an indicator on this as mazak has the head pivot on a pin that is about 10 inches or so back from the nose...just to much geometry for me to ever figure out any numbers....if you pull the head a tweek and take a cut once or twice you'll get a feel for how far to go....
be carefull that you get the prox rod back in nice and straight or you might chop the head right off your prox switches (been there,done that)

on an older machine say 90 or 88 you got the big bed machine....
there's four bolt's holding top half of tailstock to lower half.....there are 2 right in front coming up from bottom and it's been so long that i forget if the other 2 are in the back behind a cover or inside the cover where the big cylinder nut (i think in back )...loosen them and then there is an apposing set of bolts right between the 2 half's just like on an old engine lathe..loosen one and tighten the other....tailstocks are pretty good about how they move i usually go for about 65%or error....if it's out .010 move it about 6 and a half thou....on the big bed machines you can move the tailstock a mile but it is still best to set the head first.....
if you got the old big bed moven the head sucks....you gotta climb in the end...there's a set of big (24mm or so) hex head bolts some up and some down and 2 behind a little cover in the machine compartment....loosen them and then the adjust ment is right on the end of the headstock behind the belts it's 2 hex head's coming out of a little round boss upside down.....same thing as all the rest... push me pull you.....
hope you got the new style...

not sure you mean concentricity though as this is a whole differant story....maybe bearings

Wippin. From memory, I think Bobs machine is has a little age. Mid 80’s I think.

There was a picture of it in the last post with the turret problem.
Similar Turret and tailstock to Bob's

Bob.

Not much more I can add to what Wippin has just explained. I’d concur with every thing he just posted. But just summarise some. The reason he mentions the head stock, is you have to have a datum. The spindle has to be turning true to the Z axis rails. I’m guessing yours is, but if that’s tilted to the Z axis feed, and your turning tapers on chuck only work, that needs to be corrected first. If you do that, it will move relative to your turret X position also, buts that’s only a grid shift or offset adjustment.

I normally test cut a decent sized bar 6 ” long, light cuts. Often under cut the middle some, so you leave two test collars, one near the chuck, the other 6” out. I think spec was 0.020/150mm. But must be smaller away from the chuck, so when you get back to production feeds, the deflection improves the geometry/ parallelism of turning.

The bolts Wippen described. They can be real tight, and hard to get at spots. Expect to loose some skin on your knuckles. I don’t fully tighten them in between test cuts. Just past snug, the head stock wont let go, just doing light cuts until you get it right.

There won’t be tapered pins in either the head stock or turret. I’d need to grab a manual. But I think yours is just adjusted, at the base, not un-like a conventional centre lathe

Regards Phil.

You guys are good, to clarify, the machine is a '98. Is it really that hard to knock the headstock out of alignment? The only other lathes I've dealt with, if you knocked the headstock out of alignment, you had a busted casting.

The headstock being off would make sense, after realigning the turret the drilling center point moved by .050". I figured somebody had hit the homing switch while we were replacing a coolant hose. I do have to program a taper into almost everything, though most of what I do now is way longer than what I was doing before, so I thought it was normal. Guess its not.

Off to the races again tomorrow, thank god nothing on the lathe is 'hot', well it is, but the fruity @$$ in purchasing is too lazy to buy material, (not my problem).

Thanx for the advice, Its worth many beers, if I ever meet you guys anywhere.

Bob

Is it really that hard to knock the headstock out of alignment

Click to expand...

No its not that hard, and more common than you would think. I think that’s the remnant thinking of conventional lathes where the head stock sat on vee ways that were an extension of the bed.

Not all but most CNC lathes post 1970’s, the head stock mounting face is just flat, onto a flat surface on the base casting. Normally with a large dowel as the pivot point, and a means to swivel adjust them for alignment.

The surface finish of the mounting faces has to be very good, ground and / or hand scraped to get the other alignment. (Spindle pointing Up / Down)

So you have two very good surfaces that are only held by surface friction applied by the bolts. Even in your case 4 or 6 M20 or M24’s. A decent jolt will un-settle the head stock. Which is actually a good thing. If you have hit the chuck, that force has to go into the spindle bearings. It always amazes me. I see head stocks that have been sprung, all the time. Align them up, and the spindle bearings run fine, for years on end.

If you think about how much mass you have in your turret, and those two dog-legged taper pins you found in your curvic coupling. Its not inconceivable that a hit like that, will over come the bolts holding the head-stock. The impact that moved your turret, had to be opposed by your spindle. Chances are they both moved.

That’s why I always check the spindle to ensure its pointing true, first and foremost. When you have a datum, the rest follows. Upper turret, Lower turret, sub-spindle / tail stock. Once your spindle is pointing straight down the machine, every thing else should look back at that datum.

I figured somebody had hit the homing switch

Click to expand...

It’s not the homing switch that gives you the real home / zero position. That’s more like a you’re in the ball park position of the axis travel. “I can rapid up until I hit the switch, then I’ll slow down and look for the reference mark off the encoder”. The encoder, being attached to the ball screw, has far more accuracy / hysteresis than the mechanism of the limit switch. The real zero position comes off the encoder.

It’s an odd ball pulse that only happens once per revolution of the encoder. Null, Ref pulse, etc. There’s several methods to find it. Some rapid until that switch, then slow down, and find that next reference pulse in the next turn of the encoder. Some slow down (Mazak) and ride over the limit dog, and find that reference pulse after they come off the dog.

Cutting a long story short. A shift of 0.050”, wouldn’t be to do, with hitting the limit switch. You can move your limit switch striking position until the cows come home. It’s not until you move the switch by the distance of the ball-screw pitch, that it will jump by that much. Slight movements of the switch tripping, don’t move the position, until your more than the one revolution of the homing pulse coming off the encoder.

Regards Phil.

"hard to wak a headstock"
not in my neck of the woods
the picture shows the type of tailstock with the eccentric ajustment
head taper will throw your numbers all over the place...
when you get that head taper out, your diameters will change again...
just snugging bolt's between test cut's is right on the mark .....
i've set these heads a million times and i would suggest pulling that front cover...it sounds like extra work but it makes the job go twice as fast and saves those nuckles and a scrapped head or two (mines all skin so that ain't fun)....besides you only got about 4 bolt's to put back in when your done
mazak calls that there Z pulse and your desciption is right on.....it ain't bumpen the switch that changed his numbers it's that melted holder layin on the bench

I didn't get to check anything out on the machine today, there were 3 others to get up and going. I didn't know that about the limit switches, that would explain why our Mazaks always come in within tenths when they get fired up in the morning. How come the Fadal doesn't always repeat when powered down? Thats why it stays on and we punch the e-stop at night.

All your info is really appreciated, but you do realize that your putting some poor machine repairman out of business, yeah poor $85 bucks an hour and I don't know if we would have to pay for the three hour each way travel time. Actually you didn't put anybody out, I would have dug into it myself and tried to figure it out from the crappy schematics in the manuals.

One quick question, if the headstock is knocked out why does it produce a taper? I'm guessing that the rear end of the headstock is fixed further back in the machine. So, now that the headstock isn't parallel with the Z axis there are going to be some serious forces on the headstock, the bearings or the mounting surface? Its not much of a guess to figure that that is bad and I should fix it ASAP?

Bob

>>>“One quick question, if the headstock is knocked out why does it produce a taper?”<<<

In the great majority of C.N.C head stocks, they sit on a location pin, smack back in the middle of the joint face. With bolts arrayed around the perimeter of the head stock. If you took all the bolts out, belts, guards etc. You could spin it like a top, around and around on the centre location pin.

So in your case, with an upper turret. If you have had a knock from above, it would have sprung the head stock C.W away from the offending impact. Same reason your turret was low.

I’d almost risk a bottle of Kentucky’s finest, that when your programming taper correction, you have to pull the tool away, as you get closer to the chuck. Programming X plus towards the chuck. I.E On an un-adjusted cut, your diameters are bigger, the further you are away from the chuck. Smaller near the spindle? And it looks like you have to move your tail stock down, when turning between centres – your diameters are smaller near the tail stock?

There wouldn’t be any residual force’s still present after the knock, so if your spindle bearings have tolerated the hit. Maybe a little shear pressure under the bolts and washers. I figure that’s why some times they are extremely tight to break open. Hence the skun knuckles.

Fixing it A.S.A.P! I wouldn’t shut the machine down, if you have work to do, and can get good parts off it. But next chance you get. It’s a great Saturday job, when the phones aren’t ringing, and you can concentrate.

Then dial in your turret, so it doesn’t matter if the centre you’re trying to put in, is on a short part near the chuck, or hanging 10” out. Same with your tail stock, if the heads pointing true, it shouldn’t matter if the tail stock is at the end of the bed, or dragged up to half way along.

I’d note, that with the percentage that tail stock’s are used. If they weren’t in contact when the machine had a hit, nothing moved them. So they stay exactly where they should be. Same with sub-spindles. If the hit happened on the main. The sub stays close to true. If I’m in a hurry, I’ll dial one in to the other, if they were right to begin with, the main spindle falls into line fast.

If you imagine the centre line projecting form the spindle axis, and project it out into the machine. If its tilted away form the Z axis / rails. The centre of your part will be at different places, depending if it’s a short or long part. Because it’s rotating around the centre pin, locating the head-stock.

Regards Phil.

I'm getting a little scared. So now, I think I have my turret all nice and happy, but, is it possible that crash that happened threw it unsquare to the Z axis? When I swept all the boring bar/ drill pockets, they came in really nice, though I only swept the front of the pockets, at the same distance from the chuck.

If my turret isn't square with the Z rails do I have yet another adjustment to make, and how easy is this one?

You win your bottle, bigger at the chuck. That would also explain why the tool eye seems to be jumping all over the place in the X axis, also why I have to program a bigger taper into the partoff tool than the face/od finish tool.

As far as the tailstock only being affected when a crash occurs when it is engaged, the guy before me hit it a couple of times with the "tailstock barrier" disengaged, jogging. I did it once, the first time I touched the machine.

Thanx for the info, I think I'm in for more than I thought, no big deal, it will just be easier the next time.

mazaks are tough as nails
just straighten it out when you can and move on,
if it's hurt it will let you know in time...
i've seen wrecks that would curl your hair turn out to be "no harm no foul" and others that didn't seen like much that took the bearings out in 2 months......lifes to short to fret over spilled coolant

So, what takes out bearings, I just want to know, so that I know what to look out for.
Had a bit of a crash today, its a new one for me, trashed a 7/8 Kennametal insert drill. Thats only $200+. It came loose in the holder, pulled out and slammed into the 1.25 304 we were running.

Really easy to keep going, just pulled the sister drill out of the mill and replaced it with a twist drill. The twist drill only added a tiny fraction of time to the part, but the indexable drill is key to the lathe. Ordered up a new one, it will be here Monday.

Probably knocked the turret out again, but, I guess crappy things happen. Just a nice little 'thud', no overloads. Still making good parts, so I guess that is the important thing.

A funny thing did happen today tough. I'm sure most of you get used to the sound of your machines and can tell when something is going wrong (you know a KKKKKKKKKKKKKKRRRRRRRRRRRRRRRRRRRRRR is OK but a KKKKKKKKKKEERRRRRRRRRRRRRKK will send you flying because a tool broke). Well there where some low flying jets today that had a very bad machining sound to them, so I went hauling down the stairs, hurdled a pallet of aluminum plate and hit the stop button, the really bad machininig sound didn't stop, so I hit the reset, which just stops everything (I hate the Big red button it takes too long to fire it all back up again), the sound didn't change, and the guy working on another machine, just looked at me and said 'dude, your hearing planes'. Oh well, I figure better safe than sorry, thought I am sorry, $200+ worth of sorry today.

Bob.
Quote -”So, what takes out bearings”. There no hard and fast rule, lots of luck involved. I’ve seen spindle knocked so hard, that have broken master jaws. A couple of ATC35’s that have snapped the retainers about the slant saddle, and the spindle has tolerated it. Other far less drastic hits, and the spindle is toast.

Short of commissioning some one with a bearing analyser, to measure the noise signal coming out of the bearings, not a lot you can do. Even the analyser’s are subject to a fair bit of determination. There fine if you do P.M checks, so you have a good signal to compare too after a hit.

Only thing you could do in the shop, is listen for rising noise levels, bad sounds, deteriorating surface finish & heat rise.

The worst hits are when the spindle is stationary. That allows the balls to imprint the races. (Brinelling). Is you ever have a look at any technical bearing catalogue and notice the load rating capacities for Static (Stationary) and Dynamic (Rotation) loads. The dynamic loads for angular contact bearings can be nearly twice as much, as static.

Not to fear, your Mazak, will have a dirty great big double row roller bearing closest to the spindle nose. From memory, I think they are NN3020 Kxxx taking the radial load, and a set of NSK BA10X in a 30 deg taking the thrust.

First catalogue I pulled for that Roller bearing (SKF) lists the load rating at 151,000N –(15,392 kg – 6700lb) static, and 247,000N –(25,178kg – 11.450lb) dynamic. So they will take a fair amount of abuse before you over-load them.

One thing you could check for. If you look at the very bottom of the spindle nose shroud. Often there’s a small drain hole, to let any coolant out that has been flung out by the labyrinth or slinger. Occasionally that hole will block with corrosion, or dust that’s gotten in under the shroud. That lets the water level rise, until it weeps back into the bearings. I see this often. Especially on machines that have been running some of those engineering plastics.

Regards Phil.

first time i did a mazak spindle i took that pretty solid brass cage tapered roller...polished it up and put it in the fish tank.......
prettiest bearing i ever saw
increasing noise is my key also....if it ain't "running out" too much for your application I am sorry to say I have run them for a pretty long time with the first "nik"....i figure every hit in the face after that is a free one
and at my place they get plenty....
the "wreck" you describe is a fairly mild one
as stated jaws in the chip box and saddle keeper bolts ripped in two are where you start gettin' in trouble and even that won't allways do it on a quality machine tool
and the qt20 you got IS that

i can tell you for fact as of 6 am this morning what WILL do it......
a 47 pound slug, a 2 inch insert drill, 1400 plus inches a minute in rapid.
250 thou of aproach clearance programed into a job and the operator sticks in a 400 thou over sized slug and hits the go button.....this was a new guy so he still liked to put his nose right on the glass and watch the fun....
.
wac....
.
$18,000 integrated spindle in the dumpster....
along with the guy's breakfast....
so....
leave those door interlocks intact kids cause the face you save may be your own

Ouch, that doesn't sound pretty. I hope the kid didn't get hurt. I guess he'll be working for free for the next year, or at least the guy on the bandsaw.

I finally got around to lining up the headstock today, pulled the front covers off, that took a whole 3 minutes. What a mess in there, oil all over the place and tons of chips, I'm guessing this is normal?

At first it seemed that I would have to loosen the bolts down at the bed level to adjust the headstock, until I cleared out some of the chips, and got rid of some of the oil. The headstock is sitting in a nice little cradle, 6 big monster bolts and one pin to rotate about, towards the front of the machine, between the first and second bolts from the chuck. The most difficult thing was finding a 14mm hex bit in town.

Anyways, I got it to within .0008 over a little more than 5", taking light test cuts after each adjustment, of course I tried to get it even better, it got worse, then I got busy doing other things and its going to have to wait for the morning. So what kind of taper would you guys consider acceptable? I'll probably be pretty happy if I can get within a tenth per inch, much better than the .005 to .006 per inch I had. BTW how do they line this guy up at the factory, I was at the Mazak factory last fall, but this wasn't on my mind then, sure wish it was.

After this, back to check on the turret and then onto the tailstock. One more quick question, is it possible to knock the turret out of perpendicularity with the Z axis, and how would one go about tackling that problem?

Thanx for the advice, it made my life a whole lot easier.

Bob.

If your down to 8 tenths at 5 inches. Your pretty close to being in spec. Of course you could try to get it better, That’s normally when you spring past it, and start going the other way.

Remember your measuring on diameter, so the head stock to z axis alignment is half of that.

Just mark sure you have it the right way. With only an upper turret, You want the diameter at your 5 inch mark (Further away from the chuck), smaller than the diameter close to the spindle. That’s so that when you go back to production speeds and feeds, the part will deflect away from the tool and get a larger diameter. So if you have it aimed towards the turret slightly, the deflection works in your favour

So you don’t really want it Zero – Zero over 5 “ when your only doing light test cuts. Cause it will only give you large diameters away from the chuck. You have to find the sweet spot that suits your work. But if you leave 4 – 5 6 tenths / dia on it, it will run better latter.

Factory guys use nice hardened ground spindle mandrels. Just plug them into the spindle, check them for run out, and clock off that.

You would have to refresh my memory on the turret. Lots of the Mazaks were a one piece casting, turret body and X axis slide. If it’s the ones that bolt on, its not unlike manipulating the headstock. Regards Phil.

Thanx Phil, thats the little bit of exta info I needed, BTW the turret looks like the one you had linked to in this thread here, 2nd post.

http://www.manta-machinery.net/photos/4197_3.jpg