[beto81]

Hello everyone. My QT35 is making a bad noise when ever I thread a long pitch like 1.5" lead thread. Not sure if its a bearing going bad and if its a lot a work to replace. Would like your opinions before I start to disassemble the machine. i made a small video for you to see. here is the link...

Mazak QT NOISE - YouTube

[Night Shift Wiz]

If it's that banging noise I heard whenever Z axis reverses directions and it's not way covers banging then it's probably extreme backlash. Most likely bad or loose TAC bearings on the ballscrew ends. Very easy to replace. Make sure you install with correct configuration.
Check your ballscrew and if it's oily and not galled then the ballnut should be OK. That would be your greatest expense. The rest is just bearings, couplings and mounting hardware to check. The biggest pain will be pulling back the Z axis way covers. If it comes to that, be sure to adjust the Z axis gibs while you have the covers back.

[beto81]

As of right now I am waiting to receive a sf-pw power supply because machine is down and turretis not at a good spot to disasseble. Night Shift Wiz is their a way to tighten the TAC bearings incase they are loose? This would be my first time playing with this bearings. I am good at other things but NO clue on the TAC bearings. Will appreciate your help.

[Night Shift Wiz]

As of right now I am waiting to receive a sf-pw power supply because machine is down and turretis not at a good spot to disasseble. Night Shift Wiz is their a way to tighten the TAC bearings incase they are loose? This would be my first time playing with this bearings. I am good at other things but NO clue on the TAC bearings. Will appreciate your help.

Yes, there is a spanner type nut on each end of the ballscrew. Should have a star type locking washer with bendable tabs to keep the nut from backing off, or perhaps it's the bigger type nut and it will have a set screw to lock it down.

I just noticed the axis is not direct drive, but has a timing belt. Check the belt for looseness or damage. Usually you'll get excess lag alarms if it's a bad belt or encoder coupling. You'll have to remove the encoder and belt pulley to get to the bearings on that end. That may cause a small change in drill lengths. There should be two setscrews to loosen on the ballscrew side of the coupling, 90 degrees apart.

Before you do anything, take a 2x4 and try to move the turret body back and forth, perhaps by prying against the tailbody. Any movement over a few thousandths that doesn't spring back is a problem. If it's loose TAC bearings you should be able to see the ballscrew move in and out of the bearing housing. If the bearings are bad and you tighten them up it will really howl.

[beto81]

Than you Wiz! It was the locking washer that was loose that needed more tightening and was creating that bad noise. My machine was down ever since I was repairing the power supppy. I just notice I have another problem with adjusting the GIB on the cross-slide.

Here are the instructions of the book.

1. Remove wiper.

2. After loosening the uper bolt, press the gib upward to release the gib.

3. Measure the backlash of X-axis move and enter corresponding compensation data to the control.

4. With loosening the lower bolt, tighten the upper bolt fully.

5. Return the upper bolt about a half turn from the fully tightened position. After that tighten the lower bolt fully to secure the gib in position.

6. Measure the lost motion. When the measured value is less than .0002", the adjustment is complete. If it is larger than .0002", readjust the gib.

I am confuse since the BIG tapered side gib is in the bottom of the cross-slide, where it pushes and tightens the gib. Instructions appear to be in OPPOSITE direction.

Machine is not repeating dimensions and when moving in the negative directions(down) first move it jumps a couple of thousands. Machine is running worse now that I started moving the gib.

WHAT DO YOU THINK?

[murphyc1]

Have you checked bearings at pulley end on ballscrew and that nut is adjusted to take up slack ?.

[beto81]

Hello, here are the steps I did. Please let me know if I am doing it right.

1. First having the top side disassembled(pulley side), I turned the ball screw shaft by hand till the bottom nut reached full contact on the bottom bearings.

2. Then I install the top assembly and tighten the nut to full contact.

3. Then went back to bottom nut and tighten it more.

In the meantime I ordered 2 new top bearings. One fills smooth and the other a little rough. But I still do not understand how can they make the x-axis move that much if the 2 bearings are sitting side by side and having both together, the inside does not move to the sides at ALL by hand.

[murphyc1]

Just trying to eliminate all possibility of backlash. With adjusting gib I found that if I go by instructions it is too tight so I adjust until it feels right.

[beto81]

Oh yes my bad. Gib adjustment I went by the book too where not tight and loosen about 1/2 a turn back when fully tight.

And on the ball screw slack were the steps I wrote before this final post.

[Night Shift Wiz]

You can also adjust gibs using the loadmeter for that axis. Usually, a 10% increase in load is what you shoot for.

[beto81]

You can also adjust gibs using the loadmeter for that axis. Usually, a 10% increase in load is what you shoot for.

Yes, I did adjust gib with a little load, but gets more slack up and down. Someone know the right procedure to take off slack or go you think bearings may be bad. I should receive the by Friday and would like some advice on installation. Thanks for everybody supporting.

[Night Shift Wiz]

Yes, I did adjust gib with a little load, but gets more slack up and down. Someone know the right procedure to take off slack or go you think bearings may be bad. I should receive the by Friday and would like some advice on installation. Thanks for everybody supporting.

Not sure what you mean by slack unless you mean backlash. Shouldn't have more than a few thousandths which you then adjust out with the backlash parameters. We just sold a QT28 cause it had a bad ballnut in X. Would have cost a few thousand to repair.
Determine where the backlash is at. Prying up on the turret with a large 2x4, does a locked ballscrew move up and down in the TAC bearings or does the turret move up and down on the locked ballscrew. If the latter, you're looking at a bad ballnut or loose nut hardware. The former would be bad TAC bearins or loose hardware.
New TAC bearings have a ^ inscribed on the outer races of the two bearings. Make sure they line up to complete the ^. Make sure you clean and repack the new bearings with good grease.
Mazak recommends .0012" stretch on the ballscrew after you tighten the nut. Most of the time it is set by a spacer and you just crank the nut until very tight. If not set by a spacer you can get it too tight so then you measure the stretch.
If you can't get the old bearings out because of the ballscrew, you can block the turret midway, take the nuts off of both ends and turn the ballscrew by hand to push the bearings out.

[ARcncCONSULT]

Hi, how did it all work out, did you get rid of the noise and does it make good surfaces too?