Changing x-axis thrust bearing SQT18M

noname777 said:

you replace two at the same time, both bearings.

to pull this bearing out you have to use ball screw. Sort of like that.... if you undo both bearings and then somehow put wooden blocks inside the carriage to hold X axis motionless, then... by rotating ball screw itself ( carriage is fixed) ball screw will move and push out the bearing from its housing. Same rules apply to second bearing.

Change two at the same time and make sure you put them in right way with lots of grease.

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gmc1724 said:

Is this the standard way of changing these bearings? Seems a bit extreme to have to use the ballscrew to press out the bearings, has anyone else tried this method?

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noname777 said:

it is the only way to do it. no drama at all. Bearings are sitting in housings just like that, I mean ..there is normal tolerance for housing. just dirt keeps them in. Once you clean them and put some grease, you will be surprised how easily they go in.

p.s I did myself at least 10 times. no one ever called me back to go and replace them again =) what is important is ball screw preload and bearings preload. You have to measure old bearings, they thickness, then if new one is different, you have to grind a bit a support plate . the Idea is to make sure bearings are preloaded ( sort of to have > > signs on them and they are compressed to eliminate the gap in between, cause you must have at least two bearings that are assembled as one) and ball screw is slightly stretched to compensate therma lexpansion.

p.s.s. you do rotate ball screw in this procedure by hand. In no practical way you can damage ball screw... as servo motor can develop such an extreme torque and huge amount of force when it moves turret, you hand is nowhere near to create any problem for ball screw itself =)

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gmc1724 said:

Sorry to be a pain noname777, the procedure involves disconnecting the servo belt, ballscrew encoder and bearing cap and thrust bearing nut at the top of the assy' then blocking up the turret to hand turn the ballscrew to push out the bearings at the bottom bearing housing, correct?

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noname777 said:

sure, more parts you remove better for you, more access. What you do now is next:

-have a tool in your turret, use tool eye and teach it. Make sure you know X position,
cause when you put everything back, you gonna lose this X-axis home position shift. Once everything is back, you teach same tool again and see the difference. That difference will go into X axis home position shift( parameters screen)

-very old machine, never done this particular one. Any way, encoder has to go, then nut, then gear. Then plate 31 and ball screw has to be pulled out. That plate 31 might be the one that preloads bearing, if preload is controlled by outer rings, not inner rings. That is if new bearings have different thickness, plate 31 needs to be machined. I need to call my man and ask him if I am right. Old man has more knowledge about old Mazaks.

-lower bearing is same story , but this one has this funny labyrinth sealing, positions 44 and 46. I cant figure out what to do with them. I am under impression that ball screw has to be pulled from the right side. Bottom housing is bolted to the carriage and it has two dowels. So it stays untouched as a reference. Top housing can be removed, that will give access to top bearings and let you pull the ball screw and somehow remove bottom bearings. ( again, I am puzzled with the way this labyrinth sealing is done, drawing cant be doggy) Any way, if you do it this way, then when you assemble everything back make sure you put right housing in right position and not bending ball screw ( move carriage up and down and let ball screw find its place). I will have a look and chat to some guy, maybe what I am telling you is absolute nonsense, but honestly, from this picture I cant understand lower bearing assembly.


Wait a minute.... I found drawing for your machine someone sent it to me the other day.

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