massive backlash problems!?!?

sudsy55 said:

Have you checked for endfloat on the ballscrew? Could be a thrust bearing gone. Is it noisy in rapid?

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xa-mont said:

I haven't and I also don't know how to [emoji23] it's not exceptionally noisy, but I'll do some more listening now the shitty old guard are disconnected.

Sent from my G8141 using Tapatalk

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noname777 said:

what dial indicator is touching? Turret? What is happening when you move Z axis? NC send a command to SERVO MOTOR, motor rotates and through coupling rotates ball screw, ball screw nut is attached to the carriage (never seen ball screw nut bad on any MAzaks in whole my life). Carriage has two rails (x asis) with GIBS that needs to be adjusted periodically , as it is not linear bearings. Then after this, rails movement( more like X rails gap) passed to turret itself.

if that is not overcompensation of Z axis backlash through NC parameter, than it would be gibs that must be adjusted , to compensate X-axis rails wear.

by the way, your dial is 10 micron division, jumping around 6 *10=60 microns. That is quite normal for this
pile of casting, hardened steal and old Mitsubishi electronics. Buy a beer and take it easy for now, or adjust gibs on X-axis rails . =)

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noname777 said:

probably let me see it again
i dont get it , honestly.
can you write it down step by step what you do.
and what Z-axis numbers on POSITION screen are doing at this particular time

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hitandmiss said:

First question is WHAT does the indicator read at step 6? If not 60 Micron, what is the reading? Nowhere near 0 is not helpful at all.

The important missing info is any history of the "problem"
Is this a new to you machine with this problem?
is the result of a recent crash?
Or things were working well and this just started?
What is the backlash setting?
Have you made any changes to the backlash parameter?

I would use an indicator with longer travel and lower resolution and see what you have for problems over 10mm travel.
Also check again 500mm away and see what you have.

Since you don't know how to check for end float in the ballscrew, I would find out how before messing with parameters.

Bill

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Richard King said:

First I would clean machine up a bit. with the head centered in middle of travel Then I would set up another indicator on the end of the ball screw then with a bottle jack and a 4 x 4 wood between the head and table pump slowly and check for backlash lost motion and se if its a bad ball nut or thrust bearing, Then move it to the top of travel and do it again. If the screw moves then you know the bearings are loose. They should be tight and sometimes we stretch the screw a few tenths after it is no backlash. I would also suspect the nut / screw is bad and has backlash from the looks of how filthy it is. also move the zee down all the way and use a mirror and flashlight (torch, what they call them in uk) a
nd look at the ball screw and see if there is a wear grove on the threads. If there is a groove you will bed to replace the screw / nut assembly or have it repacked with larger balls.

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xa-mont said:

hey guys, got some mad backlash going on in the Z axis on my ST30ATC m/c - i'm talking nearly 1mm of lost motion.

Here's a video of me hand wheeling 1mm... (after going 1mm+ setting indicator then 1mm-)

Shared album - Travis Hammond - Google Photos

Clearly not ideal! where should I start looking? could this be as simple as a thrust washer issue (ball screw turning but not transferring the force)

I'm also able to rotate the ball screw a very small amount by hand, is this also no bueno?

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Ziggy2 said:

It look likes your thrust bearings is bad. The ball nut also seems to have way to much motion.

Do you have a lubrication problem?

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xa-mont said:

i don't THINK i have a lubrication problem. the way this ballnut (and the x i assume from the noise) is lubricated is from an air purge with an oiler in line, and there's definitely air coming out, and the most used part of the z ballscrew has definitely had oil on it. I suspect it could do with a bit more though, which may be down to the air pressure being either to high or low, not sure.

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Ziggy2 said:

How much oil is going through the lubricator. Blowing air only tells us that the air is working not how much oil.

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xa-mont said:

so... i found a thing... and i feel like a knob... i expect everyone should remind me of this constantly.

i was removing the bearing cap on the tail end bearing housing to check out the thrust bearing and see if it exploded out in a mess of bearings/cage when i opened it, and it was then that i noticed. the rear bearing housing was loose AF! like the bolts weren't even finger tight!

I tightened that bad boy up - took some measurements - messed with the BL parameter and here we are...

[video]https://photos.google.com/share/AF1QipObB89lhjBkNzz0CoZUfVz8HBl0ig3Cxs4e3UM0LCikbM 0maKngPOmqJPfZp5lHxw/photo/AF1QipM7trFgPeg0Xc6uR8qrveEaHlcWDkrTab-5N1Gx?key=Z1BmOE9qNXc4Z01ZekhmdV9nZkgtOExHUUtrT3l3[/video]

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noname777 said:

you almost got me killed! I opened your video while sitting in headphones, Jesus, that thing that you always film, .. goes always unregulated into my USB-headphones amplifier. If I die, who is gonna save the planet???

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