My Z axis is loosing depth control and inconsistent

[faroun]

hello every one, after searching Many forums, i came to the conclusion that this
forum is the best one to get educated and get help.

My issue is my Z axis "I think"

i used this machine for around 8 years with no issues, i bought it second hand, but it worked great for many years
but lately it started acting up.

i am creating wind turbine blades, i was successful making 3 blades, but when it came to the forth blade, everything went crazy.
i am using the same pc, same files, same everything, but the issue happens anyway.

i issue is that the Z looses it consistency, it drops more than it supposed to and it lifts more than it should.
i dont get it why!? why me?!

i changed the files, with no success, so i am baffled, it starts ok but then it goes wako.
attached are 2 pics, one blades is great and the other shows the inconsistency.
I am Asking you to help please, i am stuck,
i hope you can help me.
thanks

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[handlewanker]

After 8 years I would think a major overhaul is on the cards.
Ian.

[GME]

It sounds like a mechanical problem. I had a similar thing happen to me after 2 years of operation. Turned out to be a loose coupling on my Z axis. When the Z axis went positive, the coupling would slip, which meant Z did not go as high as commanded. Then, when it went negative, it went too far down and cut too deep. I read that Z is going both too high and too low, but I question the first statement. Are you sure it is going too high, and if you are, how do you know? Your DRO should read the amount of commanded movement, but not the actual movement, if there is slipping.

You can check your Z movement with a dial indicator mounted in a holder. Position the indicator with Z in a low position. Zero the indicator and Zero your DRO. Command a +Z movement to near the limit of Z axis travel. Then, command a -Z movement back to Zero. I generally use a G90 command, i.e., G90 Z8 (or whatever distance your machine will handle). Then, G90 Z0. The dial indicator will quantify how much to low the axis moved. If you move the indicator to measure from the top, you can measure quantify the movement in the positive direction. Move Z to near the top limit of travel. Mount the indicator again and zero both the indicator and DRO for Z. G90 Z-8. Then G90 Z0. The indicator will tell you whether the axis makes it back up far enough, or goes too high.

The other thing that comes to mind is your steps per setting. Hard to imagine it getting inadvertently changed, but that is something else to check. If the steps per are set incorrectly, Z can move more or less than expected depending upon whether set for too few or too many steps for your setup.

It's hard to help with diagnostics in the blind. We know nothing about your machine, except you bought it used and it has given years of service. Photos help.

Gary

[faroun]

thanks for the quick responses,

I will preform your suggestions and see if that works,
i hope that works, i will post my results.

thanks

[faroun]

Welll, it was the simplest fix "Turned out to be a loose coupling on my Z axis"
thanks for the help, i will suggest this forum in the future for help.
you guys are the best.

thanks