* resolved * Z axis not returning to zero

[rsv4dave]

Hello,

Started the mill today. No problems since day one. But today the X axis is not returning to zero.
I can reset zero, and the X axis will travel to the exact dimension entered, but will return short of zero.
The more times I travel, the worse it gets.

Retrofit Kit for Boss 1-7 = CNC Mill V 2.36 Servos have the blue cap.
System ID 0220081506

Help !!!

Thanks in advance

Dave

[Centroid_Liviu]

Can you please generate a report and email to tech@ajaxcnc.com, from the Main Menu press F7-Utilities, F-7 Report. We just need the report.zip that is generated.

[rsv4dave]

Hi Thanks for coming back so quick.

I have just tried the F7 / F7 but get a " Error occured while copying files " screen message.

Dave

[rsv4dave]

Hi,
I have just sent an email to tech dept.

I have created the zip file but we can't open it due to all our PCs not seeing the Compact Flash card.

The PC used to drive the mill uses only the Compaact Flash drive. " No Windows system "

Dave

[Centroid_Liviu]

Do you have USB on the machine used for the MIll? If you do, copy the file over to a USB thumb drive. Then put the thumb drive in a Windows machine and take the file from there.

[rsv4dave]

Hi,

There are USB ports but because the PC is bare bones they are not connected.

I've now finished for the day 18:00 approx here in the UK.

I will have a look tomorrow to see if I can connect the USBs

Any thoughts on the possible problem Z not returning ?
I can zero and move the Z axis 350mm and it measures exact.
We thought it could be the encoder, but that would give false dimensions all the time. Right or Wrong.

Both Y and Z are fine

I will check to see if any thoughts arrive during the evening.

Thanks for you help

[cncsnw]

Is your problem with the Z axis, or with the X axis?

It is not uncommon for an encoder failure, or perhaps an encoder cable/connection failure, to drop counts primarily in one direction. This would result in a progressive "drift" to one end as you do a series of programmed back-and-forth moves between the same set of coordinates.

Assuming that you have limit/home switches on your machine, and you use those switches for homing (I know, this is not a safe assumption on Ajax systems...) then you can check for dropped encoder counts by repeating the homing move in MDI and looking at the resulting position in Machine Coordinates.

1. Press Alt-D to switch your DRO to Machine Coordinates
2. Re-run the homing move (e.g. "M92/Z" or "M91/X" or whatever M91 or M92 code might appear in your cnc10m.hom macro) at the F3/MDI prompt.

Do not re-run the M26 command, which re-zeroes the axis there.

After the M91 or M92 completes, then your DRO position should either be 0.000 or it should be some whole number of motor turns. If instead it is off by some fractional number of motor turns, then your encoder has dropped counts.

[rsv4dave]

Thanks cncsnw,

I had to finish a job off this morning and will try what you say on Monday.

I have noticed that it is the Z minus that gives the fault.

If I Zero then go to a Z plus dimension no problem, Zero and go a minus dimension incorrect.

Dave

[rsv4dave]

Hi all,

This morning I have swapped encoders from the Z and X axis and the fault is still there.
I have also retrieved the zip which I just sending to the tech team.

Thanks for your help AjaxCNC

Dave

[Aftershock]

I had a problem once where the shaft the encoder was mounted to came loose from the rest of the servo motor shaft. It would tend to drift negative since the slip occurred mostly on rapids and there tend to be more rapids up than down.