all in one dc loss of y home position

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phxvhouse
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all in one dc loss of y home position

Post by phxvhouse »

ruined two parts today.
I did NOT notice faults, nothing out of the ordinary.

in short it seems that my work offset shifted from one position to another.
In the past I have noticed that my control would throw a encoder error, but typically a restart seemed to address the issue
now I am wondering if a larger issue has presented itself

attached zip report

anyone want to take a crack?



better yet can anyone deceiper these reports.. I am afraid attempt anything else until i figure out whats going on


cncsnw
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Re: all in one dc loss of y home position

Post by cncsnw »

There are many possible causes for loss of position. Mechanical slippage somewhere is most likely.

A good starting point for troubleshooting would be to restart the control; home the machine; and mark the motor shaft orientation, ballscrew orientation, and axis position with each axis sitting at home.

Then, if you suspect it has lost position in some way, you can send it back to home using one or more of the following commands at the F3/MDI prompt:

Code: Select all

M91/X
M91/Y
M92/Z
If your marks do not line up where they were before, then something has slipped.
If the marks all line up, but the DRO in Machine Coordinates does not show 0.0000, then you have encoder problems.

See http://www.cncsnw.com/PosLoss.htm for some examples.


CentroidFrog
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Re: all in one dc loss of y home position

Post by CentroidFrog »

I see you're getting non stop MPG1 encoder errors.
Do you have an MPG?
If not you'll want to set P348 to 0 and that should get rid of that error.
Want to post your own question?
Check this out first: http://centroidcncforum.com/viewtopic.php?f=60&t=1043
Acorn CNC tech tips: viewforum.php?f=63


phxvhouse
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Re: all in one dc loss of y home position

Post by phxvhouse »

this popped up at restart..

and of course we have a job that needs finishing.. TODAY
Attachments
20250613_201801.jpg


tblough
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Re: all in one dc loss of y home position

Post by tblough »

That means something has moved on the Y axis. You can hit Y to accept. You will need to re-indicate your part as the machine home position will now be different than it was the previous time the machine was homed.

This adds credence to CNCSNW's idea that something is loose in your drivetrain. It could be as simple as the encoder is loose on the motor shaft, but something is moving.
Cheers,

Tom
Confidence is the feeling you have before you fully understand the situation.
I have CDO. It's like OCD, but the letters are where they should be.


phxvhouse
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Re: all in one dc loss of y home position

Post by phxvhouse »

tom, I have checked the mechanics of the machine, I have swapped x motor with y motor, I checked the encoders, I checked the belts I marked the drive units to make sure nothing was slipping, I dont see abnormalities in the encoder feed to the dro (in other words the dro reacts as it should) however running a part, and attempting to repeat said part results in the same error

i did replace one linear bearing that was making an odd noise, with no change..
the y axis shifts.

short of dissssembling the entire drive system again, what else can I do?


phxvhouse
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Re: all in one dc loss of y home position

Post by phxvhouse »

CentroidFrog wrote: Fri Jun 13, 2025 8:26 am I see you're getting non stop MPG1 encoder errors.
Do you have an MPG?
If not you'll want to set P348 to 0 and that should get rid of that error.
thanks, I do not have a mpg, and i believe you helped me via phone address that issue.


phxvhouse
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Re: all in one dc loss of y home position

Post by phxvhouse »

ok. i just ran a code that moved the y axis back and forth for an hour (y0 to y77) at a feed rate of 333 ipm this resulted in NO noticed change or loss in position.

next I tried code that drills 4 holes, requires the tool to move in x, y and z and ran that code slowly 10 repetitions and noticed zero loss in position

however when I cranked the feedrate override up I noticed that I was losing position on each repitition of position.
accumulated over 20 runs my y position moved close to 1 inch in the (y-) position..

any ideas?


centroid467
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Re: all in one dc loss of y home position

Post by centroid467 »

By crank the feedrate override up do you mean you set it higher than 100% or to 100%?


cncsnw
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Re: all in one dc loss of y home position

Post by cncsnw »

Last month, did you make marks on your motor shafts, pulleys, and ballscrews with the machine at its homed position?

After it lost position, without shutting down and restarting, did you try sending Y back to the home switch using "M91/Y"?

If so, what did the machine-coordinates DRO (Alt-D) say after Y finished the M91/Y move? And did your home marks line up?


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