Loosing Position

[DLAM]

All,

I am at a loss. I have a Acorn controlled lathe running CNC12 V4.50. I have started loosing position on the Z Axis only. I have been running some parts and was able to run about 15 of them with no problem (machine has been producing good parts for some time). All of a sudden it started loosing position in Z Axis only. X is tracking fine with no problem. The Z axis seems like it is loosing steps and can be off as much as .060". I pulled the back of the machine off and do not see any problems with the mechanical connection of the servo to the ball screw or anything else. This a Emcoturn Machine that was converted to Centroid control so the rigidity is there. I tried shutting down CNC12 and restarting the software (machine has been up for a little while) and it is still present
I tried searching the forum but could not find any issue withe the same symptoms. Any assistance is greatly appreciated. The machine has DYN4 Servos running Step/Dir off the Acorn board. I Feel this type problem could go in a lot of different directions and to make sure I reach out the experts before I say "this" is the problem and replacing or doing things that is not faulty. Attached is the report.

Thank You

[lavrgs]

I'm having a similar problem with DYN4 drives. Are you using the DMM supplied cable? I spent a lot of time checking my axes by using the DMMDRV app and found my axes are losing steps. When I move one rev with the DMMDRV program I am able to return to zero from 65537, but when I use acorn to run a program that moves any axes back and forth I end up being close to a full rotation off.
Read through this thread to see if you are experiencing similar issues https://centroidcncforum.com/viewtopic. ... ing#p57905
I assume you have the cable to connect the DMM drives to your computer and have the latest DMMDRV app. If not it you should get the cable and the app downloaded.

[DLAM]

I initially had the Cables supplied by DMM, but replaced them during initial testing when I did the conversion.

[lavrgs]

Have you called DMM? Unfortunately solutions from this forum are not readily forthcoming...if it appears to be a DMM issue.

[cnckeith]

pull the axis motor that is having issues. mark the shaft. zero the DRO position at the mark. run a test program. (typically moving large distance and then back to zero at different rates) does the motor return lined up with the mark when program is done?

if yes, then edit the test program to tun on and off the spindle and any other accessories you have connected to the cnc controller, run the test again. if you lose steps with this test it is related to noise. make sure to have quencharcs on all contactors and solenoids, reevaluate the wiring practices for grounding and shielding.

if no, then the lost steps is related to that axis, swap the drive wiring on the acorn to another axis and run same test. does it follow the move? i.e. does it still not return to the mark while using another axis? if yes, then you have isolated the cause of the issue to the motor/drive/cabling. replace cabling/drive/motor to further isolate the issue.

if the motor/drive passes all the tests above check the mechanicals, loose pulleys and couplers that move during a rapid but will hold just fine during feedrate moves are common issue that mimic lost steps. use sleeving locktite on problem pulleys/couplers like this. i use 620 found at the bottom of this page. https://www.centroidcnc.com/centroid_di ... _gear.html