Cuts not repeatable, I'm losing steps

All things related to the Centroid Acorn CNC Controller

Moderator: cnckeith

lavrgs
Posts: 186
Joined: Sat Aug 11, 2018 11:22 pm
Acorn CNC Controller: Yes
Allin1DC CNC Controller: No
Oak CNC controller: No
MPU11 & GPIO4D -w/ 3rd Party Drives: No
DC3IOB: No
CNC12: Yes
CNC11: No
CPU10 or CPU7: No
CNC Control System Serial Number: none
Location: Oregon

Re: Cuts not repeatable < overall turns ratio >>>not the problem, I'm losing steps

Post by lavrgs »

I tried to be as diligent as possible and follow what I thought was reasonable advise from the forum like "make sure you use the DMM cables" , although at the other end there is the "don't follow the DMM schematics all those contactors aren't necessary" So I used the DMM cables and ignored the advise not to follow DMM schematics. I end up in a situation that can't make precision parts. I did not run into any threads discussing differential line drivers but I willing to learn. A couple posts up is a picture of the Centroid schematics the says DO NOT CONNECT H6 to DYN4 DRIVE and I followed that advice.

KENTONSJ it appears you have created your own board for your build - nice job!!! Is this something you sell or is it a one off? I am not an electrical engineer so the subject of differential line drivers is beyond my current scope. Any info /resources you could point me to would be appreciated.
suntravel
Posts: 132
Joined: Thu Sep 23, 2021 3:49 pm
Acorn CNC Controller: Yes
Allin1DC CNC Controller: No
Oak CNC controller: No
MPU11 & GPIO4D -w/ 3rd Party Drives: No
DC3IOB: No
CNC12: Yes
CNC11: No
CPU10 or CPU7: No
CNC Control System Serial Number: 6433DB0446C1-08115074
Location: Germany

Re: Cuts not repeatable < overall turns ratio >>>not the problem, I'm losing steps

Post by suntravel »

lavrgs wrote: Thu Jan 06, 2022 6:08 pm I end up in a situation that can't make precision parts.
Thought about to discard the servos and switch to easy to handle closed loop steppers?

Uwe
kentonsj
Posts: 43
Joined: Wed Apr 18, 2018 3:31 pm
Acorn CNC Controller: Yes
Allin1DC CNC Controller: No
Oak CNC controller: No
MPU11 & GPIO4D -w/ 3rd Party Drives: No
DC3IOB: No
CNC11: No
CPU10 or CPU7: No
CNC Control System Serial Number: 38D2694DE4D2-0423180849
Location: SK, Canada

Re: Cuts not repeatable < overall turns ratio >>>not the problem, I'm losing steps

Post by kentonsj »

lavrgs wrote: Thu Jan 06, 2022 6:08 pm KENTONSJ it appears you have created your own board for your build - nice job!!! Is this something you sell or is it a one off? I am not an electrical engineer so the subject of differential line drivers is beyond my current scope. Any info /resources you could point me to would be appreciated.
It is something I'm willing to sell. I have had a few requests and I wanted to do some testing first to make sure my board would work reliably. If I was near you, I'd let you give one a try and see if it helps your lost step problems. DM if you'd like to discuss further.
cnckeith
Posts: 3868
Joined: Wed Mar 03, 2010 4:23 pm
Acorn CNC Controller: Yes
Allin1DC CNC Controller: Yes
Oak CNC controller: Yes
MPU11 & GPIO4D -w/ 3rd Party Drives: Yes
DC3IOB: Yes
CNC11: Yes
CPU10 or CPU7: Yes
CNC Control System Serial Number: none
Contact:

Re: Cuts not repeatable < overall turns ratio >>>not the problem, I'm losing steps

Post by cnckeith »

lavrgs wrote: Thu Jan 06, 2022 2:19 pm I had a discussion with DMM and they relayed to me that "sometimes" Acorn boards do not work with their cables" and that it was an Acorn problem and that getting a new board solves the problem. What is the deal? Will I be able to use the DMM Cables do I return them and build my own ...? will I ever get to a point where I have a reliable accurate machine?
I was able to go in to create a report .However please note that the machine is not set up per my final desired config. For example there is no Z axis set up due to drive failure.
REPORThttps://drive.google.com/file/d/1GfhivO ... sp=sharing
this is the way we have wired them up with good results.
https://www.centroidcnc.com/dealersuppo ... 969.r6.pdf

the cables they sent us seemed to make no sense with resistors in odd places that were not doing anything. they never sent us any updated cables so i have no idea what they are shipping now so therefore i can't recommend using them. we made our own cable as seen in the schematic S14969.r6.pdf
a cable with good shielding/drain and twisted pair for the cable.
Need support? READ THIS POST first. http://centroidcncforum.com/viewtopic.php?f=60&t=1043
All Acorn Documentation is located here: viewtopic.php?f=60&t=3397
Answers to common questions: viewforum.php?f=63
and here viewforum.php?f=61
Gear we use but don't sell. https://www.centroidcnc.com/centroid_di ... _gear.html
cnckeith
Posts: 3868
Joined: Wed Mar 03, 2010 4:23 pm
Acorn CNC Controller: Yes
Allin1DC CNC Controller: Yes
Oak CNC controller: Yes
MPU11 & GPIO4D -w/ 3rd Party Drives: Yes
DC3IOB: Yes
CNC11: Yes
CPU10 or CPU7: Yes
CNC Control System Serial Number: none
Contact:

Re: Cuts not repeatable, I'm losing steps

Post by cnckeith »

and related diagnosis procedure i use.

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 turn 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
Need support? READ THIS POST first. http://centroidcncforum.com/viewtopic.php?f=60&t=1043
All Acorn Documentation is located here: viewtopic.php?f=60&t=3397
Answers to common questions: viewforum.php?f=63
and here viewforum.php?f=61
Gear we use but don't sell. https://www.centroidcnc.com/centroid_di ... _gear.html
slodat
Posts: 682
Joined: Thu Apr 12, 2018 11:16 pm
Acorn CNC Controller: Yes
Allin1DC CNC Controller: No
Oak CNC controller: No
MPU11 & GPIO4D -w/ 3rd Party Drives: No
DC3IOB: No
CNC11: No
CPU10 or CPU7: No
CNC Control System Serial Number: none

Re: Cuts not repeatable, I'm losing steps

Post by slodat »

If you are using the cables DMM supplies, in my experience, you will absolutely lose steps. I have had this problem on multiple systems. Wiring the DYN4 drives to the DB25 step and direction outputs solved this for me. I used the DMMRV software to get encoder position, moved the axis, the moved back to start position and checked encoder position again. I have a couple threads on here detailing my findings. For whatever their reasons, DMM is still selling the same cables. Once I made the change I've described my machines have been rock solid.
lavrgs
Posts: 186
Joined: Sat Aug 11, 2018 11:22 pm
Acorn CNC Controller: Yes
Allin1DC CNC Controller: No
Oak CNC controller: No
MPU11 & GPIO4D -w/ 3rd Party Drives: No
DC3IOB: No
CNC12: Yes
CNC11: No
CPU10 or CPU7: No
CNC Control System Serial Number: none
Location: Oregon

Re: Cuts not repeatable < overall turns ratio >>>not the problem, I'm losing steps

Post by lavrgs »

cnckeith wrote: Thu Jan 06, 2022 6:59 pm this is the way we have wired them up with good results.
https://www.centroidcnc.com/dealersuppo ... 969.r6.pdf This is similar to what DMM just Sent me. It was not part of the docs I downloaded from Centroid

the cables they sent us seemed to make no sense with resistors in odd places that were not doing anything. they never sent us any updated cables so i have no idea what they are shipping now so therefore i can't recommend using them. we made our own cable as seen in the schematic S14969.r6.pdf
a cable with good shielding/drain and twisted pair for the cable. Do you have a suggested cable? The ones I have are not twisted pair. Would a CAT5 style work - it's all I have currently and the cable I ordered are just 7 conductor shielded cable
Thanks Keith it sounds like there should be some updates to videos that recommend ONLY using DMM cables....
What about the response above suggesting line drivers?
My issue is I don't understand why the 5V line in S14969 makes such a difference, I will go with it but my understanding was that the resistor in the DMM cable brought 24V down to 5V - I may be wrong, it happened once before. Is this NOT a noise issue?
slodat
Posts: 682
Joined: Thu Apr 12, 2018 11:16 pm
Acorn CNC Controller: Yes
Allin1DC CNC Controller: No
Oak CNC controller: No
MPU11 & GPIO4D -w/ 3rd Party Drives: No
DC3IOB: No
CNC11: No
CPU10 or CPU7: No
CNC Control System Serial Number: none

Re: Cuts not repeatable, I'm losing steps

Post by slodat »

This is SO frustrating. This same schematic keeps getting pushed and it simply does not work reliably. A lot of us did extensive testing and provided real data demonstrating that the DYN4 drives lose steps when on the screw terminal outputs.

Do what you want... If you want it to work without a bunch of hassle, connect the DYN4 step and direction to the DB25 output on the Acorn...

This is the cable I use: Amphenol CS-DSPMDB25MM-010 25-Pin DB25 Premium D-Sub Cable. I cut it in half and made two DYN4 -> Acorn cables with it.

Edited to add.. it looks like the schematic above is different than when I looked last. And, the +5vdc makes sense.. Nonetheless, using DMM's cable with +24vdc applied across a resistor to drop to 5vdc was an issue in the past for me.
Last edited by slodat on Thu Jan 06, 2022 8:07 pm, edited 1 time in total.
lavrgs
Posts: 186
Joined: Sat Aug 11, 2018 11:22 pm
Acorn CNC Controller: Yes
Allin1DC CNC Controller: No
Oak CNC controller: No
MPU11 & GPIO4D -w/ 3rd Party Drives: No
DC3IOB: No
CNC12: Yes
CNC11: No
CPU10 or CPU7: No
CNC Control System Serial Number: none
Location: Oregon

Re: Cuts not repeatable < overall turns ratio >>>not the problem, I'm losing steps

Post by lavrgs »

suntravel wrote: Thu Jan 06, 2022 6:23 pm
lavrgs wrote: Thu Jan 06, 2022 6:08 pm I end up in a situation that can't make precision parts.
Thought about to discard the servos and switch to easy to handle closed loop steppers?

Uwe
inappropriate ill timed
lavrgs
Posts: 186
Joined: Sat Aug 11, 2018 11:22 pm
Acorn CNC Controller: Yes
Allin1DC CNC Controller: No
Oak CNC controller: No
MPU11 & GPIO4D -w/ 3rd Party Drives: No
DC3IOB: No
CNC12: Yes
CNC11: No
CPU10 or CPU7: No
CNC Control System Serial Number: none
Location: Oregon

Re: Cuts not repeatable, I'm losing steps

Post by lavrgs »

slodat wrote: Thu Jan 06, 2022 7:57 pm This is SO frustrating. This same schematic keeps getting pushed and it simply does not work reliably. A lot of us did extensive testing and provided real data demonstrating that the DYN4 drives lose steps when on the screw terminal outputs.

Do what you want... If you want it to work without a bunch of hassle, connect the DYN4 step and direction to the DB25 output on the Acorn...

This is the cable I use: Amphenol CS-DSPMDB25MM-010 25-Pin DB25 Premium D-Sub Cable. I cut it in half and made two DYN4 -> Acorn cables with it. Are you still using the screw terminals or going to the Acorn DB25?
SLODAT I've read that you've been through this a couple of times and I appreciate you chiming in. I'm a bit frustrated because when I started this thread I did not understand I was losing steps and the advice I got made improvements - I felt like I was on the right track, but I was only into the first layer of the onion.
I have talked to DMM several times and find they are more focused than this forum - not a slight on the forum but...
Last edited by lavrgs on Thu Jan 06, 2022 8:30 pm, edited 1 time in total.
Post Reply