accuracy issues over x axis

[streetrodlover]

Ok I am all out of ideas to test and looking for some more, I usually make more decorative stuff, but now have a project where all the parts need to fit together pretty accurately. I am sure I have had this problem since the beginning, it just has not bothered me much until now. I have parts 21.5" cutting on a 4'x4' table the right side of the table is cutting pretty much spot on but left side is cutting a 1/16" short. I have tested on .75 and .5 material, doubling the number of passes to see if backlash error was doubled, and I had the same error.

I have verified nothing is loose, nothing is binding, pinions show more wear than I would expect, but I really don't think it is a backlash issue (left side is cut first then the right, if backlash was the problem wouldn't it be more of a problem at the end of the program?). I have swapped drives, and changed my cable connectors (they were molex and were getting hot on the x and z, which means there was more resistance causing heat build up). For fun I have changed steps per to see if the error got smaller or larger and the error did not seem to change mine is calibrated over 45". I have tried mach3 and uccnc and it is the same, I remember one of the first projects I did was an end table and remember also being a 1/16th off but it went together, so I didn't worry about it much. I have not swapped motors yet, that was still on my list, and I was coming here to see if anyone else had some other tests I could make to start eliminating or verifying issues.

Electronics:
Leadshine M542 drivers
Nema 23 381 ozin motors https://www.automationtechnologiesinc.com/products-page/nema-23/nema23-381ozin-3-5a-single-shaft-stepper-motor-kl23h2100-35-4a/
UC100 (using UCCNC now with Gerry's screenset)
C35S BOB
Hitachi M12VC with Super PID (manually controlled not PC controlled)

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[ger21]

Backlash is not cumulative, so it wouldn't increase over time. 1/16" error is not due to backlash.

After homing the machine, put some registration marks on the pinion. At the end of the run, go back to the home position (do NOT home the machine this time), and see if the marks still line up.

[streetrodlover]

Backlash is not cumulative, so it wouldn't increase over time. 1/16" error is not due to backlash.

After homing the machine, put some registration marks on the pinion. At the end of the run, go back to the home position (do NOT home the machine this time), and see if the marks still line up.

Ok I will try that tonight when I get home

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[difalkner]

Are the parts supposed to be 21.5" square, Justin?

David

[streetrodlover]

Backlash is not cumulative, so it wouldn't increase over time. 1/16" error is not due to backlash.

After homing the machine, put some registration marks on the pinion. At the end of the run, go back to the home position (do NOT home the machine this time), and see if the marks still line up.

I have ran it twice just to make sure. Pinion marks and belt marks line up perfectly.

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[streetrodlover]

Are the parts supposed to be 21.5" square, Justin?

David

No they are varying lengths, for testing tho I'm just cutting 3x21.5

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[ger21]

Are your steps/unit the same on both the master and slave axis?

[streetrodlover]

Are your steps/unit the same on both the master and slave axis?

Sorry should of been more clear my X is across the gantry my Y and A are slaved. No issues with Y or A just the X.

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[davy182]

attach a dial indicator to the x axis and zero it on the right side to the rack for the x axis. I bet you are out on the one side you are consistent short on.

[ger21]

Are you saying that when the gantry is at one end of the machine, The Z carriage move one distance, and when the gantry is at the other end, it moves a different distance?

[davy182]

Yes, if there is more slop in between the rack and pinion on one side versus tight on the other the distance travel on the slop side is going to be different that distances on the tighter side, therefore one side of the x cutting shorter than on the other side. Right.

[davy182]

So the test would be on the side that is having issues the x axis should be able to move noticeably before stepper resists.

[streetrodlover]

attach a dial indicator to the x axis and zero it on the right side to the rack for the x axis. I bet you are out on the one side you are consistent short on.

I'm not following exactly how you want me to test with the indicator. Could you elaborate more please?

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[streetrodlover]

Are you saying that when the gantry is at one end of the machine, The Z carriage move one distance, and when the gantry is at the other end, it moves a different distance?

Basically yes I can cut two pieces on each side of the machine that are the same width and on the left side it is consistently short to the right side



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[ger21]

Is there maybe something mechanical that's stopping movement?

[streetrodlover]

I have manually moved the carriage with pinion engaged and disengaged to see if anything was catching or binding and did not find anything, honestly it doesn't make sense to me, I can pretty much bet on something mechanical. The error seems consistent regardless of software settings, the common denominator is the rack or pinion, teeth all look fine, backlash is very minimal. Could be slop in rack, I'm just not sure how to test. I could swap racks with A or Y and see if the problem moves to a different axis.

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[difalkner]

Is the error always about 1/16" or is it proportional to the length being cut?

David

[streetrodlover]

From my tests they were all about 1/16th this weekend I'll have more time to test and I will run different size tool paths to see if the error is always the same or changes

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[ger21]

Loose setscrews on the pinion or pulleys, would do what you are seeing.

[streetrodlover]

Loose setscrews on the pinion or pulleys, would do what you are seeing.

Yup first thing I checked, also remember I'm pretty certain this isn't a new problem I believe it has been off from the start, I just don't usually cut anything that needs to be all that accurate. Every bolt/set screw on this machine has loctite or a lock nut. Those set screws are just as tight as the day they were put on

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