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Author Topic: How to correct losing steps?  (Read 970 times)

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How to correct losing steps?
« on: November 24, 2019, 04:58:23 PM »
Im going nuts trying to figure this out lol. So my cnc will not maintain its position on the Y axis after running a program. It looks almost as if each pass (on this particular program) is losing around 0.1mm. So after running 40 passes im out about 4mm. When the material is cut it cuts one side narrow, and one side elongated ( as it grows that side slowly). However.. it does not always do it. there are odd occurrences when it runs perfectly (or very close to it) but most times it is constantly losing steps.

Machine - OmioCNC X6-1500 USB.
Currently running on acer aspire laptop with XP installed with standard processor not ACPI.

I have tried 2 different PC's (same result)
swapping stepper motors between x and y (same result)
lowering acceleration and speed (same result)
increasing pulse width and the other option next to that up to 5 (same result)
Swapping cables (same result)
running program with and without load (same result)
Setting Mach3 to have realtime process priority (same result)

I have a few ideas but i cannot test these without spending more money.
try another PC.
try a UPS.
Give up and buy a new machine (which will happen but cannot affords it atm)

Any idea's on what to test or how to fix this issue.

Re: How to correct losing steps?
« Reply #1 on: November 24, 2019, 06:27:54 PM »
Hi,

Quote
I have a few ideas but i cannot test these without spending more money.
try another PC.
try a UPS.

The testing you have done suggests that its not the PC or UPS, nor is it likely to be Mach......how many people use it successfully......and yet
its faulty just for you alone? I suspect the the stepper motor is too small for the task being asked of it.

My recommendation is up-rate the stepper/steppers on that axis.

You are looking for a stepper with more torque but equally important low inductance. What is the make and model of steppers you
have currently?

Craig
My wife left with my best friend...
     and I miss him!
Re: How to correct losing steps?
« Reply #2 on: November 24, 2019, 06:30:28 PM »
I did state it does the same thing under no load. therefore i dont think the stepper is too small for the task being asked of it.
Re: How to correct losing steps?
« Reply #3 on: November 24, 2019, 06:32:48 PM »
57BYGH76-3A/150N.cm is apparently the stepper motors on the machine
Re: How to correct losing steps?
« Reply #4 on: November 24, 2019, 06:33:31 PM »
Hi,
I did read that and still believe the stepper is not up to it.

May I suggest as an experiment that you swap the drive from X to Y and see if the problem changes axis as well, ie a drive fault, or alternately
the fault stays on the original axis ie a stepper fault.

Craig
My wife left with my best friend...
     and I miss him!
Re: How to correct losing steps?
« Reply #5 on: November 24, 2019, 06:34:47 PM »
ah ok - physically swap the drive boards for x and y?
Re: How to correct losing steps?
« Reply #6 on: November 24, 2019, 06:37:11 PM »
Hi,
a Google search on that part number suggests the stepper has 5mH inductance, by no means the worst out there, but
by no means the best either. In a  23/24 size motor you should be looking for 1mH or less if you can but certainly less than 2mH.

Craig
My wife left with my best friend...
     and I miss him!
Re: How to correct losing steps?
« Reply #7 on: November 24, 2019, 06:42:14 PM »
oh ok - motors are something im not very knowledgeable on. I still dont think its the motors as ive seen people carve up aluminum with that same machine no dramas. i will investigate swapping the drive boards over and see what happens from there./ thanks

Offline RICH

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Re: How to correct losing steps?
« Reply #8 on: November 25, 2019, 05:10:10 AM »

1. Confirm your steps per unit using the axis calibration of MACH3.
2. How much backlash do you have in the axis?

Post your xml file that you are using.
Post the code that you are running.

RICH
Re: How to correct losing steps?
« Reply #9 on: November 25, 2019, 05:15:54 AM »
OK... so i opened up the box, swapped the X and the Y cards over and the connections etc. Plugged it all back up. Ran the same program again. Returns to zero. ran it again twice more... returns to zero.

i will do a longer run tomorrow. but could have unplugging the cards done anything. like reset the chips or something?