Need Help!- creep, unidirectional backlash,not returning to zero

[dumb_luck]

I just finished my cnc router build and i'm having a problem. any help offered would be appreciated.

when I run a program in mach 3 it does not return to zero when the program is finished.
it is loosing steps in both the x and y directions.

I set up a dial gauge and moved the x axis .01 the axis moved about .009 +/_.0005 and when I jog back .01 it moves .01.

if I jog back and forth at .01 steps the dial gauge slowly creeps .001 around for for every jog.

I don't seem to have much back lash and I would assume it would show up both directions.

from what I've read so far this maybe noise in the signal.

I do have my 24v power supply located in the same box as my break outboard. I did try moving it out side the box but I still had the same problem.

any suggestions would be greatly appreciated.

.

[dumb_luck]

just checking

[ssutton]

Need more details about your setup.....control type, breakout board, stepper drives....etc.

Then maybe someone could help.

Scott

[acondit]

Originally Posted by ssutton Need more details about your setup.....control type, breakout board, stepper drives....etc. Then maybe someone could help. Scott

I second Scott's comment. It is possible that electrical noise could come into play. It is also possible that it is just taking more power to drive your axises than you are providing. More info would be helpful in providing help.

Alan

[RomanLini]

Do your stepper motor couplings have a grub screw which is tightened down onto a flat spot on the stepper shaft? Likewise on the couplings to leadscrew shafts?

If you have those couplings that just clamp around a round shaft they are probably slipping.

[louieatienza]

Originally Posted by dumb_luck I just finished my cnc router build and i'm having a problem. any help offered would be appreciated. when I run a program in mach 3 it does not return to zero when the program is finished. it is loosing steps in both the x and y directions. I set up a dial gauge and moved the x axis .01 the axis moved about .009 +/_.0005 and when I jog back .01 it moves .01. if I jog back and forth at .01 steps the dial gauge slowly creeps .001 around for for every jog. I don't seem to have much back lash and I would assume it would show up both directions. from what I've read so far this maybe noise in the signal. I do have my 24v power supply located in the same box as my break outboard. I did try moving it out side the box but I still had the same problem. any suggestions would be greatly appreciated. .

If you keep going back and forth, and you have backlash, then you'll keep creeping away from your indicator, since the backlash is being taken up on the return each time. "Not much backlash" is pretty vague; some may think .005" is not much, othersmay think .001" is intolerable!

You don't mention what kid of drive mechanism you are using (threaded rod, ACME screw, ballscrew, rack & pinion, belt drive)... maybe a pic or two of your machine could help greatly....

[dumb_luck]

Sorry about not providing enough info. I'll try to lay it all out. I was going to do a build thread but just haven't had time to write it up and post it.

I run Mach3 and I have tried using the backlash comp. to no avail.

I would say the backlash is under .001" it actually takes 16 moves before I'm off exactly .010" but it only shows up one direction.

on to the build

Three axis machine approx 48" x 48" x 12"


gantry style layout with

acme rod 1/2 10 5start on the x and y axis


z axis was purchased from k2 cnc


I have dumpster cnc anti backlash nuts


The linkage from motor to rod is direct coupled through a spider with bearing support. I have bearings supporting the rod at both ends and 2 thrust bearings keeping it clamped in place on the motor mount side.





I have not put grub screw through the spider links but everything is very tight and I have not witnessed any slipage here.

The motors are kelig 425 oz bi polar steppers running in parallel bipolar mode

on to the controller


it is a five axis break out board and stepper controller

I have one 24 volt 15a power supply and three 7volt 2.4 amp power supplies running everything.

I do not have shielded cable from the stepper controllers to the motors it is ordered and on the way.

I have checked and rechecked all mechanical connections. Everything is tight and spinning smoothly.

I have tried tuning the motors a variety of ways and tried running everything very slow. NO CHANGE

I have tried changing step and direction pulse timing. NO CHANGE

I have tried mach3 antibacklash compensation with no difference. NO CHANGE

the machine is calibrated to within a .001" meaning if I move it an inch it moves in an inch and returns an inch +/- .0005

I hope that is enough info. If you need any more let me know and I can shoot pictures of any part in particular.

thanks in advance.

[judleroy]

I would think you should use the 24v 15a supply to run all four of your motors.
Judleroy

[Walky]

Did you try swapping axis?

[louieatienza]

Might be that ribbon cable.... nice machine, hope to see your build pix!

[dumb_luck]

Originally Posted by judleroy I would think you should use the 24v 15a supply to run all four of your motors. Judleroy

I do

[dumb_luck]

Originally Posted by louieatienza Might be that ribbon cable.... nice machine, hope to see your build pix!

It is in wall speaker cable for surround sound I had it laying around and looked like it would work nice.

Hope to get build pics up soon.