Y Axis Overrunning

So thought I had everything working nicely till I started a large project where measurements needed to be on point. When I tried to do a large square, like 20inx20in the X mesurements are fine but the Y axis run over a quarter to half of an inch on either side. First let me point out the following

  • Everything has been checked twice and tightened (belts, nuts, etc…)
  • Spindle is a new Dewalt 611
  • Machine is perfectly squared in every angle
  • All pots on the Gshield have been adjusted

is there anything else i’m missing?


Hey Brian, you can go UGS, type $$ on Command line and tell me what is your number on $101 =


You can play with that number up and down until you find exact measurement.

I may have to try that, weird for it to be off so much though

On the UGS, simply click on settings, firmware setting then find line $101, double click on the number you want to change and enter new number. I did for mine. You have to reset all zero somewhere frond middle, put ruler, lower your bit (either engraving or V bit with pin point.) while it’s on zero on the ruler, give command Y20, it goes all the way to 20 point. Check ruler, if it is longer, you have to decrease $101 number.


weird for it to be off so much though

Yes, that’s really odd. If it’s really the calibration that’s off the error should be the same in both directions. So, when you move left to right and it’s off by 1/2 inch then when you move it right to left the same distance you should return to the same place you started.

Can you post the $$ output?

Here they are.

Ok, thanks.

Everything looks normal there. I wanted to check that $1 was set correctly as that could have caused the problem you are seeing.

I would say that something else is causing the problem OP is seeing. With $100=40.00 and $101=40.00 then there has to be something else giving extra steps on the Y axis.

You’re correct, might be something different. Like Math translation on Arduino firmware, characteristics of stepper, vb. But one thing sure is not loosing step, that is the good sign to have healthy stepper. I say just trick the numbers, get rid off it. If you dig it I’m sure you’ll find zillion posibilities. I always keep it simple, I’m always winner with no headache. The other word is “LAZY”. :slight_smile:

On a standard machine what does that 40 mean. 40 steps per inch? 40 steps per MM? Also OP says over run varies between 1/4" and 1/2" so it appears to not be a constant amount of error.

Here is my configuration, please check line $101=
If it make sense, I’m running this machine for long enough with these numbers, have no problems and my accuracy is perfect. Also if you take a look at more carefully, your answer is on the screen, it is 40 steps per mm. Mechanical world works on metric system. Applications Just translate to inch for you.


$0=10 (step pulse, usec)
$1=255 (step idle delay, msec)
$2=0 (step port invert mask:00000000)
$3=3 (dir port invert mask:00000011)
$4=0 (step enable invert, bool)
$5=0 (limit pins invert, bool)
$6=0 (probe pin invert, bool)
$10=3 (status report mask:00000011)
$11=0.050 (junction deviation, mm)
$12=0.002 (arc tolerance, mm)
$13=0 (report inches, bool)
$20=0 (soft limits, bool)
$21=0 (hard limits, bool)
$22=1 (homing cycle, bool)
$23=3 (homing dir invert mask:00000011)
$24=25.000 (homing feed, mm/min)
$25=750.000 (homing seek, mm/min)
$26=250 (homing debounce, msec)
$27=1.000 (homing pull-off, mm)
$100=40.000 (x, step/mm)
$101=38.012 (y, step/mm)
$102=188.900 (z, step/mm)
$110=8000.000 (x max rate, mm/min)
$111=8000.000 (y max rate, mm/min)
$112=500.000 (z max rate, mm/min)
$120=500.000 (x accel, mm/sec^2)
$121=500.000 (y accel, mm/sec^2)
$122=50.000 (z accel, mm/sec^2)
$130=790.000 (x max travel, mm)
$131=790.000 (y max travel, mm)
$132=100.000 (z max travel, mm)

Thanks This old man can’t see the forest for the trees some times. :frowning:

I didn’t mean that David, you know that. Just don’t confuse/scare kids. I always respect your knowledge.

You were correct. I did not even see the mm per step note.