# Wrong Z start point after one shape is done

In this project, after cutting the lower shape (not all the way), the next shape starts about 2 mm on top of the material.

I don’t know what’s going on. I have checked my bit, it’s ok and it’s tight. It’s a 2mm bit, inside a collet adapter with a collet of 6mm.

The first shape seems to be cut but not all the way trough. But I have no slopes or something indicating that it starts slowly shifting towards the wrong height.

And I have adjusted my Z starting point with precision (I slide a very thin paper and once I can not move it, I set the zero for that).

I also tried to adjust the potentiometer of the Z axis, and it seems fine but I don’t know how to know for sure that it is the right height.

2 weeks ago, when I last used the machine, I had no issues.

Do anyone have any idea of what is going on?

Thanks!

The Z-axis potentiometers govern voltage reference (that in order regulate current limit of driver) and do not affect travel (step/mm value, GRBL parameter \$102 do that)

Hi! Thanks. I kinda knew that. But I also read that wrong potentiometer/current settings can provoque missed steps, right?

what steps do you suggest to follow To adjust that value (\$120) correctly?
Any idea why it could have shifted?

Absolutely, too low and you´ll loose step due to lack if sufficient torque, and if too high the stepper driver will overheat and shut down to prevent damage (shutdown can be brief). When its shut down it wil just ignore any step command = lost steps.

\$120 is the acceleration parameter for the X axis.
\$102 is Z step/mm

Yes. Sorry, I meant \$102.

This are my current values, are they ok for the 1000mm xcarve? How should I know what to change in order to achieve the optimal \$102 value? Thanks!

• \$132=100.000 (z max travel, mm)
• \$131=750.000 (y max travel, mm)
• \$130=750.000 (x max travel, mm)
• \$122=50.000 (z accel, mm/sec^2)
• \$121=500.000 (y accel, mm/sec^2)
• \$120=500.000 (x accel, mm/sec^2)
• \$112=500.000 (z max rate, mm/min)
• \$111=8000.000 (y max rate, mm/min)
• \$110=8000.000 (x max rate, mm/min)
• \$102=188.976 (z, step/mm)
• \$101=40.000 (y, step/mm)
• \$100=40.000 (x, step/mm)
• \$27=1.000 (homing pull-off, mm)
• \$26=250 (homing debounce, msec)
• \$25=750.000 (homing seek, mm/min)
• \$24=25.000 (homing feed, mm/min)
• \$23=3 (homing dir invert mask:00000011)
• \$22=0 (homing cycle, bool)
• \$21=0 (hard limits, bool)
• \$20=0 (soft limits, bool)
• \$13=0 (report inches, bool)
• \$12=0.002 (arc tolerance, mm)
• \$11=0.020 (junction deviation, mm)
• \$6=0 (probe pin invert, bool)
• \$5=0 (limit pins invert, bool)
• \$4=0 (step enable invert, bool)
• \$3=3 (dir port invert mask:00000011)
• \$2=0 (step port invert mask:00000000)
• \$1=255 (step idle delay, msec)

Nevermind. I ended joggling and measuring and calibrating and arrive at the conclusion of that I need to set \$102=189.650 (z, step/mm)

I havent run a test carve yet, but I suposse it will work.

My only question is: Will this settings be saved in the arduino memory or in easel? Can they be “overwritten somehow”? Or once I set them, If I only use easel, they will remain?

Thanks,

They are stored on the controller (Arduino) and are persistent.