Anyone know why Reptetier reports different numbers (Z axis specifically) than what the LCD

(Keith Applegarth) #1

Anyone know why Reptetier reports different numbers (Z axis specifically) than what the LCD hooked up to the printer reports?

(Paul Gross) #2

This is just a guess…

Issuing the G-code command G29 (defined as Autolevel on my Printrbot) does not cause Reptetier to reset its z-axis value to zero.

When this happens, whatever z value Reptetier remembered before G29 was executed will still remain, despite the fact that my Printrbot’s extruder is now positioned at z=0.0. There is then an error between the actual machine z position and Reptetier’s z value.

That z-error error will remain when I then start to print.

Issuing commands from Reptetier like G0, G1, G92, G28 etc. do not have the same problem as the G29 command.

(Keith Applegarth) #3

I was resetting my Z offset when I noticed that when I triggered the Z end stop, the LCD value for Z is off from what Repetier says.

(Paul Gross) #4

I am supposing that the printer’s firmware has decided that Z = 0 because the Z endstop was triggered.

If that is actually the case, then you can then force Repetier to use zero for the Z axis with the G92 command like this:

G92 Z0.0

In any case, you can always use G92 from Repetier to force Repetier to agree with whatever value the LCD currently shows.

(Keith Applegarth) #5

I have only noticed it while calculating my Z offset. I bring the print head down to the bed (paper thickness away). Set Z to zero, bring it up. Drop the probe. Go down till it triggers. And the numbers are different?

(Rob Povey) #6

Repetier host is reporting the commanded position, the firmware is reporting the actual position, steppers have fixed resolution, so when you do something like jog down 0.1mm in the host it won’t move exactly 0.1mm.
The error doesn’t accumulate because the host sends absolute position commands to the firmware, and the firmware knows where it actually is, rather than where it was last told to go to.

(Keith Applegarth) #7

So, stick with what the LCD says… got it. And thanks.