Homing axes works OK but positions are wrong

General Discussion
1

Basic Information:

Printer Model: Creality CR3 with Creality direct drive extruder and Bltouch. 4.2.7 MoBo
MCU / Printerboard: Raspberry pi 3B V1.2
klippy.log

When I try to attach klippy.log it won’t save my post, saying I am only allowed 2 attachments. I only had one attachment.

Describe your issue:

Cold start of everything…
issued G28 from Terminal, printer behaved normally, moving to mid-bed and homing with the BlTouch probe.
M114 yields:
Send: M114
Recv: X:117.500 Y:117.500 Z:10.000 E:0.000
Recv: ok

BUT the actual nozzle position is
X=130
Y=115
Z=6

I THINK I have everything in printer.cfg set up correctly.

(This is not my first rodeo, I’ve been compiling and running Marlin on a variety of 3d printers, but this one has me baffled. I did of through all the calibration setups in the manual.)

Walt

2

You may try in the next post. If it too huge, you can zip (compress) it.

3

klippy.log.zip (5.3 KB)

Thanks!

4

When you just home X with G28 X, is the nozzle at the 0 coordinate?
The same for Y?

5

Yes, they each go to 0 after homing. With the direct drive extruder, the nozzle is actually at y=-10. I would compensate for that in the slicer.

6

So actually at the moment with the direct drive extruder and G28 Y the nozzle tip is -10 and not 0, yes?

And it’s not over the bed?

And for X?

7

Thanks for the help :slight_smile:
That’s correct. X is at 0 and is on the bed. Y is off the bed because the direct drive extruder is larger than the stock one. With the Creality firmware I was able to compensate in the slicer, but that doesn’t seem to work now. I may have to do a hardware mod to the limit switch.

I just looked at the limit switch and it will be easy to adjust

What bothers me more is the Z axis. It won’t accept a negative number for the probe location, and my probe is 4.5mm BELOW the nozzle. I followed the calibration routine in the manual, and it seemed to work with the “paper test” but it still “thinks” the nozzle is higher than it physically is.
I’m familiar with setting up BLTouch in the Marlin config files, but the Klipper printer.config seems to work differently.

8

Klipper and BLTouch the offset is never a negative number. A negative number is a nozzle below bed level.
A negative Z probe offset is usually reserved for some sort of nozzle probe ie piezo

9

Thanks. With Marlin a negative probe offset is below the nozzle.
I have the X and Y axes working OK (I moved the Y-zero microswitch).
I gave up on the PROBE_CALIBRATE routine, it would never actually move to zero, so I did it the old-fashioned way:
.
restart
g28
m1 z0
estimate height (use paper as we get close to the right values)
edit printer.cfg, change z_offset in [bltouch]
.
repeat.

Tedious but it’s now working OK… Thanks for the help.

Walt