Lines are staggered when engraving

[SanderLPFRG]

config.g Hi all,
We have recently built our first laser cutter and engraver system, but encountered some issues when engraving.

Regardless of the line height we choose, the engraving lines all seem to start and end with an offset. This is consistent with the movement direction, so it looks to be a result of the laseron delay. Other lasercutters do not have this effect with the same gcode.
is there any way we can solve this??

; Configuration file for RepRapFirmware on Duet 3 Main Board 6XD
; executed by the firmware on start-up
;
; generated by RepRapFirmware Configuration Tool v3.5.0-rc.4+1 on Thu May 02 2024 10:04:56 GMT+0200 (Midden-Europese zomertijd)
 
; General
G90 ; absolute coordinates
M83 ; relative extruder moves
M550 P"Exact" ; set hostname
 
; Network
M551 P"avmom" ; set machine password
M552 P0.0.0.0 S1 ; configure Ethernet adapter
M586 P0 S1 ; configure HTTP
 
; Motor Idle Current Reduction
M906 I30 ; set motor current idle factor
M84 S30 ; set motor current idle timeout
 
; External Drivers
M569 P0.0 S1 R0 T5:5:10:0 ; driver 0.0 goes forwards and requires an active-low enable signal (X axis)
M569 P0.1 S1 R0 T5:5:10:0 ; driver 0.1 goes forwards and requires an active-low enable signal (Y axis)
M569 P0.2 S1 R0 T5:5:10:0 ; driver 0.2 goes forwards and requires an active-low enable signal (Z axis)
 
; Axes
M584 X0.0 Y0.1 Z0.2 ; set axis mapping
M350 X16 Y16 Z16 I0 ; configure microstepping without interpolation
M92 X55.5 Y55.5 Z400 ; configure steps per mm
M208 X-165.3:1700 Y0:1100 Z0:200 ; set minimum and maximum axis limits
M566 X500 Y100 Z12 ; set maximum instantaneous speed changes (mm/min)
M203 X200000 Y50000 Z180 ; set maximum speeds (mm/min)
M201 X4500 Y600 Z20 ; set accelerations (mm/s^2)
M425 X-1.5  S5
; Kinematics
M669 K0 ; configure Cartesian kinematics
 
; Endstops
M574 X1 P"io0.in" S1 ; configure X axis endstop
M574 Y2 P"io1.in" S1 ; configure Y axis endstop
M574 Z0 ; configure Z axis endstop
 
; Lasers
M452 C"vfd" F5000 R255 S0 ; configure Laser port
; emergency stoppel
M950 J2 C"io4.in"
;M581 P2 T6 S1 R0
 
M582 T0
 
M950 P0 C"out_0" ; Air Blaster
M950 P1 C"out_1" ; Succion
M950 P6 C"out_6" ; Define OUT6 as the Red channel
M950 P7 C"out_7" ; Define OUT7 as the Green channel
M950 P8 C"out_8" ; Define OUT8 as the Blue channel
 
; M950 F1 C"out1" ; create fan #0
 
; Miscellaneous
M452 ; select Laser mode

[dc42]

@SanderLPFRG have you checked that there is no backlash in the axis?

[SanderLPFRG]

@dc42 Will check that next, what is an easy way to test? just power on motors and try to move by hand?

[dc42]

@SanderLPFRG in the following I will assume that the engraving was done using back and forth scanning in the X direction, so adjust axis names appropriately if not.

Measure the X offset between adjacent lines in that engraving. Then try jogging the X axis back and forth a distance smaller than that and see if the tool head moves as expected.

Alternatively: construct a GCode file to engrave a short line in the Y direction, then move X a short distance (less than or equal to the offset), then engrave another short Y line, then move X back to the original position and engrave another Y line. Check that the X offset of the middle Y line from the outer two Y lines is the correct amount.

Another possibility is that the tool head is rotating about the Y axis as the belt or leadscrew pulls/pushes it first one way and then the other way. Such a rotation will affect the X position of the laser spot on the workpiece.