Laser issue - less "power" when moving in "X"

[Alex.cr]

I am relatively new to the laser world. I am having issues where any line cut in the X axis appears to have less cutting ability then when moving in the Y axis. My hardware is a simple foxalien setup. link

But with a Duet mini5+ as the controller. Currently running 3.4B7 on the unit but have tried the 3.3 release firmware as well. I have also tried 3 different laser modules, I am now using a Neje 15W(laser output). link

The laser is powered off of the 12V power supply and controlled through out6_buff pin.

I original thought this might be due to focus or beam coherence or something like that. The most current Neje laser modules appears to be very coherent and should have plenty of power to cut the acetate plastic I am currently working with. I can easily cut through the plastic with 10% power in one pass at 100mm/min, but only in the Yaxis. The X requires two passes... This is regardless of object shape. When cutting circles any path that mostly moves in Y will cut through just fine but X will not.

Things I have tried:

1. I have removed the laser control cable from the cable chain because I thought it might be noise in the control signal from he steppers. This didn't resolve anything.

2. I have tried forcing the drives into spreadcylce instead of stealthchop. No change.

3. Adjusted the M452 "F" value to try and see if my PWM frequency could be the problem. I have tried values from 200 to 5000. No real change except in the noise the laser module makes. The higher the frequency the lower the noise has been. I have observed that if the frequency is set to something like 200, the noise the laser module itself makes when moving in the X axis is much louder then when moving in Y. It is not the axis making noise but the laser module itself.

The point above makes me think something is causing the PWM frequency from the Duet to the laser to be changing as a function of which axis is moving but that doesn't make any sense to me. I don't have my oscilloscope with me at the moment to test this theory unfortunately.

Anyone ever run into a problem like this before? Or have any other shots in the dark I can try.

Config below:

; Configuration file for Duet 3 Mini 5+ (firmware version 3)
; executed by the firmware on start-up
;
; generated by RepRapFirmware Configuration Tool v3.2.3 on Sat Apr 17 2021 22:22:30 GMT-0400 (Eastern Daylight Time)

; General preferences
G90                                     ; send absolute coordinates...
M83                                     ; ...but relative extruder moves
M550 P"laser"                           ; set printer name
M452   ; select laser mode
;M950 F5 C"out1"                			;GPIO pin for laser module power             
;M106 P5 S1 L1 H-1 C"Laser Control power"


; Network
M552 S1                                 ; enable network
M586 P0 S1                              ; enable HTTP
M586 P1 S0                              ; disable FTP
M586 P2 S0                              ; disable Telnet

M555 P1 ;set Marlin compatability

; Drives
M569 P0.0 S1                            ; physical drive 0.0 goes forwards
M569 P0.1 S0                            ; physical drive 0.1 goes forwards
M569 P0.2 S1                            ; physical drive 0.2 goes forwards
M569 P0.3 S1                            ; physical drive 0.3 goes forwards
;M569 P0.4 S1                            ; physical drive 0.3 goes forwards


M584 X0.0 Y0.1:0.2 Z0.3               ; set drive mapping
M350 X16 Y16 Z16 I1                 ; configure microstepping with interpolation
M92 X80.00 Y80.00 Z400.00        ; set steps per mm
M566 X900.00 Y900.00 Z24.00     ; set maximum instantaneous speed changes (mm/min)
M203 X9000.00 Y9000.00 Z300.0  ; set maximum speeds (mm/min)
M201 X2500.00 Y2500.00 Z200.00      ; set accelerations (mm/s^2)
M906 X800 Y800 Z100  I100            ; set motor currents (mA) and motor idle factor in per cent
M204 P2500 T2500
M84 S30                                 ; Set idle timeout

; Axis Limits
M208 X0 Y0 Z0 S1                        ; set axis minima
M208 X418.0 Y405.0 Z200 S0                  ; set axis maxima

; Endstops
;M574 X2 S1 P"io1.in"                    ; configure active-high endstop for high end on X via pin io1.in
;M574 Y2 S1 P"io2.in"                    ; configure active-high endstop for high end on Y via pin io2.in
M574 X1 S3                                   ; configure sensorless endstop for low end on X
M574 Y1 S4                                   ; configure sensorless endstop for high end on Y
M915 X S3 F0 H200 R0                                  ; set the X axis sensitivity
M915 Y S3 F0 H200 R0                                  ; set the Y axis sensitivity
M574 Z0                               ; configure Z-probe endstop for low end on Z

; Z-Probe
M950 S0 C"io3.out"                      ; create servo pin 0 for BLTouch
M558 P9 C"^io3.in" H5 F120 T6000        ; set Z probe type to bltouch and the dive height + speeds
G31 P500 X0 Y0 Z2.5                     ; set Z probe trigger value, offset and trigger height
M557 X15:215 Y15:195 S20                ; define mesh grid

; Heaters
M140 H-1                                ; disable heated bed (overrides default heater mapping)
M308 S2 P"spi.cs1" Y"rtd-max31865" A"T0" 	; configure sensor 2 as PT100 on SPI
M950 H1 C"out0" T2                                 ; create nozzle heater output on out1 and map it to sensor 2
M307 H1 B0 S1.00                                   ; disable bang-bang mode for the nozzle heater and set PWM limit

; Fans

;lead screw positions
;M671 X-50:350 Y150:150 S20         ; Define Z belts locations (Front_Left, Back_Left, Back_Right, Front_Right)

; Tools
M563 P0 D0 F0                           ; define tool 0
G10 P0 X0 Y0 Z0                         ; set tool 0 axis offsets
G10 P0 R0 S0                            ; set initial tool 0 active and standby temperatures to 0C
M452 C"out6" R255 F1000 S1        ; Enable Laser mode, on out6, with max intensity being 255, and a PWM frequency of 1000
G1 S0 ; make sure laser is off


; Custom settings are not defined

; Miscellaneous
T0                                      ; select first tool
G54
;M564 H0 S0; Allow movement outside of max/min and allow movment without homing
M915 X Y R0 F0; sensorless homing start

[MJLew]

@alex-cr Some lasers have a rectangular shaped spot. I'm not a laser user (yet) but I would imagine that such a spot would give more power to a point on the target while traversing at equal speeds in one direction than the other. Might that be what is going on?

[Alex.cr]

@mjlew

This is what I meant when I mentioned beam coherence above. The beam on my current laser module is square when I point it a a wall several feet away. But yes, that would make sense if the laser was rectangular.

[MJLew]

@alex-cr Square on the wall should be square at the spot, I also would expect.
Beam coherence is not the spot shape, but something to do with the relationship between photon and electrical field phases. I'm not at all an expert, but my impression is that a beam with higher coherence is more 'lasery' than a beam with low coherence. A light beam from a non-laser source can be focussed to any shape spot you like but it will not be coherent.

[Alex.cr]

@mjlew

Makes sense. Looked into this a bit more and it is coined beam shape by some others.

I’m not sure what to do next… I wish I had another controller of some sort to rule out any other issues.

Anyone have any other thoughts on potential fixes?

[engikeneer]

@alex-cr swap the x and y motors & endstops at the board. It will end up flipped, but you'll at least prove its not a controller or motion system issue

[o_lampe]

@alex-cr said in Laser issue - less "power" when moving in "X":

the noise the laser module itself makes when moving in the X axis is much louder then when moving in Y. It is not the axis making noise but the laser module itself.

That would make sense, if the X-driver and out6 would share the same PWM channel. That's indeed hard to believe.
Just for fun, you could use another driver channel for X-motor or change the output pin of the laser.

BTW: I've seen that the same laser module on the NEJE-site is rated 10W. Later in the detailed description they say 15W optical output??
It's also 100$ cheaper than the official NEJE Ama zone shop?!

[dc42]

@alex-cr are you able to rotate the laser 90deg to see if the X and Y axes swap behaviour?

[Alex.cr]

@engikeneer
Thanks for the suggestion. Swapped the drivers and same result.

@o_lampe
Exactly what I was thinking. Didn't make any sense to me. On the seller side, I have double checked and I did purchase this form the NEJE amazon shop for the regular price. But something interesting is going on because now my original link does not link it to the 15W side but rather back to the NEJE store showing 10W output. Now I am really confused.

@dc42 said in Laser issue - less "power" when moving in "X":

@alex-cr are you able to rotate the laser 90deg to see if the X and Y axes swap behaviour?

Rotating the laser showed that it can now cut while moving in X but not in Y.

I can't believe it is in the laser again. This is my 3rd module and they all had the same rough problem. Super frustrating.

Thanks all for the help. Now I really don't know what to do.

[o_lampe]

@alex-cr said in Laser issue - less "power" when moving in "X":

But something interesting is going on because now my original link does not link it to the 15W side but rather back to the NEJE store showing 10W output. Now I am really confused.

In the past, NEJE got lots of negative customer reviews, because they advertised their modules with 40W. They didn't lye, because that's the input power. Now they are rowing back and advertise it with output power. Because of the FAC lens, they could focus the beam even more, so they called it 15W optical power. The bashing never ended, so they started to call it what it is: 10W output power, but 15W optical power from higher density.

@alex-cr said in Laser issue - less "power" when moving in "X":

Rotating the laser showed that it can now cut while moving in X but not in Y.

I can only guess, that their fixed focus isn't adjusted well, so you are using a less optimal module height.
I've seen a simple test video where someone placed a piece of MDF at an angle and lasered along the slope. That way he could find the sweet spot of his module.
If I find the video, I'll post it here. Skip the unboxing and start watching at around 3:00 mins.