All working as expected now thankyou.

I think the key change was setting the correct Z height

M208 X305 Y332 Z350 S0 ; 

now;

M208 X305 Y332 Z950 S0 ; 

Full Gcode;

950 ; Configuration file for Duet WiFi (firmware version 3)
; executed by the firmware on start-up
;
; generated by RepRapFirmware Configuration Tool v3.1.4 on Sat Sep 05 2020 23:57:30 GMT+0100 (British Summer Time)

; General preferences
M80					       	; Turns on the ATX power supply
G90                                            	; send absolute coordinates...
M83                                            	; ...but relative extruder moves
M550 P"BLV MGN Cube"                           	; set printer name
M669 K1                                        	; select CoreXY mode

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

; Drives
M569 P0 S0                                     	; physical drive 0 goes backwards
M569 P1 S1                                     	; physical drive 1 goes forwards
M569 P2 S1                                     	; physical drive 2 goes forwards
M569 P3 S0                                     	; physical drive 3 goes backwards
M584 X0 Y1 Z2 E3                               	; set drive mapping
M350 X16 Y16 Z16 E16 I1                        	; configure microstepping with interpolation
M92 X200.00 Y200.00 Z800.00 E415.5             	; set steps per mm
M566 X600.00 Y600.00 Z24.00 E300.00            	; set maximum instantaneous speed changes (mm/min)
M203 X20000.00 Y20000.00 Z600.00 E2000.00      	; set maximum speeds (mm/min)
M201 X3000.00 Y3000.00 Z100.00 E5000.00        	; set accelerations (mm/s^2)
M906 X1500 Y1500 Z1500 E1100 I30               	; set motor currents (mA) and motor idle factor in per cent
M84 S30                                        	; Set idle timeout

; Pressure advance
; M572 D0 S0.05	

; Axis Limits
M208 X-23 Y0 Z0 S1                            	; set axis minima
M208 X305 Y332 Z950 S0                        	; set axis maxima

; Endstops
M564 H0					       	; allow jog without homing
M574 X1 S1 P"xstop"                            	;
M574 Y2 S1 P"ystop"                            	;
M574 Z1 S1 P"zstop"                            	; configure Z-probe endstop for low end on Z

; Z-Probe
M558 P1 H5 C"^zprobe.in" H5 F250 T9000 R0.5	; set Z probe type to switch and the dive height + speeds
G31 P500 X-2 Y-16.4 Z1.40                      	; set Z probe trigger value, offset and trigger height
M557 X10:292 Y5:300 P5                       	; define mesh grid

; Heaters
M308 S0 P"bedtemp" Y"thermistor"T100000 B3950 C0 R4700 A"Bed Temp"  	; configure sensor 0 as thermistor on pin bedtemp
M950 H0 C"bedheat" T0                          				; create bed heater output on bedheat and map it to sensor 0
M140 H0                                        				; map heated bed to heater 0
M143 H0 S100                                   				; set temperature limit for heater 0 to 100C
M307 H0 A466.3 C1262.5 D12.8 S1.00 V24.0 B0    				; Set PID for heated bed values
M308 S1 P"e0temp" Y"thermistor" T100000 B3950 C0 R4700 A"Hotend Temp"   ; configure sensor 1 as thermistor on pin e0temp
M950 H1 C"e0heat" T1                           				; create nozzle heater output on e0heat and map it to sensor 1
M143 H1 S260                              				; set temperature limit for heater 1
M307 H1 A340.0 C140.0 D5.5 S1.00 V24.0 B0     				; Set PID for hotend values

; Fans
M950 F0 C"fan0" Q500                           	; create fan 0 on pin fan0 and set its frequency
M106 P0 S0 H-1                                 	; set fan 0 value. Thermostatic control is turned off
M950 F1 C"fan1" Q500                           	; create fan 1 on pin fan1 and set its frequency
M106 P1 S1 H1 T45                              	; set fan 1 value. Thermostatic control is turned on

; Tools
M563 P0 D0 H1 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

@nick9one1

figured it out - some weirdness with FTP. When I copy the www files to the SD manually it works.

@Phaedrux said in problems with pressure advance calibration:

retract on layer change

Thank you. Yes I have retract on layer change enabled

I've changed the z values you suggested and set the slicer to start the pressure advance at 0.035 in increments to 0.055. Printing now

@phaedrux

update - after making a few changes the hotend is now heating without the error.

The all metal throat is secured by two grub screws to the body/heatsink. Although properly secured, I think the throat was heating up, expanding slightly and making better contact with the heatsink, causing it to dump heat a bit quicker and triggering the error.
I've added some thermal compound to the throat/heatsink, re-tuned and can now heat from cold without any issues.

it was alignment of the Y rails causing the problem. Unless they are perfectly aligned they can bind.

@nick9one1

figured it out - some weirdness with FTP. When I copy the www files to the SD manually it works.

@fcwilt when I've upgraded in the past I've just used the largest zip file (below)

3.3rc1 doesnt seem to have this, so I used the three highlighted files below. uploading In DWC from the System page and clicking the "Upload System Files" button

I didn't think the web interface uploaded correctly (it was still saying 3.2.2 on the system page) so I connected over FTP, deleted everything in the www folder and uploaded the contents of duetwebcontrol.zip.. this is when it stopped working.

First I rolled back to the 3.2.2 webcontrol, but it was the same.
So then I connnected over FTP and replaced the two 3.3rc1 .bin files in the sys folder (Duet2CombinedFirmware.bin DuetWiFiServer.bin) with the original 3.2 files.

now I need to run M997 to install.. this is where it fails

I was on 3.2.2 and have attempted to upgrade to 3.3 rc1 on a duet 2 wifi.

Initially I downloaded the files;

Duet2CombinedFirmware.bin
DuetWiFiServer.bin
DuetWebControl-SD.zip

I used the system interface and uploaded/installed. After rebooting I could see 3.3rc1 was installed but not the web interface. I then realised DuetWebControl-SD.zip needs unzipping and uploading to the www folder.

Aftre doing this and rebooting I can no longer get to the web interface at all. The page name loads but the page is completely blank.

m122 on the lcd shows 3.3rc1

So next I'd try rolling back;
I removed Duet2CombinedFirmware.bin & DuetWiFiServer.bin from sys and replaced with the old version (3.2.2)
the same with the www folder.

When I try to run M997 from the screen, it gives me an error: cant find Duet2CombinedFirmware.bin ? but its definitely there, in the sys folder.

it was alignment of the Y rails causing the problem. Unless they are perfectly aligned they can bind.

@alankilian

Thanks for the suggestion. I'll try that

I've done a little more reasearch and I think its also worth pointing out that on a core XY, moving just one motor moves the head at a 45 degree angle.
So unlike a non core XY, printing a cube square to the bed requires movement by both motors for each line printed.
This means that a problem like this cant be related to skipped steps, loose belts or anything to do with the motion system. If it was, the banding would show on both axes.

It can only really be movement or flex in the hotend assembly or bed.

@peter247 said in banding on one axis:

@nick9one1 The advantage of driving each z motor separate is X axis auto levelling.

yes, but I cant see how that has anything to do with the issue I'm having?

@peter247 ah I understand. the Z steppers are connected to the Z motor 1&2 ports on the duet2 board. I believe this controls them in series?

@peter247 Z is dual MGN12 rails and dual steppers

@phaedrux I've rotated he box 45 degrees and the banding happens on every side - I think this means it isn't skipped steps on a single axis?

this is the printer

and config.g

; Configuration file for Duet WiFi (firmware version 3)
; executed by the firmware on start-up
;
; generated by RepRapFirmware Configuration Tool v3.1.4 on Sat Sep 05 2020 23:57:30 GMT+0100 (British Summer Time)

; General preferences
M80					       	; Turns on the ATX power supply
G90                                            	; send absolute coordinates...
M83                                            	; ...but relative extruder moves
M550 P"MGN Cube"                           	; set printer name
M669 K1                                        	; select CoreXY mode

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

; Drives
M569 P0 S0                                     	; physical drive 0 goes backwards
M569 P1 S1                                     	; physical drive 1 goes forwards
M569 P2 S1                                     	; physical drive 2 goes forwards
M569 P3 S0                                     	; physical drive 3 goes backwards
M584 X0 Y1 Z2 E3                               	; set drive mapping
M350 X16 Y16 Z16 E16 I1                        	; configure microstepping with interpolation
M92 X200.00 Y200.00 Z3200.00 E965.00           	; set steps per mm
M566 X700.00 Y700.00 Z50.00 E150.00             ; set maximum instantaneous speed changes (mm/min)
;M566 X820.00 Y820.00 Z70.00 E300.00			; original
M203 X12000.00 Y12000.00 Z300.00 E2000.00      	; set maximum speeds (mm/min)
M201 X2500.00 Y2500.00 Z150.00 E1500.00        	; set accelerations (mm/s^2)
M906 X1200 Y1200 Z1200 E900 I30               	; set motor currents (mA) and motor idle factor in per cent
M84 S30                                        	; Set idle timeout

; Pressure advance
M572 D0 S0.05

; Axis Limits
M208 X-15:315 Y0:330  Z0 S1                     ; set axis minima

; Endstops
M564 H0					       					; allow jog without homing
M574 X1 S1 P"xstop"                            	;
M574 Y2 S1 P"ystop"                            	;
M574 Z1 S1 P"zstop"                            	; configure Z-probe endstop for low end on Z
M591 D0 P7 C"e0_stop" S0 R50:120 L6.967 E20

; Z-Probe
M950 S0 C"exp.heater3"								
M558 P9 C"^zprobe.in" H2.5 F300 T12000 S0.003 R0.5 B0	; set Z probe type to switch and the dive height + speeds
G31 P500 X50 Y-20 Z2.7                      			; set Z probe trigger value, offset and trigger height (higher no. = closer to bed)
M557 X50:306 Y10:300 P10                       			; define mesh grid

; Heaters
M308 S0 P"bedtemp" Y"thermistor" T100000 B3950 C0 A"Bed Temp" 				; configure sensor 0 as thermistor on pin bedtemp
M950 H0 C"bedheat" T0                          								; create bed heater output on bedheat and map it to sensor 0
M140 H0                                        								; map heated bed to heater 0
M143 H0 S100                                   								; set temperature limit for heater 0 to 100C
M307 H0 R0.291 C1127.4 D26.90 S1.00				 							; Set PID for bed values
M308 S1 P"e0temp" Y"thermistor" T100000 B4725 C7.06e-8 A"Hotend Temp"		; Semtec Thermistor
M950 H1 C"e0heat" T1                           								; create nozzle heater output on e0heat and map it to sensor 1
M143 H1 S280                              									; set temperature limit for heater 1
M307 H1 R2.551 C268.1:175.5 D7.02 S1.00 V23.9								; Set PID for hotend values

; Fans
M950 F0 C"Fan2" Q50                   	     	; create fan 0 on pin 2 and set its frequency
M106 P0 S0 H-1 X204                             ; set fan 0 value. Thermostatic control is turned off
;M950 F0 C"Fan0" Q100                           ; create fan 2 on pin fan2 and set its frequency
;M106 P0 S1 H1 T45                              ; set fan 2 value. Thermostatic control is turned on

; Tools
M563 P0 D0 H1 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

; Screen
M575 P1 B57600 S1

I seem to have bad banding/z wobble (not sure what to call it) on just one axis. The front and back are ugly, but the sides are perfect.
The printer is a core xy with MGN12 rails.

I've PID tuned both bed and hot end a few times (numbers are always very close)
I've stripped the rails cleaned them with IPA and reassembled - zero difference.
Belts aren't loose.
I cant detect any wobble in the bed.

What could be causing this?

I think the banding being on a single axis rules out a few things.. PID tuning (would show on both axis) and belts motors (core xy uses both motors simultaneously so would show on both too?