Speed limit stuck at 4000 mm / min?

[thomas.weiss]

Hey,

I built a small CNC with a 150x130 mm working area based on the Duet 3 Mini 5+ about a year ago. Back then, i limited the maximum speeds to 4000 mm/min using the M203 command in the config.g file.

For a different application, I would like to increase it to 6000 mm / min. I changed the config (M203) to allow the higher speeds. For some reason though, a GCODE file with F4000 looks the same as F6000 while being processed by the machine. I can't spot a difference.

I am using Nema17 motors with 200 steps/rev and a maximum current of 2500 mA. Is there anything else in some other file or setting that could still be limiting the maximum speed?

This should be the relevant part from the config file.

M569 P0.0 S1 D3                  ; physical drive 0.0 goes forwards
M569 P0.1 S1 D3                  ; physical drive 0.1 goes forwards
M569 P0.2 S0 D3                  ; physical drive 0.2 goes backwards
M569 P0.3 S0 D3                  ; physical drive 0.3 goes backwards
M584 X0.1 Y0.2:0.3 Z0.0          ; set drive mapping
M350 X16 Y16 Z16 I1              ; configure microstepping with interpolation
M92 X656.168 Y656.168 Z1007.874  ; set steps per mm
M566 X1000.00 Y1000.00 Z800.00   ; set maximum instantaneous speed changes (mm/min)
M203 X6000.00 Y6000.00 Z4000.00  ; set maximum speeds (mm/min)
M201 X200.00 Y200.00 Z200.00     ; set accelerations (mm/s^2)
M906 X2000 Y2000 Z1100           ; set motor currents (mA) and motor idle factor in per cent

Any idea what it is that is still limiting the motor speeds? - They aren't losing steps.

Thank you so much!

Here is the full config if needed:

; Configuration file for Duet 3 Mini 5+ (firmware version 3.3)
; executed by the firmware on start-up
; generated by RepRapFirmware Configuration Tool v3.3.5 on Wed Nov 03 2021 10:22:11 GMT+0100 (Mitteleuropäische Normalzeit) 

; General preferences

G90                              ; send absolute coordinates...
M83                              ; ...but relative extruder moves
M550 P"cnc"                      ; set printer name
M551 P"reprap"			 ; Password - if set to reprad, webcontrol won't ask for it. Mainly used for FTP then

; Network
M552 P0.0.0.0 S1                 ; enable network and acquire dynamic address via DHCP
M586 P0 S1                       ; enable HTTP
M586 P1 S1                       ; enable FTP
M586 P2 S0                       ; disable Telnet
M575 P1 B57600 S0		 ; disable check-sums for UART communication

; Drives					
M569 P0.0 S1 D3                  ; physical drive 0.0 goes forwards
M569 P0.1 S1 D3                  ; physical drive 0.1 goes forwards
M569 P0.2 S0 D3                  ; physical drive 0.2 goes backwards
M569 P0.3 S0 D3                  ; physical drive 0.3 goes backwards
M584 X0.1 Y0.2:0.3 Z0.0          ; set drive mapping
M350 X16 Y16 Z16 I1              ; configure microstepping with interpolation
M92 X656.168 Y656.168 Z1007.874  ; set steps per mm
M566 X1000.00 Y1000.00 Z800.00   ; set maximum instantaneous speed changes (mm/min)
M203 X6000.00 Y6000.00 Z3000.00  ; set maximum speeds (mm/min)
M201 X200.00 Y200.00 Z200.00     ; set accelerations (mm/s^2)
M906 X2000 Y2000 Z1100           ; set motor currents (mA) and motor idle factor in per cent

; Axis Limits
M208 X0 Y0 Z-55 S1               ; set axis minima
M208 X150 Y130 Z20 S0            ; set axis maxima

; Endstops
M574 X2 P"!^io5.in" S1           ; configure switch-type (e.g. microswitch) endstop for low end on X via pin !^io0.in
M574 Y1 P"!^io2.in+!^io3.in" S1  ; configure switch-type (e.g. microswitch) endstop for low end on Y via pin !^io1.in
M574 Z2 P"!^io1.in" S1           ; configure switch-type (e.g. microswitch) endstop for low end on Z via pin !^io2.in

; Spindle
M950 R0 C"nil+io4.out" L20000
M563 P0 S"spindle" R0; define tool 0

; Z-Probe
M558 P0 H5 F120 T6000            ; disable Z probe but set dive height, probe speed and travel speed
M557 X15:215 Y15:180 S20         ; define mesh grid

; Misc
M140 H-1                         ; disable heated bed (overrides default heater mapping) 
G10 X0 Y0 Z0 P0
M453 ; switch to cnc mode
T0                               ; select first tool

[OwenD]

@thomas-weiss
If you have a look at the acceleration calculator here, you will see that with an acceleration rate of 200mm/s2, it will take about 25mm to get up to your desired speed of 100mm/sec
It will also begin to slow down 25mm from the end of the move.
So unless the move is over 50mm, it will spend almost no time at that speed.
The other factor could be that if you have a Z move at the same time, the XY movement is coordinated so that all three axis arrive at the end point at the same time.
As you have a lower Z max speed, this could affect things.

[T3P3Tony]

@thomas-weiss something else to check is there are no speed limit setting commands in the job file from your CAM processor.

You can send M203 from the command line in DWC to confirm the setting, then try moves from one end of your longest axis to the other with F4000 and F6000, sending them directly from the console. e.g.

G1 X0 ;start at 0
G1 X150 F4000
G1 X0 F4000
G1 X150 F6000
G1 X0 F6000