Doubled flow on slow speed parts of print

[Forever.exe]

Hi, I'm relatively new to 3D printing and I'm currently working on a BLV mgn Cube that I managed to get for cheap with a Duet 2 Wifi V1.03 and RRF3.5 using Cura as a Slicer.

I've had fun so far, building and testing various aspects of the machine, and now is ready to do some test prints.

After calibrating both extruder and Axis, the first test print I've done was an hollow 25x25x10mm cube since I wanted a fast test print.

The problem is during slow parts like the corners, where the extruders goes from a flow rate of 16mm/s^3 to a doubled 32mm/s^3, which is weird because I imagine it should extrude less when going slow since it doesn't need to push a lot while on faster movements there should be more extrusion.

Anyway, it ends up creating a mass of plastic in those sections, and inevitably ends to harden and get grabbed by the nozzle, while the extruder starts skipping and making some raw plastic dust.

Searching for solutions, I've tried to do a fast print (default 100mm/s), slow print (15mm/s), 0% to 100% flow rate, and decreasing steps in the config.g file.

At this time I don't know if I have too much current on the motors, wired something bad, missing something on the slicer or on the firmware or if I did the math wrong.

I'll leave here my config, the print's .3mf and some photos of what it does. I cannot upload photos or files from the time of writing, so I'll leave here a Drive folder link where you need to add the starting h
(ttps://drive.google.com/drive/folders/1b5V6NvPhvoKB8coNeH9Hivv2M8vaHcZv?usp=sharing), it contains the photos, the .3mf and the .curaprofile test profile.

The steppers for the axis are Nema17 1.8° bipolar stepper motors (ttps://www.omc-stepperonline.com/download/17HS19-2004S1.pdf), while the extruder motor is a TriangleLab 23mm 1.8° stepper motor (ttps://trianglelab.net/products/23mm-stepper-motor)

Thank you in advance.

; Configuration file for RepRapFirmware on Duet 2 WiFi
; executed by the firmware on start-up
;
; generated by RepRapFirmware Configuration Tool v3.5.8 on Mon Dec 09 2024 14:50:05 GMT+0100 (Ora standard dell’Europa centrale)

; General
G90 ; absolute coordinates
M83 ; relative extruder moves
M550 P"Stampa Rossetti" ; set hostname

; Accessories
M575 P1 S0 B115200 ; configure PanelDue support

; Network
M552 S1 ; configure WiFi adapter
M586 P0 S1 ; configure HTTP

; Smart Drivers
M569 P0 S0 D2 ; driver 0 goes forwards (X axis)
M569 P1 S0 D2 ; driver 1 goes forwards (Y axis)
M569 P2 S0 D2 ; driver 2 goes forwards (Z axis)
M569 P3 S1 D2 ; driver 3 goes backwards (extruder 0)
M569 P4 S0 D2 

; Motor Idle Current Reduction
M906 I30 ; set motor current idle factor
M84 S120 ; set motor current idle timeout

; Axes
M584 X0 Y1 Z4:2 E3 ; set axis mapping
M350 X32 Y32 I1 ; configure microstepping without interpolation
M350 Z16 I1 ; configure microstepping with interpolation
M906 X1600 Y1600 Z1600 ; set axis driver currents
M92 X159.7 Y159.7 Z400 ; configure steps per mm
M208 X-20:240 Y0:220 Z0:340 ; set minimum and maximum axis limits
M566 X600 Y600 Z24 P1 ; set maximum instantaneous speed changes (mm/min)
M203 X35000 Y35000 Z12000 ; set maximum speeds (mm/min)
M201 X6000 Y6000 Z400 ; set accelerations (mm/s^2)

; ================ Independent Z Leveleing =================
M671 X20:220 Y95:95 S10			   	; leadscrew pivot point:

; Extruders
M350 E16 I1 ; configure microstepping with interpolation
M906 E1000 ; set extruder driver currents
M92 E399.23 ; configure steps per mm
M566 E1000 ; set maximum instantaneous speed changes (mm/min)
M203 E3000 ; set maximum speeds (mm/min)
M201 E1500 ; set accelerations (mm/s^2)

; Kinematics
M669 K1 X1:1:0 Y1:-1:0 Z0:0:1 ; configure CoreXY kinematics

; Probes
M950 S0 C"exp.heater3" ; create servo #0 for BLtouch
M558 K0 P9 C"^zprobe.in" H6 F120 T6000 R0.4 B1; configure BLTouch probe via slot #0
G31 P25 X0 Y-57 Z1.945 ; set Z probe trigger value, offset and trigger height


; Endstops
M574 X1 P"xstop" S1 ; configure X axis endstop
M574 Y2 P"ystop" S1 ; configure Y axis endstop
M574 Z1 S2 ; configure Z axis endstop

; Mesh Bed Compensation
M557 X10:220 Y10:140 S40:40 ; define grid for mesh bed compensation

; Sensors
M308 S0 P"bedtemp" Y"thermistor" A"Heated Bed" T100000 B3950 ; configure sensor #0
M308 S1 P"e0temp" Y"thermistor" A"Nozzle" T4500000 B5373 C1.961112e-8; configure sensor #1
M308 S2 P"mcu-temp" Y"mcu-temp" A"Duet Board"

; Heaters
M950 H0 C"bedheat" T0 ; create heater #0
M143 H0 P0 T0 C0 S140 A2 ; configure heater monitor #0 for heater #0
M307 H0 R0.168 K0.528:0.000 D2.18 E1.35 S1.00 B0 ; configure model of heater #0, PID
M950 H1 C"e0heat" T1 ; create heater #1
M143 H1 P0 T1 C0 S290 A2 ; configure heater monitor #0 for heater #1
M307 H1 R3.034 K0.614:0.000 D5.49 E1.35 S1.00 B0 V24.4 ; configure model of heater #1, PID

; Heated beds
M140 P0 H0 ; configure heated bed #0

; Fans
M950 F0 C"fan0" ; create fan #0
M106 P0 C"Extrude1" S0.4 B0.1 H1 T60 ; configure fan #0
M950 F1 C"fan1" ; create fan #1
M106 P1 C"Extrude2" S0.4 B0.1 H1 T60 ; configure fan #1

; Tools
M563 P0 D0 H1 F0:1 ; create tool #0
G10 P0 X0 Y0 Z0    ; set tool 0 axis offsets
M568 P0 R0 S0 ; set initial tool #0 active and standby temperatures to 0C

; Miscellaneous
T0 ; select first tool

; Custom settings
M564 H0
M911 S10 R11 P"M913 X0 Y0 G91 M83 G1 Z3 E-5 F1000" 		; set voltage thresholds and actions to run on power loss

[droftarts]

@Forever-exe The forum doesn't allow new users to post links, to help combat spam. I've given you an upvote, I think you need a couple to be able to post links and upload files. See https://forum.duet3d.com/topic/30602/managing-spam-accounts

I'll have a look at the linked files when I get a chance. At a guess, I expect Cura is adding acceleration code at the corners. Check you have it set up correctly, see https://docs.duet3d.com/en/How_to_guides/Calibration#h-7-suggested-slicer-settings

Please send M122 and post the response, so we can see the exact firmware version you are using.

Ian

[Forever.exe]

@droftarts thank you for the reply and sorry for the late reply.

After sending the message I continued tinkering and searching for clues of why that happened, and I've discovered what was the problem:

By using the BLV mgn profile on Cura, the special option "Set Relative Extrusion" is disabled, meaning that when I was applying the "set relative extrusion" command inside the gcode, the acual extrusion values inside the print gcode were still absolute and exponentially told the machine to extrude more and more filament, more than it could do.

By removing the relative extrusion command, the printer worked like a charm.
After that, I've tried using other slicers like Orca, and it managed to convert to relative extrusion with no problem, with also a lot more of options for me to customize. So I'll probably stick to it from now on.

That was genuinely my bad to not have thought of that before, tomorrow I'll set this post to resolved for the posterity.