Problems with direct drive extruder skipping

[dbrb2]

I have an X5SA printer with a Duet board with the following paramaters:

Firmware Name: RepRapFirmware for Duet 2 WiFi/Ethernet
Firmware Electronics: Duet WiFi 1.02 or later
Firmware Version: 2.05.1 (2020-02-09b1)
WiFi Server Version: 1.23
Web Interface Version: 1.22.6

I am having an odd problem with my extruder.
Even when extruding filament into thin air - no hot-end at all - I am getting quite severe skipping, causing problems printing - see this video:

https://photos.app.goo.gl/zxSyeezumrJqYFRr7

The smallest assist from me from below and it will move slowly, but any idea what the problem may be? The extruder is direct drive - could that be a problem? But the torque required here should be minimal....I have adjusted the tension between the gear and the runner wheel without obvious effect
My steps per mm is:

M92 X80.00 Y80.00 Z1500.00 E100 ; set steps per mm

This seemed to be working - but since calibrating, the knocking has now become much worse

M122
=== Diagnostics ===
RepRapFirmware for Duet 2 WiFi/Ethernet version 2.05.1 running on Duet WiFi 1.02 or later
Board ID: 08DGM-9T6BU-FG3SJ-6JKD4-3S86Q-TAX7F
Used output buffers: 3 of 24 (9 max)
=== RTOS ===
Static ram: 25712
Dynamic ram: 93252 of which 304 recycled
Exception stack ram used: 648
Never used ram: 11156
Tasks: NETWORK(ready,628) HEAT(blocked,1232) MAIN(running,3728) IDLE(ready,160)
Owned mutexes:
=== Platform ===
Last reset 01:46:12 ago, cause: software
Last software reset at 2021-10-28 18:55, reason: User, spinning module GCodes, available RAM 11156 bytes (slot 1)
Software reset code 0x0003 HFSR 0x00000000 CFSR 0x00000000 ICSR 0x0441f000 BFAR 0xe000ed38 SP 0xffffffff Task 0x4e49414d
Error status: 0
Free file entries: 9
SD card 0 detected, interface speed: 20.0MBytes/sec
SD card longest block write time: 109.6ms, max retries 0
MCU temperature: min 30.2, current 34.1, max 34.4
Supply voltage: min 23.2, current 24.0, max 24.5, under voltage events: 0, over voltage events: 0, power good: yes
Driver 0: standstill, SG min/max 0/204
Driver 1: standstill, SG min/max 0/234
Driver 2: standstill, SG min/max 0/127
Driver 3: standstill, SG min/max not available
Driver 4: standstill, SG min/max not available
Date/time: 2021-10-28 20:41:35
Cache data hit count 4294967295
Slowest loop: 26.43ms; fastest: 0.07ms
I2C nak errors 0, send timeouts 0, receive timeouts 0, finishTimeouts 0, resets 0
=== Move ===
Hiccups: 0, FreeDm: 160, MinFreeDm: 95, MaxWait: 336963ms
Bed compensation in use: mesh, comp offset 0.321
=== DDARing ===
Scheduled moves: 11679, completed moves: 11679, StepErrors: 0, LaErrors: 0, Underruns: 0, 0
=== Heat ===
Bed heaters = 0 -1 -1 -1, chamberHeaters = -1 -1
Heater 0 is on, I-accum = 0.3
Heater 1 is on, I-accum = 0.4

[o_lampe]

@dbrb2 from the video I can tell that you are using the extruder the wrong way round, although this should work as well somehow
The spring of the lever arm is quite tight, I'd reduce spring load a lot.

[dbrb2]

Thanks - I'll take a look tonight. I tried the tension much looser without much effect, but will try again.

When you say the wrong way around, how do you mean?

The motor turns, pushes the filament up from below and into the Bowden tube, in the direction of the hot end (when it's connected)

Thanks!

[o_lampe]

@dbrb2 Ok, I didn't see much movement anyway. What I also noticed is hard to describe: the (virtual) axis between drive wheel center and idler wheel center should be perpendicular to the filament path. That's not the case with your extruder.

BTW: How much current does the stepper get? And how much is max. current?

[rjenkinsgb]

With power off and the pressure roller held away from the drive gear, can you turn the motor freely by hand, complete turns?

If so, I'd suggest carefully re-checking or replacing the wiring to the extruder motor; a bad connection causing low power on one winding seems the likeliest cause?

If you cannot find any problems, do you have a spare stepper output you can try it on?

[dbrb2]

@rjenkinsgb thanks. Yes, it moves freely with just a very slight but consistent "judder" as it turns.

I have checked the wiring, which seems ok, and will double check the mechanics later today.

I do have a spare motor as well if it comes to that

[Gixxerfast]

It's not uncommon for these extruders that the idler wheel eats into the aluminum quite rapidly since for many of then there's no spacer underneath (I could remember this wrongly since it was a while since I used this type). I would checkout the idler wheel and arm before looking any further.

Just a thought.

[dbrb2]

@gixxerfast said in Problems with direct drive extruder skipping:

wheel eats into the aluminum quite rapidly since for many of then there's no spacer underneath (I could remember this wrongly since it was a while since I used this type). I would checkout the idler wheel and arm before looking any further.

Ok. I have:

replaced the extruder with an idemntical type
Recalibrated extrtuder
Re-run bed calibration

Still getting a lot of extruder skipping. I wonder if the nozzle could be more blocked than it seems (it is certainly working, but maybe the pressure needed is higher than it should be...?)

I have an old titan extruder somewhere....perhaps I could try that. Should give me more torque...

[Gixxerfast]

@dbrb2 But in the video it looked like it skipped just pushing the filament through the extruder.

Can you post your config.g ?

I think you can just run an empty M906 to show the motor currents.

If all is good there, you might have a bad crimp/connection.

[dbrb2]

@gixxerfast Yes - the video was with no hot-end

Interestingly, I have found that post my changes today (replacing extruder mechanism and motor, checking calibration) , it can extrude into the air fine. I also shortened the bowden tube path slightly.

On a test extrusion, once it starts skipping, it will keep doing so, but a little hand assistance and it will then work fine. So it seems like once it starts to jam, it stays that way until released.

M906 gives me:
Motor current (mA) - X:800, Y:800, Z:800, E:800, idle factor 30%

It feels like there may be room to increase this...? The motot has a niminal maximum of 1.8A:
SL42STH40-1684A 1.8A

My entire config is:

; Configuration file for Duet WiFi (firmware version 2.03)
; executed by the firmware on start-up
;
; generated by RepRapFirmware Configuration Tool v2.1.8 on Thu Apr 23 2020 19:55:13 GMT+0100 (British Summer Time)

; General preferences
G90 ; send absolute coordinates...
G21 ; use mm
M83 ; ...but relative extruder moves
M550 P"TronXY X5SA" ; set printer name

M669 K1 ; select CoreXY mode

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

; Drives
M569 P0 S1 ; physical drive 0 goes forwards
M569 P1 S1 ; physical drive 1 goes forwards
M569 P2 S0 ; physical drive 2 goes forwards
M569 P3 S1 ; Extruder physical drive 3 goes forwards
M584 X0 Y1 Z2 E3 ; set drive mapping
M350 X16 Y16 Z16 E16 I1 ; configure microstepping with interpolation
M92 X80.00 Y80.00 Z1500.00 E100 ; set steps per mm
M566 X900.00 Y900.00 Z12.00 E100.00 ; set maximum instantaneous speed changes (mm/min)
M203 X6000.00 Y6000.00 Z180.00 E1500.00 ; set maximum speeds (mm/min)
M201 X500.00 Y500.00 Z20.00 E250.00 ; set accelerations (mm/s^2)
M906 X800 Y800 Z800 E800 I30 ; set motor currents (mA) and motor idle factor in per cent
M84 S30 ; Set idle timeout

; Axis Limits
M208 X00 Y00 Z0 S1 ; set axis minima
M208 X310 Y310 Z380 S0 ; set axis maxima

; Endstops
M574 X1 Y1 S0 ; set active low endstops
M574 Z1 S2 ; set endstops controlled by probe

; Filament Run Out Sensor
M591 D0 P1 C4 S1 ; Filament runout Sensor for Extruder E0 on E1 Endstop input P1 = signal HIGH.

; Z-Probe
M558 P5 I1 H5 F120 T6000 ; set Z probe type to inductive and the dive height + speeds
G31 P500 X20 Y20 Z0.53 ; set Z probe trigger value, offset and trigger height
M557 X90:280 Y90:280 S20 ; define mesh grid

; Heaters
M307 H0 B0 S1.00 ; disable bang-bang mode for the bed heater and set PWM limit
M305 P0 T100000 B4138 R4700 ; set thermistor + ADC parameters for heater 0
M143 H0 S120 ; set temperature limit for heater 0 to 120C
M305 P1 T100000 B4138 R4700 ; set thermistor + ADC parameters for heater 1
M143 H1 S280 ; set temperature limit for heater 1 to 280C

; Fans
M106 P2 S0 I0 F500 H-1 ; set fan 2 as part cooling fan
M106 P0 T45 S0.7 H1 ; set fan 0 as our hotend fan

; Tools
M563 P0 D0 H1 F2 ; define tool 0 uses part cooling fan 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

; Custom settings are not defined

[o_lampe]

@dbrb2 said in Problems with direct drive extruder skipping:

M906 gives me:
Motor current (mA) - X:800, Y:800, Z:800, E:800, idle factor 30%
It feels like there may be room to increase this...? The motor has a minimal maximum of 1.8A:

That's why! You can easily raise the current to 1.4-1.6A = E1400 or E1600

[dbrb2]

@o_lampe so far that is looking good....

I moved from a geared extruder that was relay hard to thread to this one - but didn't increase the current, despite the obvious need to have more torque!

Fingers crossed....