extruder e steps doubled

Sbutterfield

I just changed extruder motors and my e steps doubled. Any ideas why that happened? Does it even matter?

Here is my setup.
firmware: Duet WiFi 1.0 or 1.01
Firmware version: 2.02(RTOS) (2018-12-24b1)
WiFi Server Version 1.23
Web interface Version 1.22.6

Old motor: E3D Slimline stepper motor (0.9 deg)
Bondtech BMG extruder
Microstepping 16x
e steps 840
current 1400

New motor: LDO pancake motor part number LDO-42STH25-140MAC (0.9 deg)
Bondtech BMG extruder
microstepping 16x
e steps 1560
current 1200

I didn't change the wiring.

It should have been a drop in replacement. I'm stumped why I needed to almost double my e steps.

here is some of the config file

; Axis and motor configuration
M350 X16 Y16 Z16 E16 I1 ; Configure microstepping with interpolation
M92 X80 Y80 Z3230 ; Set steps per mm
M92 E1560 ; Set extruder steps/mm
M201 X500 Y500 Z250 E600 ; Set accelerations (mm/s^2)
M203 X10000 Y10000 Z200 E2000 ; Set maximum speeds (mm/min)
M566 X200 Y200 Z20 E500 ; Set maximum instantaneous speed changes (mm/min)

M906 X2600 Y2600 Z1500 E1200 I30 ; Set motor currents (mA) and motor idle factor in percent

mendenmh

I'll bet the new stepper is an 0.9 degree (400 steps/turn) instead of the more common 1.8 degree (200 steps/turn) motor.

Phaedrux

Nope, doesn't make any sense. How did you arrive at the new value?

I'd say the original was a 1.8 degree too, but 800 ish steps per mm for the bondtech would be correct for a 0.9.

Sbutterfield

Yea, it's weird. Both motors are 0.9 deg. Per Bondtech's website a 1.7 deg stepper motor should be around 415 steps/mm. I was at 840 for the old slimline motor which is a 0.9 deg stepper motor. That makes sense.
Here is my process:
-using PETG
-set my extruder temp to 235°C
-measured 100mm of filament and marked it
-On the duet WiFi I opened the extrusion menu
-selected 100mm
-selected 5mm/sec
-selected extrude
-only 50mm was extruded
-doubled the value and iterated until I was able to extrude 100mm

The final e step value was 1560.

Other than the fact that it's weird and I want to figure out WHY this is happening is there any negative impact to having the steps so high?

Phaedrux

Try this method and see if you're getting the same results.

https://duet3d.dozuki.com/Guide/Ender+3+Pro+and+Duet+Maestro+Guide+Part+4:+Calibration/40#s165

bot

Is it possible that the newer pancake motor has much less torque, and cannot reliably microstep to the same resolution? Try setting the E axis to 1/8 or 1/4 stepping.

zapta

If my calculation is correct, extruding 100mm with 1560 microsteps per mm, and 16x400 microsteps per revolution will result in

100 * 1560/16/400 = 24.375 revolutions.

Make a black mark on the stepper shaft and see if you count ~24 revolutions while extruding 100mm.

Sbutterfield

I finally figured it out. The grub screw on my bondtech extruder was loose. The stepper motor would spin shaft assembly but the drive gear would only turn sporadically. I put some locktite on the grubscrew, put it all back together and its working great and the E steps are the same as before! For future reference if you see the large gear spinning on the shaft assembly and are getting inconsistent sporadic extrusion check to see if a screw is loose.