Anet A8 Stepper motor question

OBELIKS

There is also data from this page: https://3dprint.wiki/reprap/anet/a8/steppermotor
The SL42STH40-1684A motor specs are:

Step Angle: 1.8°
Step Angle Accuracy: ±5% (full step, no load)
Voltage: 2.8V
Current per phase: 1.68A
Resistance per phase: 1.65Ω
Resistance accuracy: ±10%
Inductance per phase: 3.2mH
Inductance accuracy: ±20%
Holding torque: 3.6 Kg·cm (0.4 N·m)
Moment of inertia: 54 g/cm^2
Weight: 0.28 kg
Orientation torque: 150 g/cm
Length: 40 mm
Temperature rise: 80°C max (rated current, 2 phases on)
Ambient temperature: -20°C ~ +50°C
Insulation resistance: 100MΩ min, 500VDC
Shaft radial play: 0.02 mm max (450g load)
Shaft axial play: 0.08 mm max (450g load)
Max. radial force: 28N (20mm from the flange)
Max. axial force: 10N

But I am not sure these are correct, and in the end there is no guarantee that the drives you have on your Anet are really these.

wilriker

@obeliks This info is outdated. Anet used to use 1.7A steppers but switched to the 0.9A steppers "because they not get so hot" - which probably means they just get them cheaper.

Black Canary

@wilriker Thanks for the config file, unfortunately only had time today to finish the upgrade of the Duet3D in the anet A8. I already tuned the heaters but I am getting an error saying that I have no home files when I try to home the axis, do you know why is this happening?

wilriker

@black-canary RepRapFirmware works a little different than most other firmwares. Also for homing. It uses 4 different files to home depending on what you want to do. They belong into the /sys folder on the SD card (also accessible via Settings -> System Editor in DWC). They should have been part of the configuration that you get from https://configurator.reprapfirmware.org. Anyway I'll include mine below (filename is always on the first line):

; homex.g
; called to home the X axis
;
; generated by RepRapFirmware Configuration Tool on Sat Apr 28 2018 20:07:26 GMT+0200 (CEST)
G91               ; relative positioning
G1 Z2 F3000 S2    ; lift Z relative to current position
G1 S1 X-260 F3600 ; move quickly to X axis endstop and stop there (first pass)
G1 X5 F3000       ; go back a few mm
G1 S1 X-260 F360  ; move slowly to X axis endstop once more (second pass)
G1 Z-2 F3000 S2   ; lower Z again
G90               ; absolute positioning

; homey.g
; called to home the Y axis
;
; generated by RepRapFirmware Configuration Tool on Sat Apr 28 2018 20:07:26 GMT+0200 (CEST)
G91               ; relative positioning
G1 Z2 F3000 S2    ; lift Z relative to current position
G1 S1 Y-250 F1800 ; move quickly to Y axis endstop and stop there (first pass)
G1 Y5 F3000       ; go back a few mm
G1 S1 Y-250 F360  ; move slowly to Y axis endstop once more (second pass)
G1 Z-2 F3000 S2   ; lower Z again
G90               ; absolute positioning

; homez.g
; called to home the Z axis
;
; generated by RepRapFirmware Configuration Tool on Sat Apr 28 2018 20:07:26 GMT+0200 (CEST)
G91               ; relative positioning
G1 S1 Z-260 F900 ; move quickly to Z axis endstop and stop there (first pass)
G1 Z2 F3000       ; go back a few mm
G1 S1 Z-260 F180  ; move slowly to Z axis endstop once more (second pass)
G90               ; absolute positioning

; homeall.g
; called to home all axes
;
; generated by RepRapFirmware Configuration Tool on Sat Apr 28 2018 20:07:26 GMT+0200 (CEST)
G91                     ; relative positioning
G1 Z2 F3000 S2          ; lift Z relative to current position
G1 S1 X-260 Y-250 F3600 ; move quickly to X and Y axis endstops and stop there (first pass)
G1 X5 Y5 F3000          ; go back a few mm
G1 S1 X-260 Y-250 F360  ; move slowly to X and Y axis endstops once more (second pass)
G1 S1 Z-260 F900        ; move quickly to Z axis endstop and stop there (first pass)
G1 Z2 F3000             ; go back a few mm
G1 S1 Z-260 F180        ; move slowly to Z axis endstop once more (second pass)
G90                     ; absolute positioning

OBELIKS

@wilriker Ah, OK. Mine are probably the old ones. I tried to use 500mA, ad the printer was not moving. So that means they must be 1,68A version. And they get to ~50°C with 23°C ambient temperature.

wilriker

@obeliks It is quite easy to tell: the new ones are marked as 42SHDC3025-24B on the back (probably easiest to spot on the extruder motor). The old one have either another or no model number on them.

OBELIKS

Yup. Exactly.

mortn

@wilriker Thanks for posting your config.g ! Made setting up my A8 a lot faster Just one question: how did you come up with the M569 C values?

I just tried to do some investigating in the trinamic driver docs, but without an electronics degree its quite cryptic to me

wilriker

@mortn said in Anet A8 Stepper motor question:

@wilriker Thanks for posting your config.g ! Made setting up my A8 a lot faster Just one question: how did you come up with the M569 C values?

I just tried to do some investigating in the trinamic driver docs, but without an electronics degree its quite cryptic to me

It all came together here https://forum.duet3d.com/topic/5392/does-m906-set-rms-or-peak-current/19

Basically this is a bitmap of flags where the TOFF part has the highest influence on noise at standstill. At the end of the linked thread there is also a list of values for all 16 TOFF variants. Not sure if the link is also in that thread but I wrote a little tool to create these numbers:
https://github.com/wilriker/chopconf-generator (under releases are pre-compiled versions)

In one of the next RRF versions @dc42 will implement a dedicated parameter to set TOFF without having to use these cryptic bitmap-integer in decimal notation (hex notation does no longer work).

P.S.: the value for TOFF is motor specific - and note that I did not write model but motor, i.e. even if you have the same model your motor is different and may need different TOFF value to be most silent. So please test various values.

Black Canary

@wilriker Cheers man. Like I told you I'm really beginer in this, I did not even created the files on the website you mentioned because I thought I just needed the config.g file, It's working now, I feel that I can make it work better because It doesn't look 100% good, but I will eventually get it to the point. Just another question by the way, Imagine that I want to now use the board in another printer I go to the website and just put the details of the printer, but I got a bit confused in the motors settings, how should I know what is the, max speed and the Steps per mm and every other information? in the data sheet of the motor? (if it has one how about if it doesn't?)

wilriker

@black-canary said in Anet A8 Stepper motor question:

[...] how should I know what is the, max speed and the Steps per mm and every other information? in the data sheet of the motor? (if it has one how about if it doesn't?)

This is a tough one. If this is e.g. a totally new printer build from scratch you'd have to start at reasonable defaults and try from there.
Here is how I did it: before switching my A8 to Duet I was using Marlin on the stock board. So I looked at Marlin's values for these settings and just took them exactly over to the configurator for RRF. Except that I forgot

M204 P400 T1000                                    ; Lower accelerations when printing though

which led to... say... a surprisingly rough first print. From there I adjusted the values partly by trial-and-error and partly by using the EMF calculator at https://reprapfirmware.org/. Take the value of "speed at which torque starts to drop (low slip angle)" as the new maximum speed.

Black Canary

@wilriker Thanks again, at this moment it's not to build one from scratch it's actually to upgrade one printer. So in this case this printer uses marlin, could I just literally drag and drop the config files? Or my only option is to copy the values to the https://configurator.reprapfirmware.org and then use those files? (Sorry if i'm bothering you but I really like 3D printing and my only regretting is knowing just a little)

wilriker

@black-canary No worries, we all started some point in time. And this forum was also a great help to me in gaining knowledge (besides hours of videos at YouTube ).

You cannot use the files used with Marlin. RRF would not understand them. It is actually your second idea how it is done: get the values from the appropriate Configuration.h or Configuration_adv.h in Marlin and enter them in RRF Configurator. This will then create all the necessary files in the appropriate format.

The biggest difference of RRF compared to Marlin is that you will (probably) never compile RRF yourself. Everything in RRF is configured via GCode - and it can be done at literally any point in time. So if e.g. you decide in the middle of a print that your acceleration is to high you can just reduce it live with the appropriate GCode command (btw. something I already did more than once).

Black Canary

Good man @wilriker, Thanks a lot!