static torque when powered

In order to test extruder torque, I have tied weights in the extruder gear (direct drive). After that, I tried to lift it. Depending on how much weight is hung, when the motor stops, it suddenly starts to unwind. Is it normal?

weight: 350 grams
Gear diameter: 11 mm
motor: NEMA 17HS4218

That's physics...
As soon as the weight drops a bit from a skipped step, it gains velocity which adds to the static weight. This causes a chain reaction.
-Olaf

Or maybe the motor is instantly powered off by the board when the last command has been executed?

Quote
o_lampe
That's physics...
As soon as the weight drops a bit from a skipped step, it gains velocity which adds to the static weight. This causes a chain reaction.
-Olaf

the gear unwind right after it has the lifting job done. Is the board powering off by its own?

I can´t stop gear spinning even applying force, but I can move the gear when the gear velocity is zero. That torque is lower than the lifting torque, but it´s higher than the magnet motor torque when powered off.

You need to look at the firmware that you are running, and what it does after it completes the "Move" commands that you send to it.

For example, all of my steppers are "locked solid" when the printer is under the control of the Pronterface UI (so current is being supplied to all motors, held in position and ready to move), but at completion of a print job, the G-Code includes a M84 "Stop Idle Hold" command [reprap.org] , which means I can manually move the X and Y axes, wind the Z-axis rods independently (if I need to re-level my X-Axis for example), and turn the Extruder (if the extruder is still hot, or there is no filament loaded).

I would guess that your control software that you are using for testing is de-energising the steppers when it has completed the Move commands, so they have no static holding torque.

---

Follow my Mendel Prusa build here: [julianh72.blogspot.com]

Quote
julianh72
You need to look at the firmware that you are running, and what it does after it completes the "Move" commands that you send to it.

For example, all of my steppers are "locked solid" when the printer is under the control of the Pronterface UI (so current is being supplied to all motors, held in position and ready to move), but at completion of a print job, the G-Code includes a M84 "Stop Idle Hold" command [reprap.org] , which means I can manually move the X and Y axes, wind the Z-axis rods independently (if I need to re-level my X-Axis for example), and turn the Extruder (if the extruder is still hot, or there is no filament loaded).

I would guess that your control software that you are using for testing is de-energising the steppers when it has completed the Move commands, so they have no static holding torque.

Interesting Julianh72. I am currently using full graphic smart lcd controller. I did not insert Gcode SD card, I am only testing axle movement.

I can test axle movement in full graphic smart lcd controller with: main menu--> prepare--> move axis--> 1mm --> extruder

It seems only extruder motor is powering off after movement.

#define DISABLE_E false // For all extruders

In Marlin this line looks like that. I don't know, if you can change this with an M-command using pronterface, maybe you'd have to reflash the firmware.
-Olaf

Quote
o_lampe

#define DISABLE_E false // For all extruders

In Marlin this line looks like that. I don't know, if you can change this with an M-command using pronterface, maybe you'd have to reflash the firmware.
-Olaf

thanks for the advice Olaf,

I have the following configuration:

#define DISABLE_X false
#define DISABLE_Y false
#define DISABLE_Z false
#define DISABLE_E false // For all extruders
#define DISABLE_INACTIVE_EXTRUDER true //disable only inactive extruders and keep active extruder enabled

I will try to set DISABLE_INACTIVE_EXTRUDER to false

Good news! There wasn´t torque extruder problems, but I had a temperature gradient along the hot end and nozzle structure. I insulated nozzle and hot end all together with cotton and Kapton tape. At the first try I was able to extrude 1170mm ABS, with 0.3mm, nozzle in 20 seconds, that´s about 60mm/s!

Maybe I had my nozzle temperature much below that the thermistor was showing before insulating.

Your advice helped me to check for firmware problems and it opened my mind to think about temperature gradient issues in nozzle area.