Stall detection with 2 motors

noisettetbou

@Phaedrux said in Stall detection with 2 motors:

Well what behaviour do you want when a stall is detected? stop both motors or stop each individually?

I want to stop both motors. No choice, they're in series on the same driver.
This is the results of my M98 P"config.g" :
09/09/2020 à 22:16:49 M98 P"config.g"
HTTP is enabled on port 80
FTP is disabled
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Warning: Heater 0 appears to be over-powered. If left on at full power, its temperature is predicted to reach 365C
Warning: Heater 0 appears to be over-powered. If left on at full power, its temperature is predicted to reach 269C

Note my My PID aren't done for heaters errors.

Phaedrux

@noisettetbou said in Stall detection with 2 motors:

I've found more than 1000 mm/s. It's crazy !

That seems wrong based on your motor specs. My calculation gives 145mm/s

Stall detection H value			
Hmin = full_steps_per_rev * rated_current * actual_current/(sqrt(2) * pi * rated_holding_torque)			
Full_steps_per_rev	200		
Rated_current (A)	2.100		
Actual_Current (A)	1.000		
Rated_holding_torque (Nm)	0.650		
Squareroot(2)	1.414		
Pi	3.142		
Hmin	145.436

You may be able to reduce that speed further if you reduce the motor current further. You should try reducing it as much as possible such that you still have reliable movement. Right now you're using 50%, try 30%.

noisettetbou

@Phaedrux
Thanks for the calculation. I've confused the units of torque.

I've tried speeds up to 300 mm/s and differents current between 20 and 100% but nothing.

Phaedrux

When you say the motors rotate in opposite directions, what do you mean?

Can you post a photo of the printer?

noisettetbou

@Phaedrux
That's a link to a photo of Y axis :
https://photos.app.goo.gl/oeFLBnE1iaKtcJMNA
The motors are biaxials and synchonysed by a shaft

oliof

@noisettetbou possibly crazy talk but could you disable one stepper for homing only? As they're synchronized by a shaft you should be able to live with that.

noisettetbou

@oliof
It's a good idea. I've tried and it is the same problem.
So 2 motors on same driver and the series wiring aren't the source of the problem.
I'm trying to invert drivers.

noisettetbou

I've tried to invert driver with X and always the problem. As if my Y motors aren't compatibles with the stall detection.
Is it possible ? Crazy, no ?

oliof

Oh two steppers on a single driver? I can see how that will be bothersome/impossible. Maybe if you drive each motor independently ...

noisettetbou

@oliof
It's no a problem if current is respected. I use two motors on same driver in X axis and no problem. And I done as you said for trying, so there is only one motor right now, and no good stall detection...

Phaedrux

I think an endstop switch might be in your future.

noisettetbou

@Phaedrux
I think too... but I would like to understand

dc42

Have you used the motor EMF calculator at reprapfirmware.org to verify that you have enough VIN voltage to drive 2 motors in series without loss of torque?

oliof

Difference between X and Y is often that Y moves more mass and there for needs better tuning. But I agree that an endstop likely will give you reliable results faster.

noisettetbou

@dc42 @Phaedrux @oliof
dc42 has reason. My voltage is enough for each axis but limit for all axis in the same time.
So i've decided to installing a Duex5.