MMU Motors warm while idle
I'm playing around with my new MMU, and among other problems I will search the forum for, I have warm motors while the printer is powered on but idle. Do the Selector and Extruder motors need to be actively powered during idle? It seems like they are forcing themselves to hold to a specific location. No movement, but you can tell the motors are working.
I've just installed the latest firmware today, and am taking my time figuring this thing out. (MK3 3.4.1, MMU2 board 0.9.0)
Re: MMU Motors warm while idle
Unfortunately, the motors do need to be on, otherwise they con lose track of position 🙁
They are only positioned once at startup and then depend on maintaining the position.
Peter
Please note: I do not have any affiliation with Prusa Research. Any advices given are offered in good faith. It is your responsibility to ensure that by following my advice you do not suffer or cause injury, damage…
Re: MMU Motors warm while idle
Ah! Makes sense. That explains the sound I´m hearing as well... At first I thought this was a fan running somewhere but it turned out it´s one of the motors.
This is a serious design flaw for me as I tend to let the printer powered. This will have to change now. 🙁
Re: MMU Motors warm while idle
Dennis this issue has been identified by other users as well. It bugs me as also. Someone made a GitHub issue:
https://github.com/prusa3d/MM-control-01/issues/27
Perhaps you could add your experiences to the GitHub linked above. Hopefully it's addressed in a future firmware release. Maybe after some set idle period, current gets lowered. Then a re-home to ensure correct position....
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Prusa MK2.5 kit > MK3 > MK3+MMU2 (R3/B/7) 😀
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Re: MMU Motors warm while idle
I am new to my 3d printer, and waiting on my MMU, but I have been working with stepper motors for many years. Here is a fairly simple explanation:
Stepper motors are basically a multi pole permanent magnet rotor driving the output shaft with typically four stationary electric coils in the body. Applying sequential power to the coils magnetically attracts (or repels) the poles in the rotor and rotates the output shaft or holds it when the sequence stops.
When you remove all power from a stepper motor the magnetic field is gone and the rotor will most likely loose its position by at least one step, maybe more if there is tension from whatever it is driving.
In industry, the stepper control boards usually have a low power mode for when the stepper is not moving. This will reduce (but not eliminate) power waste and motor heating.
If there is a lot of tension from whatever the motor is driving, then the low power mode can still allow slippage because the motors magnetic field is reduced along with its holding torque.
One option is to use a gearhead stepper motor that reduces the torque needed to drive the shaft. This allows the standby power to be even lower without risking loosing a step and it can give more precision to the final shaft output step size.
I dont know if PRUSA driver boards use a lower power standby for the steppers and I doubt they are using gearhead steppers.
Wayne
Re: MMU Motors warm while idle
I dont know if PRUSA driver boards use a lower power standby for the steppers and I doubt they are using gearhead steppers.
Yes, the Trinamic drivers (and MMU firmware) employ both "holding" and "running" currents, with the "holding" current being used when the motor is not in use.
However, the situation is further complicated by micro-stepping. Stepper motors will naturally "hold" at a full-step position and will move to the nearest full-step position when power is removed, so when using micro-stepping there always must be a holding current to prevent this.
Peter
Please note: I do not have any affiliation with Prusa Research. Any advices given are offered in good faith. It is your responsibility to ensure that by following my advice you do not suffer or cause injury, damage…
RE: MMU Motors warm while idle
Hi
Has anyone updates on this problem ?
In my case on MK3S MMU2S and last firmwares, the problem is still present on all motors of the MMU2S and the Z motors of the MK3S.
So the x, y and nozzle motors are cold !
Is there a risk to keep the printer always on ?