Deliberately stalling stepper motors on one driver

[MortarArt]

I will be using some spare stepper motors to drive pins to close a mould that I've designed via a Duet 3 board. The steppers are small and low current Nema17s, but will conduct the same range of motion with each operation. As a result, I want to be economical, and control them all via the same stepper driver on the board.

However, I want to be sure this won't cause any damage to the board. The reason I'm concerned that it might, is largely that I know very little about electronics, but also that I plan to home the pins by deliberately stalling them out. That is ... I intend to drive the stepper in reverse until the 'pin' element is hitting the plate the motor is fixed to. I'm concerned that stalling one or multiple motors might present a problem for the stepper driver?

Below is a basic render of the pin (in purple), driven by a threaded shaft. STL here.

[bot]

AFAIK this is totally fine and there is zero chance this will damage the electronics. You could reduce current while doing so to make sure no mechanical damage is possible.

[MortarArt]

@bot when you say mechanical damage, you mean to the stepper, or the parts attached to it? I am using very low amp pancake steppers in the hope this has the same effect.

[bot]

@mortarart Sorry, I meant the parts that are attached to the stepper. You have to ensure that the stepper will actually stall, and not just damage everything in its path.

[MortarArt]

@bot aha, yes, that's what I thought you meant. I think that won't be a problem in my case.

[Norder]

@mortarart
In your case, the magic word is probably stall detection or sensorless homing.
More Information (Duet3d Dokumentation).
With this function you can prevent the steppers from continuing to work even though the end for the pins has already been reached.

I have to admit... I don't understand the construction and I can't explain what it's supposed to do.
Unfortunately, I couldn't see any useful function from the Thingiverse upload either.

But maybe it's also because the Google translator translates some texts very cryptically, so that you have to guess what they could mean.

Can you please briefly explain to me what you want to achieve with the construction?
Many Thanks.

Google Translate
-- Original Text --

In Deinem Fall heißt das Zauberwort wohl Stall Detection bzw Sensorless Homing.
Mehr Information (Duet3d Dokumentation).
Mit dieser Funktion kannst Du verhindern das die Stepper weiter arbeiten obwohl das Ende für die Stifte schon erreicht ist.

Ich muss gestehen... ich verstehe die Konstruktion nicht und kann mir nicht erklären wozu sie dienen soll.
Leider konnte ich aus dem Thingiverse Upload auch keine sinnvolle Funktion erkennen.

Vielleicht liegt es aber auch daran dass der Google Übersetzer manche Texte sehr kryptisch übersetzt, so das man raten muss was sie bedeuten könnten.

Kannst Du mir bitte kurz erklären was Du mit der Konstruktion bezwecken möchtest ?
Vielen Dank.

[dc42]

@mortarart when stall-homing axis motors, we recommend using the M913 to reduce the motor current temporarily. This makes the stall easier to detect and also reduces the risk of damaging the mechanics, by reducing the maximum motor torque. See the documentation page that @Norder linked to in his reply.

[MortarArt]

@norder @norder the tool I'm making drives a pin that locks a mould shut. Basically, there will be a slot in the bottom of the mould, and the stepper (with a threaded shaft) would drive a block (purple on thingiverse) in to the slot. This is crucial because I'm using compression moulding, and will use the ram that compresses the mould to eject the plastic part, once it has cooled down.

There are no doubt more elegant solutions to this, but I have these pancake steppers on hand.

[MortarArt]

@dc42 thanks! So you basically reduce the current just for homing? Makes sense to me.

Will the stall homing work across multiple motors?

[MortarArt]

Ok, so I just recalled that my plan was not to do a 'sensorless home', but to travel backwards for the full length of the axis, and assume the axis is at zero because of stalling. Just a small FYI.