Allow to use different idle currents on different drives

nikscha

i have a delta, the cariages tend to drop when on idle. I can increase the idle current but then my extruder drive gets hot.

Veti

see
https://duet3d.dozuki.com/Wiki/Gcode#Section_M906_Set_motor_currents

you can specify the current for each axis independently.

dc42

@nikscha said in Allow to use different idle currents on different drives:

i have a delta, the cariages tend to drop when on idle. I can increase the idle current but then my extruder drive gets hot.

At present the idle percentage is the same for all drives. Typically, 60% idle current is enough for a delta. If your extruder motor gets hot at 60%, it will get very hot at full current.

Another way to prevent carriages from dropping is to use a retractor to support some of the weight of the effector or Bowden tube (or flying extruder if you are using one).

gtj0

@dc42 said in Allow to use different idle currents on different drives:

@nikscha said in Allow to use different idle currents on different drives:

i have a delta, the cariages tend to drop when on idle. I can increase the idle current but then my extruder drive gets hot.

At present the idle percentage is the same for all drives. Typically, 60% idle current is enough for a delta. If your extruder motor gets hot at 60%, it will get very hot at full current.

Another way to prevent carriages from dropping is to use a retractor to support some of the weight of the effector or Bowden tube (or flying extruder if you are using one).

Oh. If you use separate M906 commands with different I values for each axis only the last I value gets used for all drives? Didn't know that.

nikscha

@dc42 to clarify, it's not my primary extruder but part of a multi material upgradr

Veti

if you want to set a different current on the second extruder you specify it like this

M906 E800:500
This is 800 on the first extruder motor and 500 on the second.

on idle those get reduced to 60% of their value respectively.

nikscha

@Veti what i would like to do is have the 2nd extruder at a high current when i use it, even though it will overheat. But it will only be driven for a short amount of time so it wont be a problem. But if it is sitting idle for some amount i want to reduce the current to 10% to counter the overheating. The rest of my rig should idle to 60%

deckingman

@nikscha How about using M913 to adjust the motor current for the second extruder just before, and just after, you use it? I don't know how you are calling the second extruder into action but maybe you could use the tpre and tpost macros and put M913 commands in there. So something like M913 E100:100 just before you use the second extruder, then M913 E100:10 when you finish with it. Or even turn off the idle hold altogether for the second extruder using M84 when you'd finished with it.

dc42

@nikscha, which Duet are you using? On the Duet Maestro and Duet 3 you can set the standstill current percentage using M917.

nikscha

@dc42 Duet wifi +duex2

nikscha

@deckingman that sounds promising. The extruder is controlled by macros for the most part.

deckingman

@nikscha said in Allow to use different idle currents on different drives:

@deckingman that sounds promising. The extruder is controlled by macros for the most part.

In that case it's easy. You could simply use M84 to turn the idle hold off completely when not in use. You can't do that with an X,Y or Z motor because it will reset the homing status, but I can't think of any reason why you couldn't do it with an extruder.