Printer electronics for 8 stepper motors

dc42

@Arminas if TMC2209 drivers are powerful enough for your chosen stepper motors, then I suggest a Duet 3 Mini plus the 2-driver expansion module and one tool board.

Arminas

@dc42 this one https://www.duet3d.com/duet3toolboard1lc ?

2-driver expansion board gives 2.0A each driver at max, yes?

dc42

@Arminas yes that tool board.

The TMC2209 drivers on the Duet 3 Mini and the 2-driver expansion board (Duet 3 Mini 2+) can in theory manage 2A each with good fan cooling, however we suggest running at lower current (e.g. 1.7A or lower) if possible.

Arminas

@dc42 following question about current - if motor current rating: 2.5A/Phase, 1.7A is not too low? I mean, won't I loose some of the motors power?

oliof

@Arminas depends on the torque curve of the motor in question.

dc42

@Arminas what size motors are they? Nema 17 motors are rarely rated above 2.0A.

Arminas

@dc42 48 mm https://ratrig.com/electronics/motors/nema-17-stepper-motor.html

Arminas

This post is deleted!

dc42

@Arminas how large is the printer and how heavy are the axes? The 40mm version may be a better choice.

Arminas

@dc42 it's 400 x 400 mm in coreXY, but I am planning to do an AWD mode, so the belt path will be shorter and there will be 4 motors, not 2. Weight is around 900 gr I believe for the printhead and Y axis.

Arminas

@dc42 because it is better to use a 40 mm motors at full amps, compared to 48 mm motors at 70% of their amps?

dc42

@Arminas it's usual to run stepper motors at between 60% and 80% of rated current, because at full current they get very hot.

Motors rated 2.0A or lower are a good match for TMC2209 drivers. TBH I've not come across Nema 17 motors rated above 2.0A before.

deckingman

@dc42 .............although, if the data sheets in the OP's link are to be believed, the 48mm version has a very low inductance (1.5mH) compared to the 40mm version at 3.6mH, which might be something to take into consideration.

Arminas

@dc42 regarding what you said about duet2 - what would be the best set up for the same configuration printer, but with nema23 motors of 2.8 amps rated current for XYZ axes (8 in total) + 1 nema17 for the extruder?

Duet2 + duex would seem like an option, since it’s drivers are more powerfull compared to duet3 mini, and duet3 6hc looks too powerfull. But duet2 does not support tool board…

dc42

@Arminas for eight Nema 23 motors I suggest a 6HC and a 3HC. You are correct that a Duet 2 + DueX5 could drive the motors (just) but not the tool board. However, I advise against using Duet 2 in new designs because as well as the lack of CAN-FD support it has insufficient memory to accommodate further improvements to firmware functionality.

oliof

@dc42 the LDO LDO-42STH48-2504 are rated at 2.5A. I did submit their config to the back emf calculator in a PR a while ago but I think it never got picked up.

Arminas

@oliof how can I find it out? The torque curve

oliof

@Arminas Check the technical data sheet or ask the motor manufacturer if it's not included.