Wort investing in Bed levelling with independent Z motors?

claustro

I have a CoreXY printer evolved from a D-Bot, equipped with three lead screws for the Z-axis.
I'm considering converting it to use three independent lead screw motors. I already have the motors, but since I’m using a Duet 2 WiFi, I’m looking for the most cost-effective option to add an extra stepper driver.

Recently, I bought a Bambulab P1S, and I’ve come to appreciate the convenience of greater automation in the calibration process

Thank you all

droftarts

@claustro Your options are:

a DueX5
add stepper drivers as outlined in https://docs.duet3d.com/en/User_manual/Connecting_hardware/Motors_connecting_external
a third party board like the BTT-EXP-MOT connected to the CONN_LCD connector

As to whether it's worth it, some swear by having only 1 Z motor driving 3 leadscrews, and never having to change the bed level. However, many machines now do come with three (or four) Z motors.

Ian

claustro

@droftarts thank you very much for your comprehensive answer.
I didn't know about the BTT-EXP-MOT option, it seems a very cheap option. Does it have some problem I can incur using it?
I could use it to drive my single extruder letting the duet drive the 3 lead screws. Will still be possible to use a panel due connected with a 4-wire connection?

Andrea

droftarts

@claustro said in Wort investing in Bed levelling with independent Z motors?:

I didn't know about the BTT-EXP-MOT option, it seems a very cheap option. Does it have some problem I can incur using it?

You do need to buy drivers for it, not just the bare board. As far as I'm aware, it only supports two drivers when connected to CONN_LCD. @jay_s_uk may know better than me (I've never used one), and I think @oliof may have used one.

Will still be possible to use a panel due connected with a 4-wire connection?

Yes.

Ian

oliof

@droftarts I actually got the Duex5 from you and never gave the mot exp a chance in the end (-: And then I upgraded to a Duet 3 mini 5+ with the +2 board; only to switch in toolhead toolboards which made managing the IDEX machine so much easier ...

jay_s_uk

@claustro as @droftarts said, you'll need drivers for it. You'll also only be able to use them in standalone mode, so no UART/SPI. So you'll need drivers where you can set the driver current using a potentiometer

claustro

@jay_s_uk
thank you all ,
Can I use a DRV8825? I have several available. Am I correct in thinking that using the expansion board for the extruder won't affect performance, even if a less capable driver is used

oliof

@claustro that should work.

dc42

@claustro two caveats about using a DRV8825:

It supports only x16 microstepping AFAIR. This isn't a problem if your extruder has a large steps/mm (e.g. 300 or more at x16 microstepping), however extruders with low steps/mm (e.g. 100 at x16 microstepping) benefit from using higher microstepping.
Check that the DRV8825 can use 3.3V signal levels on the step, direction and enable pins.

claustro

@dc42 thank you for your answer helpfull as usual
Can you suggest me a fully compatible driver just in case?
Thank you
Andrea