Issue with dual Z-Axis on Rumba with Marlin firmware

Hi,

I'm trying currenty to set up my new and first printer an Ortbot with a RUMBA board and A4988 drivers on 24V.

On the board I set the dips for all axis to 1/16 (all ON [111])

I've set up the Z-Axis to two drivers, Z and E2. Within the the firmaware I disabled dual Z-Axis in Configuration_adv.h:

#define Z_DUAL_STEPPER_DRIVERS

and in the pins.h:

#define Z_STEP_PIN         57
#define Z_DIR_PIN          56
#define Z_ENABLE_PIN       62
#define Z_MIN_PIN          33
#define Z_MAX_PIN          32

//to use Z_DUAL_STEPPER_DRIVER in Marlin
#define Z2_STEP_PIN        29
#define Z2_DIR_PIN         28
#define Z2_ENABLE_PIN      39

...

#define E2_STEP_PIN        29
#define E2_DIR_PIN         28
#define E2_ENABLE_PIN      39

The problem is, that both steppers run with different speeds totaly asyncronous. I discoupled the steppers from the lead-screws. So they run without load. Both A4988 are ajusted to the same current.

I've no further idea what could be the problem and how to proceed.

hope anyone of you can help me! I lost the hope to spend my spare time till end of the year to finish the printer and get my first prints.

Regards

Andreas

This isn't the answer you are looking for (and I cannot help you with that) but the Rumba is fully capable of running two stepper motors off one driver. I hooked one motor up to the wire connector and one to the pins and have no problems with my Z axis.


Roy

Topic is the A4988 current-limits and thermal topic. I`m affraid to bring it to it's limits.

All I am saying is that I don't think you need to worry. Hook both stepper motors to the one Z driver and you will not hit the current limit or over heat.I've had three different printers (two with the Rumba, all with A4988) and hooked both motors to one stepper driver on all of them and never had an issue with the Stepper over heating or missing steps.

If you are worried about the current limit of the A4988, then why don't you hook up the 2 Z-motors in series? (Especially given that you are using 24V...)

Hi,

The issue is finally solved:

The rumba board is damaged. The jumpers for the steppers were not ok. So I could not set all chanels to 1/16 (Switch position 111). One chanel was running with 1/16 step and the other with 1/4. I'm allready in contact with the dealer. He will send me tomorrow a new board.

Thanks to all your replies.

Regards

Andreas

Were you able to get dual Z steppers to work off one driver? If so can you share how? Possibly upload your firmware as a zip as well? Thank you in advance.