Delta with "AllWheelDrive" possible?

DavidG_68kg_PLA

Hey Guys,

I'm happily using a 6HC+SBC on a convential delta mechanics with three towers, one stepper each. I want to go dual drive, so one stepper on the lower end, one on the upper end.
I already read, that is possible to assign multiple motors to one axis & endstop.

Are there any known traps, like with (initial) synchronisation?
In case of a step loss, in theory both mechanically synchronized motors should loose the same amount of steps. But because of the belts compliance there might be different amounts of step losses, resulting in raised currents. Is there a function available to detect that?

Thanks in advance, Fabian

Phaedrux

I haven't seen it done with a delta before, but with other kinematics using multiple motors per axis the belt linkage is enough to keep them in sync. The belts would need to be quite loose to have enough compliance to allow the motors to snap to different positions.

Ensure that the motors are identical.

With a 6HC you'll have 6 drives to work with. Are you going to add a toolboard for the extruder?

If you want to do a quick test to see what the firmware does, try mapping the dual drives for X Y Z in M584 and see what it says when you send M98 P"config.g"

o_lampe

@DavidG_68kg_PLA said in Delta with "AllWheelDrive" possible?:

there might be different amounts of step losses, resulting in raised currents.

Stepper motors always run with the same preset current. There is no current change you could detect...
But the object model might spit out different error-counts if 'stall detection' is active?

o_lampe

@DavidG_68kg_PLA said in Delta with "AllWheelDrive" possible?:

Are there any known traps, like with (initial) synchronisation?

You may want to energize both steppers in 'fullstep mode' before you tighten the grubscrews on the pulley. Making sure they are 100% aligned.

DavidG_68kg_PLA

Thanks a bunch for all your effort and answers, really appreciate it!

@Phaedrux yes, I'm already using the can toolboard. Identical steppers are so far obvious, thanks for reminding.

I assigned the additional motors to the drivers:

M584 X0.0:3 Y0.1:4 Z0.2:5 E121.0                          ; map motors to drivers in the Format: Axis Board.Driver:Driver

M98"config.g" answers only a green bar with the command itself, nothing more. What should happen?

@o_lampe thanks for the hints, synchronizing in fullstep mode is the answer i was looking for with my question of initial sync!

Phaedrux

Does @dc42 have any insight on whether this setup should "just work" or not?

breed

@DavidG_68kg_PLA definitely can be done. Nitram I believe was doing this on a modified anycubic linear delta during the speedboatrace.

dc42

@DavidG_68kg_PLA said in Delta with "AllWheelDrive" possible?:

Are there any known traps, like with (initial) synchronisation?

The main risk I see is that if you energise both motors together, they may try to jump in different directions to an appropriate multiple of 4 full steps. To avoid this it might be better to power up one motor, pause, then power up the other one. One possibility is initially to assign just one motor to each tower in M584, send M17 to power them up, pause, then use M584 to assign both motors to each tower and immediately use M17 to power them all up.

DavidG_68kg_PLA

Thank you all!

@dc42: thanks for the immediate solution! A multiple of 4 full steps would be a difference of 4*1,8°, which on our pulleys (D=18mm) equals to a lenght delta of about 1,2mm. At least on the mechanical side of things, that seems unlikely to me.

I will hit up Nitram on his discord, asking him for his experience.