No Z idle torque before Z move commands have been send

Nemesis

I've designed a Cartesian printer (which works brilliantly with the duetwifi )

The Z moves the bed using a two motor setup connected using the Z series outputs on the duet. Because of that the motors may not move independently.

The problem I currently have is that when I power on the printer it does not apply the Idle torq. As soon as you touch the bed a bit one motor moves down. Which means I have to home the Z turn off the printer make it level and startup the printer again.

After the first Z move has been performed Idle troque is applied and I'm unable to move the rods by hand (without using excessive force).

M906 X1200 Y1200 Z1500 E1500:1500:1500:1500 I50
Motors used:

Length: 48 mm axis diameter: 5 mm
Voltage: 3,1 V step angle: 0,9 °
Holding Torque: 4.0 kg-cm Weight: 360 g
Aantal draden: 4 Type: 42BYGHM809
kabellengte: 30 cm Nominal current: 1,7 A
https://www.123-3d.nl/123-3D-NEMA17-HR-stappenmotor-hoge-resolutie-0-9-graden-per-stap-4-0-kg-cm-42BYGHM809-i68-t14804.html

This becomes even more important for the new printer I am designing since it'll have 3 700mm ball screws. with 3 motors each with their own driver. This setup will however have auto bed calibration, but still.

dc42

You could use the following at/near the end of config.g:

G91
G1 S2 Z0.01
G90

This commands the Z axis to move up 0.01mm (any amount that corresponds to at least one microstep will do).

If your E1 motor output is free, take a look at https://duet3d.dozuki.com/Wiki/Bed_levelling_using_multiple_independent_Z_motors.

Nemesis

I'll try that. I did notice that after a print completes there is no idle holding torque as well?

Is this by design? I would assume IDLE hold torque is there whenever the motor isn't moving.

Phaedrux

@nemesis Do you have something in your end print Gcode that turns off the motors? Or do you have your idle current percentage set too low?

Nemesis

@phaedrux Ah yeah I had M84 at the end

Removed it and now it has been resolved. Thnx!

Nemesis

@dc42 said in No Z idle torque before Z move commands have been send:

G91
G1 S2 Z0.01
G90

Thnx this works brilliantly

I did change it to (to make sure when I restart after power outage it's always exactly where it left off):
G91
G1 S2 Z0.01
G1 S2 Z-0.01
G90