Z Motors loosing sync?
-
Hi,
I'm hoping someone more knowledgeable than me can help?
I am using a Prusa like 3dPrinter with a Duet2 WiFi board and generally it works great.
The two Z motors connect to the Duet via the Z motor 1 & 2 sockets (in series I think?). Occasionally the two motors seem to loose sync and the X gantry moves differently at each side. Occasionally the next move seems to correct this but sometimes I have to level the X axis gantry.
Should there be some code/settings in config.sys to correct this? at the moment the only code in config.sys for the Z axis is... M569 P2 S0 F5
Help please
Regards, Andy -
@handyandy they are driven by the same driver so theres nothing really you can do.
A stepper motor will move by up to 4 steps when energised.
If E1 is spare you're better off running the second z motor from that and performing gantry levelling in the firmware -
@jay_s_uk Thanks for that.
Could you explain it in more detail, or point me to some documentation covering it? -
@handyandy this should cover you https://docs.duet3d.com/en/User_manual/Connecting_hardware/Z_probe_auto_levelling
i run my prusa in the same way. -
@jay_s_uk Thanks again. I will look into this.
I still don't really understand why the two motors in the in the Z motor sockets don't just move in sync.
Surely the board is designed to manage this? -
@handyandy it is but it wouldn't be my recommended method unless you had some sort of mechanical way of stopping any individual movement. single motor to single driver will always be more reliable
-
@handyandy When you power on the motors they will jump a bit. Which way and how much they jump depends on where they were sitting when they were powered off. They can jump different directions and different amounts, tilting the X axis in the process.
Prusa firmware drives the X axis to the top of the Z axis and a little beyond, with hard mechanical stops positioned so that when both ends of the X axis hit the stops the X axis will be perpendicular to the Z axis. Then it drops the X axis down to print position and it will remain perpendicular to Z until the next time you power cycle the motors.
A single motor driving both screws prevents the X axis from tilting, even if the motor jumps when power is applied.
-
@handyandy I had the same issue and think I have resolved it.
The first thing I did is to put a very noticeable black marking on the top of the motor couplings so I could easily tell if they lost sync. If they ever do (has not happened lately) I can manually put them back in sync.
Another thing I did is a suggestion from @dc42 to slowly power up the motors in config.g as follows
;Sowly power up motors M913 X10 Y10 Z10 ;Set power to 10% M17 X Y Z ;Enable steppers G4 P100 ;Dwell 100ms M913 X20 Y20 Z20 ;Set power to 20% G4 P100 ;Dwell 100ms M913 X30 Y30 Z30 ;Set power to 30% G4 P100 ;Dwell 100ms M913 X40 Y40 Z40 ;Set power to 40% G4 P100 ;Dwell 100ms M913 X50 Y50 Z50 ;Set power to 50% G4 P100 ;Dwell 100ms M913 X60 Y60 Z60 ;Set power to 60% G4 P100 ;Dwell 100ms M913 X70 Y70 Z70 ;Set power to 70% G4 P100 ;Dwell 100ms M913 X80 Y80 Z80 ;Set power to 80% G4 P100 ;Dwell 100ms M913 X90 Y90 Z90 ;Set power to 90% G4 P100 ;Dwell 100ms M913 X100 Y100 Z100 ;Set power to 100% G4 P100 ;Dwell 100ms M18 X Y Z ;Disable steppers.If that doesn't work try boosting the current to your Z motors a bit. One of them may need a bit more current than the other.
