Z axis motors spin too fast

When the auto levelling has finished, The Z axis motors spin too fast and jam to drop the J head too correct hight before printed.

Please help

---

Printer: Prusa i3
FIRMWARE: Marlin_v1.1
North east,UK

what do you mean the axis motor spin too fast?you can limit maximum z speed in firmware

video of problem

---

Printer: Prusa i3
FIRMWARE: Marlin_v1.1
North east,UK

Check the homing feed rate in the firmware. I;m not sure if this is the cause of your issue, but I'm assuming it's homing at this rate after auto-leveling.

#define HOMING_FEEDRATE {50*60, 50*60, 4*60, 0} // set the homing speeds (mm/min)

4*60, the default, is too fast for my i3. It works better at 3*60 (these are mm/min, so it's either 4 or 3 mm/sec).

---

[3DKarma.com] - suppliers of quality, affordable 3D printer kits and filament for the UK market.

mine used to do the same!
3 possible solutions:

1. slow down to max 3mm/sec movements in Firmware

2. adjust the voltage slightly. When I gave my Z-motors a little more voltage, they did not do this anymore

3. you may want to re-check if both sides are at exact! same height - measure with a caliper - (rather adjust for any imbalance via the bed )- because you do not want binding on the Z-axis linear rods. Some lubricant on the Z-axis`s threaded rods may also help quite a bit.

for me all 3 steps mentioned above did solve the issues permanently.

Alex

If you have a multimeter
set the Z-motors vref at about 0.85 - 0.95 I did adjust mine to 0.85 and motors are not even getting slightly warm.

reduce the maximum speed of z axis to 3mm/sec.
also reduce the homing speed, it is good while you debug the machine. in case of endstop failure the motor might be too fast and break things.