Denford Software & Machines

Compact 1000
July 2007
VR Milling v5.19

The Z axis stalls randomly, this usually happens in the up travel.
We thought it might be the brake. We removed the brake from the stepper motor and the problem still exists.
We removed the Porter Cable spindle motor. Dissasembled, cleaned and lubed the lead screw, ball nut and the rails with the spray silicone.
The lead screw turns smoothly in the ball screw and the carriage slides smoothly on the rails, by hand.
The resistance across the 2 pairs of wires to the stepper motor measure 2 ohms on each pair.
The lead screw and rails look good, there are no nicks or damage to them.
The Z axis still stalls, but if I help it by turning the coupler , the Z will continue on.
Is there a way to test the stepper motor?
What else should we look at?
The machine has been working very well before this.

Just a thought - could it be a broken stepper motor wire? I know you have checked the stepper motor winding resistance to be 2 Ohms which seems fine, but i was wondering, if when the Z axis moved it could cause a broken wire to temporarily break connection and cause what appears to be the Z axis stalling ?????

Another thing to try would be to connect the Z motor to say the X axis drive output - the orange plug coding pins will need removing.

Carefully try plugging the Z axis connector (you will need to remove the small black indicator from the orange connector) into the Y or X output on the control card to see if issues persist.

This will proove a drive fault (if Z works ok when connected to X) or
motor/wiring fault (fault remains).

(You'll have to do the secret home in VR5 and be aware that wherever the axis is positioned when powered on, will be what it considers home position - so you may not be able to jog UP because of software limits)

Vibration and movement could be causing the cracked wire to make and break contact as it is flexing. Stepper motors rarely go bad; it is usually the wires or the control card that go.

I have realigned the motor and lead screw/coupling 3 times, per our last discussion, and after each alignment the axis homes fine and we can cut a car for about 10 minutes before the axis fails. Remember, the motor still has power to it all the time, it just starts growling and stops moving-but growls, or even drops...it still has power to it. Then, when you attempt to home it, again, it just growls and won't move. However, sometimes I can push up the carriage, i.e., assist the motor, and it will move. I can't find any place where it is binding. It will cut very smooth for a time tranversing at least 75% of the Z axis, no apparent binding anywhere, but then just stop articulating in Z, set still and growl.

Also, the motor and brake feel very hot when the axis stops and will not pull up or when it even slips down and cuts the car in half almost.

This could be a fault with the drive or the motor.

Have you tried another next move?

If the direction or clock are not switching correctly you would get these symptoms.

It is normal for the motor and brake to get hot.

Have you tried running EasyUpgrader to check you are running the latest Firmware?
Also update VRMilling to the latest version.
I think the latest version on the website is 5.26.