Denford Software & Machines

On homing the Z axis the stepper motor trys to step but just judders until the emergency stop is pushed. We have cleaned the leadscrews and bearing housings, although when we turn the leadscrew by hand the bearing feels quite rough. Before we strip down the unit 1) Are the bearings sealed units? 2) Could the symptoms be caused by other hardwear / firmwear faults? 3) Can the Z axis unit be stripped easily without causing registartion errors. Thanking you in advance.

Does this machine have a gold coloured brake on the Z axis motor ?

Have a look at this topic for a possible cause:
viewtopic.php?t=456

No, have read that post but it doesn't seem to apply. The stepper motor connects to an aluminium flexible drive but it is an integral unit, black with silver ends square in section, have tried to remove stepper motor for a closer look but the six cable plug does not want to unplug from the motor, is it fixed in any way? Didn't want to force it. Used your magic switch to enable jog which it did half heartedly, better down than up! Wonder if is the motor. Hope this helps.

I suppose if the axes are binding, then you'd get this half-hearted jogging.
But you may also get it if:
the stepper driver electronics are failing / overloading (maybe due to motor winding failure)
the motor cables have broken or come loose
the motor itself is damaged.

I'd undo the round silver coupling from the motor (a couple of cap-head screws in the side), and run the motor on its own to determine if the fault is with the axis slide, or with the motor / cable / drive.
You won't have any problem loosing position, as the home position is set purely from driving off the home limit switch - the system does not know the rotor angle of the stepper motor at all - just the number of steps it has sent to it.

Hope this makes sense

Martin,

What machine type are you running?

If its a router then most of them other than the very early ones have a brake fitted on a shaft extension on the oposite end to the coupling.

As Admin says if you dont have a brake then it could be an axis drive problem.

If you open up the control you will be able to see the Denstep card. see link below.

The three stepper motors wire into the control card and it is possible to swap 2 axes over to see if the fault transfers.


https://www.denfordata.com/projectimages ... _guide.pdf

It sounds to me that it is a brake in the z axis motor cable. The best way to check it is to use a meter to check the contiunity of both pairs at the drive. guess you need to see about 2 ohms accross either pair.

What is the purpose of the Z brake?

The Z axis stepper motor stops the Z axis dropping when the E Stop is pushed in or there is no power to the machine.There is no counterbalance so the weight of the Z assembly & Spindle motor can cause the axis to drift down when the stepper motor is not energised.