[uspl]

Hi all

Issue:
Long standing mill x/y/z, now adding a 4th axis.
When I power up the BOB all is good, stepper motors startup and control the axis as expected including A-axis
I can home the machine and motors behave except no "homing" from A-axis
Jogging all fine on x/y/z but as soon as I jog A-axis the motor goes slack and I can freely turn it by hand. Small vibrations felt on the motor but no apparent movement.

Config:
Mach3 3.043.066 on Windows 7 32 bit
Smoothstepper USB driving KTA-205 4 axis BOB, same physical kit for years
3:1 belt drive reduction on a 200 step motor, 1/2 step microstepping on a M542H Chinese knockoff driver
A-axis tuning set to 3.333 steps per based on 200 steps x 2 for the microstep x 3 for the driver reduction = 1200 / 360 degrees = 3.333
A-axis angular ON
360 rotation ON
Rotational soft limits ON
Softlimit Amax = 360, Amin = -360
Toolpath axis of rotation = X
Axis rotations ON

Been driving me nuts for a week now, any thoughts ?

Thanks

David

[awerby]

What happens if you turn the rotational soft limits off? Unless you've got a homing switch set up on the 4th axis, you can't expect it to find home, and arbitrarily limiting its motion with soft limits doesn't seem too useful. Otherwise, it might be something going on with the driver. See what happens if you turn everything off, letting the caps drain before disconnecting anything, and switch the leads from an axis that's working okay to A, putting the A axis leads to it.

[uspl]

What happens if you turn the rotational soft limits off? Unless you've got a homing switch set up on the 4th axis, you can't expect it to find home, and arbitrarily limiting its motion with soft limits doesn't seem too useful. Otherwise, it might be something going on with the driver. See what happens if you turn everything off, letting the caps drain before disconnecting anything, and switch the leads from an axis that's working okay to A, putting the A axis leads to it.

Well.....

I wired the driver for the A-axis into the BOB pins for the Z-axis, same result.
Looks like my eBay driver is the source of the issue.

Got any suggestions for a good replacement, 42v PSU, 3.2A?

Thanks

David

[RCaffin]

Gecko 203V
Mfr warrants them as indestructable.
I use one on my A axis too.

Cheers
Roger