I have a KM-3, with Ultimax 2 controls. I am having trouble with the z-axis. Here are the symptoms:
- On occasion, the z axis will head at the current speed towards + or - Z, well beyond its commanded position and will then stop and report a "Motion Error on Z axis." If, for example, I turn the jog wheel just a little in the - direction, the spindle will continue down until it faults.
- The problem seems to be temperature dependent (happens on warm days)
- Resetting (Manual, Power, Reset Servos, Start) will bring things back on, but it will immediately fault again at the next command. My only hope is to shut down for the day and try again on a cooler morning.
Here is what I've done in trying to troubleshoot the problem:
- I observed the tachometer signal coming from the z-axis encoder using an oscilloscope. I get the same signal at the encoder connector (blue and white wires) and at the DB-25 connector on the Z-axis card (pins 25 and 12 on PC1-A1), I'm not sure what the spec is for the encoder, but I do see a ~5V square wave that increases in frequency with increased Z-axis speed at both places (so I don't thing there is a cabling problem)
- I can see the Marker signal on the green wire at the encoder (the z-axis usually calibrates correctly--but not always)
- I have swapped the dual axis board (with the z-axis) board with a spare board that I have. Same behavior.
- I have swapped the Z and X servo boards (I don't have a spare). Same behavior.
At this point I'm out of ideas. I assume that the problem is that the digital logic (i.e., dual-axis board) is commanding a movement, the servo board is creating a voltage on the motor, but the encoder signal is not getting back to the digital logic to close the loop. Based on that simple understanding, it seems that I've tested or swapped all of the relevant pieces. What am I missing?
Any help would be much appreciated,
,
-joel