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Topics - justinwol

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General Mach Discussion / Odd problem: Z axis stalls X or Y or both
« on: March 16, 2013, 10:10:09 PM »
I've been trying to solve an odd problem for awhile and finally decided that I need some help from the forums as searching for this specific issue has come up dry.

Here is the problem:

When jogging the X or Y axis at 100% rapid (1500 mm/min), the axis I was jogging (X or Y or both) will stall the moment I begin jogging the Z axis. I can simultaneously jog the X and Y axis without any stalling, but I cannot jog X with Z or Y with Z without the X or the Y stalling. The Z axis never stalls, it only causes the X or Y or both to stall. The Z axis also only stalls the other axis if it is jogged after the X or Y is already jogging. If the Z axis is jogging first, then the X and Y will not stall when they are jogged. If the X or Y axis are jogging first, then they will stall the moment the Z axis is jogged.

The only solution I have found is to reduce the rapid speed to 500 mm/min. No stalling at all occurs at this speed.

I have done as extensive testing of the hardware that I am capable of and as I eliminated each piece of hardware I eventually arrived at Mach 3's handling the Z axis. This is where I am at now and am no longer able to troubleshoot this on my own.

Here is what I tested:
1. PSU and Mechanical axis. X and Y jog simultaneously without stalling. This means PSU at least has enough power to simultaneously jog 2 axis. It is a commerical 40V 12A PSU driving 130oz steppers. This remains true if I change the motors to drive any combination of the 3 mechanical axis of the machine. Stalling is not specific to mechanical axis. The stalling also happens when the motors are attached to nothing.
2. Motors. Swapped Z axis motor with X and Y, problem stayed on the Z axis output and did not follow the Z axis motor to the other axis. All motors caused the stalling when attached to Z axis output. None caused stalling when attached to X or Y axis outputs.
3. Drivers. Basically same as above. Problem followed the Z axis output. Whichever driver was attached to the Z axis output, caused the stalling. I've reduced the microstepping to 1/2 step, but still stalls.
4. Breakout board. This is also same as above. Problem followed the Z axis output. Which ever pins were programmed as the Z axis caused the stalling. For example, originally pins 8/9 where programmed as the Z axis output in Mach 3 and 6/7 were the Y axis. If I physically swap the Z pins with the Y pins on the breakout board - the problem stays on the Z axis output, meaning that when I jog the Z axis, which is now the mechanical Y axis, it causes the others to stall. I can jog Mach 3's configured X and Y axis, which are now the mechanical X and Z axis simultaneously without stalling. If I keep this setup and change the pin configuration in Mach 3 so that 6/7 are now the Z axis outputs (which were the Y axis outputs) and pins 8/9 are now the Y axis outputs (formerly Z axis outputs) - the problem follows the Z axis output. When I now jog the Z axis on pins 6/7 it will cause the other axis to stall, but I can jog the Y axis on pins 8/9 with the unchanged X axis simultaneously without stalling.

In summary, the Z axis output from Mach 3 was the cause of the stalling no matter what combination of breakout board pins, motors, drivers, cables, wires or mechanical axis were attached to it.

The part that confuses me is that I can solve the problem by reducing the rapid speed. I can rapid the X and Z axis at 2000 mm/min and the Y axis at 3000 mm/min with minimal stalling individually. 1500 mm/min is a conservative and very reliable rapid speed for the machine. To reduce it to 500 mm/min is painfully slow.

It appears to be caused by Mach 3's Z axis output somehow and I'm not sure how to go about troubleshooting this. I'm also ready to do further hardware testing, but I've exhausted all that I know of.

Does anyone know a solution or have suggestions?


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