Y axis runaway

[damelman]

I have a YCM-30 Supermax with a bandit 3 control. On power up the Y axis
rapids towards the column (-Y). The soft and hard travel limits have no effect on the movement, only pushing the E stop stops the travel. When the E stop is released the motion resumes.

To verify that the driver board was not getting a premature run command, I unplugged the y axis ribbon cable, then jogged x and z to the middle of their travels. The X and Z axis functioned normally so I pushed the E stop then plugged the y axis driver ribbon cable into the X axis.

When I released the E stop the Y axis took off again at a MUCH faster rate! I then tried to plug the X axis driver ribbon cable into the Y axis but it was too short. I then plugged the y axis ribbon cable into the Z axis. When I released the E stop button the y axis ran in a + Y direction.

Finally I plugged the Z axis ribbon cable into the Y axis and when I released the E stop nothing moved. I jogged the Z axis by pushing the Y axis hotkey and it moved a little then a lag error fault occured. I put the X and Z axis ribbon cables in their normal location and once again those two axis ran normally.

I removed the Y axis driver board. Part NO: 214-076 11 20 AMP DC Driver
any one have a schematic? I'm a novice when it comes to power electronics but I think I may have some bad power transistors.

[bharbour]

I don't think it is bad power transitors. If it were bad power transistors, it would always move at maximum speed in the same direction when the EStop is released, whether the ribbon cable is plugged in or not. I am not familiar with the Supermax stuff so I don't know exactly what is routed over the ribbon cables.

My suspicion is that you have an encoder failure, either wiring or maybe the encoder itself. The reason I think this, is that when you plugged the Z axis ribbon cable into the y axis, everything sat stationary until you jogged the Y axis. With no feedback a servo will sit stationary until something generates a difference signal (jogging the axis) and then it took off. With no feedback, the servo never knows that the mechanical system has moved past the requested new position. Why you don't get similar behavior with the Y axis hookup, I am not sure. It may have to do with what is route encoder, it would be a good idea.

Are the driver boards the same part number for all the axes? You might be able to swap them, but there may be other reasons that this would not work. Someone really familiar with the Bandit 3 hardware would have to answer that.

Good Luck,
BobH

[damelman]

Thanks Bob for your insightful reply. All three boards have the same part number, so I will swap the X and Y axis boards then see what happens.

[damelman]

Here is a photo of the driver board in question

[damelman]

On saturday I removed the X axis driver board and installed it in the Y axis position. I then reinstalled the original Y axis driver board in the X axis position. The control then ran flawlessly for six solid hours.

Today when the machine was powered up the Y axis once again took off.
the servo motors have a 500 line encoder as well as a 7 volts per 1000 rpm
tach. So my next step will be to check connections in the controller,then I will swap the X and Y axis motors to see if the problem moves to the X axis.

[Helix60]

If you have the instalation manual for the Bandit III controler. You can go through the drive section and retune the Y axis. Might help some. I recently re did mine and it is quite a bit more accurate in circular arcs.

Regards,
Heli

[vger]

I had an intermitant runaway issue on a turret punch once. After swapping controlers around, swapping motors around, and replacing an encoder... the problem turned out to be the cable to the encoder.