Need Help!- Y dac overflow

[fullbore]

This machine has been nothing but problems. I purchased it about 6 months ago and have now changed a mother board , drive board, power supply( logic) and the crt is out. The machine is a series 2 dx

So the prob now is that I get a dac y overflow. I was running the machine for about 2 weeks after the last fix and its down again.

I was in the middle of a simple face event when it stopped after completing a x move. I have flopped the drives same problem, I flopped the motors same problem.The Bmdc loads fine red lights on and off when they are supposed to be. The readout is working properly when I move the machine manually. I have changed the aux and axs bob cards too same problem.

Single man shop this machine is killing me.

Thanks for the help

[machintek]

A DAC overflow means the control sent commands to move an axis but did not see movement. Either it did not move or did move and the encoder count is not being seen by the control.
Based upon what you did, it seems the drive is not receiving a command to move. A open armature cable would give you a axis drive fault.
Either a bad connection in the command line or a lack of output from the BMDC.

George

[fullbore]

Thanks for the info, I dont think there is much else that is in the loop besides the bmdc and the cable right? Can I test the output from the bmdc? The machine moves it just hits the hard stop in the y axis. I have a new cable I will install it to take that out of the possibilities.

[machintek]

If the axis moves but does not stop (but counts) the fault may be in the marker pulse circuit. This is used for homing. Without seeing it, the machine hits the end of travel, encoder pulses stop and you get the DAC overflow. Since you swapped the motor and AXSBOB, the probable culprit is the cable followed by the BMDC.

George

[ppascuzzi]

Does the table slow down as it nears the home position? It should slow down as soon as it hits the reference home switch. If it doesn't see the reference home switch it will never look for the z channel pulse of the encoder (home position pulse) and will run into the hard stops. If it is crashing into the hard stop in the positive direction (normal home direction) check and make sure that the dog is actually physically tripping the switch and that the switch signal is getting back to the control.


If the table is on the reference home switch when you try to home it travels in the negative direction until the switch is cleared and then will move in the positive direction to close the switch again and start looking for the "z" pulse on the encoder.

If the reference home switch is stuck on it will continue to travel in the negative direction until it hits the negative direction hard stop. If this is the case check the switch and wiring for the switch. if the switch and wiring are good it would be the auxbob (which you already swapped) the BMDC or associated wiring. Check the ribbon cables to make sure they are fully seated


If the table moves in the positive direction until it hits the hard stop a simple test to perform is to manually move the table back in the negative direction until you can physically hold the reference home switch down. Now power up the machine and while holding the switch down try to home the mill. If the table moves in the wrong direction release the switch, the table should change directions. (watch where your fingers are as I suspect you like having them attached to your hand)) If the table does this the switch is electrically good. Now just check to make sure the table is actually able to physically close the switch. If the table doesn't switch directions then it could be a bad switch, cable, auxbob, ribbon cable or bmdc. You can use a voltmeter to check the cable. Make sure the ribbon cables are fully seated (it's rare for anything else to be bad with them) The auxbob you already swapped. If all that is good and the mill still fails this simple direction test that only leaves the BMDC board. The BMDC is not cheap so if you get to the point where you think it is the problem come back here and ask and I'll see if I can find any info in my old notes on checking it out or call EMI and see if they will help you test it.

If that all checks out good then you are back to the encoder, encoder cable, axsbob board (or axis I/O board depending on the version of EZtrak) or bmdc board or associated wiring.

You can try swapping the x and y motors to see if it is the encoder. (oh I see you already tried this)

If it is not in the encoder check the wiring and cable to make sure it is not broken. Also check the connectors on the BMDC board and the Axsbob (or axis I/O) board, make sure they are fully seated. As the Axsbob board is basically just a break out board that just takes the signals from the encoders and dumps them right onto the ribbon cable it is rare for it to be bad.