Replacing a servo driver

[LOTT]

I had the X axis driver fail on an Intertech QuickTurn 42-9LSS CNC Lathe. It's a weird Taiwanese machine that's an orphan, and I knew when buying it that the day may come when not having support would bite me; it was cheap and has done very well, certainly paying for itself, but that day of failure is upon us.

The drive in question is a Mitsubishi MR-J2S-100A. I bought a "used & tested" replacement off ebay, and set all the parameters to match the old one. The alarm that had been on is now gone, but as soon as I try to jog X there's a "X Axis Loss Pulse" alarm and it's not moving. The servo is locked up (holding it's position, whatever the correct term is), so something is happening, just not everything that should be going on.

Any suggestions?

 

[BugRobotics]

Maybe check encoder pulses are getting to the drive? Anyway to communicate to the drive to verify?

Also make sure there are no dip switches that need to be set.

 

[LOTT]

There don't seem to be any dip switches, I pulled the case off to look for any. How would I check that encoder pulses are reaching the drive?

 

[BugRobotics]

There don't seem to be any dip switches, I pulled the case off to look for any. How would I check that encoder pulses are reaching the drive?

Easiest way would be to verify with a scope. Is this a direct replacement (same PN)?

 

[BugRobotics]

Just checked the manual for that drive. Are there any errors being displayed on the drive itself?

https://dl.mitsubishielectric.com/dl/fa/document/manual/servo/sh030006/sh030006j.pdf

 

[Vancbiker]

Is the encoder cable plugged into CN2 on the drive? Since all 4 connectors on the drive are the same, it is possible to fit a cable to the wrong position.

 

[Vancbiker]

Also, what alarm number shows on the drive itself (Sounds like the alarm in your first post is from the CNC screen, not the drive)? What control is on the machine?

 

[LOTT]

Yes on direct replacement, and I don't have a scope but will get one if needed.

All the drives show alarm E-6 until they are homed, so this one stays on E-6.

 

[LOTT]

Also, what alarm number shows on the drive itself (Sounds like the alarm in your first post is from the CNC screen, not the drive)? What control is on the machine?

Edited- the control is a Syntec, do you need a model number? I left the shop so won't have it until tomorrow.

 

[LOTT]

Is the encoder cable plugged into CN2 on the drive? Since all 4 connectors on the drive are the same, it is possible to fit a cable to the wrong position.

Yes, I took a bunch of pictures before pulling anything apart. And Y, Z, and Z1 are all the same so it's easy to dummy check X against.

Unless this new drive has ports in different positions, didn't even think to read the actual labels...

 

[BugRobotics]

I'm assuming a wiring error as well. Looks like the control is commanding position and not seeing the appropriate feedback.

 

[Vancbiker]

E6 is servo emergency stop. I don't have access to any Syntec info, so not sure how they interface to the drive. Gut feeling is that they are using the drive in position mode with step and direction command. If that is the case, double check parameters 0 and 21.

Any chance of swapping drives with a know good unit to confirm that the encoder signal is good?

 

[BugRobotics]

E6 is servo emergency stop. I don't have access to any Syntec info, so not sure how they interface to the drive. Gut feeling is that they are using the drive in position mode with step and direction command. If that is the case, double check parameters 0 and 21.

Any chance of swapping drives with a know good unit to confirm that the encoder signal is good?

I was looking in the servo drive manual and it states (I think I'm reading this correctly) that E6 means the e-stop has been disengaged. Which would be a good sign that the drive is at least alive enough to respond to an external signal.

 

[Vancbiker]

I was looking in the servo drive manual and it states (I think I'm reading this correctly) that E6 means the e-stop has been disengaged. Which would be a good sign that the drive is at least alive enough to respond to an external signal.

It's actually the opposite. EMG is normally "on". When it turns off, the drive is in the e-stop condition. This is done so that a failed circuit will e-stop the drive rather than a failed circuit preventing the drive from being placed in e-stop.

 

[LOTT]

E6 is servo emergency stop. I don't have access to any Syntec info, so not sure how they interface to the drive. Gut feeling is that they are using the drive in position mode with step and direction command. If that is the case, double check parameters 0 and 21.

Any chance of swapping drives with a know good unit to confirm that the encoder signal is good?

Z and Y use the same drive, I could swap them around to see if the fault stays with the axis or moves with the drive.

I hesitate to blame a wiring problem because the new drive is behaving differently from the old one, but you guys (Vancbiker in particular) have pointed me in the right direction before so I'll try whatever you suggest.

 

[BugRobotics]

It's actually the opposite. EMG is normally "on". When it turns off, the drive is in the e-stop condition. This is done so that a failed circuit will e-stop the drive rather than a failed circuit preventing the drive from being placed in e-stop.

Thanks for clarifying, I got confused by the wording in the table on 10-14 (EMG OFF) but on page 4-5 it is described nicely as you stated.

 

[BugRobotics]

Z and Y use the same drive, I could swap them around to see if the fault stays with the axis or moves with the drive.

I hesitate to blame a wiring problem because the new drive is behaving differently from the old one, but you guys (Vancbiker in particular) have pointed me in the right direction before so I'll try whatever you suggest.

I'm flying blind as I've never messed with this drive or control. Happy to try and help though. These systems are all trying to do the same thing so not too crazy to troubleshoot.

 

[LOTT]

Ok, I'm back at the shop finally. The place that sold me the "used & tested" drive swapped it out with another one. This time is acts just like the others do, as far as clearing the E-6 alarm when firing the machine up, but when I try to jog it won't move and comes back with "X AxisLoss Pulse" and "X AxisFollowing error exceed" messages.

So how do I determine what is failing? Start swapping drives around to see where the fault ends up?

 

[Vancbiker]

It appears then that the first replacement drive was probably bad leading on a bit of a troubleshooting detour. The alarms point very strongly toward an encoder problem. Checking that was mentioned earlier in the thread....

 

[BOB-OO]

Did you turn the number screw to ?6? on initial power up, then move it to the number required by the controller? On a Mazak w Mitsu drives, that initialization process is required every time you change a drive. I would find the manual or call Mitsu, they are awesome and support their products.