Motoman motor /encoder Ruined?

  • Looking for some help.

    Motoman MPL80 Motor SGMRV-09ANA-YR11

    I swapped encoders and have been informed that I now need two replacement motors with encoders. Once disconnected, they cannot be re-aligned.

    Can anyone confirm? or provide instructions how or a place where re-alignment can be done ?

    Hard to believe 8 tiny screws can immediately result in a $4500 error.



  • SPLights

    Changed the title of the thread from “Motoman motor /encoder” to “Motoman motor /encoder Ruined?”.
  • What were the 8 screws you took out? There should only be 4 that attach the encoder to the motor body. The encoder then pulls off.

    Re-alignment is:

    On the encoder side there is about a 1", metal rectangular piece with a cutout on each end. Halfway down the longer side, along the edge on one side or the other is a triangle.

    On the motor side there is a round piece that has cutouts for the encoder side metal piece to fit into. In the center of it, along the edge of a cutout is a triangle.

    The two triangles align together. The 4 screws go in. The encoder connection is attached and you're ready to power up and re-calibrate.

    Alcohol: The cause and solution to all life's problems

  • Hey!

    Thanks for the reply.

    2 encoders, 4 screws each= 8.

    Yes , no problem remounting with couplings getting properly engaged.

    Swapped 2 encoders, B and T axis. Then wanted to try jogging. After servo on, pulling safety switch, the B axis twitched negative and faulted for wrong direction. Reset and try again, and B twitched in the positive direction and faulted.

    I called Tech service and was advised you can't separate encoders and they wont repair. Must buy factory replacement motor/encoder.

  • Making Progress.

    You were correct in that I did not align the triangles and was 180 out on B. B is now operational via jog.

    T now indicates a Servo Tracking Error 4328. This is the error i had on B that swapping the encoders was supposed to help me diagnose, and now I have good evidence that the encoder now on T is the culprit.

    I'm going to swap them back to confirm. Will Update when done.

    Edited once, last by SPLights ().

  • Well no more progress. Still getting Servo Tracking error T Axis.

    I swapped encoders and B continued to work fine. I swapped amplifiers and B contiued to work fine. I ohmed through the power cable to the motor connector and all good, no phase to phase, no short to ground. I confirmed the brake releases and I can hands on rotate T.

    I'd appreciate if you have any other ideas.


  • Update:

    T power plug and T encoder plug attacthed to B axis motor and T controls operated B motor it just fine. Indicates T control, amp, and conductors are all fine.

    B controls resulted in Servo tracking error when connected to T axis motor and encoder.

  • Sounds like you are now isolated to T-axis motor assembly/mechanical drive. Might as well pull the motor and try to drive it unattached. If you pull, you will have to re-calibrate.

    When you manually released the brake on the T, how did the drive feel when you moved it? Nice and smooth or clunky. May be hard to move if you don't have so type of mechanical advantage.

    Alcohol: The cause and solution to all life's problems

  • I have a tooling fixture approx 18 x 12" that picks up large boxes so I have some leverage to move it when testing. It moved with some resistance but not more than I expected. In terms of smoothness, I could feel individual "pulses" while turning but I took that to be magnetics in the motor or timing belt teeth. Again not more than I expected. Certainly not clunky. I tried moving it with the B centered, and at both extremes. All the same.

    T operated correctly 2 weeks ago and I never once ran into a restriction or encroached on any mechical stops. I do not suspect its a mechanical drive issue.

    Really the only thing done was to swap amplifiers and swap encoders. I can't rule it out but nothing should have affected the mech drive system.

    Could there be some accuracy to Tech service statement that there is a position range between the motor and encoder that needs to be correct?

    I will proceed with pulling motor to try unattached. If it faults, that will tell me its either motor or motor/encoder association ( I know the encoder is OK as it works fine on B)?

    I appreciate your ideas.

  • Update

    Motor pulled, so zero load compared to normal. Jog speed set to slow

    Enabling switch releases brake, T+ starts rotation, but it Faults Servo Tracking Error 4328 T axis

    Reset and pull enabling switch, T- rotates other direction and faults the same.

    Reset and pull enabling switch. Without pressing either T ( simply holding enable) and the motor stays stationary for several seconds, then will rotate a revolution or so and fault 4328

    Thinking there is a necessary correct position of the abs encoder to the motor, and that i have it incorrectly positioned.

    Now to figure out how to correctly position.

    Again, I appreciate any ideas.

  • If I understand fully what steps you have done so far, I'd say the motor is bad. I have seen that same scenario before. I'd try a new motor/encoder assembly.

    Most times when I run into a low hour or out of box servo motor that chatters, it's the servo gains that I need to adjust. If nothing has changed in the software that's not it.

    I looked at the procedures for replacing the encoder and nothing is different than what I described above.

    Alcohol: The cause and solution to all life's problems

  • Thank You 95. Your guidance has helped tremendously!

    I've got a new motor ordered and since it appears I have a few days to wait for receiving, I will try a few more tests.

    Apologies for the length below, but I'll explain my steps up to now..

    I have effectively done nothing to the T motor other than disconnecting and reconnecting the encoder, and I witnessed the motor operating without issue 20 days ago. Lastly, I am confident I have not impacted , crashed , or jammed the axis in anyway.

    I started receiving Servo tracking Error on B and intermittantly a current feed back error 2005 There is not explanation for "2005" but the servo tracking error included SLUBT with the B highlighted. (Tech service said the 2005 indicated the same B axis but I now wonder if its actually pointing at T {5 would be B if I had an E axis, but I dont})

    I did a lot of testing confirming the robot harness, motor connections, and swapping amplifiers to resolve. ( Motoman suggested changing the harness based on age and faults, but if there was an break or a short, I should be able to read it with an Ohmeter, and wasn't),

    Every requested movement of L,U and B axies resulted in an immediate fault for servo tracking error B and occaisionally a major current feedback error 1547. Most all my efforts to resolve were associated with the L,U,B axies as I had not even gotten to trying T. Since L,U movement always maintains B parallel to floor, I repeatedly got the 4328 fault on B whenever jogging L and U.

    Working with Motoman tech service direction, I used the T axis amplifier and circuitry for testing on B. I will say they did NOT recomend I pull off an encoder when I asked (He said "I would not do that as you can get into more trouble", But also did not warn DO NOT SEPARATE encoders or its ruined). Days later, after I told Tech service that I have now separated encoders to test, they provided the information that when they hear that, they immediately direct to replace ( and do NOT offer repair). He stated the factory will dispose of, rather that attempt a fix any motor they understand has been separated from the encoder.

    The only thing I did find was a power cable connection issue where the CN3 module (which carries the phase conductors U,V,W for both B and T axies) was pushed back in the housing and either making no connection, intermittant or poor connection, or perhaps even single phase connection to the B and T motors. ( at the back of the DX100 controller)

    Upon finding the bad connection, fixing it, and fixing a mismatched encoder coupling on B ( my error in re-assembly) my faults have changed solely to Servo Tracking error on T. For tests I have swapped the amplifier and encoder, and circuitry (from B) again, and B continues to operate correctly. T circuitry , when connected to B motor , correctly operates B axis. But when connected to T motor, it faults. Ultimately, I would expect motor failure if any sustained run time was done while the poor connection was occurring. But I rarely attempted to jog T, and when I did, It immediately faulted. There was no prolonged duration with bad power connections.

    Since it worked before, and I really have done little to it other than separating the encoder and replacing it, I'm really doubting it's damaged. Motor/ encoder position is very likely way out of position with regard to where it was when I started. So, while I cannot explain why it would even matter, it's the only thing I have especially with the info from Motoman Tech.

    Today I plan to separate the encoder and advance it in the + or - direction at 360 degree increments and try it repeatedly until it works or I receive the replacement. We'll see if I have any success or condition change. (what's the resolution - 4096??or more?? ugh)

    Watch for an update!

    Thanks again.


  • Finding:

    After lots of testing, the condition that indicated my 4328 Servo tracking error source is actually the rotary position of the encoder when coupled to the motor.

    As a last ditch effort in testing to allow jogging without the fault, I loosened the encoder screws and rotated the encoder to the limits of the space in the bolt holes. The result was improvement to an intermittant fault occurring less often and after only some movements. Removing the bolts and rotating the encoder another "degree" (?), resulted in full operation without fault. I have it temporily held to allow full testing until a fix is completed

    It is assumed that the timing between the motor and encoder is critical and that I have somehow rotated the rectangular coupling flange on the motor shaft, or the encoder shaft and that the "alignment" or timing is now off ( by perhaps a degree). I have not yet gone into the coupling to see if I can resolve or reset it to the needed position.

    I haven't devised a way to move it precisely and/or easily in terms of how much to turn it or even how it's attached, ( via setscrew or press fit or even keyed?).

    Perhaps there is a software adjustment to tune the motor to the encoder? making physical adjustment un-neccessary?

    Thank You


  • Thank you for the complete write up. Keep us posted. I have not had this problem before. If I have swapped 1 I have swapped 100. The current design (Oldham Slide) has been around since the DX100. Far easier than the NX100 which had a coupling with a pin on the motor side and a dimple on the encoder side.

    Alcohol: The cause and solution to all life's problems

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