Semco cnc mill problem

  1. scottmk1

    scottmk1 Forum Supporter

    Messages:
    1,257
    Location:
    Scotland
    I have a Semco CNC bed mill, it has had a GSK 983 controller fitted but still uses the Anilam servo drives and boards. The wiring looks like a mess unfortunately, should have checked that before I bought it but there you go.

    Anyway recently I fired it up and get alarms about the Z axis detecting device pulse encoder, and the Z axis motor is constantly turning. See the alarm below:

    DSC_0787.JPG

    Where do I start with trouble shooting this?

    Here is the cabinet on the back of the column:

    DSC_0799.JPG
     
  2. skotl

    skotl Forum Supporter

    Messages:
    6,757
    Location:
    Edinburgh, UK
    Do you have an oscilloscope, or a frequency mode on your multimeter, that you could use to see whether you're getting pulses from the encoder?

    Also - is it possible to swap the pugs for the Z axis encoder with one of the other encoders and see whether the problem stays on Z or moves to the other axis? That would confirm whether you have a problem with the encoder and its wiring or on the board.
     
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  3. Hood

    Hood Forum Supporter

    Messages:
    10,309
    Location:
    Carnoustie, Scotland
    First step is look at the encoder on the motor (or ballscrew) and check all looks ok.
    Not sure if it is a Step/Dir control or not, if it is then the encoders will almost certainly go to the servo drives, if not then they will go direct to the control, trace the wire and check all is ok.
    If you have a scope you could check the signals when they enter the drive/control.
     
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  4. Hood

    Hood Forum Supporter

    Messages:
    10,309
    Location:
    Carnoustie, Scotland
    Looking at the pic there doesn't seem to be much in the way of connections to the servo drives so I am more inclined to think it is analogue command and the encoders will go direct to the control.
     
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  5. scottmk1

    scottmk1 Forum Supporter

    Messages:
    1,257
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    I don't have a scope unfortunately, but I will check my meter and see what it can do.

    Currently swapping the boards over and it's apparent that the Z axis one has been out before!
     
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  6. Hood

    Hood Forum Supporter

    Messages:
    10,309
    Location:
    Carnoustie, Scotland
    Often just cleaning the contacts can help.
     
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  7. scottmk1

    scottmk1 Forum Supporter

    Messages:
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    OK so the fault doesn't transfer with the board so I've whipped the servo motor off and I'll check the contacts. DSC_0805.JPG
    DSC_0806.JPG
     
  8. Hood

    Hood Forum Supporter

    Messages:
    10,309
    Location:
    Carnoustie, Scotland
    Motor looks like it may not have an encoder, no mention of it on the data plate. Check to see if there is an encoder on the ballscrew.
     
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  9. scottmk1

    scottmk1 Forum Supporter

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    OK will do. There's no obvious sign of one so I assumed it was integrated into the motor.
     
  10. Hood

    Hood Forum Supporter

    Messages:
    10,309
    Location:
    Carnoustie, Scotland
    It may be as I have just looked at the SEM manual and the end cap on yours does look to be extended more than the one in the manual.
     
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  11. scottmk1

    scottmk1 Forum Supporter

    Messages:
    1,257
    Location:
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    Well I can't see anything on the ballscrew the X axis motor does have an extra bit on the end though?

    DSC_0807.JPG
     
  12. Hood

    Hood Forum Supporter

    Messages:
    10,309
    Location:
    Carnoustie, Scotland
    Have a look in your control manual and see where the encoder inputs are. Trace them back and they will go to the encoder or servo drive. The pic of the servo drive makes them look like they are analogue amplifiers as there are not a lot of wires going to them so I am guessing the encoders will go direct to the control.
     
  13. scottmk1

    scottmk1 Forum Supporter

    Messages:
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    Location:
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    Well I'm guessing this is the bugger?

    DSC_0808.JPG
     
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  14. Hood

    Hood Forum Supporter

    Messages:
    10,309
    Location:
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    Yep, Renco encoder, maybe even info there in the lid as to what colour is what.
     
  15. Johnnybravo Member

    Messages:
    927
    Location:
    Northiam
    First thing I would do would be take the brushes out the servo motor and blow all the carbon dust out. Encoder cannot do its job if commutator is clogged up with dust,as it will over shoot the mark constantly. Something I learnt from the Prototrak mill....
     
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  16. scottmk1

    scottmk1 Forum Supporter

    Messages:
    1,257
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    OK so I found a loose wire in the control panel, along with a couple of pikey connections. Sorted that and it's still the same.

    DSC_0810.JPG

    DSC_0811.JPG

    Back home now to have a look at the manual
     
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  17. scottmk1

    scottmk1 Forum Supporter

    Messages:
    1,257
    Location:
    Scotland
    Thanks I'll try that later
     
  18. scottmk1

    scottmk1 Forum Supporter

    Messages:
    1,257
    Location:
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    OK, took the brushes out and blown it out with the air gun, it seemed to make an improvement for 10 minutes then went back to the way it was. The brushes are fairly worn, so I'll change them, also got the manual here so I'll get familiar with the wiring diagram!
     
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  19. scottmk1

    scottmk1 Forum Supporter

    Messages:
    1,257
    Location:
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    OK here is wiring diagram inside the motor, I've traced all the wiring for it back to the source, here is the diagram:

    DSC_0815.JPG

    So from the encoder, the red and black wires each split into two with red and black going to a multi plug for the X axis and Y axis.
    The white, green and brown all go to this device:

    15851474583527216860429896077948.jpg

    From that device all wires go to the Z axis port on the back of the control panel.

    The two small red and black wires from the motor go to the Anilam card for the Z axis, as do the heavy wires, and finally the ground obviously goes to the ground point in the cabinet.
     
  20. scottmk1

    scottmk1 Forum Supporter

    Messages:
    1,257
    Location:
    Scotland
    I've cleaned the crap out from in between the commutator segments on the Z axis motor and put it all back together, it's now running even faster than before, when it should be stationary! Maybe the commutator is goosed? How can I test the encoder with a multi meter if at all?
     
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