1995 Haas VF-0 X and Z axis jump an inch and I get a Over Current Alarm
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    Default 1995 Haas VF-0 X and Z axis jump an inch and I get a Over Current Alarm

    Hi Guy's,

    After some advice. I bought a used Haas with electrical issues very cheap and have cleaned 20 years of grime out of it and am in the process of getting it going again. I found a failed relay on the SDIST board and a rectifier diode and a couple if dead FETS on the servo amplifiers. The amps test ok on the bench with a fake PCM signal fead into pin 1 on the connector.

    I have also stripped and cleaned the z and x axis motors and replaced bearing and brushes. To do this I removed the encoders.

    I now have the machine back in one pice and the Y axis with single axis home ok.

    Where I jog the X or the Z axis the axis jumps about 1 inch and then I get over current alarms.

    So questions:

    Is the encode phased with the amateur of the motors. They didn't go back on in the same angle?

    Maybe the motors have demagnetised and they are taking excessive current. Do Electro-Craft sell replacements as Haas are out of stock.

    Thanks,

    Ian

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    Quote Originally Posted by slipalong View Post
    Hi Guy's,

    After some advice. I bought a used Haas with electrical issues very cheap and have cleaned 20 years of grime out of it and am in the process of getting it going again. I found a failed relay on the SDIST board and a rectifier diode and a couple if dead FETS on the servo amplifiers. The amps test ok on the bench with a fake PCM signal fead into pin 1 on the connector.

    I have also stripped and cleaned the z and x axis motors and replaced bearing and brushes. To do this I removed the encoders.

    I now have the machine back in one pice and the Y axis with single axis home ok.

    Where I jog the X or the Z axis the axis jumps about 1 inch and then I get over current alarms.

    So questions:

    Is the encode phased with the amateur of the motors. They didn't go back on in the same angle?

    Maybe the motors have demagnetised and they are taking excessive current. Do Electro-Craft sell replacements as Haas are out of stock.

    Thanks,

    Ian
    Is the "Y" motor untouched but working? Have you tried using an Oscope to check relative encoder/armature signatures? And does the Y rotate properly when subbed into the X or Z drive cable?

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    Quote Originally Posted by Milland View Post
    Is the "Y" motor untouched but working? Have you tried using an Oscope to check relative encoder/armature signatures? And does the Y rotate properly when subbed into the X or Z drive cable?
    No I haven't tried that. Ive tried swapping the servo amplifiers over and problem remained with the motors. Are you thinking the PCM signal from the MOCON is high and not producing PCM? So when the axis is enabled it 100% on and caused an over current?

    When I swapped the servo's I kept the Z axis motor with the Z axis mocon input so that would make sense.

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    Sorry I cannot be of more help.. but looking to learn from this one. How or what did you use/do to push a PCM signal on pin 1?

    TIA.
    CG.

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    First guess is the parameters are wrong. Does the table jump the wrong way when you jog? If so then try changing the REV ENCODER and REV POWER parameters.
    How did you clean the motors? If you blew the carbon out then the motor is probably shorting in the windings. You have to wash the carbon out of the windings with the motor on end. Whatever you use cannot dissolve the insulating varnish on the wire.
    You can buy brushes and holders aftermarket VF-1 parts - carbonbrush.com holder BH187-58, eurtonelectric.com brush 1110024

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    Quote Originally Posted by slipalong View Post
    Ive tried swapping the servo amplifiers over and problem remained with the motors.
    Did the working motor work on other drives?
    Is problem following axis wire harness?

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    did you mark the motor bodies in comparison to the back caps and which side faces the back?. I have seen people take DC motors apart, and not mark them before disassembly. this will cause a phasing issues and motor run away. this would be my initial guess without more information.

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    One note on plugging a different axis cable to check if it is servo/cable or internal, copy all the parameters for each axis first then replace the parameters on the axis you are moving the servo to with the parameters the servo came from.

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    Hoss,

    this sounds interesting. So you are saying the brush / commutator needs to be in phase with the magnets in the body? There are 4 magnets and 4 brushes so I didn't consider any phasing. I have run the motors on 30vDC and the axis move slowly but they do move.

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    I used a simple 555 timer to generate the PCM signal.

    so the pins on the 6 pin connector from the mocon board seem to function as below:
    1 some sort of sync. 20uS period
    2 drive enable
    3 PCM and direction (high with low pulses in one direction and low with high pulses in the other)
    4 5 Volts
    5 Overload
    6 ground

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    My VF-2 behaved like that when it lost the servo gain parameters. I re-entered them from hardcopy, and it's been fine ever since.

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    Pins 4&6 are 5V and GND for the optical couplers. Pin 5 is the FAULT output. Pins 1,2&3 control which leg(s) of the full bridge are conducting.
    Q1 is the lower right
    Q4 is the upper right
    Q3 is the lower left
    Q2 is the upper left
    IC39 connects to pin 1
    IC34 connects to pin 2
    IC42 connects to pin 3
    Attached Thumbnails Attached Thumbnails pal_logic.jpg   pn_32-4070_rev_k.jpg  

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    Quote Originally Posted by Hoss710 View Post
    did you mark the motor bodies in comparison to the back caps and which side faces the back?. I have seen people take DC motors apart, and not mark them before disassembly. this will cause a phasing issues and motor run away. this would be my initial guess without more information.
    No I didn't! The problem was I re-assembled the motor with the tube containing the magnets upside down. This shouldn't have made a difference as the norths and souths are opposite each other. But it apears there are actually 8 magnets so to in each quadrant?? This made the motor run backwards :-(

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    Then all you should have to do is change the rev motor bit in the parameters. No need to take the motors apart again.

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    I have seen this before. that's why I posted what I had. a number of time customers have taken their motors apart to clean , and almost every time this was the problem. something to always do. even with brushed AC motors . you must mark everything before disassembly glad you got it fixed !

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