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  1. #1

    Join Date
    Mar 2012
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    stepper only goes one direction

    I have a Chinese CNC machine and for some reason the stepper motor only goes one direction. I push +Z or -Z on the pendant and it will only move one way.

    I swapped the Z and X axis at the control board and then the X moves fine (using Z commands) but the Z still only moves one way (using X commands).

    I know the stepper is physically capable of moving backwards because I swapped the X and Z cannon plugs where they connect to the motors and the Z would work really jerky and weird (not smooth at all) both directions. It obviously didn't like being hooked up that way but at least it worked.

    I swapped the motor direction on the pendant (software) and that didn't fix it either.

    Also, twice today I somehow managed to get it to work. Not sure what I did. It was either a connection thing or it was something in the controller software, possibly having to do with the Z axis limits?

    Any idea what's wrong or how to troubleshoot further? Do you think it's hardware (like bad connections to the motor, driver, board, etc) or software (like the controller settings).

    Thanks so much folks!

    [if it helps the Chinese stepper motor is a "FL86STH118A-22" and the controller/board is a "RZNC-05"]

  2. #2

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    Mar 2012
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    Any ideas here guys?

  3. #3
    CRP
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    Quote Originally Posted by HalfRhoVSquared View Post
    I have a Chinese CNC machine and for some reason the stepper motor only goes one direction. I push +Z or -Z on the pendant and it will only move one way.

    I swapped the Z and X axis at the control board and then the X moves fine (using Z commands) but the Z still only moves one way (using X commands).

    I know the stepper is physically capable of moving backwards because I swapped the X and Z cannon plugs where they connect to the motors and the Z would work really jerky and weird (not smooth at all) both directions. It obviously didn't like being hooked up that way but at least it worked.

    I swapped the motor direction on the pendant (software) and that didn't fix it either.

    Also, twice today I somehow managed to get it to work. Not sure what I did. It was either a connection thing or it was something in the controller software, possibly having to do with the Z axis limits?

    Any idea what's wrong or how to troubleshoot further? Do you think it's hardware (like bad connections to the motor, driver, board, etc) or software (like the controller settings).

    Thanks so much folks!

    [if it helps the Chinese stepper motor is a "FL86STH118A-22" and the controller/board is a "RZNC-05"]
    This also could be a noise issue, try isolating the wiring from the driver to the Z from any other cables or electronics (especially the power cable to your cutting head).

    Cory
    CNCRouterParts

  4. #4

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    Mar 2012
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    I'll try that. At this stage I'll try anything... so frustrating...

  5. #5

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    Mar 2012
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    Well now it's acting strange. Sometimes it works OK but will only go in "step" mode, not "continuous" mode from the control pendant. Then it will go really slow and sound funny. And then it will go back to only moving in one direction.

    Still sound like noise? Or possibly a bad wire connection?

    I'm not impressed at all with the electrical wiring on this Chinese router. The rest of the router seems stout but they use too small of wires with lousy connections.

  6. #6

    Join Date
    Apr 2004
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    2126
    Your swap test indicates that whatever's going on, it isn't the fault of the software, controller or breakout board. That leaves the motor, plus its wiring and cable. Double-check to make sure the wiring is correct and well-attached. Assuming a 4-wire motor, there should be two phases with continuity between them. (a six-wire motor works basically the same way, but there's a center tap which can be connected so as to give you the choice of parallel or series operation). A stepper motor works by energizing one phase at a time, pushing the armature from one position or "step" to the next one, that's typically 1.8 degrees apart. When the motor changes direction, the phases change their pattern of energizing the internal electromagnets and push the other way. It sounds like one of those phases isn't operating correctly, so you're only getting half the control you need. A faulty cable can cause that, as can mis-wiring, a bad motor, bad grounding or electrical interference.

    Andrew Werby
    www.computersculpture.com

  7. #7
    CRP
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    Quote Originally Posted by awerby View Post
    Your swap test indicates that whatever's going on, it isn't the fault of the software, controller or breakout board. That leaves the motor, plus its wiring and cable. Double-check to make sure the wiring is correct and well-attached. Assuming a 4-wire motor, there should be two phases with continuity between them. (a six-wire motor works basically the same way, but there's a center tap which can be connected so as to give you the choice of parallel or series operation). A stepper motor works by energizing one phase at a time, pushing the armature from one position or "step" to the next one, that's typically 1.8 degrees apart. When the motor changes direction, the phases change their pattern of energizing the internal electromagnets and push the other way. It sounds like one of those phases isn't operating correctly, so you're only getting half the control you need. A faulty cable can cause that, as can mis-wiring, a bad motor, bad grounding or electrical interference.

    Andrew Werby
    ComputerSculpture.com ? Home Page for Discount Hardware & Software
    Well put Andrew

    Cory
    CRP

  8. #8

    Join Date
    Jun 2009
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    37
    Intermittent operation is almost always a loose connection somewhere. Check the connector and the wire connection to the motor. Also, verify that the Z axis is not somehow binding. Beyond that, could also be a noise issue. On many of the Chinese machines, it's almost standard operating procedure to tear them down and rebuild them as soon as you get them.

  9. #9

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    Mar 2012
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    Ok guys, thanks for the suggestions. I suspected it might be a bad wire but now I'll go through very carefully and confirm. I have some new connectors ordered so plan to swap those out for ones of better quality and size.

  10. #10

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    Mar 2012
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    Ok, I replaced one of the connectors that I suspected was bad but it didn't fix the problem. So here's the symptoms...

    1. When I start testing with things cold (after I haven't used it in a while) the Z axis seems to work properly when attached to the X and Y ports on the board. But when attached to the Z port it only works right in "STEP" and "DISTANCE" mode but stutters and sounds bad and barely moves in "CONTINUOUS" mode when I hold down the button (moves both up and down but barely).

    2. After I work with things for a while and things warm up (or whatever...something else may be happening to trigger it) now the Z axis will only go down no matter which port on the board it's plugged into.

    Weird.

    Does this bring any other clues as to what may be wrong?

  11. #11
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    Jul 2013
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    22
    Hey mate I had a similar problem with a 6040 cnc router.i found it was ****ty motor cabling,how I found this was testing the z axis up and down it behaved in a weird way,it would work then stall then only go one direction and make all kinds of noises. I ended up finding a sweet spot in x and y on the table where the cable carrier was bending the cables and problem solved it worked perfectly then I moved it back and it started again,after finding this I replaced all the cables and its been sweet eversince. so my advise is try the z axis in all different places on the table,try rattaling the cable carrier and see what happens also I could hear a noise it would change in sound when I moved the cable carrier around hope this may help. Danny

  12. #12

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    Mar 2012
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    Well it use to only have problems on the Z axis and only after I used it a while. Now it has problems on every axis, even when cold. I think it's the controller since it's affecting every axis and is really irregular. It only seems to get worse the more I use it.

    Anyone else using this DSP RZNC-0501 controller effectively?

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