Thread: Y axis stalling

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  1. #1
    I've got a 3020T and it seems fine apart from a problem with the y axis which seems to come on after the mill has been running for a while. It stalls like if you have set the feed rate too high and looses track of where it is, i.e. end up being short of where it should have got to. I've taken a video of it, this was the worst it has ever been at this point.

    http://www.readresearch.co.uk/person...l_stalling.avi

    I've got the motor and coupling close and centralised OK, the y axis is tighter than the others, but this is to be expected as it's got more weight to carry and a longer leadscrew? Also has a tiny bit of eccentricity.

    Any ideas? I'm wondering if it's the control box.

  2. #2
    Quote Originally Posted by richie00boy View Post
    I've got a 3020T and it seems fine apart from a problem with the y axis which seems to come on after the mill has been running for a while. It stalls like if you have set the feed rate too high and looses track of where it is, i.e. end up being short of where it should have got to. I've taken a video of it, this was the worst it has ever been at this point.

    http://www.readresearch.co.uk/person...l_stalling.avi

    I've got the motor and coupling close and centralised OK, the y axis is tighter than the others, but this is to be expected as it's got more weight to carry and a longer leadscrew? Also has a tiny bit of eccentricity.

    Any ideas? I'm wondering if it's the control box.
    errrm... is that not your X axis?
    first id go into motor tuning and knock your rapid speed down a bit on the offending axis and if that stops it we can assume that the drag on that axis has gone up a bit for some reason (has it been stood for a while?)

  3. #3
    If it's sticking enough to stall going that slow then this should be easy to find.! It sounds very much like very dry or knackerd lead nut to me with it coming on after time.?
    Could be a tight bearing
    Do this in a methodical order and you'll track it down quick.
    Start by disconnecting the lead nut and running gantry up and down feeling for binding.? If it does then loosen bearing mounts and again run up and down seeing if it lessens.? It could just be an alignment issue.? tighten up and if gone then happy days.!! . . If still sticking then chances are it's a bad or dying bearing.

    Check the lead nut for wear or crap embedded in it. Run it up and down checking for tight spots. Unfortunately if it's worn or tight spots then nothing much can be done.!

    One thing I've experienced with these machines is the wiring is rubbish. Recently I repaired one where the Z axis and Y would change direction for no reason which turned out to be stepper wires. New shielded wires and machine ran a lot nicer and stable.

  4. #4
    Quote Originally Posted by blackburn mark View Post
    errrm... is that not your X axis?
    On this machine the run them other way round a mark.? Drove me crazy crashing kept crashing the bloody thing. .

  5. #5
    Quote Originally Posted by JAZZCNC View Post
    On this machine the run them other way round a mark.? Drove me crazy crashing kept crashing the bloody thing. .
    ahhh! something new every day :)

  6. #6
    Thanks Jazz will try what you said. I should point out that this is a new machine only used about 3 evenings so there shouldn't be anything worn. I have tried to search for problems with this machine and found some Youtube footage of a similar problem and they said it was the wires. I have tried jiggling the wires to reproduce the fault but can't. Also the Y axis wires never move.

    I'm a total novice to CNC, is the lead nut the nyloc that is on the end of the y axis leadscrew? I contacted the seller (ebay) and they said not to touch this nut. Actually they seemed really helpful and quick to respond, but since I sent them the video they are ignoring me. I wonder if I have gone outside of some Paypal claim window or something, and they were trying to fob me off until that time.

  7. #7
    Quote Originally Posted by richie00boy View Post
    Also the Y axis wires never move.
    One of the issues I seen was that the wires are too tightly crammed into the cable guide and rubbing badly. They where also unshielded and I'm sure some of the trouble was electrical noise was interfering with the steppers because when changed for shielded cable the machine was much smoother and sounded loads better.?

    Quote Originally Posted by richie00boy View Post
    I'm a total novice to CNC, is the lead nut the nyloc that is on the end of the y axis leadscrew?
    No it's the bit that's fastened too the gantry cross brace.

    How long running before this starts happening.? Also is the noise I'm hearing there all the time or does that come on after time has well.?

  8. #8
    Not sure what you mean there, the noise is the stalling. If the machine has been on about an hour it seems more prone to it. If I was to rewire it any ideas where I can get replacement connectors to fit the blue control box?

    Is the nut the part in the housing that the leadscrew tuns to move the gentry up and down? I have tried moving the stepper motor by hand to feel for any tight spots and there didn't seem to be anything that bad.

    The stalling can happen anywhere on the y axis, doesn't seem to be related to x or z axis position.

  9. #9
    Quote Originally Posted by richie00boy View Post
    Not sure what you mean there, the noise is the stalling. If the machine has been on about an hour it seems more prone to it. If I was to rewire it any ideas where I can get replacement connectors to fit the blue control box?

    Is the nut the part in the housing that the leadscrew tuns to move the gentry up and down? I have tried moving the stepper motor by hand to feel for any tight spots and there didn't seem to be anything that bad.

    The stalling can happen anywhere on the y axis, doesn't seem to be related to x or z axis position.
    Maplins sell the connectors :)

    I had to replace the x,y and z cables on our machine to keep the machine going, although i used standard connecting cable because it was all i had to hand at the time. Machine has worked ok since.

    Swap the cable over and see if the fault tranfers to that axis which should confirm a cable problem.

  10. #10
    Thanks for that, looks like they are Maplin code FK24B.

    When it starts doing it again I'll swap X and Y cables over and see if it changes over. Is there any great danger in plugging and unplugging connectors on the control box when it is on?

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