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  1. #21
    Quote Originally Posted by m_c View Post
    I think you might need a few things clarified.

    The microstepping setting simply controls how many steps the drive takes on the input, compared to what it outputs. A more accurate description would be step-multiplier/ratio.
    I'd guess the drive output will never go above 16 or 32 microsteps, as above that resolution, it makes no difference to motor smoothness, and it certainly does nothing for accuracy, as microstepping is by nature inaccurate. Due to the very nature of microstepping, what it's essentially doing is holding the motors rotor between two electromagnetic springs, so position cannot be guaranteed other than to the nearest step.
    Personally, I would never run above 32 microsteps, as there is no real benefit.

    In terms of current. In electric motors, current = torque. Reduce current, you reduce torque. Less torque means you can't accelerate as fast. It also likely means you'll hit the stepper motor/driver bad resonance point and stall at a lower speed.
    Too high a current could cause failure due to overheating, but I'm sure you would have noticed if the motor had heated up.
    As Clive says, stepper motors can run hot. 80degC after running for a long time is acceptable, but if they get that hot in a matter of minutes, then you've got a problem.


    One thing you could try, is unbolt the motor, and separate it from the screw (that style of coupler will simply pull apart)
    Try spinning the screw by hand, to see if it feels smooth
    And run the motor with no load.


    Having watched the video again, it could just be the fact it's using a big stepper motor.
    It does sound like the stepper motor vibrating, and being amplified through the relatively light weight rig. There does seem to be a variation in sound level per revolution, but probably nothing you'd need to worry about.

    A solution would be either a small servo, or possibly a smaller stepper motor with some gearing.
    Although given you don't need high precision, I wonder if the existing motor could be mounted using some kind of anti-vibration mounts to isolate the motor vibration from the rig.
    Thanks for the comment and explanation on Microstepping. I knew some of that already but just provided the info as I know some people may ask for it.

    I knew that voltage had an impact on torque but didn't realise current also does. Thanks for explaining that. With what you said in mind, is it odd that I noticed a reduction in vibrations when I reduced the current? From what you said the vibrations should have increased?

    Precision is a big factor for me. When you shoot at 1:1 macro levels, in other words very very close to things, I think accuracy will be a big factor. Think filming a watch face or panning over a diamond. Mistakes at that level would be really obvious.

    I'm hearing mixed things from people, some are certain it's an issue and some not so sure. I think for now, I'll wait to hear what the manufacturer says, then perhaps take it apart and investigate further...If all else fails then perhaps a geared motor as you say could be a good approach.

  2. #22
    m_c's Avatar
    Lives in East Lothian, United Kingdom. Last Activity: 3 Days Ago Forum Superstar, has done so much to help others, they deserve a medal. Has been a member for 9-10 years. Has a total post count of 2,908. Received thanks 360 times, giving thanks to others 8 times.
    The other part of the motor equation is voltage. Voltage is what gives you speed.

    As a motor spins faster, the back emf (electro motive force - essentially voltage that fights back against the applied voltage) increases, so in order to maintain current (which is what give you the torque), you need to apply an ever higher voltage.
    The driver handles all this, so all you need to do is set the current.


    As for why the motor seems smoother at lower current, I wonder if there is a fault somewhere. Without having a motor or drive to substitute, there isn't really that much testing you could do. Measuring the resistance through the coils of the motor would test for any obvious electrical faults with the motor, but they probably wouldn't be that conclusive.


    My comment about precision was although Macro photography needs accuracy, it's more a case of needing repeatability, rather than pure precision. You don't really need the position to be highly accurate, you just need it to be repeatable.
    Avoiding the rubbish customer service from AluminiumWarehouse since July '13.

  3. #23
    Quote Originally Posted by m_c View Post
    The other part of the motor equation is voltage. Voltage is what gives you speed.

    As a motor spins faster, the back emf (electro motive force - essentially voltage that fights back against the applied voltage) increases, so in order to maintain current (which is what give you the torque), you need to apply an ever higher voltage.
    The driver handles all this, so all you need to do is set the current.


    As for why the motor seems smoother at lower current, I wonder if there is a fault somewhere. Without having a motor or drive to substitute, there isn't really that much testing you could do. Measuring the resistance through the coils of the motor would test for any obvious electrical faults with the motor, but they probably wouldn't be that conclusive.


    My comment about precision was although Macro photography needs accuracy, it's more a case of needing repeatability, rather than pure precision. You don't really need the position to be highly accurate, you just need it to be repeatable.
    Oh good, glad to hear I'm not wrong about the driver setting the voltage automatically. OK, so I can safely increase the current back to where it was and eliminate that as a cause for this issue. That's another thing down, moving in the right direction!

    Hopefully the manufacturer can shed some light but if not I'll see if there's anything obviously wrong when, or if, I take it apart. If it came to replacing the motor is there any motor you'd recommend?

  4. #24
    This particular driver (linked below) connects directly to AC so it's 240vAC. It has the PSU built in unlike the DM 542T drivers I have which utilize a separate PSU that supplies 42.5 volts.
    Just to be clear that you are using the 3 phase driver that is supplied by 230v ac. I so that is fine.

    As a lot of steppers are two phase. I take it your stepper is actually 3 phase.

    What controller are you using to drive it ?
    ..Clive
    The more you know, The better you know, How little you know

  5. #25
    Quote Originally Posted by Clive S View Post
    Just to be clear that you are using the 3 phase driver that is supplied by 230v ac. I so that is fine.

    As a lot of steppers are two phase. I take it your stepper is actually 3 phase.

    What controller are you using to drive it ?
    Yes, it is a 3 phase stepper.

    The controller is a piece of software called Mantis which is designed for motion control video - https://www.bfg-motion.com/index.php?p=1_4

  6. #26
    m_c's Avatar
    Lives in East Lothian, United Kingdom. Last Activity: 3 Days Ago Forum Superstar, has done so much to help others, they deserve a medal. Has been a member for 9-10 years. Has a total post count of 2,908. Received thanks 360 times, giving thanks to others 8 times.
    I'm currently wondering, if a single coil in a 3 phase stepper had failed, would it run but with vibrations?
    If you've got a multimeter, disconnect the motor wires at the driver, and compare the resistance between all the wires.
    The datasheet lists resistance as 2.48ohm per phase, but I don't know if that will with coils connected (i.e. give an actual reading of 2.48ohm) or for each coil individually (which would give a reading of about 1.66ohm ).

    I'd also unbolt the motor and try running it. It's only the 4 bolts that hold it in place. As long as there's no marker paint on the bolts and you don't damage anything, the supplier will be none the wiser you've had it off.
    If the motor runs rough disconnected from the slider, then you know that's the main problem.


    For a replacement, I'd probably go for a 200W servo, and combine it with a planetary reducer box to give more control (3000rpm is a bit much for something with this short a travel directly coupled to a 10mm pitch ballscrew!)
    Have a look a http://servo.xlichuan.com/ for ideas. Servo motor size would be 60 frame, and you'd need a new adapter for fitting the motor, but that's nothing major.
    You can buy Lichuan servos via Aliexpress - https://www.aliexpress.com/store/1907567
    Although I think all their gearboxes are built to order. The last one I ordered added a couple weeks delay to the order, as they had to build the gearbox.
    Avoiding the rubbish customer service from AluminiumWarehouse since July '13.

  7. #27
    Ok well, this convinces me even more that it's something wrong with the linear stage rather than the motor.

    I fit these types of motors all the time, by type I mean 3 phase Motor with 220V mains powered drives and I can tell you without a doubt that at this size just reducing the current shouldn't make it stall on an unloaded linear stage that using ball-screws.! . . . Unless the stage as gots excessive friction from misalignment or something being bent.

    This also fits with the noise because the power in these motors will easily overcome any friction, other than outright sticking, this would cause vibrations as it powers thru any sticktion.
    For instance, a 7.5Nm Nema 34 motor with 220V drives connected to a ball-screw will easily lift a fully grown man off the ground and not bat an eyelid.
    When working on a CNC machine it will happily accelerate a 50kg mass holding the spindle in excess of 2G to a velocity of 20mtr/min and bring it back to a dead stop in fractions of seconds and then push that same mass with a 12.5mm tool thru a solid piece of Oak at 8mtr/min.!!

    So hopefully you're getting some idea of what I mean when I say an unloaded linear stage that uses a ball screw shouldn't be making it stall just because the current is set a little low.

    I'm sticking with my first suggestion that the linear stage is binding or bent or twisted.!
    -use common sense, if you lack it, there is no software to help that.

    Email: [email protected]

    Web site: www.jazzcnc.co.uk

  8. #28
    Quote Originally Posted by m_c View Post
    I'm currently wondering, if a single coil in a 3 phase stepper had failed, would it run but with vibrations?
    I like your thinking. Not sure if that's what would happen, but interesting and simple test. Of course, it could also be the drive.

  9. #29
    Thanks again everyone.

    Once I have the OK from the manufacturer I'll take the drive off and run some tests to exclude it as an option.

    JazzCNC - What you're saying makes total sense. It seemed so odd to me that the drive would stall that easily when the current was lowered and there was no load. Makes total sense that something else is causing friction. Couple quick things:

    1) Is there anything I could have done which could have caused this? The slider has hit the end a few times while I was getting used to the software but nothing major.
    2) Would this be obvious when I take it apart or could it be a subtle bend?
    3) How would you test for it?

    I'm just thinking about what the manufacturer will ask and what I'll need to come back with. Sadly, my experience with Chinese companies on sires like AliExpress is that they don't like to take responsibility when there's a problem. Hopefully this will be different.

    Finally, if you're correct in your assumption, is it easy to fix?

  10. #30
    Quote Originally Posted by mbridge87 View Post
    Thanks again everyone.

    Once I have the OK from the manufacturer I'll take the drive off and run some tests to exclude it as an option.

    JazzCNC - What you're saying makes total sense. It seemed so odd to me that the drive would stall that easily when the current was lowered and there was no load. Makes total sense that something else is causing friction. Couple quick things:

    1) Is there anything I could have done which could have caused this? The slider has hit the end a few times while I was getting used to the software but nothing major.
    2) Would this be obvious when I take it apart or could it be a subtle bend?
    3) How would you test for it?

    I'm just thinking about what the manufacturer will ask and what I'll need to come back with. Sadly, my experience with Chinese companies on sires like AliExpress is that they don't like to take responsibility when there's a problem. Hopefully this will be different.

    Finally, if you're correct in your assumption, is it easy to fix?
    #1 Only if you hit very hard and fast would I expect big damage.
    #2 It should be quite obvious if it's sticking to the point it stalls the motor.
    #3 I've never used one of the stages so I have no idea what's under those covers so I can't advise on how easy to test or difficult to fix, if indeed I am correct.

    Just for a laughs n giggles, and to point out the power of steppers, here's a single 4Nm 2 phase Closed loop stepper running on just 60Vac being stress tested at 10mtr/min.
    I'd estimate you have more than twice that power and much smoother action with 3 phase motor.

    -use common sense, if you lack it, there is no software to help that.

    Email: [email protected]

    Web site: www.jazzcnc.co.uk

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