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  1. #1
    Hi,
    The items in cause are Nema 34 motor 5.6A, 1200oz-in, and driver DQ860MA.
    Dip switches set as OFF OFF ON ON OFF ON ON OFF , which sets the thing to 4.9A Peak, 3.5A RMS, Full Current from SW4 (i don,t really know how to set this), and 2000 pulse/rev. The next current setting is 5.7A peak.

    In mach 3, in ports and pins, motor outputs, checking only the enabled column does nothing, as I,ve seen in some tutorials. Checking only step low active will get the motors running, and also checking both dir and step low active, seems to work.

    In config, motor tuning, I,ve set a few different speeds and acceleration just to see the difference. What exactly should I set in there?

    Now, I,m new to this, and I,ve surely missed something, as the motors get relatively warm after a 1-2 min of running a test gcode from the default mach3 folder.
    The motors are not connected to the ballscrews, so there isn,t any load to carry.

    What have I done wrong?


    Regards,
    Andrei

  2. #2
    I can not see any thing wrong with how the stepper driver is set up

    with stepper motors the motor current depends on what you set by the DIP switches - sw1 to sw3
    not the mechanical load on the motor
    so the current does not go up when you mechanically load the motor as you may of expected

    depending on which manufactures data sheet you look at
    the motor can safely run at 70 to 80 degrees C - too hot to touch !

    a quick look on line did not find clear instructions for the setting of sw4
    but going by a photo of your DQ860MA driver
    I expect sw4 sets the current reduction when the switch is set to OFF and the motor is idle ( not being stepped )

    set to ON the motor will run hotter but should be OK

    setting the motor current to 4.9A instead of 5.6A will do two things
    1) reduce the motors temperature
    2) reduce the motor torque

    if the room temperature is not too high
    then I expect you can safely set the motor current to 5.7A
    the extra 1.7% current should not be a problem
    especially with sw4 OFF


    John
    Last edited by john swift; 15-06-2018 at 09:54 PM.

  3. #3
    Hi John,
    Thank you for the reply.
    It seems the problem then is my lack of experience with how this equipment runs in normal conditions. Besides others which might come in the near future.
    I,ll adjust the settings a bit then, as you,ve recomended, and proceed to mount the motors on the machine.


    Regards,
    Andrei

  4. #4
    Neale's Avatar
    Lives in Plymouth, United Kingdom. Last Activity: 8 Hours Ago Has been a member for 5-6 years. Has a total post count of 1,157. Received thanks 209 times, giving thanks to others 5 times.
    General recommendations for stepper motors on CNC routers - set the DIP switch to reduce current when motor is stopped. You do not need as much torque to keep the motor in position when not moving, so you can safely reduce the current and therefore motor heating. Then adjust the motor current based on the motor temperature. Select a current setting, and check the motor case temperature with your hand after, say, 30 minutes. If you can hold it comfortably, try increasing the current. If it is too hot to touch, reduce the current. Aim at a motor temperature of about 60degC, which is about the maximum you can hold. Stepper motors are designed to run at these kinds of temperatures. Current ratings, specification sheets, etc, give you a first guess, but in practice you just want as much current as possible without the motor becoming too hot.

  5. #5
    Hi Neale,
    Thank you for the info.
    As soon as I,ll get the machine going, I,ll post some photos, and some detailed info about it, to get some feedback and advice.
    For example, the gantry weighs apx 250 lbs (100 plus kilos), and even if the motors are capable of moving it fairly easy, and the ball screws 2005 seem ok, surely there is an ipm limit, to avoid any problems from the inertia. It,s a wood router design, 5x5 feet, steel tubing frame.
    I,m reading as much as I can online, but surely there will be some things which I.ll not be able to figure out and I,ll have *to contact someone who knows what he,s taking about* as someone from youtube nicely put it.

    All the best,
    Andrei

  6. #6
    m_c's Avatar
    Lives in East Lothian, United Kingdom. Last Activity: 9 Hours Ago Has been a member for 9-10 years. Has a total post count of 2,123. Received thanks 233 times, giving thanks to others 5 times.
    According to the photo of the drive at http://www.wantmotor.com/product/dq860ma.html SW4 changes between full current and half current.

    As has been said, stepper motors can run pretty hot. If they're getting too hot to touch within a couple minutes, something is wrong, but 80deg after an hour or so of running is perfectly acceptable.
    Avoiding the rubbish customer service from AluminiumWarehouse since July '13.

  7. #7
    Hi again,

    Here are the photos I.ve promised 4 weeks ago.
    It is a 5/5 machine (1.5m/1.5m) made of 2.3 inches (6cm) steel tubing, and aluminium plates.
    Rails and ballsscrews of 20 mm. Nema 34 motors (overkill for z axis, but i.ve bought a kit of 4 a few years ago, I.ll get a nema 23 kit sometime in the future). The part of the gantry moving left and right weighs apx 65 pounds (30 kg), while the whole gantry apx 240 pounds (110kg). I did not have any problem so far with the supported rails and bearings, or screws and motors, just a limitation in speed, as a hard stop at a high speed will shake the whole thing. Adjusting each motor to a certain speed seems to work fine.
    The project was designed at first with 2 motors on the y axis, and it weight apx 200 pounds, but the fact that I could not mecanically sync the two ballscrews involved, had me worried and I.ve decided to go with one screw in the middle, as any kind of failure does not have the potential to break or bend something.
    It is this large, as I need this mainly for carving soft and hardwoods, for cabinet making, and this size let me fit 6 door panels at once on the table.


    This is where i.ve got so far with the project, and once again I ran into an issue which I.m not able to fix. Everything was going fine, until I.ve wired mains for the vfd, then I had a surprise when I almost crushed the z axis as it did not stop when I released the keybord. After I.ve wired the spindle, evrything went nuts, as the steppers make a strong noise, and move back and forward quite fast. It.s a chinese 1.5 kw air cooled kit.
    As it can be seen in the photos, my idea was to put eveything in one box, including the pc.
    I.ve decided to make another enclosure for the vfd and move it a bit further away, and it did not fix the problem. When I turn on the power for steppers (with a contactor) and the vfd (cam swith), even if the pc and mach 3 are off, or even if the vfd is off, the steppers go mad until i hit reset in mach 3, then they stop and work fine, until i turn on the vfd and/or the spindle.

    The wires are shielded, 4 wire cable for all steppers and spindle (18 and 14 awg). I did open the cap of the spindle and connected to the case a ground wire (the 4th one) and connect it to a steel rod in the ground. I did this because it says in the manual to avoid having a common ground with a welder. And I do use one quite often. I did not connect the shielding to anything. I.ve only tried yesterday to connect one end of the shielding at the vfd end to see if it makes any difference, and it did not, and also disconecting the spindle ground from the vfd did not do anything (as by default there is not a 4th wire available). No shielding it connected at any end for the steppers or the limit switches. The only non shielded wires are the mains for everything, pc, sources, drivers, breakout board and vfd.
    All the wires go togheter in a cable drag chain.

    So this beeing one issue, the second is how to wire and configure the limit switches. From what I know so far, I can wire all of them in series, normaly closed, and connect then to the breakout board (DB25-1205 in my case), to one pin from P10 to P15, and to GND. Well, I did something like that, only that I.ve separated each axis 2 limit switches to separate pins. So P10,11,12 to X,Y,Z and P13 to Probe, P15 to Estop, and all grounds together. And it does not work, as the RESET button from mach 3 stays on emmergency limit swicth all the time, when I enable the pins in cause.

    So 3 issues,
    1. How to fix the stepers issue? I though I.ll ask first here, and then call an exorcist. (it looks a lot like in the movies) :P
    2. How to wire and setup the limit switches?
    3. Opinions, reviews, criticism, potential problems and solutions for this particular design, if you may. :)

    It.s a long post, so before anything else, thank you for taking the time to read it.
    Regards,
    Andrei

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  8. #8
    nd. I did this because it says in the manual to avoid having a common ground with a welder. And I do use one quite often. I did not connect the shielding to anything. I.ve only tried yesterday to connect one end of the shielding at the vfd end to see if it makes any difference, and it did not, and also disconecting the spindle ground from the vfd did not do anything (as by default there is not a 4th wire available). No shielding it connected at any end for the steppers or the limit switches. The only non shielded wires are the mains for everything, pc, sources, drivers, breakout board and vfd.
    All the wires go togheter in a cable drag chain.
    It is important to connect all the shields to a star point at the control box. Including grounding the router frame.

    Only ground one end of the shields. Also make sure the various mounting plates are also grounded to the star point.

    With a gantry that wide I think you will need two screws to stop it racking this can be done with one motor and a long belts or two motors one each side.
    ..Clive
    The more you know, The better you know, How little you know

  9. #9
    Hi Clive,
    Thank for your reply.
    What do you mean by a star point?
    So I should connect all the shieldings at one end for the spindle, the steppers and the limit switches, to a common point in the case. The frame has a common ground/earth with the spindle, which goes into the vfd and from there into one iron rod in the ground. Everything else, has the ground wires sent into the main electrical grid.

    After all the shields are connected to this star point, where should this star point be wired to?

    Regards,
    Andrei

  10. #10
    Quote Originally Posted by Radu_Andrei View Post
    Hi Clive,
    What do you mean by a star point?
    So I should connect all the shieldings at one end for the spindle, the steppers and the limit switches, to a common point in the case. The frame has a common ground/earth with the spindle, which goes into the vfd and from there into one iron rod in the ground. Everything else, has the ground wires sent into the main electrical grid.

    After all the shields are connected to this star point, where should this star point be wired to?

    Regards,
    Andrei
    OK I am not familiar with how you receive you incoming mains in your country In the UK the electric company supplies a ground point (that in general is also connected to our neutral) But in Spain in the country areas the supply does not include a ground So you have you use an earth rod in the property.

    In your case I think I would connect the shield of the cy4 core going to the spindle to the star point at the control box end only. Ie don't connect the other end to the earth in the VFD.

    Thee start point is connected to the main ground (if that is a earth rod then that)

    What you are trying to achieve is not to get any ground loops.

    Do you need to take the mains for the VFD into the control box.
    ..Clive
    The more you know, The better you know, How little you know

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