Steppers with Brakes



  • I'm considering using ballscrews for my Z axis on a tall 3d printer, and I'm looking into stepper motors with electromagnetic brakes.

    The kind where the brake is on unless you provide power to the brake - usually 12 or 24V DC. Then the stepper is free to move.

    I figure I could drive the brakes via a extruder heater channel on the Duet + Duex5, or by a fan header.

    The brakes use about 5-6 watts at 24V, and I'll need 4, so 20-30 Watts total.

    Is there any capability in the hardware or firmware for a brake system, perhaps tied to an axis (Z)?

    Thanks.



  • I have to ask why ball screws? Or rather, please think again. Ball screws are designed for applications where fast linear motion and low friction are the primary objectives. Neither of which are valid criteria for the Z axis of a 3D printer.


  • administrators

    There is no such facility at present, but it could be added. If you drive solenoids from heater outputs, make sure you add f!yback diodes.

    What do you perceive as the advantage of ballscrews over leadscrews?



  • @deckingman:

    I have to ask why ball screws? Or rather, please think again. Ball screws are designed for applications where fast linear motion and low friction are the primary objectives. Neither of which are valid criteria for the Z axis of a 3D printer.

    Are anti-backlash nuts a good idea for lead screws on a 3D printer Z axis?

    I can find long (1500mm) lead screws for cheap:

    https://www.accu.co.uk/en/carbon-steel-c45-trapezoidal-lead-screws/75808-L-Tr12x3-1R-1500-C45

    But they don't offer anti-backlash nuts for metric - or at least I can't find any.

    And no, I don't want to be fabricating my own lead screw nuts out of acetal…



  • @dc42:

    There is no such facility at present, but it could be added. If you drive solenoids from heater outputs, make sure you add f!yback diodes.

    What do you perceive as the advantage of ballscrews over leadscrews?

    Low friction, requiring lower torque?

    I believe ballscrews are intended to be fixed at both ends, or rather fixed at the driven end and floating at the other.

    I also have the impression that a 16mm ballscrew at 1500mm length would probably be straighter than an equivalent leadscrew.



  • The specs for the stepper brake unit on a Nema 17 stepper say that it draws 5.8W at 24V, or about 0.25A.

    So I should be able to drive four at the same time from one Fan header, with a max current draw of 1A on a 1.5A limit, flyback diode included.



  • I'm also using ballscrews on my z axis, and I don't have any brake. The resistance from the stepper motor is enough to keep the bed from falling. Zotrax M200 uses ballscrew on z axis as well, and they also don't use any brake.



  • @Shen:

    I'm also using ballscrews on my z axis, and I don't have any brake. The resistance from the stepper motor is enough to keep the bed from falling. Zotrax M200 uses ballscrew on z axis as well, and they also don't use any brake.

    What's your ballscrew diameter and pitch / mm per revolution?

    The ones I'm looking at are 1605 ballscrews, 16mm diameter and 5mm per revolution, 1500mm long.

    I'm also looking at about 5-8 pounds of weight per ball screw, 20-25 pounds on the gantry, 4 ball screws.

    The heated bed plate is big and heavy…



  • I have 2 ballscrews on either side of the bed. They are 10mm diameter, 10mm pitch. My bed is around 2.5kg, and I can put another 5kg of weight on the bed before it starts to fall.



  • Yeah, my bed is going to weigh at least 9KG/20lbs by itself, lifted by 4 lead screws and guided by 4 x HGR20/HGH20CA linear rails.

    For the length I need, I'm seeing mostly 1605's being the ones commonly available.. possibly some 1204's (12mm, 4mm pitch).

    And with everything from China, it's not the cost of the rails and screws, it's the cost of the shipping…


  • administrators

    Please add a request in the Firmware Wishlist section for this feature.



  • @GiulianoM:

    …........................Are anti-backlash nuts a good idea for lead screws on a 3D printer Z axis?

    With a bed weighing 20lb and pushing down on the lead screw nuts, gravity alone will take care of any backlash. All the lead screws and ball screws you are looking at using are for fast linear motion, usually in the X and Y directions, where gravity does not assist in taking up any "slack". That is why vendors sell anti back lash nuts.



  • @deckingman:

    @GiulianoM:

    …........................Are anti-backlash nuts a good idea for lead screws on a 3D printer Z axis?

    With a bed weighing 20lb and pushing down on the lead screw nuts, gravity alone will take care of any backlash. All the lead screws and ball screws you are looking at using are for fast linear motion, usually in the X and Y directions, where gravity does not assist in taking up any "slack". That is why vendors sell anti back lash nuts.

    ok, so I can get 12mm leadscrews and bronze flanged nuts for about $40 a piece, in the 1500mm length I need.

    The problem is, I am not finding mounting blocks or bearing blocks to mount the screws.

    Would something like these pillow block bearings be sufficient?

    Vertical: http://www.ebay.com/itm/FL001-Zinc-Alloy-12mm-Bore-Self-Aligning-Pillow-Block-Bearing-Flange-T1-/252483419183

    Horizontal: http://www.ebay.com/itm/2Pcs-Znc-Alloy-12mm-Bore-Diameter-Ball-Bearing-Pillow-Block-/182240847949

    I'm thinking the bearings are radial or possibly deep groove, instead of angular contact…



  • @GiulianoM:

    @deckingman:

    @GiulianoM:

    …........................Are anti-backlash nuts a good idea for lead screws on a 3D printer Z axis?

    With a bed weighing 20lb and pushing down on the lead screw nuts, gravity alone will take care of any backlash. All the lead screws and ball screws you are looking at using are for fast linear motion, usually in the X and Y directions, where gravity does not assist in taking up any "slack". That is why vendors sell anti back lash nuts.

    ok, so I can get 12mm leadscrews and bronze flanged nuts for about $40 a piece, in the 1500mm length I need.

    The problem is, I am not finding mounting blocks or bearing blocks to mount the screws.

    Would something like these pillow block bearings be sufficient?

    Vertical: http://www.ebay.com/itm/FL001-Zinc-Alloy-12mm-Bore-Self-Aligning-Pillow-Block-Bearing-Flange-T1-/252483419183

    Horizontal: http://www.ebay.com/itm/2Pcs-Znc-Alloy-12mm-Bore-Diameter-Ball-Bearing-Pillow-Block-/182240847949

    I'm thinking the bearings are radial or possibly deep groove, instead of angular contact…

    Answering my own question:

    K000 bearings used in the pillow blocks:
    http://catalog.amibearings.com/viewitems/light-duty-set-screw-bearing-insert/set-screw-locking-bearing-insert-k000-series

    K000 10mm bearings "rated" for 200 kgf in static radial loads… Axial loads recommended to be no higher than 20%, or 40 kgf - which equals 88 pounds of axial load with gravity.

    K001 bearings (12mm) up that to about 108 pounds of axial load capacity.

    <jedi wave="">Lead screws will be fine...</jedi>


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