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IndustryArena Forum > Other Machines > PCB milling > Choosing Stepper Motros and Ballnut screw for Sieg SX2P
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  1. #1

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    Feb 2020
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    Choosing Stepper Motros and Ballnut screw for Sieg SX2P

    Hi All

    I am new here and not sure if this is the right thread, I need some expert people advice if you can please help me in that thank you.

    I am have a problem with choosing the stepper motors and Ball screw for converting my milling Sieg SX2P machine to CNC.
    After searching online for days I come across two motors which seems reasonable and powerful that is Nema 425oz and Nema 570oz now I am confused which one should I go for or is this bad choice or should I choose some other motor ?
    please see the link below for both. Can yo please advice me on that

    https://www.ebay.co.uk/itm/US-DE-Shi...1&isGTR=1#shId

    https://www.ebay.co.uk/itm/3PCS-NEMA...1&isGTR=1#shId


    Other confusion I have is choosing a lead screw which size I should choose 12mm, 14mm or 16mm diameter.
    I have found one which seems like 12mm with reasonable price please see link below, can you please advice me about ballnut screws.

    https://www.aliexpress.com/item/32863518333.html



    Thank You All

  2. #2
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    Re: Choosing Stepper Motros and Ballnut screw for Sieg SX2P

    Assuming you are cnc converting for PCB milling.

    The size you need depends on the space you have to fit the ball screw and nut.
    For PCB milling, the accuracy isn't that important and a few microns play won't harm.
    Both the steppers have enough power to move your SX2P mill at a decent speed. More power means more speed, more noise, more money.

    Sure there are a lot of better options that are also more expensive. I my self would fit these parts on my HBM BF16 mill without any doubt (for pcb milling and other milling tasks). The most doubtful parts are the spindles. If in time, you need more accuracy you will have learned enough to select a better one and there isn't spent a lot of money in vain.

    You need to consider if the drivers you are going to use are capable of driving (3A) these steppers.

    Have fun

  3. #3

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    Re: Choosing Stepper Motros and Ballnut screw for Sieg SX2P

    Thank you for replying,
    I believe machine can easily fit up to 16mm nut I did not open it its from research online my question is what difference it will make if I choose 12mm, 14mm or 16mm diameter ?

    I am thinking for the driver able to drive up to 5A see link below.

    https://www.ebay.co.uk/itm/202880677969

    if I choose 425oz or 570oz which one will be more accurate ?

  4. #4
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    Re: Choosing Stepper Motros and Ballnut screw for Sieg SX2P

    I prefer the 16mm screws. The nuts need a fair bit of cutting with a grinder etc but they will fit in.
    Will be more rigid.

    Where possible use angular contact bearings. Thrust bearings sit terrible on the Chinese screws and you end up with a lot of wobble.

    My choice would be 425ox on X,Y and 570oz on the Z.

  5. #5

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    Re: Choosing Stepper Motros and Ballnut screw for Sieg SX2P

    Thank you very much for replying I think I got an Idea now
    Will go for 425oz and 16mm screw with angular bearing

  6. #6
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    Re: Choosing Stepper Motros and Ballnut screw for Sieg SX2P

    Quote Originally Posted by Jadoon View Post
    Thank you for replying,
    I am thinking for the driver able to drive up to 5A see link below.

    https://www.ebay.co.uk/itm/202880677969

    if I choose 425oz or 570oz which one will be more accurate ?
    Both steppers have the same step resolution (200 steps / revolution) and will be equal in accuracy.

    The TB6600 driver will do, i use them on both my lathes. The (trouble free) speed they can reach is limited when compared to more expensive drivers like leadshine. Ebay is to optimistic about the current the driver can handle. In my experience 4A is the limit.
    Keep in mind that these drivers don't handle a high supply voltage well. To avoid a lot of resonance (electrical) use a 24 Volt power supply. A 300..350 Watt is more than enough (ignore the PSU current spec).

    De Z-axis is the heaviest part to move. If necessarily, you can lower the weight the stepper has to move, and increase the speed, by adding a contra weight. A rope, pulley and plastic water container will do for starting.


    My choice would be 425ox on X,Y and 570oz on the Z
    I agree on that choice.

  7. #7

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    Re: Choosing Stepper Motros and Ballnut screw for Sieg SX2P

    Quote Originally Posted by hfjbuis View Post
    Both steppers have the same step resolution (200 steps / revolution) and will be equal in accuracy.

    The TB6600 driver will do, i use them on both my lathes. The (trouble free) speed they can reach is limited when compared to more expensive drivers like leadshine. Ebay is to optimistic about the current the driver can handle. In my experience 4A is the limit.
    Keep in mind that these drivers don't handle a high supply voltage well. To avoid a lot of resonance (electrical) use a 24 Volt power supply. A 300..350 Watt is more than enough (ignore the PSU current spec).

    De Z-axis is the heaviest part to move. If necessarily, you can lower the weight the stepper has to move, and increase the speed, by adding a contra weight. A rope, pulley and plastic water container will do for starting.



    I agree on that choice.


    Thank you very much for replying. I almost bought power supply of 36Volt, Thank you for mentioning that, you save me from extra hassle and cost.I have a one power supply laying around at home 24Volt 10amp,What do you think That should be ok?

    About adding contra weight I did not get it how to do that mean where will I install that.
    On my milling for z-Axis there is Gas Strut installed as well, I am not sure do I removed it after conversion or leave it on?

  8. #8
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    Re: Choosing Stepper Motros and Ballnut screw for Sieg SX2P

    Thank you very much for replying. I almost bought power supply of 36Volt, Thank you for mentioning that, you save me from extra hassle and cost.I have a one power supply laying around at home 24Volt 10amp,What do you think That should be ok?
    (10 x 24) = 240 Watt will do, at least for starting. When in doubt, use a voltage meter to monitor the output voltage of the power supply when the mill is running.

  9. #9

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    Re: Choosing Stepper Motros and Ballnut screw for Sieg SX2P

    Quote Originally Posted by hfjbuis View Post
    (10 x 24) = 240 Watt will do, at least for starting. When in doubt, use a voltage meter to monitor the output voltage of the power supply when the mill is running.
    Thank you will do that

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