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IndustryArena Forum > CNC Electronics > Stepper Motors / Drives > Replacing steppers for more torque options / Advice wanted
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  1. #41
    Join Date
    Jul 2018
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    6254

    Re: Replacing steppers for more torque options / Advice wanted

    Hi DAAD - What is the width of the drive belt? Peter

  2. #42
    Join Date
    May 2015
    Posts
    684

    Re: Replacing steppers for more torque options / Advice wanted

    We use the work energy method in our design model. We wanted to harness the stepper motor's high torque at low speed to get to our desired cut velocity.
    This video explains it
    https://www.loom.com/share/64ef8fb13...006761e222b076

    So by using smarter drives from Lam technology, we can reduce the current when torque is not needed. This gives the motors time to cool so then they do not miss steps as they no longer overheats.
    But you can't harness those features if you can't determine constant velocity and have enough output pins to communicate with the drives in real time.
    We use Linuxcnc and our custom component to do this 1000 times a second.
    Rod Webster
    www.vehiclemods.net.au

  3. #43
    Join Date
    Dec 2003
    Posts
    24216

    Re: Replacing steppers for more torque options / Advice wanted

    I still am puzzled why posters quote stepper motor oz-in/N-cm by quoting a NEMA size?
    NEMA 23 is a stepper motor with a 2.3×2.3 inch (58.4×58.5 mm) faceplate
    My Vexta catalogue shows 9 steppers motors from 38.2N-cm to 132N-cm, ALL with the NEMA 23 mounting base size.
    CNC, Mechatronics Integration and Custom Machine Design

    “Logic will get you from A to B. Imagination will take you everywhere.”
    Albert E.

  4. #44
    Join Date
    Jul 2018
    Posts
    6254

    Re: Replacing steppers for more torque options / Advice wanted

    Hello DAAD - I redid the calcs. I downloaded the drive file and it uses a 1/2" belt. Since I had the pulley geometry I used that to calculate the rotational inertias. So in summary. The drive system has been well designed as the motor torques and motor speeds match quite well for an accel of 0.83m/s/s and a top speed of 25m/min. So not talking about cutting at the moment, the motor runs out of puff at about 1000rpm and at about 968rpm it runs out of torque to accelerate the system. Again check the math. This is for moving the gantry as it has two motors. The Z axis being lighter will have more potential but its about half the mass and half the torque so its about the same...

    The rotational side of things the motor is 96% of the inertia, the pulleys are 4%. So the math's for the system look good so its then up to the system to do the right thing. This points at the voltage again letting it down.... Keep at it. Peter

    I just noticed that I halved the torque requirement for two motors, Shouldn't have done that as the calc was for one motor and one pulley system. But rotational component small so not wrong by much... won't correct it too many numbers for today. Peter

  5. #45
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    Jul 2018
    Posts
    6254

    Re: Replacing steppers for more torque options / Advice wanted

    found this readable article on stepper motor control Peter

    https://www.edn.com/improving-curren...otion-quality/

  6. #46
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    Jul 2018
    Posts
    6254

    Re: Replacing steppers for more torque options / Advice wanted

    Hi DAAD - I was wondering about the 10N used for the friction in the AVID data so checked it out. I'm assuming here that you have 20mm rails. I looked up a car static capacity and used the graphs supplied by PMI. Other makers are about the same. I used a luggage scale to measure the seal static friction, its less once on the move and these are new cars so the seals are a bit sticky. Friction for the gantry comes out at 27N so 10N maybe a bit light. But its tiny vs the rest of the loads... Peter
    Attached Thumbnails Attached Thumbnails friction factor.jpg   seal friction 1.jpg   car friction 1.jpg  

  7. #47
    Join Date
    Sep 2019
    Posts
    44

    Re: Replacing steppers for more torque options / Advice wanted

    Oops,

    Missed out on the posts!

    Thanks for the extra info, will lok into it!
    Surely the avid cnc is well designed! Only "flaw" is rigidity of the system.

    #peteng, belt is 15mm GT3 5 pitch one.

    Adam

  8. #48
    Join Date
    Sep 2019
    Posts
    44

    Re: Replacing steppers for more torque options / Advice wanted

    At the moment i'm searching a 20T motor pulley to fit 14 mm keyway axis. The avid ones are 20T 1/2" keyway, but in europe most steppers the size i need are 14mm.
    I've searched for the last couple of hours but can't find any that fits the needed specs.

    The belt on the system is an gt3 375-5mgt3-15, so i'm in the search of an GT2 profile 5mm pitch, 15mm wide BF style hub , 20Tooth, 14mm bore keyway.

    If anybody knows where i could find these pulley's please let me know.

    Avid pulley attached for reference.

    Keep Safe,

    Adam
    Attached Thumbnails Attached Thumbnails Screenshot 2021-01-24 at 20.32.42.jpg  

  9. #49
    Join Date
    Dec 2003
    Posts
    24216

    Re: Replacing steppers for more torque options / Advice wanted

    For drive purposes, I would recommend paying a little extra for S.S. versions over the aluminum.
    Misumi have a excellent source of pulleys, and hardware in general. https://us.misumi-ec.com/?gclid=Cj0K...caAhO9EALw_wcB
    Their catalogue is handy just for the engineering data in it.
    Al.
    CNC, Mechatronics Integration and Custom Machine Design

    “Logic will get you from A to B. Imagination will take you everywhere.”
    Albert E.

  10. #50
    Join Date
    Mar 2003
    Posts
    35538

    Re: Replacing steppers for more torque options / Advice wanted

    Get a 1/2" bore pulley and bore and ream it to 14mm.
    The Nema 34 standard is 1/2" shafts, and that was all you would find until the Chinese started making them with 14mm shafts.
    Gerry

    UCCNC 2017 Screenset
    http://www.thecncwoodworker.com/2017.html

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    http://www.thecncwoodworker.com/2010.html

    JointCAM - CNC Dovetails & Box Joints
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    (Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)

  11. #51
    Join Date
    Sep 2019
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    44
    Quote Originally Posted by ger21 View Post
    Get a 1/2" bore pulley and bore and ream it to 14mm.
    The Nema 34 standard is 1/2" shafts, and that was all you would find until the Chinese started making them with 14mm shafts.
    In my neck of the woods 14mm is te norm. Leadshine, lam techonologies, sanyo denki all comes standard with the 14 axle.
    If i don’t find the 14mm pulleys i wil look into adapting the 1:2 ones.

  12. #52
    Join Date
    Jul 2018
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    6254

    Re: Replacing steppers for more torque options / Advice wanted

    Hi DAAD - You will probably buy a set same cost as the pulley eg

    https://www.aliexpress.com/item/3282...11615926qttsXp

    Peter

  13. #53
    Join Date
    Sep 2019
    Posts
    44

    Re: Replacing steppers for more torque options / Advice wanted

    Quote Originally Posted by peteeng View Post
    Hi DAAD - You will probably buy a set same cost as the pulley eg

    https://www.aliexpress.com/item/3282...11615926qttsXp

    Peter

    Nice!

    I see these are the HTD versions profile, wouldn't it be better to keet the gt2 profile for better accuracy?

  14. #54
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    Jul 2018
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    6254

    Re: Replacing steppers for more torque options / Advice wanted

    Hi DAAD - There's lots of discussion about the differences in profiles and their use in the forum. All are used satisfactorily for CNC applications it seems. Here's a good manual on belts.

    https://www.optibelt.com/fileadmin/p...ming-Belts.pdf

    https://www.sdp-si.com/products/deta...elt-detail.php belt section i9nfo seems GT2 is being replaced by GT3

    In Oz its easier to get AT sections. These are PU belts with steel cords. These are much stiffer then the GT with fibreglass cords. Can you get GT2/3 with steel cords? AT stands for advanced T so supersedes T. There is also an ATL which is a zero clearance AT belt for better displacement control then AT. Here they cost about 2x the AT section.

    Peter

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