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  1. #1
    Member Goce93's Avatar
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    Default Cnc router electronics

    Hi guys, i want to build 120cm x 80cm cnc router, and i have few questions?
    I want to use 4 x nema 23 stepper motors (2 on X axis) 269 oz.in 2.8A 3.2V, 4 x TB6560 12-36VDC max 3A stepper drivers, 1 x PSU 24V 15A, and arduino uno. It will be a wooden frame, about 28kg gantry, 500-700W router, belt and pulley on X and Y axis (20 teeth pulley, direct drive) and leadscrew 1605 on Z axis. It will be used for cutting wood.
    1. I want to know are the all electronics compatible?
    2. Is stepper motor size good, or i need bigger or smaller ones for this application?
    Thanks!!

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  2. #2
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    Default Re: Cnc router electronics

    Hi,
    all steppers lose torque the faster they go, thats plain physics and you can't get around it.

    The inductance of a stepper is a good measure of how bad that torque degradation will be, the lower the better. For example a 269oz.in stepper of 5mH
    inductance probably will have 5% or less, ie 13 oz.in at 1000 rpm, whereas a 260oz.in stepper but only 1mH may have 100oz.in at 1000rpm.

    I think your 23 size 269oz.in steppers are about right but they MUST be low inductance or you will be disappointed.

    The second way to defeat the degrading torque is to use the highest voltage drivers and power supply you can. Don't waste your money on a 24V supply,
    that wouldn't pull the skin off a rice pudding, and those TB6560 drivers have a poor reputation for lasting. What you want is 80VDC capable drivers,
    about the highest voltage of regularly available drivers with an 80VDC linear (transformer/rectifier/capacitor) power supply.

    Craig



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    Default Re: Cnc router electronics

    Hi GoCe - Agree with Craig. Go higher voltage. 48V is your next step as low cost drivers are about 50V max. I've built 12V systems and they just don't work. 24V is OK for N17 motors that go slow. Your N23's are good. The 20mm pully will give you lots of speed but low force. But if your only cutting wood and plastic thats OK. Something like a 700W makita router is great but noisy. Look for DC spindles on ebay with ER collets. Same price or less as Makita cuts nearly as good and they are quiet. I've cooked a few TB6560 drivers wouldn't use them,,, 16mm ballscrew is big for Z axis 12mm will be cheaper and just as good 5mm lead is good for Z axis.. 15A PS is expensive and overkill 10A is fine....What rails are you planning on using...cheers Peter



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    Quote Originally Posted by joeavaerage View Post
    Hi,
    all steppers lose torque the faster they go, thats plain physics and you can't get around it.

    The inductance of a stepper is a good measure of how bad that torque degradation will be, the lower the better. For example a 269oz.in stepper of 5mH
    inductance probably will have 5% or less, ie 13 oz.in at 1000 rpm, whereas a 260oz.in stepper but only 1mH may have 100oz.in at 1000rpm.

    I think your 23 size 269oz.in steppers are about right but they MUST be low inductance or you will be disappointed.

    The second way to defeat the degrading torque is to use the highest voltage drivers and power supply you can. Don't waste your money on a 24V supply,
    that wouldn't pull the skin off a rice pudding, and those TB6560 drivers have a poor reputation for lasting. What you want is 80VDC capable drivers,
    about the highest voltage of regularly available drivers with an 80VDC linear (transformer/rectifier/capacitor) power supply.

    Craig
    About the stepper inductance, i was looking and all steppers are about 4-5 mH, how much inductance will be good?, and i want my router to cut with about 100 ipm, its not that fast.
    And is not a problem to buy bigger drivers and PSU just i want to know can i connect those drivers on arduino because they are too big, or size is no matter??
    And if you want can you send me some links of PSU that you reccomend me?
    Thanks ????

    Last edited by Goce93; 08-19-2021 at 05:29 PM.


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    Quote Originally Posted by peteeng View Post
    Hi GoCe - Agree with Craig. Go higher voltage. 48V is your next step as low cost drivers are about 50V max. I've built 12V systems and they just don't work. 24V is OK for N17 motors that go slow. Your N23's are good. The 20mm pully will give you lots of speed but low force.
    But if your only cutting wood and plastic thats OK. Something like a 700W makita router is great but noisy. Look for DC spindles on ebay with ER collets. Same price or less as Makita cuts nearly as good and they are quiet.
    I've cooked a few TB6560 drivers wouldn't use them,,, 16mm ballscrew is big for Z axis 12mm will be cheaper and just as good 5mm lead is good for Z axis.
    15A PS is expensive and overkill 10A is fine....
    What rails are you planning on using...
    cheers Peter
    Yes but on 100 ipm it will have enought force i thing!?
    I dont know did i can connect spindle on arduino, if i can i'll think about the spindle and i will go with 12mm ballscrew.
    But one friend told me that he had the same system as mine, same steppers, drivers and PSU and he fried his PSU, and told me that i have to go with even bigger, 20A PSU.
    I will use bearings on steel profile...
    Thanks ????



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    Default Re: Cnc router electronics

    Hi GoCe - 4 x 3A motors is 12A max. All motors do not operate at max at the same time. Maybe half that or 60% max so 6A to 8A maybe. You can't fry the PS by drawing current from the motors. The driver has a current chopper to protect itself so you set the max current at 3A or 2A etc. The electronics guys can explain this better. If the PS fried it was shorted somehow not the motors fault... 100ipm is 2540mm/min which is not fast. I expect it will have lots of force to cut timber and plastic. Without doing the numbers I used similiar motors on Gecko 540 with 3A setting and usual cutting speeds where in the order of 1000-1500mm/min. I did finishing cuts on some jobs at 20,000mm/min I used a 20T pulley as well. I use a 16mm wide belt 5mm pitch AT type. Workes fine... Peter



  7. #7

    Default Re: Cnc router electronics

    You will not get good performance if you use your 269 oz in, 24V power supply and TB6560, I am sure

    For 120cm x 80cm cnc router, it is better to use 570 oz-in motor and 48VDC power supply

    I would suggest you to use the following parts

    Stepper Motor: 570 oz in
    https://www.automationtechnologiesin...23h2100-50-4bm
    Stepper Driver, 5056
    https://www.automationtechnologiesin...-driver/kl5056
    power supply, 48V
    https://www.automationtechnologiesin...upply/48v12-5a
    Breakout Board, UC100 USB and breakout board
    https://www.automationtechnologiesin...mach3-usb-card
    UCCNC software
    https://www.automationtechnologiesin...ntrol-software



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    Default Re: Cnc router electronics

    Hi,
    if buying 23 size steppers look for as low inductance as possible, 1mH preferred and reject anything over 2mH.

    In order to make low inductance steppers manufacturers use fewer turns of a thicker wire, which in turn requires more current to get the same
    torque. Thus the steppers you are looking for will tend to be high current devices, say 5A or more. The 570oz.in motor linked to by the previous poster
    has an inductance of 2.5mH, so on the high side but still quite respectable.

    I'm not a fan of switch mode supplies, they are too tender. Linear supplies like these:

    https://www.antekinc.com/power-supplies/

    Are very much more robust.

    One of the most common reasons for failure of witch mode supplies and/or stepper drives is BackEMF at deceleration. All motors generate
    energy back into its nominal supply when the motor is decelerating. The ability of the driver and/or supply to tolerate these overvoltage events
    is the principal difference between good and bad driver/supplies.

    Gecko is the industry standard for robust drivers but are not cheap. There are plenty of good Chinese made 80V drivers at very fair prices...get some.
    Remember you'll have these drivers and power supply for ten years or more if you buy well in the first place, but throw them out in months or less if you buy poorly.

    Craig



  9. #9
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    Quote Originally Posted by peteeng View Post
    Hi GoCe - 4 x 3A motors is 12A max. All motors do not operate at max at the same time. Maybe half that or 60% max so 6A to 8A maybe. You can't fry the PS by drawing current from the motors. The driver has a current chopper to protect itself so you set the max current at 3A or 2A etc. The electronics guys can explain this better. If the PS fried it was shorted somehow not the motors fault... 100ipm is 2540mm/min which is not fast. I expect it will have lots of force to cut timber and plastic. Without doing the numbers I used similiar motors on Gecko 540 with 3A setting and usual cutting speeds where in the order of 1000-1500mm/min. I did finishing cuts on some jobs at 20,000mm/min I used a 20T pulley as well. I use a 16mm wide belt 5mm pitch AT type. Workes fine... Peter
    Thanks peter, i want to use 20mm wide belt, but maybe 16 is enough.



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    Quote Originally Posted by automationtechinc View Post
    You will not get good performance if you use your 269 oz in, 24V power supply and TB6560, I am sure

    For 120cm x 80cm cnc router, it is better to use 570 oz-in motor and 48VDC power supply

    I would suggest you to use the following parts

    Stepper Motor: 570 oz in
    https://www.automationtechnologiesin...23h2100-50-4bm
    Stepper Driver, 5056
    https://www.automationtechnologiesin...-driver/kl5056
    power supply, 48V
    https://www.automationtechnologiesin...upply/48v12-5a
    Breakout Board, UC100 USB and breakout board
    https://www.automationtechnologiesin...mach3-usb-card
    UCCNC software
    https://www.automationtechnologiesin...ntrol-software
    Thanks friend, those electronics are good but expensive and i dont want to spend much money, and as i said this is a diy cnc build i think that 269 oz.in motors will be ok for cutting wood with 80-100 ipm, and i can only change 24v psu for bigger one, and i can use bigger stepper drivers. What do you think?



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    Default Re: Cnc router electronics

    Hi GoCe - You may have trouble fitting 20mm wide pulleys on your stepper shafts. So look at that closer. Plus look up the moment capacity of the motor bearing. If you mount the pulley away from the motor to use the wide pulley it will bend the shaft. Get larger shaft versions of the motor. Belts work best when tight and this tension will fatigue small shafts... Peter

    From your comment on rails I assume you mean steel section with skate board rails. If this is the case I suggest you look at round rails. They will cost th same and perfom much better. Many skate bearings on a rail although doable and initially looks good requires much alignment and many bolts and holes. Round rail is simpler and more accurate and will be similar cost. You can save $$$ on electronics (and upgrade later) but put the $$$ into things that matter more eg the motion system.



  12. #12
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    Quote Originally Posted by joeavaerage View Post
    Hi,
    if buying 23 size steppers look for as low inductance as possible, 1mH preferred and reject anything over 2mH.

    In order to make low inductance steppers manufacturers use fewer turns of a thicker wire, which in turn requires more current to get the same
    torque. Thus the steppers you are looking for will tend to be high current devices, say 5A or more. The 570oz.in motor linked to by the previous poster
    has an inductance of 2.5mH, so on the high side but still quite respectable.

    I'm not a fan of switch mode supplies, they are too tender. Linear supplies like these:

    https://www.antekinc.com/power-supplies/

    Are very much more robust.

    One of the most common reasons for failure of witch mode supplies and/or stepper drives is BackEMF at deceleration. All motors generate
    energy back into its nominal supply when the motor is decelerating. The ability of the driver and/or supply to tolerate these overvoltage events
    is the principal difference between good and bad driver/supplies.

    Gecko is the industry standard for robust drivers but are not cheap. There are plenty of good Chinese made 80V drivers at very fair prices...get some.
    Remember you'll have these drivers and power supply for ten years or more if you buy well in the first place, but throw them out in months or less if you buy poorly.

    Craig
    Thanks friend, i'll take a look at those psu, gecko is good but expensive, and i dont want to spend a lot of money, this is however diy cnc, and i think 269 oz.in will be ok even with bigger inductance, because i want to cut with 100 ipm, i can only change psu and drivers for bigger ones, what you think?



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    Default Re: Cnc router electronics

    Hi,

    and i think 269 oz.in will be ok even with bigger inductance,
    Good luck.

    Craig



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    Default Re: Cnc router electronics

    Power supplies: you can get good 'bricks' from ebay for very little $$.
    I replaced my under-sized transformer w diodes, caps etc, with bricks, and got 5 V, 24 V and 60 V all at 10 A.
    They have survived some mishandling.

    Cheers
    Roger



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    Quote Originally Posted by RCaffin View Post
    Power supplies: you can get good 'bricks' from ebay for very little $$.
    I replaced my under-sized transformer w diodes, caps etc, with bricks, and got 5 V, 24 V and 60 V all at 10 A.
    They have survived some mishandling.

    Cheers
    Roger
    Thanks man!!



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    Quote Originally Posted by joeavaerage View Post
    Hi,



    Good luck.

    Craig
    Thanks!!
    Can you just take a look at this motor..

    https://www.omc-stepperonline.com/nema-23-stepper-motor/nema-23-bipolar-1-8deg-2-83nm-400-oz-in-4a-2-26v-57x57x84mm-8-wires.html

    Last edited by Goce93; 08-21-2021 at 05:09 PM.


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    Quote Originally Posted by peteeng View Post
    Hi GoCe - You may have trouble fitting 20mm wide pulleys on your stepper shafts. So look at that closer. Plus look up the moment capacity of the motor bearing. If you mount the pulley away from the motor to use the wide pulley it will bend the shaft. Get larger shaft versions of the motor. Belts work best when tight and this tension will fatigue small shafts... Peter

    From your comment on rails I assume you mean steel section with skate board rails. If this is the case I suggest you look at round rails. They will cost th same and perfom much better. Many skate bearings on a rail although doable and initially looks good requires much alignment and many bolts and holes. Round rail is simpler and more accurate and will be similar cost. You can save $$$ on electronics (and upgrade later) but put the $$$ into things that matter more eg the motion system.
    Hi friend,
    Yes im going to use 16mm belt, and i will look for motors with larger shaft.
    And about the motion system, what you think about SBR16UU linear bearing block on steel/aluminum tubing, can it work??



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    Default Re: Cnc router electronics

    Hi
    the stepper to which you linked has an inductance of 1.8mH when wired i bipolar parallel and is a far better choice than you original 269oz.in 5mH ones.

    Craig



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    Quote Originally Posted by joeavaerage View Post
    Hi
    the stepper to which you linked has an inductance of 1.8mH when wired i bipolar parallel and is a far better choice than you original 269oz.in 5mH ones.

    Craig
    Yes, as you told me to choose under 2mH this is good choice and is not much more expensive that mine 269 oz.in and are 400 oz.in, so i will use them!
    Thank you



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    Default Re: Cnc router electronics

    They're 5.66A (parallel) which sounds really high (for 57x84 400oz) and would seem to rule out a lot of drivers, e.g. DM556.



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