Need source for DC axis motors


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Thread: Need source for DC axis motors

  1. #1
    Member nelZ's Avatar
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    Default Need source for DC axis motors

    Hello, I have all electronics to make a killer router table but my axis motors are way too big. Over 1 hp and large.
    I don't want to go stepper. I'm used to industrial CNC mills and retrofit one.
    Servos and encoders for me.
    Problem is I haven't found a source for the right motors. Too big or small.
    My drives can handle brush or brushless.
    If anyone has a clue I'd appreciate it!
    Thanks,
    Nelson

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    Default Re: Need source for DC axis motors

    Hi,
    the choices for DC motors are shrinking, they have largely been taken over by AC servos.

    I use Delta servos, a Taiwanese brand made in China. Good quality, support, documentation and free set-up and tuning software at fair prices. From my regular supplier (in China)
    I pay $438USD for a 750W B2 series (160,000 count/rev encoder) kit which includes the servo motor, the drive and cables. Pretty hard to beat that value.

    Craig



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    Member nelZ's Avatar
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    Default Re: Need source for DC axis motors

    Thanks for the info. I looked at Keling's new website. They have brushless. I've never used them. Does the Hall effect feedback eliminate the need for encoders? A machine I retrofitted had "resolvers" they used back then before encoders were invented/popular, I don't know which.
    I have 3 AMC BE25A20's with hall and encoder inputs.

    i build the braces that keep american teeth straight......tick tick tick


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    Default Re: Need source for DC axis motors

    Hi,

    They have brushless. I've never used them. Does the Hall effect feedback eliminate the need for encoders?
    No, Hall effect sensors are used to 'commutate' the drive, but for accurate positioning control you still require encoders.

    A machine I retrofitted had "resolvers" they used back then before encoders were invented/popular, I don't know which.
    Resolvers were used in days prior to encoders. The early encoders were expensive and fragile with limited resolution, and so resolvers remained popular
    for quite some time. By about the mid 90's they pretty much disappeared. Resolvers are still rugged and reliable but less accurate than modern encoders.

    The AMC BE25A20 is a discontinued product. Are you sure that you want to re-use them?. You will then be responsible for matching the motor to the drive and then tuning it.
    The AC servo that I suggested is perfectly matched to the drive and has a sophisticated 'Auto Tune' feature., which makes them easy to use. I hasten to add that just about all modern AC
    servos have similar features, so there are many brands to choose from.

    I suspect that by re-using the drives you have you might 'save five dollars but cost yourself a hundred'.

    Craig



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    Member nelZ's Avatar
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    Default Re: Need source for DC axis motors

    I've got 2-560 watt PM motors and 1-400 from dismantling my Shizuoka retrofit. They're way too large for a 2X4 router table. I will do heavy cuts in hardwood so I imagine 250 watt axis motors will do.
    My company had me retrofit the Bandit controller on the Shizuoka instead of buying a new machine so I know about saving 5 and spending a lot more. That took me 3 months of fiddling but got it done. About $8,000 parts, but my time? Major $$$
    I'll scope out the Delta. Thanks for the info.
    I've a Galil 1832 and Camsoft already so it might happen.

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    Community Moderator Al_The_Man's Avatar
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    Default Re: Need source for DC axis motors

    Also Tach's were also originally used on DC motor/drives, these had two loops to tune, the inner loop (tach) and the outer loop position loop This resulted in voltage feedback mode rather than the now preferred current/torque mode.
    The AMC AMC BE25A20 are nice transconductance/torque mode drives, but they have +-10v analogue input control, however.
    They are very easy to integrate with the right controller that has the right analogue output signal as they are non-intelligent drives, just simply amplifiers.
    The DC treadmill motors that are made by Johnson make nice servo motors with the addition of an encoder, as they have a rear shaft also to accommodate it.
    AMC have, or at least had some drives that were capable of using these.
    A little bit of a pity, AMC has dropped many of their products in favour of digital control. Together with Galil, made a nice control system.

    CNC, Mechatronics Integration and Custom Machine Design

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


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    Member nelZ's Avatar
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    Default Re: Need source for DC axis motors

    Thanks Al, You did help me a lot 12 years ago with my retro. Yes, tachs as well on that system.
    At the outset I was looking for PM motors in the 250 watt range and just twiddle it until it works in my semi retirement.
    ps, I've a lot of boards from that Bandit system I'd sell cheap

    i build the braces that keep american teeth straight......tick tick tick


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    Member mactec54's Avatar
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    Default Re: Need source for DC axis motors

    Quote Originally Posted by nelZ View Post
    Thanks Al, You did help me a lot 12 years ago with my retro. Yes, tachs as well on that system.
    At the outset I was looking for PM motors in the 250 watt range and just twiddle it until it works in my semi retirement.
    ps, I've a lot of boards from that Bandit system I'd sell cheap
    You are not going to do much with 250w motors 400w would be the minimum and 750w the norm for a machine 2 x 4 size, 250w will work for a laser or 3D printer it also depends on your Ballscrews or how you are going to move each axis

    Mactec54


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    Member nelZ's Avatar
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    Default Re: Need source for DC axis motors

    The motors I have are 2 - 560 watt motors. They're from the X and Y of a Shizuoka AN-S. It's like a Bridgeport, only twice the size and 5,000 lb. What you say is surprising but what do I know.

    i build the braces that keep american teeth straight......tick tick tick


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    Default Re: Need source for DC axis motors

    Hi,
    I have to agree with Matec, 250W is minimal.

    The Delta servos that I have been recommending are 60mm frame (24 size equiv) at 400W and smaller, including 200W and 100W.
    Noticably the 400W B2 series servo kit is $398 while the 200W kit is more! So why would anyone bother with 200W when you can get
    a 400W for less. The frame size is the same, but obviously the 400W servo is longer.

    The 750W B2 series servo is only $438, so only $40 more than the 400W. Admittedly the 750W has an 80mm frame so is a little bigger, which may or may not be an issue
    if you are retrofitting a machine.....but nearly twice the power for only an extra $40, seems like a no-brainer to me.

    Craig



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    Default Re: Need source for DC axis motors

    Quote Originally Posted by nelZ View Post
    The motors I have are 2 - 560 watt motors. They're from the X and Y of a Shizuoka AN-S. It's like a Bridgeport, only twice the size and 5,000 lb. What you say is surprising but what do I know.
    Yes, they are also old and minimal for that size machine, BridgePort retro fit machines normally have 750w minimum on the X Y Axis I usually were using 750w to 850w on X / Y axis for this size machine

    Not much changes when going to a CNC Router, it depends on what you are trying to move and at what speed, CNC Routers need to move quite fast, those old mills did not move fast but were heavy for the motors to move the mass, this is the same for a CNC Router instead of a large mass to move, you need to move what you have fast, so still need the same motor power / torque to get the job done, if you're stuck on this, most AC servo manufacturers have sizing software that you can down load, plug in your numbers you want to achieve with your machine specs and you will have an answer to what size servo you need for your machine

    If your CNC Router is light weight, then you may get away with 400w, just remember your max cutter size you will be using and how much torque it takes to make a cut.

    Those old motors you have, the same motors today are a third of the size for the same power / torque output

    Mactec54


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Need source for DC axis motors

Need source for DC axis motors