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IndustryArena Forum > CNC Electronics > Servo Motors / Drives > Trying to figure out high RPM servo motor with decent torque?
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  1. #1
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    Trying to figure out high RPM servo motor with decent torque?

    I am pretty stumped here..

    I am doing a retrofit on a brother TC-225 drill tap center. I am sourcing a spindle motor for the machine and am looking to use a synchronous servo motor so I can have rigid tapping capability.. but heres the stumbling point, I cant seem to find any servos with a rated speed of more than 3000 RPM. I would really like to find something in the range of at least 8000 if not 10000RPM. the stock motor was 6000. I plan to install a higher rpm motor and upgrade the bearings to allow for the 10000 rpm spindle.

    But again I cant seem to even find one 10000 rpm servo with something like atleast 15NM. What am I missing? how are all these other manufactures doing direct drive motors to spindle and getting 10-12000 rpm?

    Thanks for any help i am just ripping my hair out with this right now.:drowning:

  2. #2
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    akm64N? 6000rpm max, 17nm. many other 6000rpm windings to pick from. ... $ 2000-ish? (IIRC)

    why not faster? centrifigul force. higher require different mechanical designs, kevlar banding, etc. .... cost

    why not faster yet? can't field weaken a synchronous motor easily like an induction motor; hence 99% of hi speed motors are induction machines....

    willing to pay for it? we supply B404C (5000rpm max, 13.1nm) for some spindle apps - we kevlar band the rotor and respec it at 8000rpm max. $ 4000-ish (IIRC)

    limit is also near top what servo drive can output in hi freq....

    Or plain custom model for 8-10-12krpm easily - get what you pay for - prob around $ 8000-ish

  3. #3
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    I understand that there is obviously more cost in the servo, but what I want to know is, say in a Mazak 510 CNC mill, it has a 12000 RPM Spindle. I run that spindle at full speed 12,000 RPM for long periods of time. That machine has an independent spindle motor that connects directly to the spindle in line no gear box or belt drive. So obviously it is capable of standard speeds of 12,000 RPM and many other machines as well, yet I am having an extremely hard time finding any servo motors with anything near those capabilitys. Usually around 3000rpm 6000MAX which is only rated for an extremely short time. I want a servo motor for rigid tap capability's, Is there another spindle motor option that can attain those speeds (atleast 10000rpm) and have the control for rigid tapping and not be a servo? Any help would be appreciated.

  4. #4
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    I stand by my reply: 99% of hi speed motors are induction machines....

    The servos I listed are capable of their rated high speeds continuously same as your spindle motor so please do not respec them to be only 'intermittent duty' at their max speed limits - it ain't so.

    As I said, your 12krpm spindle is NOT a servo motor, it is an induction motor. Apples and Oranges.

    Now if you want to get into what differences are and why they matter, that is another discussion.

    We have supplied servo motors rated to 8000rpm for the quick turn around required on some very unique specialized rigid tapping machines; we have supplied 20-30krpm induction motors for high speed machining. Different animals and different applications. I have never heard of any machine tool capable of rigid tapping at 12krpm - yours will be a very unique machine.

    When we helped design the rigid tapping 8krpm machine, we spent days on motor sizing to make sure the motor could do the reversals required in the time required based on the mechanics being designed. That is how to go about getting a unique machine capable of what no one else can do - design it with proper motor sizing and paying attention to all the details.

    You ask if there are alternatives to do what you want to 10krpm; sure, design it yourself or buy it from someone who makes high speed high performance spindles. But be prepared to SPECIFY EXACTLY what you need in great detail. The likes of Setco Spindle in Cincinnati can build you such a spindle head - if you spec details. I would swag from your general comments it to cost about $ 75,000.00 (drive not included) from someone like them. The internal heart (motor) will probably be around $ 15,000 itself. The drive will come in around $ 10,000.00 also.

  5. #5
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    Mike, I want to start by saying that I am not disagreeing with you and as a matter of fact I greatly appreciate your input. I think I came across wrong with what I am looking for with a servo motor. I by no means am looking for a servo motor that is capable of rigid tapping at 12k RPM Id honestly be happy with 1500 RPM. At 10k I only plan to be doing milling mainly surfacing, but would still like atleast some torque at that rpm range to run at some higher feed rates doing normal milling. I am also not set on a servo motor as a spindle motor if there is any other options that would allow the necessary positional control of the spindle motor for rigid tapping

    My comment about the max speed of a servo motor was only from figures i had seen on a few servos I had looked at where over the speed of 3000 and at the max of 6000 was rated for a duty cycle of only a few minutes, I do not doubt that there are servos that are capable of sustaining there max speed, those are the things that I am here to find out about.

    I guess my needs for a spindle motor would be as follows:
    -10kRPM constant capability for milling strictly (would still like a bit of torque/power in this range)
    -Rigid tap capability (only to an absolute max of 2000RPM)
    -have these capability's with no gearing or belt drives

    and like I said any suggestion of another motor and control system that meets these needs I would be glad to hear about it!

  6. #6
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    Also I have tried to do some looking into using a non servo motor with a closed loop vector drive which seems like a possibility but I am having a hard time finding definitive information as well as hundreds of posts about Haas vector drives

    Anyone knowledgeable about Closed loop vector drives and rigid taping without a servo motor please chime in!

  7. #7
    Community Moderator Al_The_Man's Avatar
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    Rigid tapping is similar to threading on a lathe, the way it is normally achieved is with an encoder on the final spindle, not the motor.
    A closed loop system where the servo position are fed back and controlled by a single trajectory planner is usually capable of electronic gearing, that is where in the case of a mill, the Z axis is electronically geared off of the spindle encoder, therefore the system does not require a spindle that has servo capability.
    The Z servo tracks the spindle encoder.
    Al.
    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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    Al, so in simplistic terms I need a accurate measurement of spindle location through an encoder and a way to accurately and rapidly synch the z to the spindle location. for me an encoder on my spindle I would imagine is theoretically the same as on the motor as they are connected directly in line, or would the coupling provide a positional discrepancy between the encoder and actual spindle location under high load.

  9. #9
    Community Moderator Al_The_Man's Avatar
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    If the motor is directly on the spindle with no gearing etc, then it would be the same thing, but in the system I mentioned, the spindle encoder would go back to the motion card for the Z axis to electronically gear to it, your system would have to be capable of this.
    Any slight variation of the spindle motor or slow down - reverse the Z axis would just follow it.
    Al.
    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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    So after everyone's input and some more reading I've been doing I think that the best way to achieve what I Need as far as a spindle motor in a way that isn't insanely expensive, Is using an induction motor and a Vector drive. I understand that the vector drives give a much more predictable motor control as well as help with low rpm usage and better torque through the entire RPM range. Can anyone suggest a good Vector Drive? Also What kind of motor is standard used with a vector drive?

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    What Kind of motor specs do I need to have the reversing speed for rigid tapping?

  12. #12
    Community Moderator Al_The_Man's Avatar
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    If you want the maximum rpm also you may want to look at a vector rated motor such as the Baldor type that go up to 6000rpm.
    The maximum with a non-vector type is probably 3500-4000 max.
    Al.
    CNC, Mechatronics Integration and Custom Machine Design

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

  13. #13
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    as AL said,you will use encoder on spindle back to cnc and it will modify feed motor speed/position to MATCH what the spindle is doing.

    If you want best performance from the spindle to match, then the lowest inertia vfd rated motor you can find is the answer. That means long and SKINNY. Probably best standard motor like this is the blue and black max series from Marathon. They can be bought with the separately excited fan and encoder already on so it is plug and play for full rated torque from zero. sensorless prob will work for your needs but if you spend a tad more and get a vector vfd that accepts the encoder feedback also then it is better. We just happen to sell Hitachi & Refu brands, but as for brand, I would say as long as it is not one of those chinese cheapos it prob will be ok for you. You can spend x for one of the low cost ones (not chinese brand) or 2x and the difference will likely be 0-full current under control into motor in 200msec on x cost one vs 10 msec on 2x cost one - reason we sell 2 brands. Get quotes & specs on various models and decide.

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    Hey Mike and Al so it looks as though the options for something in the 10K rpm range is still challenging even when going to an induction motor? I looked at both of your recommendations but both seem to be in the realm of 3000 rpm

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    Well today I realized I needed to educate myself some more on understanding duty cycles of motors and the ratings for speed and power. I came across a good article here about spindle motors and gave me a better understanding of duty cycles and torque compared to rpm and kind of made a connection for me that I was missing.

    article: Selecting high-performance ac spindle motors | Technologies content from Machine Design

    I am looking at this Yaskawa AC Spindle Motor on ebay Yaskawa AC Spindle Motor Uaaska 08LYA11 7 5KW | eBay

    From my understanding now this motor can be ran at a 100% duty cycle at 7.5KW at 1500 RPM as well as sustain a 100% duty cycle at 5.5KW at 10,000RPM

    Is this correct?

  16. #16
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    Quote Originally Posted by PIVOTALCUSTOMS View Post
    Is this correct?
    yes. good price for the value if shipping doesnt kill u!

  17. #17
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    Mike If you'd be interested why don't you send me over a quote for a appropriate vector drive for that Yaskawa motor I posted?
    Pivotalcustoms@gmail.com

  18. #18
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    Re: Trying to figure out high RPM servo motor with decent torque?

    I would really like to find something in KFC Near Me

    the range of at least 8000 if not 10000RPM. the stock motor was 6000. I plan to install a higher rpm .

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