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  1. #1
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    New servo selection?

    I know motor selection has probably been beat to death, but I’m new to servos, so here goes.

    The following is what I know about factory ac servos on the mill that I have.

    Apparently reusing them is a pipe dream even with replacement encoders.

    Now what parameters do I need to match or slightly exceed to get a decent sized motor.

    I know with steppers the stall torque is a good place to start, but I don’t know enough about servos to be dangerous.

    So please help me understand what I need to be looking at to get servos that will move this mill well.

    Thanks
    Duke


    X-Y axis
    HA40CS
    Rated Torque
    30.0 kg/cm at stall (2687 oz.in.)
    27.2 kg/cm at 1000 RPM
    24.4 kg/cm at 2000 RPM
    Max. RPM 2000
    Weight 8 kg

    Z axis
    HA80CS
    Rated Torque
    60.0 kg/cm at stall (5375 oz.in.)
    54.4 kg/cm at 1000 RPM
    48.7 kg/cm at 2000 RPM
    Max. RPM 2000
    Weight 12kg

    Motor HA40CS 3Phase
    Input in 100% (kVA) 1.0
    Input in 100% at 170V 3.4

    Motor HA80CS 3 Phase
    Input in 100% (kVA) 1.6
    Input in 100% at 170V 5.4

  2. #2
    Community Moderator Jim Dawson's Avatar
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    Re: New servo selection?

    Take a look at the DMM servos. https://store.dmm-tech.com/collectio...0Servo%20Motor

    1kW for X and Y axis, 1.3 or 1.8kW for the Z axis. I would match the motor frame to the original motor frames, makes installation easy, just bolts in.

    I have 4 of their 1.8kW units on my CNC lathe and they have been operating flawlessly for the last 2 years running production every day, and have used them in other applications also.
    Jim Dawson
    Sandy, Oregon, USA

  3. #3
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    Quote Originally Posted by Jim Dawson View Post
    Take a look at the DMM servos. https://store.dmm-tech.com/collectio...0Servo%20Motor

    1kW for X and Y axis, 1.3 or 1.8kW for the Z axis. I would match the motor frame to the original motor frames, makes installation easy, just bolts in.

    I have 4 of their 1.8kW units on my CNC lathe and they have been operating flawlessly for the last 2 years running production every day, and have used them in other applications also.
    Thank you for the suggestions.

    For my own understanding what in the specs of my originally fitted motors led you to suggest the 1kW for X-Y and 1.3 or 1.8 for Z

    Thank you
    Duke

  4. #4
    Community Moderator Jim Dawson's Avatar
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    Re: New servo selection?

    Quote Originally Posted by jduke View Post
    Thank you for the suggestions.

    For my own understanding what in the specs of my originally fitted motors led you to suggest the 1kW for X-Y and 1.3 or 1.8 for Z

    Thank you
    Duke
    First you look at the torque required, then the RPM. Then I also looked at the drive specs you provided. So that, plus my general refitting experience led me to those motor sizes. In general, a 0.75kW servo will be in the range for axis drives on a Bridgeport type machine. A larger bed mill may be more happy with a 1kW X/Y axis drive, and with the higher mass of the Z axis, normally you would want to step up to a larger motor. Also, you may want the Z axis motor equipped with a brake, for power off position holding, depends it the Z axis is counter weighted or not.
    Jim Dawson
    Sandy, Oregon, USA

  5. #5
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    Quote Originally Posted by Jim Dawson View Post
    Take a look at the DMM servos. https://store.dmm-tech.com/collectio...0Servo%20Motor

    1kW for X and Y axis, 1.3 or 1.8kW for the Z axis. I would match the motor frame to the original motor frames, makes installation easy, just bolts in.

    I have 4 of their 1.8kW units on my CNC lathe and they have been operating flawlessly for the last 2 years running production every day, and have used them in other applications also.
    Thank you for the suggestions.

    For my own understanding what in the specs of my originally fitted motors led you to suggest the 1kW for X-Y and 1.3 or 1.8 for Z

    Thank you
    Duke

  6. #6
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    Re: New servo selection?

    Quote Originally Posted by jduke View Post
    Thank you for the suggestions.

    For my own understanding what in the specs of my originally fitted motors led you to suggest the 1kW for X-Y and 1.3 or 1.8 for Z

    Thank you
    Duke
    For another option. I bought a Lichuan A4 & 1.8kw motor for my mill spindle.
    Once I got my head around the wiring, it's a nice bit of kit.
    (Wiring wise, the B2 diagrams look easier).

    https://lichuanmotor.com/
    https://www.aliexpress.com/store/1907567

    I often see other folk with servo's of 750w on X / Y and 1-1.3kw on Z.

  7. #7
    Community Moderator Jim Dawson's Avatar
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    Re: New servo selection?

    Quote Originally Posted by jduke View Post
    Thank you for the suggestions.

    For my own understanding what in the specs of my originally fitted motors led you to suggest the 1kW for X-Y and 1.3 or 1.8 for Z

    Thank you
    Duke

    See my post #4 above
    Jim Dawson
    Sandy, Oregon, USA

  8. #8
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    Quote Originally Posted by Jim Dawson View Post
    See my post #4 above
    Sorry I double tapped accidentally posted same thing second time

  9. #9
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    Quote Originally Posted by dazp1976 View Post
    For another option. I bought a Lichuan A4 & 1.8kw motor for my mill spindle.
    Once I got my head around the wiring, it's a nice bit of kit.
    (Wiring wise, the B2 diagrams look easier).

    https://lichuanmotor.com/
    https://www.aliexpress.com/store/1907567

    I often see other folk with servo's of 750w on X / Y and 1-1.3kw on Z.
    Thanks for the suggestion


    These machines at one point were sold with steppers with a belt reduction
    With specs as follows

    200 steps/rev
    140 oz. in.
    125 watts
    Parallel: .13 Ohms 4.6 A
    Series: .52 Ohms 2.3 A
    Shaft: .375" x 1"
    Size: NEMA34

    I’m thinking that since they were such anemic steppers, they went way overkill with the servos that they put on it.

    After looking at the price of 750w and 1kW I may go back with closed loop steppers since I can get 12nm nema 34 closed loop steppers for about 1/2 the price of 1kW servos.

    Duke

  10. #10
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    Quote Originally Posted by dazp1976 View Post
    For another option. I bought a Lichuan A4 & 1.8kw motor for my mill spindle.
    Once I got my head around the wiring, it's a nice bit of kit.
    (Wiring wise, the B2 diagrams look easier).

    https://lichuanmotor.com/
    https://www.aliexpress.com/store/1907567

    I often see other folk with servo's of 750w on X / Y and 1-1.3kw on Z.
    That’s an attractive price point.

    And you like the 1.8kW as a spindle motor?

    Thanks
    Duke

  11. #11
    Community Moderator Jim Dawson's Avatar
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    Re: New servo selection?

    What machine are we talking about here? The steppers you list are a far cry from the existing servos.
    Jim Dawson
    Sandy, Oregon, USA

  12. #12
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    Re: New servo selection?

    Quote Originally Posted by jduke View Post
    I know motor selection has probably been beat to death, but I’m new to servos, so here goes.

    The following is what I know about factory ac servos on the mill that I have.

    Apparently reusing them is a pipe dream even with replacement encoders.

    Now what parameters do I need to match or slightly exceed to get a decent sized motor.

    I know with steppers the stall torque is a good place to start, but I don’t know enough about servos to be dangerous.

    So please help me understand what I need to be looking at to get servos that will move this mill well.

    Thanks
    Duke


    X-Y axis
    HA40CS
    Rated Torque
    30.0 kg/cm at stall (2687 oz.in.)
    27.2 kg/cm at 1000 RPM
    24.4 kg/cm at 2000 RPM
    Max. RPM 2000
    Weight 8 kg

    Z axis
    HA80CS
    Rated Torque
    60.0 kg/cm at stall (5375 oz.in.)
    54.4 kg/cm at 1000 RPM
    48.7 kg/cm at 2000 RPM
    Max. RPM 2000
    Weight 12kg

    Motor HA40CS 3Phase
    Input in 100% (kVA) 1.0
    Input in 100% at 170V 3.4

    Motor HA80CS 3 Phase
    Input in 100% (kVA) 1.6
    Input in 100% at 170V 5.4
    What is the Mill, they are quite big motors are they 1:1 or have a different ratio
    Mactec54

  13. #13
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    Quote Originally Posted by mactec54 View Post
    What is the Mill, they are quite big motors are they 1:1 or have a different ratio
    These are for a dyna mechtronics dm4400m
    And yes the steppers that they put on it were grossly different then the ac servos.
    As I understand it the steppers did have a belt reduction but I’m not sure what the reduction is.
    The ac servos are 1:1 on the belts but later ones may be directly coupled.

    The head does have a counterweight.

    Duke

  14. #14
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    Quote Originally Posted by dazp1976 View Post
    For another option. I bought a Lichuan A4 & 1.8kw motor for my mill spindle.
    Once I got my head around the wiring, it's a nice bit of kit.
    (Wiring wise, the B2 diagrams look easier).

    https://lichuanmotor.com/
    https://www.aliexpress.com/store/1907567

    I often see other folk with servo's of 750w on X / Y and 1-1.3kw on Z.
    Do the lichuan motors take step/dir input? Or 0-10v input

  15. #15
    Community Moderator Jim Dawson's Avatar
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    Re: New servo selection?

    Quote Originally Posted by jduke View Post
    Do the lichuan motors take step/dir input? Or 0-10v input
    Based on the specs, they take both step/direction and +/- 10V analog.

    From the web page:
    1. Three control mode support, Position control, speed control, torque control

    2. With Pulse + direction, CW/CCW, AB pulse three pulse modes;
    3. Support pulse feedback frequency division function;
    4. ±10V analog voltage control;
    Jim Dawson
    Sandy, Oregon, USA

  16. #16
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    Quote Originally Posted by Jim Dawson View Post
    Based on the specs, they take both step/direction and +/- 10V analog.

    From the web page:
    1. Three control mode support, Position control, speed control, torque control

    2. With Pulse + direction, CW/CCW, AB pulse three pulse modes;
    3. Support pulse feedback frequency division function;
    4. ±10V analog voltage control;
    Thank you , I’m still trying to wrap my head around wiring differences between steppers and servos.
    Are there any good videos that you can recommend on the basics of wiring servos to either Mach3 or uccnc ?

    Also from measurements it looks like the ac servos on my machine are nema 51 frame while the steppers used on previous dyna dm4400 were nema 34 steppers.

    Thanks
    Duke

  17. #17
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    Re: New servo selection?

    Quote Originally Posted by jduke View Post
    That’s an attractive price point.

    And you like the 1.8kW as a spindle motor?

    Thanks
    Duke
    Yes I do.
    I realise that my little mill is no comparison to the one you're referring to (now I know what it is... VMC).
    Bottom line is that they work well.
    Take S/D signals and/or analogue voltage.
    Position / speed / torque.. or hybrid modes.

    You'd prob put the 1.8kw in place of the HA40CS' by the looks of it.

    I wouldn't look at 12nm steppers. I've tried those out and binned them before now. They need drives with full AC mains voltage afaic.

  18. #18
    Community Moderator Jim Dawson's Avatar
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    Re: New servo selection?

    Quote Originally Posted by jduke View Post
    Thank you , I’m still trying to wrap my head around wiring differences between steppers and servos.

    By definition, a servo system is a closed loop system. The term servo does not define a motor type contrary to what the marketing types would have you believe. Your home heating/AC system is a servo system, the loop is closed by the thermostat and you, as the user, define the comfort level parameter by setting the thermostat. Another common example of a servo system is your car. You, as the controller, take various inputs from what is going on around you, process the data, and output the appropriate (we hope) actions to the steering, throttle, and brakes. On a machine tool, the loop is closed by the encoder feedback to either the servo drive or the controller.

    Servo motors can be brushed DC, brushless DC (also called AC servos), or closed loop steppers, there may be some other variations, but not common. The common theme with all of these motor types is a permeant magnet rotor (armature)


    On the low end there is the open loop stepper stepper system, this is the most popular for many hobby uses because it's inexpensive. In this case the controller sends out a pulse train and direction signal to the stepper drive but there is no feedback and the controller just assumes that the motor is doing what it is commanded to do. But the controller has no idea what is actually happening. Not the best for accurate work, but it does work pretty well.

    The primary wiring differences are that on a closed loop system there some kind of position feedback device (encoder) tied back to either the drive or controller. Other than that, the wiring is pretty much the same. You would connect the command signals to the drive (step & direction or analog). Then most likely also have an enable signal.
    Jim Dawson
    Sandy, Oregon, USA

  19. #19
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    Re: New servo selection?

    Quote Originally Posted by dazp1976 View Post
    Yes I do.
    I realise that my little mill is no comparison to the one you're referring to (now I know what it is... VMC).
    Bottom line is that they work well.
    Take S/D signals and/or analogue voltage.
    Position / speed / torque.. or hybrid modes.

    You'd prob put the 1.8kw in place of the HA40CS' by the looks of it.

    I wouldn't look at 12nm steppers. I've tried those out and binned them before now. They need drives with full AC mains voltage afaic.
    What makes you say replace the ha40cs with the 1.8kW?

    I was just looking at the 1kW and it says it’s rated at 4nm which is a little higher than the 2.94nm that the HA40cs rates as it’s stall torque of 30kg-cm.

    I have used the 12nm closed loop steppers on a 4x4 router, and like them for that application, but I can understand that my familiarity doesn’t make them right for this new application.

    That’s why I am trying to wrap my head around the use of servos on mills so frequently while routers still commonly use steppers.
    I am assuming it has to do with the opposition to movement that cutting metal provides that causes the need for more torque at higher feed speeds.

    I also have avoided servos in the past due to what I assumed was complicated wiring. Apparently that is not as true as it once was, they don’t seem substantially more complicated than a closed loop steppers from what I have read recently.

    Price has always, and will continue to be a deciding factor, as this is entirely a hobby for me, but again the price of some of the lower cost servos is not so far above closed loop steppers as to make them out of reach.

    Although I could get a couple of the 12nm Nema 34 closed loop steppers for $165 each vs $430 for a 1kW servo.

    Duke

  20. #20
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    Re: New servo selection?

    I just checked another calculator online, and the 30kg-cm and 60kg-cm respectively came back as about 3 and 6Nm

    So that would put the above advice of 1kW ac servo for x and y as well as 1.8kW for Z as pretty much spot on replacements.

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