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Which Motor is best suited

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techie

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a dc series motor is best suited for driving

I need to drive the X & Y axis of a shaft grinding machine using a servo motor. The torue required is equivalent to a 2-3HP ac motor. Since I cant use an AC motor for this due to jerky and intermittant load and high startup torque, what is the most cost effective solution for this application. A DC motor, a stepper motor. Is it possoble to use the motor used in hand drill machines. They are quite high torque and suited for jerky and intermittand loads
 

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sick_man

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servo drive box rutex

yes i think that using domestic drills will work
but prob not very well

there are sites and sites companies who will make to order
for this purpose you want a stepper motor and gear this allowing for high precission
 

solvarg

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techie said:
I need to drive the X & Y axis of a shaft grinding machine using a servo motor. The torue required is equivalent to a 2-3HP ac motor. Since I cant use an AC motor for this due to jerky and intermittant load and high startup torque, what is the most cost effective solution for this application. A DC motor, a stepper motor. Is it possoble to use the motor used in hand drill machines. They are quite high torque and suited for jerky and intermittand loads
What speed/torque ratio is needed? If you are thinking of an hand drill machine i guess it´s a low speed application.
I would propose a brush less PM AC motor. they give quite high torque and are verry robust.

Regards
 

techie

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The speed is slow. Imagine like driving the tool bed of a large lathe machine.

Can anyone suggest the approximate cost of
a) 3 HP stepper motor + power drive
b) 3 HP DC motor + power drive
c) 3 HP brushless serv + power drive

I just want to have an idea before starting on one of above

thanks
 

bunalmis

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Grinder motor may be AC async. motor.

If you use screw drive you dont need a lot of torque for XY positioner motors and you can use stepper or DC brush motor. (Speed may be reuce if you use stepper motor)

DC brushless and DC motor good choice but need complex controller unit.

Stepper motor dont need feedback. Therfore you can build simple controller.
 

hobbymat

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A 3 hp stepper motor? You'll have to sell all your family to buy one :)

More seriously: If you want a controlled movement, you can buy a rather big stepper (NEMA 34, triple stack) rated at around 5 amps. There are also driver modules for this size of steppers. Both cost something like 200 USD/Euros a piece, or less if you can find surplus motors somewhere. There are also kits for stepper drives available, if you want to build your own. You'll need a DC voltage source of 60 volts to achieve any good speed with steppers, but it's the easy part.

For more torque, I'd recommend a timing belt (i.e. toothed belt) with 1:2 or 1:4 reduction ratio. The bigger the ratio, the more speed you may need to get from the motor, and thus more operating voltage for the drives.

Tell something more about the machine. Does it have lead screws or some other method of moving the table? How many inches/mm of movement per crank revolution?

We just installed motors like above to an old&big MAS milling machine, and the table moves beautifully, even if it doesn't have ball screws, only normal trapezoidal screws with 5 mm pitch.


Interested to hear more,

Hobbie
 

techie

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The application is as described a shaft grinding machine. The Bed is about 20ft in length and the lead screw is used to move the X-axis. My approximation of 3HP is entirely empirical. It maybe much lesser. It is hard to move the lead screw by hand beacuse of the load. Since I have no mechanical background and am entirely an electronics guy, there may be many assessment mistakes that I am making.
 

hobbymat

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A big servo motor (either DC or AC) would be my choice for that big a machine. Servos are much better than steppers, and nowadays they can be controlled even with the same software as steppers. Just be sure that your chosen servo drive is a "digital" one, i.e. it has step/dir inputs for positioning purposes. And the motors shall have encoders for position feedback.

There are also analogue servo drives with control voltage input (typically -10...+10 volts), but they are not what you want. Or at least you'll then need an additional box that works as an interface for digital controller output (LPT port) and analogue drive input, something like e.g. Rutex has.


Hobbie
 

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