question about motion control in cnc.

[avr_micro]

servo motor incnc

Hello.I have started to studing about cnc and i have some questions.please help me.
1-what kind of motors should we use in cnc (for moving in each direction such as x ,y ,z).
2-if we use a stepper motor and if we want to move from (x=2 &y=2) to (x=10 &y=5) how we can do this job because the difference of x is 8 step and difference of y is 3 step,while we know the divition of this two value is not a natural number (2.666666).how can a stepper#1 round 2.666666 step(while we know a stepper can round 1 or 2 or ... not 2.66666 step).
3-If we want to use a dc motor instead of stepper motor,how we can break it in suitable time immediately.
4-How we can get feedback from motors(in example when we transfer a command for motor(such as stepper or other motors)how we can find out it rounds 1step).
In the end if anybody has a good pdf about motor driving and cnc systems please upload it.
excuse me for my bad english.

 

[flatulent]

cnc controller circuit

One problem with the feedback approach is the nonlinearity and hysteresis involved in the mechanical portion. Even very small amounts of these will cause stability problems in the control system.

In the stepper motor approach you can gear down the drive so that the increments of motion are smaller than the specification for surface roughness. Also there is the possibility of microstepping the motors for finer resolution.

 

[Moof]

position torque loop servo cnc

A CNC use servo motors

 

[avr_micro]

good question about motion

1-how can i control servo motor.if you have any circuit please send.
2-how much resulation can i get from servo motor?
3-Have you any complete project for cnc(include of servo motor)?

 

[DarkJedi]

cnc servo project

Are you familiar with encoders and speed control????

Encoders give you control of position of the motor axis, this way you are able to know how much the axis have turn and you can control the position of the motor axis if you calculate how much of a turn you want .... with speed control, as a PWM you control the speed of the motor axis, combining this two ways, the feedback of the encoder and the control over the speed with the PWM you can get a pretty good control of the motor with a good pressicion wich depends on the pressicion of the encoder you use.

 

[sabri]

best cnc motion control

I think in CNC & Robotic ,To determine the position of Arm/Support we can use Resolvers .
Resolvers have low cost ,very economic and good precision.

Thanks.

 

[babara]

cnc motion control software

If you want make some small cnc machine you can use stepper motor, but only bipolar beacause this motor have higher torque. You must insert increment encoder to rotate devices becase that is the only way to recognize error in motion.
Using stepper motor is more chipper way to build cnc machine but only for low load and small mass machine. You can use gear box for dividing steps. In that way you get more torque but you will incrise max. speed of working. Please, specifide what kind of cnc you realy want to build and than i can help you with some other information.
I have some project in my office and if you have any questions or idea please contact me to my mail
babara@net.hr

 

[shangwa]

question of motion in hindi

1-how can i control servo motor.if you have any circuit please send.
2-how much resulation can i get from servo motor?
3-Have you any complete project for cnc(include of servo motor)?

1.CNC offen us AC servo motor in milling&
turning but stepper would be fine if accurancy is not important.
To control servo motor the best way is to use servo driver accomplished with servo motor or you have to design PWM control circuit and position loop.

2.it depends on encoder feedback resolution and ball screw pitch.Usually you have 10000 pulse/per rev or 2500 A/B phase pulses/rev

3.check www.linuxcnc.org

Good luck

 

[trend]

motion profile in cnc

uhrm.. you sound exacully like me about a year ago. I found out that you can purchase an inexpensive controller card (3 axis = ~140$ for xylotex board) and be done with it.. Then download/buy some software that will work with it OOB.

That is the easiest route (any possibly the cheapest).. If this project is just for fun, you can buy some stepper motor controller chips off jameco or other sites, then you will have to hook them up to an uC to control them..

Some unipolar motors can go forward/reverse (depends on how many wires they have).

you might want to subscribe to xylotex's usergroup on yahoo and ask your questions there... they are very quick.

Hope that helps out some