stepper or dc motor with feed back which is best for CNC at high speed

hi guys…
I am planning to make a cnc using arduino uno board but now I am in a situation to select the motor for my drives. As it seems that the stepper motor(Nema 23) is only giving about 300rpm which may leads to low speed for leadscrew carriage/ tool movement and I would like to et about 1000 rpm for motor

So can use some geared dc motor with some feed-back to get the result ?

some times I also seen that the stepper motor is skipping steps from arduino uno at higher speed 300 rpm!

THANKS

expecting helps from you…!!! :disappointed_relieved:

Which stepper motor, which driver, what supply voltage?

its unipolar stepper motor with 1.8 degree stepping angle similar to Nema 23, and I have used L239D ic to drive the coils and applied 12V 0.5A current, and used built-in example to test drive it. Some time motors turn and some times it just vibrate

Thanks

midhun_aka_ks: its unipolar stepper motor with 1.8 degree stepping angle similar to Nema 23, and I have used L239D ic to drive the coils and applied 12V 0.5A current, and used built-in example to test drive it. Some time motors turn and some times it just vibrate

Post a link to the datasheet for a motor.

It seems suprising that a Nema 23 motor is intended for 12v and 0.5A. I would expect them to need a few amps and 20v or 50v.

...R Stepper Motor Basics

I haven't followed CNC machining but I do remember that digital read out devices were used to track position. I don't see using a stepper without feed back of some sort in CNC machining. Use steps to position but the encoder would have the 'final word' in terms of the number of steps it made.

I think it comes down to the resolution needed. You can get 3/4" 10TPI all thread. Beefy is good in machining and 1/10" per turn divided by 200 steps per turn gives you 0.0005" resolution. Accuracy is another story but that is quite good compared to manual machines. Many accounts I've read said commercial all thread and bolts in general have pretty tight tolerances as a rule. The courser rod will help your speed.

Bottom line, you need to track the position, not just hope the machine did it as per the instructions.

midhun_aka_ks: hi guys.. I am planning to make a cnc using arduino uno board but now I am in a situation to select the motor for my drives. As it seems that the stepper motor(Nema 23) is only giving about 300rpm which may leads to low speed for leadscrew carriage/ tool movement and I would like to et about 1000 rpm for motor

So can use some geared dc motor with some feed-back to get the result ?

some times I also seen that the stepper motor is skipping steps from arduino uno at higher speed 300 rpm!

THANKS

expecting helps from you..!!! :disappointed_relieved:

Perhaps some more homework is needed.

You need to have an acceleration period for what ever you are moving using the stepper motor. How much mass does it have? Then are you needing to decelerate and stop the device, then hold it in position? How accurately does it need to be held? Is you device another motor that will try to move itself?

Your lead screw will need to be lubricated if it is to have much lifetime. Will your project create dust or abrasive particles? You may need to have shields on the lead screws.

Paul

midhun_aka_ks: its unipolar stepper motor with 1.8 degree stepping angle similar to Nema 23, and I have used L239D ic to drive the coils and applied 12V 0.5A current, and used built-in example to test drive it. Some time motors turn and some times it just vibrate

Thanks

Unipolar is game-over for CNC - you need a fast low-impedance bipolar motor driven by a chopper driver, and 24V/36V/48V/60V for the supply. You'll get 2000rpm perhaps with a good setup.

If you drive a lead-screw, you are needing as much speed as you can get, and unipolar steppers are not going to give you anything like that.

For a NEMA23 the kind of motor I'm thinking about would be in the 0.5 to 1.5 ohm range, several amps, and need a discrete stepper controller (no single-chip solutions much above 1.5A). These days there are 'cheap' stepper drivers at this current level: http://www.pbhonline.in/products/psd-5042-2p?utm_medium=cpc&utm_source=googlepla&variant=1089571764&gclid=CLiJr4qB7cgCFVAljgodNxIBzA

Also there are more affordable servomotors available for hobby CNC, but I think you'll find still a lot more expensive unless you can find a real bargain servo drive...

Oh, and someone mentioned allthread (studding) for a leadscrew - not ideal for CNC, low precision and will wear really fast compared to purpose-designed leadscrew. Eliminating backlash usually means hardened steel leadscrew and anti-backlash nut assembly, or for more money a ballscrew/ballnut.

Still you can start cheap and upgrade parts as an when - I think a lot of people do this.

Checkout the cnczone forum, you'll get much expertese and experience there I think:

http://www.cnczone.com/

OOpps...I think I need to have more homework for this project.. thanks a lot all..for all the valuable information