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a question about stepper motor's speed

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alwindawee

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Hi all.

I build a CNC machine, the problem is it's slow, I was thinking that the steppers may be
slow or the screws notches are too soft.

by the way the distance between 2 notches is 1mm.

the stepper motors are unipolar 24V 200 step per round, I'm driving it at 100 RPM, and can not increase it.

is 100 RPM is natural for stepper motors or it's just slow ??

thanks in advance.
 
Higher input in frequency to the driver, makes the motor turn faster.

Up to a point; there is a point at which you can step faster than the rotor can turn - then things can go "wonky" (missed steps, back-stepping, stalling, etc). The specs for the motor will have all of this information, if you can get them.
 
what type of driver are you using to power the stepper? If it's a fixed circuitry I doubt much can be done. But if it's a PIC to control the pulse width, let's say, then reprogramming should do it.
 
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About driving at high voltage with current limit resistor, I did that, I also increase the freq. till it start spoil and not rotate so I'm driving at possible maximum freq. but I was thinking is my motor can be driven at more than 100 RPM.

at the other hand I can only change the screws that pull/push the stages because as I said I'm afraid that the screws has soft notches (the distance between 2 notched is 1mm), so think in this too.

I'm have designed the driver my self, simply I used PIC18F2550 as a driver and as an interface, it gets data from PC then drive the steppers.


NOTE: I designed the whole system my self.


thanks in advance.
 
If your motor is directly connected to your 1mm pitch ball screw, and you
could give up some torque and resolution, you could put a timing belt pulley
on the motor that has more teeth then the ball screw.
Example: if you put a 30 teeth pulley on the motor, and 15 on the ball screw
it should go 2 times it's current speed. if you can make the brackets to move
the motor all it would cost you is the cost of the pulleys and belt.

Tommy
 
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I can't understand why a lot of people are trying to use a PIC or other micro to run a stepper? With as many driver chips and driver modules out there, why make things more complicated. All the CAM software is written to drive a driver module or chip.

The drivers are all self contained and made to run most motor sizes/amperages (built in amp control choppers) With a micro you have to add mosfets or transistors to be able to handle the current. Most driver chips are cheaper than the mosfets needed.

Your speed problem is probably in your PIC code. Unless your machine itself has too much friction for your motors. What size/type motors are you using? If they are from a ink jet printer or something like that they probably don't have enough torque. The little round "can" motors are very weak.
 
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I can't understand why a lot of people are trying to use a PIC or other micro to run a stepper? With as many driver chips and driver modules out there, why make things more complicated.
When you live in Ohio you can get most any part made. People who live in other places, like Iraq or India, have to built their project with the parts the can get.
 
Hi, you still did not answer my question, is my stepper motor could driven faster than 100 RPM if my stepper motor details are as follows:

unipolar 24V, each winding resistance is about 25 ohm, by the way I bought the motors and did not get them from a junk.

I even used a driver chip it comes with the same result, also my CNC machine is working but some times I like to make it faster, after I tried several things with electronics of the driver and the motor it self I get nothing and I be content that it may be the screw which it's notches are very close to each others so when the motor rotate one turn the stage goes only 1mm, hope you understand my problem now.

I agree with you 3v0 also I building the diver your self will give you many options and if you did not tried that before you will not understand what I mean "shortbus= ".

what ever thanks all.
 
Well - now you're saying you have a "driver chip"; mind cluing us in to what that chip is (ie, a part number or something)? How about a schematic/spec/code for the system - maybe there's something hard-wired/hard-coded that is preventing you from speeding things up (but we don't have enough information except to make guesses)?
 
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