CNCzone Network:

# Thread: g320 step for Mach3

1. ## g320 step for Mach3

What would the steppes be in Mach3 for a 5mm lead screw that is direct coupled to servo and it has a 250 count encoder. And does kernel affect steppes
Thanks

2. Hi,
If the encoder is 250 counts then it would be 250/5 = 50 steps/unit. If the encoder is 250 lines resulting in 1000 counts then it would be 1000/5 = 200 steps/unit. (At 1:1 gearing)

The kernel speed determines the maximum speed that you can set the motors to in the motor tuning dialog. If set to 25kHz and you have 200steps/mm then your maximum speed (if you max out the velocity slider in the motor tuning dialog) is 25000/200=125mm/s or 7500mm/min.

Generally you should never set the kernel speed higher than you need. Ie don't increase the kernel speed unless the velocity slider is maxed out and you still need more speed.

/Henrik.

3. I still not for sure what to set steppes in Mach3. I have a 5mm screw but I am working in inches in Mach3.

4. Oh, I didn't know that.

1 inch is 25.4mm, so if you have 200 steps/mm you have 200*25.4=5080steps/inch.

5. Thanks

6. Ok see if you can help me figure this out. I have a heds 5701 f00 which is 256 counts. My motor gear is 14 teeth the other is 24 teeth. A 5mm lead screw. In Mach I have my steppes set 8960.544216. It cuts with in 2thousands of inch. I'm satisfied with this. But I have had to work with these numbers a lot to get this accuracy. Why does the above formula not work?
Thanks Ed

7. Why don't you just use the "Calibrate Axis" function in Mach3 and let the program do it's own math?

8. Hi,
Lets see...

(256*4) * (24/14) / 5 = 351.0857 steps/mm
351.0857 * 25.4 = 8917.577 steps/inch

That's around 0.5% off from what you get which might be accounted for as pitch error of the screw. 0.5% for a garden variety lead screw probably isn't too bad, if it was a ballscrew I'd be a bit surprised. But really, as long as it's accurate and repeatable to whatever specs you actually need the real number of steps/unit doesn't really matter much.