1. I'm having trouble calculating the right steps/AppUnit for the servo motors im using...

Can anyone demonstrate how to calculate the correct settings so the motors move the correct distance ?

my setup consists of the following:

· 3.2:1 belt reduction - CNCRouterparts pro rack and pinion drive - http://www.cncrouterparts.com/pro-rack-and-pinion-drive-nema-34-p-226.html

· 35 Tooth Pinion and MOD1 Rack

any help would be very much appreciated

2. Bloody hell Derick do you realise with 35T and 3.2:1 you have 34mm pitch and with 2000Rpm motors you'll be getting in excess of 68M/min rapids.!!! . . . Tread careful mate the bloody gantry will flying off the end in blink of eye. . .Lol

Ok well you have 2500 count Encoders which will be quadrature so x4 gives 10,000 pulse per rev.
Then workout your Pitch which is 35 x Pi = 109.599mm per rev / 3.2(ratio)=34.361mm per rev

Now Calculation is 10,000 / 34.361 = 291.026 pulses per mm.

Hope you have a nice fast motion control card because you'll need nearly 300Khz to get full RPM from those motors.
Last edited by JAZZCNC; 17-03-2015 at 08:01 PM.

3. Yeah I will have to tame the beast pal. Nearly had one misshap when messing about with the speeds on the X with one motor disengaged and not slaved, I ramped the speed up a little and I capped myself!!

So if I enter that information I should get the correct movement when I enter movement in the MDI? For example: X100 F300 I should get 100mm travel at a feed rate of 300 correct?

4. Originally Posted by D-man
So if I enter that information I should get the correct movement when I enter movement in the MDI? For example: X100 F300 I should get 100mm travel at a feed rate of 300 correct?
Yep should work.! . . . But don't hold me to it. . Lol

5. Champion I will give it a bash pal cheers

6. Dean, I will be able to turn those rapids down tho correct?

7. Originally Posted by D-man
Dean, I will be able to turn those rapids down tho correct?
Yes just set velocity to what you feel happy with.!! . . Thou ideally you would have calculated the ratio better to make full use of the motors potential and give better resolution rather than wasting motors potential. To be honest with 6:1 ratio you'd have got away with 3000rpm 400w motors.

8. Actually I've just thought and I think EdingCNC is limited to 125Khz frequency. In which case you won't get the full 2000rpm from those motors with 2500ppr encoders. You'll only get 750rpm unless you use electronic gearing using the drives, if they have that feature.

For the full 2000Rpm you'll need a frequency of 333khz.

9. I think your right yeah I saw that in the settings... So will that affect the calculations?

10. What cpu card are you using and how are you handling positioning feedback from the servos?

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