## Re: RPM on steppers & StepServos

Originally Posted by imitheo
Have anyone ever look at the TBI MOTION ballscrew designing PDF ?

TBI MOTION Ballscrew

I used this design guide to know the Torque i would need to drive my gantry. If anyone could take a look with for me to be more confident about these calculations.

To get the cutting force on my endmill i used this KENNAMETAL calculator:

KENNAMETAL Calc

To see the maximum cutting force my end mill could hold, i got the milling parameters for the endmill i am using from kennametal and then inserted in the calculator.

So with the maximum tangential force i maxed my parameters using my spindle power. Finally i got 90N as my cutting force.

Anyone could take a look at these ?
Yes, take a look at my thread here:

http://www.cnczone.com/forums/linear...118-cnc-3.html

Look at post #21. There is a sample calculation.

You can try to recreate my graph in post #5 using an excel spreadsheet or whatever kind of math program you want to use. Then if you get the same results, both of us will know that our spreadsheets are good and you can then put your specific parameters in your spreadsheet for your machine

The motor torque table is here:
http://www.cncrouterparts.com/cdata/...rque_curve.pdf

That is two motors driving an 800lb gantry at 0.25G, And calculating how much force is left over at different RPMs. I didn't include preload drag or bearing drag and assumed an efficiency of 90%. See if you can recreate that graph.

Some references are here:

http://www.engr.sjsu.edu/bjfurman/co...iaformulas.pdf
https://www.aerotech.com/media/85449...d%20sizing.pdf
http://www.hiwin.com/pdf/ballscrews.pdf pages 26 and 27

Also, HSMAdvisor gives cutting forces and will tell you how much HP you need. Your machine is light and I doubt (correct me if I'm wrong) that you will have a really powerful spindle, so I don't think you will be making really aggressive cuts or subsequently need much cutting force.

But you can check it out and download it here if you wish: