# Inertia units: Payload Checker vs Robot (kg*m*s^2 vs kg*cm*s^2)

• Hey, all, stupid question: The Fanuc payload checker spreadsheet takes inertias in kg*m*s^2, but the robot payload setup screen takes kg*cm*s^2.

What's the conversion factor between these two units? I mean, if I'm handed a printout of the spreadsheet from the mechanical design department, how do I transcribe that into the robot? Do I just multiply by 100, since there's 100cm to every meter? Or is there another factor I need to be wary of here?

• The Fanuc payload checker spreadsheet has a nice conversion sheet that converts from SI units to 'Fanuc Units'. Do you have or can you get the spreadsheet? All the Fanuc reps have them.

Hey, all, stupid question: The Fanuc payload checker spreadsheet takes inertias in kg*m*s^2, but the robot payload setup screen takes kg*cm*s^2.

What's the conversion factor between these two units? I mean, if I'm handed a printout of the spreadsheet from the mechanical design department, how do I transcribe that into the robot? Do I just multiply by 100, since there's 100cm to every meter? Or is there another factor I need to be wary of here?

You were right on with the multiply by 100. I looked at the current payload checker and found this conversion listed there:

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• Thanks. Someone handed me a printout of the Checker that they ran -- I didn't think of trying to re-run the spreadsheet myself.

• I got you. I posted this elsewhere as a duplicate.

You want to put in the primary values Ixx, Iyy, and Izz from the CAD export. I assumed the values are from the flange and not about the center of mass. Corrected: Values are about center of mass.

Select kg and m for the units for CAD.

Use this: 1 kg*m2 = 10.197 kgf*cm*s2

If you need convincing, the conversion is as follows:

First, know that 1kgf = m*g = kg * (9.81)m/s^2=9.81N

-Then, multiply by (s^2/s^2)

kg*m^2*(s^2/s^2) = (kg*m/s^2)(m)(s^2)

Note: 1 kg*m/s^2 = 1N

Substituting, you have

(kg*m/s^2)(m)(s^2) = (N)*m*s^2

Next, you sub 1kgf = 9.81N

(N)*m*s^2 *(1kgf/9.81N) = kgf*m*s^2/9.81

Finally, convert m -> cm: 1m/100cm

(kgf*m*s^2/9.81)(100cm/1m) = (100/9.81) kgf*cm*s^2

=10.194 kgf*cm*s^2