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This is a complex subject. You need textbooks and training on statics and dynamics. Contact your local Mechanical Engineer.

Robots have torque & mass moment of inertia limits stated explicitly for J5, J6 on their respective data sheets. Values are for maximum payload at maximum speed in all configurations of the arm that the manufacturer guarantees to achieve the stated repeatability. Values can be greater if speeds are reduced (in general).

Torque-maximum = (all static torques) + (dynamic torque) for each axis J5 & J6.

Static torque is torque effects about respective J5 & J6 axes due to gravity loads and also due to loads applied through EOAT reaction forces, hoses, etc., during operation. Calculations must be T-static = F*D for worst cases of distance D from respective axes.

Dynamic torque is T = I*Alpha = (MassMomentOfInertia)*(AngularAcceleration).

If CAD models of EOAT has mass properties enabled to give correct density/mass/weight values of components, then MMI can be obtained from CAD models of EOATs about J5 or J6 axes.

If not, then can be estimated with inertia primitives (blocks, cylinders, etc.) and manual calculations using I-totalDynamic = I-primitive + ML^2 (parallel axis theorem) about respective axes.

Alpha can be estimated from (Delta-max-angular-velocity) / (Delta-acceleration-time) for J5 or J6. Or calculate some useful percentage of max. Max velocity axes is from data sheet.

Put it all together and the calculated max torque and MMI values should not exceed values stated on data sheet.

Or, alternatively and less accurately, many robot manufacturers will provide charts in their user manuals to evaluate EOAT weight or mass at a distance from the J5 or J6 axis for a particular model of arm.

I agree. But there will be only few formulas to calculate, by which generally torque and inertia calculation softwares are made.Hope any one cracks and explains those.