Rockwell Automation Motion Analyzer Software - Manual (Page 85)

Rockwell Automation Publication MOTION-UM004B-EN-P - October 2012 85
Sizing Your System Chapter 2
2.1.1.1.1. Mass Counterbalance
• Vertical load with a 100% mass counterbalance
Set the Inclination field to zero and enter a load mass two times greater
than the load into the Load Mass field.
• Vertical load with less than 100% mass counterbalance.
Set the Inclination field to zero and enter the load mass plus the
counterbalance mass into the Load Mass field. Add an external positive
force equal to the following into the Applied Force field:
F = (M
load
- M
counterbalance
) a
where a = acceleration due to gravity = 9.81 m/s
2
2.1.1.1.2. Force Counterbalance
For a vertical load with a 100% force counterbalance, you have two choices:
• Set the Inclination field to zero and enter the load mass into the Load Mass
field.
• Set the Inclination field to 90°, and enter the load mass into the Load Mass
field. Add an external negative force equal to the load weight into the
Applied Force field.
For a vertical load with less than 100% force counterbalance, set the Inclination
field to 90° and put the load mass into the Load Mass field. Add an external
negative force equal to the counterbalance force into the Applied Force field.
Be sure to add some allowance for friction. Hydraulic type counterbalances are
notorious for high friction, which is usually speed-dependent. Because a mass
counterbalance cannot easily handle this directly, take the friction force at the
maximum speed, convert the friction force to torque at the drive shaft and add
this torque to the Losses field in the Actuator tab.