Computer Aided Design of Useful Spherical Watt I Six-Bar Linkages

This paper presents a software system for the kinematic synthesis of useful spherical Watt I six-bar linkages that can guide a body through five task positions. The design procedure begins with the specification of a spherical 3R open chain that reaches five specified task positions. The six-bar linkage is designed by constraining the 3R spherical chain to the topology of a Watt I spherical six-bar linkage. The CAD software SolidWorks is used to specify the 3R chain and the five spherical task positions. We describe the SolidWorks Add-In MechGen that reads the SolidWorks data and generates candidate linkages. Included in the task specification are tolerance zones that allow random adjustments to the task positions to search for defect-free linkages. An example is provided that demonstrates the five position synthesis of a useful spherical Watt I six-bar linkage.