This paper presents a general method for treating nonassembly in the optima
l synthesis of planar mechanisms. The synthesis is performed with gradient
based optimization algorithms and the sensitivities are calculated analytic
ally through the method of direct differentiation. The analysis is based on
the well-established and general method of computational kinematics. In th
is study the residuals of the joint constraint equations are minimized rath
er than equated to zero. This makes it possible to perform the kinematic an
alysis for any proposed design even though it may not be possible to assemb
le the mechanism. Several examples are provided.