Synthesis of Four-bar Motion Generation Considering Worst Case Joint Tolerances
Abstract— Four-bar motion generation is used to synthesize a mechanism which passes through or approximate prescribed rigid-body positions. This work will discuss the motion generation of four-bar mechanism with position tolerance variations due to joint running clearance. The tolerance variations study will be based on the standards of American National Standard Institute (ANSI). The new design constraint introduced in this paper will consider the joint tolerances and incorporate it into the displacement position matrix of coupler points described in the conventional planar four-bar motion generation models. The synthesized planar four-bar mechanism will produce tolerance limits for moving pivots and link length from which any mechanism can be synthesized to satisfy the prescribed coupler points with their prescribed tolerances. The included example demonstrates the synthesis of a four-bar mechanism with joint tolerances. 1
Kinematic synthesis of RRSS mechanisms for multi-phase motion generation with tolerances
Abstract This paper presents a new technique for synthesizing spatial RRSS mechanisms to achieve phases of both precise rigid body positions and rigid body positions with tolerances. This method is an extension of the adjustable RRSS motion generation synthesis method developed by the authors [11]. By incorporating rigid body point tolerances in the rigid body displacement matrices and calculating mechanism solution loci for the prescribed rigid body positions under the tolerance limits, circle and center point regions can be calculated. R–R link solutions can then be selected from these regions. This paper considers two-phase fixed and moving pivot adjustment problems with fixed and adjustable crank and follower lengths.
The Diminishing Role of Social Work Administrators in Social Service Agencies
ABSTRACT The social service industry in the United States has experienced tremendous growth and change since the early 1970s. Unfortunately, the social work profession has not kept up with this growth and change. This article explores several issues that have emerged in social work administration that may contribute to the seemingly diminished role of social workers in administrative positions in social service agencies. They include the role that schools of social work play in educating social workers for administration, competition for administrative positions in social service agencies, and the differences which exist between administration in social service agencies and other types of organizations.