IMPROVEMENT IN MOTION CHARACTERISTICS OF CAM-FOLLOWER SYSTEMS USING NURBS

Abstract

Absrtact. This paper proposes an integrated system for improving the cam-follower performance. The design method is to improve the motion characteristics of a cam follower-system. Improvement of the motion characteristics is to achieve low maximum velocity and acceleration for each follower motion curve so that jerk is minimum. Representing basic follower motion curves with nonuniform rational B-splines (NURBS) can do this. Conventional methods in designing and manufacturing of cam are tedious and time consuming. Even programming them on a computer numerical control (CNC) machine can be a difficult job because of the complexity of the cam profiles. . A CAD/CAM system is developed, which provides useful design information such as graphical and numerical representation of displacement, velocity, acceleration, jerk, pressure angle and cam profiles for both basic curves and NURBS. An analysis can be carried out based on maximum velocities and accelerations to select the best cam follower motion. It also provides cam profile coordinates for basic curves and NURBS to manufacture a cam on CNC machines. . A plate-cam is a disc-cam, which is cut out of a piece of flat metal or plate and used to transform a rotary motion into a translating or oscillating motion to its follower. Applications of these cams found in packaging machines, wire-forming machines, internal combustion engines, mechanical and electronic computers. Requirements for high performance of such machinery demand efficient methods for the design and manufacture of cams. The purpose of this paper is to develop a seamless integration of design and manufacturing of plate cams. NURBS have been used to design and optimization of cam profiles. The design parameters will be used in the manufacturing module that generates the NC program required for the machining of the designed cam.