TABLE OF CONTENTS The previous chapters discussed a number of acceptable cam functions for the critical extreme position (CEP) case, for double- and single-dwell cases, respectively. This chapter will discuss the design of custom cam functions to provide control of displacement, velocity, or acceleration over some range of motion as opposed to just the end-points of motion. This case is referred to as critical path motion or CPM. The variables used in this chapter are the same as those defined in Table 2-1 (p. 18).
Probably the most common application of critical path motion (CPM) specifications in production machinery design is the need for constant velocity motion. There are two general types of automated production machinery in common use, intermittent motion assembly machines and continuous motion assembly machines.
Intermittent motion assembly machines carry the manufactured goods from work station to work station, stopping the workpiece or subassembly at each station while another operation is performed upon it. The throughput speed of this type of automated production machine is typically limited by the dynamic forces that are due to accelerations and decelerations of the mass of the moving parts of the machine and its workpieces. The workpiece motion may be either in a straight line (as on a conveyor) or in a circle (as on a rotary table).
Continuous motion assembly machines never allow the workpiece to stop and thus are capable of higher throughput speeds. All operations are performed on a...
