Computer-Aided Design of a Punch Assembly

Abstract

In the high-speed page printing systems used as peripherals to computers, the paper moves at a speed of around 30 in./s. The printing and punching of the paper has to be done when the paper is in motion. If the punching is not finished in a short enough time, the paper would get torn up by the punchette. In a typical punch assembly as used in modern page printing systems, a plunger is driven forward by the force of a solenoid. Plunger impacts the punchette which in turn punches a hole in the paper which is in motion. To minimize the flight time of the punchette with the object of increasing paper speed, the design parameters of the punch assembly must be carefully selected. In this paper, a model for the punch assembly is developed. The necessary equations for plunger and punchette motion are derived. The design parameters, such as the masses of the plunger and punchette, constants for springs used in the assembly, force generated by the solenoid, and the gap between the plunger and punchette, are varied using a Rosenbrock algorithm to minimize the flight time of the punchette. The results obtained indicate that by the use of a Computer-Aided Design approach optimal values of design parameters can be found before the development of prototypes and experiments.