A PC-based computer-aided manufacturing system for three-axis milling of aircraft structures.

摘要

This research illustrates the development of a personal computer (PC)-based computer-aided manufacturing system, which was applied in the machining of aircraft structures. The developed system contains a design module, tool path generation routines, postprocessing routines, and a verification routine.;The design module allows the user to construct the wireframe model of three-dimensional (3-D) geometries made up of lines and arcs through a series of entity creation and editing operations. Several view functions are also included so that the user can observe the constructed geometry in any direction of view and with different scales.;Five tool path generation routines are implemented in this system. They are the contouring routine, the two-dimensional (2-D) and 3-D spiral pocketing routines, and the 2-D and 3-D zigzag pocketing routines. The boundary of the pocket can be either closed or half-open. The half-open boundary contains segments which can be crossed by the tool. The generated tool path is comprised of offsets from the boundary specified by the user. The offsets are determined by using a newly developed offset computation method which allows different offset distances, does not create circular motions around external corners, and can be applied to half-open pocket.;The postprocessing routines produce the numerically-controlled (NC) program for the machining task based on the generated tool path. The ramping strategy adopted in these routines avoids the build-up-edge problem due to plunging and minimizes the times to move the tool through the clearance plane. These routines allow the user to specify different feedrates for linear and circular motions.;The verification routine checks the format and feedrates of the existing NC program and displays the commanded tool motions on the screen so that the tool path can be visually examined. This routine is developed to save time from verifying NC programs by running the machine in air.;This system has produced four different aircraft structures satisfactorily.