Geometric Modelling and NC Machining of Scroll Profiles Using Circular Biarcs Fitting

Abstract

Scroll configuration plays a very important role in the design of a scroll compressor. In order to comprehend the concepts of design and improve the flexibility of machining, the objectives of this paper are the regeneration of scroll profile, the study of the curve fitting and circular interpolation. Since the sample geometry is unknown, reverse engineering is used to obtain a sample scroll configuration. Then, by analyzing the configuration, the design paramters are retrieved. The geometry of the scroll is derived using conjugate surface theory. A deviation analysis between the theoretical curve and the actual curve is implemented to modify the design parameters. In order to generate a continuous smooth toolpath, a circular biarcs fitting method is adopted to approximate the toolpath of the scroll profile. The developed biarcs fitting method eliminates the problem in conventional straight-line approximation toolpath which leaves ridges on the finished surface of the workpiece. The toolpath generated by the proposed method is verified through the solid cutting simulation and the trial-cut on a three-axis machine.