A Benchmark Comparison of Curvature Matched Machining Methods
C. Greg Jensen, Rob Cheatham, Zhenyu Chen, & Max Wang, Brigham Young University; Yifan Chen & Brian Bowman, Ford Motor Company

Five surface regions from a prerelease Ford GT concept vehicle were machined using CurvatureMatched Machining (CM 2) methods. Three commercial CAM algorithms were compared to a CM 2 code which had it beginnings at Brigham Young University, but is now being commercialized by Contour Numerical Control. The benchmark of these methods compared tool path lengths, computation time and visual inspection of the clay surfaces. CM 2 proved to be a superior method for the parts studied, with System 1 coming in a close second. Improved surface finish of parts machined with either CM 2 or System 1 was observed. CM 2 showed a significant reduction in tool path length as well as a reduction in computational path planning time. CM 2 also showed visual superior surface to the surfaces machined using System 1.

1. INTRODUCTION
Selecting a machining process for a part consisting of sculpted surfaces has traditionally been relegated to three-axis part programmers. However at the Ford Motor Company's Design Center clay concept vehicles have been machined using 5-axis mills for the past 12 years. Traditionally they have used ICEM DDN from ICEM Ltd. to program the mills. In a previous (2002) benchmark effort BYU's CM 2 was compared to DDN with the results indicating a strong advantage in using CM 2 over DDN. In 2003 students within the Direct Machining and Control Laboratory at BYU (a Utah State Center of Excellence for machining) took it upon themselves to compare CM 2 to three other top CAD/CAM packages (hereafter referred to as System 1-3) by machining, full-scale, five surface regions taken from a prerelease Ford GT concept vehicle, Figure 1.

Figure 1: Ford GT
The five regions consisted of the A-pillar, Window, Door, Back Corner, and Trunk Deck and Fender.

Below are CAD images of the surface patches that were machined, Figures 2 - 6. Within each CAM system algorithms that most closely compared to curvature matching were used. All machining parameter were chosen and held constant within each system so that no advantage would be gained during the tool

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