Generating Machine-Optimal Numerical Control Paths

Massachusetts Institute Of Technology, Cambridge MA

Investigators

Abstract

The objective of this research is to generate the fastest tool paths to sweep a three-dimensional surface. This will be accomplished by first developing a mathematical formulation which captures all the practical constraints of machining, including motor speed limits, acceleration limits, surface finish requirements, machine kinematics and the effects of path discontinuities. It is likely that the formulated problem will not yield a closed-form solution. Several numerical approaches will be tested. A "greedy" approach has shown initial promise. In this approach, the tool paths are denerated using a local optimality criterion in place of the global optimality criterion. A second approach is to generate candidate tool path families are using parametric "basis" curves. A third approach which will be studied is a global search; the surface will be broken into smaller and smaller elemefltts, and tool paths directions will be varied individually in each element. The third approach is computationally expensive, but is also likely to yield the best results. If successful, this research will yield faster tools paths for high speed machining. As the spindle speeds available in CNC machine tools have increased, linear actuation systems have increasingly become the bottleneck in machining performance. Upgrading to faster linear motor technologies is very expensive. The tool paths enabled by this research will better utilize the capabilities of todays machine tool structures with new spindle technologies, and enable greater productivity without significantly greater costs.