Adaptive point design algorithm to generate toolpath in fast tool servo ultra-precision machining of freeform surface

Compared with traditional coaxial multi-reflection imaging systems, the off-axis imaging system using optical freeform has many advantages, including high design freedom, small optical system size and high energy utilization. Nowadays, optical freeform surfaces have been widely utilized in imaging and non-imaging optical systems. But correspondingly, freeform machining is more difficult than spherical and aspherical optical reflectors. In the turning process, toolpath plays a critical role because it will determine the accuracy of the machined surface. The conventional methods to generate toolpath include constant-angle method, constant-arc-length method and the combination of constant-angle and constant-arc-length methods. This article proposes a new method based on an Adaptive Point Design Algorithm (APDA) to generate a series of cutting points. It will generate the cutter’s toolpath based on the tangential height changes of the ideal surface. Through the simulation, the algorithm is verified that it can achieve the same accuracy when reducing the amount of data by about 40%, compared with the traditional constant-angle method. This makes freeform machining faster and provides the basis for precision machining of large-aperture freeform surfaces.