Thermo-mechanical tool setting mechanism for ultra-precision milling with multiple cutting edges

Abstract

Ultra-precision milling operations are particularly ineffective machining processes, due to the fact that they are typically operated with a singular cutting edge (fly-cutting). For meeting the tight tolerances of optical and high precision surfaces, a nanometer precision tool setting mechanism is mandatory when adding more cutting edges. On the basis of a theoretical assessment of the surface generation, this paper presents a novel tool setting mechanism based on a thermo-mechanical actuator that has specific advantages compared to electrical or mechanical solutions. The prototype design for a two-tool holder for diamond milling using this actuator is presented and the choice of substrate material is assessed by FEM simulations. It was found that 1.2083 type steel potentially offers a larger stroke and therefore was chosen for the prototype. Next, the requirements for the heat input are discussed and a novel device for quasi-continuous heating during spindle rotation—an IR-LED ring light—is presented. Using the ring light, it is demonstrated that the tool holder can be selectively heated and a localized expansion of up to 1μm is achievable at a spindle speed of 240min-1.