With increasing demands in manufacturing for smaller and more precise features, the advent of micromechanical machining processes, such as microdrilling and micromilling to create features at the microscale are of increasing importance. However, at the length scales found in micromechanical machining, localized variation in the microstructure (such as grain boundaries and grain orientation in polycrystalline materials) can greatly affect the machinability and final process outcome in terms of surface and edge condition; defects such as excessive roughness and burrs are of particular importance. A focused set of micromachining experiments were conducted on single crystal materials in order to further understand how surface and edge condition are affected by material crystallographic orientation. A clear correlation between burr height and crystallographic orientation was found, giving insight into optimal orientations and process parameters for acceptable micromachining process outcome.

Author(s): Litwinski, Kai M; Min, Sangkee; Lee, Dae-Eun; Dornfeld, David; Lee, Nakkyu | Abstract: Micromachining applications have received increased emphasis in recent years with the advent of new precision manufacturing applications which have stringent requirements for surface and edge finish. One of the main concerns in mi- cromachining is burr formation which can incur high production costs due to time-consuming deburring operations. Although deburring operations are commonly carried out in macroscale milling, in micro machining they can be difficult to use. De- burring processes can destroy delicate microfeatures and are usually unfeasible at the micro scale. For this reason, the utiliza- tion of burr minimizing machining tool paths is desirable. Optimum tool paths minimize burr formation while satisfying sur- face quality requirements, dimensional tolerances, and cycle time constraints. A new concept for micro end milling tool paths is developed. An integrated performance index using the Taguchi method is introduced to optimize the main microscale end milling process outputs: surface quality, edge accuracy, burr formation, and time constraints. In addition, the concept is ap- plied to macroscale milling and its scalability down to the micromilling scale is studied.