Optimization of a Multi-Drilling Sequence with MQL Supply to Minimize Thermal Distortion of Aluminum Parts

The drilling process with solid carbide tools with minimum quantity lubrication is under development in the automotive industry due to its high productivity and its environmental benefit. Because of the poor cooling performance when using MQL, a high amount of heat remains in the workpiece, which induces macroscopic thermal distortions and inaccurate parts. This paper presents a methodology to model the thermal distortion of a complex part having a large number of holes. The heat flux entering into the workpiece during each drilling operation is calibrated based on embedded thermocouples and on geometrical observations of the drill surface. Finally, it is shown how the model enables the optimization of a drilling sequence so as to minimize the thermal distortion and the accuracy of the machined part.