Sensitivity analysis for considering the process dynamics during the calibration of process force models

When analyzing milling processes, various characteristics such as process forces and tool deflections can be investigated using process simulations. The analysis of cutting forces is subject to the dynamic effects of the tool and workpiece, whereby the force measurement technology used has a further influence due to its own modal properties and its specific force transfer behavior. Particularly during finishing with spherical milling tools, the variation of radius and helix angle along the cutting edge leads to variations of the engagement situation and effective cutting speed. These different geometric properties and orientations of the tools infuence the process forces and dynamics and their interactions. Due to various influences on force measurements and dynamic superimposition, a higher model quality can be achieved through a sophisticated calibration methodology.

In this paper, a methodology is presented in which the effects of tool dynamics are included in the calibration of force model coefficients to improve the accuracy of the resulting model. To this end, the inclusion of non-stationary tooth engagements during run-in and run-outs are considered, where process dynamics are more prevalent. For this analysis the cutting edge of spherical tools was divided into sections using confocal microscopy, which were replicated as analogous tools using cylindrical end mills. Peripheral milling tests with different process scenarios were conducted with these analogy tools, which had different geometric properties, in order to generate an experimental database. Based on this data, a sensitivity analysis was carried out for process force calibration taking process dynamics into account.