Universal approach for simulation and analysis of cutting edge engagement in orbital drilling processes

Abstract

During the last decade a special drilling method called orbital drilling (OD) was investigated in many directions. The process is described by a complex geometric machining setting due to the three dimensional tool path and the superimposed rotary cutting motion. Comparing to standard mill or drill operations this motion causes highly changing conditions regarding the chip formation for each cutting edge of the tool and forms a complex shape of the bore bottom. For primitive tool geometries and certain process specifications, several analytical approaches to calculate the geometrical cutting conditions were published. However, it is still difficult to calculate or visualize the cutting conditions for each cutting edge in an arbitrary OD-operation and especially for free formed tool geometries. As a matter of fact the understanding of the details of OD is still limited. The objective of this study is to derive a more universal approach for the geometrical description of the uncut chip thickness in OD-processes. The approach is realised in a prototype of a simulation software (SSW) that calculates a virtual material removal by a numerical algorithm based on a workpiece representation consisting of so called Dexel elements combined with a residuum strategy. In contrast to many common tool engagement simulations, this paper presents a method that is focussed on a calculation of the engagement condition for each cutting edge of the tool. By means of this method it is possible to simulate and visualize a virtually arbitrary OD-process. To proof the accuracy of the simulation a comparison to an analytical model for a standard tool type was carried out. Furthermore the SSW was applied for an analysis of a concave front cutting profile of an OD-tool. Due to this application a mathematical description for a full front cut could be derived.