Model Based Cutter Analysis and Evaluation in Milling Titanium Alloys.

Abstract

In developing a high performance titanium milling process current industry practice uses experimental approach. However, trial-and-error tests are time-consuming and have become increasingly costly due to rising material costs. In this study, several models addressing the important parameters in the titanium milling processes are developed for the evaluation of tool performance. First, a cutting force model has been developed. The model considers varying rake and clearance angles along the flutes and uses a universal uncut chip thickness calculation for arbitrary cutter geometry. Moreover, the force of worn milling tool is also modeled in the study. The forces of sharp and worn tools are both validated by experiments. The second topic includes a temperature model and a temperature measurement technique for milling process. The model considers the varying heat flux and heat input area. The coolant and flank wear effects are also included in the model. Finally, a tool-foil thermocouple technique has been designed to measure temperature in milling process and the measurement results are used for model validation. An integrated model for estimating tool wear progression is proposed based on existing models. The model uses iterations between tool wear and force, so that the increase in wear with cutting time is able to be estimated from the CAD model of the tool. Tool wear is measured in the experiments to validate the wear progression in the model. Moreover, by setting a criterion of flank wear, the tool life can be predicted. Tool lives under several cutting conditions are calculated and compared with experimental results. Finally, an analytical model for calculating the stress in the tool is developed. The wedge-shaped tool is divided into two loading systems, and a boundary element method is used for solving the loading problems. Brittle fracture analysis is used to evaluate the stress level along the milling tool edge. The chipping region on a milling tool design is identified from the stress analysis with the use of the CAD model of that tool design.