Computer graphics presentation of drilling operations.

Abstract

The motivation of this study is to apply computer graphics technology to drilling animation. The underlying knowledge-base is the proposed cutting model and the drill geometric model. The dissertation includes four parts: (1) a new oblique cutting mechanics model, (2) a new drill flute geometric model, (3) a systematic method to predict the upper limit of the feed rate, and (4) computer animation software for drilling. An oblique cutting model is proposed involving both the chip curl and the built-up edge for the first time. A metal stagnation principle is postulated. The model is capable of predicting the chip formation including the chip thickness, the chip curl radius and the flow angle. The numerical results agree reasonably well with the available experimental data. A new flute geometry model is proposed using a polynomial function. The model reveals the main cutting edge of a drill is a curve instead of a straight line as previous researchers commonly assumed. Temperature distributions and subsequently thermal stress distributions in a drill are computed using the finite element method. The drill geometric models are used for mesh generation and the cutting mechanics model for boundary conditions. Combining a failure criterion (von Mises criterion) with the thermal stress distribution leads to predictions of the upper limit of the drilling feed rate. The computational results are in good agreement with the reference data. Based on the above cutting mechanics model and the geometric models (both point and flute) of a drill, a menu-driven computer graphics package is presented to animate drilling operations, simulate drill grinding processes, and evaluate drill performance. Visualization on a graphics terminal, a principal element of CAD integration, presents the drilling animation results in a form that is easily interpreted.