Pocket Decomposition using DN and HARI Number. A Novel Approach

Doctoral Thesis / Dissertation from the year 2016 in the subject Engineering - Mechanical Engineering, grade: Distinction, Sardar Vallabhbhai National Institute of Technology, language: English, abstract: A 2.5D pocket milling is extensively used in aerospace, shipyard, automobile, dies and molds industries. In machining of 2.5D pockets, directional parallel tool-path and contour parallel tool-path are widely used. However, these tool paths significantly limit the machining efficiency. In the present work, an attempt has been made to generate a spiral tool path for machining of 2.5D star-shaped pocket for improving machining efficiency. The spiral tool path is developed using second order elliptic partial differential equation (PDE) and it is free from sharp corners inside the pocket region. Further, the implementation of proposed method is presented on complex non-star-shaped polygon, pocket bounded by free-form curve and pocket with island. The shape of pocket geometry, tool path strategy and various machining parameters (speed, feed rate and depth of cut) affect machining performance. However, the effect of the shape of a pocket geometry and tool path strategy on the performance of pocket machining is scarcely reported. Hence, an attempt has been made to investigate the effect of aspect ratio, feed rate and tool path strategies (zig-zag, spiral and contour parallel) on tool path length, cutting time, percentage utilization of a tool and average surface roughness in machining of AISI 304 stainless steel using design of experiments (DOE). From the findings of above experimental investigation, it was anticipated that there is a need to develop a method (or technique) for comparing different pocket geometry quantitatively and predict the effect of pocket geometry on pocket machining. A novel approach is reported for quantitative comparison of different pocket geometries using a dimensionless number, Divyang Number (DN). The concept and formula of DN are developed a