A general mechanics and dynamics model for helical end mills

Presented in the paper is a new approach to 3-axis NC tool-path generation for sculptured surface machining. In the proposed C-space approach, the geometric data describing the design-surface and stock-surface are transformed into C-space elements, and then, all the tool-path generation decisions are made in the configuration space (C-space). The C-space approach provides a number of distinctive features suitable for high speed machining of dies and moulds, including: (1) gouge-free and collision-free tool-paths; (2) balanced cutting-loads; (3) smooth cutter movements; and (4) verification mechanisms. It is suggested, with some supportive results, that the Z-map model might be a suitable representation scheme for implementing the C-space method. Also discussed are other implementation as well as future research directions.

C-space approach to tool-path generation for die and mould machining

CAD/CAM systems offer various possibilities for finishing milling of parts such as dies and moulds, turbine blades and other high quality components, but most of them do not take into account the surface topomorphy expected, which is significantly affected, among others, by the milling kinematics and the contact conditions between the tool and the workpiece. In order to predict the workpiece roughness in multiaxis finishing milling with ball end tools, the computer supported milling simulation algorithm ‘ ballmill ’ was developed. By means of this algorithm, considering the individual movements of the cutting tool and of the workpiece due to the milling kinematics, the undeformed chip geometry, the cutting force components, the tool deflections and the final surface topomorphy expected are determined. Numerous investigations concerning the parameters mentioned above, with various workpiece materials have been carried out in order to determine the correlation of the experimental results with the corresponding calculated ones with the aid of the ballmill algorithm. Moreover the algorithm validity was extensively evaluated in milling of free form surfaces of large hydroturbine blades. The convergence between the experimental and the related calculated surface topomorphies by means of the ballmill computer program was found out to be satisfactory. Thus, the prediction of appropriate cutting conditions and milling kinematics to fulfill surface topomorphy requirements was enabled.

Determination of the chip geometry, cutting force and roughness in free form surfaces finishing milling, with ball end tools

High-Speed Milling of Dies and Molds in Their Hardened State

This chapter provides an introduction to sculptured surface machining (SSM) process, including the unit machining operation (UMO), and identifies the geometric issues that occur in the information processing stages of SSM, such as interference handling, cutter location (CL)-surface construction for the C-space approach, 2D point sequence (PS)-curve offsetting, area scan algorithms, PS-curve fairing, and collision detection algorithms. Many products are designed with sculptured surfaces to enhance their aesthetic appeal, especially in the automotive and consumer-electronics industries. Other products have sculptured shapes to meet functional requirements, such as aerodynamic, optical, medical, structural, and manufacturing. While these aesthetic and functional surfaces are created using computer-aided geometric design (CAGD) techniques, it is the role of SSM to realize them in physical form. The chapter presents the examples of various SSM processes. It classifies SSM process models into two types: sequential models and hierarchical models. The purpose of an SSM process is to produce a sculptured part by applying a series of metal-removal processes to a workpiece.

St. Hock

Papers

High-speed milling of dies and moulds - cutting conditions and technology