Using Clothoidal Spirals to Generate Smooth Tool Paths for High Speed Machining

Pamali, Abhinand P. Using Clothoidal Spirals to Generate Smooth Tool Paths For High Speed Machining. (Under the direction of Dr. Yuan-Shin Lee.) We present a new and innovative method to generate Contour Parallel tool paths using Clothoidal spirals for 2.5D pocket milling. The tool paths generated by the proposed method are more suitable for High Speed Machining compared to the traditional tool paths. Mechanical parts, such as those in Aerospace industry, Mold and Dies industry, etc require large volumes of milling operations. Modern High Speed CNC Machines are used in making of these parts. Although the High Speed CNC machines can provide very high spindle speed, due to various reasons, it has not been possible to use their High speed capabilities to their full extent. Two of the main reasons being, complex pocket geometry and complex tool path geometry. Most pockets are made up of sharp corners. In the traditional contour parallel pocket milling tool paths, as the cutting tool approaches these corners, they have to undergo a sudden change in directions and the acceleration of the tool has to be instantaneously decreased. Also, there is an instantaneous increase in the chip volume and the resultant forces acting on the cutting tool. In our proposed method we smooth these sharp corners of the traditional tool path by using Clothoidal spirals. The Clothoidal curves which have traditionally been used for Highways and Rail track design, have an unique property, according to which, the curvature of the Clothoidal spirals varies linearly with the length of the curve. By using these curves of uniformly varying curvature, we reduce the magnitude of the sudden direction changes that the cutting tool has to undergo at the sharp pocket corners. The cutting tool is subjected to lesser resultant forces and has a comparatively uniform acceleration. Machining time is also expected to be reduced by our proposed method. USING CLOTHOIDAL SPIRALS TO GENERATE SMOOTH TOOL PATHS FOR HIGH SPEED MACHINING By Abhinand P Pamali A thesis submitted to the Graduate Faculty of North Carolina State University in partial fulfillment of the requirements for the Degree of Master of Science Industrial Engineering