Tool path generation facilities for 2½-D features in current commercial CAM software suffer, in general, from a number of serious limitations. Improvements in this technology are required in order to reduce machining time and cost.

This thesis describes a method to generate tool paths for milling 2%-D features using a window-frame based approach. This method enhances the current techniques employed for offsetting, covering sharp comers and crossing windows. In this method, the material to be removed in a feature is first divided into layers which are represented by drive profiles. These drive profiles are generated by offsetting the boundary profile. The problems encountered in offsetting procedures, such as negative loops, and small circular arcs, are investigated. The corresponding cutter Centre Location (CL) profile is then generated for each drive profile. Finally, all the CL profiles are unified to give a continuous tool path.

Contributions to existing knowledge have been made in the following areas:​

1. Covering and window-crossing techniques, especially when the stepover is greater than the cutter radius.
2. Consideration of cutter tooth entry/exit conditions during the tool path generation.
3. An algorithm to calculate the medial axis diagram in a polygon which can be adapted to generate Voronoi diagram.
4. Calculation of the actual radial width of cut.
5. Strategies for machining surfaces and complex features.

The proposed method can deal with 2½-D features whose boundaries consist of straight lines and circular arcs. They include (1) Pockets, (2) Surfaces, (3) Semi-open pockets, such as slots, shoulders, and (4) Other complex combinations with islands and existing sub-pockets in the previous features.

Using the proposed method, the slotting distance and the total cutter travel length can be minimized. For any specified stepover1 between cutting passes (even when the stepover is larger than the cutter radius), the cutter machines all the accessible work material to be cut in complex features without lifting the cutter. These advantages should lead to more accurate machined surfaces and to substantial gains in machining time and cost. If necessary, an option is available to effectively control the cutter tooth entry/exit angle so that favourable cutter tooth entry/exit conditions are maintained along most of the travel length by applying special procedures. Hence, cutting geometries that causes tool pre-failurcs can be avoided.

A tool path generation module for pocket machining has been implemented. The actual radial width of cut is calculated, and the effective cutting mode is detected by simulating the machined area. This makes it possible to integrate with a module dealing with cutting conditions, hence the feed rate can be dynamically optimized