INTERACTIVE SIMULATION OF ROBOT MILLING FOR RAPID SHAPE PROTOTYPING

Rapid shape prototyping has become a prominent method to speed up the product development process in industry. Automatic robot milling, directly from CAD data, is an efficient technique to materialize the intended product shape quickly. There are a number of situations in which previewing of this process is required. The end-user, i.e., the designer who intends to order a prototype, wishes to be informed about the quality of the result in terms of geometric appearance and accuracy, for example, by comparing it to the CAD model. Also, any systematic defects inherent in the prototyping process must be made visible. Furthermore, the developers of the prototyping system can take advantage of simulation in their efforts to improve the process. The major technical problem in simulating the milling process is to model the volume removal operations efficiently, so that the stock-in-progress can be visualized at any moment. This article presents a method to perform such simulation while meeting stringent requirements, including the ability to handle the large number of robot movements in a single milling process (up to 10(6), depending on the required spatial accuracy), high speed, and user-interactivity. Both the block of material that is being machined and the milling tool are internally represented by a 3D voxel structure to achieve real-time volume-removal operations on the material. All other objects, such as the robot and the work cell, keep their original B-spline surface representation, to enable high-quality visualization. Implementation of the data structures and algorithms described here has resulted in a useful system for joint simulation of volume removal and robot motion.