| Author | Tran Duc Tang |
| Call Number | AIT Diss. no.ISE-07-04 |
| Subject(s) | Machine-tools--Numerical control
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| Note | A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Engineering in Design and Manufacturing Engineering, School of Engineering and Technology |
| Publisher | Asian Institute of Technology |
| Series Statement | Dissertation ; no. ISE-07-04 |
| Abstract | Five-axis CNC machine tools have been more popular in machining area because of their ability to machine parts with complex geometries efficiently and achieve higher dimensional accuracy. Since two additional rotational axes are introduced in five-axis CNC machines, five-axis NC machining offers many advantages over three-axis machining, such as better tool accessibility, faster material removal rates, reduced machining time and improved surface finish. However, because of the two additional degrees of freedom, collisions are prone to occur in five-axis NC machining. This dissertation introduces a new algorithm based on the sweep plane approach for collision detection and avoidance for five-axis NC machining. The proposed algorithm takes into account not only collisions between the tool and workpiece, but also collisions between the other parts of the CNC machine. The change of the workpiece geometry during machining is included in the detection process. In this algorithm, the workpiece and machine bodies are firstly approximated by an octree of bounding spheres. The collision is checked between these spheres. If there is any interference between these bounding spheres, their sub-spheres are further tested. The subdivision process is recursively performed until the accuracy reaches the desired level. If there is no interference between the spheres, there is no need to subdivide any more. When the interference is detected between the spheres at the lowest octree level, the slices within these colliding spheres are further checked by using the sweep plane algorithm to determine whether the enclosed objects really collide with each other. In the sweep plane algorithm, most of the slices of the moving bodies stay parallel and their collisions are detected by checking the interference between these parallel slices using 2D polygon clipping. If the slices are not parallel to the reference slicing direction (due to the rotary axes), the interference detection examines overlaps of the projections of these slices on the three perpendicular planes XY, YZ, and ZX. In case that the collisions are detected, the biggest collision boxes are stored. Based on the collision data, a new collision correction strategy is proposed, where the biggest collision gets highest priority for correction. By this strategy, when the biggest collision is corrected the other collisions mostly will automatically disappear. Therefore, time complexity for collision avoidance algorithm will be considerably reduced. With the use of the proposed sweep plane approach, the accuracy of the algorithm can be adjusted to meet the required accuracy by changing the distance between the sweep planes. Furthermore, the proposed algorithm can be customized for a wide range of applications in three, or four, or five-axis machines as well as in other computer graphics applications. |
| Year | 2007 |
| Corresponding Series Added Entry | Asian Institute of Technology. Dissertation ; no. ISE-07-04 |
| Type | Dissertation |
| School | School of Engineering and Technology (SET) |
| Department | Department of Industrial Systems Engineering (DISE) |
| Academic Program/FoS | Industrial Systems Engineering (ISE) |
| Chairperson(s) | Bohez, Erik L. J.; |
| Examination Committee(s) | Pisut Koomsap;Guha, Sumanta;Lauwers, Bert; |
| Scholarship Donor(s) | Ministry of Education and Training, Vietnam; |
| Degree | Thesis (Ph.D.) - Asian Institute of Technology, 2007 |