NURBS Surface NC Machining Tool Path Auto-generation Technique Research Based On The Iso-scallop Method

At present,in the field of complex surface processing of NC,CAM softwares that used for the actual production in most of our manufacturing enterprises is introduced from abroad, they are expensive, users must be specified cutting tools, boundary and parameters, the system calculate tool path based on user's input, so it lacks flexibility in the specified tool location and distribution of tool path, and generally has to try many times to be successful. For the tool path of non-ball-end cutters that have no over-cutting intervention, especially the five-axis, it lacks support of commercial systems. The greatest weakness in the NC programming by commercial CAM system is the human intervention redundantly and lack of flexibility and adaptability in the calculation of cutting lines pacing, step and the tool axis direction. NC processing is one of the important links in the CAD / CAM technology, and planning of tool path is the key of NC processing technology. In NUBRS surface processing of NC, the pros and cons of tool path generation algorithm affect the final surface quality and processing efficiency to some extent. This paper studies aspects of optimization of tool path in NUBRS surface processing of five-axis NC and automatic generate on the basis of referencing relevant literature.In the optimization of tool path in NUBRS surface processing of five-axis NC: on the basis of the analysis of five-axis NC processing features and principles, we propose a computational method based on the spiral tool path of constant scallop height in view of prone problems such as machining vibration in NC processing. Using this method can discrete the boundary surface into cutter contacts firstly based on the maximum tolerance, then generate ring trajectory with the same high level of residual following the maximum allowable scallop height, at last, construct constant scallop height tool path line to achieve continuous cutting, which is the adjacent path connected with diagonal curve. This paper describes the calculation of step size and line spacing on the basis of tool path generation method of constant scallop height in detail; Using the nature of law cut-off line in differential geometry, we put forward an algorithm to determine the local surface shape rapidly based on constant scallop height, it optimizes the direction of tool cutting and simplifies the calculation; when determine the course of tool axis vector, it takes the impact of processing tolerance into consideration, reduces the deviation since the surface characteristics of a knife contact instead of that at the point in the neighborhood.In the development of automatic tool path generation module: UG/Open Application Programming Interface can build the connection with the application programming of original UG software, realize seamless integration between development of new features and original features. This paper applies the second development tools of UG such as UG/Open API,UG/Open Menu Script,UG/Open UIStyler, which is the basic platform of universal computer-aided design system, we can embed in our computation algorithm of tool path, develop the UG-specific interface, it includes a special pull-down menus, toolbars, dialog boxes and related information prompt window, so that develops the required functions.In the experimental validation: this paper gives a specific surface model, carries on the processing simulation using traditional constant scallop height algorithm and the one this paper raises by defining the type tool and machining tolerance, the results of experiment carry on the contrastive analysis from the processing efficiency, processing quality, the machining process that can bring vibration of the machining. Experiments show that the proposed algorithm of tool path is feasible, and the algorithm based on the UG platform calculates fast, it is easy to operate and control accurately.