تاثیر استراتژی تولید در تولید الگوها و قالب ها

The manufacturing of molds and dies has become more prominent as the world economy advances toward reduced lots, larger diversity of products and more importantly, reduced time for launching new products. Such requirements increased the application of new technologies – on one side looking to improve the digital integration of the process chain CAD/CAM/CNC and on the other side the introduction of the HSC technology in this process chain. However, the introduction of these technologies requires also the gathering of the necessary know-how related to the whole process, for example the application of appropriate cutting strategies, which have a direct effect on the geometrical precision, surface roughness and surface texture of the final part. This paper presents a experimental work about the relation between cutting strategies and the machining time and surface quality of the part. For that was developed a test model representing surfaces found in mold and dies; the material of the part was P20, a typical material for this application. Cutting strategies like Follow Periphery, Follow Part, Parallel Lines and Zig-Zag, were applied in the NC machining of test model and the results considering time and surface quality were compared.

Increasing demands for industrial designs which provide more harmonic ways of presenting a product, the development of methods and software for modeling and manipulation of complex surfaces as well as the reduction of hardware costs has intensified the use of CAD/CAM Technology in product development [1]. For this reason, the manufacturing of molds and dies has become more prominent as the world economy advances toward reduced lots, larger diversity of products and more importantly, reduced time for launching new products. However, these technological applications have encountered great difficulties in industry since new factors have emerged as variables in the manufacturing process [2]. Within these variables, the manufacturing strategy is importance for determining the tool path, and therefore responsible for lead time, geometric precision, and surface finishing, which make up the product characteristics for subsequent stages. Within the CAD/CAM/CNC Technology, product manufacturing is carried out through the creation of a geometric model in the CAD system which is transferred to the CAM system. There the programmer will provide the manufacturing data which will result in the tool paths. After the generation of the tool path, an internal post-processor of the CAM system creates a NC Program based on all of the tool paths, which is interpreted by the CNC of the tool machine as movements [3].

This study provided additional knowledge and a clearer understanding of the influence that the cutting strategies have in relation to the geometry being manufactured. These influences can be observed in the lead time, surface finishing and CAM programming time. During the CAM programming of the test model, the programming time for the Zig–Zag 45° strategy was more rapid compared to the application of the different strategy set. This result is due to the fact that the Zig–Zag strategy needs only to select one geometric type while the set of strategies needs to select diverse geometric types, as well as configure the parameters for each one. These results verify that the selection of geometries is a dependent factor of the CAM programming time due to the longer time it takes to select each geometry. In relation to lead time, the increase in finishing operations for Test Model 2 was due to the increase in detail associated with the geometry and resulted in a longer lead time when compared to Test Model 1. In relation to the surface finishing, regions represented by geometries with a high inclination angle in Test Model 1 did not present good surface quality when the tool path followed the lateral direction of the inclined geometry. However, when the tool path followed the frontal direction of the inclined geometry, good surface quality resulted due to the influence of the uniformity of the tool path. Finally, the surface quality of the test models verifies the large difference in final finishing quality. Test Model 2 obtained more satisfactory results compared with Test Model 1 due to the selection of strategies that better adapt to the geometry. Test Model 1 obtained a facetted finishing due to the direction of the tool path which was considered unsatisfactory. Due to the low variation of superficial roughness obtained, we can conclude that the influence of the strategies is perceptible only in the CAM programming time, the lead time and surface finishing. For these factors, a tangible difference was observed between the test models. Acknowledgements This study was developed with the support of ProBrAl Project–Optimization of the Productive Chain with the Utilization of High Speed Cutting (HSC Technology) and of Form Features Technology with the support of Millenium Factory Institute (IFM) and with the support of the Support Program for Scientific Advancement of Professors (FAPIC/UNIMEP and PIBIC/CNPq).