Research On Key Technologies Of Numerical Control Engraving Machining

In recent years, along with the raising of living standards, the demands for aesthetic engraving products have been continuously increasing. But the traditional manual engraving method is inefficient and far from meeting the huge market reqiurements. For this reason, numerical control ( NC ) engraving machining method has been adopted to improve the productivity of engraving industry. However, because of the special characteristics of engraving products, directly applying existing NC machining strategies to NC machining of engraving products is not feasible. This dissertation makes further researches on the key technologies of NC engraving machining to pursue comprehensive solution to digitized manufacture of engraving products. The main contents and achievements are as follows:Based on improved sweep-line intersection method, an algorithm is put forward on automated recognition of complex regions from planar profiles composed of arc and straight segments. For invalid input, the exact positions where intersections occur can be detected so that it is convenient for the user to eliminate any defect in profiles. For valid input, by quickly built spatial relationship between profiles, the regions can be recognized with approximately linear time consumption. The algorithm is also suitable for the recognition of multi-nest regions.An contour-parallel tool path planning algorithm and a smooth spiral tool path generation algorithm are put forward for area milling. The former can efficiently create uncut-free tool path without tool retractions, which is applicable to milling of arbitrary shaped machining area with multiple holes. The latter can generate Cn continuous tool path with no sharp turning corners via B-spline curve fitting, which is suitable for high speed engraving with small cutting tools.A tool path scheduling methodology for 3D engrave models is presented, which performs rough machining by z-level milling first, then finish machining corner uncut material with pencil tracing. Calculation of rough machining tool path is greatly simplified using equivalence relation between curves offset from engraved pocket boundary and the intersection curve of horizontal plane and engraved pocket. Generation of pencil cleanup tool path is simplified to medial axis travel problem using equivalence relation between edges of engraved pocket and medial axis of machining region. A simple medial axis traveling strategy is also presented.A new tool path generation algorithm is presented to eliminate interferences when nesting convex mold and concave die which are machined with tool paths calculated by offsetting the 2D profile directly. With this algorithm, after only three times of profile offsetting, both tool paths for machining convex mold and concave die can be calculated simultaneously. When convex mold and concave die which have been manufactured by this algorithm are assembled together, there are absolutely no interference, and the fit clearance is of uniform distribution.By means of introducing new conception including relief surface definition, relief surface blending, art-gray-photo modeling, image edge detection et al, an approach for 3D relief modeling is presented. Based on geometry-relief and photo-relief mixture modeling, the approach can be applied to generate artistic relief with complex surfaces. Using inverse tool offset and projection method, the generation of interference-free tool path for relief finish machining is achieved, which is particularly suitable for relief machining with small tools and is extendable to arbitrary shaped engraving tools.Based on the methods and algorithms proposed above, an NC engraving software has been developed. Practical examples show the validity and effectiveness of the system.