Research On Automatic Coloring Technology For Deformed Areas On Metal Surfaces

With the rapid advancement of the economy,metal products like badges,logos,tags,and other crafts are gaining increasing popularity among consumers,which providing a huge market for the domestic related industries,especially the decoration industry.To achieve diverse colors on the surface of such products,the conventional method involves using injection equipment to pour a specific quantity of PU material or UV ink into the grooves of the target area,so as to achieve color diversification of the metal surface.As the demand for personalized metal badges,logos,and other products continues to grow,there is an urgent need to develop a feeding equipment system capable of automating the coloring process on metal surfaces.This advancement will not only enhance processing efficiency but also enable mass production and processing of high-quality products.Ultimately,meeting the demands of the market is the primary objective.Therefore,this paper focuses on small metal badges as the research subject and incorporates machine vision technology to achieve accurate image positioning.Subsequently,the contours and characteristic points of irregular-shaped regions are extracted,and a parametric model of the region’s contours is established using NURBS curves.Finally,the coloring trajectory planning for different regions is accomplished based on regional classification standards.First,a summary of the development history and research status of surface contour extraction and trajectory generation is provided.Subsequently,the research status of metal surface coloring devices is presented,both domestically and internationally,highlighting the limitations of the current injection-based metal surface coloring technology.Finally,the research objectives of this paper are outlined,followed by a concise summary of the main research content.To address the issue of inaccurate filling points during the coloring process,an intelligent metal surface coloring device visual platform is built,and the selection of camera,lens,light source and lighting mode is given to ensure that the visual system could maintain a good image acquisition ability.Then,the Zhang Zhengyou calibration method is employed to refine the calibration grid to realize the transformation from the world coordinate system to the pixel coordinate system,ensuring precise positioning accuracy of the feeding points within a tolerance of below 0.02 mm.To enhance the efficiency of subsequent parametric modeling,the acquired images are preprocessed first,the effects of different processing methods are compared.The weighted average grayscale and median filtering methods are selected to reduce the noise in the images and strengthen the feature region.Secondly,the Canny operator is improved and adjusted to the optimal threshold ratio of 19:245 to obtain a clear edge contour image.After the clear edge contour image is obtained,the automatic generation of coloring trajectory is studied.With the help of SIFT operator,the contour curve feature points are extracted,the NURBS curve is used to combine the feature point data information to complete the parametric modeling of edge contours.Taking into account the presence of "islands" within the regions,an automatic path generation scheme is proposed for different shaped regions.This scheme ensures appropriate trajectory generation based on the presence or absence of such islands.Finally,modeling and simulation experiments are conducted to ensure that the proposed algorithm could ensure the uniform and quantitative distribution of the injection points in the interior of the target area,which verifies the feasibility and effectiveness of the algorithm.Online coloring equipment often has only one injection head,which cannot realize the multi-color injection process,and molded products such as badges and LOGOS are developing in the direction of multi-color multi-layer personalization.To solve this problem,a four-color jet machine and a four-color parallel nozzle group device and system are developed to realize the multi-color injection process.At the end of this paper,the proposed automatic coloring trajectory generation algorithm is experimentally verified by using the automatic metal surface coloring device.The results demonstrate that the algorithm effectively achieves uniform and quantitative coloring of irregular areas on the metal surface,and there are no problems such as pigment spillage,crosstalk,bubbles and white space on the surface of the target area,which improves the efficiency of trajectory generation and processing while meeting the expected outcome.