Research On Mechanism And Assessment System Of Accurate Color Reproduction In Color 3D Printing

3D printing,as a digital new technology for manufacturing and replicating color 3D geometric objects,is becoming more and more popular in personalized and functional fabrication applications.According to different demands of product customization,3D printing can be divided into functional 3D printing and color 3D printing,and the former is much concerned by the public because it matches closely with national strategies.In recent years,color 3D printing has been growing in livelihood applications,especially in cultural creativity,sci-tech education,fashion art,brand 3D marketing and foodservice,which require accurate color reproduction.However,due to the challenges of color reproduction accuracy,these color3 D printing applications have not yet reached a large-scale market globally.The bottleneck in achieving accurate color reproduction is the lack of a unified theory and standard models,which in turn restricts the industrialization of faithful fabrication based on color 3D printing.This dissertation is a systematic study of the applied and scientific issues involved in the key accuracy challenges of rendering,coloring,and acquisition for accurate color reproduction in color 3D printing,from the perspective of color transmission flow in color 3D printing.The main aim is to understand and improve the mechanism description,theoretical model,and color evaluation system for the accurate color 3D printing.The core work and innovations of this dissertation mainly include the following five aspects.Chapter 1 In the introductory section,the process features,application characteristics,color reproduction methods,color reproduction quality evaluation and prediction models are clearly elaborated in the domestic and international research related to color 3D printing.Moreover,the generic challenges for accurate color reproduction and evaluation of color 3D printing are summarized to propose the key research contents and the framework of this study.Chapter 2 To deeply understand mechanisms related to surface properties,color rendering principles,color efficiency evaluation and calculation strategies of color 3D printed substrates,experimental tests,quantitative characterization,and microscopic feature analysis of color rendering efficiency of paper-,plastic-,and powder-based color 3D printing substrates are conducted to develop a new substrate color rendering efficiency metric and numerical model.The proposed macro-micro and subjective-objective binary assessment systems can provide the core theoretical basis for the accurate color reproduction control of color 3D printing.Chapter 3 To address the coloring challenge of accurate color 3D printing,the key factors such as the slicing strategy,coloring method,and printing sequence of each sliced layer are analyzed,and a boundary coloring theory oriented to color control of the color sliced layer is proposed.Given the Mimaki UJF-6042 and Stratasys J750 3D printers,the color reproduction performances of unique 3D benchmark models with primary colors and gradient colors,as well as hemisphere shell models with same primary colors are analyzed and correlated to confirm the proposed theory in a limited scope.Next,the proposed equation for defining the boundary coloring width of each color layer can provide computational feedback for the color 3D printing system to actively adjust the boundary coloring width of the following color slices.Chapter 4 To precisely match the optical properties of coloring materials and filling materials in each sliced layer,the longitudinal hierarchical structure inferred by the microscopic imaging features of each patch side(cross-section)with a primary color on the special benchmark model of paper-,plastic-,and powder-based color 3D printing is analyzed.Thus,the mechanism cognition at the aspect of optical properties such as optical medium and optical transmission path is classified for each substrate color 3D printing.The research framework of the boundary coloring width model based on optical parameters is constructed accordingly,which provides a solid theoretical support and expansion direction for the development of a universal boundary coloring theory system.Chapter 5 Based on the study of color rendering efficiency evaluation in Chapter 2,the color 3D benchmark model is used as test samples,and the interface design and operation codes of eight functional analysis modules were implemented by the MATLAB GUI to develop a color reproduction quality evaluation system for color 3D printing.This evaluation system provides a friendly interface interaction while maintaining high efficiency in the evaluation of each color reproduction quality index,and serves as the theoretical basis and technical reserve for the development of color 3D printing digital flow and color management system.