This book focuses on 3D printing and molding/ copying technologies and approaches, which innovatively proposes the concept of polymer 3D copying technology. It introduces the two technologies of polymer 3D printing and 3D copying by analogy and elaborates the core principles and processes of polymer 3D copying technology, the composition, basic parameters and structure design of polymer 3D copying machines, precision control methods, defect generation mechanism and solutions of polymer 3D copying products, and also discussed the future development of polymer 3D copying technology. The novel concept of 3D copying is one of the major features of the book, which is particularly suited for readers who are interested in rapid prototyping and molding. The book is based on both traditional and new knowledges, with novel content and concept, focusing on both principles and engineering practice. It systematically reflects the content and application of polymer 3D printing and 3D copying technology, which can benefit researchers, engineers, and students of related majors engaged in the fields of polymer processing, rapid prototyping, 3D printing and molding/ copying, etc.