Abstract: Orthopedic emergency treatment is highly sensitive to the manufacturing time of braces.3D printing technology provides favorable conditions for rapid manufacturing of personalized braces.Due to the curved tube shape of the elbow support having a large number of suspended structures relative to the printing platform,the supported printing greatly affects the forming efficiency. The five-axis unsupported 3D printing process with rotating bottom plate provides an effective solution for efficient printing. However,the position and pose of the irregular elbow model after field 3D scanning should be adapted to the printing mechanism to print smoothly.In order to solve the optimal pose adaptation problem of elbow model,an automatic pose adjustment method based on 3D elbow model features and printing equipment structure constraints was proposed. Aiming at the irregularity of the 3D scanning model,the spatial pose characteristics of the model were obtained by extracting the center line of the elbow model,calculating the angle between the three axes,and identifying the long and short axes. In view of the limitation of the rotation angle of the bottom plate of the printing equipment and the coordinate position of the growth point of the bottom model,the multi-angle pose of the elbow model was optimized and adjusted,such as the parallel bottom surface,the spatial orientation and the close bottom plate,so as to meet the requirements of 3D printing. The effectiveness of the pose adjustment algorithm for the raised elbow model was verified through simulation comparative analysis and printing experiments,providing support for the slice processing of unsupported fast 3D printing.

Key words: 3D printing, 3D scanning, the extraction of centerline, position adjustment, feature matching