An Automated 3-D Shape Measurement Method for Turbine Blade Using a 6-Axis Robot

High-accuracy 3-D shape measurement of turbine blade is important for manufacturing engine and aircraft's safety. At present, the most commonly used three-coordinate measuring machine in the industrial field may cause scratches on the surface of turbine blade. Optical 3-D measurement methods, such as fringe projection profilometry, are unable to carry out targeted measurement of geometric structures with different levels of precision. This paper presents an automatic measurement method based on pneumatic gripper and 6-axis robot. The proposed composite system includes global sensor with large scanning range and local sensor with high accuracy, which can perform 3-D reconstruction with specific resolution for different positions of turbine blade. We use a 6-axis robot and pneumatic gripper to grasp the turbine blade automatically. The 3-D scanning is completed according to the viewpoints planned in advance. The point cloud data of different angles are aligned to obtain a high precision 3-D model of turbine blade surface. The experimental results show that the proposed automatic scanning method can effectively avoid the measurement error caused by manual grasping operation. On the basis of complete 3-D measurement of the whole surface, more dense point cloud data are obtained for fine structures such as blade edge. Our result is of great significance to the field of industrial measurement.