Automatic inspection of turbine blades using a 3-axis CMM together with a 2-axis dividing head

Turbine blades are widely used in turbo-engines and generators. The complex geometry of turbine blades and the limited space between two adjacent blades cause difficulties in both machining and inspection. This paper is focused on the use of a 3-axis coordinate measurement machine (CMM), together with a dividing head with two rotational axes, to undertake the task of precision inspection of turbine blades that surround the periphery of an axial wheel. Based on the geometrical relationship between the probe stylus and the turbine blades, a methodology is proposed to find the angle of rotation of the axial wheel when a collision is likely to occur between them. Other issues related to system implementation are also discussed in this paper, including: (1) Data transformation from the turbine blade's geometric model to the CMM control codes, (2) Planning of the traveling paths of the stylus, and (3) Analysis of the measured data.