On-Machine Metrology for Hybrid Machining

In this chapter the concept of surface metrology is introduced and the optical methods for on-machine metrology(OMM) and machine tool calibrations are discussed. Then we focus on a single-point optical method, namely dispersed reference interferometry (DRI) for OMM as a case study. The work principle and hardware design of the DRI system are introduced. Due to the relatively harsh environment in the machine tools, the metrology characteristics of surface measuring instruments would deviate from those tested in laboratories. In order to improve the performance of OMM systems, it is necessary to calibrate the OMM system and compensate the systematic errors. Three major error sources, including on-machine vibration, machine tool kinematic errors, and linearity errors are investigated. Static and scanning vibration tests are performed in order to select the proper sampling frequency. Machine scanning error is mapped for OMM correction with the proposed kinematic error modeling measurement and compensation method. Calibration of the response curve and linearity error correction are conducted by measuring a radially distributed step height sample on the machine. Experimental investigation is conducted which proves the validity of the proposed calibration methodology and the effectiveness of OMM