Intelligent on-machine measuring robot and assessment methods for internal contour parameters of deep-hole components

The diameter, roundness, and straightness of internal contours significantly dictate the mechanical performance, operational stability, and service life of deep-hole components. Consequently, accurate on-machine measurement during multi-stage manufacturing is essential for optimizing efficiency and ensuring production quality. This paper presents a wheel-driven intelligent robot designed to implement in-situ metrology for deep-hole components with diameters exceeding 60 mm and unrestricted axial lengths. The system features an integrated embedded control architecture and custom that utilizes the Least Squares Method (LSM) for the comprehensive assessment of diameter, roundness and straightness errors. Calibration with an 80 mm ring gauge yielded a diameter Type-A standard uncertainty of u d ≈ 0.003 mm, and combined standard uncertainty of u dc ≈ 0.0052 mm. The ring gauge roundness Type-A standard uncertainty is u fr ≈ 0.0011 mm, and combined standard uncertainty of u frc ≈ 0.0075 mm. For a 2 000 mm deep hole of 80 mm diameter, the mean straightness error is f s ≈ 0.501 mm, with expanded uncertainty of 0.035 mm at 95 % confidence. The results indicate that the proposed measuring robot provides a versatile and precise solution for the on-machine measurement of diverse deep-hole specifications, effectively eliminating the constraints imposed by extreme hole lengths.