A novel type compact five-coordinate measuring machine with laser and CCD compound probe

In this paper, a novel type compact five-coordinate measuring machine with laser and CCD compound probe, which consists of three translational axes and two rotational axes, was designed and built. The compound probe is employed and the measurement mathematical model is established. An improved genetic algorithm is applied to solve the unknown parameters of the model. Hence, by means of this model, the 3D surface data of the tested object can be transformed into the same reference coordinate system. Quasi-Newton method is introduced and in charge of processing tested surface data. Based on the variety of tested object, such as plane, sphere, cylinder etc. the corresponding optimization objective function and initial condition are set properly to achieve the solution of characteristic parameters. Especially, in this work, an evaluation function method based on the “roundness” information of the through-hole image is proposed to detect the diameter and spatial location of hole, which particularly fits for inspecting those thin and small through-holes drilled at the soft and easy-deformed objects. Consequently, the measurement puzzle of spatial angle between two thin and through-holes is easily solved. The experiments show that the measurement repeatability of this machine is within 1.6 μm. Meanwhile, the experiments illustrate the validity and feasibility for through-holes measurement.

► A novel type compact five-coordinate measuring machine is designed and built. ► The laser and CCD compound probe is adopted in this machine. ► The system measurement model is established and the system parameters are calibrated by the genetic algorithm. ► A new method of detecting tiny and soft through-holes is discussed in this work.