Study On The Flatness Measurement Of Large Precision Parts Using Laser Tracker

With the fast development of the modern manufacture, the photoelectric, machinery, energy,shipping and the other industry’s demand for the large size and high precision rotary axialproducts are increasing, and requirements for the flatness of these large size and high precisionthrust parts are also increasing. The conventional flatness measurement technologies, such as thepointer method, table bridge method, and stride instrument and so on, have already failed to meetour requirements. Their accuracy is not enough, and they cannot achieve the in sitemeasurements. Laser tracker appeared in the1990s as a three-dimensional measuring instrumentfor large dimensions is widely used in the industrial measuring system, which is famous for itshigh precision, high efficiency, in site measurement, real-time dynamic tracking measurementand easy to be moved or installed etc. Therefore, this paper proposes a method of measuring theflatness of large size and high precision machinery parts based on laser tracker. The majorresearch content is included in the following:1. The structure and working principle of laser tracker system are investigated, the errorsources of laser tracker, which affects the accuracy of distance and angle measurement, areanalyzed. On the basis, theoretical analysis on the single-station measurement uncertainty iscarried out, it is calculated that the single-station measurement form is not suitable for themeasurement accuracy0.03mm（±0.015mm） of Φ5000mm thrust parts based on the analysis ofexperiments. Therefore, a new measurement form based on the station-moving measurementprinciple of laser tracker is proposed.2. The principle of the station-moving measurement is introduced; the mathematical modeland algorithm model of the station-moving measurement are built. According to thecharacteristics of laser tracker, a method, which is used to determine the initial value, isprovided.3. The arrangement of the station-moving measurement is analyzed. The effects of thenumber of mobile station, the different layout of base stations and the altitude difference betweenstations on the flatness measurement are analyzed through simulation, and measurementuncertainty is analyzed through Monte-Carlo principle,4. According to the station-moving measurement principle, experiment of the flatnessmeasurement of a Φ5000mm round table is carried out, the result is compared with bridge-level,and feasibility of measuring flatness of large precision parts is validated by experiments andanalysis results.