Study On Ultra-precision Cylindricity Error Measurement Method

Cylindrical parts are both the basic components of all kinds of machinery equipments and the essential elements making up several rotary motion pairs. The shape errors of cylindrical parts have great influences on fit precision and quality, having great significance on controlling the vibration noise of the rotary motion and the rotational between the rotary motion pairs and sealing effect. Cylindricity error is a comprehensive evaluation index used to evaluate the shape precision of cylindrical parts. It reflects the variation between the measured cylinder elements and the ideal cylinder. The measuring method of cylindricity error is simple, practical, economical with high precision and high-efficiency. Therefore, it is always the hot issue of foreign and domestic researchers.The author examined a large amount of literature, analyzed the current foreign and domestic methods of cylindrical error measurement, and put forward the capacitive shaped surface sensing method used to measure the cylindrical error according to the criteria of cylindricity error evaluation and the basic capacitive sensors theory. This method takes advantage of sampling surface to measure cylindrical parts, of which this method can gain all the information of measured surface so as to achieve fast, accurate, non-contact measurement of cylindrical error, making up the drawbacks of the existing measurement that is sampling by sampling point.This thesis studies and derives the solving process and nature about part of the capacitor, and uses ANSYS software to extract the part of the capacitor in multi-conductor system of three-dimensional solid mode, By comparing and analyzing the extracted capacitance, it verifies the accuracy of measurement principle of the capacitive shape surface sensing method as well as demonstrating the feasibility of this method at the same time.In the end, based on the measuring principle of capacitance shape surface sensing method, this thesis designs the capacitive probe, and makes a simulated experiment for the designed capacitive probe. By analyzing the experimental results and the distribution of electric field, this thesis suggests that the designed capacitive probe can greatly reduce the influence of fringe effects and the external interference on the measuring results. At the same time, it carries out optimization to the dimension parameters of capacitive probe structure and finds the primary and secondary relations and the optimal combination of the effects of all dimension parameters on the measuring results. As for the requirement of certain company on their produced parts that the cylindricity error cannot be higher than 0.002 mm, this thesis makes an overall design of the mechanical structure of measuring system based on the fundamental theory of capacitance shape surface sensing method.