Research On Measuring Method Of Geometric Error Of Large-scale Thin-walled Cylinder

Large-scale thin-walled cylinder is widely used in aerospace,automobile manufacturing,petrochemical and other fields.Spinning forming,as an advanced manufacturing technology for thin-walled rotary parts to achieve less or no cutting,is an important development direction of precision plastic forming,and has become one of the main processing methods for manufacturing large-scale thin-walled cylinders.In recent years,with the vigorous demand of aerospace,aviation and other national defense fields,together with the improvement of the overall level of the domestic manufacturing industry,the development of spinning equipment in China has reached a new height.With the development of spinning parts upsizing,how to measure the geometric error of large-scale thin-walled cylinder will also be highlighted.Due to their large size,small stiffness,the characteristics of difficult transportation and easy deformation,the measurement of large-scale thin-walled cylinder geometric error is difficult to rely on the existing measuring instruments.And if only simply enlarge the size of measuring instruments accordingly,designing the large-scale measuring instruments,it is neither economical nor convenient to such small batch production,and before or after the measurement the loading,unloading or positioning of workpiece are very difficult,the accuracy of the gage itself will also be affected,making the measurement error increases,the loss outweighs the gain.In order to solve the problem of measuring the geometric error of largescale thin-walled cylinders,it is necessary to improve and upgrade the existing measurement methods and evaluation models of the geometric errors combined with the actual measurement situation,so as to avoid the above problems encountered in the measurement.In this paper,the method of measuring inner or outer diameter of large-scale thin-walled cylinder,the method of measuring the roundness error of large-scale thin-walled cylinder and the method of measuring and evaluating the cylindricity error of large-scale thin-walled cylinder are proposed.By studying the current methods of correlating geometric quantities,the paper analyzes and verifies the advantages and disadvantages of the existing methods in measuring large thin-walled cylinders,improves and presents new measurement methods and new evaluation models.When improving the conventional measurement method of workpiece diameter,on the basis of it,an offline measurement methods of the roundness error and the cylindricity error are proposed.The measuring tool is designed to realize the function of measuring above three geometric quantities,this tool may improve the measurement efficiency and reduce measurement costs.In the process of sampling data,a matrix method is used to solve the roundness error evaluation model in the time domain,effectively avoiding the cumbersome and inefficient calculation of the conventional frequency domain method.A new evaluation method of the cylindricity error is put forward,and a corresponding evaluation model is established.This measurement method abandons the conventional discontinuous method of measuring the cylindricity error by each circular section of the cylinder,but adopts the continuous spiral line track measuring method,at the same time,the error separation technique can be used to separate the rotation error,the eccentricity error of the leastsquares center of circle and the straightness error in the sample.Compared with the existing cylindricity error measurement by each discrete circular section of the cylinder,the use of continuous approximate spiral line method can avoid discontinuous measurement and there is no need to ensure that the starting sampling point of the adjacent circular cross-section is in the same radial position,so as to obtain more accurate axial information of the cylindrical surface and improve the measurement efficiency.