Development Of Dimensional Measurement System For Large Forgings Based On Laser Ranging

As the key components of large complete sets of equipment,large forgings have played important roles in the fields of advanced science and technology construction as well as national defense development.Dimensional measurement of large forgings in high temperature is one of the vital parts during forging process and measuring accuracy is of great significance for the formulation of process and utilization of material.The temperature of the forgings is usually between 850? and 1250? in the forging process,so it is quite difficult to get the size information with traditional measurement methods.Based on the time-of-flight method,laser ranging technology has the advantages of high precision,high speed and wide range.It will be significant to apply it to on-line dimension detection of large-scale forgings.A 3D scanning system was developed in this paper using a 2D TOF laser range finder in combination with other components like servo motor,motion control card,reducer.Then corresponding interface was developed to control the whole system.The system can quickly obtain the point cloud data of the measured object,which lays a foundation for the study of the size measurement for the large forgings.The error sources of the scanning system are analyzed in this paper and the corresponding methods are used to reduce or eliminate the error.For the ranging error of LMS-500 laser finder,the average value of multiple measurements is used to improve the measurement accuracy.An edge error correction model based on the beam spacing is proposed aiming at reducing the edge loss caused by the mixed pixels.Finally,the calibration of the system is completed using the wall as the calibration object.The scanning experiment of the large piece with three-step shaft was completed in the laboratory and the point cloud of the partial surface was gained.The experimental result showed that the profile of the point cloud was similar to the shape of the piece.The length measurement error of the three shaft segments was less than 15 mm and the measurement error of the three diameters was less than 6mm,which can meet the requirements of measurement accuracy of large forgings.In addition,the system was applied to the measurement of the forging field,and a clear point cloud image was obtained.