Research On The Online Measurement Method Based On The Green Laser Scanning For Large Hot Forgings

Large forgings have long production cycle, numerous and complex manufacturingprocess and often consume huge material and energy sources. Therefore it is of greatsignificance to ensure the rate of finished forging products and the production efficiencyfor the development of the forging industry and the improvement of the economic benefits.The size is an important factor for timely detection in the process of the forging andespecially the size of the critical parts plays an important role due to the fact that size isthe main basis of the next rolling pressure, rolling reduction, and the number of rolling.Therefore, it is of great important to detect the size of forgings accurately and timely,monitor the shape and the size of the forgings, and fine-tune the forging equipment timelyfor improving the forging technology, the machining accuracy, and the productivityefficiency in the forging process. To overcome the drawbacks of the existing methods forsize measurement in the manufacturing process, a new size measurement method isproposed in this paper. The main contents are represented as follows:Firstly, to solve the existing problems in measureing process of large hot forgingsand meet measurement requirements of different forgings, a new size measurementmethod based on laser scanning has been proposed. According to different characteristicsof the measured forgings, the line laser and CCD are controlled to scan the forging alongthe vertical and horizontal direction. The captured images are transferred in time tocomputer to perform the data analysis and size measurement procedure. Moreover, theinstruction of the rolling reduction and working position location can be instructedaccording to the high brightness and good direction performance of the laser line. Theproposed method can meet the size measurement requirement of both the regular andirregular forgings.Secondly, a mathematic sanning measurement model based on the motion of theCCD is established and a solution of the optical center motion trail on the basis of thetwo-dimensional chessboard plane is proposed. The motion trail of the camera is solvedaccording to the feature point coordinates on the reference plane in different frames.Furthermore, the overall three-dimensional size is achieved by combining the measurement model with the optical center motion trail.Thirdly, the intial calibration for the internal and external parameters is solved byusing two-dimensional plane method, thus completing initial calibration of the wholevisual system as well. Then to improve the accuracy of the coordinate reconstruction ofthe forgings’ surface, particle swarm optimization algorithm is utilized to optimize thesystem structure parameters and the error of the optimized results is also analysed.Finally, a size measurement system based on the laser scanning is established after agreat deal of theoretical studies. The first test on standard cylinder forging is conductedunder the laboratory conditions, and the second test on the spherical shell cover has beendone in workshop conditions. The measuring method is feasible according to theexperimental results.