Theoretical And Experimental Study On Cold Rolling Precision Forming Of Spline Shafts

This work is supported by the National Natural Science Foundation ofChina(NO.50675145, Theoretical and Experimental Study on the Cold RollingPrecision Forming Process of Thread or Spline) and the Key Scientific Project ofShanxi Province(NO.50675145, Study on New Technology and EquipmentDevelopment for the Cold Rolling Precision Forming Process of Shaft).Cold rolling precision forming process of spline shafs is one of the non-chipforming advanced manufacturing technologies. It has the characteristics such as havinghigh forming efficiency, forming components with better property and so on. But it hasnot been widely used in the practical production because of the lack of knowledge aboutthe complex cold rolling forming mechanism as a kind of cold volume plasticdeformation. Aiming at those problems exited in the theoretical and equipment researchon forming process and in the precision control on component forming, this work givesa systematic study on the precision forming mechanism of cold rolling process of splineshafts, the calculation of force and energy parameters, the strengthening mechanism ofgear tooth surface, the forming precision and quality control based on the combinationof theoretical analysis and experimental study. The following main research contentsand conclusions have been made.According to the theoretical analysis on the cold rolling precision forming processof spline shafts, the revolving condition and the geometric condition to form on theindexing stage were worked out, moreover, the rolling wheel design was schemed outwhich limits the minimum number of teeth and requests addendum electroplating toimprove the revolving condition. Based on the analysis of the double-sidednon-backlash meshing, the characteristics of contact area between rolling wheel andworkpiece and the sliding mode of the contact point were brought out. On the basis ofslip line field theory, the unit average stress at the cold rolling forming process of splineshaft was worked out precisely, the method and influencing factors to calculate thecontact area between rolling wheels and tooth was presented, meanwhile, the rollingpressure and rolling moment in the cold rolling process were calculated. The theoreticalanalysis is the support for both the determination of process parameters and the designof machine or rolling wheels.According to the theoretical analysis, a vibration damping design applied to the spindle of the cold rolling machine has been brought out and has been used in thedevelopment of special NC cold rolling machine which is co-developed with enterprise.As the result, the key problem has been solved which is the deformation force variationleading to the low forming precision during the cold rolling forming. A system wasinnovatively constructed for testing the force and energy parameters during the coldrolling precision forming of spline shafts, and the variation of rolling pressur and rollingmoment were in-circiut tested. The effect of the rotational speed and feed rate of therolling wheel on the maximal rolling pressur and the maximal rolling moment wasanalyzed and the theoretical calculation of the force and energy parameters was verified.A comprehensive test system was firstly designed to obtain cold rolling deformationaccurary, surface quality and mechanical properties, and the flow characteristic of themetal on tooth surface was analyzed, and the effective range of the deformation duringthe practical cold rolling precision forming was marked out. Then, the strengthening andhardening mechanisms in tooth surface was obtained based on the theoretical analysisand experimental study on the machining accuracy and the performance of the splineshafts which were made out by cold rolling precision forming press. The experimentalso verified this forming technology could been applied to make components withcomplex shape and high precision and could improve the microstructure then toenhanced the performance. It could be considered that the processing meet the shapeand performance requirement simultaneously and especially meet high quality, highprecision requirement of axial parts production needed by national defense industry.The relationship was carried out between the cumulative pitch error and everyprocess parameters according to analysis on the cumulative pitch error brought out incold rolling precision forming process of free-indexing spline shafts, then a rollingmethod controlled by speed synchronization was put up to realize the dynamic indexingin cold rolling and to improve the forming accuracy. In addition, the cause brings aboutthe usual forming defects was analyzed, and then a quality control method was putforward. This work has theoretic value and practical meaning for extension andapplication of the cold rolling precision forming process of spline shafts because that itsolves the key technical problems in the industrial application and it expands thetechnology theory in cold rolling precision forming press of spline shafts.