Research On The Warm-cold Composite Precision Forming Process Of Large Module Spur Gear

With the rapid development of modern industry, spur gear as one of theimportant transmission devices, has been widely used in the automobile and relatedindustries, and the need of the technical requirements has become higher and higher.The conventional mechanical chipping gear does not meet the demands of themodern automobile industry. Then, the precision forming process of spur gearemerged. Compared to the former, gears manufactured by precision formingtechnique have lots of advantages such as good mechanical properties, compactstructure and better wear resistance properties of tooth surfaces, etc. At present, thecold precision forging is the primary precision forming process. While in coldprecision forging process, there exist such problems as large forming loads and lowdie life, etc. The warm-cold composite precision forming process which solves theexist problem in cold precision forging process has been received more and morecountries’ attention now.In the present paper, numerical simulation is utilized to investigate the warm-coldcomposite precision forming process of the spur gear. Three forging processes withdifferent modes called fixed die-plunger mode, fixed die-restrained split flow mode andfloating die-restrained split flow mode are compared respectively. The last mode is chosenas the final warm forging process plan. The effects of processing parameters, such asbillet initial temperature, mold preheating temperature, friction coefficient andforming speed, on the warm forming process of spur gear are investigated. Resultsshow that the forming load is mainly effected by the billet initial temperature and moldpreheating temperature and it decreases with the increase of the aforementionedtemperatures. The forming speed play the main roles in die wear, and the degree of diewear reduces with the decreases of forming speed. The optimum process parameterscombination was determined by the orthogonal test.The effects of different sizing amount and sizing frequency on the tooth errorwere studied. The results indicate that the lower tooth error and better sizing effect can beachieved with unilateral allowance between0.1mm and0.3mm. If the gear accuracy andthe die wear are considered, an allowance of0.2mm is acceptable. With the increase ofsizing frequency, the tooth spring back reduces and the tooth error decreases, but the gearaccuracy class isn’t significantly improved. Considering both the gear accuracy and the mold cost, once sizing process is chosen. Corresponding physical simulation experimentsof sizing process are carried out and it is found that the physical experiment and numericalsimulations have the approximate results.