Research On The Robot Welding Technology Of The Backward Centrifugal Fan Impeller

The backward centrifugal fan impeller as a core component of the centrifugal fan,is welded by multiple thin-walled parts.However,its welding quality is not guaranteed due to the thin sheet,the large quantity of welding joints,the high labor intensity of manual welding.With a significant influence on the performance and service life of the fan,the welding quality of the impeller as a determinant factor in the market competitiveness of centrifugal fans,has been prioritized by related enterprises engaging in fan production.And the automatic welding of the fan impeller has been achieved thanks to the rapid development and extensive application of the robotic welding system,providing an opportunity to improve its welding quality and reducing labor force.For all this,related technical researches on the backward centrifugal fan impeller using robot welding has been conducted in this paper to develop a rotary double-station positioner,and to realize its integration with the robot welding system,as well as to research parameters,welding sequence and welding direction of the welding process.By doing so,the welding quality of the backward centrifugal fan impeller can be guaranteed with the reduction of welding deformation.The main work of the thesis includes the following aspects:Firstly,the thesis has stated the background and significance of topic selection,analyze the development and application status of the robot welding system and the welding positioner at home and abroad.Meanwhile,domestic and foreign research progresses on the prediction of welding deformation have been also summarized to propose research contents of this paper.Secondly,an overall design scheme of the rotary double-station robot welding system has been put forward against the current situation that the fan companies heavily depend on manual welding production of the backward centrifugal fan impeller with the combination of the existing robot welding system.Besides,a rotary welding positioner with double stations and jigs for welding the backward centrifugal fan impeller have been designed.Moreover,type selection has been conducted on the robot welding system in accordance with the structure and material type of the impeller.And by integrating the control system of each functional module in the rotary double-station robot welding system,the human-machine interface has been developed with the VC++6.0 languageThirdly,as it's difficult to search the optimal welding parameters using tests on the thin sheet of the backward centrifugal fan impeller,the weld pool of welded joints of the local finite element model has been numerically simulated and verified under different welding parameters using the Visual-Environment software based on the thermal elastic-plastic finite element method together with the double-ellipsoid thermal source model.Furthermore,the deformation and the post-welding stress of the local finite element model have been analyzed through comparing different welding parameters,so as to find out optimal welding parameters,such as welding speed and welding current,etc.Fourthly,the welding sequence and the welding direction of each welding joint should be strictly controlled against the problem of thin sheet,large quantities of welding joints and welding deformation that is easily generated after welding of the backward centrifugal fan impeller,so to reduce post-welding deformation to a greater extent.In this paper,the post-welding deformations of the backward centrifugal fan impeller have been numerically simulated under different welding sequences and welding directions with the Weld-planner software based on the inherent strain method.Meanwhile,the optimal welding sequence and welding direction have been located through comparing deformations generated under different welding sequences and welding directions.Finally,the paper summarizes the whole work and proposes the future research direction.