Study On The Mechanism And Technology For Spouted-accumulated Forming Of Large Diameter Plastics Pipe

The forming mechanism and technology of the plastic pipe,especially large diameter plastic pipe,are studied in this paper.Based on the analysis of the traditional large diameter plastic pipe molding technology(extrusion and winding and welding forming),and combined with the principle of additive manufacturing technology,a new technology of forming the large diameter plastic pipe,which is called the Spouted-Accumulated Forming(ASF),is first proposed,and the equipment of the spouted-accumulated forming has been successfully developed,and the large diameter pipe with a diameter of 400-500 mm is formed by the deviceIn this paper,the development status,existing problems and development trend of traditional large diameter plastic pipe applications are reviewed.In order to slove the problems existing in the traditional forming technology of the large diameter plastic pipe,the spouted-accumulated forming technology,which is based on calendering and combined with additive manufacturing technology,has been put forward.The principe of this new technology is that the ploymer melt with a certain temperature and pressure is firstly provided by an extruder,then the melt is spouted inside a certain room via a nozzle,and the room is constrained by the calendar rolls and the pipe blanks,finally a continuous and compact large diameter pipe with the size precision is spiral wound formed by the welding of the spouted melt embedded into the pipe blanks and the calendaring of the calendar rolls.According to the principle of spouted-accumulated forming technology,the spouted-accumulated forming device has been developed,and the equipments composed of extruder,calendring device,diameter adjusting mechanism,mechanical transmission system and control system.The mechanism of spouted-accumulated forming has been analysed in this paper,and the physical model has been established.At the same time,based on the quality conservation,momentum conservation law,the law of conservation of energy and polymers constitutive equation,the mathematical model of spouted-accumulated forming has also been established.According to the assumptions and boundary conditions,the velocity distribution,pressure distribution and temperature distribution of polymer melt in the process of spouted-accumulated forming has been solved.This will lay a foundation for the guidance of equipment improvement and process debugging.The performance of the pipeline formed by spouted-accumulated has been characterized through mechanical tests including tensile strength,impact strength,stiffness and flexible ring etc.,thermal performance test and microstructure analysis.Compared with the traditional molding method such as extrusion under the same forming conditions,the performance of the polymer pipe formed by spouted-accumulated has many advantages,which will provide important experimental data and technical support for promoting the application of the technology.In this paper,the key process parameters such as calender rolls speed,rotation rate of extrusion machine,melt pressure,melt temperature,melt spout velocity and the depth of nozzle embedded to the melt and pitch have also been analyzed.And these parameters affect spouted-accumulated forming.Through the analysis on thees key process parameters,it is expected to find optimal parameters of the pipe spouted-accumulated forming,which will provide the theoretical basis for the practical industrial production.The performance test of the pipe formed by spouted-accumulated has been analyzed in this paper,and the results show that the performance of the large diameter pipe formed by this process is better than the traditional method.Among them,the impact strength of the pipe formed by ASF is more than 1.75 times of pipe’s formed by the extrusion,and ring stiffness exceeds the national standard SN2 level 25% or more.Thus,the advantages of this method are further proved such as non-mold forming,flexible forming,simple process,low cost,good product quality and so on.At the end of this paper,the mechanism and the technology of spouted-accumulated forming polymer pipeline is further summaried and prospected,and relevant suggestions has put forward for the further improvement of the technology,which will lay the foundation for the industrial application of this technology.