Study On The Key Technique Of The Gas-assisted Injection Molding

Gas-assisted injection molding is a new plastic forming and processing technology,which is derived from the conventional injection molding and structural foam molding.Its working principle is that utilizing high pressure nitrogen to promote the filling process of the melt,and form the hollow part in the gas channel of the plastic production,then finish the injection molding process in the effect of gas-holding pressure. The reinforcing ribs forming by the gas channel enhance the strength of plastic parts,remove the warpage defect and supply the possibility of once molding of plastic parts with both thick and thin sections.Therefore,in that era,GAIM was known as a revolutionary technology in the plastic processing industry.With the development of motor industry,light-duty,environmental protection and household possession is the trend of worldwide automobile industry.Reducing cost, increasing production and efficiency, shortening research and development cycle of new product is the most important task to our national automobile industry.GAIM plays an important role in this process.The molding problem involved in complicated plastics,thin plastics,high strength plastics and exact plastics has caught engineer's and scholar's great attention.This article is put forward in such an circumstance,the purpose is having a research on the key technique of gas-assisted injection molding and processing parameters,which affect the gas finger at the inner wall of GAIM production.In addition,we optimize the processing conditions of the car storage box and design the practical producing mold of the truck roof handle.The followings are studied in this paper:1.Study of the gas fingering defect with the influence of the GAIM processing parametersUsing the rectangular board as a model,the influenced connections of six different processing parameters are studied,such as melt shot size,gas delay time,gas injection pressure,mold temperature,melt temperature and gas injection time.It shows that the most important processing parameters that affect gas fingering are gas delay time,mold temperature and gas injection pressure orderly.The conclusions of level difference with reference to largest gas fingering length and range are the same.Therefore,it's very important to choose the reasonable gas delay time,melt temperature and gas injection pressure prior.2.Study of the gas fingering defect with the influence of processing parameters interactionThe gas fingering defect in GAIM parts with the influence of processing parameters interaction are researched with the methods of numerical simulation and orthogonal experiment.The influenced connections of three different processing parameters interaction were studied,such as melt temperature and gas delay time,melt temperature and gas injection pressure,gas delay time and gas injection pressure.The results show that:compared to others,melt temperature and gas delay time interaction is more serious to gas fingering influence.In order to reduce the gas fingering defect of GAIM production,we should avoid the situation that shorter gas delay time and higher melt temperature coexist.3.Optimization of the GAIM processing conditions of the car storage box Based on the Moldflow software, the car storage box is analyzed and compared by numerical simulation between Conventional Injection Molding and Gas-Assisted Injection Molding.The conclusion is as follows:the shrinkage rate of the volume, welding lines and the warping deformation of the productions which use the GAIM processing ,are weakened to a large extent, and even are eliminated in some parts,so that the GAIM technology improves the product's surface quality and strength.Due to the gas injection, the consumption of raw materials is reduced, the weight reducing rate of the product reaches up to 40.4 percent.In addition,according to the results of numerical simulation,the optimum GAIM processing parameters are: the melt short-shot is 95 percent, gas delay time is 0.3s, the gas injection pressure is 8Mpa.4.Design of the GAIM practical producing mold of the truck roof handle Based on the existing physical simulation mold of our group,we have further designed the practical producing mold of the truck roof handle.The optimum gate location has been chosen according to the CAE analysis.The side core-pulling mechanism with hydraulic pressure promotion and the component of the gas nozzle have been designed.Finally,the truck roof handle has been put into practical producing application.