Heat Response And Mechanisms Of RHCM Mold With Annular Heating And Cooling Gap

Rapid Heat Cycle Molding(RHCM)technology has been widely used in the injection molding industry because of it's advantages of high efficiency,energy conservation,environmental protection and forming complicated plastic parts with high quality for one time.In RHCM process,the control of mold temperature has great significance to the productivity and molding quality.However,as the most widely used mold temperature controlling technology,steam heating combined with water cooling(S-RHCM)has the deficiencies of complex peripheral equipment,low energy efficiency and limited heating temperature.Electric rapid heat cycle molding(E-RHCM)has simpler structure,higher heating temperature and lower cost,but it is difficult for assembly and disassembly and the cooling efficiency is low.The RHCM mold with annular gap heating/cooling channel used a new type of mold temperature controlling method,which combined electric heating and water cooling(AG-RHCM),its characteristic is that the diameter of the hole on mold is larger than the diameter of heating rod,the annular gap between the rod and hole wall will be formed after assembling.During the heating process,the liquid in the gap act as heat transfer medium,and during the cooling process,the annular gap can be used as the cooling channel.The RHCM mold with annular gap heating/cooling channel can reduce complex peripheral equipment,and it's easier for mold design,manufacturing and assembly compared with S-RHCM and E-RHCM mold.However,the current research about this technology is not very sufficient,especially for the effect of mold thermal response and the heat transfer mechanism in the heating and cooling process.The effect and mechanism of pressure response in the annular gap is not clear,which remains further research.Focusing on the existing problems,the effect and mechanism of thermal response for the AG-RHCM mold is studied.AG-RHCM experiment system is established based on the characteristics of this method when the mold is rapid heated or cooled.After test and evaluation,the system can realizes manual and automatic mode of heating and cooling cycle,providing a platform for experimental research on mold thermal response and pressure response.The effect of thermal and pressure response of AG-RHCM mold in rapid heating,cooling and circulating process is investigated based on experimentation.Combining with the characteristics of heating and cooling process,the factors affecting thermal and pressure response are analyzed.The effect of heating/cooling time,flow rate of cooling water and mold structure parameters on the thermal response of mold cavity surface is investigated,and the affecting mechanisms of these factors are proposed.The influence of flow rate of cooling water,initial conditions,gas content in the medium on the pressure response is studied.Combined with the expansibility and compressibility of fluid,a calculation method for calculating the pressure in annular gap of the AG-RHCM mold heating and cooling channel is proposed.The methods for controlling pressure response are summarized during rapid heating process.The finite element model for the analysis of AG-RHCM mold thermal response is built.By the way of simplifying the heating process of the medium to the heat transfer process with equivalent thermal conductivity for medium,the mold surface thermal response that are consistent with the experimental results are obtained through simulation.The temperature field of internal mold and the medium inside the gap in the RHCM process are also obtained.The effect of mold-opening temperature,cooling water temperature and annular gap size on mold thermal response are investigated based on the numerical simulation.The AG-RHCM,S-RHCM and E-RHCM analysis model are established,and the difference in the aspect of mold thermal response in the RHCM process between these three kinds of mold temperature control method are analyzed.Aimed at the problem of uneven temperature distribution in AG-RHCM mold,the mold structure is optimized using the response surface method,the mathematical model used for AG-RHCM mold structure design is built,and the uniformity of mold surface temperature distribution is improved significantly,which provides theoretical guidance for the AG-RHCM mold design.