Research On Injection Warpage And In-mold Bonding Of Polymer Flat Micro Parts

As its short injection cycle and high efficiency, micro injection molding is an important fabrication method of polymer flat micro parts. Warpage is one of the major problems in micro injection molding, which could not only weaken the injection quality, but also affect the following working procedures. Thus, warpage has been a research focus for domestic and foreign scholars. For the fabrication of polymer flat micro parts, the bonding procedure should be conducted in special facilities and is separate from molding, which leads to long production cycle and high cost. Therefore, to develop an efficient bonding method is the key part in the mass production of polymer flat micro parts.In this paper, the micro injection molded polymer flat micro parts were taken as the research object, the warpage controlling method was developed in terms of the residual stress in micro injection. Through the simulation and the measurement experiment, the influence order of the process parameters on warpage was analyzed as well as the effect of technological structures on warpage improvement. Further more, the solvent-assisted in-mold bonding experiment was conducted based on isopropanol. The major contents are as follows:A core-removable micro injection mold was designed. The insert structure was selected and the Si chip was fabricated as the core by MEMS process. With the utilization of traditional design discipline, the gating system, mold temperature controlling system, exhaust system and ejection mechanism were implemented. And a removable assembling method was designed to realize the rapid and non-damaged replacement of mold core.With the Taguchi method in the simulation, it was analyzed that the influence of injection process parameters and technological structures on warpage. Moldflow was conducted to research the influence of melt temperature, packing pressure, mold temperature and cooling time on warpage. and optimize the parameters. Further more, the weakening effect of technological structures on warpage was analyzed in the same conditions. And its influence on residual stress improvement was studied by Ansys.The warpage measurement experiment was implemented. According to the simulation results, the warpage values were measured under different process parameters. And the change of warpage values was compared to the former one after adding the technological structures, in order to test the simulation conclusion. In-mold bonding experiment was completed based on the isopropanol solvent. The swelling of PMMA was tested under different temperatures and times in the isopropanol. and the micro channel shapes and surface roughness were measured. Besides, the in-mold bonding experiment was carried out with isopropanol on Babyplast610micro injection machine, the bonding strength was tested through tensile experiment, and the process parameters were optimized.