Research On Silicon Based Micro Injection Mould Design And Insert Fracture

Micro injection molding is of high efficiency and low cost, and can easily be put into large production. Mould insert of micro injection mould is the key part for the manufacturing high precision micro channel on the micro fluidic chip. It can be made from both metal and nonmetal material. However, the mould insert made from nonmetal material, for example silicon insert, has great advantage over metal material: it’s more suitable for the high transform speed of micro injection; it can also make full use of the advantage of MEMS manufacturing line; it has both excellent physical and chemistry performance. While, the disadvantages of silicon insert can be concluded into2aspects:1) it’s hard to fix the silicon insert on the mould made from metal;2) it’s easy to fracture during the injection process. Therefore, it is of great value for designing the silicon based micro injection mould and studying the silicon fracture problem.This article aims at researching these problems having put forward, the main work having been done can be conclude into the following aspect:Designed one set of micro injection mould based on dual-thread connecting to fix the silicon insert to the mould base. The silicon insert is fastened in the plunger ring by the thread fit between the plunger ring and the supporting plate. Then fasten the whole part into the mould base by the exterior thread of the plunger ring and the inner thread of the mould base. Designed the injection system, ejecting system and the mould temperature circulate system. The new designed mould has improved the lifetime of the silicon insert to60times per piece.In order to study the fracture mechanism of the silicon insert, analyzed the crack propagation of the silicon insert under different temperature and pressure loads by ANSYS software. For the injection pressure load, the mold temperature was fixed to70℃and the pressure loads ranges from60MPa to80MPa. For the temperature load, the injection pressure was fixed to70MPa, the temperature loads ranges from60℃, to80℃. From the analyzing, we know that the injection pressure is the main factor for the crack propagation of the silicon insert.To know how the injection affects the silicon fracture, established one test platform for measuring the dynamic pressure in the cavity, designed the special mould for measuring and solved fixing problem of the pressure sensor. For the purpose of using one sensor to measure pressure of multi-point, a small clearance fit of axle hole was designed between the supporting plate and the fixed mould. From analyzing the measuring data, we conclude that:the distribution of pressure peaks isn’t absolutely symmetrical, and the maximum pressure didn’t occur in the middle as expected. Further studying shows the uneven distribution of the pressure in cavity is caused by the air compressing problem.The results play a guiding role in designing silicon based micro injection mould and studying the silicon insert fracture mechanism.