Experimental Research On Electrical Discharge Machining Of Microstructure Mold Insert With Multi-station Combination Electrode

The disposable polymer microfluidic chip is widely used in many fields such as biology, chemistry, medicine and environmental testing. Nowadays, hot embossing and injection molding are the main process which is used for producing microfluidic chip in quantity, mosaic structure is mostly adopted for mold. Therefore, the quality of the micro mold insert has directly great effect on the quality of the microchannel of microfluidic chip. At present, LIGA and UV-LIGA are the two main process for fabricating micro mold insert. However, the cost of them is high and the process is complex. As the same time, the material of electroforming is limited to copper, nickel and nickel alloy. The electroforming layer is damaged easily because of softness, repaired difficultly with short service life. So, it is of great significance to study of manufacturing micro mold insert of mold steel with low-cost and high hardness for reducing the cost of microfluidic chip and promoting its applications.Firstly, in order to fabricate micro mold insert of mold steel, a new precise EDM method with multi-station combination electrode is proposed in this paper on the basis of comprehensive analysis of the concrete form of micro mold insert，the process of traditional EDM, the law of electrode wear and the compensation mode of electrode wear. In this method, the combination electrode is fabricated by WEDM firstly, and then it is used to form the micro-structure.Then,the major machining parameters are studied through the single factor experiments, including servo reference voltage, open circuit voltage, peak current, pulse interval, the electrode wire tension and wire speed, on processing speed, surface roughness and kerf width at cutting copper-tungsten. Based on the analysis of formation mechanism of corner error in WEDM, comparison test is done with best feed cutting to constant cutting and single cutting to several-times cutting. And then, the multi-station combination electrode is made by WEDM of several-times and constant cutting through the comparison test.In end, the study of experiment contains the effect of different material on surface roughness and the influence of different form and amount of movement on rounded corners and manufacturing gradient. The position of the mold insert and electrode is exchanged in experiment. Then the micro mold insert is formed with three-station combination electrode of copper, six-station combination electrode of copper, four-station combination electrode of copper-tungsten and sis-station combination electrode of copper-tungsten. Based on the analysis of the different efficiencies, the electrode wear of copper combination electrode is higher, the dimensional accuracy of the microstructure is worse, rounded corner is bigger, but surface roughness of the micro mold insert is better. The relative size error of microstructure formed with six-station combination electrode of copper-tungsten is less than5%, the surface roughness Ra is around0.3μm, which can satisfy the requirements of microfluidic chip.