Experimental Research On Electrical Discharge Machining Of Microscale Structure Mold Insert

The polymer microfluidic chip is widely applied in some fields such as biochemistry, clinical, medical and environmental, and the demand quantity of the chip is rapidly increasing. Hot embossing and injection molding are the main technological methods to achieve its mass production; however, the fabrication of the microscale structure in the high performance die steel is the key to realize these technological methods. With the low cost, flexibility in material selection and non-contact processing features, EDM has a unique advantage in the manufacturing of micro structure. Therefore, it is greatly significance to carry out the study of the fabrication of the microscale structure in the high performance die steel by EDM, and promoting its practicality, mass production.Firstly, a narrow slit type electrode was used instead of groove type electrode to fabricate a convex structure. The experiment of narrow slit cutting in the copper tungsten (W70%) which thickness is 6 mm by LS-WEDM with (?) 0.1mm Cu-wire was carried out. In the experiment, the relationship between the machining parameters and the width of narrow slit in the first cutting was investigated, and the removal amount of each cutting in the total three cutting was figured out. Based on this experiment, the offset value of each cutting in the multi-cutting could be confirmed so that the narrow slit cutting could meet the requirement of dimensional accuracy and surface quality, and the narrow slit was cut in the copper tungsten, which width was 140±2μm, surface roughness Ra was 0.37μm.Secondly, the narrow slits electrode which width were 200μm,160μm and 140μm were cut to carry out the fundamental experiment of fabricating of micro convex structure by precision EDM. The relationship between shaking amount and forming dimension, and the relationship between the number of electrode stations and forming accuracy were researched respectively. The results showed that the forming accuracy of the convex structure was high when used four electrode stations.Then, in order to fabricate a variable cross-section micro convex structure, four narrow slit electrodes which maintained a certain relative position in an electrode plate were machined on the basis of the above theoretical research, formed an integrated multi-station electrode. Multi-station electrode could not only realize the electrode wear compensation, but also avoid repeated clamping, alignment and positioning error caused by the replacement of multiple electrodes in the EDM. The machining results show that the forming accuracy of the convex structure becomes worse with the decrease of the forming convex height. This phenomenon is analyzed from the perspectives of the EDM principle and the error reflection mechanism.Finally, a multi-station combination electrode was designed to fabricate a complex micro groove structure. The multi-station was retained while the difficulty which removed the rounded corner in the convex structures intersection by HSM was solved by this combined structure. The machining results show that the height and width error of the micro groove structure are within 3μm, and that can be satisfied with the demand of micro fluidic chip molding.