Study On Micro 3D Mold Processed By Micro EDM Milling

The need for micro parts is rapidly increasing as the developing of MEMS (micro electromechanical system). In micro forming technology, two methods, micro hot embossing and micro injection molding, are used in industries of electronic, aerospace, biotechnology and precision instruments, due to its good precision and high forming efficiency. Photolithography process, micro EDM, LIGA techniques, micro electrochemical machining technology, micro milling etc. are used to generating micro mold because of its tiny structure, high dimensional accuracy and surface quality. Among them, micro-EDM milling what is used to remove material from any electrically conductive and semi conductive materials without mechanical contact, shows a great potential development in machining micro 3D structure. It is an effective method to generate arbitrary 3D micro mold machined layer by layer using simple shaped electrode, which is controlled to move along designed tool paths.For the advantage and application of micro-EDM milling in micro mold processing, this paper carries out research on micro-EDM milling. The NC program is developed by LabVIEW based on the existing vertical precision Micro-EDM device, which includes the tool electrode processing, gap voltage acquisition, axis motion servo control during milling duration, and location information of x-y-z axis stored.The surface quality and machining efficiency of 3D micro cavities machined by micro electrical discharge machining (EDM) is related to layer thickness in milling. In order to improve machining efficiency of 3D micro-EDM, layer thickness should be determined reasonably. The impact of layer thickness on the surface quality of micro molds prepared by micro EDM and hot embossed products is studied in this paper. Furthermore, relationships of surfaces of micro hot embossed plastic parts and micro-molds, and the variation of surface profile of molds after hot embossed are analyzed. Experimental results indicate that the bottom surface roughness of mold cavity enlarge along with the increase of layer thickness; the surface roughness of sidewall of molds is irrelevant to layer thickness; the variation of micro plastic part surface roughness, Ra, Rvk and Rpk follows the corresponding micro mold surface roughness, Ra, Rpk and Rvk; the surface profile of mold cavity has changed after hot embossed, which can show up in the variation of surface roughness, Ra, Rpk and Rvk. These results are helpful to improve the surface quality of micro plastic parts and micro mold.Besides, this paper study on processing quality of Micro-EDM milling, which lays a foundation for high precision processing of micro mold. Multilayer thickness combination machining is employed to process series of micro molds, which obviously reduce machine time and advance bottom surface quality. Ra and Rpk of bottom change gently via layer thickness. Straightness error is adopted to evaluation shape error of sidewall surface profile, and the results are compared and analyzed. In addition, this article analyses dimension error of micro mold in the X, and Y direction, and the effect of sidewall structure on discharge state in micro-EDM milling. The actual discharge gap is acquired by tool path and size, and work actual size, which reveals that the actual discharge gap in the X direction is 0.1 ?m, while that in the Y direction is 5.1 ?m. Based on bottom contour model, this article simulate the impact of relative electrode wear ratio on bottom contour, and the effect of tool size and layer thickness on bottom contour while there exists error and change variation range of wear ratio.