Research On Micro-gear Mold By Micro-WEDM Machining

With the rapid development and wide application of micro electromechanical system(MEMS), as the main drive and a power component in MEMS devices, realizing the machining of micro gear with low cost, high efficiency, high precision become the focus of the scholars both at home and abroad. Because micro etching, LIGA /UV-LIGA,micro cutting etc have the disadvantages of high processing costs, complex process,limited processing material, they can not meet the need of micro gear with mass production. While micro extrusion forming technology(Micro-extrusion) has the advantages of low processing cost, simple process and it has the potential of realizing the mass production of micro gear with high-efficiency. But the micro gear mould need to be designed and fabricated separately, this is the key of Micro-extrusion for wide application.In this paper, the mathematical model of the involute micro gear is established and UG NX8.0 software is used to conduct parametric modeling. A set of micro gear mold is designed, the module is 0.1mm and the number of teeth is 10. In order to plan micro gear mold machining path, compensate machining gap conveniently, and improve machining precision, UG NX8.0 software CNC wire cutting is used, and NC code is generated automatically by the post processor.In order to improve the micro-WEDM speed and reduce the surface roughness of micro gear male die, this paper conducts a three factor central composite experiment including open circuit voltage, discharge capacitor, pulse width. The mathematical model of machining speed and surface roughness are established using response surface method. The machining parameters is selected taking into account the machining speed and surface roughness. As the tooth profile of micro gear male die after micro-WEDM is incomplete, this paper presents micro-WEDM second processing method, and a self centering flexible fixture is designed. The fixture can ensure the coincidence between locating datum and technology datum of micro gear male die, avoiding base noncoincidence error. The micro gear male die without defects of tooth profile and the tip diameter is 1197.5μm is machined using the fixture. The machining defect of microWEDM for micro gear male die is solved by the method.In view of the problem of micro-WEDM for micro gear female die with large thickness, considering micro gear female die can be multiple cutting processed after a single clamping, in order to improve machining speed and reduce surface roughness,this paper presents multiple cutting processing of micro-WEDM for micro gear female die. To ensure higher processing, the rough machining is conducted by adopting appropriate processing parameters without wire electrode lagging; To reduce the Ra of micro gear female die, the finishing machining is conducted by adopting low machiningparameters in compressed gas medium of 0.05 Mpa. The tip diameter of the micro gear female die is 1210.5μm, the Ra is 0.52μm.The micro gear is machined successfully by micro extrusion forming technology(micro-extrusion) using the micro gear die. The tooth profile of the micro gear after micro-extrusion is complete and the tip diameter is 1205.2μm, verifying the practicality and effectiveness of the micro gear mold machined by micro-WEDM, promoting the feasibility of micro-extrusion to achieve the mass production of micro gear with low cost, high efficiency.