Micro Electrochemical Machining Technology For Swirl Chambers Of Engine Fuel Nozzles

Manufacturing of micro and small metal parts has been a common difficulty in the field of aerospace, weapons and equipment manufacturing. The nozzle is one of the key parts of aero engine. Its micro-size swirl chamber is difficult to cut with traditional machining methods because of the following problems:hard materials, particular structure (inlet part is small and stomach part is big). Tools can’t reach the machining area easily and the structure of the nozzle may be ruined by cutting force of traditional machining methods. EDM machining technology will produce metamorphic layer which is also difficult to remove for small size parts. In this thesis, micro electrochemical milling technology is applied to machine the swirl chamber of the nozzle.Some important basic theory of micro electrochemical milling is firstly studied, including principle and characteristics of electrochemical machining (ECM) and micro-ECM and basic theory of micro-ECM milling. Then a two-stages (rough and finish) micro-ECM milling process scheme is designed, which use macro-ECM milling to remove most of the materials of the part with a mille-miter diameter rod electrode and micro-ECM milling to machine the micro features of the nozzle with a hooked electrode. Electrolyte for the workpiece material is selected according to its characteristics. And a simple on-machine manufacturing technology for small diameter electrodes is proposed with anodic dissolution method. Then two-stage micro-ECM milling experiments of rough and finish are carried out to machine swirl chambers of engine fuel nozzles by select appropriate milling parameters (move speed of the electrode, distance between milling lines, milling thickness, etc.), electrical parameters (voltage) and so on. The research of micro ECM for the swirl chamber of the nozzle is divided two stages. At roughing stage, the workpiece is machined with DC voltage, a rod-shape electrode and dilute H2SO4to remove the major allowances by quickly ECM dissolving and obtain the "funnel-shaped" swirl chamber structure with small finishing allowance saved for next stage. At finishing stage, the workpiece is machined with nanosecond pulse power,"ring conical scanning" micro-ECM milling is used to remove the tiny margin of the workpiece and to achieve precise shape of the swirl chamber. Meanwhile, mutual influence between electrical parameters (movement speed of electrode, milling line space, milling layer thickness, etc.) and milling parameters (machining voltage, etc.) is studied.Swirl chamber of the nozzle is successfully machined with ECM milling based on theoretical analysis and experimental study. And machining accuracy and surface quality of the workpiece meet the required technical requirements. The study will construct the theoretical basis of micro-ECM milling technology to solve difficult machining problems existed in many industries and to break through the bottleneck problem of industrial production of miniature metal parts.