Research On Mechanical Technology Of Micro-indexing Structure By Using Micro-WEDM

Micro wire electro discharge machining(Micro-WEDM) is a kind of micro machining with the feature of high precision, high efficiency and flexibility. Because there is no physical contact and macro-forces between the tool and the workpiece, this technique can process hard, strong, heat-resisting and wear-resisting materials without the influence of its physical characteristics. Micro-WEDM is widely used in many processing fields such as micro tools, micro dies and special components with complex microstructure. This paper will expand the processing capacity of Micro-WEDM, aim at machining micro indexing structure, exploring the processing technology of sharp corner and exploring the influence of main electrical parameters on machining efficiency and machining precision. The final goal is to realize machining micro indexing structure with low cost and high precision.The author set up a hardware system for micro indexing structure processing on the basis of analyzing the process of machining indexing structure by Micro-WEDM, using PLC to control the spindle, achieving the function of horizontal rotating with a constant speed and rotating with a fixed angle. Then the system can machine micro indexing structure cooperating with the movement of micro wire.Fundamental experiments of Micro-WEDM by machining one step of manufacturing micro indexing structure are conducted on the basic of the system above. The effects of main electrical parameters, including voltage, capacitance and pulse width, on Material Removal Rate(MRR) and Surface Roughness are analyzed by making single factor experiment. In order to explore the influence of the interaction between the factors above on the response characteristics, the process experiment is carried with the method of center combination experiment. The mathematical model of voltage, capacitance and pulse width as well as MRR and SR are established by using response surface methodology, obtaining best parameter combination of voltage 90 V, capacitance 2150 p F and pulse width 7μs on account of both MRR and SR.Based on the precious work, several indexing structures is machined by Micro-WEDM, the parameters obtained above is applied to machine square tool and get a well-shaped tool, the result shows that the error between predicted value and actual value are less than 10% about MRR and SR, verifying the accuracy of mathematical model. A 3×3 allay structure of micro pyramid allay is manufactured on the tip of Tungsten electrode which diameter is 600μm, through the experiments, design an experiment of cutting grooves on different thickness of workpiece to explore effects of cutting thickness on discharge gap when machining micro indexing structure by Micro-WEDM, an experiment machining the same micro pyramid allay is carried out and shows the new compensation method can control the smallest dimension error as-1.8μm. Based on this experiment, a 8×8 micro pyramid allay is machined. Multiplicity cutting is applied to machining typical micro cutting tool on the basic of parameter optimization. Then, the micro tool with 0.42μm of SR is successfully processed, expanding the application range of indexing structure machining system. At last, a micro tower with length 3.3mm is machined which verifies the ability of manufacturing micro allay structure along axial direction and reveals the system has a wide applicability.