| Aeroengine is the decisive factor of aircraft performance, reliability and cost. the aeroengine mainly adopts film cooling holes to cool the blades in order to make the blade running stable and reliable in the high temperature environment. The machining of film cooling holes is the key to film cooling technology. The size of film cooling holes is ranged from ? 0.2 mm to ?0.8 mm, depth to diameter ratio of 5 ~ 8. The number of the film cooling holes on single blade within the scope of tens to hundreds. The high-performance EDM spindle is indispensable to ensure that the quality and efficiency of film cooling holes. The EDM with high pressure fluid inside can timely update and clear the particle quickly from machining. Through a long and thin electrode rotation and axial servo feed can realize machining of film cooling hole efficiently. Accordingly, the EDM electrode spindle institutions with different diameter tubular electrode clamping, high pressure fluid inside supplying(?10 MPa), automatic compensation function and high precision rotary is of great significance to enhance the automation processing of film cooling machining technology and batch process of structure with small holes.Through the relevant technical research about spindle in domestic and foreign and existing equipment usage at micro-nano manufacturing laboratory of Tsinghua university, acquired the concrete structure, functional requirements of the spindle institutions. According to the function module of the spindle design, analysis and optimization, Put forward a kind of spindle which can realize ?0.3 mm ~?0.8 mm tubular electrode stable clamping, liquid pressure adjustable range of 0~10MPa, high precision rotation and compensation automatically. Moreover, the relation between the vibration of electrode and machining precision also been deeply analyzed.The spindle adopts the single channel rotary joint and high-performance conductive slip ring has realized the liquid pressure(P?10 MPa) continuous supply and stable link between the power and electrode(U?300V, I?30A).By dividing the clamp into eight parts and flexible clamping, the spindle achieved the ability to clamp tubular electrode in different diameter. That, combined with the creep feed mechanism, implement the automatic compensation of the electrode. The high precision angular contact ball bearing and small clearance guide realized the high precision rotary of the electrode. Key factors like Guide clearance, liquid pressure, deep of the hole, the length of electrode hanging, spindle speed, discharge gap are analyzed in Ansys Workbench, which used to describe the process of machining expressed by influence and function curves. Moreover, the stress, strain and maximum deformation of the key parts of the spindle are also been analyzed, which realized the optimization of the structure and size of the partsThe experiments of array holes are carried out to verify the machining performance of the spindle. By Choosing the electrode range from ?0.3 mm to?0.8 mm in diameter, 400 mm tube brass in length, the 4x4 array holes, straight hole, step-hole and different diameter holes, are machined on the Inconel738 in the thickness of 3 mm, which verified the spindle ability of different diameter tubular electrode clamping, high pressure fluid inside supplying, high precision rotation and automatic compensation. |
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