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Impellers Forming Accuracy
Aug 15, 2017

The balance hole (return port) is mainly to balance the axial force generated by the Impellers operation.To reduce the wear of the bearing end and the wear of the thrust plate when the Impellers rotates the liquid filled in the Impellers under the action of centrifugal force, The center is thrown around the Impellers along the flow path between the blades, and the pressure and velocity are increased simultaneously due to the action of the blade, resulting in a forward axial force. The Impellers is perforated to reduce the axial Force on the protection of bearings, thrust plate and control pump pressure.

The degree of reduction of the axial force depends on the number of pump holes and the size of the aperture, it is worth noting that the seal ring and the balance hole is complementary. The disadvantage of using this balanced approach is the efficiency of the loss (balance hole leakage is generally designed to flow 2% to 5%).

In addition, the leakage flow through the balance hole and the main flow into the Impellers impact, destruction of the normal flow state, will reduce the anti-cavitation performance.

At non-rated flow, the flow state changes. In the case of small flow, the pressure in the central part of the Impellers inlet is lower than the pressure on the outer periphery due to the effect of the pre-rotation. The leakage of the balance hole increases, and the pressure of the lower chamber of the seal ring is very low despite the increase of the head, small. When the flow rate is large, the axial force becomes smaller due to the decrease of the head.

The results show that the total area of the balance hole is 5-8 times of the gap area of the mouthpiece, and good performance can be obtained.

The overall Impellers blade profile is complex, the machining space is limited, the machining precision is high, the dynamic performance is good, and it has become one of the difficulties in the field of machinery manufacturing. At present, CNC milling, precision casting in the overall Impellers processing to get more applications. However, the CNC milling of difficult cutting materials, small channel leaves for processing, due to rigid rigidity of the tool is difficult to process; precision casting production process is complex, difficult technical, high scrap rate, only for castable alloy. EDM processing using the instantaneous high temperature generated by the discharge, the workpiece will be relative to the electrode surface melting, and gradually erosion of materials, to achieve the purpose of processing. Therefore, the EDM in the no cutting force, not subject to the hardness of the workpiece has other processing methods can not match the advantages.

EDM The overall Impellers used in the electrode can be designed into the form of the form and the overall form, the electrode form directly affects the accuracy of the parts being machined. Split electrode machining is easy to form a lap step on the blade surface, so that the blade profile produces a profile error, which affects the overall Impellers forming accuracy. The whole electrode is designed according to the structural characteristics of the whole Impellers. Two kinds of machining schemes are discussed for the different parts of the workpiece and the electrode. In order to avoid the electrode processing The occurrence of the interference problem, the electrode movement was simulated, and the interference check; the final manufacturing process of the electrode was studied.