Operation planning and use of numerically controlled electrolysis impeller
Cathode Motion Trajectory Planning Cathode Motion Trajectory Calculation (1) The initial motion trajectory of the midpoint of the cathode front end is calculated to facilitate the subsequent EDM processing. In addition to removing the margin as much as possible in the electrolysis machining pre-channel, it is also necessary to make the leaf back and leaves The basin balance is uniform, so the center of the inter-leaf channel is used as the origin of the initial motion trajectory of the cathode. Cathode motion trajectory data conversion Because the tool cathode is fixed in the actual machining, the machining movement is completely driven by the machine tool table. Therefore, the coordinates (xi, yi) of the series of points on the cathode motion trajectory obtained above must be correspondingly The cathode swing angle i of the position is properly converted to obtain the translational displacement of the workpiece along the X and Y axes and the rotation angle around the Z axis under actual machining conditions, that is, a is converted into b.
In the processing motion trajectory data conversion diagram, O is the rotation center of the workpiece to be machined, D is the reference point on the tool cathode, A is the midpoint of the tool cathode front end, the subscript 0 is the position of the initial machining point, and the subscript i is the processing. The position of the point at the i-th moment. In a, the center of gravity of the blade is taken as the coordinate origin. When the workpiece is used as the reference object, the movement of the tool cathode can be regarded as moving on the one hand along the movement point of the front end midpoint A, and at the same time rotating around the point A; At the moment, the position of the point A relative to the machining initial position P0 is xAi, yAi, and the angle at which the cathode turns around the counterclockwise direction relative to the initial position is Ai, where O is the center of rotation, so the position of the rotary motion to the point O is not Have an impact.
Due to the design, the center of rotation of the workpiece coincides with the center of rotation of the machine table; therefore, the angle of the machine table rotating at the ith moment is -Ai relative to the initial position of the table, and the machine table is along the X at the ith time. The displacement of the Y-axis translation is obtained by the equation (2). The processing equipment shown in the realization of multi-axis linkage is a self-developed 5-axis linkage CNC electrolytic machining machine. It adopts a two-level numerical control system and consists of a general-purpose computer and five two-axis CNC units combined, each movement axis. They are controlled by an independent two-axis numerical control unit, and each axis is synchronized by the virtual real axis mapping method <6>, thereby completing the processing of the inter-leaf pre-channel.
The NC program must be programmed according to the characteristics of the electrolytic machining and control system to determine the various parameters in the NC program. The aforementioned blade profile treatment adopts a layer cutting method, and the blade profile is discretized into a plurality of segment curved surfaces by cutting a blade on a series of parallel straight lines x=xi on the R=Rk surface (on the R=Rm development surface) A number of segments of the curve), the forming motion trajectory is derived from these curved segments. During processing, the forming motion trajectory surface is processed according to the precision (profile profile) to be divided into several small curved surfaces whose upper and lower boundaries are parallel to the xGy plane. The linear approximation is nonlinear in each small segment, and the forming motion starts from this segment. During the transition from the position to the end position, the total forming motion is synthesized by the uniform motion of each axis. That is, in the process of processing this small curved surface, the required feed amount of each axis is completed at a constant speed.
The feed rate of electrolytic machining mainly refers to the moving speed of the cathode relative to the workpiece to be processed, which is the vector synthesis vfi of the translational speeds vXi, vYi of the table along the X and Y axes at each moment and the rotational speed i of the moment. Is a synthesis speed; the synthetic feed rate refers to the constant value of the synthetic feed rate during processing. According to the parameters Xi, Yi, i, Wi, F, the numerical control program can program the NC program of each drive shaft when machining the small surface curved surface Li. In the same way, a numerical control program for processing other small curved surfaces can be obtained, and a series of small-scale machining programs are connected in series to form a machining program for the entire curved surface.
The conclusion is shown in the processing of the overall impeller specimen with crown. The test and test processing site showed that the processed pre-channel between the impellers of the whole crown meets the process requirements and achieved the intended purpose. The realization of motion planning and multi-axis linkage is the basic content of CNC integrated electro-mechanical processing of integrated crown impeller technology. It will continue to deepen research in this area and make it engineering, and further expand the application field of CNC electroforming technology. The machining problem of the crowned impeller is of great significance.
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