In the machining of three-axis CNC machine tools, regular bevels and curved surfaces can be processed by interpolation, but the accuracy and efficiency are not high. For some special curved surfaces, multi-axis simultaneous machining is usually required. Multi-axis machining has many advantages over three-axis machining, such as expanding the machining range and improving machining accuracy and efficiency. At present, multi-axis surface machining is generally programmed by various CAM software. MasterCAM is one of them. It provides curves (Multiaxis→Curve5ax), drilling (Multiaxis→Drill5ax), and pulling angles (Multiaxis→Swarf5ax). Multi-axis machining methods such as surface streamline (Multi-axis→Msurf5ax), multi-surface (Multiaxis→Flow5ax), and rotary four-axis (Multiaxis→Rotary4ax). Especially in multi-surface machining, MasterCAM has reached a practical stage: Mas-terCAM can integrate CAD modeling and CAM numerical control programming into a system environment, complete part modeling, tool path generation, machining simulation, NC program Generate and communicate with the CNC machine to complete the data transfer and finally complete the machining of the parts.
First, the question is raised
Impellers are widely used in many industries today. Since the impeller is a power component, its forming technology often affects the performance of the designed product. In addition, all the blades are relatively thin, and are easily deformed during processing, resulting in a large error in the final blade cross-sectional shape and the original design.
The surface characteristics of the impeller are very difficult, such as the use of ordinary three-axis CNC machining methods. Not only the number of clamping times is high, but also there is interference at the top when machining the bottom of the blade. Therefore, multi-axis CNC machine tools are often required to be processed. By adopting the MasterCAM model and using the curved multi-axis machining method to generate the path of the tool, the tool axis direction can be freely controlled according to the surface characteristics, so the actual machining angle and cutting conditions of the tool are improved, and the blade and the blade root can be simultaneously loaded at one time. The processing is carried out, and at the same time, the deformation of the blade after processing is small, and the surface smoothness of the blade is high, thereby improving the processing quality and efficiency of the impeller.
Second, part modeling and parts processing technology analysis
Analyze the structure and characteristics of the part, determine the CAD modeling method, and generate the part model according to the part drawing in the MasterCAM drawing area: the part is a rotating part, the rotation function is used to construct the base body, the first curve and the second curve are drawn, and the scanning surface is generated to construct the blade. The surrounding blades have the same structure, and the remaining blades are generated by the rotary copy function. The vane groove contains the left and right sides of the blade, the inclined curve and the bottom surface.
From the structural analysis of the impeller, the blade body face is divided into complex spatial curved surfaces, and the curvature and torsion changes of each part are large, and it is an important component of the power and the like, so the quality performance of the impeller should be ensured in the manufacturing process. The processing quality of the profile directly affects its performance and may also affect the overall performance. The material of the blade requires a high mass-strength ratio, which is difficult to cut during processing, has large cutting resistance, and causes large deformation. Due to its cross-sectional shape, the ability to resist deformation in the direction of the basin and the back of the blade is also different, and the edge at the edge of the row is thinner, and the deformation during processing is complicated, which places high demands on the numerical control processing.
The manufacturing process of the impeller is roughly as follows: determining the basic parameters of the impeller → making the part blank → blank flaw detection → CAM modeling and generating the program → impeller processing → inspection.
Third, the impeller processing example
The basic parameters of the impeller are: the diameter of the impeller is 425.45mm, the diameter of the impeller is 110mm, the height is 106mm, and the blades are evenly distributed in 12 places. The ideal processing scheme for the five-axis linkage milling blade surface is as follows.
(1) Remove the residual material, and the cutter spirals along the axis to remove the residual material.
(2) Milling the blade, the tool spirals along the axis, from one end to the other.
(3) Remove the residual angle, finish milling the bottom surface and the blade to ensure accuracy and surface finish.
(4) When milling the transition surface of the blade root, ensure that the bosses at both ends of the blade are not damaged.
In the CAM menu, click "ToolPaths" → "Job Setup", set the impeller blank, select "ToolPaths" → "Multiaxis" → "Flow5ax", the system displays the dialog box shown in Figure 8. Select "5Aaxis" in the "Output Format" option, select "Surfaces" in the "Cut Pattern" option, and the "Tool Axis Control" option. Select "Pattern Surfaces" and select "Comp to Surfaces" from the "Cut Surfaces" option. The above settings indicate that the path of the generated tool is a five-axis machining tool path, the area of ​​the tool path is defined by the selected surface, the tool axis coincides with the surface normal selected in the cutting mode, and the system projects the tool position to the selected cut. On the surface, compensate the tool vector to prevent overcutting.
For blade milling, a path similar to a spiral can be used. The tool rotates about the axis relative to the blade while moving linearly along the axis.
With this path of the cutter, the deformation of the blade is small, the quality is reliable, and the blade back and the blade are uniformly distributed, and the balance is uniform, which reduces the workload of subsequent grinding and polishing processes, and can obviously improve the production efficiency of the blade. .
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