Error detection of typical complex parts in rapid investment casting

Through zgsccan three-dimensional laser scanner to complete the detection of point cloud data, the obtained point cloud data of complex parts are imported into the software Geomagic control, and then the STL format file of corresponding complex parts is imported for data processing and comparison, and finally the size deviation of the part is obtained. The specific steps are as follows: import the complex part 3D scanning digital model file and the original data part STL file, first take the original part as the reference; secondly use the “best fit alignment” of the software to overlap the scanning digital model and the original data part; finally select “3D comparison” to analyze the size deviation between the scanning data and the original data. Figure 4.4 shows the measurement results of dimension deviation of complex parts from different perspectives. The corresponding color in the right color code is the size deviation range of the part, in mm. At the same time, the area without obvious color differentiation can be created and annotated.

After comparing the three-dimensional data, the average positive dimension deviation of diffuser impeller is 0.4212mm, and the average negative dimension deviation is -0.7269mm.

From the comparison of different parts in figure (a), it can be seen that the size deviation of different parts of the impeller is different, the outer surface of the impeller is reduced, the inner surface is increased, and the average positive size deviation is 0.39885mm.

It can be seen from figure (b) that the dimensions of both sides of the outer blade show zero deviation, only the outer side of each blade and the joint between the two blades show negative deviation, with an average deviation of -0.6461mm, and the outer side of the upper blade shows negative deviation, with an average deviation of -0.7712mm.

It can be seen from figure (c) that the upper surface plane of the impeller shows a certain size reduction, and the average size deviation is -0.7230mm.

It can be seen from figure (d) that the inner side of the lower surface of the impeller shows zero deviation, while the outer side shows negative deviation, with an average deviation of -2.47135mm. Since this is the initial machining surface, the warping deformation in the initial machining process causes the size deviation, and the average deviation of the outer side of the side blade is -1.6918mm.

To sum up, it is not difficult to find that the increase of the inner dimension of the diffuser impeller is due to the reduction of the overall inward shrinkage of the parts under the effect of the heat radiation from the sintered area on the inner powder bed, and the larger temperature difference between the powder bed and the sintering area on the outer side leads to the overall radial shrinkage of the test piece, while the positive dimension deviation of the inner side is only half of the outer shrinkage.

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