What is the deformation of plastics in cutting during machining?
Because of the elastic resilience of plastics, this property must be reflected in the deformed plastic, while reflection occurs either in or after the cutting. It not only results in excessive wear and tear on the tool clearance surface, but also produces more frictional heat. This causes the tool temperature to be too high. When the tool is in high temperature for a long time, its hardness will decrease because of annealing. The elastic recovery after cutting shows why the bore diameter of drilling or tapping is smaller than the diameter of the cutter, and the size of the turning product will shrink when it is stored.
When the front angle of the tool is changed and the other factors remain unchanged, the vacuum deformation of the workpiece is removed. Cutting speed cutting is used in 190m/min, the cutting depth is 0.5mm, after the angle of cutting tool is 10 degrees. The dotted line in the figure represents the orientation of the material before cutting, and the solid line lattice indicates the displacement of the dotted line in the cutting, that is, the deformation of the material. As can be seen from the diagram, the deformation of the material in cutting is dependent on the rake angle of the tool. When the current angle is 40 degrees, (as in Figure), the material deformation at the top and bottom of the blade is a draft deformation, while the direction along the blade is compression deformation. The two kind of deformation in the workpiece will be transmitted to a considerable depth. At present, when the angle changes to 0 degrees, the deformation of the materials in some parts of the drawing has been alleviated, but the compressive deformation has increased. A rake angle of -20 degrees, (Figure C), along the edge of two straight upward deformation is compressive deformation, and the great
From this point of view, the general trend of material deformation in the process of gradual deformation of the front angle is that the dominant drafting deformation gradually prevails over the compressive deformation and increases continuously in quantity. What is more obvious is that the material under the blade is first raised, and gradually becomes depressed as the front angle becomes smaller. So long as the angle is different, even if other factors are the same, the size of workpiece will never be the same. In addition, in the cutting of the material being pressed, the friction on the back clearance of the tool is greater than that of the material being raised. Experiments show that if the cutting conditions change, the material deformation with the rake angle change remains, by drawing deformation gradually to compression deformation, but changes in the number and specific but not equal. The experiment also proves that the above phenomenon is accurate for any plastic cutting.
