The PTJ profile cnc machining center has a long stroke and a large load-bearing structure. Therefore, compared with general machine tools, the PTJ profile machine is heavier, and the lighter machine tools (such as the PIA series) have about 8 tons. Longmen series) has about 50 tons. Under the influence of gravity, such a weight causes a large deformation of the bed. In order to resist the influence caused by such deformation, there are two kinds of methods: the first one is high stiffness bearing structure; the second one is the corresponding deformation compensation method. This article mainly describes a method of the second kind, how PTJ can correct the influence of gravity deformation through the processing of the working table (milled surface) to ensure the machining accuracy of the machine tool.
Taking the PTJ profile machining center PYC machining center as an example, when the Y-axis stroke is the maximum, the deformation of the nose of the nose affected by gravity is shown in Figure 1, the red area indicates the maximum deformation, and its value is 14.6 wire, blue area It indicates the minimum deformation, and its value is 12 filaments. Since the main axis is located at the center, we use the average deformation index, which is 13.3 filaments.
Assuming that during the machining process, the spindle will run the entire Y-axis travel, only considering the action of gravity, we analyze the average deformation of the machined processing surface along the Y-axis travel, and obtain the results shown in Figure 2.
From the above figure, we can see that the shape of the processing surface changes into a curve. When moving along the Y axis, the deformation of the processing surface is the smallest when the stroke is 160mm. When the stroke is 580mm, the deformation of the processed surface is the largest. According to the results, we can grind the work surface accordingly to overcome the machining error caused by the deformation caused by gravity.
We can effectively improve the accuracy by polishing the worktable surface. In the future, we will polish the curved surface, or design a structure that linearly deforms the machining surface of the machine head, and further improve the accuracy of china cnc machine tools.