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| Fig. 1 shows elevation of the entrance guide affects the sectional curvature. Fig. 2 shows an Edge Bent Down Model. |
Figure 1 illustrates the relationship between the elevation of the entrance guide and the sectional curvature before and after the first pass. In the top drawing, the entrance guide is too high. The metal may curve up after coming out of the first pass. In the bottom drawing, the entrance guide is too low, which could cause the metal to curve down after coming out of the first pass. When the entrance guide is set at the correct elevation, as shown in the middle drawing, no additional elongation occurs at the edge section, and the metal will be flat out of the first pass, without bow or twist.
A calculation method is available to estimate the best elevation of the entrance guide. This method is based on both the bending corner
AD and the side edge BC having the same traveling distance from the entrance guide to the first pass—in other words, AD and BC are the same length (see Figure 2).
