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图1所示为柴油机灯罩,共形状复杂,口部转角半径小,壁部在轴向是弧形,底部成尖角,整个零件要求轮廓清晰。如完全采用直接拉深的方法来完成很困难。因此,我们采用拉深制作毛坯(见图2),然后用全形整形达到要求。要用全形整形,就要求凸凹模的形状准确。而这样复杂的形状用机械加工的方法使其凸凹模形状完全吻合是很不容易的,即使能达到目的,其成本也是很高的。故我们采用铋锡合金浇铸法制造整形模,具体步骤如下。
Figure 1 shows the diesel lampshade, a total of complex shape, mouth corner radius is small, the wall is arcuate in the axial direction, the bottom into a sharp angle, the entire part requires a clear outline. Such as the complete use of direct drawing method to complete very difficult. Therefore, we use the drawing of the blank (see Figure 2), and then use the whole shape to meet the requirements. To use a full plastic, it requires the shape of punch and die accurate. However, it is not easy for such a complicated shape to be mechanically machined to completely match the shape of the punch and die, and the cost is very high even if the purpose is achieved. Therefore, we use bismuth-tin alloy casting method to create plastic mold, the specific steps are as follows.