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注塑成型设计有明确的规则：添加草案。没有底切。圆形边缘。清除分区线。均匀的墙壁，不太厚。但是学习高级塑料制造就像在矩阵中访问Morpheus的Dojo：一些规则可以弯曲。其他人可以被打破。但打破这些规则是昂贵的。
Sharp edges需要额外的加工费用和时间;室壁厚度变异可以留下难看的沉降量;虽然可能，但可能需要对模具的侧面动作，可以提高成本和循环时间。要了解原因，我们需要访问Dojo。
注塑模具
As covered in other articles here on Fictiv, basic injection molding consists of two mold halves coming together, plastic being heated and forced into the cavity between those two halves, and the mold halves separating to release the part from the mold. That last step is what makes undercuts in parts difficult to mold.
What is an undercut? Essentially, this is any surface of the part that can’t be seen by looking at it from the top or bottom. (In reality, the “pull direction”—the axis along which the mold opens and closes—is typically horizontal, but conceptually, it’s easier to think of it vertically.)
如果看下面的部分横截面，你可以看到大部分表面都是模具的顶部或下半部分的大部分表面，但沿右侧的小架子会导致部分粘在较低的位置半模。
In other types of casting, like lost wax or sand casting, the molds are disposable. In injection molding, however, the mold parts are designed to produce hundreds of thousands of pieces. Therefore, each mold part needs to easily separate from the mold when it opens, and these undercuts present a special design for manufacture challenge.
If your design requires an undercut, is that a rule that can be bent? Yes, and that’s where side actions enter the picture.
底切的工具中的侧面行动
因为底切不是一个新问题，因此有进取心的工程师已经开发了解决方案。而不是仅仅将刀具的两个半成部分聚集在一起，从侧面移动，允许形成的表面，否则允许形成的表面，同时仍然允许部分允许部分从模具容易地释放。
如果你看一看,更有意义at the way the part above would be molded. In order to create that shelf, the bottom half of the mold would have a side action that would move vertically with the bottom mold piece and would also move horizontally, as part of the molding cycle. When the mold is closed, this side action forms part of the mold cavity, but as the mold opens, it slides away from the part, allowing the part to release easily from the mold.
虽然巧妙并能够产生真正的令人惊叹的零件，但否则无法模塑，侧面行动确实具有缺点。设计具有侧面动作的模具工具需要额外的工具工程，处理所有模制品中存在的高力和加热和冷却循环，以及附加的移动部件。这些部件还需要额外的加工时间来生产和组装模具工具。所有这些都显着提高了需要副作用的模具的成本。
您如何讲述您的部件是否需要侧面行动？对于经验，经常用注射成型处理的工程师可以快速分析设计。
Alternatives to Side Actions: Avoiding Undercuts
The most common solution to undercuts, and the resulting increase in tooling cost and lead time from side actions, is to cut away material below the undercut. In the picture below, you can see how a groove in the side of a molded piece will allow the snap to be formed without any undercuts. In the image below that, you can see how a hinge barrel can be formed without requiring side actions.
Another possible solution is to section your parts. Instead of molding parts as a single unit with multiple side actions, consider having the design molded as several smaller parts and ultrasonically welded together after molding. While this can also increase the per-unit and tooling cost, it’s often worth exploring and quoting this as a manufacturing option, especially when you have either very complex geometry, as with the golf training tool below, or when your parts need to enclose a volume, as with Apple ear pods.
Undercuts in Your Design
With more than a century of refinements in injection molding technology, rules of design for molding are rarely absolute. However, veering from the standard DFM rules does increase the cost of the tooling and of each unit, and side actions to produce undercuts on parts are no exception.
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