We've spent so much time reminding designers that parts must be drafted to facilitate ejection from molds that it seems strange to talk about how to avoid having to draft parts, but it can sometimes be done when absolutely necessary. Keep in mind, however, that drafting is still the key to simplicity of design, ease of molding, and cost control. As we've said in previous Design Tips, when a surface is parallel to the direction of mold opening, it should be slightly tapered toward the mold; otherwise the mold surface will drag across the surface as the mold opens, damaging the surface. Drafting causes the part face to move away from the mold face as the part is ejected, preventing damage. The slight change in face angle usually makes no difference in either the functionality or appearance of the part. But what if it does?
我们经常提醒设计师，塑料零件必须有拔模角度，这样会使得模具顺利的工作，所以我们来谈怎样避免拔模角好像很奇怪，但在必要的情况下这确实是可以做到的。当然，我们必须时刻记住拔模角度是一个可以简化设计、简单模具、降低成本的关键特征。正如我们前面讲到的一样，当一个表面与模具张开方向平行时，产品应该朝模具开启方向有一个轻微的倾斜角度，否则产品表面可能会被模具刮伤。拔模角度可以使得零件表面偏离模具的表面，从而避免了这个问题。这个小小的角度经常不会对零件本身的功能和外观产生影响，但是，当他确实影响了改怎么办呢？

Probably the most common reason not to draft a surface is to make it fit with other parts of a finished product. Figure 1 is a bracket which bolts to a machine. If the mating face is drafted, the top facetilts at an angle that is unacceptable for this application .
大概不需要拔模角度的最经常用到的理由就是我们需要让这个表面和其它产品配合。图1是一个需要用螺栓固定在一个机器上的托架，如果配合的面有了拔模角，那么这个配合就将无法接受。

Fig. 1 /图1

For a specific requirement, like this one, Protomold can incorporate cam-driven side actions into a mold. These are typically used to create undercuts that could not be molded in a simple two-part mold. But, because cams move perpendicular to the direction of primary mold opening they can also be used to produce surfaces that are undrafted in relation to the A- and B-side mold halves.
对于有特殊要求的，就像这个零件，Protomold可以将凸轮机构引入要模具中。这被典型的用于不能在简单的凹凸模上做出的倒扣。因为凸轮朝着主模开启方向运动，所以也可以用来形成与与凹凸模相关的无拔模角平面。 

Imagine a part with a surface parallel to the direction of mold opening. Let's assume that we cannot draft the problem surface and must find some other way to protect it during ejection (see figure 1). Protomold would normally require draft on this face as shown in figure 2.
想像一个有着与模具开合方向平行平面的零件，让我们假设我们不能在这个问题（平行）面上有拔模角度，而且必须找到一些其它的途径来保护这个面在注塑过程中不被刮伤（图1）。一般情况下都会有如图2这样的拔模角度。 

Fig. 2 /图2

If the surface cannot be drafted, so as to move away from the mold as the part is ejected, an alternate solution is to have the mold move away from the surface. This is achieved using a side-action cam (pink face in figure 3).
如果这个面不能加拔模角度，那么必须要让模具朝远离（垂直）平面的方向运动。这就要用到一个边向凸轮机构（参见图3） 

Fig. 3 /图 3

In essence, a side action works like the moving wall in the Death Star trash compactor in Star Wars. As the A- and B-side mold halves open or close along the X-axis, the cam (or cams) move along the Y/Z axes. During ejection, the cam will withdraw leaving no mold wall next to the problem face to cause problems as the part is ejected.
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当凹凸模具在X方向上闭合，凸轮（机构）在Y或者Z方向上运动。 

Aside from undrafted faces and the obvious undercut features, there are several other applications for side actions. Raised lettering on a face parallel to the direction of mold opening presents a problem even if the face is drafted; side actions solve that problem (pink face in figure 4).  
除了倒扣和无拔模角平面以外，这种方式还有一些其它的应用。位于平行模具开合方向平面上凸起的文字可以代表这一类问题。（图4） 

Fig. 4 /图4

Similarly, texture on a low-draft face, which might not be reproducible in a straight-pull mold, can be produced in a mold with side actions.  
类似的，还有小拔模角度（小于参考拔模角度）面上的晒纹。 

There is additional cost for each side action, and there may be some flash between the side action face and the rest of the mold. Therefore they should be considered an option with tradeoffs, not a panacea for all undercuts or zero-draft faces.
这将会增加模具成本，而且可能会产生飞边。因此必须在各方面上找到平衡。 .

One more application is the production of decal recesses. These are shallow undercuts, but they can simplify the placement of decals and, if they fall in faces that are parallel to mold opening, are made possible using side actions. ProtoQuote® now points out areas that can be produced using side actions, giving users the option of redesigning their parts for standard straight-pull molds or using this more advanced capability.