Geometric dimensioning and tolerancing (GD&T) is a widely-adopted engineering language. Just like any language, however, it takes time and effort to learn and use properly.
几何尺寸和公差 （GD&T） 是一种广泛采用的工程语言。然而，就像任何语言一样，正确学习和使用都需要时间和精力。

For example, let抯 look at a manufacturer who practically lives by the ASME Y14.5-2009 GD&T standard. At this company, every new engineer must go through one week of Y14.5 training and then apply GD&T to all designs. However, with that level of commitment, the team members, including seasoned engineers, still make mistakes frequently due to lack of knowledge, oversights or fatigue梥imilar to those typos in an email that we抳e all made.
例如，让我们看看一家实际上遵循 ASME Y14.5-2009 GD&T 标准的制造商。在这家公司，每个新工程师都必须接受为期一周的Y14.5培训，然后将GD&T应用于所有设计。然而，在这种程度的承诺下，团队成员，包括经验丰富的工程师，仍然会因为缺乏知识、疏忽或疲劳而经常犯错棗类似于我们所有人在电子邮件中犯的那些错别字。

Fortunately, Microsoft Office provides a spelling and grammar check to flag typos for us. Wouldn抰 it be nice if an engineering design tool could help flag GD&T mistakes too? After all, just like other languages, GD&T is structured and has a well-defined set of rules and best practices.
幸运的是，Microsoft Office 提供了拼写和语法检查来为我们标记拼写错误。如果工程设计工具也可以帮助标记 GD&T 错误，那不是很好吗？毕竟，就像其他语言一样，GD&T 是结构化的，并且有一套定义明确的规则和最佳实践。

Well, this is where a real-time grammar verification such as the one in SOLIDWORKS MBD can assist.
这就是实时语法验证（例如 SOLIDWORKS MBD 中的验证）可以提供帮助的地方。

To start, note that this checking function only gives warnings. It doesn抰 stop a workflow, force us to correct an error or automatically fix the error. We still have the flexibility to ignore it after a careful review. Therefore, engineers still need to take the control and responsibility.
首先，请注意，此检查功能仅提供警告。它不会停止工作流，不会强制我们更正错误或自动修复错误。我们仍然可以灵活地在仔细审查后忽略它。因此，工程师仍然需要承担控制权和责任。

Figures 1 and 3 show where a flag can be raised:
图 1 和图 3 显示了可以升旗的位置：

1. In the graphics area, a feature control frame in error is turned in yellow.
   在图形区域中，错误的特征控制边框变为黄色。
2. On the DimXpert tree, the top node of this entire PMI scheme is prefixed with a warning sign and presented in red.
   在 DimXpert 树上，整个 PMI 方案的顶部节点以警告标志为前缀，并以红色显示。
3. The questionable feature node is prefixed with a warning sign.
   有问题的要素节点以警告标志为前缀。
4. The questionable GD&T node is prefixed with a warning sign and presented in red.
   有问题的 GD&T 节点以警告标志为前缀，并以红色显示。
5. A warning message explaining the root cause is displayed in a pop-up bubble when the mouse cursor is over the GD&T node.
   当鼠标光标位于 GD&T 节点上时，弹出气泡中会显示一条解释根本原因的警告消息。
6. The same warning message is displayed at the bottom of a GD&T definition dialog in Figure 3.
   在图 3 中，GD&T 定义对话框的底部显示相同的警告消息。

Figure 1. A GD&T error is flagged in both the graphic area and the tree nodes.
图 1.在图形区域和树节点中都标记了 GD&T 错误。

Now, you may wonder: What抯 wrong with this position tolerance? The warning message says, 揘o size tolerances defined for feature Boss5.?Aha! Because this position tolerance contains a maximum material condition (MMC) modifier   (M in a circle) to the diameter tolerance zone Φ.020in, it needs to know the boss feature抯 overall size tolerances to calculate its MMC.
现在，您可能想知道：这个位置公差有什么问题？警告消息显示，?#27809;有为特征 Boss5 定义尺寸公差?#12290;啊哈！由于此位置公差包含直径公差区 Φ.020in 的最大材料条件 （MMC） 修饰符  （圆圈中的 M），因此它需要知道凸台特征的整体尺寸公差才能计算其 MMC。

We can fix it easily either by adding the boss size tolerances as shown in Figure 2 or removing this MMC modifier. The former approach could save cost because it only requires the Φ.020in position tolerance at the MMC, which is Φ.810in, or the biggest boss. At the least material condition, Φ.790in, or the smallest boss, the position tolerance could be as loose as Φ.040in or Φ.010in + Φ.010in + Φ.020in. Therefore, if it meets the functional requirements, Figure 2 would be a more cost-effective recommendation.
我们可以通过添加如图 2 所示的凸台尺寸公差或移除此 MMC 修饰符来轻松修复它。前一种方法可以节省成本，因为它只需要 MMC 处的 Φ.020in 位置公差，即 Φ.810in，或最大的凸台。在最小材料条件 Φ.790 英寸或最小凸台下，位置公差可以像 Φ.040 英寸或 Φ.010 英寸 + Φ.010 英寸 + Φ.020 英寸一样松散。因此，如果它满足功能要求，图 2 将是一个更具成本效益的建议。

Figure 2. The added size tolerances for the boss feature corrected the feature control frame.
图 2.为 凸台 特征添加的尺寸公差更正了特征控制框架。

Following the same logic to loosen the tolerance requirements and cut cost, I applied the MMC at the datum features A and C in this feature control frame in Figure 2. The warning is now gone.
遵循相同的逻辑来放宽公差要求并降低成本，我在图 2 中这个特征控制框架中的基准特征 A 和 C 处应用 MMC。警告现已消失。

Can we apply the MMC to the datum feature B? Let抯 give it a try. Figure 3 shows the warning, 揂 material condition modifier applied to a feature that cannot have size tolerances.?Why? Because the datum feature B is a plane, not a feature of size. It can抰 have size tolerances or the MMC at all, so the MMC doesn抰 apply here and SOLIDWORKS MBD catches this error.
我们可以将 MMC 应用于基准特征 B 吗？让我们试一试。图 3 显示了警告，?#24212;用于不能具有尺寸公差的特征的材料状况修饰符。为什么？因为基准特征 B 是一个平面，而不是一个尺寸特征。它不能有尺寸公差或 MMC，因此 MMC 在此处不适用，SOLIDWORKS MBD 会捕获此错误。

Figure 3. A warning against an incorrect MMC modifier to a datum plane.
图 3.针对基准平面的 MMC 修饰符不正确的警告。

As we construct a feature control frame on the Geometric Tolerance dialog in Figure 3, let抯 pay attention to the warning messages at the bottom of this dialog as it guides us towards a more robust GD&T creation.
当我们在图 3 的 Geometric Tolerance 对话框中构建一个特征控制框架时，让我们注意此对话框底部的警告消息，因为它会指导我们进行更健壮的 GD&T 创建。

The above are just several quick illustrations of the grammar verifications against the MMC modifier. Now let抯 go through the key compartments in a feature control frame to review more examples.
以上只是针对 MMC 修饰符的语法验证的几个快速说明。现在，让我们浏览一下功能控制框架中的关键隔间，以回顾更多示例。

Symbols  符号

There are 14 GD&T symbols, and they are used for specific feature control types. For example, if we change the position tolerance symbol in Figure 2 to a flatness symbol, the grammar verification will give us a warning as shown in Figure 4, 揃oss5 is an invalid feature type for flatness,?because, obviously, it doesn抰 make sense to define how flat a cylinder is.
有14个GD&T符号，它们用于特定的特性控制类型。例如，如果我们将图 2 中的位置公差符号更改为平面度符号，语法验证将给出如图 4 所示的警告，揃oss5 是平面度的无效特征类型?#65292;因为显然，定义圆柱体的平面度没有意义。

Figure 4. An invalid flatness symbol applied to a cylinder.
图 4.应用于圆柱体的无效平面度符号。

The similar checking is conducted against other symbols. For instance, defining a circularity control symbol to the datum feature B (a flat plane) would be flagged.
针对其他交易品种进行类似的检查。例如，为基准特征 B （平面） 定义圆度控制符号将被标记。

Tolerances  公差

The next compartment is for tolerances. As we move along, we need to keep in mind not only the validity of an individual compartment, but also its relationships with other compartments. That is, whether this compartment definition makes sense in the context of the entire feature control frame.
下一个隔间用于公差。随着我们的前进，我们不仅需要记住单个区间的有效性，还需要记住它与其他区间的关系。也就是说，此区间定义在整个功能控制框架的上下文中是否有意义。

Here the grammar checking verifies whether a tolerance number or a tolerance zone is valid. For example, the tolerance needs to be a numeric value in the first place. There are several exceptions of letters such as the CZ in the ISO 1101:2012 standards, but for most cases, tolerances are numbers. Furthermore, the tolerance zone needs to be applicable to the corresponding feature control type. Figure 5 shows an invalid zone type specified for a cylindricity tolerance control. We can fix that by removing the diameter modifier Φ from this compartment. As a comparison, if we choose a concentricity control type, then the diameter tolerance zone modifier Φ will be needed in this tolerance compartment. Otherwise, the grammar check will throw out an error.
此处的语法检查验证容差数字或容差区是否有效。例如，容差首先需要为数值。字母有几个例外，例如 ISO 1101：2012 标准中的 CZ，但在大多数情况下，公差是数字。此外，公差带需要适用于相应的特征控制类型。图 5 显示了为圆柱度容差控制指定的无效区域类型。我们可以通过从这个隔间中删除直径修饰符 Φ 来解决这个问题。作为比较，如果我们选择同心度控制类型，那么在这个公差区间中将需要直径公差区修饰符 Φ。否则，语法检查将抛出错误。

Figure 5. An invalid tolerance zone type specified for a cylindricity tolerance.
图 5.为圆柱度容差指定的无效容差带类型。

Datum features  基准特征

Datum features are the foundation of GD&T, so there are very extensive checks in MBD against them. First of all, the datum feature needs to be called out before being referenced in a feature control frame. Otherwise, the GD&T dialog will remind us, 揇atum X has not been defined.?Of course, we can still proceed here and define the datum feature X later to fix the reference.
基准特征是 GD&T 的基础，因此 MBD 中对它们进行了非常广泛的检查。首先，在特征控制框中引用基准特征之前，需要先调用该特征。否则，GD&T 对话框将提醒我们，?#23578;未定义基准 X?#12290;当然，我们仍然可以继续在此处，稍后定义基准特征 X 以修复参考。

In addition, the control type symbol is checked against a datum feature. In Figure 6, although a runout tolerance is valid on this cylinder, it抯 invalid in the context of the datum feature A because a feature for a runout tolerance needs to be coaxial with the datum axis.
此外，对照基准特征检查控制类型符号。在图 6 中，尽管跳动公差在此圆柱体上有效，但在基准特征 A 的上下文中它是无效的，因为跳动公差的特征需要与基准轴同轴。

Figure 6. An invalid datum feature framework specified for a runout tolerance.
图 6.为跳动公差指定的无效基准特征框架。

Besides the manual GD&T definition, the datum features are also checked in the auto dimension scheme as shown in Figure 7. The secondary datum feature shouldn抰 be collinear with the primary datum feature. Otherwise, they would generate the same theoretical datum, the hole axis, which would be a duplicate.
除了手动 GD&T 定义外，基准特征也在自动尺寸方案中检查，如图 7 所示。次基准特征不应与主基准特征共线。否则，它们将生成相同的理论基准，即孔轴，这将是重复的。

Figure 7. An invalid secondary datum feature collinear with the primary one.
图 7.与主基准特征共线的无效次基准特征。

There are hundreds of rules built into SOLIDWORKS MBD. We can only show very few examples in this article. Please feel free to check out the product and discuss the grammar verifications in detail in the comment area below. To learn more about how the software can help you with your MBD implementations, please watch this video below and visit its product page.
SOLIDWORKS MBD 中内置了数百条规则。在本文中，我们只能展示极少数几个示例。请随时查看产品并在下面的评论区详细讨论语法验证。要了解有关该软件如何帮助您实施 MBD 的更多信息，请观看下面的视频并访问其产品页面。