终极数控加工指南

• 机械因素： 旨在承受重载、磨损或其他外力的零件需要由能够承受这些力的材料制成。确定零件最理想或最必要的属性（例如柔韧性、抗冲击性、拉伸或压缩强度）可以帮助团队确定最适合的材料。

• 化妆品注意事项： 虽然美学对于某些部件来说可能是次要的，但对于许多消费品来说并非如此。在颜色、透明度或表面光洁度方面，某些部件或应用可能需要具有特定外观选项的材料。

• 公差： 在制造过程中，预计零件之间会存在一定程度的变化，尺寸公差是指可行零件必须落入的可接受变化范围。更严格的公差更费力且重复实现成本更高，但根据组件的使用方式可能是必要的。

CNC 加工设计

设计一个能按预期执行的高质量零件只是挑战的一半。您还必须能够以高效且具有成本效益的方式加工零件。可制造性设计 (DFM) 是一种流程框架，有助于将零件的制造方式与零件设计相结合。 DFM 对制造至关重要，影响从生产时间表和成本到运营效率和零件本身质量的方方面面。 CNC 加工最常见的设计考虑因素包括：

财大气粗：

深或窄的口袋和槽等特征需要更长的工具才能正确加工。然而，较长的切削刀具更容易断裂，并且由于加工振动或颤振通常不太精确。深层特征通常还需要多次切割才能正确加工，这会增加加工时间和生产成本——尤其是因为可能需要更小的工具来完成精加工道次。如果必须加工槽或深型腔，目标是尽可能减小特征深度或增加型腔横截面积。凹槽或槽的深度不应超过所需最小刀具直径的 3 倍。

狭窄区域：

狭窄的特征限制了可行切削工具的尺寸。这可能会给制造商带来挑战，因为长而小直径的工具很容易出现颤动和破损。与深层特征一样，狭窄区域应不小于最小切削刀具直径的 3 倍。将这些特征的深度减至最小允许您使用更短、更大直径的切削工具，这有助于减少机器颤振。

尖锐的内角：

CNC 立铣刀是圆形的，因此很难加工尖锐的内角，因为钻头会留下圆角半径。虽然有加工尖锐内角的方法，但这些工艺往往成本高昂。一般来说，加工零件应避免尖锐的内角。内角半径也应大于预期切削刀具的半径。通过将内半径设计为大于刀具，机器可以在壁之间形成平滑的过渡。相比之下，与刀具尺寸相同的内半径会迫使机器突然改变方向，从而导致光洁度降低。

无法访问的功能：

诸如沉头孔之类的功能——那些在另一个口袋中打开或带有负草案的口袋——可能对生产团队构成重大挑战。这些设计特征需要更多的时间来加工，因为允许切削工具进入是多么困难。确保切削工具可以自由访问零件的所有特征而不会被任何其他特征阻挡，这一点至关重要。

外圆角：

外圆角，或沿凹槽、凸台、槽和其他特征顶部边缘的圆角，需要由精确加工设置支持的定制切削工具——这种配对很快就会变得昂贵。对外边缘进行斜切或倒角可以帮助避免这些成本。

壁厚：

薄壁会给金属和塑料部件带来类似的问题，应尽可能避免。例如，薄金属壁更容易产生颤振，这会对零件的精度及其表面光洁度产生负面影响。薄壁塑料部件也更容易翘曲或软化。金属件的最小壁厚应为 0.03” (0.762mm) 和塑料件的 0.06” (1.524mm)。

平底孔：

平底孔不仅难以加工，而且往往会给后续操作带来困难。一般来说，产品团队应避免使用平底盲孔，而应使用标准麻花钻，后者会产生锥形底部的孔。

螺纹零件：

在加工内螺纹或外螺纹时，有几个不同的设计考虑因素。

对于内螺纹：

• 在内螺纹末端包括一个埋头孔。
• 尽可能减少线程数。大部分零件的压力实际上都落在前三个线程上，因此增加数量
• 线程数会产生递减收益。
• 使用标准形式和尺寸。
• 选择粗螺纹以降低成本。

对于外螺纹：

• 在所有螺钉设计中都包含倒角。
• 避免在大直径区域的肩部附近终止。
• 车削外螺纹应有后槽。
• 除非零件特别需要高螺纹强度，否则请使用较短的外螺纹。

钻出入口：

如果工件的表面不垂直于钻头的轴线，则钻头在与材料接触时会漂移。为了最大限度地减少不均匀的出口毛刺并简化去毛刺过程，请确保孔特征具有垂直于钻孔轴线的起始面和终止面。

降低成本的清单

1。保持零件简单
具有复杂设计或制造工艺的零件可能会产生许多下游影响。复杂性会增加加工时间和成本，引入错误机会，并使最终用户难以了解组件或零件的确切用途。将哪些特性和设计特征对零件的生存能力至关重要，而哪些是理想但非关键的，有助于消除零件设计和加工操作中不必要的复杂性。

2。设计时要考虑工具几何形状和设置方向

虽然大多数 CNC 加工工作需要多个设置方向，但您需要将每个零件的方向数量保持在最低限度。例如，如果您需要将工件翻转 3 次以使切削工具能够访问所有功能，这将增加成本，因为每次设置都需要重新安装零件，将机器归零以建立正确的轴，并运行一个新的 G 代码程序。 5 轴机器在这方面将更有能力，因为它们无需多次设置即可实现更多功能，但这取决于特定零件的几何形状。

减少所需切削工具的数量是另一种降低成本的方法。尽可能保持半径一致，以便加工内角所需的工具更少。同样，尽可能避免非常小的细节。较小的刀具不能切入工件的深度，也更容易断裂。 Typically, the smallest internal features that can be machined are 0.0394” (1mm), though holes can go as small as 0.0197” (0.5mm).

3。 Balance your tolerances

Choose your critical dimensions thoughtfully. Not every dimension requires inspection or is critical to the viability of the part, so focus your attention on those that are most essential. Determining how precise specific features need to be will allow you to adjust tolerances accordingly, reduce costs, and streamline the manufacturing process. Make sure that tolerances are still within machineable limits, adhere to given standards, and account for tolerance stacking.

Avoid over-dimensioning your part, as well. Unclear part drawings defeat the purpose of geometric dimensioning and tolerancing, which is to clarify and streamline communication. At Fast Radius, we recommend that you align drawing datums with the CNC coordinate system, as using consistent datum reference frames between machining and measurement systems is more likely to ensure parts are accurately located.

If possible, ensure all datums — points, surfaces, or axes used as references for measurement — reference the same setup. If a datum was machined in a previous setup, it becomes more difficult to hold tight tolerances after a setup change. Finally, be conscious about your datums. Choosing reference datums that are easy to measure from will ease manufacturing.

4。 Tailor inspection levels

Similar to balancing your tolerances, strategically applying the right inspection levels can help reduce costs and optimize the production processes. Typical inspection options may include a visual inspection of the part, checking part dimensions using hand tools, or a first article inspection (FAI) where the first manufactured part is checked to ensure all requirements have been met. More in-depth inspections require more time and labor, which increases manufacturing costs.

Increasing the number of parts that you inspect will also increase the cost of production, so it’s important that you select the right sampling plan to ensure confidence across the entire order. At Fast Radius, our default sampling rate is based on ANSI ASQ Z1.4 Level 2.

5. Design to common stock sizes

Designing parts to common stock sizes can help streamline the manufacturing process by minimizing the amount of material that needs to be removed from the workpiece. For example:if it’s acceptable for a part surface to retain its stock finish — that is, if the surface can be rougher than 125 μin Ra — and it does not need to be machined, you have an opportunity to reduce machining time without sacrificing part quality.

This is why knowing the common stock sizes for various materials is important. Metals, for instance, are typically available in a number of stock forms, including sheets, rods, bars, or tubes, which can be purchased according to dimensions like length, width, thickness, and diameter.

Keep in mind that metric sizes are more commonly available in Asia, while imperial sizes are more commonly available in the U.S.

6. Minimize deformation risk

Removing a large amount of material from a workpiece can cause the material to deform. This requires additional processing during machining to prevent deformation, leading to higher costs. Plastics have a higher risk of deformation than metals.

7. Choose your material carefully

The material you pick has a significant impact on the overall cost of your part. For example, metals are generally more expensive than plastics. Avoid over-engineering your parts and consider whether a specific grade or material certificate is required for the part. If a generic material can fulfill the part’s requirements or multiple materials can be accepted, select the less expensive material to keep costs low.

The machinability of the material should also be taken into consideration. Steels, for example, are typically more difficult to machine, which leads to higher costs because steel parts take longer to machine and increase wear-and-tear on cutting tools.

Common applications for CNC machining

Many industries rely on CNC machining processes to produce reliable, accurate parts that meet precise specifications and regulatory requirements, including the aerospace, automotive, medical device, electronics, and commercial parts manufacturing sectors.

Aerospace parts are held to high quality, testing, and regulatory standards in order to ensure proper function, fit, and safety. CNC machining is an excellent fit for creating plastic and metal parts with extremely tight tolerances that satisfy the aerospace manufacturer’s need for an incredible degree of precision and a range of highly specialized parts. The same is true for automotive components.

CNC machining can also be used to create a variety of medical devices, from implants to surgical implements to components for medical electronics.

Care and precision are critical when producing these sorts of devices and tools, as they are held to additional safety standards and requirements. Semiconductors and electronics components also have incredibly stringent precision requirements and tolerance standards, given their size and complexity. As a process, CNC machining has few material limitations, allowing it to be used with conductive materials like silicon. Many commercial parts — from aluminum castings and extrusions to steel and plastic parts — can also be machined.

Another common application for CNC machining is tooling, or the process of creating the various components, tools, machinery, and master patterns that will be used in production. Tooling is an integral part of every manufacturing and molding process and encompasses items like molds, jigs, and fixtures.

Starting your CNC machining project with Fast Radius

At Fast Radius, we make it simple and straightforward to get quality parts through our CNC machining service. To get started, visit os.fastraidus.com, upload your part designs, and you’ll receive instant DFM feedback. The site also allows you to manage designs and orders from a single, intuitive interface.

When you choose Fast Radius, you’re choosing to work with a seasoned group of experts. You’ll receive the full support of our team of engineers, customer success managers, account executives, and others across the business. We’ll also leverage options for domestic and international CNC machining to ensure that your project is carried out as efficiently as possible, without sacrificing quality.

Contact us today to experience the Fast Radius difference or click here to download our comprehensive guide as a PDF.

准备好使用 Fast Radius 制作零件了吗？