A Designer’s Guide to CNC Machining-Friendly Parts

Designing parts for CNC machining requires a thoughtful approach to ensure your designs are not only functional but also optimised for efficient manufacturing. By understanding the capabilities and limitations of CNC machines, you can minimise costs, reduce production time, and achieve better results.

Here’s how to create machining-friendly parts that make the manufacturing process smoother and more cost-effective.

Simplify Geometries

Complex geometries may look impressive, but they can dramatically increase machining costs and time. Features like intricate curves, undercuts, or unnecessary decorative elements often require advanced multi-axis setups or specialised tools.

Tips

• Opt for simple shapes and avoid undercuts unless absolutely necessary.
• Use flat surfaces where possible to reduce the need for sculpted surfacing.

Optimise Internal Features

Sharp internal corners and deep cavities are challenging to machine with standard cutting tools. These features often require smaller tools and slower machining speeds, driving up production costs.

Tips

• Add fillets to internal corners with a radius matching standard cutter sizes (e.g., ≥3mm).
• Limit the depth of cavities to ensure easy tool access and maintain stability.

Minimise Setup Changes

Every time a part needs to be repositioned during machining, it adds to production time and increases the likelihood of alignment errors.

Tips

• Consolidate critical features on fewer faces of the part.
• Design parts to be machinable in two or three setups, avoiding the need to flip or rotate multiple times.

Standardise Holes and Threads

Non-standard hole sizes and thread specifications necessitate additional tooling and setup changes. This can significantly increase machining times.

Tips

• Use common hole diameters such as 3mm, 6mm, or 10mm.
• Stick to standard thread sizes like M3, M6, M8, or M10.

Balance Tolerances with Functionality

Applying tight tolerances across your entire design may seem like a good idea, but it can substantially raise machining costs. Tolerances should be specified based on the functional requirements of each feature.

Tips

• Reserve tight tolerances (±0.05mm) for critical dimensions.
• Use general tolerances (±0.1mm) for non-critical features.

Choose the Right Material

Material selection plays a vital role in both machinability and part performance. Some materials, while offering excellent properties, may be difficult or costly to machine.

Tips

• For metals, consider aluminium for its machinability and strength-to-weight ratio.
• For plastics, use materials like ABS or POM for easier machining and stability.

Collaborate with Your Machining Partner Early

A CNC machining partner, such as Prototype Projects, can offer valuable insights into optimising your designs. Involving them early in the design process ensures that your parts are manufacturable and cost-efficient.

Tips

• Share your design specifications and seek feedback on potential improvements.
• Discuss alternative materials, tooling, or setups to enhance efficiency.

Conclusion

Designing for CNC machining doesn’t have to be complex. By applying these principles, you can streamline the manufacturing process, reduce costs, and create high-quality parts that perform as intended.

We’re here to assist you in optimising your designs for CNC machining—contact us today to learn more!

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