How to Design Parts for CNC Machinability

In the competitive world of custom part manufacturing, designing for manufacturability (DFM) is not just a best practice—it's a critical factor in determining cost, lead time, and final quality. For companies seeking reliable, highprecision CNC machining services, understanding these fundamental principles is the first step toward a successful partnership and a superior product.


cnc machining center
1. Prioritize Internal Radii
A cornerstone of CNCfriendly design is the proper specification of internal corners. Cutting tools, primarily end mills and drills, are cylindrical and cannot produce sharp internal corners. Always design with a radius, and make it slightly larger than the intended tool's radius. This allows the tool to trace the pocket efficiently without unnecessary passes, slashing machining time and cost. A common radius size across your design also enables the use of a single tool, minimizing tool changes.

2. Optimize Cavity and Pocket Depths
Deep cavities with small tools are a significant challenge. The lengthtodiameter ratio of a tool impacts its stability; exceeding a ratio of 4:1 increases the risk of tool deflection, vibration, and breakage, leading to poor surface finish and dimensional inaccuracies. Whenever possible, limit pocket depths to four times the tool diameter. For deeper features, consider designing parts with multiple sections or exploring alternative manufacturing methods like casting for the base structure, with CNC for final precision.

3. Standardize Hole Sizes

cnc machining online
Holes are ubiquitous in machined parts. Designing them to standard drill bit sizes is a simple yet powerful way to reduce costs. Standard tools are readily available, while nonstandard sizes require expensive custom tools or slower machining processes like boring. Additionally, specify thread depths wisely—a depth of more than 1.5 times the hole diameter in steel (or 3x in aluminum) often provides no extra strength but adds significant machining time.

4. Minimize Thin Walls
Thin walls are fragile and prone to vibrating during machining, which results in poor surface finish and potential part failure. While modern machines can achieve very thin features, they require lighter cuts and more time, increasing costs. Design walls with a minimum thickness that aligns with the material's capabilities—for instance, 0.5 mm for metals like aluminum and 1.0 mm for plastics is a good starting point for most applications. A more robust design is inherently easier and faster to produce.



5. Simplify Setups and Reduce Complexity
Every time a part must be refixtured in the machine, it adds to the labor time and introduces a potential for error. Design parts that can be machined in as few setups as possible. Avoid features on five or six sides unless absolutely necessary. Furthermore, consider adding slight chamfers (instead of radii) on vertical edges; this can often be done with the same tool used for a primary operation, eliminating a separate deburring step.

By integrating these principles into your design phase, you directly contribute to a more efficient and costeffective manufacturing process. At our onestop CNC machining service, we combine advanced technology with deep engineering expertise. We are your ideal partner, ready to provide DFM feedback to refine your designs, ensuring you receive highquality, precision parts faster and at a competitive price, fueling your business growth.