Designing Effective Undercuts in CNC Machined Parts
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- Source:Axom
In the world of precision CNC machining, designing parts for manufacturability is paramount. One feature that often presents a significant challenge is the undercut. An undercut is a recessed feature that is not directly accessible from the primary tool approach directions. While they can complicate the machining process, welldesigned undercuts are essential for creating parts with interlocking components, snapfits, Oring grooves, or specific aesthetic profiles. Understanding how to design them effectively is key to balancing design intent with costefficient production.
Understanding the Challenges
Standard CNC milling tools, like end mills, cut from their sides and bottom. They cannot cut features where material is above or around the recess. Machining an undercut typically requires specialized tooling, such as Tslot cutters or lollipop (undercut) mills. These tools have a reduced shank diameter, making them more fragile and prone to deflection and breakage. This often results in slower machining speeds, increased tool wear, and higher costs. Furthermore, deep or complex undercuts can be impossible to machine without multiaxis setups or even secondary operations like EDM, drastically increasing lead time and price.
Best Practices for Effective Undercut Design
By incorporating design for manufacturability (DFM) principles, you can mitigate these challenges.
CNC machining
1. Optimize the Depth and Width: A common guideline is to keep the undercut depth to a maximum of 24 times the tool's neck diameter. Deeper undercuts require specialized, expensive tools and increase the risk of tool failure. Ensure the recess is wider than the tool's cutting diameter to allow for proper chip evacuation.
2. Specify Adequate Radii: Avoid sharp internal corners in the undercut. The radius of the undercut should match the radius of the standard undercutting tool available to your manufacturer. Designing with standard tooling sizes in mind prevents costly custom tool fabrication.
3. Provide Tool Access and Clearance: Ensure there is sufficient clearance for the tool shank to enter the cut without colliding with other part features. Designers should consider the entire tool path, not just the final geometry. Adding relief areas next to the undercut can significantly simplify machining.
4. Consider Alternative Designs: Before committing to a complex undercut, explore if the same functionality can be achieved with a different design. Could a twopart assembly replace a single part with a deep undercut? Often, a simple design change can eliminate the need for an undercut altogether, leading to a more robust and affordable part.
Partner with a Knowledgeable Manufacturer
Successfully integrating undercuts requires a collaborative partnership with your CNC machining provider. A seasoned manufacturer, like our factory, offers invaluable DFM feedback. We analyze your design to recommend optimal tooling strategies, suggest adjustments to improve strength and reduce cost, and leverage our expertise in 3, 4, and 5axis machining to produce your parts efficiently.
By thoughtfully designing undercuts and working closely with an experienced machining partner, you can unlock greater design possibilities for your components without compromising on quality, lead time, or budget. This approach ensures your highvolume production runs are smooth, reliable, and costeffective.