Designing Undercuts in CNC Machined Parts
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In the world of precision CNC machining, designing parts for optimal manufacturability is paramount. One feature that often presents both a design challenge and a significant opportunity is the undercut. An undercut is a recessed feature, groove, or cavity in a part that is not directly accessible from a single machining direction. While they are essential for creating complex geometries like internal snapfit tabs, Oring grooves, or specific thread reliefs, they require careful planning to be produced efficiently and costeffectively.
The primary challenge with undercuts lies in tool access. Standard CNC cutting tools approach the workpiece from a vertical direction. When an undercut is required, specialized tools, such as lollipop cutters (undercut end mills) or Tslot cutters, become necessary. These tools have a cutting profile that allows them to reach beneath an overhanging feature. However, their use introduces complexities: they are often less rigid than standard end mills, which can lead to tool deflection, reduced cutting speeds, and potential vibration, affecting the final surface finish and dimensional accuracy.
Therefore, successful undercut design hinges on collaboration between the designer and the manufacturing engineer. Here are key considerations:
1. Accessibility and Tool Selection: Ensure there is sufficient clearance for the shank of the undercut tool to enter the cavity without colliding with other part features. The depth and width of the undercut are limited by the dimensions of available standard tools.
2. Corner Radii: Always design internal corners of an undercut with a radius, never a sharp 90degree angle. This radius must be equal to or larger than the radius of the cutting tool to prevent tool stress and breakage.
3. Minimizing Depth: Design the undercut to be as shallow as possible. Deeper undercuts require longer tools, which are more prone to deflection, leading to higher costs and potential quality issues.
CNC machining 4. Considering Alternatives: Before committing to an undercut, evaluate if the part's function can be achieved with an alternative design. Could a twopart assembly eliminate the need for the undercut? Sometimes, a simple design change can dramatically improve manufacturability.
At our factory, we specialize in navigating these complexities. Our expertise in designing and machining parts with undercuts ensures that your components are not only functional but also optimized for costeffective batch production. We leverage advanced tooling and proven machining strategies to produce highquality undercuts with precision and repeatability.
By understanding the principles of undercut design and partnering with an experienced manufacturer, you can unlock greater design freedom. Wellexecuted undercuts enhance part functionality, reduce assembly steps, and lead to more robust and innovative final products. For your next project requiring complex geometries, trust our team to deliver machining excellence that drives your business forward.