The Impact of Inside Corner Radii on Machining Efficiency
Design for Manufacturability (DFM) is essential in creating parts that are efficient and cost-effective to produce. One critical aspect of DFM in CNC machining is the radius of inside corners. Small radii, while often necessary for functionality or aesthetics, can drastically increase machining time and cost compared to larger radii.
Why Inside Corner Radii Matter
CNC machining relies on rotational tools, which means sharp internal corners are impossible, and inside corners must have a radius. Smaller radii require smaller cutting tools, leading to:
Increased Machining Time: More tool passes are needed to achieve the desired geometry.
Tool Wear and Breakage: Smaller tools are more prone to wear and may need replacement mid-job.
Higher Costs: Slower production cycles and frequent tool changes increase expenses.
Case Study: Optimizing a CNC-Machined Part
Small Radius (0.032") vs Larger Radius (0.125")
Tool Diameter Used: 0.0625" (1/16) vs 0.25" (1/4)
Feed Rate: 8 in/min vs 30 in/min
Number of Passes: 10 vs 3
Initial Design
Feature: 8 inside corners
Corner Radius: 0.032"
Machining Time: 40 minutes
Tool Changes: 2 per part - Rough, Semi-Finish, and Finish
Optimized Design
Feature: 8 inside corners
Corner Radius: 0.125"
Machining Time: 20 minutes
Tool Changes: 0 per part- Rough and Finish with Same Tool
Result
The optimized design reduced machining time by 75%, cut tooling costs, and shortened delivery timelines, saving approximately $120 per part in production costs.
Cost Implications
Reducing corner radii can have a ripple effect on costs:
Machine Time: A 75% increase in machining time can escalate labor and operational costs.
Tool Replacement: Smaller tools wear out faster, increasing tooling costs.
Production Delays: Slower cycle times can push back delivery schedules.
Design Recommendations
1. Use Larger Corner Radii
Increase corner radii wherever possible. For most applications, a radius of 0.125" or larger is ideal for reducing machining time while maintaining functionality.
2. Collaborate with CNC Partners
Involve your manufacturing team early in the design process to align on achievable tolerances and radii that balance form and function.
3. Limit Small Radii
Restrict small radii to critical areas of the design where they are functionally necessary.
Conclusion
Small adjustments to inside corner radii can lead to significant time and cost savings in CNC machining. Larger radii reduce tool wear, minimize machining time, and enhance overall efficiency. Incorporating these DFM principles ensures parts are not only functional but also economically viable to produce.