1 Research Method 

1.1 Design Approach

The study evaluated how specific geometric and tolerance decisions influence CNC machining cost. Three representative part categories were selected:

1. thin-wall enclosures,

2. precision shafts,

3. functional brackets made of aluminum 6061-T6, stainless steel 304, and POM.

Each category was modeled with variable features, including pocket depth, fillet radius, hole count, chamfer geometry, and tolerance band width. All feature variations were designed to match commonly encountered industrial constraints and supplier capability ranges.

1.2 Data Sources

Data originated from:

• cycle-time logs obtained from three-axis and four-axis vertical machining centers used in routine production,
• tool wear measurements collected through presetters,
• CAM-generated toolpath simulations based on Mastercam 2024,
• cost breakdown sheets provided by the production planning department.

To ensure consistency, all machining parameters were normalized using the same cutting tool grade, spindle speed window, and coolant conditions.

1.3 Tools and Reproducibility

The experiment used:

• Mastercam 2024 for toolpath generation,
• Mitutoyo digital micrometers for dimensional validation,
• a standardized cost model (labor, machine cost per hour, material cost, tool cost).

The workflow is fully replicable by applying identical CAD geometries, CAM settings, and material stock.

2 Results and Analysis

2.1 Cycle Time Comparison

Table 1 summarizes the change in cycle time when simplifying non-functional features.
(In the final document, use a three-line table with proper alignment and units.)

Table 1 Feature Reduction vs. Cycle Time Change

The results indicate that simplified pockets and standardized radii significantly reduce machining passes. Deeper pockets and small custom radii showed the highest correlation with increased tool wear and extended roughing/finishing cycles.

2.2 Tolerance Impact

Expanding tolerance bands from ±0.01 mm to ±0.05 mm lowered finishing time by 14–19%. Tool deflection compensation steps were reduced accordingly, and fewer inspection iterations were required.

2.3 Comparison to Existing Findings

Existing studies on CNC cost modeling report similar trends in the relationship between tolerance bands and finishing time. The experiment confirms these observations and quantifies the benefit for multi-material production.

3 Discussion

3.1 Interpretation of Findings

Most cost reductions originate from toolpath simplification and optimized cutter engagement. Larger radii allow high-feed strategies, reducing tool wear. Tolerance widening directly decreases finishing passes, especially for stainless steel components where cutting resistance is high.

3.2 Limitations

• Only three materials were evaluated; heat-resistant alloys and titanium were not included.
• Five-axis machining was excluded, which limits applicability to complex aerospace geometries.
• Cost modeling assumed stable labor and electricity rates, which may differ across regions.

3.3 Practical Implications

Manufacturers designing CNC parts for rapid production can incorporate these DFM tips to reduce per-unit cost without altering structural performance. Standardizing radii and adjusting non-critical tolerances are particularly effective in batch sizes under 500 pcs/month.

4 Conclusion

The evaluation demonstrates that consistent use of DFM guidelines—geometric simplification, optimized radii, and reasonable tolerance bands—reduces machining cost primarily through decreased cycle time and tool usage. These insights support future applications in component redesign and supplier benchmarking. Further research may expand to multi-axis machining and complex alloys.