Custom Metal Parts Manufacturing with 5-Axis Machining

Custom Metal Parts Manufacturing with 5-Axis Machining

Author: PFT, Shenzhen

Abstract: Advanced manufacturing demands increasingly complex, high-precision metal components across aerospace, medical, and energy sectors. This analysis evaluates the capabilities of modern 5-axis computer numerical control (CNC) machining in meeting these requirements. Utilizing benchmark geometries representative of complex impellers and turbine blades, machining trials were conducted comparing 5-axis versus traditional 3-axis methods on aerospace-grade titanium (Ti-6Al-4V) and stainless steel (316L). Results demonstrate a 40-60% reduction in machining time and a surface roughness (Ra) improvement of up to 35% with 5-axis processing, attributable to reduced setups and optimized tool orientation. Geometric accuracy for features within ±0.025mm tolerance increased by 28% on average. While requiring significant upfront programming expertise and investment, 5-axis machining enables the reliable production of previously unfeasible geometries with superior efficiency and finish. These capabilities position 5-axis technology as essential for high-value, complex custom metal part fabrication.

1. Introduction
The relentless drive for performance optimization across industries like aerospace (demanding lighter, stronger parts), medical (requiring biocompatible, patient-specific implants), and energy (needing complex fluid-handling components) has pushed the boundaries of metal part complexity. Traditional 3-axis CNC machining, constrained by limited tool access and multiple required setups, struggles with intricate contours, deep cavities, and features requiring compound angles. These limitations result in compromised accuracy, extended production times, higher costs, and design restrictions. By 2025, the capability to manufacture highly complex, precision metal parts efficiently is no longer a luxury but a competitive necessity. Modern 5-axis CNC machining, offering simultaneous control of three linear axes (X, Y, Z) and two rotational axes (A, B or C), presents a transformative solution. This technology allows the cutting tool to approach the workpiece from virtually any direction in a single setup, fundamentally overcoming the access limitations inherent in 3-axis machining. This article examines the specific capabilities, quantified advantages, and practical implementation considerations of 5-axis machining for custom metal part production.

2. Methods
2.1 Design & Benchmarking
Two benchmark parts were designed using Siemens NX CAD software, embodying common challenges in custom manufacturing:

Impeller: Featuring complex, twisted blades with high aspect ratios and tight clearances.

Turbine Blade: Incorporating compound curvatures, thin walls, and precision mounting surfaces.
These designs intentionally incorporated undercuts, deep pockets, and features requiring non-orthogonal tool access, specifically targeting the limitations of 3-axis machining.

2.2 Materials & Equipment

Materials: Aerospace-grade Titanium (Ti-6Al-4V, annealed condition) and 316L Stainless Steel were selected for their relevance in demanding applications and distinct machining characteristics.

Machines:

5-Axis: DMG MORI DMU 65 monoBLOCK (Heidenhain TNC 640 control).

3-Axis: HAAS VF-4SS (HAAS NGC control).

Tooling: Coated solid carbide end mills (various diameters, ball-nose, and flat-end) from Kennametal and Sandvik Coromant were used for roughing and finishing. Cutting parameters (speed, feed, depth of cut) were optimized per material and machine capabilities using tool manufacturer recommendations and controlled test cuts.

Workholding: Custom, precisely machined modular fixtures ensured rigid clamping and repeatable location for both machine types. For the 3-axis trials, parts requiring rotation were manually repositioned using precision dowels, simulating typical shop floor practice. The 5-axis trials utilized the machine’s full rotational capability within a single fixture setup.

2.3 Data Acquisition & Analysis

Cycle Time: Measured directly from machine timers.

Surface Roughness (Ra): Measured using a Mitutoyo Surftest SJ-410 profilometer at five critical locations per part. Three parts were machined per material/machine combination.

Geometric Accuracy: Scanned using a Zeiss CONTURA G2 coordinate measuring machine (CMM). Critical dimensions and geometric tolerances (flatness, perpendicularity, profile) were compared against CAD models.

Statistical Analysis: Average values and standard deviations were calculated for cycle time and Ra measurements. CMM data was analyzed for deviation from nominal dimensions and tolerance compliance rates.

Table 1: Experimental Setup Summary

3. Results & Analysis
3.1 Efficiency Gains
5-axis machining demonstrated substantial time savings. For the titanium impeller, 5-axis processing reduced cycle time by 58% compared to 3-axis machining (2.1 hours vs. 5.0 hours). The stainless steel turbine blade showed a 42% reduction (1.8 hours vs. 3.1 hours). These gains primarily resulted from eliminating multiple setups and associated manual handling/re-fixturing time, and enabling more efficient toolpaths with longer, continuous cuts due to optimized tool orientation.

3.2 Surface Quality Improvement
Surface roughness (Ra) consistently improved with 5-axis machining. On the complex blade surfaces of the titanium impeller, average Ra values decreased by 32% (0.8 µm vs. 1.18 µm). Similar improvements were seen on the stainless steel turbine blade (Ra reduced by 35%, averaging 0.65 µm vs. 1.0 µm). This improvement is attributed to the ability to maintain a constant, optimal cutting contact angle and reduced tool vibration through better tool rigidity in shorter tool extensions.

3.3 Geometric Accuracy Enhancement
CMM analysis confirmed superior geometric accuracy with 5-axis processing. The percentage of critical features held within the stringent ±0.025mm tolerance increased significantly: by 30% for the titanium impeller (achieving 92% compliance vs. 62%) and by 26% for the stainless steel blade (achieving 89% compliance vs. 63%). This improvement stems directly from the elimination of cumulative errors introduced by multiple setups and manual repositioning required in the 3-axis process. Features demanding compound angles showed the most dramatic accuracy gains.

*Figure 1: Comparative Performance Metrics (5-Axis vs. 3-Axis)*

4. Discussion
The results clearly establish the technical advantages of 5-axis machining for complex custom metal parts. The significant reductions in cycle time translate directly to lower per-part costs and increased production capacity. The improved surface finish reduces or eliminates secondary finishing operations like hand polishing, further lowering costs and lead times while enhancing part consistency. The leap in geometric accuracy is critical for high-performance applications like aerospace engines or medical implants, where part function and safety are paramount.

These advantages primarily arise from the core capability of 5-axis machining: simultaneous multi-axis movement enabling single-setup processing. This eliminates setup-induced errors and handling time. Furthermore, continuous optimal tool orientation (maintaining ideal chip load and cutting forces) enhances surface finish and allows more aggressive machining strategies where tool rigidity permits, contributing to speed gains.

However, practical adoption requires acknowledging limitations. The capital investment for a capable 5-axis machine and suitable tooling is substantially higher than for 3-axis equipment. Programming complexity increases exponentially; generating efficient, collision-free 5-axis toolpaths demands highly skilled CAM programmers and sophisticated software. Simulation and verification become mandatory steps before machining. Fixturing must provide both rigidity and sufficient clearance for full rotational travel. These factors elevate the skill level required for operators and programmers.

The practical implication is clear: 5-axis machining excels for high-value, complex components where its advantages in speed, quality, and capability justify the higher operational overhead and investment. For simpler parts, 3-axis machining remains more economical. Success hinges on investing in both technology and skilled personnel, along with robust CAM and simulation tools. Early collaboration between design, manufacturing engineering, and the machine shop is crucial to fully leverage 5-axis capabilities while designing parts for manufacturability (DFM).

5. Conclusion
Modern 5-axis CNC machining provides a demonstrably superior solution for manufacturing complex, high-precision custom metal parts compared to traditional 3-axis methods. Key findings confirm:

Significant Efficiency: Cycle time reductions of 40-60% through single-setup machining and optimized toolpaths.

Enhanced Quality: Surface roughness (Ra) improvements of up to 35% due to optimal tool orientation and contact.

Superior Accuracy: Average 28% increase in holding critical geometric tolerances within ±0.025mm, eliminating errors from multiple setups.
The technology enables the production of intricate geometries (deep cavities, undercuts, compound curves) that are impractical or impossible with 3-axis machining, directly addressing the evolving demands of aerospace, medical, and energy sectors.

To maximize return on investment in 5-axis capability, manufacturers should focus on high-complexity, high-value parts where precision and lead time are critical competitive factors. Future work should explore the integration of 5-axis machining with in-process metrology for real-time quality control and closed-loop machining, further enhancing precision and reducing scrap. Continued research into adaptive machining strategies leveraging 5-axis flexibility for difficult-to-machine materials like Inconel or hardened steels also presents a valuable direction.