High-Precision Long Shaft with Flange: A Case Study in Multi-Process and Tolerance Control

Project Overview

In high-tech industries such as 5G communications, 110 GHz microwave and millimeter-wave systems, industrial automation, semiconductor testing, and automotive electronics, equipment often depends on components that ensure accurate rotation and stable positioning.

The component shared here is one such part — an AL6061-T6 long shaft with an integrated flange — which calls for tight control of coaxiality, geometric tolerances, dimensional stability, and a reliable anodized and sandblasted surface finish.

Let’s look at how WayKen efficiently completed the components, using a coordinated combination of processes to achieve high precision and consistent quality.

Part Structure and Key Machining Requirements

The part features an integrated aluminum alloy structure combining a long shaft and a flange, with high overall performance requirements. The coaxiality between the shaft section and the flange mating holes must be controlled within 0.01 mm. The flange end face requires not only exceptional flatness but also strict perpendicularity to the shaft axis.

It also includes multiple deep holes and fine metrology features, which impose high requirements on positional accuracy. The finished part undergoes anodizing and sandblasting, ensuring corrosion and wear resistance while achieving a uniform, refined surface appearance that balances functionality with aesthetics.

Machining Challenges and Solutions

Some features of the part presented machining difficulties, requiring careful adaptation to ensure both precision and structural integrity.

1. Design Adaptation for Manufacturability

Early in the process, we found that two deep-hole features in the original design could not be realized using CNC machining. Traditional solutions, such as welding or press-fitting, posed significant risks: welding could deform the part due to heat input, compromising perpendicularity, while press-fitting risked cracking because of the part’s thin structure.

Optimized Solution

The design was revised to enable CNC manufacturability, guided by WayKen’s recommendations. We then proposed a composite structure combining mortise-and-tenon positioning with screw fastening to optimize the design. This approach uses high-precision mortise-and-tenon features to pre-locate the core components, ensuring accurate assembly positioning, and is supplemented by four standard screws at the base for final fastening.

By avoiding heat-induced deformation and structural damage, the solution significantly enhances connection rigidity and reliability. This optimization was ultimately adopted by the client and successfully implemented.

2. Multi-Process Machining Challenges

The long shaft does not conform to standard CNC turning principles. Its multiple complex structures — deep holes, side holes, and circumferential features — require a combination of CNC milling, EDM, and deep-hole drilling. Coordinating these processes presents challenges in sequencing, machine selection, and maintaining machining accuracy.

Strategy for Precision and Stability

To address common issues in long-shaft machining, such as vibration-induced deformation and error accumulation, a systematic multi-process coordination strategy was implemented:

• Flip-Turning for Deflection Control: Two clamping operations control deflection and radial vibration, maintaining stable axial dimensions and coaxiality.
• Deep-Hole Drilling: Specialized machines with peck drilling cycles, optimized feed, and spindle speeds ensure straightness, diameter accuracy, and surface quality of fine 3.5 mm deep holes.
• 4-Axis Milling: All circumferential features are machined in a single setup, preserving precise positional relationships.
• Wire EDM Slotting: Stress-free precision slotting ensures structural accuracy without deformation.
• 3-Axis Machining: End-face and local features are finished while maintaining strict reference consistency.
• Key Process Control Points: Optimized process sequencing and clamping design keep cumulative errors from multiple setups within 0.03 mm, with each operation executed under strict monitoring.

3. Runout and Tolerance Control

The original runout tolerance was difficult to measure and control. Flange and disc assemblies depend on manual screw torque, making consistent runout standards infeasible and affecting assembly accuracy.

Solution: Coaxiality-Based Tolerance

The original runout tolerance was converted into a reference-based coaxiality tolerance. By inspecting the coaxiality of assembly surfaces instead of the AB-reference runout, both measurement feasibility and part accuracy were ensured. Through appropriate process control and inspection methods, we maximized compliance with client standards.

Project Practical Experience

Design adaptation, process coordination, and tolerance control are essential to achieving reliable results in precision CNC machining:

• Design Optimization: Early identification of unmachinable features and effective communication prevented manufacturing risks. Mortise-and-tenon positioning combined with screw fastening resolved structural issues.
• Process Coordination: Multi-process machining strategies, including segmented turning, single-setup 4-axis milling, and coordinated deep-hole drilling with wire EDM, effectively controlled cumulative errors and ensured reproducible quality.
• Tolerance Management: Converting runout to coaxiality-based inspection ensured process feasibility and verifiable accuracy.

WayKen’s integrated capabilities, including DFM, multi-process machining, and advanced inspection, equip us to handle complex, tight-tolerance parts with confidence. With extensive experience in precision CNC machining, we support clients in achieving both reliable performance and efficient production.