CNC Machined 7075-T6 Aluminum Rotor for High-Speed Turbine Generator Applications

Product Overview

Product Name

High-Speed Turbine Generator Rotor

Application

Used in a customized turbine generator system developed by the customer for oil and gas industry applications.

Material

7075-T6 Aerospace Grade Aluminum Alloy

7075-T6 was selected because of its excellent strength-to-weight ratio, high fatigue resistance, and suitability for high-speed rotating components where weight reduction is critical.

Key Specifications

• Final Outer Diameter (OD): 90.00 mm ±0.01 mm
• Overall Length: 150.00 mm ±0.02 mm
• Central Bore Diameter: 72.00 mm ±0.01 mm
• Wall Thickness: 9 mm radial thickness
• OD Surface Finish: Mirror polishing, Ra ≤0.2 μm
• Dynamic Balance Requirement: G2.5 or better at 100,000 RPM
• Edge Treatment: 0.1–0.2 mm chamfering on all edges

Thread Features

The rotor includes precision internal threads on the central bore:

• Thread type: UNJF / MJ fine thread specification
• Pitch: 1.5 mm
• Thread depth: 1.5 mm per side
• Thread length: Minimum 35 mm
• One side: Left-hand thread
• One side: Right-hand thread

The opposite thread directions were designed to provide a self-tightening effect during high-speed rotation.

Manufacturing Challenges

1. Extremely Tight Dimensional Tolerances for High-Speed Rotation

The biggest challenge was maintaining dimensional stability during machining.

For a rotor operating at 100,000 RPM, even a small amount of runout or imbalance can create vibration issues.

The requirements included:

• OD, bore, thread, and blade features must maintain 0.01 mm TIR concentricity
• Bore and outer diameter must remain perfectly aligned
• Thread machining must maintain precise positioning without burrs

Traditional machining methods could easily introduce deformation or misalignment, especially when removing large amounts of material from 7075-T6 aluminum.

2. Complex Rotor Structure and Difficult Blade Formation

The rotor design included thin blade-like features that needed to be integrated with the main body.

The challenge was that these blades were:

• Thin and easy to deform
• Difficult to machine as a one-piece structure
• Sensitive to cutting force and vibration

Attempting complete one-piece CNC machining would create risks such as:

• Excessive tool vibration
• Blade deformation
• Low machining efficiency
• Difficulty controlling final geometry

A different manufacturing approach was required.

3. Mirror Surface Finish Requirement

The external surface required a mirror polishing finish with Ra 0.2 μm or better.

For high-speed rotating parts, surface quality directly affects:

• Air resistance
• Rotational efficiency
• Heat generation
• Long-term stability

However, 7075-T6 aluminum is relatively soft compared with steel, meaning polishing can easily create:

• Uneven reflections
• Rounded edges
• Surface scratches
• Local deformation

Maintaining both precision geometry and a high-quality polished surface required careful process control.

Our CNC Machining Solution

1. Optimized Step-by-Step Manufacturing Process

Instead of forcing the entire rotor to be machined from a single piece, our engineering team developed a more practical process:

Step 1: CNC Machining of the Main Rotor Body

The main rotor structure was first machined from 7075-T6 aluminum billet.

During this stage, we focused on:

• Outer diameter accuracy
• Central bore machining
• Thread positioning
• Overall concentricity control

Multiple inspection points were added during machining to prevent cumulative errors.

Step 2: Independent Blade Manufacturing

Due to the complexity and thin structure of the blades, the blade sections were manufactured separately.

This approach helped us achieve:

• Better dimensional control
• Reduced machining stress
• Improved surface quality
• More stable production consistency

After machining, the blade components were carefully positioned and assembled with the rotor body.

Step 3: Precision Assembly and Finishing

After the blade integration process, the complete rotor went through additional finishing procedures:

• Alignment inspection
• Surface refinement
• Precision polishing
• Final dimensional verification

Special attention was given to maintaining:

• Blade position accuracy
• Rotor symmetry
• Surface smoothness

2. Precision Thread Machining

The internal fine threads required special attention because they directly affect assembly reliability under high rotational loads.

Our process included:

• Dedicated thread machining tools
• Controlled cutting parameters
• Multiple inspections after machining

The final threads were verified for:

• Clean thread profile
• No burrs
• Correct pitch
• Proper concentricity with the rotor axis

3. Dynamic Balancing and Quality Inspection

Before delivery, the finished rotor underwent final inspection procedures:

• Dimensional inspection of critical features
• Concentricity verification
• Thread inspection
• Surface quality inspection
• Dynamic balancing test

The rotor was balanced to meet the required G2.5 or better standard at 100,000 RPM.

Project Results

Through process optimization and close engineering cooperation, we successfully delivered a rotor that met the customer's demanding performance requirements.

Key Achievements:

✅ High precision machining
Critical dimensions were controlled within ±0.01 mm requirements.

✅ Stable high-speed rotation performance
The rotor passed dynamic balance requirements for 100,000 RPM operation.

✅ Complex structure successfully manufactured
The separate blade manufacturing approach solved the biggest machining challenge and ensured structural accuracy.

✅ Premium surface quality achieved
The mirror-polished aluminum surface met the customer's aerodynamic performance requirements.

Why the Customer Chose Our CNC Machining Capability

This project was not simply about producing an aluminum part. It required a combination of:

• 7075-T6 precision machining experience
• Complex structural manufacturing capability
• High-speed rotating component knowledge
• Advanced surface finishing technology
• Flexible engineering problem-solving

By redesigning the manufacturing process around the actual machining challenges, we helped the customer transform a difficult rotor design into a reliable production-ready component.

For projects involving high-strength aluminum parts, turbine components, precision rotors, or other high-speed rotating assemblies, our engineering team can provide customized CNC manufacturing solutions from prototype development to production.