Generated Article 📖

Hollow motor shafts are integral components in New Energy Vehicle (NEV) electric drive units, offering benefits such as reduced weight and improved performance. Various manufacturing technologies are employed to produce these shafts, each with distinct advantages and considerations. Below is an overview of current forming techniques, a comparative analysis based on key criteria, and recommendations for the most suitable manufacturing routes for this application.

Current Forming Techniques:

1. Flow Forming:

   • Process: A metal blank is rotated while rollers apply pressure, deforming the material into the desired hollow shape.

   • Applications: Suitable for complex shapes with varying wall thicknesses.

   • Materials: Applicable to various metals, including high-carbon steels.

   • Advantages: Achieves weight optimization and cost reduction; allows for design flexibility and efficient material usage.

   • Considerations: Requires specialized equipment and expertise.

2. Radial Forging:

   • Process: A hollow billet is compressed radially using multiple hammers while a mandrel shapes the inner diameter.

   • Applications: Ideal for producing strong, lightweight hollow shafts.

   • Materials: Commonly used with steels requiring enhanced mechanical properties.

   • Advantages: Improves mechanical properties through refined microstructure; suitable for high-strength applications.

   • Considerations: Involves significant equipment investment and process control.

3. Three-Roll Skew Rolling:

   • Process: A hollow billet is rolled between three skewed rolls, reducing diameter and forming the shaft.

   • Applications: Used for producing hollow shafts with constant wall thickness.

   • Materials: Suitable for various steels.

   • Advantages: Efficient for mass production; maintains uniform wall thickness.

   • Considerations: Requires precise control to avoid defects; limited to certain geometries.

4. Welding and Integrated Forming:

   • Process: Combines extrusion forming with welding to create hollow shafts.

   • Applications: Common in producing hollow shafts with stepped inner holes.

   • Materials: Applicable to various metals.

   • Advantages: Allows for complex internal geometries; adaptable to different designs.

   • Considerations: Welding may introduce weaknesses; requires thorough quality control.

5. Machining (CNC Turning, Milling, Grinding):

   • Process: Material is removed from a solid blank to achieve the desired hollow shape.

   • Applications: Used for precise geometries and small production runs.

   • Materials: Suitable for a wide range of metals.

   • Advantages: High precision; flexibility in design changes.

   • Considerations: Material waste is higher; less cost-effective for large volumes.

Comparative Analysis:

Recommended Manufacturing Routes:

For NEV electric drive units, the optimal manufacturing route depends on production volume, material requirements, and design complexity:

• High-Volume Production: Three-Roll Skew Rolling is advantageous due to its efficiency and ability to maintain uniform wall thickness, making it suitable for large-scale manufacturing.

• High-Strength Requirements: Radial Forging enhances mechanical properties, making it ideal for applications demanding superior strength and durability.

• Complex Geometries: Flow Forming offers flexibility in design and efficient material usage, accommodating intricate shapes and varying wall thicknesses.

• Prototyping and Low-Volume Production: Machining provides high precision and flexibility, suitable for small batches and design iterations.

In conclusion, selecting the appropriate manufacturing technology for hollow motor shafts in NEV electric drive units requires careful consideration of material properties, production volume, design complexity, and cost constraints. Aligning the chosen method with these factors ensures optimal performance and efficiency in the final product.

Generated Article 📖

Hollow motor shafts for New Energy Vehicle (NEV) electric drive units require lightweight, high-strength, and cost-effective manufacturing solutions. Current technologies balance material efficiency, mechanical performance, and production scalability. Below is an analysis of forming techniques, their trade-offs, and optimal applications.

**Current Hollow Shaft Manufacturing Technologies

1. Cold Forging (Near-Net Shape)

• Materials: High-strength steel alloys, including concast blooms or as-cast ingots with reduction ratios >3–5 [2][3].

• Process: Utilizes hydraulic presses for forming hollow preforms, followed by heat treatment, proof-machining, and stress relieving [3][4].

• Advantages:

  • Material savings: 30% weight reduction vs. solid shafts [3][6].

  • Cost reduction: 15% lower material costs vs. machining [4].

  • High productivity: 41% shorter machining time [3].

• Post-processing: Limited to stress relief and precision machining [3].

• Best for: High-volume production with strict weight and strength requirements (e.g., EV drivetrains) [4][6].

2. Radial/Rotary Forging

• Materials: Steel billets or hollow tube blanks [6][9].

• Process: Uses radial hammers (e.g., FELLS, GFM) for high-frequency deformation to create stepped inner holes [6][8].

• Advantages:

  • Integrated forming: Eliminates welding, improving structural integrity [6].

  • Precision: Directly achieves complex geometries (e.g., multi-stage inner diameters) [6][9].

• Limitations: Higher equipment costs (typically imported machinery) [6].

• Best for: High-performance shafts requiring cooling channels or lightweight designs [4][6].

3. Hollow Cold Rolling of Seamless Pipes

• Materials: Seamless steel pipes [5][8].

• Process: Combines cold rolling, annealing, forging, and heat treatment to replace traditional rod-based forging [5][8].

• Advantages:

  • Cost/time savings: 50% lower cycle time vs. conventional methods [5].

  • Sustainability: 68% material utilization rate, reduced energy waste [5].

• Post-processing: Surface treatment and precision machining [8].

• Best for: Mid-volume production with moderate strength requirements [5][8].

4. Welded Hollow Shafts

• Materials: Steel tubes or extruded profiles [6].

• Process: Extrusion forming followed by friction or laser welding [6].

• Advantages:

  • Flexibility: Compatible with diverse geometries.

  • Weld strength: 80–90% of base material strength achievable [6].

• Limitations:

  • Costs: 20% higher vs. solid shafts due to post-weld inspections (ultrasonic/X-ray) [6].

  • Weight reduction: Limited to 30–35% [6].

• Best for: Prototyping or custom designs with moderate volumes [6].

Comparative Analysis

Recommended Manufacturing Routes

1. Cold Forging: Optimal for high-volume NEV applications requiring lightweight, high-strength shafts with minimal post-processing [3][4].

2. Radial/Rotary Forging: Preferred for shafts integrating cooling channels or multi-stage inner diameters, critical for high-speed EV motors [6][9].

3. Hollow Cold Rolling: Cost-effective alternative for mid-volume production with simpler geometries [5][8].

Welded methods remain niche due to reliability concerns, while advancements in forging and rolling technologies dominate NEV electrification trends. Manufacturers prioritizing energy efficiency and lifecycle costs should adopt integrated cold forging or radial forging processes [4][6][9].

参考文献：

[1] https://richconn.com/motor-shaft-machining/

[2] https://www.mdpi.com/2075-4701/14/6/702

[3] https://patents.google.com/patent/US9446445B2/en

[4] https://www.kanetakogyo.co.jp/en/latest_technology/hollow_shaft/

[5] http://www.patentbuddy.com/Patent/WO-2020253550-A1

[6] https://www.yeaphi.com/news/hollow-technology-of-motor-shaft/

[7] https://eprints.whiterose.ac.uk/197799/1/A_Manufacturing_Driven_Design_Methodology_to_Lightweighting_of_the_Structural_Elements_of_a_Permanent_Magnet_Electrical_Machine_Rotor.pdf

[8] https://patentimages.storage.googleapis.com/45/d9/d8/6a600c526a36d3/EP3854517A1.pdf

[9] http://www.astrj.com/pdf-139134-67808?filename=Conception+of+Hollow.pdf

[10] https://info.ornl.gov/sites/publications/files/Pub31707.pdf