Sinbo Precision High-Precision Pin Shaft Machining Solution: Providing Reliable Connections for Heavy Engineering

Case Background
A internationally renowned engineering machinery manufacturer encountered performance bottlenecks with key hinge pin shafts during the production of a new hydraulic excavator. Traditional pin shafts experienced early wear and fatigue fracture issues, seriously affecting equipment service life and reliability. The customer required a high-performance pin shaft capable of withstanding extreme working conditions, with excellent wear resistance, fatigue resistance, and dimensional stability.

Technical Challenges

• Material requirements: Withstand working loads over 50 tons, tensile strength ≥1000MPa
• Precision requirements: Diameter tolerance ±0.015mm, straightness ≤0.03mm/m
• Hardness requirements: Surface hardness HRC58-62, core maintaining HRC30-35 toughness
• Wear resistance requirements: Service life not less than 10,000 hours in sandy environments
• Anti-corrosion requirements: Adapt to humid, corrosive working environments

Solution
Sinbo Precision established a professional technical team and solved customer challenges through the following innovative solutions:

1. Material Optimization Selection
   Using 42CrMoA alloy steel, processed through vacuum degassing to ensure material purity
   Custom special heat treatment process to achieve perfect combination of surface high hardness and core high toughness
2. Precision Machining Process
• Using CNC lathes for rough machining to ensure benchmark accuracy
• Using high-precision cylindrical grinders for finish machining to ensure dimensional tolerance
• Using superfinishing process to achieve Ra0.2 surface finish
• Improving dimensional stability and wear resistance through cryogenic treatment
3. Surface Treatment Innovation
• Using double-layer chrome plating process, with porous chromium bottom layer for improved adhesion and dense chromium top layer for wear resistance
• Precisely controlling plating thickness at 0.03-0.05mm, with uniformity deviation <5%
• Using special sealing treatment to improve anti-corrosion performance
4. Quality Control System
• Implementing full-process SPC statistical process control
• Using CMM for full-size inspection
• Using metallurgical microscope for material structure analysis
• Conducting fatigue tests and wear tests to verify product performance

Machining Process

1. Material inspection: Chemical composition analysis, ultrasonic testing
2. Rough machining: CNC turning forming, reserving 0.3mm machining allowance
3. Heat treatment: Quenching and tempering → Hardening → Cryogenic treatment → Tempering
4. Finish machining: Precision grinding → Superfinishing
5. Surface treatment: Pre-plating treatment → Hard chrome plating → Sealing treatment
6. Final inspection: Dimensional inspection → Hardness testing → Nondestructive testing

Quality Results

• Dimensional pass rate: 99.8%
• Hardness uniformity: HRC60±1
• Coating adhesion strength: Reached the highest grade of ASTM B633 standard
• Fatigue life: More than 3 times higher than traditional products
• Wear resistance: Achieved the required 10,000-hour service life

Customer Benefits

1. Significantly improved equipment reliability, maintenance intervals extended by 300%
2. Reduced production costs, spare parts inventory reduced by 40%
3. Enhanced product market competitiveness, significantly improved customer satisfaction
4. Established long-term strategic partnership

Conclusion
Through technological innovation and strict quality control, Sinbo Precision successfully solved the technical challenges of engineering machinery pin shafts, providing customers with high-performance solutions. This case fully demonstrates Sinbo Precision's technical strength and service capabilities in the field of precision part machining.