An Example of Observing Reduction Gear Using the Microfocus X-Ray CT System

Significance of the Topic

Non-destructive inspection of reduction gears is essential to ensure safe, reliable operation in applications ranging from automotive drivetrains to industrial machinery. Traditional disassembly methods risk damaging components and are time-consuming. High-resolution X-ray computed tomography (CT) addresses these challenges by revealing internal structures, defects, and foreign inclusions without dismantling, thus supporting design improvements and stringent quality control.

Objectives and Study Overview

This study demonstrates the application of the Shimadzu inspeXio™ SMX™-225CT FPD HR Plus microfocus X-ray CT system to:

• Visualize the internal geometry of a parallel-shaft reduction gear assembly.
• Quantify gear backlash, detect embedded foreign matter, and analyze porosity.
• Highlight the advantages of combined overall and magnified imaging modes.

Methods and Used Instrumentation

Imaging was performed on a reduction gear measuring approximately 60 × 60 × 70 mm, composed of metal housing, gears, bearings, and shafts. Two CT modes were applied: overall view and magnified region of interest.

• System: inspeXio SMX-225CT FPD HR Plus (Shimadzu)
• Tube voltage/current: 220 kV, 400 µA
• Number of views: 2400; exposure time: short; total scan time: ~40 min
• Field of View: Ø104 × 74 mm (overall), Ø55 × 39 mm (magnified)
• Voxel size: 0.102 mm (overall), 0.054 mm (magnified)
• Software: VGStudio MAX for dimensional measurement, defect identification, and porosity analysis

Main Results and Discussion

CT cross-sections verified part geometry and gear alignment. Key findings include:

• Gear Backlash Measurement: Dimensional analysis revealed a backlash of approximately 0.16 mm in the assembled gear train.
• Foreign Matter Detection: Two iron sand particles (1–2 mm) introduced deliberately were located and rendered in 3D after color-coding, confirming the ability to pinpoint inclusions in X, Y, Z coordinates.
• Porosity Analysis: Automated pore detection identified 149 pores in the overall scan and 285 in the magnified scan. The smallest detected volumes were 8.2 × 10⁻³ mm³ (overall) and 4.4 × 10⁻³ mm³ (magnified). Pore-volume distribution plots highlighted enhanced resolution and sensitivity of the magnified mode.

Benefits and Practical Applications

The demonstrated CT approach offers:

• Non-destructive verification of internal dimensions and clearances in assembled components.
• Quantitative detection of contaminants and micro-defects that could compromise performance.
• Data-driven feedback for design refinements, prototyping, and production quality assurance.

Future Trends and Potential Applications

Advances likely to expand CT utility include:

• Integration of AI-driven defect recognition and automated reporting workflows.
• Faster detectors and optimized scanning protocols for higher throughput in production environments.
• Multi-modal imaging combining X-ray CT with other analytical techniques for comprehensive material characterization.
• Development of portable or in-line CT solutions for real-time monitoring on assembly lines.

Conclusion

The inspeXio SMX-225CT FPD HR Plus microfocus X-ray CT system enables comprehensive, non-destructive evaluation of complex metal assemblies such as reduction gears. By accurately measuring gear backlash, detecting foreign inclusions, and quantifying internal porosity, this method enhances quality control, informs design improvements, and supports the reliability of critical mechanical systems.