Camera, Eddy Current, Laser… How to Choose the Right Inner-Diameter Inspection Method

In quality inspection of inner-diameter components, various methods are used.

・Camera(vision)

・Eddy current testing

・Capacitance

・Laser

Each method has its own strengths, but in practice the following challenges often arise:
“Fewer defects detected than expected” or “Results are unstable when conditions change.”

In most cases, the root cause lies in the compatibility between the inspection method and the target workpiece.

Camera Method

The camera method excels at detecting visual defects such as scratches, foreign matter, and surface conditions.
However, in inner-diameter inspection, it is susceptible to the effects of lighting angle, bore depth and diameter, and reflections, making condition setup difficult.

Eddy current testing

Eddy current testing is well suited for detecting internal defects such as cracks and material flaws.
However, since it is affected by material type and surface conditions, careful selection based on application is required.

Laser Method

The laser method irradiates the inner wall of a workpiece with laser light and acquires the intensity distribution of the reflected light.
The acquired signal is visualized as 256-level grayscale, enabling stable observation of anomalies such as casting porosity, scratches, and surface condition changes across the entire inner circumference.
In addition, the cylindrical inner surface can be displayed as an unrolled image, making it easy to identify the location and extent of defects.

Summary

In inner-diameter inspection, the most suitable method depends on:
・ What defects need to be detected
・ The material and geometry of the workpiece

Particularly when the following need to be confirmed:
・ Inner wall surface condition
・ Distribution of casting porosity or scratches

Laser reflection-based inspection is one effective option to consider.