In automated spark plug assembly, the precise detection of the smallest assembly errors is crucial for quality and process reliability. A typical challenge is gap detection between the metal thread and the ceramic body. Even minimal gaps can indicate faulty assembly and must be reliably detected – despite short cycle times and demanding ambient conditions.
In the application, the individual spark plug components are brought together from separate feeders and assembled on an assembly machine. The fully assembled spark plug is positioned on a rotary indexing table and stops for a few milliseconds in front of the image processing sensor. During this short time window, the optical inspection for possible assembly errors takes place.
The aim is to reliably detect a possible gap between the metal thread with ring flange and the porcelain body. Such a gap indicates an incorrectly installed assembly and must be ejected at an early stage.
The solution is based on a weQube+ vision sensor in combination with backlighting. If a gap occurs, the bright light from the illumination can be detected by the sensor through the gap. This creates a clear brightness contrast that is particularly suitable for image evaluation.
The bright area is evaluated using the “Find segments on line” tool. By setting the segment brightness to “bright”, the gap can be detected and measured directly. Even very small gaps can be reliably detected in this way.
Stable measurement results are also ensured by an image coordinate system that compensates for positional deviations of the spark plug. At the same time, the system checks whether the threaded part is correctly present. These test results can be logically linked via a spreadsheet module to produce a clear good or bad signal. The results are passed on to the machine via digital inputs and outputs.
The solution described works very reliably even in dynamic and dusty environments. If higher measuring accuracy is required, several optimization options are available. Firstly, the image processing sensor can be positioned closer to the component, which further increases the resolution.
On the other hand, depending on the format, integration and performance requirements, the Smart Camera B60 can also be used for this application. It is also suitable for gap detection on spark plugs and enables a stable evaluation for comparable testing tasks. If even greater measuring accuracy is required, telecentric lenses can also be used. These are used in particular when very tight tolerances must be reliably maintained.
The combination of targeted illumination, intelligent image processing and logical linking of several inspection criteria makes gap detection on spark plugs reliable and process-safe. Whether with weQube+ or alternatively with the Smart Camera B60: the flexible system architecture enables a tailor-made implementation for different machine concepts and quality requirements – and thus creates a stable basis for efficient, automated quality control in spark plug assembly.
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