A close look: The key role of visual inspection in quality control
Visual inspection of catheters and stents continues to play a key role in quality control, as Ash Technologies explains.
High definition imaging technology combined with inspection and measurement software has enabled digital microscopes to become an essential tool in quality control, inspection and production for the medical device industry.
Improving stent inspection
There are a number of common defects which occur during the manufacture of stents, such as cracks, pits, score marks and scratches. It is essential that these defective stents are repaired or rejected from production.
High resolution imaging, high magnification, large field of view and lighting are important factors for stent inspection. With Full HD 1080p at 60 frames per second, the Omni provides the perfect resolution to see defects and reduce any lag effect which can disorientate the operator.
Lighting is also critical in achieving a sharp image. Diffused LED lighting reduces reflection on the stent surface and greatly improves the image clarity.
The Omni digital microscope has a large magnification range and large field of view, which makes it easier to switch from an overview of the stent to a close-up view of a particular area. This in turn saves time as the operator can quickly identify a problem area and focus in on it.
One of the challenges when visually inspecting a stent is its cylindrical shape. A convenient way to manoeuvre the stent is by using a rolling stage. This allows the operator to easily rotate the stent and inspect all areas for defects.
Improving balloon catheter inspection
The manufacture of balloon catheters is a complicated process that can occasionally result in defective products. Common defects which occur during the manufacturing of balloon catheters include gel spots, “fish eyes” and foreign particles. Due to the safety critical nature of balloon catheters it is essential that all defects are eliminated before being shipped.
Balloon defects can often be difficult to identify and categorise with traditional inspection tools. However digital microscopes provide an effective solution to inspect and measure balloon catheters.
Polarised lighting is very useful for detecting surface defects in materials like balloons. The polarisation interference patterns uncover common defects such as gel spots and ‘fish eyes’. This technique involves using a polarising filter on both the lens and sub stage light. The lens polarising filter is rotated to produce the interference patterns.
Measurement of medical device parts
Omni’s integrated measurement software can be used to carry out measurements of stent struts and to add text if something needs to be labelled.
Technical drawings of medical device parts can be imported as DXF files and used to create overlay templates with tolerance limits ensuring continuity of quality control from the design of the part.
Measurement overlays of specific part dimensions can also be created to enable a qualitative inspection against on-screen templates. These overlay templates can be configured with part-specific camera and lighting parameters to ensure reproducibility and standardisation of inspection conditions.
A repeatable inspection process ensures produced parts are of consistent quality. The automatic edge detection feature in the Omni measurement software ensures that measurements are repeatable thus reducing variability between operators.
Digital microscopes are also appealing for the medical device industry, due to their efficiency. The Omnis can maintain calibration whilst zooming, so there is no need for time consuming recalibrations between changing magnifications.
All data captured using the Omni digital microscope can be saved to the network for efficiency or stored on internal and external memory as required.
Advantages that digital microscopes can offer medical device inspection processes:
Improved ergonomics: Operators can inspect and analyse samples while sitting or standing comfortably for longer periods of time.
Improved workflow efficiency: Reduces the number of steps and tools involved in inspection and analysis through integrated, easy to use inspection and measurement software applications.
Documentation of inspection: Offers traceability and documentation of inspection and analysis through image capture for reporting and quality control purposes.
User control: Offers improved traceability and control if many different users work with the same microscope.
Key applications for digital microscopes within the medical device industry include:
• Inspection of the surface of a medical device to detect defects
• Measurement of medical device parts