Is new vision technology the future of inspecting medical devices?
Juha Saily, regional development manager, Helmee Imaging, highlights how new vision technology enables automated in-process inspection of medical devices with high gloss, specular and clear surfaces.
Quality inspection in the manufacture of medical devices with demanding high-gloss and specular finishes is often performed manually by human visual inspection. This is because traditional machine vision systems cannot capture good enough images of such surfaces, and dedicated systems designed for characterisation of high gloss parts are slow and work adequately in sampling-based laboratory applications only. The technical challenge is even more difficult when inspected parts or assemblies have contoured, sloping or complex surface geometries that reflect just a small portion of light, if any, to the system’s cameras or sensors.
A new machine vision technology, Covered Stereo Deflectometry (CSD) by Helmee Imaging, addresses all disadvantages of existing automated systems, and human visual inspection alike. High-speed in-process inspection of complex high gloss parts can now be automated which makes all the well-known benefits of automatic 100% product inspection available also to more challenging applications.
Deflectometry is a common technique and works well in inspection of flat high-gloss surfaces. Covered Stereo Deflectometry expands from it in several ways allowing the capture and analysis of high-quality high-resolution images also of contoured, sloping and complex surface geometries.
Imaging hardware
It is important to get light emitted by light sources to the cameras from a highly reflective non-flat surface. This is accomplished by a semicircle-shaped membrane that diffuses light evenly onto the target surface from all directions that the membrane covers the part.
The system’s wide angle of view reduced the number of cameras making the CSD system simpler, more robust, and easier to setup and maintain than common deflectometry solutions that may contain more than 10 cameras.
Imaging and analysis sequence
Light sources outside the membrane project a very quick series of striped patterns onto the inspected surface. Pattern direction, width and the number of captured images vary and depends on the inspected object and its surface. The system’s camera(s) capture these raw images that are instantly processed into result images by complex mathematical algorithms. The CSD image processing software can produce about 30 different result image types for handing virtually any surface and defect type from part deformation to missing material to pin holes and anything in between.
The CSD software is recipe-based, and all parameters are selected by it making part changeovers extremely quick. No physical adjustment or alignment for light sources, cameras, or other imaging components are ever required.
Setup for a new product is quick with Helmee’s AI/ML (Artificial Intelligence and Machine Learning) software that is currently being implemented in phases. Setup allows configuring the system for detected defect type, size, shape, and frequency. Both 2D defects and 3D imperfections can be detected and analysed with CSD.
When the software detects a severe enough defect violating any of the acceptance rules, the unit sends a signal to solution’s parts handling automation to remove the part from the production line. Inspection time, reject reason, serial number, image, etc. can be saved in the database for reporting and tracking purposes.
System integration and parts handling automation
A complete CSD solution consists of an imaging core unit and software, and parts handling automation that is based on a conveyor or a robot, depending on the application. Conveyor is a simpler approach and works well with parts that can be inspected without turning them. Robotised infeed and handling is recommended when multiple sides of the part need to be inspected.
Since the CSD core units include all necessary imaging hardware and software, they are easy to integrate into external systems. The core units come even with an integrated PC, and the software is preinstalled. Connecting the system into a PLC, factory network and cloud is simple and straightforward.