Metrology vision systems are an essential tool in medical device manufacturing

Medical devices impact and save millions of lives annually. As such, healthcare providers and their patients rely on manufacturers to deliver the highest-quality products, from pacemakers to artificial joints to arterial stents. With little room for error, metrology vision systems have become an essential tool in manufacturing U.S. Food and Drug Administration (FDA)-compliant healthcare products that are safe, reliable, and effective. Proven innovations such as advanced vision systems are helping device makers overcome challenges in the dynamic healthcare manufacturing environment.

Material variability & complex geometry

Medical devices have revolutionized healthcare by delivering novel therapies, diagnostic capabilities, and treatments. Tiny bone screws, microscopic syringes, catheters, stents, and other minute parts require strict standardization. These can be challenging for a host of reasons, including being able to accurately measure in a production environment.

Biocompatibility of materials is imperative to protect patient health. Device designs may feature reflective or transparent materials to reduce rejection rates. For example, a stent is a single wire-mesh device ranging from 8mm to 38mm in length and about 2.5mm to 4.0mm in diameter. Standard vision systems typically measure to about 2μm accuracy, with higher-end machines down to about 250nm . Specialty equipment is necessary to evaluate clear or shiny surfaces of an implant or other devices. Surface variability is also a factor. In some cases, a device may be prone to damage due to size, material, and geometry, requiring measurement with a non-contact method.

Vision systems

Highly accurate, best-in-class vision systems for non-contact dimensional measurements are available in a range of sizes, speeds, resolutions, and sensor capabilities. Engineered with high-quality components for better durability and longevity, with faster and more accurate edge detection, pattern recognition, and measurements, the latest vision systems can provide tremendous value in medical device applications.

Various lighting options, including white light interferometers as a 3D non-contact scanning sensor, can take highly accurate measurements of ever smaller and more complex devices. Rapid processing can achieve sample rates of hundreds of thousands of data points in mere seconds. In conjunction with a built-in, high-performance camera, some machines support versatile probe options, such as touch-trigger and scanning contact probes for more prismatic geometry, features, and materials that can’t be inspected by vision alone. These data points from various sensors can be combined to get a full inspection on the same platform.

Modular vision systems allow for adaptive light sources, with options to add hyper spectral lighting or a strobe light, or the ability to switch out light sources to accommodate material variability of products. Flexible, near colorless materials in varied states can make visual machine inspection more challenging because they lack the contrast needed by vision machines to detect a surface or an edge. Strobe lights can also be used to enable nonstop motion during a measuring event, while optical sensors, such as laser or white light interferometry (WLI), are used to achieve high-accuracy Z measurements and complex profiles.

While vision systems historically haven’t been considered truly three-dimensional, using these advanced sensors is changing that. Next-generation vision systems using a grid pattern or structured illumination can create contrast when it isn’t present to obtain the general shape of the object being measured, enabling the image to be created on the camera. Optical deconvolution methods bring the ability to move the vision machine along the Z axis and look at different images within a stack on that axis. While analyzing these images for in-focused pixels, a 3D data set can be obtained for detailed topographical and geometric measurement.

This type of 3D imaging is particularly useful in medical applications. For example, the shape of a knee replacement part has unique contours with a mirror-finish surface. A through-the-lens laser sensor can enable automatic tracking of the part’s surface, following contours while the machine moves, eliminating the need to stop the camera to refocus. Tracking autofocus with laser technology dynamically adjusts to maintain the targeted feature in focus for camera measurements. When combined with strobing, this approach significantly increases measurement throughput while preserving accuracy and reliability in real time, even for ultra-small dimensions.

Add-on artificial intelligence (AI) solutions can further augment defect detection by teaching a model to look for defects. This is usually accomplished by providing a data set of images illustrating the defect, before a human teaches the model by labeling the defect within a particular image. The trained model can then be deployed to a vision system to look for defects. Highly accurate and traceable artifacts are also used to mathematically correct errors associated with hardware, specifically the main optical objective lens. This helps calibrate lenses exhibiting geometric aberrations, enhancing isometric filtering, and increasing accuracy when calibrating pixel sizes. Optical aberrations can also be mapped out for each lens to adjust for the field of view and compensate for additional inaccuracies.

Regulatory compliance

The digital era has been a boon, streamlining data collection and recordkeeping while adding new layers of compliance in the competitive medical device manufacturing field. FDA-compliant medical device manufacturers are urged to embrace data governance and security to protect patients, proprietary data, and brand integrity. In the United States, medical device manufacturers must adhere to FDA regulations by implementing processes safeguarding the collection and storage of electronic records.

Each new vision machine must be validated against existing processes. Even software upgrades require revalidation. Validation can be challenging with the wrong technology or vendor. Compliance with the food and drug code of federal regulations on electronic records and signatures (21 CFR Part 11) can be achieved by specifying vision solutions and software backed by technologies keeping pace with the regulations.

The right system partner can assist in evaluating and choosing vision solutions and software to leverage electronic data and records while providing documentation and training to support standard operating procedures. A fully compliant solution can streamline FDA audits and improve efficiencies while delivering the safest possible products.

Integrating automation

Delivering quality products on ever-tighter production schedules is par for the course for medical device manufacturers. Automation and robotics have advanced in the medical device measurement industry and have helped improve many elements of the production process.

In lower-volume manufacturing operations, easy-to-use, benchtop vision inspection systems are readily available. Although manual, they feature numerous capabilities found in higher-end CNC machines, such as pattern recognition, measurement macro playback, automatic light controls, and edge detection. Higher-volume manufacturing brings greater challenges.

New metrology inline sensors and high-speed cameras have been developed to meet demand in production operations with enhancements to automation and robotics. Automated programs for measurement systems expedite measurement cycles and production timelines by removing labor-intensive human interventions from the processes by using a rapidly moving sensor to capture images with a camera to build a topographical map of areas of interest.

Multiple parts can be detected and measured simultaneously, efficiently, and quickly using automated machines. For example, 2D profilers with scanning frame rates up to 10KHz can be used to obtain 3D point cloud data of the medical device. These sensors have also been used on the end of a robot arm collecting data while the robot is in motion.

Vertically integrated

Manufacturing medical devices requires the highest level of planning, precision, accuracy, and quality to ensure patient safety and deliver optimal care. Vision systems are an essential part of this industry, and it’s important to choose the right type of vision measurement equipment along with supporting technologies to capture critical measurements accurately and efficiently. As medical parts continue to get smaller and more complex, the role of vision systems in the medical manufacturing industry will continue to grow, with new solutions designed to address these challenges with reliability and confidence.

About the author: Allen Cius is product group manager at Mitutoyo America Corp.

Mitutoyo America Corp. 
https://www.mitutoyo.com
IMTS 2024 booth #134117