The benefits of using nonlinear resonance NDT for the part qualification of AM medical devices.
Additive manufacturing (AM) offers unprecedented opportunities for creating highly customised medical devices, implants, and prosthetics. However, with this innovation comes the critical challenge of ensuring that these devices meet the strict safety and reliability standards required for medical applications. Traditional non-destructive testing (NDT) methods, such as X-ray CT, or destructive techniques like tensile testing, often fall short in adequately qualifying complex AM parts. This is where Theta Technologies’ nonlinear resonance NDT shines as an industry-enhancing solution, offering medical device manufacturers a more reliable, efficient, and scalable method of part qualification.
Challenges with existing part qualification methods for AM medical devices.
If you’re involved in the manufacturing, or the use of AM medical devices, you already understand how pivotal part qualification is, both to human life, reputation, and mitigating the risks of financial repercussions. The reality is that even a minor flaw situated within an implant could lead to severe complications for the patient, requiring additional surgeries and resulting in prolonged recovery times.
Currently, medical device manufacturers rely on various NDT techniques to qualify components, but many are increasingly outdated or simply unable to deliver the reliability the industry needs. Tensile testing, for instance, was designed to fulfill the needs of simpler traditional manufacturing practices and is not wholly representative of the intricate geometries and material properties of AM-produced parts. Other methods such as X-ray radiography may be astute at identifying flaws in early development stages, but should high-volume production batch testing be your requirement, slow test speeds render this method impracticable. Optical inspection, where human inspectors often examine components under microscopes, can be slow and susceptible to human error. These methods, though helpful in some cases, can lack the sensitivity, speed, and scalability needed for the rigorous demands of AM medical devices.
An AM medical device implant being placed into RD1-TT in preparation for a nonlinear resonance non-destructive test.
Introducing nonlinear resonance NDT: Theta Technologies’ innovative solution
Theta Technologies’ nonlinear resonance NDT presents an innovative leap forward in part qualification, especially for medical devices manufactured through AM. Unlike traditional NDT methods, nonlinear resonance can test complex AM structures directly and efficiently, without the need for additional tensile specimens or coupons.
How does nonlinear resonance NDT work?
Nonlinear resonance NDT involves exciting a component at varying energy levels, causing it to resonate. A baseline resonance signature is first established with low energy, unique to the material and geometry of the part. As the energy input increases, nonlinear behaviours are activated if any hidden or microscopic flaws, such as cracks or inclusions, are present. Flawed components show deviations from the expected linear frequency response, while flawless parts maintain their baseline signature at higher energy levels.
This technique is ideal for AM medical devices as it tests the integrity of the parts themselves, rather than relying on secondary structures or test coupons that are not entirely representative of the final product. It provides a sensitive, accurate way of detecting hidden defects that other methods may miss, ensuring that the parts deployed in real-world medical scenarios meet the highest safety and quality standards.
Enhancing part qualification in medical device manufacturing
For medical device manufacturers, nonlinear resonance NDT offers a range of compelling benefits that enhance part qualification processes and mitigate risks:
Rapid, scalable testing:
Nonlinear resonance NDT can perform part inspections in under a minute. This high-speed testing capability allows manufacturers to test entire production batches quickly, rather than relying on sampling. Faster testing improves production efficiency and reduces the risk of faulty parts slipping through.
Surface finish agnostic:
Many AM methods, particularly for metal parts, produce components with rough surface finishes. Traditional inspection methods often struggle to cope with this, but nonlinear resonance NDT is unaffected by surface roughness. This opens up possibilities for testing parts that might otherwise be deemed untestable using standard techniques.
By their very nature, medical devices are designed to be rough surface components. Those surface peaks and troughs mean that you can use cementless processes and help the bone integrate the typically titanium or ceramic component. From a similar phenomenon some mesh parts also have this behaviour, but a cracked mesh link is very hard to see on XCT/ Optical inspection or to detect via tensile testing and the like.
Heightened sensitivity:
Nonlinear resonance excels at detecting even the narrowest of flaws in complex AM structures, including internal cracks or lack of fusion defects. For medical devices where reliability is paramount, this level of sensitivity provides greater confidence in part integrity.
Pre and post-processing inspection:
The ability to inspect parts at various stages of post-processing, from immediately after the build to post-heat treatment or machining, ensures that potential flaws are detected at every critical phase of the manufacturing process.
Reduction in test coupon dependency:
Nonlinear resonance testing eliminates the need for manufacturers to produce tensile test coupons alongside production batches, freeing up build space for more parts and reducing the time and costs associated with producing auxiliary test pieces. This enables manufacturers to focus on testing real, usable parts rather than samples.
Minimising patient risk:
By ensuring that medical devices meet rigorous standards, nonlinear resonance NDT reduces the likelihood of part failures, which can lead to critical patient complications. This offers peace of mind not only to manufacturers but also to healthcare professionals and patients relying on the safety of implants and devices.
Image: Medical device implants produced using additive manufacturing
Additional data acquisition for accelerated wear assessments
Medical device regulations and notified bodies across the globe can prove to be a navigational challenge, not least of which is defining a “medical device”. A consistent theme across the various regulations and countries, however, is the need for manufacturers to prioritise post-market surveillance and raise medical device alerts (MDA) for faulty products. Given the primary aim of a medical implant is to restore movement to a patient, component wear is naturally a major manufacturing consideration to reduce revision rates and build a reputation of high-quality, high-performance, and robust products.
Although nonlinear resonance has been designed specifically to identify potentially detrimental flaws with components, the versatility of the technology goes far beyond flaw detection. Additional linear data acquired during the test process can prove invaluable in the assessment of anticipated volumetric wear in AM medical implants. With high dimensional sensitivity, manufacturers can build an understanding of how their manufacturing process impacts the final product.
Graph: A visual representation of how additional data acquired during a nonlinear resonance test can help assess wear in AM medical devices.
Scaling additive manufacturing in the medical industry
Additive manufacturing holds immense promise for the future of healthcare, allowing for the creation of personalised implants and devices that meet the specific needs of individual patients. However, scaling AM production to meet growing demands requires reliable, fast, and cost-effective part qualification processes that can ensure the integrity of components intended for use. Traditional methods are often too slow, expensive, or inconsistent to allow for large-scale production of AM medical devices.
Nonlinear resonance NDT, on the other hand, offers a viable solution for scaling AM production without compromising on quality. Its speed and sensitivity make it possible to inspect high volumes of parts efficiently, paving the way for broader adoption of AM technologies in medical device manufacturing. As AM becomes increasingly mainstream in the medical sector, ensuring the reliability of these components through advanced NDT techniques will become even more critical.
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Experience the power of nonlinear resonance NDT for your AM medical devices
If you’re a medical device manufacturer looking for a more reliable, efficient, and scalable solution for part qualification, Theta Technologies’ nonlinear resonance NDT is the answer. By leveraging this innovative technology, you can enhance the reliability of your AM parts, reduce the risk of failure, and streamline your manufacturing process – all while ensuring patient safety.
To find out more about how nonlinear resonance NDT can revolutionise your part qualification process, visit www.thetandt.com, or contact our team to arrange a complimentary technology demonstration on your own components. Experience firsthand how nonlinear resonance NDT can help you deliver higher-quality, safer medical devices.
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