Additive manufacturing (AM) technology, more commonly known as 3D printing, has seen a massive evolution in the past few years. From being used for prototypes and concepts, the technology has progressed to part-for-part substitution and the creation of unique, AM-specific part geometries. Today, these applications are increasingly present in demanding, mission-critical fields such as medicine and aerospace, where materials with specific thermal, stiffness, corrosion, and static loading properties are required. To advance in these arenas, metallic, ceramic, and polymer composite AM parts need to be free from discontinuities, and the manufacturing processes have to be stable, robust, and repeatable. And the nondestructive testing (NDT) technology and inspection methods will need to be sufficiently capable and reliable to ensure that discontinuities will be detected to prevent the components from being accepted for use.
The AM technology has seen a tremendous evolution in the past few years, and its impact on manufacturing is substantial. It has opened up new possibilities in terms of design and has the potential to change how we think about manufacturing. With the ability to create unique geometries, manufacturers can now design and produce complex parts that would have been impossible to create using traditional manufacturing methods.
But the technology’s advancement hasn’t come without its challenges, particularly when it comes to material quality. In critical industries like aerospace and medicine, where lives depend on the quality of the parts produced, there’s no room for error. The parts need to be free from discontinuities, and the manufacturing process has to be stable, robust, and repeatable to ensure quality. To ensure that AM parts are up to standard, NDT technology and inspection methods have to be reliable and capable enough to detect any discontinuities that might compromise the parts’ quality.
In this blog post, we’ll discuss the impact of AM technology on critical industries like medicine and aerospace, the challenges manufacturers face in producing high-quality parts, and the role of NDT technology and inspection methods in ensuring that AM parts meet the required standards.
AM Parts in Demanding Fields
AM parts have come a long way from being used for prototyping and concepts. Today, these parts are increasingly used as part-for-part substitution in demanding fields like medicine and aerospace. In the medical industry, AM technology is used to produce patient-specific implants, surgical tools, and dental crowns, among others. These parts are designed to fit each patient’s unique anatomy, improving the success rates of surgeries and reducing the risk of complications.
In the aerospace industry, AM technology is used to produce parts that can withstand the harsh environments of space, such as rocket nozzles and satellite components. These parts need to be strong, lightweight, and able to withstand extreme temperatures and pressures. AM technology allows manufacturers to produce parts with unique geometries that cannot be produced using traditional manufacturing methods, making it ideal for aerospace applications.
The Importance of Material Quality
In demanding fields like medicine and aerospace, where the quality of the parts produced can mean the difference between life and death, material quality is crucial. AM parts need to be free from discontinuities like porosity, cracking, and delamination, which can compromise the part’s structural integrity. Any discontinuities in the parts can result in catastrophic failure, which is unacceptable in critical applications.
To ensure that AM parts are free from discontinuities, the manufacturing process has to be stable, robust, and repeatable. Manufacturers need to ensure that the parts are produced under optimal conditions to reduce the likelihood of discontinuities. The process needs to be controlled to ensure that each part produced meets the required standards.
Nondestructive Testing (NDT) Technology and Inspection Methods
NDT technology and inspection methods are essential in ensuring that AM parts meet the required standards. NDT is a method of evaluating the properties of a material, component, or system without causing damage or altering the material’s physical properties. NDT techniques can be used to detect any discontinuities in AM parts, ensuring that they are free from defects.
There are several NDT techniques used in the industry, including radiographic testing, ultrasonic testing, magnetic particle testing, liquid penetrant testing, and eddy current testing. Each technique has its advantages and disadvantages, and the choice of technique depends on the type of material and the type of defect being detected.
Radiographic testing, also known as X-ray testing, is commonly used to detect internal defects in metallic parts. The technique involves passing X-rays through the part being tested and capturing the resulting image on a film or digital detector. The resulting image can then be evaluated for any discontinuities, such as porosity or cracking. Radiographic testing, for example, is an effective technique for detecting internal defects in metallic parts. This makes it a useful tool for inspecting complex internal geometries that can be produced using additive manufacturing.
Ultrasonic testing is another commonly used NDT technique. The technique involves sending high-frequency sound waves through the material being tested and measuring the time it takes for the waves to bounce back. The resulting data can be used to evaluate the material’s properties, such as thickness, and detect any discontinuities, such as cracks. However, it is important to note that while ultrasonic testing may have limitations in inspecting complex geometries and rough surfaces of additive parts, it is still a widely used and effective NDT technique for detecting defects in a range of materials. Ultrasonic testing may not be the most suitable technique for inspecting all additive manufactured parts and that other NDT techniques may need to be used in conjunction with ultrasonic testing to ensure that all defects are detected.
Magnetic particle testing is used to detect surface and subsurface cracks in ferromagnetic materials. The technique involves applying a magnetic field to the part being tested and applying magnetic particles to the surface. The particles will be attracted to any areas where the magnetic field is distorted, indicating the presence of a crack. Like ultrasonic inspections surface roughness can be a problem in terms of inspectability and interpretation.it is important to consider the surface preparation of additive manufactured parts before performing NDT inspections to ensure accurate and reliable results.
Liquid penetrant testing is used to detect surface defects, such as cracks and porosity, in non-porous materials. The technique involves applying a liquid penetrant to the surface of the part being tested and allowing it to seep into any defects. The penetrant is then removed, and a developer is applied to the surface, highlighting any defects.Liquid penetrant testing is a widely used technique for detecting surface defects in non-porous materials. However, it is less suitable for use on porous materials such as metal foam or additively manufacture surfaces, where the penetrant can seep into the material and give false results. The technique is also limited to detecting defects that are open to the surface, making it less effective for detecting subsurface defects.
Eddy current testing is used to detect surface and subsurface defects in conductive materials. The technique involves passing an alternating current through a coil, creating a magnetic field. The magnetic field will induce an electrical current in the part being tested, creating a secondary magnetic field. Any changes in the secondary magnetic field can be used to detect any discontinuities in the part.Eddy current testing is a non-destructive technique that can be used to detect surface and subsurface defects in conductive materials. It is particularly useful for detecting defects in thin-walled structures, such as those commonly produced using additive manufacturing. However, the technique is less effective on non-conductive materials such as ceramics and polymers.
Overall, the choice of NDT technique for additive manufactured parts will depend on a variety of factors, including the type of material being inspected, the type of defect being detected, and the cost and time constraints of the inspection process. By using the right NDT technique, manufacturers can ensure that their additive manufactured parts are free from defects and meet the demanding requirements of industries such as aerospace and medicine.
Additive manufacturing technology has come a long way from being used for prototyping and concepts. Today, it is being used as part-for-part substitution in critical industries like medicine and aerospace, where the quality of the parts produced is crucial. To ensure that AM parts meet the required standards, they need to be free from discontinuities, and the manufacturing process has to be stable, robust, and repeatable. NDT technology and inspection methods are essential in detecting any defects in the parts, ensuring that they meet the required standards.
As the technology continues to evolve, the industry will continue to face new challenges. The demand for high-quality parts will only increase, and manufacturers will need to adapt to meet these demands. With continued advancements in NDT technology and inspection methods, the industry can be confident in the quality of AM parts produced, paving the way for a future where AM technology is the go-to manufacturing method for critical applications.
| DT Technique | Advantages | Disadvantages | Suitable Materials | Suitable Defects |
|---|---|---|---|---|
| Radiographic Testing | Detects internal defects | Requires special equipment and trained personnel; harmful to health and the environment | All materials | Porosity, cracking |
| Ultrasonic Testing | Non-destructive; high accuracy and resolution; can detect both internal and surface defects | May not be suitable for complex geometries and rough surfaces | All materials | porosity, cracks |
| Magnetic Particle Testing | Detects surface and subsurface cracks in ferromagnetic materials; relatively simple and cost-effective | Only suitable for ferromagnetic materials; surface preparation is critical; requires trained personnel | Ferromagnetic materials | Surface and subsurface cracks |
| Liquid Penetrant Testing | Detects surface defects in non-porous materials; simple and cost-effective | Only suitable for non-porous materials; requires proper surface preparation and cleaning; may produce false indications | Non-porous materials | Surface defects such as cracks, porosity |
| Eddy Current Testing | Detects surface and subsurface defects in conductive materials; can detect small defects | Only suitable for conductive materials; requires trained personnel; may produce false indications | Conductive materials | Surface and subsurface defects |