.webp){kind=icon}
.svg){kind=icon}
WENZEL industrial computed tomography at Nidec Machine Tool
WENZEL America and NIDEC continue their partnership to exploit the potential of eXact U to investigate WENZEL computer tomographs researching additive manufacturing with directed energy capture (DED). This system, integrated into NIDEC Machine Tool America's LAMDA system, uses cutting-edge technology to process even the hardest metals.
Since the introduction of additive manufacturing in Japan in 1987, numerous new applications have developed that use various technologies to turn CAD files into physical 3D objects. Today, even highly complex objects and shapes are recognized and widely used in many industries. In this article, we look at directed energy separation (DED) and the ways to use this technology to ensure product quality.
LP-DED (Laser Powder-Directed Energy Deposition) is a powerful additive manufacturing (AM) process in which a focused laser beam melts and combines metal powder layer by layer to produce a desired 3D object. The metal powder is introduced into the molten pool created by the laser via a nozzle, which enables precise material placement and the production of complex design features.
Compared to other AM processes such as powder bed melting, LP-DED offers greater flexibility as it can work directly on existing components. This makes the process ideal for repairs, adding features to existing parts, and producing functionally tiered structures where material properties vary within the object. LP-DED can also process a wider range of materials, including metals that are difficult to process with other processes.
A key advantage of NIDEC's LAMDA LP-DED system is the ability to carry out large-scale additive manufacturing of metals without the use of a complete environmental chamber. This is achieved through local shielding — a gas housing that surrounds the coating area. This shielding minimizes the interaction of the laser and metal powder with the environment, reducing the risk of vapors, splashes, and oxidation. This not only simplifies set-up, but also reduces costs and energy consumption compared to chamber-based AM systems.
A significant step forward is NIDEC's use of monitoring and real-time feedback to control the process. In combination with artificial intelligence and machine learning, LAMDA systems can identify anomalies early on and automatically stop the process before the component is damaged.
Thanks to the combination of a variety of materials, repair options and the ability to manufacture on a large scale, LP-DED is a valuable tool for various industries such as aerospace, automotive and energy sectors. As research and development continues to improve process control and material understanding, LP-DED is expected to play an even more significant role in the future of additive manufacturing.
Industrial computed tomography (CT) is an advanced, non-destructive testing method that enables detailed internal views of components and even penetrates materials such as metal and plastic. In combination with suitable software, industrial CT becomes a powerful tool for engineering and measurement technology. CT technology has existed for decades and enables rapid inspections, makes internal structures visible that remain hidden with conventional measurement methods, and thus improves cost efficiency and productivity. In contrast to other testing machines, CT offers an in-depth analysis of internal structures, material properties and potential defects.
CT systems are invaluable in materials testing and offer a unique opportunity to uncover hidden features in metals. With DED (Directed Energy Deposition) technology in particular, it is crucial to know the quality of the material when adding new features to existing parts or creating functionally graded structures in which the material properties vary within the object. CT systems measure material density precisely, which allows conclusions to be drawn about strength and durability. They can also detect pores that could impair the performance of the material and cracks that are not visible to the naked eye but could cause the product to fail catastrophically.
Another important application of CT systems is to check the dimensional accuracy of a component to ensure that it meets the specified dimensions and tolerances. This ability is essential in precision industries. This can be achieved through a target/actual comparison, in which the CAD drawing of the part is compared with the actual CT scan of the same part. In cases where CAD data is not available, scan data of a reference part can also be compared with the scan data of the part to be tested.
The most common defects that occur with DED (Directed Energy Deposition) are porosity and cracks. These can be caused by contaminants that are trapped in the component during the additive manufacturing process. When analyzing the DED process, potential defects such as burr formation, cavities, cracks, porosity, surface lines, and increased surface roughness can be identified. Such separation defects pose significant challenges in both PBF and DED processes, and repairing them is a complex and demanding task. Fortunately, by measuring and detecting these defects, the latest CT software provides valuable insights into the necessary corrections to ensure the highest quality products.
Porosity and cavities are common problems with additively manufactured cast and molded parts. They are often caused by air or gas pockets that are trapped in the metal during solidification, or from the shrinkage of the metal that leaves cavities inside it, which is known as shrinkage porosity. Because porosity consists of trapped air, CT analysis can identify it as an area of lower density, making detection easier.
Suitable software is crucial for the precise determination of porosity due to density fluctuations. World Cup | PointMaster by WENZEL is a CT analysis tool that identifies porosities with a simple click. It allows the quality assurance engineer to easily measure and visualize the size, shape, and possible clusters of porosities. The operator can set a range for the porosity sizes and color code them for easy identification to prevent the detection of porosities that are too small. CT is particularly effective in revealing trapped porosities in printed parts. Types of porosity include continuous porosity, which extends over the entire part, and blind porosity, which typically occurs on a surface of the part. Porosity detection should focus on worked areas and other critical, heavily stressed sections.
The CT system has certain limitations in terms of resolution and penetration performance. The selection of the X-ray tube, the detector and the positioning of the object in the scan area significantly influence the maximum magnification and resolution. Some CT systems offer scan field extensions that make it possible to merge multiple fields to capture a larger scan area. The resolution is also determined by the precision of the turntable, which determines the layer thickness of the scan.
The voxel size (v) of a tomographic reconstruction can be calculated using the formula v = p M (1), where p is the detector pixel distance and M is the ratio of SOD (source-to-object distance) and SDD (source-to-detector distance). However, the actual value of v is also determined by factors such as the drift of the X-ray source, thermal expansion of the CT components, the inclination of the detector and the slide, and other influences.
With the optimal setting, we should be able to detect and measure cavities, blockages and cracks ranging from 21µm to 26µm with a high degree of certainty. With a precise angle, we can detect them even better. When measuring edges, the density transition should be no more than three pixels, and the sharpness of an edge should ideally be around 3 to 4 pixels.
The search for the causes of crack formation and the exact phase in the manufacturing process can be extremely complex. Finding the crack and observing its propagation through the object can provide decisive clues to solve the problem.
In many cases, high-resolution CT technology, such as the eXACT system, is required to precisely identify cracks in printed parts. Cracks are often irregular and can run through a component in various directions. It is particularly important to identify cracks caused by uneven cooling during the manufacturing process. Similar to porosities, these cracks can be visualized and colored with the WM | PointMaster software to analyze material properties and the manufacturing process. CT technology is particularly useful for studying crack migration in parts that have undergone tensile tests.
A notable example of the use of CT in studying crack migration is the analysis of ballistic tests on protective vests. It can be shown how polyurethane layers separate after a ballistic test while maintaining the overall integrity of the material and being able to resist projectiles such as bullets or shrapnel chips.
The WM | PointMaster software can provide sub-voxel measurements of CT scans to evaluate shape, strength, and the effects of cracks on the material.
CT scanning provides detailed data about the inner and outer sides of the most complex parts. After demolding, plastic parts are often deformed due to shrinkage and signs of distortion. To counteract these effects, compensated molding is usually carried out during the injection molding process. The plastic part is first brought into a “wrong” shape so that, after cooling, shrinking and warping, it becomes the desired final shape and comes as close as possible to the desired shape.
Traditionally, tool geometry is adjusted through iterative post-processing (milling, grinding or eroding). However, this process is complex and may result in the mold no longer being able to be reused.
With virtual deformation, the deformation specifications can be derived from simulation systems or measurement results of actually scanned components. This allows WM | PointMaster to automatically calculate the deformation result, taking into account factors such as local volumes, shrinkage and the toolmaker's experience. The automatically calculated, deformation-compensated geometry is then processed using the powerful surface return functions of WM | PointMaster and World Cup | Quartis converted into CAD surface models, into which the existing tool data is integrated.
For critical, additively manufactured components, the WENZEL EXACT series offers precise measurements of internal and external geometry as well as reliable fault detection. Watch this short video for a graphical overview of this valuable tool.
.webp){kind=small}
