Printed Quality: Enabling yield improvement in 3D printing process chain
Breaking new ground in production to be one step ahead—such is the ambition of numerous companies. In light of the additive manufacturing trend, this may be possible. Dr. Marcin Bauza, Dr. Claus Hermannstädter, and Dr. Robert Zarnetta explain how to support pioneering entrepreneurs in their efforts.
Ever since the first companies have been able to shape metal powders by means of 3D printing or melting, more and more companies want to supplement their conventional production processes with additive methods. How quickly and comprehensively additive manufacturing of metal parts will be established depends to a large extent on the yield—the proportion of good parts—at the end of the process chain. Dr. Claus Hermannstädter, head of strategy and business development; Dr. Marcin Bauza, director of new technology and innovation, both Carl Zeiss Industrial Metrology Business Group; and Dr. Robert Zarnetta, head of business sector manufacturing and assembly of Carl Zeiss Microscopy Business Group, explain how to best enable process improvements within additive manufacturing across the entire value chain.
1. Why does 3D printing play an increasingly important role for metrology?
Dr. Hermannstädter: One of the greatest potentials of additive manufacturing is the opportunity to create components with unique geometries and structures that are impossible to manufacture so far, and therefore, can take on completely new functions. From medical implants to aircraft turbines, the variety of possible applications for industrial 3D printing is very promising. A third of the companies in the mechanical and machine building, automotive, aerospace, pharmaceutical, consumer electronics, and medical technology industries are already working on additive manufacturing. We, therefore, firmly assume that increasing numbers of critical components will come from the printer in the near future. How efficient this technology is depends strongly on how well the additive manufacturing process chain is understood and controlled, and how good the feedback is. It is important to have a broad portfolio of solutions to ensure the required quality of additively manufactured parts—from material testing to final inspection. In addition, it’s important to work closely with many partners, including research institutes and users of additive manufacturing technologies, to expand our understanding of processes and know-how in this field. Having a combination of decades worth of experience in microscopy, material research and metrology, will help to better advise customers and qualify work in setting assurance standards and norms.
Dr. Bauza: Even though the technology is currently being hyped in view of the new opportunities it offers, for example in terms of lightweight construction and resource savings, it is still in its infancy. The industry is still far from guaranteeing the high reproducibility and reliability known from traditional manufacturing processes. Additive manufacturing has only a fraction of compounded know-how compared to conventional subtractive methods. Therefore, it requires a lot of investigation within every step of the process chain to enable optimal part printing. Gaining this process knowledge might take as long as several years. In other words: there is still much to be done about trial and error. However, the number of iteration loops can be significantly reduced with detailed analysis of materials and processes. It’s critical to have significant expertise combined with unique technology, allowing deeper understanding and detailed monitoring of the majority of process steps, such as material powder characterization, i.e. powder size and form, as well as distribution analysis, crystallographic analysis, build defects, internal and external surface analysis, internal and external dimensional analysis. They allow correlation between process steps and understanding the influence of post build treatments, such as heat treatment on final dimensional characteristics. Each of those steps can have a significant impact on the overall yield, therefore, correlating obtained information across each of the process steps can significantly improve overall part performance.
2. How best do you support companies in ensuring the quality of additive-manufactured metal parts and optimizing processes?
Dr. Zarnetta: As already mentioned, it is important to have a very broad portfolio of solutions that are used before and after the printing process. For example, companies often characterize powder with light and electron microscopes. This is an important issue for quality assurance, because the powder-bed fusion process requires the use of powders with very strict specifications in terms of size, shape, and material properties. As experience shows, deviations from these parameters have a great impact on the quality of the final product. Scanning electron microscopes are used by companies to check whether the powder contains oxidized particles, which could cause problems when melting in the 3D printer, or analyze the recycled powders, if they still can be used for high quality builds. To further aid the analysis, correlative techniques to enable customers to close the gap between light and electron microscopy have been developed, allowing better understanding of material characteristics. Detected abnormalities in the powder at macro scale can then be investigated at the micro level with pinpoint localization transferred to electron microscope or X-ray computed tomograph, enabling hassle-free nanometer range analysis. This helps customers to evaluate the powder quality faster and prevent material-related defects in the build stage.
Dr. Bauza: In addition to the microscopes, also other metrology solutions play a role in additive manufacturing. For example, errors in the printing process can be investigated with 3D optical scanners, both white light and X-ray based. This means that companies receive a volume model of the entire component within a few minutes and can then easily compare these actual data with the target data from the CAD model. This information can be also verified across post-printing steps, allowing analysis of parts in “as build” state, then heat treated state, and finally removed from the build plate. Understanding how much the post-process can influence the final part dimensional characteristic is critical in setting up build recipe and drawing conclusions about process parameters. Such tests can be performed with classic tactile CMMs, as well as utilizing the latest CT X-ray technology. In addition, the surface roughness of additive manufactured parts could be responsible for the failure of the component (crack propagation), which should also be reviewed. There are solutions for external and internal surfaces, using again optical white light and X-ray based systems. Furthermore, all test information from across the process chain can be combined with quality data management software, enabling detailed statistical evaluation. The above technologies are already used within classic manufacturing environments, and the experience and expertise can be leveraged, offering a fast track for additive manufacturing process development and overall yield improvement.
Where are we going? How do you intend to further advance the process stability and quality of additive components?
Dr. Hermannstädter: Some manufacturers of 3D printers are starting to monitor the printing process themselves. We are currently looking closely at these developments. We will certainly create interfaces to include in-process data. Then users of additive manufacturing can correlate a variety of quality and measurement data with each other and find errors faster. But, of course, we see further potential for improvement. Our goal is to develop a self-learning solution that, based on the quality data already acquired during the assembly of the metal parts in the printer, decides whether detected defects might affect the performance of the final product or not. Such a solution will then provide process feedback in the spirit of Industry 4.0.
Dr. Zarnetta: And not only that. By bringing together and evaluating all the information from the material properties of the metal powder to the ambient conditions in the printer, and the microstructure of the components, we will even influence upstream processes, and, for example, enable designers to develop models that can be produced without any problems with the same functional performance to avoid defects before they occur. Q
Dr. Claus Hermannstädter is responsible for strategy and business development of the Carl Zeiss Industrial Metrology Business and leads the customer relationship excellence program.
Dr. Marcin B. Bauza is responsible for New Technology and Innovation of the Carl Zeiss Industrial Metrology Business, focusing on high-speed in-line metrology and surface inspection solutions, and is the head of ZEISS Additive Manufacturing Process and Control. He received his PhD in mechanical engineering from the University of North Carolina in Charlotte and his Executive MBA with concentration on strategy from Duke University. Before joining ZEISS he co-founded a start-up, focusing on advanced motion and sensing solutions and was focused on technology and business development.
Dr. Robert Zarnetta is responsible for the business sector Manufacturing & Assembly at the Carl Zeiss Microscopy Business and, thus, is responsible for all microscopy applications for industry customers across all technology platforms of light, electron, and X-ray microscopy.