Milan Polytechnic’s AddMe Lab shows off progress in process monitoring AI

We know the common places. Compared to other countries in Italy there are fewer research funds, there is less coordination at the national level and it is difficult to emerge with new technologies. The visit to the AddMe Lab of the Polytechnic University of Milan, where Professor Bianca Maria Colosimo and her team of engineers from the Department of Mechanics work on some of the most innovative aspects of 3D printing of metals, has partially dispelled them. It also confirmed other clichés with more positive connotations, including how Italian ingenuity can make up for some organizational and macroeconomic weaknesses.

The research projects of the Department of Mechanical Engineering of the Polytechnic of Milan (or PoliMi) in the field of 3D printing of metals are on a par with those carried out by universities that enjoy even greater visibility such as MIT, Fraunhofer and ETH. On the contrary, one aspect where they may even hold a lead – something that everyone would like but that nobody has managed to develop properly – is the use of big data analysis systems in the process simulation and monitoring phases. Precisely this is the main area of study of Professor Colosimo and her team, along with a wide range of other projects focused on hardware and industrial applications of additive manufacturing. Below we tell you the main ones. Make yourself comfortable because there are quite a few.

Leadership in AI for the AM process

The AddMe Lab has access to all the main technologies for the additive manufacturing of metals, then powder bed fusion (laser and electron beam), both internally developed and commercial systems, directed energy deposition (both with wire and powder) and, soon, binder jetting thanks to a new system coming from ExOne and the newborn Desktop Metal. Other internally developed systems work on ceramic materials with extrusion processes derivated from CIM (Ceramics Injection Molding), and even on continuous fiber composites.

I meet Bianca Maria Colosimo in her office. It may surprise some that she is a woman, given that industrial manufacturing is a predominantly male environment globally, but in Italy there are actually many women working in cutting-edge segments of additive manufacturing, both academically and industrially. What is perhaps most surprising is her genuine enthusiasm, since we tend to think of academic experts and engineers as somewhat overly serious people.

“The main objective we set ourselves is to try to have a well-rounded approach to manufacturing – she begins. As Milan Polytechnic we study the problems concerning the design, choice of materials, simulation, monitoring and real-time control of the process, in the context of the Industry 4.0 framework. Our group, in particular,r is very focused on these last two themes, and on all related issues. The main theme on which we are investing in is the machine’s sensorization, in order to catch, avoid and correct production defects in real time.”

One element that needs to be kept under tight control is the porosity of the component being printed. Once the component has been completed it becomes difficult to analyze it, even with tomographic systems, so it is est to notice it during the printing phase. Reducing process instability, and therefore the number of defective parts is one of the most important keys to reducing the costs of 3D printing in general.

“There are different levels at which we can operate,” continues Professor Colosimo, “an idea is to link the process parameters directly to the” signature” of the process that is observed with cameras and sensors in real time. This signature is in turn linked to the quality of the finished product. Basically, instead of making a lot of samples and measuring them, as we normally do, we choose the process parameters that make the process signature stable and similar to the desired one. This can be done using the signals that the machine already makes available or by adding other sensors. ”

All major manufacturers of industrial 3D printers are developing these new process monitoring systems. One of their limitations, explains Professor Colosimo, is that they have not yet fully integrated intelligent data analysis systems in their software. The commercial process monitoring that exists today makes it possible to gather a lot of information, but when it comes to making a decision based on the data collected it is still limited. “For example – she explains – you can look at the meltpool in every point of the layer but you are not yet able to analyze this data in real time to understand if something unusual is occurring.”

Before assessing and correcting any imperfections, monitoring systems must be able to reduce the number of false alarms. For this, you need to have data analysis strategies, which must be in real-time, fast, lean, and also reliable. “This requires a lot of research,” says the Professor. “We need to reduce the distance between the different skills needed to solve the typical problem of manufacturing 4.0: take advantage of the huge amount of data available to improve production. Historically, those who design and manufacture machines do not have great expertise in big data analysis and machine learning. There is, therefore, a gap to be filled through collaborations as it is a very multidisciplinary type of problem,” she explains.

Addressing these challenges would enable more AM industrialization. AddMe researchers examined many different cases. For example, a spot that remains too hot resulting in degenerating geometry problems; or an analysis of the melting process with respect to the intensity of the sparks to understand if too much or too little energy is applied, causing more internal porosity. Other studies concern the analysis of the microstructure of a 3D part. This could in the future also lead to other very interesting applications such as the possibility of varying the microstructure of different areas of the same part, depending on the stress requirements, and then modifying – locally and digitally – the mechanical properties of the material itself.

AddMe Lab some Hardware

This cutting-edge software research is possible thanks to the great amount of work done on additive hardware. The laboratory has both commercial systems such as an Arcam A2 (EBM) and a Renishaw AM 250  (SLM) system, as well as several systems developed internally to conduct more specific research and development on the process and materials.

A system was developed internally by Professor Previtali’s group. He is an expert in laser processes in the Department of Mechanics, to study (and use) the directed energy deposition process, with a deposition head positioned on an ABB robotic arm. This system allows creating complex parts on a tilting plane. Other internally developed systems use different selective laser fusion (SLM) approaches. One, called Powerful, is used to study the materials through a standard SLM process and a very small powder bed, to allow the use of even very small amounts of metallic powders. Another, Penelope, integrates additive and subtractive functionalities and is used to develop a process that allows correcting in-situ defects. Finally, there is Efesto which is used for ceramic materials through an evolution of CIM processes. In practice, the ceramic materials mixed with a binder are extruded and deposited to form green parts, then sintered in a furnace. 3D printing of other ceramic materials (cement and clay) and even continuous fiber composites are carried out and studied through a system based on two collaborating robotic arms.

Searching for research

The Polytechnic University of Milan – PoliMi – is a technical university with over 43,000 students. In this segment, it is high in international rankings. It is considered the first university in Italy for engineering and technology, the sixth in Europe (in a ranking that also includes institutions such as Cambridge and Oxford), and the seventeenth in the world. At the general ranking level, the institute suffers a bit from the relationship between students and teachers, which is about 1:33.

This cutting-edge knowledge has allowed the AddMe Lab to become part of important research projects, both Italian and European. The first is the AMATHO project, funded by the European community within the cleansky2 program, which involves the study of new printing solutions for large objects. In particular, this project studies innovative solutions for 3D printing the gearbox of the convertiplane, a hybrid between aircraft and helicopter developed by Leonardo (a company that is part of the Finmeccanica group).

A second project co-financed by the Lombardy Region sees the collaboration of many companies interested in the potential of the additive. The project, named Metal ADditivE for LOmbardy (MADE4LO), aims to develop a new model of factory based on additive manufacturing, digital networks and processes. Launched with a budget of 6.6 million dollars, it sees among the participants, in addition to the Polytechnic University of Milan and the University of Pavia, large companies such as Tenova, BLM, and GF Machining Solutions and six SMEs: TTM Laser, 3D-NT, GFM, Fubri , Co. Stamp, and Officine Meccaniche G. Lafranconi.

Finally, the forecast is that of an increasing number of loans to be dedicated to add-ons in the new Horizon Europe program. “Recently – confirms Prof. Colosimo – there was an escalation. Today additive is everywhere: it is experienced as a technology to invest in. The biggest challenge is the change in scale in terms of market size.”

The AddMe Lab also collaborates with many other universities: it has active projects with the John Hart group at MIT, with Georgia Tech, ETH, with the European Space Agency (ESA) and with the Italian Space Agency (ASI) for studying the potential of additive technology in space applications.

PoliMi is also part of a network with ETH, Chalmers, Delft and Aachen, in a project called Idea League, where the themes of advanced manufacturing are of interest to all partners. On the same topic, collaborations are beginning with China, which is increasingly strong and in particular with the prestigious Tsinghua University, which will open an Innovationhub in PoliMi. In December, a new master will be co-organized with Rina Consulting – CSM (Materials Development Center) – on Additive Manufacturing for metallic materials.

These are some of the main things that emerged during the meeting with Professor Bianca Maria Colosimo. The future promises to be really intense and we are only at the beginning. “They are all there, ready. There is a part of skeptics and a part of ‘believers’, “concludes the Professor. It is necessary to complete the transition to sectors that will start to achieve even more important numbers than aerospace and medical. The research part remains very active because AM is an interesting process on which there is still a lot to be said. And to be done.”