by Kim Färnlund, Metallurgist at AMEXCI.
“Those who cannot remember the past are condemned to repeat it”.– George Santayana 1905
Recognizing the enormous impact and unprecedented possibilities that Additive Manufacturing (AM) technologies present, the AM Strategic Research Agenda (SRA) highlights key strategic areas that are vital for success within the field of AM that were quickly recognized and adapted by the AM community in Sweden. Due to increased global competition and the rapid development of a variety of advanced manufacturing technologies, such as AM, and the pressure to push the envelope, other related topics like EH&S, have been left aside. Fortunately, we exist in an era in which occupational health and safety is one of the foremost recognized industrial measures of success. Therefore, the SRA highlights occupational health issues as one of three key strategic areas that are vital for success in the field of AM, alongside design competence and quality and productivity.
Additive Manufacturing – the challenges of industrialization
As true industrialization of AM is rapidly approaching, with leaps made to productivity, scalability, and economic viability, the understanding of health aspects has not experienced the same level of advancements. While health effects of exposure to different alloying elements, such as nickel, cobalt, and chromium, and chemicals, polymer additives, and solvents are well-known, as is the explosion risk associated with some powders, very little research has been done on effects of exposure to the particle size ranges that are found in the metal AM industry. In particular, long-term effects and long-term exposure of small doses that are possibly experienced by personnel working with the AM machines are virtually unexplored territories.
The same can be said about exposure risks posed by specific operations in the daily work, since measurements have rarely been done for particles in the sub-micron ranges. By extension, specific guidelines that describe the exposure limits or safety equipment requirements are few to none and sometimes based on the idea that some limits are better than no limits and set through assumptions made from other fields. This void of know-how can lead to a division within the AM community, where the materials and processes are either regarded as completely harmless or as a potential occupational health risk.
Tackling the challenges of work environment health and safety
Adamant not to be subject to forgetting industrial history that is littered with tragic examples, such as the unprotected use of asbestos or silicosis as an effect from breathing in stone dust, AMEXCI has made it a mission to be a driving force for a safer AM industry. Working with health and safety as a core topic meant joining up with leading institutes, researchers, and industries in Sweden to explore the EH&S area and contribute to the knowledge base surrounding occupational health and safety in the field of AM. AMEXCI is currently engaged in two collaborative research projects, HÄMAT2 and NanoSafety, both of which are looking into different areas of improving the working environment in AM and to shed a light on the potential health risks.
The AMEXCI team has been at the disposal for these projects, where particle measurements have been done both by collecting dust that fall on surfaces, using impactors and particle collection equipment, and collecting powder samples. Wearable particle collectors have been attached to the operators for tracking exposure risks in the daily work and to find out what operations are the potentially most hazardous, and stationary equipment have been used to collect larger amounts of particles over a longer time, up to a week. Additionally, the AMEXCI team perform voluntary blood and urine tests up to twice a year, as well as spirometry, to check for changes and potential accumulation of alloys and chemicals over the span of a week.
One of the key challenges met in these two projects is collecting adequate amounts of relevant material. While it is simple to acquire a powder sample from the raw material, acquiring samples of the biproducts created in the AM processes has proven significantly more challenging. The fumes created by the AM process, the so-called condensate, is of particular interest as it is expected to be of a respiratory size, meaning it could potentially travel deep into the lung if inhaled. However, particles of this size are difficult to collect, and it is where the efforts are currently being put.
Good working practices within the Additive Manufacturing industry
By nature, a comprehensive understanding of the health effects of exposure to these materials and long-term effects will not be finalized for a long time, but initial results indicate that some materials are absorbed by the body, but not necessarily all are detected. Therefore, some might accumulate over time and cause an increased risk for long term irritation and inflammation. This is a clear indicator that until more data has been collected to generate a better understanding, it is recommended to use purpose-specific safety equipment when performing certain operations in areas where fine powders can get airborne.
Particle concentrations appear to spike not only when work is being done on the machines with operations such as adding or removing powder and sieving the powder, but also when cleaning the working areas. In particular, the latter can be easily missed as the powder cannot be seen, but the number of particles that get airborne even from a seemingly clean surface can be in the hundreds of thousands per cm3. It is therefore paramount that some safety equipment is used also when cleaning.
Drawing on the knowledge from experienced ventilation industries, such as Absolent and Nederman, the singularly most effective way to reduce exposure to particles is purpose-specific ventilation that is optimized for the setup and the machine room. Good airflow transports particles away from the operator and refreshes the air in the room and prevents build-up over time.
There is yet much research to be done and in order to not fall into the trap described by the striking words by George Santayana, we must continuously strive to improve, deepen our understanding, and remember our past, to ensure a thriving future.