According to The Wohler’s Report 2018, sales of metal AM systems increased by nearly 80% between 2016 and 2017, making metal AM a key driver in the overall adoption of AM technologies and systems intended for industrial applications . However, although AM has the potential to transform modern industrial production, it also raises new considerations for manufacturers and users that include potential safety issues.
The introduction of Additive Manufacturing into mainstream manufacturing brings with it new safety issues concerning workplace safety, health and the environment. In general, these safety concerns in metal AM facilities can be attributed to one or more of the following sources:
Metal powders used in AM processes are typically microscopic in size (< 100 µm) and often pose toxicity, reactivity, combustibility and instability hazards. Dust clouds, formed for example by the accidental swirling of powders, have the potential to catch fire and explode under certain conditions. Other hazards include health-related risks resulting from inhalation, ingestion or contact with the skin.
Some of the equipment used in metal AM involves potentially hazardous energy sources such as lasers and electron beams. As AM technology evolves, the design of production equipment is becoming more and more complex. Typical equipment hazards include electrical energy hazards, irradiation hazards, entrapment, thermal hazards and others. Some of these hazards can be life threatening if not properly mitigated.
Manufacturing production equipment is often tightly grouped to maximise space utilisation and increase production efficiency, which can result in an unsafe work environment. In addition, certain AM production processes use gases such as argon and nitrogen, which are capable of displacing the ambient air in a localised workspace, thereby potentially depriving operators of sufficient breathable air. The lack of a monitoring system for safe oxygen levels can have catastrophic results on worker safety. Furthermore, the use of reactive powders such as aluminium or titanium has led to debates among authorities having jurisdiction (AHJs) and code officials regarding the most suitable types of fire suppression systems. Robust facility design and safe work practices are thus critical to achieving overall safety.
Besides the risk to human health and safety, metal AM production can also contribute to environmental degradation. For example, if not properly designed, metal AM workplace ventilation systems can exhaust contaminated gases and toxic compounds, impacting atmospheric air quality. The improper disposal of metal AM waste materials can contaminate soil and groundwater reserves. This can have a potentially adverse effect on plants, animals and aquatic life.
Safety incidents involving metal powder
Unfortunately, the true scale and scope of the inherent risk posed by the potentially explosive nature of dust formed from the metal powders used as the feedstock in AM have been amply demonstrated in a number of factory and workplace incidents, involving fires or explosions directly linked with powdered metals. Just a few examples are:
A 2013 fire and explosion at a Massachusetts Additive Manufacturing
company, which injured one employee, was traced to the ignition of titanium and aluminium powder. The U.S. Occupational Safety and Health Administration (OSHA) ordered the company to pay nearly $65,000 in penalties for failing to eliminate known sources of potential ignition .
Metal powder plant
A Tennessee-based facility that produced atomised steel and iron powders experienced multiple iron dust flash fires and a hydrogen explosion that led to the loss of the lives of five workers. Workers reported that flash fires were commonplace at the facility, but that they had not been trained to understand the extent of the hazard or how to address it .
Aluminium wheel plant
An explosion at an aluminium wheel plant in Indiana that resulted in one fatality and injured six others was linked to the ignition of finely powdered aluminium in the facility’s dust collection system. A subsequent report on the incident found that inadequate housekeeping in the foundry area and poor maintenance of processing equipment led to the dust accumulation that caused the explosion .
A West Virginia facility that milled and processed scrap titanium and zirconium experienced a fire and explosion attributable to the accumulation of combustible metal dust in a mechanical blender that generated heat and sparks due to poor maintenance. The incident involved three fatalities and injured a contractor working at the facility .
Current landscape – AM standards and regulations
As is often the case with new technologies, efforts to develop standards and regulations applicable to AM processes and equipment are a work in process. Standards development organisations (SDOs) around the world are actively involved in processing the knowledge gained from actual experience in working with AM technologies and developing new standards or revising existing ones to reflect that knowledge. As a result, the standards landscape for metal AM and AM in general is continuously in flux as additive technologies continue to evolve and industry learns more about their effective application.
In an effort to help both SDOs and the AM industry navigate the dynamic standards landscape, the America Makes & ANSI Additive Manufacturing Standardization Collaborative (AMSC) has developed a Standardization Roadmap for Additive Manufacturing . Updated in June 2018, the AMSC Roadmap details all existing AM-related standards as well as AM standards under development. Importantly, the AMSC Roadmap also assesses gaps in current standards and prioritises specific areas in which additional standards development efforts are needed (the AMSC Roadmap is available at the ANSI website for downloading).
But, while extensive efforts to develop relevant standards for various aspects of AM production activities continue, little attention has been paid to safety and environmental issues specifically associated with the use of AM. Instead, AM-related safety issues are currently addressed in accordance with laws and regulations that apply to facilities and equipment across the manufacturing industry. In the U.S., for example, workplace health and safety falls under the general scope of the Occupational Safety and Health Administration (OSHA). Safety issues related to the transportation and handling of potentially hazardous materials are addressed in both OSHA regulations and those of the U.S. Department of Transportation (DoT), while environmental issues associated with the generation, treatment, storage and disposal of hazardous waste are addressed under the scope of regulations by the Environmental Protection Agency (EPA).
Regulations related to workplace safety or the environment may be more rigorous in some state jurisdictions and may impose stringent limits on activities that contribute to environmental pollution and contamination. Building inspectors and other officials in local jurisdictions may also apply the requirements of specific electrical safety codes or occupancy classification requirements to AM facilities.
But, while compliance with federal, state and local safety and environmental regulations is not optional for adopters of AM technologies, greater clarity is needed on specific actions that operators of AM production facilities can take to help ensure the safety of their workers or to protect the environment.
What UL is finding at AM facilities
At UL, our understanding of the unique safety issues facing AM facilities has developed over the last several years through engagement with various stakeholders in evaluating the potential use of AM technologies in their supply chain. In our experience, the most common safety challenges facing our AM clients include:
Facility design and construction issues
Manufacturing facilities incorporating AM technologies face a higher risk of experiencing hazardous conditions than traditional manufacturing operations. Yet, many of the facilities we have visited or inspected are neither designed nor constructed to help mitigate those specific risks. This is most often the case when manufacturers introduce AM technologies into existing manufacturing facilities designed for conventional production technologies.
Unsafe powder storage and handling practices
We frequently come across practices that fail to account for the unique safety risks associated with the storage and handling of powder feedstock materials used in AM production. Storage containers are often placed in close proximity to heat sources and hot surfaces, or near equipment that can generate ESD or sparks. Workers fail to take sufficient care in unpacking powdered material containers or in transferring them to and from AM production equipment.
Insufficient or inappropriate fire suppression systems
Metal powder fires must be extinguished using appropriate media. Existing manufacturing facilities may only be equipped with conventional sprinkler or fire suppression systems that use water or other substances to extinguish the fire or control its spread. These forms of fire suppression have the potential to actually exacerbate a fire caused by metal powders.
Wrong or inadequate Personal Protective Equipment
The Personal Protective Equipment (PPE) used in Additive Manufacturing facilities should preferably be made of anti-static materials to help minimise charge accumulation and subsequent electrostatic discharge hazards. At the same time, PPE should also be fire- and heat-resistant to protect workers in the event of a fire or explosion. And workers should be equipped with breathing-protection systems that filter out airborne powdered materials, especially when they are subjected to direct exposure to metal powders and residues. All employees should also have received thorough training on safe and effective use as well as in different strategies for PPE usage. But unfortunately, many AM facilities UL inspects fall far short on each of these issues.
General lack of AM-specific safety knowledge
Finally, UL has found a general lack of awareness or understanding on a broad range of safety issues specific to AM production, not only among facility operators and workers but also with AHJs and local officials who are responsible for enforcing federal, state and local regulations and codes. This often leads to confusion, unexpected delays, escalated spending and even frustration for those involved.
Undoubtedly, not every AM facility is characterised by all of these deficiencies. Some facility owners and operators have made great progress in recent years in understanding and addressing the unique safety risks associated with AM. However, as the use of AM technology increases, there is clearly more work to be done to standardise safety practices specific to AM facilities and to help educate producers, regulators, users and the general public about the inherent risks of the process.
How UL is working to address AM safety
UL has been at the forefront of efforts to address safety issues in AM facilities. UL professionals have been participants in AMSC activities since the collaborative’s founding in March 2016. Our team also made significant contributions to the development of the initial edition of the AMSC Roadmap published in February 2017, as well as the second edition published in June 2018. We are also actively involved with ASTM F42 Subcommittee on EHS and the ISO/ASTM TC261 Working Group on EHS and participate in regional working groups for AM standards development.
UL launched its AM Facility Safety Management Program in 2016 to help facility owners and operators develop a comprehensive approach to AM safety. The programme works directly with facilities to develop an AM safety management plan, which evaluates and addresses risks specific to materials, equipment and facilities, employing a four-step process:
Identify the hazards — The programme begins by investigating AM-specific hazards related to fire, explosion and potential toxicity, among others.
Assess the likelihood of occurrence and severity of impacts of each hazard — This step allows for the risk quantification and the prioritisation of mitigation efforts for each identified risk.
Identify methods to eliminate or mitigate hazards — In this step, specific control measures are developed that, when implemented, will eliminate or reduce to an acceptable level the identified hazards and potential effects
Regularly assess compliance with an established safety management plan — The last step involves regularly-scheduled checks to verify ongoing compliance with the plan’s provisions, as well as the plan’s continued validity
To formalise this four-step process, UL published UL 3400, Outline of Investigation for Additive Manufacturing Facility Safety Management. As the first set of guidelines specifically addressing safety issues in AM facilities, the standard can be especially helpful to organisations that are new to AM, or in the early stages of adopting or integrating AM technologies into their facilities. Manufacturers with in-depth experience in AM technologies and production activities can seek certification in accordance with the requirements of UL 3400.
Finally, as part of ongoing efforts to foster the continued development of AM technical and business professionals, UL has established a robust multi-tiered training programme focused on safety. The programme includes advanced hands-on training courses that address AM design set-up, design optimisation, machine set up, part production, post-processing, part inspection, testing and validation and facility and process safety.
A metal AM success story
Today, a number of AM facilities representing the aerospace and defence manufacturing sectors have been certified to UL 3400. One organisation recently certified to UL 3400 helps to illustrate the potential challenges facing the adoption of AM technologies, as well as the value of the approach detailed in the standard. Our client, an aerospace industry leader in the application of metal AM technologies, sought advice on building a state-of-the-art design and manufacturing facility that would effectively bridge the gap between materials research and the manufacturing floor, thereby enabling the company’s engineers to design and produce better quality parts faster and at lower cost.
The path to UL certification gave the company the opportunity to thoroughly evaluate its facility in accordance with the safety practices outlined in UL 3400 and the advanced framework provided by UL’s facility safety services. The evaluation not only served to validate the company’s current safety practices, but also helped to identify improvements needed to make existing safety practices more scalable and resilient, while still supporting the goal of increasing the overall speed and efficiency of product development.
As a result, the company has solidified the basis for its AM production efforts and set the stage for even more advances in the application of AM technologies. Equally importantly, UL 3400 certification has served to assure the company’s industrial partners that the company regards employee safety as its highest priority.
Already well adopted by industry for the creation of prototypes and the small-volume production of high-value parts and components, metal AM technologies are on the verge of transforming our approach to large-scale production operations. Along with the application of other advanced and emerging smart industrial technologies, metal AM has the potential to improve the quality of manufacturing while also reducing production costs, improving time to market and increasing resource conservation.
For its long-term success, however, wider adoption of metal AM technologies heavily depends on an increased focus on the unique health and safety issues that these technologies present. The collaborative efforts of industry and SDOs will be essential in helping to ensure that appropriate safety guidelines and standards for metal AM continue to be developed and evolved which address new and emerging safety challenges in the future.
 Wohlers Report 2018: 3D Printing and Additive Manufacturing State of the Industry. Annual Worldwide Progress Report a report produced by Wohlers Associates, 2018. Web. 27 December 2018. https://wohlersassociates.com/2018report.htm.
 From an OSHA News Release issued on May 20, 2014. Web. 27 December 2018. www.osha.gov/news/newsreleases/region1/05202014.
 Hoeganaes Corporation: Gallatin, TN—Metal Dust Flash Fires and Hydrogen Explosion, a case study prepared by the U.S. Chemical Safety and Hazard Investigation Board, published January 5, 2012. Web. 27 December 2018. https://www.csb.gov/hoeganaes-corporation-fatal-flash-fires/.
 ‘CSD Determines Fatal 2003 Incident at Hayes Lemmerz Plant in Indiana Most Likely Caused by Explosion in Dust Collection System’, news released by the U.S. Chemical Safety and Hazard Investigation Board, October 5, 2005. Web. 27 December 2018. www.csb.gov/csb-determines-fatal-2003-incident-at-hayes-lemmerz-plant-in-indiana-most-likely-caused-by-explosion-in-dust-collection-system-company-did-not-identify-or-control-hazards-of-aluminum-dust/.
 ‘Final Report on AL Solutions Metal Dust Explosion and Fire that Killed Three in West Virginia Leads CSB to Reemphasize Call for OSHA Combustible Dust Standard’, news released issued by the U.S. Chemical Safety and Hazard Investigation Board, July 16, 2014. Web. 27 December 2018. www.csb.gov/final-report-on-al-solutions-metal-dust-explosion-and-fire-that-killed-three-in-west-virginia-leads-csb-to-reemphasize-call-for-osha-combustible-dust-standard-/.
 Standardization Roadmap for Additive Manufacturing, Version 2.0, developed by America Makes and ANSI Additive Manufacturing Standardization Collaborative (AMSC), June 2018. Web. 27 December 2018. www.ansi.org/standards_activities/standards_boards_panels/amsc/.
Balakrishnan V Nair (Balu)
Additive Manufacturing Lead
333 Pfingsten Rd
Balakrishnan V Nair joined UL in 2015 as an AM Development Engineer with more than three decades of hands-on manufacturing industry experience, including design and prototype development of CNC machine tools and control valves manufacturing. He is trained in various AM technologies with a core focus on the safety management of AM processes.
Balu holds a Bachelor of Technology in Mechanical Engineering and a Master of Science in Computer Integrated Manufacturing. He is a member of the ASTM F42 subcommittee on EHS and a member of ISO/ASTM TC261 WG6 and JG69. He is also a Working Group member for Singapore Technical Reference on AM Facility Safety and a member of the Working Group on Combustible Dusts. for the Singapore Chemical Industries Council.