Additive Manufacturing (3D Printing)
I recently came across an article about the first 3D printed house hitting the market in New York. While I’ve seen a lot of information regarding the benefits of 3D printing structures, mainly that it less expensive and faster than traditional construction methods, this was the first time I had seen a house that was actually 3D printed and being sold. It reminded me how quickly the 3D printing industry is expanding. The most recent edition of NFPA 1, Fire Code includes new language related to 3D printing or, more specifically, additive manufacturing. One major distinction between the article and the language in the Fire Code is that the article is talking about structures that are 3D printed where as the NFPA 1 language addresses buildings that house additive manufacturing operations. Perhaps, as 3D printed structures become more popular the codes and standards may need to address unique requirements for them. Will there be special considerations when inspecting these types of structures, or will there be a limitation on the types of materials that can be used to print structures? Right now, the focus of requirements in the Fire Code is on protecting buildings that conduct additive manufacturing operations.
Although you may have heard the term “3D printing” the Fire Code addresses “additive manufacturing.” Sometimes these are used interchangeably, but there is a difference. Additive manufacturing is the more inclusive term that encompasses all types of manufacturing that produce a product by adding material. Traditional manufacturing methods produce a product by removing material. The process starts with a block of material and pieces are removed and shaped until the desired shape is achieved. Here you can see how nails are made in a traditional manufacturing process. In additive manufacturing the process starts with nothing and material is added one thin layer at a time. 3D printing is one subset of additive manufacturing, but there are other types such as direct metal laser melting.
The Fire Code has two separate sets of requirements for additive manufacturing based on the associated hazard: industrial additive manufacturing and nonindustrial additive manufacturing.
Industrial Additive Manufacturing
Industrial additive manufacturing processes are those operations that meet one of the following conditions:
- Use combustible powders or metals
- Use an inert gas supply
- Have a combustible dust collection system
- Create a hazardous electrical classification area outside of the equipment
Nonindustrial Additive Manufacturing
Nonindustrial additive manufacturing processes are those operations that meet all of the following:
- Do not use an inert gas supply
- Do not have a combustible dust collection system
- Do not create a hazardous electrical classification area outside of the equipment
Differences in Requirements
The use of combustible powders or metals, the use of an inert gas supply, or the creation of a hazardous electrical classification area outside of the equipment results in a higher level of hazard anticipated with industrial additive manufacturing than with nonindustrial additive manufacturing. Therefore, the requirements for industrial additive manufacturing and nonindustrial additive manufacturing are significantly different.
Location of Additive Manufacturing
Nonindustrial additive manufacturing is permitted in all occupancy groups whereas industrial additive manufacturing is only permitted to be conducted in the occupancy groups associated with the manufacturing operations and as permitted by the maximum allowable quantity tables in NFPA 400. The fire and explosion hazards associated with industrial additive manufacturing are more aligned with the hazards you would see in a traditional manufacturing setting. However, many of those same hazards will not be found in nonindustrial additive manufacturing because of the differences in the operations. Therefore, those operations are permitted in a wider range of occupancies.
The nonindustrial additive manufacturing operations are only permitted to use plastic filament production materials that are listed with the 3D printer and that are identified in the manufacturer’s instructions. The powders used in industrial additive manufacturing must be tested for combustibility in accordance with NFPA 484, Standard for Combustible Metals or NFPA 652, Standard on the Fundamentals of Combustible Dust. For industrial additive manufacturing operations additional requirements may need to be followed depending on the material used for production. For example, if a combustible, nonmetallic powder is used, then the operation must also comply with Chapter 40 of NFPA 1 and NFPA 654, Standard for the Prevention of Fire and Dust Explosions from the Manufacturing, Processing and Handling of Combustible Particulate Solids. Since these types of combustible materials are not permitted in nonindustrial additive manufacturing there are no similar requirements for those types of operations.
Industrial additive manufacturing processes that use inert gasses must have a gas detection system in all indoor areas where the inert gas is present. The gas sensors must be provided in areas where the gas is expected to accumulate and other locations where the AHJ requires them. The system must activate a supervisory audible and visible alarm upon detection of inert gas at the 8-hour time-weighted average concentration. There must also be an audible and visible alarm within the room or immediate area where the system is located and must automatically shut off the flow of the inert gas to the 3D printing equipment when the system detects inert gas at the threshold limit value-short-term exposure limit concentration. There are no comparable requirements for nonindustrial additive manufacturing since those processes are not permitted to use inert gasses.
This summarizes the major differences between the two types of additive manufacturing addressed in the Fire Code. For specific details, you can view chapter 46 in NFPA 1. This new chapter provides a starting point for a technology that is changing rapidly and gaining in popularity every day.
Have you started seeing additive manufacturing in your jurisdictions? What are some of the challenges you’ve faced when it comes to this technology?