Low-cost 3D printers such as the Creality Ender-3 have made additive manufacturing more accessible to the general public. But food is the only thing people enjoy more than making plastic items to order from the comfort of their homes.
Naturally, these two processes intersect in the form of 3D-printed tools. Unfortunately, the two go together as well as vinegar and bleach. In other words, 3D printed food cans are toxic enough to slowly kill you.
Read on to find out why this is happening and what you can do to get around the problem.
Why isn’t 3D printing safe for food
Plastics, in general, have a really bad reputation for causing long-term adverse effects on health and well-being. There are packages of warnings written on the BPAs, phthalates, and other endocrine disruptors associated with plastic.
But let’s cover up a file The horrors of shrinking genitals of plastics in general and limits the scope of this endeavor to the more pressing toxicological aspects of 3D-printed plastics.
Here are the ways 3D printing makes plastics more unhealthy than they’re accused of, starting with the weird way FDM 3D printers tend to make plastic stuff.
Porous and bacterial colonies
Conventional injection molded plastic is completely airtight because the body is created by forcing the material into a mold under extremely high pressure. The finished surface of these plastic objects shall be smooth and free from any pores or cracks.
On the other hand, 3D-printed objects are made by stacking hundreds and sometimes thousands of layers of plastic, with the internal geometry of the parts themselves hollowed out in many air pockets.
The porous nature of 3D-printed parts makes it a perfect breeding ground for deadly bacteria such as salmonella and E. coli. These pathogens are known to cause chronic disease and are incredibly resilient to most bactericidal agents.
Therefore, food-safe utensils must withstand smooth, non-porous and easy-to-clean surfaces, which 3D-printed utensils lack.
Food safety and particle migration
The concept of particle migration is an important factor in food safety. Several hundred nanometers of particles can be exchanged between solids that interact with each other and with liquids on a microscopic level.
This is the primary mechanism by which toxic substances are transferred and filtered onto 3D printed plastic and then to the food consumed through these utensils.
Factors such as duration of exposure (long-term storage), friction (scraping spoons), temperature (cooking utensils), and reaction of substances (acidic/alkaline food) involved dictate the size of particle migration. That’s why some interactive foods should be stored in glass jars but are still fine when eaten from metal utensils.
Copper nozzles are toxic
Things get really hot at the end of work for a 3D printer. Your 3D models are turned into physical parts by a molten fuse that is forced out of the hot tip components. Among these, the wick is in close contact with the heat sink and the nozzle.
The former are usually made of stainless steel, so the risk of toxic substances entering the wick is minimal. However, the stock nozzle is usually made of brass, which has been known to leach trace amounts of lead into the wick.
This is definitely a taboo from a health and safety perspective.
What about the rest of the 3D printer?
The copper extruder gears found in most common 3D printers work by applying massive amounts of pressure and friction to the filament. In addition to the brass nozzle, it can also filter lead into 3D-printed plastic.
Most 3D printers also have tubes lined with PTFE between the extruder and the hot tip components. While these materials are food safe, those used in 3D printers contain lubricating additives, which can be toxic.
Other components such as the design surface, filament coil, and lubricant used in the 3D printer are additional methods of transferring harmful substances into the printed parts. Making your 3D printer truly food grade is undoubtedly a hard endeavor.
Most bristles are not food safe
Although PLA is described as biodegradable filaments made from sugars found in corn or sugarcane, various brands offer various additives to enhance the printability, durability, and other physical properties of the printed parts. These additives can be toxic, making the printed parts unsafe for food handling.
The US Food and Drug Administration (FDA) issues food safety approvals for popular sutures. This is a great starting point for figuring out which filaments can be used for printing tools.
However, it is advisable to check approval on a per-lead basis. Despite the concerns surrounding printed ABS parts leaching styrene into food, a lot of commercial ABS filaments receive the FDA nod, while some PLA filaments do not thanks to the specific color pigment used.
Just because a certain brand of ABS is certified as food-safe, you can’t assume the compliment extends to ABS strings from another brand. Various frequencies of colors and added blends also play major roles in FDA approval, so be sure to check the fine print.
How to 3D print food safe utensils
Now that we fully understand the dangers of using 3D printed utensils for food, we’d be remiss in leaving without giving some tips on how to 3D print food parts.
For starters, providing a separate 3D printer for prints intended for food is the most foolproof way to ensure compliance with the Food and Drug Administration. This is an inconvenient requirement because toxic substances can persist over several print cycles.
Here are some tips and tricks to improve the food safety of your 3D prints.
Replace brass parts with stainless steel
Knowing how copper nozzles and extruder gears can deliver lead in 3D prints, and replacing them with stainless steel alternatives is the easiest way to make them safe for food. Just be sure to use parts that are made of food-grade stainless steel because the types of steel used in tools are not the same. Furthermore, stay away from stainless steel nozzles with extra layers of non-stick coating.
Steam smoothing to repair porosity
Layer lines are an important factor that contributes to the porosity of 3D FDM prints and creates conditions conducive to bacterial growth. Fortunately, some threads can be chemically smoothed like ABS, ASA, PETG, and HIPS.
This involves partially dissolving the layer lines through a process of steam softening, in which solvents such as acetone and ethyl acetate are allowed to interact with the surface of the 3D-printed parts. The result results in parts with smooth, sealed surfaces that are easy to clean and lack the surface area required to host bacterial colonies.
For filaments that cannot be chemically smoothed, you may want to reduce the layer height to make the 3D printing as smooth as possible. It should make sanding the surfaces smoother. Just make sure that the sanding equipment does not introduce toxic substances.
Stick to food-safe bristles
While PLA is generally food safe (as long as the manufacturer has not used toxic additives or color dyes), 3D-printed parts are not practical for long-term food handling. The material has one of the lowest heat deflection temperatures (HDT). This means that it will not survive hot drinks or hot dishwashing cycles.
The chemically inert nature of PETG filaments makes it ideal for handling food, but like PLA, it also lacks the HDT required to survive hot and dishwasher foods. However, PETG can be chemically softened. However, ABS filaments produce 3D printed parts that are heat resistant and can also be steam smoothed.
Exotic filaments such as PEI (brand Ultem) are approved by the U.S. Food and Drug Administration, but cannot be printed on non-commercial 3D printers. Meanwhile, nylon and polypropylene yarns are also FDA food safety compliant.
It is still a good idea to check the wick packaging for FDA approval.
Use food safe dipping paints
It’s not easy to adapt your printer to an entirely new material. In most cases, entry-level FDM printers can’t even print materials like ABS out of the box. This makes submersible paint and sealants a viable alternative.
These come in various food grade options, such as polyurethane resins, epoxy, and PTFE coatings. The options are nearly endless, so be sure to do your due diligence regarding FDA approvals and compatibility with different leads.
It is also useful to check the temperature and corrosion resistance of these solutions in advance. You don’t want to use low temperature paint for your coffee mug.
3D printing is food safe? There is so much to consider
The concept of food-safe 3D printing is uncharted territory at the moment. Although the Food and Drug Administration conducts due diligence and issues approvals for popular filaments, it still cannot control for unknown variables of printing temperature and unexpected use cases.
What is certified as food safe may not be the same after prolonged use. Furthermore, it is best to reduce food temperature and contact time and generally avoid pairing 3D-printed utensils with interactive foods.
It is smart to err on the side of caution.
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