Food-Safe 3D Printing: Are 3D Printed Products Food-Safe?
Since the rise in popularity of moulded plastics, kitchens worldwide are packed with these utensils, or at least to some degree, from Tupperware containers to cutlery to everyone’s favourite high-heat marvels: silicone and Teflon instruments. Plastics are lightweight and do …
Since the rise in popularity of moulded plastics, kitchens worldwide are packed with these utensils, or at least to some degree, from Tupperware containers to cutlery to everyone’s favourite high-heat marvels: silicone and Teflon instruments. Plastics are lightweight and do not shatter like glass; they are affordable and easy to produce in mass, disposable and with all the design versatility that moulding technologies grant manufacturers. Rubbers offer excellent sealing properties, and they’re soft to the touch. Furthermore, with 3D printing as a game-changer, versatility in design opens a whole new range of innovative possibilities.
However, things are not as easy as they sound. And, what issues do we face now? Over the latest years, increasing environmental and health concerns have set their eye on plastic kitchenware. We recently tackled sustainability concerns in a two-part article series focusing on how sustainable 3D printing is and how we can make it more sustainable. Now, the new question is: Can 3D printing be food-safe? Is it possible to reconcile the benefits of 3D printing with the need for healthier food consumption?
What are the Potential Food-Safety Hazards of 3D Printed Products?
So, where do we begin? Let’s start by naming the undeniable three potential hazards in plastic food products: Material hazards, bacterial growth and fabrication processes. We’ll do an overview for each one and subsequent design and processing requirements to achieve the highest level of food safety possible.
Recent studies point out that many everyday food packaging plastics are not as chemically stable as we think. Some studies point out at UFPs (Ultrafine Particles). Monomers and microplastics migrate into foods after extended contact, especially after heating or after dissolving with particular food substances, namely oils.
The other big concern is plasticisers, additives commonly used to improve material quality in terms of flexibility. Two significant examples are the controversial BPA (Bisphenol A) and phthalates. While the first one is common in polycarbonate bottles and epoxy coatings in cans, the other grants PVC wraps their flexibility. Both substances are endocrine disruptors that could potentially affect reproductive and brain development in fetuses, babies, and children.
There’re even suspected levels of cancerogenic in plastic bottles. Nevertheless, important regulatory entities like the FDA (Foods and Drugs Administration) and REACH (Registration, Evaluation, Authorisation and Restriction of Chemicals) point out that while migration of particles might be true, it happens at low enough safety levels for it to have harmful effects.
All in all, we still lack consensus on the matter, and the best thing we can do is take preventive measures while choosing our printing materials. Check out the quality labels and inform yourself of future studies and public perceptions to generate the utmost confidence in your products. The requirements for qualified food-safe materials mainly are:
- Heat resistance, materials must deal at least with dishwasher temperatures and repeated washing cycles
- Chemical reactivity to common foods, cleaning agents and solvents. No odours nor colours, or tastes should transfer to foods.
- Resistant to mechanical scratching, chipping or deformation.
- Accesible for inspection
3D Printing Material Food-Overview
Evaluating whether or not a material is food-safe is not a simple task, it depends on the specific manufacturer formula and respective certifications. And, even if a material is approved for blue and yellow, for example, it might not be the case for red and green since different additives are added for each case. Let’s see, briefly, what we know for well-known materials.
PLA: The most widespread FDM printing material. Countless companies make unique PLA variations (PLA+, PLA PRO, WoodPLA, Copper PLA, etc.), and food-safe formulae are not the exception. Many brands sell FDA approved PLA. Just consider that PLA is weak against high temperatures, so using PLA to drink hot tea might not be the best idea.
PETG: This material is famous for its food-safe properties, similar to PET bottles. However, checking the labels for extra assurance wouldn’t be a bad idea.
ABS: This is the material you need to make strong, durable and heat resistant cups for hot tea; however, ABS safety is highly questionable. ABS printing is known for emitting toxic fumes; additionally, they are suspected of releasing harmful styrenes on contact. Despite all, there’re some food-safe certified options on the market.
PP: Polypropylene is the typical material you would find in food packaging, from disposable cups to Tupperwares. So, it is not strange to find that PP filaments are also ideal for food-safe applications.
PC: This material is robust, clear and durable; however, the red flag is that it might contain BPA, so better not use it.
Nylon: Polyamides are ideal for high-temp applications. Only specific grades like nylon 6 without additives are mostly food-grade.
SLA resins: Most resins for SLA 3D printing are not food-safe and are even toxic. If biocompatible resins come to mind, unfortunately, no, they aren’t. They are specifically made for medical and dental applications, that doesn’t mean they’re also compatible with food applications.
Ceramics: This material has been with us since the dawn of civilisation, carrying our food safely. And, thankfully for us, ceramics are also 3D printable. Just make sure to glaze them after printing! For more information on ceramics 3D printing, click here!
When working with plastics, you must consider that microorganisms tend to have an affinity to some plastic materials under certain conditions. Within few weeks or even days, entire bacterial and even mould cultures will attach deeply into the object’s surface, causing potential infections after food or human contact. In this case, more than focusing on which material to choose, you must consider surface qualities in terms of:
- Smoothness: Gaps in layered surfaces typical of 3D printed parts are ideal for bacteria to grow. Try to reduce them to the bare minimum.
- Geometry: The object must be designed to have easy-to-wash surfaces. Try to avoid sharp internal angles.
- Coatings are a great option. Be sure they are food safe and resistant to heat, scratching, impacts or anything that could expose the original surface in one way or the other. Also, coatings must be compatible with the material of choice; they must adhere well while avoiding reactions with the print’s surface.
Now, let’s say that you chose the suitable material, it has all the big food-grade quality labels and it is also resistant against bacterial growth. But what about the fabrication process itself? I mean, all that happens during printing and post-processing? How do you make sure no harmful substances migrate from your equipment and tools? Let’s see what’s the case for FDM, SLA and SLS.
FDM: Although FDM offers a wide range of food-safe options, the main issue is the resulting lack of surface smoothness compared to other methods. The ideal print would need to have the thinnest layer height possible, and even that wouldn’t be enough. Subsequent post-processing would be necessary; you would need to sand the part with the help of filler pastes. Alternatively, you can use solvents like acetone or limonene-d if it applies to your material. Nevertheless, it would be best to ensure that the materials you use for post-processing are food safe; furthermore, applying coatings might be necessary.
Regarding the machine, you must make it as sterile as possible by cleaning it before using it. Verify the bed adhering method is safe, but most importantly, pay attention to which nozzle material you use. Standard brass nozzles might be affordable and more than enough to print your material of choice; however, they might contain lead. So, for food-safe applications, it is better if you invest in a stainless steel nozzle.
SLA: With SLA happens the opposite as with FDM. While SLA materials are mostly not safe for food, surface smoothness and the possibility to make more intricate designs is a great advantage. Of course, standard SLA post-processing (washing and curing) is a must after printing. Just like with FDM, sanding and coating are highly recommendable.
SLS: While many SLS nylon options are food safe, the main issue is that SLS is definitely not a clean process. This technology deeps your part into fine powders, which aren’t that easy to clean in their entirety since the resulting surfaces are exceptionally porous. Using compressed air might come in handy, but if it comes within your possibilities to autoclave it, then that would be the best.
When considering bacterial and mould growth, it happens with pores as with layer lines but even worse. Luckily, SLS parts are highly versatile for post-processing. You can smooth them, and you can coat them, even dye them. For more information on SLS post-processing, we have a whole dedicated article here.
Sometimes 3D printing is just a means to an end, and this fact becomes more relevant when developing food-grade products. The following are some great things you can do from a printed part.
Electroplating: This process makes it feasible to coat a part with metals by dipping it in an electrolytic fluid. Since your part must act as the cathode in a close electrical circuit, electroplating submersion is not as easy with plastics as with metals, but high-quality results are entirely possible. Again, make sure the metal you use is food safe and resistant to corrosion.
Silicone mould casting: 3D printed parts are ideal patterns to create silicone moulds. This rubber has a big success history in the kitchen goods industry due to its soft texture, durability, high thermal stability, and chemical stability with foods and cleaning agents. Just as you would mould muffins with silicone, you can cast utensils with materials such as urethane, plaster and epoxy (BPA-free, of course). To go deeper into the silicone moulding process, check this article!
Vacuum forming: Similarly to silicone casting, you can use a 3D printed part as a pattern for thermoforming. This process is ideal for making custom packaging trays and covers; nevertheless, you can get even more creative with it. The best part, perhaps, is that there are countless food-safe plastic sheet options on the market.
Lost resin casting: This process allows you to cast metal and ceramic objects from a pattern made with castable resin. This process might not be the cleanest, so take proper safety measures if you want to use it for food-safe applications. For more information on this process, click here.
Do you have a food-related 3D printing project in mind? SolidPrint is here to help you make the best decisions. For more information, please call SolidPrint at 01926 333 777 or email firstname.lastname@example.org.
Check our latest articles here!