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Read on for an introduction to food safety, food safety considerations for 3D printing, and a variety of methods to produce food safe products with common 3D printing processes, including stereolithography (SLA) , fused deposition modeling (FDM) , and selective laser sintering (SLS) .
Food safe 3D printing is possible and the variety of materials approved as food safe is increasing, but there is a high degree of ambiguity around the workflows and finding the appropriate applicable regulations can be a challenge.
These benefits can be compelling for a range of food-related applications. However, if 3D printed parts are intended for food contact items, you&#;ll have to consider safety practices and regulations to avoid contact with toxic substances and prevent the buildup of harmful bacteria.
3D printing offers unparalleled design freedom to produce custom parts and complex or organic shapes that would be costly or impossible to manufacture with traditional manufacturing methods.
Having trouble finding the best 3D printing technology for your needs? In this video guide, we compare professional 3D printers across popular buying considerations.
To begin, it&#;s important to clarify a few key terms:
Food grading and food safety concern a specific way to ingest parts, called migration. Particles as small as a few nanometers and up to several hundred nanometers may get transferred each time various materials encounter with each other, for example from components of the industrial 3D printer to the 3D printed object, and from the object to the food.
Because migration levels are very low on occasional contact, food grading typically concerns items that are in prolonged contact with food such as containers, straws, utensils, plates, and food molds. Different testing institutions will adhere to different government-imposed risk tolerances and approved substances, which for the US is described by the FDA CFR 21 and for the EU in guidelines 10/.
Look for these labels indicating FDA and EU approval. Beware that a material being &#;compliant with&#; doesn&#;t mean that it is explicitly approved by the institutions, so always check the technical datasheets for a certificate.
To be considered food safe according to the FDA Food Code, a material has to meet the following requirements:
Any FDA or EU approved material includes not only the raw polymer but also the additives or masterbatch. These might contain components such as plasticizers, impact and heat distortion modifiers, UV-stabilizers, flame retardants, anti-fouling, anti-static, anti-slip, foaming and clarifying agents, anti-oxidants, aromatic nucleators, carbon alloys, phosphorescents, fillers, thickeners, chain extenders, metal deactivators, dyes, and a carrier resin.
A 3D printed part can turn into a petri dish squirming with bacteria within weeks. Even though some materials will survive the dishwasher, so will dangerous bacteria such as E. coli and salmonella that live in the little nooks and crannies. Some toxic molds find favorable growth conditions on several types of plastic and are hard to remove. Neither cleaning with bleach nor microwaving your polymers is an option for eliminating germs.
While bacteria buildup might not be an issue for disposable items, if you&#;re planning to create a part for long-term use, using a food safe coating is highly recommended.
The best option to reduce the risk of particle migration and bacteria buildup is by dip coating the 3D printed parts with a food grade epoxy or polyurethane resin, such as Masterbond&#;s EP42HT-2FG or ArtResin or an FDA approved PTFE (known as Teflon®) to seal their surface.
However, note that coating also doesn&#;t guarantee food safety for prolonged use as not all of these coatings are dishwasher safe, and they may degrade over time, exposing the original, potentially non-safe surface.
Most 3D printing materials have a low heat deflection temperature (HDT), which means that the 3D printed parts might become brittle and crack, or deform and warp at elevated temperatures. If you&#;re planning to clean a 3D printed part in a dishwasher, make sure to double check that the material is dishwasher safe and if there are any specific recommendations for washing temperature.
As particles might migrate from components of a 3D printer to 3D printed parts, it is crucial that any components that might come in contact with the 3D printing material or the part are food grade and do not contain or leach harmful chemicals.
This includes taking precautions when using multiple materials, as some materials previously used in the 3D printer might have contained toxic particles and made contact with some components.
Many 3D printing materials are not food safe and might contain toxic chemicals. Only use materials to 3D print parts intended for food contact that are certified for food safety.
As may be expected, the risk of migration is higher if the food is exposed to the 3D printed part for an extended time period. In general, try to limit food contact time and take further precautions for parts that will be in contact with food for longer periods of time.
Think about the reason why you&#;d like to use 3D printing for a food contact item. If it&#;s to create custom shapes and forms, in most cases, there are indirect ways to use 3D printing to create these custom parts, for example with molding. See an example in the next section.
SLA 3D printing uses a laser to cure liquid resin into hardened plastic in a process called photopolymerization, resulting in parts that have the highest resolution and accuracy, the clearest details, and the smoothest surface finish of all plastic 3D printing technologies.
Is resin food safe? The answer is no. Substances may migrate from SLA parts which makes none of the resins and printed parts food safe by default. While some resins for dental and medical applications are certified biocompatible, that doesn&#;t mean that they&#;re food safe. These materials are certified for specific applications and should not be used for food contact products.
SLA parts have a smooth surface finish that makes it easier to use coatings to seal their surface and prevent the buildup of bacteria. The factors which affect the ultimate smoothness of a part include resin type, layer thickness, build orientation, mesh triangulation resolution of the 3D model, and the curing profile of the SLA resin. Printed parts require washing and post-curing according to the manufacturer's instructions before the coating is applied. However, note that coatings don&#;t guarantee food safety, as the coating may interact with the resin or degrade over time, exposing the original, potentially non-safe surface.
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Creating custom molds is a common way to leverage the benefits of SLA 3D printing to produce highly detailed custom parts without having the 3D printing parts come into direct contact with food. While SLA 3D prints aren&#;t suitable for directly molding foods, (SLA) resin 3D printers are perfect tools to create mold negatives, which can be vacuum formed using food safe plastic.
The tools and techniques for creating 3D printed food molds are easy to master, and the results are often stunning.
3D printed molds for thermoforming and silicone enabled the creation of unique shapes and designs.
Learn more about creating molds for vacuum forming in our in-depth tutorial.
Electroplating is the process of coating parts with metal using an electric current. The process is most commonly used for decorative purposes or to prevent corrosion by creating a durable surface.
SLA parts are ideal for electroplating due to their smooth surface finish. However, as plastics are nonconductive surfaces, SLA 3D prints have to be rendered conductive by coating with graphite, conductive lacquer, electroless plate, or a vaporized coating.
Food safe metal coatings are available, but as the process involves various chemicals, making sure that the workflow is approved for food contact is the developer&#;s own liability.
SLA 3D printing offers the unique possibility to produce ceramic parts. After 3D printing, parts can be fired in a kiln to burn out the resin and form a true ceramic part that is strong and heat-resistant. With subsequent food safe glazing, the parts will become more hygienic and resistant to most chemicals.
A variety of food safe glazes are available on the market, but make sure to follow the manufacturer&#;s instructions in accordance with food safety guidelines.
3D printing in ceramics is ideal for fabricating complex geometries that wouldn&#;t be possible by hand.
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FDM is a 3D printing process that builds parts by melting and extruding thermoplastic filament, which a print nozzle deposits layer by layer in the build area.
The extruded material is circular in cross-section, which leaves very narrow crevices in between layers with a depth directly proportional to layer height. It is recommended in any case to print at the lowest feasible layer height for food safe parts.
Consequently, the main challenge with FDM parts is avoiding the buildup of bacteria. To be truly food safe in the long term, an FDM 3D print needs to have a smooth surface. Chemical smoothing with solvents like acetone, d-Limonene, or ethyl acetate removes many of the irregularities of the print resulting in a smooth, glossy appearance. However, applying a subsequent food safe coating is still highly recommended.
Layers showing on FDM (left) and SLA (right) 3D prints.
Food grade filaments do not contain any composite particles so will not wear down the nozzle into the print. Nevertheless, avoid brass nozzles that contain lead and use a dedicated stainless steel nozzle instead for all food contact items.
Always check the compatibility of your 3D printer&#;s components with the filament. For example, PEI is a material that is FDA compliant and offers great mechanical benefits but needs to be processed at over 300 °C, which requires a specific printer solution.
The most common questions around FDM food safety concern two popular materials. Is PLA food safe? Is ABS food safe? The answer is, it depends.
Food safe 3D printing filaments include PLA, PP, co-polyester, PET, PET-G, HIPS, and nylon-6, as well as some brands of ABS, ASA, and PEI. Having to run parts through the dishwasher rules out PET, nylon, and PLA because these plastics soften and distort around 60&#;70 °C. For applications involving hot liquids, co-polyester, High Temperature PLA or PEI are most suited.
While not reflected in the regulations, some studies suspect that polystyrene may leach styrenes, co-polyesters might cause health concerns and that food grade FDM filaments might lose their safe status due to oxidation and thermal degradation from the printing process.
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