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Creating 3D printed food contact items was a myth that is now turning into reality. More and more materials are being developed and approved as food safe. This is a guide towards food safe products for various 3D printing technologies.

Food safe, what does it mean?

3D Printing enthusiasts and professionals are concerned with possible inhalation of the fumes released during the 3D printing process [7,10]. Food grading concerns another way to ingest parts: migration. Particles as small as a few up to several hundreds of nanometers are transferred with each substance the material encounters; from the 3D printer to the 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 [2] and for the EU in guidelines 10/2011 and EN 71-3. Beware that a material being ‘compliant with’ means something different than it being explicitly approved by the institutions, so always check the technical datasheets for a certificate.

Look for these labels indicating FDA and EU approval.

To be considered food safe according to the FDA Food Code [3], a material has to meet the following requirements:

No migration of deleterious substances

Does not impart colors, odors or tastes

Safe under normal use conditions

Durable, corrosion-resistant, and nonabsorbent

Sufficient in weight to withstand repeated washing

Finished to have a smooth, easily cleanable surface without breaks and sharp internal angles

Resistant to pitting, chipping, crazing, scratching, scoring, distortion, and decomposition

Accessible to inspection

Any FDA or EU approved material includes not only the raw polymer but also the additives or masterbatch. It contains 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. That is a mouthful though you don’t want most of these actually landing in your mouth.

We will now analyze food safety aspects for various 3D printing processes.

FDM

Fused Deposition Modeling (FDM) is a 3D printing process that builds objects layer by layer while a plastic filament is being extruded from a heated nozzle. Since the extrudate is circular in cross-section, this 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.

Layers showing on FDM (left) and SLA (right) 3D prints.

Filaments available for food safe 3D printing are PLA, PP, co-polyester, PET, PET-G, HIPS, nylon-6, as well as a few 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. The public perception with polystyrene is that it may leach styrenes, also more and more people tend to avoid PET. The best filament choice is in many cases polypropylene [11]. For applications involving hot liquids, co-polyester, High Temperature PLA or PEI are most suited though it has been debated that co-polyesters will also cause health concerns.

Food Safe FDM Materials

Filament Brand FDA EU Smoothable Dishwasher Hot liquids ABS Adwire PRO Approved NA Yes, acetone Yes Yes Innofil3D Approved except red, orange and pink Approved

except red, orange and pink Yes, acetone Yes Yes ASA Innofil3D NA Compliant Yes No Bendlay Orbi-Tech NA Compliant Yes, brake cleaner No No Biocompound Extrudr GreenTEC NA Compliant – Co-Polyester Colorfabb XT Approved Compliant No Yes Yes HIPS Easyfil Compliant Compliant Yes, d-limonene Yes No Fillamentum NA Compliant Yes, d-limonene Yes No InnoFil3D Approved Approved Yes, d-limonene Yes No Nylon Taulman Nylon 680 Compliant NA No No PEI ULTEM® 1000 Compliant NA Yes Yes PET InnoPet EPR Approved except red and orange Approved except red and orange Yes, ethyl acetate No No Refil Approved NA Yes, ethyl acetate No No Taulman T-Glase Approved NA Yes, ethyl acetate No No Verbatim Compliant NA Yes, ethyl acetate No No PET-G Extrudr MF NA Approved Yes, ethyl acetate No No HDGlass Approved Approved Yes, ethyl acetate No No PLA Filaments.ca TrueFS Approved NA No No No Fillamentum NA Compliant No No No Innofil3D Approved except red, orange, pink, apricot skin, grey and magenta Approved except red, orange, pink, apricot skin, grey and magenta No No No Copper3D PLActive Antibacterial Approved Compliant No No No Makergeeks Approved NA No No No Purement Antibacterial Approved Approved No No No PLA-HT Fiberlogy Approved Approved No Yes Yes Makergeeks Raptor Approved NA No Yes Yes PP Centaur Compliant Compliant No Yes

+microwave-safe Yes InnoFil3D Approved Approved No Yes Yes Nunus Compliant Compliant No Yes Yes Verbatim Compliant NA No Yes Yes SBS Filamentarno NA Approved only in Russia Yes, d-limonene No No

You can be too Cautious

For developers, the suggested work ethic is often to avoid as much risk as possible. Looking closer we find that actual migration levels are in most cases far below tolerated or even measurable [7] levels. We have irrational fears for any additive even though some are completely organic such as some UV blocking agents. We prefer to avoid anything non-organic even though some components do no harm to the human body. ABS for example has a petrochemical basis but several compounds that were recently processed into 3D printable materials have been FDA food contact approved. Do not turn away from a material before having done a detailed analysis on its benefits regarding different aspects of your 3D printing venture.

Foodproofing 3D Printers

Always check the compatibility of your 3D printer’s components with the filament. Some PEI that is FDA compliant offers great mechanical benefits but needing to be processed at over 300°C it requires a specific printer solution. And a PTFE liner will already start to disintegrate when printing ABS over 240°C.

Foodgrade filaments do not contain any composite particles so will hardly wear down the nozzle into the print. Avoid brass nozzles that contain lead and use a dedicated stainless steel nozzle instead for all food contact items.

Avoiding Microorganisms

A 3D print can turn into a petri dish squirming with bacteria within weeks. High Temperature PLA will survive the dishwasher, but 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 in eliminating germs. The exceptions are PEI which is so heat resistant that it can be steam autoclaved, and PP which has no definite melting point so it will withstand microwaving for a brief period.

Yet to be truly food safe and approved by the authorities, a 3D print needs a smooth surface. Chemical smoothing such as with d-Limonene for HIPS removes many of the irregularities of the print resulting in a glossy appearance and without the health risks of using acetone (for ABS) or ethul acetate (for PET). It does however not satisfy the complete set of requirements for food safety, therefore we recommend dip coating the part in a food-grade epoxy resin such as polyurethane, Masterbond’s EP42HT-2FG, Alumilite Amazing Clear Cast and ArtResin. Not all of these are dishwasher safe, and they may degrade over time exposing the original print.

Vapor smoothing reduces but does not fully remove all crevices on an FDM 3D print.

Image courtesy Rigidink.

SLS

Selective Laser Sintering is a 3D printing process that utilizes two lasers that at their intersection melt and fuse powder particles. The most common material is a type of nylon that results in flexible and strong parts. Some of these powders are graded food safe, but because they do not fuse completely, the products created with SLS are inherently porous and do not deal well with moisture and mold growth. Even though the nylon 12 powder can be steam cleaned in an autoclave, it is best to seal SLS parts with a food contact approved resin similar to what we advise for FDM parts. After an SLS part has been dyed, the dye may leach into the resin which renders the item not food safe.

The same advice holds for parts made with DMLS (Direct Metal Laser Sintering); even though the 316 Stainless Steel powder is food-safe, the surface still contains crevices and porosities so it will need a post-processing step.

The surface of SLS and DMLS parts is porous and contains possible contaminants.

For a specific solution, it is possible to apply an FDA approved PTFE (known as Teflon®) coat to SLS nylon parts. Dip molding your part in food-grade silicone or urethane will in many cases also work. Common food contact compliant silicones with relatively low viscosity are Smooth Sil 960 and Sorta Clear 18. Take note that not all FDA compliant materials are in fact suitable for producing high-risk items such as baby bottle teats.

SLA

Stereolithography (SLA) 3D printers create models layer by layer by means of photopolymerization. A UV light source progressively hardens a liquid resin so a solid object emerges. Stereolithography produces the most detailed and accurate parts of all 3D printing processes. Geometrically it is therefore best suited for food contact parts, however chemically there are substances that may migrate from these parts which makes none of the resins food safe. If for any reason toxicity might be an issue in your projects, one study suggests post UV-curing the parts to reduce their toxicity levels [6]. Even though the resins themselves are not food safe for prolonged use, they are suitable to create molds for products that do come into food contact [5].

Another option is to electroplate your parts. This is possible for SLS as well as SLA parts, the requirement being that they are sanded to absolute smoothness. Since this process involves different chemicals, it is not officially approved for food contact so any use will be the developer’s own liability. In electroplating, a layer of copper is first electroformed over the outer surface. Since copper poses corrosion risks it is forbidden by the FDA [3 – §4-101.14] for contact with foods with a pH level under 6. Your part needs an additional layer which is applied electrolytically. In this process metallic salts are used which become depleted and do not end up in the final product.

The process allows plastics such as ABS, nylon, PET and polystyrene to attain a coat of gold, silver, nickel, aluminum or stainless steel. The latter is used for metallized polystyrene silverware because it is the most durable and dishwasher-proof coating. Some of these metals may leach dangerous other metals such as lead, zinc, cadmium or chromium. The ingestion of aluminum is linked to neurotoxicity and Alzheimer’s for example, even though in some food contact products it is tolerated by the FDA as being ‘decorative’. We do not recommend using electroplated parts for food contact unless explicitly stated by the manufacturer.

Providing a mineral oil finish is a popular method to increase transparency, but note that this oil is petroleum-based and not food approved.

The best option is to coat SLA parts with one of the food-grade, epoxy resins we mentioned at the end of the FDM section. These all have a low viscosity eliminating the need for toxic thinning agents. The factors which affect the ultimate smoothness of a part include resin type, resin viscosity (dependent on temperature), part stripping residue, build orientation, mesh triangulation resolution of the 3D model and the curing profile of the SLA resin in addition to the defined layer thickness [9].

Ceramics

For true food safe 3D printing, the only material that meets all requirements is fired and glazed ceramic. SLS and Binder Jetting are high-end technologies able to produce ceramic 3D prints. Formlabs is the first company to offer a desktop stereolithography solution with Ceramic Resin. The Form 2 3D Printer uses a ceramic powder embedded in a polymer resin matrix. After 3D printing, parts are kiln-fired which burns out the resin. It also makes them stronger and more heat-resistant. With a subsequent food safe glazing they become resistant to almost all chemicals and as hygienic as 316L stainless steel.

When designing a 3D printed object for end-use, take into account that most people are not informed about the dangers and have a high risk perception with the term. Some people avoid plastics altogether, let alone 3D prints. When consumers and developers can be convinced of food safe 3D printing, it opens up numerous germ-free applications besides mugs and bowls: musical instruments, vases and hydroponic planters, scent diffusers, handheld electronics, custom control knobs, knife handles, bathroom accessories, massage objects, cake decoration, storage containers, and piggybanks to name a few.

3D prints in Ceramic Resin by Nervous System.

References

Boyer, M. (2010) Germapalooza: How to Keep Kitchen Sponges Clean. HowStuffWorks. https://recipes.howstuffworks.com/tools-and-techniques/cleaning-your-cooking-area/how-to-keep-kitchen-sponges-clean.htm FDA 21 CFR §175 and §177. FDA Food Code. Recommendations of the United States Public Health Service Food and Drug Administration (2017). U.S. Dept. of Health and Human Services. Formlabs Ceramic Resin https://formlabs.com/materials/ceramics/ Formlabs (2015) Chocolate Molds with 3D Printing & Vacuum Forming https://formlabs.com/blog/custom-chocolate-molds-3d-printing-vacuum-forming/ Grover, W. et al. (2015). Assessing and Reducing the Toxicity of 3D-Printed Parts. Environ. Sci. Technol. Lett. 2016, 3, 1-6. Jacobsen, E. et al. (2017) Risk Assessment of 3D Printers and 3D Printed Products. The Danish Environmental Protection Agency. ISBN 978-98-93614-00-0 Lelieveld, H.L.M. (2016) Handbook of Hygiene Control in the Food Industry. Woodhead Publishing, ISBN: Reeves, P.E., and Cobb, R.C. (1995) The Finishing of Stereolithography Models Using Resin Based Coatings. UK: University of Nottingham. Stephens, B. (2013). Ultrafine Particle Emissions from Desktop 3D Printers. Atmospheric Environment 79 (2013) 334-339. Elsevier Ltd. Trombetta, D. (2016). Choosing Plastic for Food Contact Applications. FDA. https://weeklypellet.com/2016/06/10/the-tricky-business-of-choosing-plastic-for-food-contact-applications/

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