3D printing has matured as a manufacturing technology over the past decade, inching closer to becoming a mainstream manufacturing technology. This is in large part because 3D printing technology has gotten more sophisticated, leading to more consistent, durable, and complex prints that match its counterparts made with injection molding and CNC machining.
With this continued acceptance, more industries are exploring the use of 3D printing as a part of their manufacturing strategy. One of these is the food industry, where food packaging, utensils, or spare parts for food production lines can all become important 3D printed parts. The food industry has strict regulations regarding safety which must be considered when planning on using a new manufacturing technology. This article will discuss how to design and implement food safe 3D printing and clarify the responsibilities of the client and manufacturer when it comes to ensuring the printed parts meet strict requirements.
In order to make a part food-safe, it is important to review the relevant regulations in the region where the part is to be distributed or used. This section will focus on the challenges of implementing food-safe 3D printing by basing the analysis on the 3-A Sanitary Standards that were developed to help companies comply with FDA and USDA regulations. In general, there are three factors that determine if a part is safe for use with food: its design, the materials used, and the manufacturing process.
In terms of food safety, parts are divided into two categories according to the 3-A Sanitary Standards:
When evaluating a component for food-safe 3D-printing, it is important to focus on the product contact surfaces. Listed below are some key points that need to be considered in the design phase.
Another critical factor in determining the food safety of parts is the material. Listed below are some key material-specific factors that product designers should consider.
It is important to understand that sterilizable does not necessarily mean food-safe. Sterilizable simply means that the material can be effectively purged of all bacteria. However, the factors mentioned above can determine whether the part is ultimately food-safe. An example of this in the list below is ABS; while it is sterilizable it is not food-safe. Listed below is a summary of various sterilizable 3D printed materials.
| Process | Material | Method of Sterilization | Considerations |
|---|---|---|---|
| SLS / HP MJF | Nylon 11 or 12 | Chemical, EtO, Gamma, Plasma, Chemica, Steam Autoclave | Moisture absorption, matte surface |
| FDM | ABS-M30i | EtO, Gamma | Gaps and crevices in surface |
| FDM | PC-ISO | EtO, Gamma | Gaps and crevices in surface |
| FDM | ULTEM | EtO, Gamma, Steam Autoclave | Gaps and crevices in surface |
| Carbon DLS | CE, EPX, RPU | Electron Beam Irradiation, EtO, Gamma, Steam Autoclave | Limited cycles or minor changes in mechanical properties |
| Carbon DLS | FPU, EPU, SIL | Electron Beam Irradiation, Gamma | Limited cycles or minor changes in mechanical properties |
| DMLS | Stainless Steel 17-4PH or 316L | Chemical, EtO, Gamma, Plasma, Chemica, Steam Autoclave | Matte surface |
List of Sterilizable Materials
The manufacturing technique and process also need to be carefully chosen when trying to achieve food safe 3D printing. Below are two considerations for choosing the right 3D printing process:
3D Printing Technology - It is important to choose the correct 3D printing technology for the project at hand. Generally speaking, fused deposition modeling (FDM) machines will create parts with rougher surface finishes whereas stereolithography (SLA) and selective laser sintering (SLS) can create smoother surfaces. However, these decisions need to be made in tandem with material selection, part design, and post-processing surface finishes, which we discuss in the next section.
Materials of the 3D Printer- If the material being printed is rated as food-safe and the surface profile of the correct smoothness achieved, a part can still be denied its food-safe classification if the machine on which it is printed is not food-safe. An example of this would be a brass nozzle on an FDM machine that may contain traces of lead or lubricants used for the mechanical components that are not food-safe.
As-machined 3D-printed parts may have surface finishes with a roughness that does not meet the minimum 32 Ra surface roughness standard set by the 3-A Sanitary Standards. To help surface finishes achieve a surface smoothness that does not contain small pockets for bacteria growth and that can be easily cleaned, a part can undergo post-processes like mechanical finishing and surface coatings.
FDM Surface Finish
To reduce the surface roughness of parts intended for food use, it is possible to use mechanical methods to smooth out certain materials. While metal parts respond well to polishing, some plastics can be ground, tumbled, or machined to improve their surfaces.
It should be noted that with some materials and processes, it is simply not possible to get a food-safe surface finish even with the above-mentioned processes. Food-safe product design starts with the design, material, and manufacturing process; once these are properly chosen, mechanical finishing can help food-safe products reach safety standards.
When mechanical finishing is not achievable or cost-effective, it is possible to coat non-qualified parts with a food-safe coating, thus allowing for food-safe 3D printing. These coatings can include anything from food-grade epoxy to polyurethane. They effectively smooth out the surface by filling in all the gaps and voids as well as creating an impervious food-safe seal between the part and the food. It's important that these coatings are free of typical coating defects (problems like blistering, delamination, and pitting, to name a few). These coatings should also be compatible with any cleaning products that are to be used to periodically clean the part in service.
Food safe 3D printing relies on many factors. Together, the materials, design, manufacturing method, and application will help a certifying body determine whether a product adheres to all safety standards. While Xometry cannot guarantee a product will be food safe, our team of application engineers can provide expert guidance on which materials, design principles, and manufacturing techniques will put you on the best possible path to achieve the necessary level of food safety. Xometry offers over 7 different additive manufacturing technologies through its on-demand 3D printing service. To learn more about the options for food safe 3D printing manufacturing, contact a Xometry representative today.
