Food-safe 3D printing is not as simple as it might seem. Here we outline some of the challenges. We also recommend you to check out our blog article where we present our research of the process.
PETG, and sometimes PLA, are hailed in the 3D printing community for being chemically neutral and as practically food-safe materials. Your soda plastic bottles, food containers, and salad boxes are made from PET, a close relative of PETG.
The problem, with all 3d-printed objects, in general, is that they are made from layers. The grooves in between those layers are a seedbed for bacteria as they are almost impossible to clean properly, and will hold residue.
Another issue is color-pigment and unknown additives. These might not be as neutral to your body as pure plastic. It is also hard to say exactly how much there is of these substances. Natural/pure PETG-filament without any color, would be your best bet, but it's hard to say exactly what is in it. Some filaments are FDA-approved, but often with an asterisk like "Approved except red, orange, and pink". In our blog article we map out which of our Prusament filaments you can and can not use.
Waterbottle, no. Cookiecutter, maybe. There should not be much problem to 3d-print your own custom cookie-cutters, but as the layer-lines will collect food, bacteria will grow, so this will be something you want to throw away after some use.
The same goes for soap and detergent if you think you can just wash it. The layer lines can absorb these chemicals, which later can be released into something you want to consume.
Again, no. There can be uncured resin and other contaminants on and in the print. There are bio-compatible resins out there, but these are highly specialized and very expensive. They also rely on special considerations when curing and in post-processing.
The nozzle you use also makes a difference. The standard brass nozzle is not considered food-safe, as it wears out. It is a consumable. Where does the worn material go? Into your print. Therefore, a soft brass nozzle just won't do. You would need a stainless-steel or a titanium nozzle if you are even considering printing with food in mind.
There are epoxy resin coating-materials out there that have been deemed suitable. There is also the option of using 3d-prints simply as a mold with suitable materials and manufacturing methods. We have done some research and you can read more about food-safe 3D printing in this blog article.
It is theoretically possible, but special preparations and post-processing is required. If you really want to, it is not as simple as getting some PETG, and printing what you want. Do proper research, so you do not put anyone's health or safety at risk!