3D printing food safety
Context
3D-printed objects should generally not be used in contact with food for various reasons depending on the specifics of your printer, material and use case. For personal projects anybody has to judge these factors for themselves but food products for other people should not be exposed to these risks.
Problems
Nozzle
Especially but not exclusively older and/or lower priced printers use brass nozzles since they conduct heat really well. Because they are softer than stainless steel nozzles, higher amounts of the material gets rubbed off. Since some of the brass nozzles contain trace amounts of lead the contamination of the filament also contains this really unhealthy metal. Additionally material that was used previously may also remain in the nozzle and mix with the new filament rendering food safe materials useless if it has any unhealthy effects.
Quality & Additives
While a lot of polymers (the main component) in filaments are fundamentally food safe, additives in the filament such as colours or fibres may not. Also, if a polymer is produced poorly there may remain leftovers of the monomers that diffuse into e.g. fluids in contact (similar to BPA)
Hygiene
Because of the layer lines in FDM printing that are hard or impossible to clean, prolonged/repeated use is not advised.
Solutions
Nozzle
Using a stainless steel nozzle for only a single kind of filament decreases contaminations as much as possible.
Additives
Some shops or manufacturer declare their filaments to be food safe making them a bit more expensive. These claims may not really be trustworthy and should at least be backed by official badges.
Hygiene
Filling the gaps with food safe epoxy, using it as a one time only tool or clean it hot enough to kill anything sticking to it can reduce the contamination. The latter would require a filament with higher glass transition temperature such as ABS. (This ABS could be fitting)
Possible Bypass
The easiest way would be to wrap the printed object in a food safe film avoiding all of the problems above.
Unfortunately some applications don't really work with this solution since they require fine details on the print or can not be covered without closing off recesses. (e.g. Project:Cookie Cutters)
