3D Printed accessories potentially harmful

Surely you jest?

This does feel a little bit like pearl clutching, I’m sure many people will use many of these things and never have an issue. But I wouldnt let my (hypothetical¹) baby anywhere near a 3D printed rattle, and you cant assess your risk if you don’t understand the risk.

At its core, the problem is that printed items are usually FDM, and FDM items are not able to be safely cleaned or sanitised.

Lets get up to speed on 3D printing, lightning round.

There are a lot of different 3D printing methodologies. Heres the ones you will generally see:

• FDM: Fused Deposition Modelling, this is the vast majority. The printer lays down plastic like a robotic hot glue gun, through drawing each layer it makes an object.
• MSLA: Masked Stereolithography, colloquially referred to as ‘Resin’ printers. They use a vat of uv curing resin, a screen and a uv light to expose a layer at a time, drawing the object out of the resin bath. Some other resin printers use other techniques, like lasers. Technically different acronymn, same result and issues.
• LPBF / SLS: Laser Powder Bed Fusion or Selective Layer Sintering, A laser melts the top layer of a powder bed, an arm sweeps another thin layer of powder over the top, laser fuses again, repeat. Used to be the majority of prints pre the Consumer FDM revolution, now it’s only just, just starting to have companies try to make desktop versions of the industrial machines. If you have ordered a print in metal from an online company, it was likely this method.
• MJ: Material Jetting, very similar to your 2D printer, it prints out uv cure resin, cures the layer, repeats. Used to be the domain purely of wildly expensive objet printers, just now there are companies bringing these out for the desktop. Can do full colour, mixed materials, etc.

Theres more, but these are the ones you are likely to run into. The vast, vast majority of prints you will see are FDM, obvious by their layer line texture. Resin prints secondarily. The other two, more likely over the coming years.

FDM Printers can print in a wide range of plastics. PLA, ABS, ASA, PC, PP, PETG, PA, HIPS, TPU, etc. You will sometimes see people state that PLA is made from plants, biodegradeable, and safe. You can even buy PLA thats labelled as ‘food safe’. This is all largely only true in very specific circumstances. Alongside this, filaments often have additions, such as pigments, glitters, glass and carbon fibre particles; these give different looks and properties. Also, a material might be ‘food safe’ as a filament on a roll, but that doesnt mean that whatever gets printed is then also, food safe. The oils, microparticles, residue from other filaments, glue or solvents on the print bed, etc all in the printing path can contaminate, and the printed object itself can be unsafe just due to its geometry.

OK, ok, I’m a printing professor now, so whats the issue?

FDM prints cannot be sanitised (or sterilised²) because of their nature. An FDM print is layers of a thin plastic pattern laid out, they are normally hollow with an infill pattern. So the first problem is just the layers, every little bit of gunk and cruft easily sits in the grooves in between the layers. It’s not really viable to clean that fully, your only hope is soaking in something antibacterial which may impact the plastic itself. And then you’ve got to hope that the soak gets to all the problem areas.

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Depending on print quality, FDM prints may not be watertight, and so will have tiny gaps that allow ingress into internal spaces or into the infill of the print itself. This is why giving a baby a rattle that is FDM printed is a bad idea, they put it in their mouth, it gets wet, saliva can make its way to an internal surface, it does not dry and becomes a petri dish from mold etc to flourish. If the item is printed with an additive like glass or carbon fiber, those little particles improve strength and rigidity, but they make the print porous. I recently saw an online creator trying to print a car part that was meant to hold liquid, but his prototypes were inexplicably leaking. I let him know that because he was printing in a CF filament, that makes it porous, and so his leak was through all those micro channels.

Rope itself is unable to be sanitised you might be thinking right now. And I agree, its not, its a natural material thats fibrous, no chance. The distinction is that its hard for rope to long term hold a moist environment for biologicals to take hold, whereas prints can.

Another vector, is that FDM filament is often hygroscopic and gets ‘wet’ if not kept in very dry conditions. The water in the filament turns into steam in the hot end of the printer, and turns into bubbles in the plastic as it lays down. If the moisture is particularly bad, you can hear the popping across the room. All these popping bubbles make millions of uncleanable micro cavities, and can make porous paths to internals.

So, in essence, any liquid near a print, or any skin or other particles, are not really cleanable or sanitisable in a reliable way. Does this mean if you use an FDM print, you’ll immediately get an infection and die? unlikely. But, would you tie with ropes still damp with a little blood from someone who might have Hep C? Or feel ok to discover your toy you’ve been using is full of black mould?

So FDM is bad, got it, so we just need to use other types?

The resin used in MSLA printers is wildly toxic to humans before it is cured. Working with these printers is a pain in the ass and a real lesson in biological contamination and spread. One exposure to skin, in my experience, irritates with a burning sensation. Repeated exposure sensitises people to it and the reactions get bigger and bigger. If the resin is fully, 100% cured, this is not a problem. But, if you yourself did not print it, one of the common mistakes is to not design the print so internal spaces drain out any resin inside, so if the part ever cracks open it will bleed out this toxic goo. Also, personally, I find a lot of the consumer level resins to be pretty average strength wise, and if you leave them in the sun they uv degrade very quickly due to their nature. I would say they are safer than FDM prints, But not by a huge amount. If the item is big enough to need a drain hole so its not a little resin bomb, and that hole did not get resealed after cleaning and curing, its another cavity to accumulate nice moist problems. So they can be safer, but it depends heavily on the process of whomever printed it.

LBPF in a plastic I wouldnt really trust. Its made from a powder, you cant easily guarantee no micro voids. In a metal? at least you can make the thing really hot and sterilise it.

MJ is very rare at the moment, it remains to be seen what the risks are. But it is up and coming, there will be more and more of it in the future. It may be that it is like resin prints, less problems if done right and problems if not.

I ‘sealed’ mine

Who are you, Kenjaku? This might help if done effectively with the right sealant. A rattle can of clear spraypaint is not the right sealant. Anything that can flake, degrade etc is, in my opinion, probably worse than au naturel. It can be done, it’s kind of like putting lipstick on a pig.

Is any option actually, fully, safe?

You might have noticed I keep saying ‘less risk’ and ‘less problems’ rather than ‘is safe’. Thats because thats what I mean, I’m not espousing any of these options as safe. The only options I would say are safe are metal items that have been (CNC³) machined, and are not post treated other than by non additive chemical processes. These are not porous, have no coatings to flake or fail, and the metal is able to be heated, autoclaved, live its life in barbasol without a care, etc. Metal has no microfeatures to capture biologicals, no internal voids. So safety wise, in my opinion its gold standard. Bonus, anodysed aluminium comes in prettymuch any colour under the sun. As does titanium.

There is a caveat to metal, and that is if it is not one monolithic piece. For example, if the item is covered in spikes and those spikes are unscrewable, or it assembles with screws etc, then those are all places for potential issues to hide or be left uncleaned. Could downgrade a ‘safe’ item to ‘safe but needs proper handling’.

I would even accept machined plastic options as a reasonable alternative, since they do not have the micro features and voids etc of a print. Harder to clean than metal, cant heat it and the plastic might be susceptible to whatever antibacterial you wash it with. Its just more complicated, you have to be aware of explicitly what plastic it is, and look up the big old table of what solvents its susceptible to etc. You can get around this by buying things machined in plastic from PEEK⁴. If PEEK is viable for you, will you be my sugar Gender Inspecific Parental Title?

Another method would be casting, where a silicone mould is made and then a two part urethane or similar is poured in and cast in the mould. So long as it is done properly and degassed or done in a pressure pot, this is another method that avoids porous problems, voids. Similar problems to plastics, cant heat it, solvents may be an issue. In the case of silicone toys, I know a lot of women are savvy these days to the things to look out for, like cheap/bad silicones, pthalates, etc. High quality platinum cure silicones only, essentially. Minor thing to look out for, did the cast originally use an FDM print and replicates the surface texture as a result? No good.

I’ve never seen one in glass, but if you’re a glassblower and want to have a go, knock yourself out. It would be arguably as safe as metal.

Wood in the right species with the right finish like a penetrating oil would likely be ok, as while its porous its a bacterially unfriendly environment. Might be a little tricky to sanitise.

Is biologics and cleaning the only risk?

Unfortunately… no. The other identifiable problem but less likely to be an issue is flammability. Most FDM filaments are not fire safe and fire retardant, ie if they catch fire they tend to continue to burn and wont self extinguish. It’s in the realm of freak accidents, but people do play with candles and I could see a case where one accidentally sees too much fire inadvertently. There are FR variants of filaments, they are very uncommon. I have a roll of PC-FR here for printing enclosures for things like batteries, and its like buying an early ford. You can have it in any colour, so long as its black.

Metal has this wonderful property of being typically fully non flammable in our conditions.

I sold my house to buy nothing but printed toys!

The ones you have are not necessarily little guaranteed death traps. Be considerate of when and where they get exposed to moisture, potentially consider keeping anything you use on a person to be used only for them, as people do with items that may get blood on them, like impact toys. Keep an eye out for anything that looks off, funky, has a smell. Do your best to sanitise but know it may not be fully effective. Don’t sit around with one in your mouth to sooth an oral fixation.

If you read all this and want to buy one anyway, I would ask the seller what the material is. If it were me, I’d want a PA, or at worst an ASA. PA is Nylon and can cope the best with higher temps and a wide range of chemicals. Spoilt for choice, a PA12 over a PA6, its less hygroscopic and still handles temps up to 180c, so you could put it in boiling water, for instance. I would not hold much stock in PLA, which becomes plastic deformable at left-in-car temperatures, is less chemically resistant. PP would be an okayish candidate also but its somewhat new/rare as an FDM filament, and uncommon. Very chemically inert, but glass transition point is quite low, around 100c.

You make too many words funny man.

TL;DR. Printed toys are not necessarily safe, or can be made safe. The safest option is machined metal. The actual risk is relatively small, but not zero, and is likely above most persons hygeine threshold. The size of the problem also varies according to how the item was printed, not just what material it is.

Responsible disclosures

At the time of writing this article, I have no horse in the race, I do not sell any item like this and have no axe to grind or profit to make. In future if I find there is a market willing to pay for metal versions of these toys, I might decide to manufacture and sell, but have no current plans to. (Effort to profit ratio is not really there).

I am not making or implying any moral judgements on any persons or businesses selling these items, or people self printing etc. The goal here is purely Risk Aware Consentual Kink. Now you are Risk Aware, and better equipped to Consent.