Food Safe Materials

[McCreator4Life 0]

Hi All,

 

Can anybody point me in the right direction to learn if any of the materials that the UltimakerS5 can use are food safe? When I say food safe, I also need them to be dishwasher safe. It needs to be able to maintain its food safe capability for the lifetime of the products. ABS seems to have these capabilities but can't find any information that specifically states this.

 

Best,

[gr5 2,173]

There are lots of food safe filaments.  But there is a more serious issue.  3d printing creates tiny layer lines where bacteria can survive a brief washing.  And worse, there's usually at least one tiny hole into the interior of the printed part where water can get in and stay for weeks to allow bacteria to grow.

 

Most food safe filaments come with the caveat that the material should touch food only once and then be discarded (never cleaned and reused).

 

If you are okay with this caveat, and if no one answers your question directly, let us know and I'll call in someone to the conversation who knows about this subject better than me.

 

As far as dishwashers - PLA slumps/softens around 52C and dishwashers often have a sanitizing feature where they heat the water to something like 55C.  Plus near the heater it can get to 95C.  So pick a material that can handle being heated to 90C.  Like ABS but ABS smells horribly so I recommend something else.  Maybe CPE+.  Nylon is okay but doesn't do great if submerged for days (it gets more rubbery but recovers when it dries out).  Also Nylon doesn't look as good usually and is a bit harder to print.

 

Most filament types (e.g. ABS or CPE+) have versions that are NOT food safe because of additives and also have versions that ARE food safe.

[McCreator4Life 0]

I was afraid that might be the case. If I can't get a filament material to be dishwasher safe, food safe, and lacks strange odors, then what about a post-print coating? Something I could dip the printed product into that can prevent the problems that the tiny layers and holes cause. It would also need to prevent the odor problem cause by the ABS (leaning towards ABS at the moment).

 

Nylon sounds feasible if I can figure out a way to make it look good. Which Nylon filament would be best given the previous constraints?

[gr5 2,173]

The odor is only during printing.

 

Please describe the part better.  Is it a bowl?  A cup?  A coffee maker? 

[McCreator4Life 0]

For the sake of simplicity, lets go with a coffee mug.

[gr5 2,173]

I don't recommend FFF.  Maybe a resin printer like the form 2 can do this?  I asked some colleagues to pipe in here but they seem to have chosen to say nothing. 😞

 

[McCreator4Life 0]

Ah, okay. Thanks for the info! I wish they would reply lol. I think I am set on an Ultimaker 5S because of its versatility and production capability.

[geert_2 557]

What about printing a mould, and then carefully sanding and polishing that mould, and casting your model in a food safe plastic? Then you still have the freedom of designing and 3D-printing, but you don't have the tiny holes in the final models. Use a low-exotherm, slow curing product, so the prints do not melt. And depending on the product, use a good mould release spray or coating so it does not permanently get glued into the mould.

 

[McCreator4Life 0]

That sounds like a nice option. How much would be involved with casting the model in a food safe plastic like HDPE or PET? Specialty equipment, operating space requirement, etc. Casting moulds would be a whole new world for me.

[kmanstudios 1,120]

There is also the issue of contamination in the printing process. It may be food safe going into the printer, but it may not be food safe after the nozzle.

[geert_2 557]

I don't think you can easily cast in HDPE or PET, that normally requires injection moulding. Most casting products are two-component epoxies, polyurethanes, polymethylmetacrylates (=PMMA, as in plexiglass and dental models), silicones, and similar. So they are often quite thin liquids, and then chemically cure into hard plastic or silicone. PMMA should be food-safe when fully cured, otherwise they couldn't use it for dental applications in the mouth. I don't know about fully cured PU. Most platinum-cured silicones are also food-safe, like in commercial baking moulds.

 

The basic procedure is:

- Design the mould in CAD, and print at highest quality. Make sure you can still open the mould after a solid cast is sitting in it,  thus no undercuts! Usually this requires a two-part mould. Or more parts if it is a complex model. Also design alignment-features into both halves, so they mate well without shifting. Provide holes or flats for screws or clamps to keep both halves together.

- Carefully post-process and polish or chemically smooth the mould until it is totally smooth. No layer-lines.

- Upon closing the mould, seal all seams, otherwise the liquid will leak away.

- Carefully and generously apply release-coating to the mould. Otherwise the cast will be glued permanently to the mould.

- Mix the components very well, and then degas them to remove bubbles. Depends on the products and their viscosity.

- Use low-exotherm products, so they don't melt the mould. Some PMMA can get extremely hot, and even melt metals like tin, or even catch fire or explode, if in too big quantities.

- Cast your mixed liquids, and let cure.

- Carefully demould, and then post-process: remove seam lines, etc.

 

Search on Youtube for moulding and casting: there are a lot of good tutorial videos. And they also describe the products they use. You will learn a lot, and see a lot of different techniques.

 

The main disadvantage of moulding and casting is that you have to work with chemicals: in uncured state they often smell badly, and may be irritating or poisonous like solvents. But once fully cured, they are almost inert plastics. And they can be messy and sticky when still uncured.

 

Note that silicone is watertight, because it repells water. But it is not oil- and solvent-tight: these leak through slowly. So you can't keep oils in a silicone cup or pot. Don't ask how I know...  🙂

 

Edited December 2, 2020 by geert_2

[geert_2 557]

I just think about it: if you want to make moulds, it is a good idea to have a look at manuals of injection moulding too. These manuals explain very well how plastic behaves when casted. And which guidelines to follow in mould-design. Although intended for injection moulding, a lot of principles apply to any kind of moulding. Search for: injection moulding manual bayer basf. And maybe other companies: most manufacturers of plastic pellets do have such manuals, available for free, because they want customers to be satisfied with their plastics.

 

[X-Type 2]

You can use PP (polypropylene). It is food safe and dishwasher safe. 

 

Print it with really thin layers and high temp and you will have have a very nice and smooth item and no issues. 

 

I have previously used PLA for printing objects used in food processing and hand cleaned it and it works great. Now I am switching to PP to get it dishwasher safe too.

Edited December 19, 2020 by X-Type