Food safe 3d printing?

[Angus Gratton]

Has anyone experimented with food safe 3d printing techniques?

I picked up a used coffee grinder that needs a plastic part
replaced. I was thinking about designing the part and printing it, but
it has to be safe for near-permanent contact with food (coffee
grounds). It doesn't need to be mechnically strong, or withstand
extreme temperatures.

Reading online, it looks like the usual technique is to print in
common ABS/PLA/etc and then apply a coating of food-safe epoxy or
similar (either designed for food products, medical use, or possibly
for potable water).

Does anyone have any tips on products available in Australia? I've
found a lot of US trade names but nothing that I can definitely buy
here.

The other leads I've found so far are suggestions of using water tank
sealer coatings, or kitchen benchtop coatings. I haven't looked into
how well these would adhere to ABS, mostly because they seem kind of
expensive ($100 per 1L tin is the smallest I've seen).

Cheers,


Angus

[Clifford Heath]

Does anyone print in HDPE? They make milk bottles from it, so it’s food-safe.
Also, I heard of someone making their own hot-melt plus sticks out of recycled
milk bottles, so it definitely extrudes.

Clifford Heath.

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[Clifford Heath]

Gah sorry, hot-melt glue sticks (damn you auto-correct)

[Angus Gratton]

On Mon, Apr 20, 2015 at 03:52:24PM +1000, Clifford Heath wrote:
> Does anyone print in HDPE? They make milk bottles from it, so it’s food-safe.
> Also, I heard of someone making their own hot-melt plus sticks out of recycled
> milk bottles, so it definitely extrudes.
>
> Clifford Heath.

Hi Clifford,

Interesting suggestion, thanks. I think some of the RepRap
experimenters have used HDPE, although the wiki page is discouraging:
http://reprap.org/wiki/HDPE

Aside from material composition, there's a second factor to food
safety that I didn't mention before. FDM printers don't produce a
smooth surface. There are very small voids - impossible to clean -
where bacteria can grow.

Someone on the reprap forums posted some interesting microscope shots:
http://forums.reprap.org/read.php?1,164077,167669#msg-167669


Angus

[Zac Faragher]

You could try surface finishing the HDPE in a similar way to using acetone vapour on ABS.

I'm not sure which solvent is best to try, but here are some starting points:
http://www.researchgate.net/post/What_is_the_effective_method_for_dissolution_of_HDPE_and_LDPE1

Angus

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[tubular]

At one point Dave and I were joking about printing using "ice magic"

There's a food innovation centre at Ringwood with a number of high end 3d printers.  They should know because they'd have the real world incentive to drive such a thing forward.   I'll see what they say

I'm also meeting up with the quickparts guys sometime soon and will ask the same.  

I suspect the answer will be that you need to line it with something.  Vacforming? 

[Rob Gannon]

According to reprap.org PLA is food safe.  Also,  PET filament is available, which is commonly used in drink containers.

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[Stuart Young]

The problem with food safe printing is making sure the whole path and environment is safe and free of contamination, not just the plastics.

Dirt, hair, etc getting trapped between layers is a problem. You also need a completely food-safe path for the filament, from the spool, drive gear in the extruder, and the hot end, and it would need to be cleaned regularly. All metal parta need to be food-grade stainless or similar metal (brass does not cut it).

Add to this the issues with small voids and ridges where food/grime can get trapped and lead to bacteria growth, and it rapidly points you at using a coating process as mentioned earlier, over a print base made in a food-safe material on a printer made food-safe is about the best option.

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[Angus Gratton]

On Thu, Apr 23, 2015 at 06:39:13PM -0700, tubular wrote:
> At one point Dave and I were joking about printing using "ice magic"
>
> There's a food innovation centre at Ringwood with a number of high end 3d
> printers. They should know because they'd have the real world incentive to
> drive such a thing forward. I'll see what they say
>
> I'm also meeting up with the quickparts guys sometime soon and will ask the
> same.

Thanks heaps Lachlan. I'll be interested to hear what they say.


Angus