The problem here is a little thing called "food safety". Is it really Health and Safety gone nuts?, well yes and no. There seem to be 2 main concerns with printed plastic products:
- The process in making the plastic may use chemicals that are not very healthy, or, the plastics themselves could contain compounds that are harmful.
- Crevices are present that may allow bugs to grow and you cannot heat the product to a safe enough temperature without the plastic deforming.
ABS plastic is made from crude oil based products. As such a lot of harsh chemicals are used to make it, and it contains a lot of unpleasant things naturally. If it is treated properly it is generally a good plastic to use for things like cutlery and cups etc, but the processes are designed and monitored to specific tolerances. Heating and extruding it in your printer is generally not seen as a valid process for ensuring food safety.
PLA is a "Biopolymer" which means it basically made from organic substances such as starch. Because of this it is seen as "green" and recyclable, and in the event you don't recycle it is also biodegradable. In itself, it is also safe, however when you add colour, stabilisers or chemicals to make it flow easier you start to throw doubt into the mix again.
Assuming you do find food grade extrudable filament, and you don't damage it though the extrusion process, the process of laying down the layers still allows for pockets and creases to exist that can allow bugs to grow if you don't clean your print adequately. ABS does smooth in an acetone bath so these creases can be minimised, but then you've just impregnated your product with acetone - known to not be very compatible with the human body, also you tend to loose a lot of detail in your print.
The other problem is that these plastic prints don't deal with heat well. Most hold their shape until about 70 degrees where they soften a fair bit. (ABS can go a bit higher). To effectively clean utensils, you generally need to get them above 68 degrees for a while which means there is a very fine line.
When you wash your dishes, the temperature isn't that hot though is it? But then the things you are washing are generally metal and ceramics.
Dish washing detergent has anti-bacterial stuff in it, isn't that ok? Again, on a smooth surface it's fine as it will dry off. With the creases and pits in the plastic these anti-bacterial compounds will settle in, and get into you next time you use them.
Is there an answer?There are silicone coatings you can apply, but this is fair bit of additional work and you can't really tell when it starts to come off. And remember the temperature thing, a coating will not help with this.
You can make your final product in ceramics. Shapways will do this from your 3D model, but it's not very cheap and you can lose a fair bit of detail. Stainless steel is also an option.
You could assume that Health and Safety has gone nuts and just use it anyway. Staying away from hot drinks, or things that bacteria like to grow in.
You could also just use the item as a toothbrush mug or ornament? Or better yet, just build a bottle holder:
While this is pretty much guaranteed food safe and it won't melt or sag, you can still do the same things for your favourite coffee shop purchased beverage. Since these drinks generally come in a cardboard cup that you can pick up with your bare hands, this means it's also under 70 degrees centigrade (I measured my the outside of my mocha at 46 degrees a couple minutes after it was made). Be aware though that these cups are designed for single use and should be disposed of afterwards for sanitary reasons. You could always ways get some cheap glasses from Tesco to line your cup as well. Remember though, measure twice, cut once... erm... well, print once.
A quick design note though: The rotational point of both an empty and full cup should be well below the top handle joint for stability. Here is the Costa 'Massimo' option. The best way to get your morning jolt of Joe in a cup of Nige.
If you're looking at food safety for actual food items, then get some cheap tupperware. If you wanted it mostly permanent then you can always make it so that the lip of the container fits inside a ridge.