Make-it-a-Mold Choclifier (1-piece vacuformer for shopvac)

THESE INSTRUCTIONS SHOULD BE FOLLOWED BY ADULTS OR UNDER ADULT SUPERVISION.  

So there are no good vacuforming rigs out there for 3d printers, probably because you can't make a good vacuforming rig with a 3d printer!  You can, however, make a better one than the ones available.  This one prints in one shot, unsupported (well, I supported the vacuum port) and can be used to make mediocre chocolate molds of your favorite 3d prints.

You will need:

1. high-temperature filament.  I went ABS.  This is actually my first ABS print, and it sucked, but it still worked.  Everything is a learning experience.
2. 1/8" (0.125") O-ring material.  Well you don't need it because I uploaded a version without (as well as the Solidworks file for your reworking pleasure) but I'm definitely glad I included it.
3. 0.010" to 0.020" acrylic sheets.  I used 0.020" because my wife's chocolate molds are made out of it.  Thinner would definitely be easier.
4. A shopvac with a 1.25" hose or adapter.  I used a Datavac and it worked fine.
5. A source of heat.  For 0.020" sheets a heat gun is inadequate.  I used a propane torch.
6. Candymelts (basically colored, sweetened cocoa powder or “white chocolate”) or chocolate
7. Corn starch

Method:

Print the model (I recommend using the one with the o-ring).  At 0.6 nozzle, 2 shells and 15% fill it's going to use uhhh about a quarter of a roll and it's going to take like eleven hours.  Cut o-ring material to fill it; no need to be precious about the alignment because this whole rig is about to get really sloppy anyway.

Connect your choclifier to your shopvac.  Take your mould model and place it in the center of the choclifier. OPTIONAL: spray model and choclifier with cooking spray, food-grade silicone, etc.  I am unconvinced as to whether this makes a difference after a half-dozen test patterns.

Cut a piece of acrylic bigger than you think.  After all it's going to warp and smear and misbehave.  Peel off the protective films.

Put the acrylic on a thermal backer (I used a torch tile) and hit it with your heat.  Work smoothly, work calmly, and work it until it stops wiggling - it's going to dance like it's in pain for a while while the uneven expansion causes it to warp and bend.  Heat as evenly as you can until it sits there limply.  Don't go too much beyond that or it will melt to the surface.

Use your backer to tilt your now-very-hot acrylic onto your choclifier.  It will cool down and harden at a frustratingly quick pace.

Turn on your vacuum and get your torch.  Work from the outside and do what you can to get the acrylic to melt down onto the o-ring - this will radically improve the vacuum and therefore the forming.  You are adding heat to thermoplastic at an incredible pace, be careful.  

Gently work your way in to the model - the plastic will suck around it.  Do not focus heat too much in any one place.  If the acrylic starts to get shiny and wet looking, congratulations, you have just melted your acrylic to your choclifier (or model).  This will happen, but try to minimize it.

Touch things up until just before you think you've taken things too far (it will take practice).  Turn off the torch, let the vacuum run for a few seconds (if you're lucky it'll make a different tone as the suction gets better) then turn it off.

Remove the choclifier from the vacuum and take it over to the sink.  Run cold water on it - this will cool your recently-molten acrylic as well as your hopefully-not-molten choclifier. 

 Peel the model out of your mould.  There's a definite compromise between “ease of removal” and “quality of moulding.”  Let it dry and let your choclifier cool.

Heat up chocolate/candymelts per instructions.  Sprinkle cornstarch on the mould - a good way to do this is to use a tea strainer and tap it gently (I used an enamel sifter, which is totally not worth buying for this project).  Glorp chocolate into the mould and put it in the refrigerator.  It will take longer to cool than you think.

Turn the mould over on a cutting board/countertop and WHACK it.  The chocolate should come out.  It might also break.  Congratulations, you just made some gnarly-looking confections!

TIPS

(note that I had this idea when the contest started and haven't had that much time to work out the bugs so consider these soft suggestions rather than iron-clad rules)

• Good moulding patterns are flat with relief.  Bad moulding patterns have lots of overhangs and recesses.  The plastic will suck into those recesses, bond real good and hold onto your mould forever.
• If the choclifier isn't cool to the touch when you start, it's gonna start melting when you make the next mould.  I was able to do three in a row but the fourth one is gonna return the ABS to push-it-in-with-your-thumb softness.
• If you don't know how to use a propane torch, don't learn on this project.  The melting point delta is about 30 degrees C.  Don't worry, you'll make a mess long before you'll start a fire but it's pretty frustrating to slag a part you spent eleven hours printing.
• Models can be cut in half by importing them into Prusaslicer, “sinking” them to the centerline, copying them and rotating them 180 degrees.  They can then be glued together with more chocolate.  Or, masking tape if you're in a hurry to take photos and your wife is too busy making Thanksgiving to fiddle about with your projects.

PRINT FILE/STLs

• This works for Hatchbox ABS, in an enclosure, with a 0.6mm nozzle, with the Prusa-supplied glue stick.  I think.  I did mine with stock Prusa settings and no glue and it warped like crazy.  It still worked, though, and I don't need two of them.
• I strongly recommend the O-ring.  However, if you don't wanna wait, go to town.