3D Printing Dicks

First off, I don't recommend outright using printed sex objects, they're stiff and take a lot of effort to produce a less comfortable toy than you'd get from just making a mold and casting a silicone one, but if you want to anyway, this is how to do it right. We'll be using PLA for this just because it's the easiest to work with and the filament you are most likely to have some of on hand.

Step 0: Tools Checklist
3D Printer (duh)
PLA Filament (match your printer's built size, usually 1.75mm)
Hot Air gun (must reach at least 200c)
Dish Soap
An old toothbrush
Patience

If you use supports you will also need:
Nail Files
(Optional but helpful) Needle Files
Plastic Snips
Even more Patience than before

Basic steps: Find/Make, Print, Refine, Smooth, Clean, and Test



----------Step 1: Find or Make
You can design your own using a CAD program, 3D Modeling program, or a simple modeling program like Tinkercad, or you can download one from a website like Thingiverse or Tinkercad (again). Either way these are the pitfalls and design faux pas to watch out for.

1: No sharp edges/corners or overly pointy tips
This should be obvious, but it's also a pretty easy detail to miss. Blunt shapes are your BFF.

2: Make sure it's fairly straight
after 30° it will pushe uncomfortably on inner walls in use. In sone models this can be fixed by playing with the scaling a bit, but can cause other problems like once blunt bumps becoming sharp.

3: No deep crevasses on the business end
These make it hard to smooth your print and to clean it after use.

4: Ribbing OK, exessive bumps not so much
Friction is something not everyone remembers is still a thing even after smoothing the skin of the print itself, repeated bumps can create unwanted friction and places for Bacteria to hide.

5: Make sure it has a mushroom top on the handle end  (C=>)
Getting your toy stuck inside is the WORST thing that can happen. Don't do that, prevent it from the start by keeping it from going in further in the first place.

---------- Step 2: Print

When you get to the slicing stage of things, you want to minimize the number of support pillars, as well as the layer height, while you maximize print durability while balancing infill and print time. Preferably you'd be able to print without any supports at all, but some designs are just too complex for that.

These are the settings I changed over Cura's defaults that got the best overall results for my model of choice:
1mm layer height
3 layer walls (if using a 0.4mm nozzle, that's 1.2mm)
30% in fill (helpful for the smoothing step)
Line supports, over print bed only (align print at an angle across slicer grid to make them easier to spot and remove the lines)
Reduced print speed by 5mm/s (for a cleaner, more detailed print. in my case, 55 to 50.)

---------- Step 3: Refine
This is the most tedious part of the process, but if you got a perfect print and didn't use supports you can skip this and move on to Step 4.

First, You have to remove the supports. using your snips, cut as close to the print as possible to minimize the amount of time spent filing your print down.
Next, you have to file down the edges and bumps from the supports, and those that may have developed from the printing process, get these marks as flush to the "skin" of your toy as possible. Ideally you'd have both needle files and nail files for both fine and broad refinement.

---------- Step 4: Smooth
As in our case we're using PLA, smoothing is a matter of hitting your print with enough hot air to force the top layer to melt, turning visibly glossy and smooth. With ABS this can be done with Acetone and a brush but that's a more difficult to do right.

In my case, I set my hot air gun to 200°c and started heating one spot until it turned glossy in the light before slowly working my way around it until every angle was glossy. Let it cool at least until it's safe to touch. Don't heat an area for too long or you may cause the wall layer to collapse in, ruining the print.

---------- Step 5: Clean
Wash your print and scrub well with a toothbrush and dish soap to remove the chemical residue from the printing and smoothing process. This is also the first litmus test for if your print is smooth enough to use safely, if water rolls off every surface of your new toy, it's smoothed out enough to not gather bacteria when used, making it safe for use. If it doesn't roll off and instead beads up just go back to Step 4 and try smoothing that area again, if that doesn't work you may need to refine that area a bit more, smooth it once more, then try again.

---------- Step 6: Test
You are your own best test subject. Start by rubbing your fingers across it, you shouldn't feel any scratching on your hand, then rub an area with your thumb, if you smoothed it out well enough, your new toy should squeak when you rub it. Now is the fun part, prepare it with lubricant and slowly slide it in. If you've gotten this far and followed these instructions exactly it should slide in without pain. Congratulations, you've produced your own sex toy! Have fun. :-)