I print something nearly every day, and over the last few years, I’ve created hundreds of practical items. Parts to repair my car, specialized tools, scientific instruments, the list goes on and on. It’s very difficult for me to imagine going back to a time where I didn’t have the ability to rapidly create and replicate physical objects at home. I can say with complete honesty that it has been an absolutely life-changing technology for me, personally.
But to everyone else in my life, my friends and family, 3D printers are magical boxes which can produce gadgets, weapons, and characters from their favorite games and movies. Nobody wants to see the parts I made to get my girlfriend’s 1980’s Honda back on the road before she had to go to work in the morning, they want to see the Minecraft block I made for my daughter. I can’t get anyone interested in a device I made to detect the algal density of a sample of water, but they all want me to run off a set of the stones from The Fifth Element for them.
As I recently finished just such a project, a 3D printed limpet mine from Battlefield 1, I thought I would share some thoughts on the best practices for turning fiction into non-fiction.
Getting the Model
Before you can print it, you need to model it. Or ideally, have somebody else model it for you. Generally speaking, when it comes to games or movies that have a considerable fandom, you should be able to find 3D models to work from fairly easily. Unless it’s something obscure that only you and your circle of friends are into, there’s an excellent chance somebody has already slaved away at a high-quality 3D model of it that you can base your project on.
If you’re lucky, you can find a suitable model in the “Prop” category of sites like Thingiverse or MyMiniFactory, ideally something that even has some pictures of the final painted product to give you a guide. These models might not be 100% suited for your needs, but they’re likely to get you pretty close and beat having to start from scratch.
If you can’t find what you’re looking for on the usual sites, and you’re serious about getting the thing made, you might expand your search to sites like CGTrader or Renderosity. But keep in mind that these models are not always suitable for printing. There are many people out there who simply 3D model things from their favorite fictional universe for the fun of it, and never intend on actually printing it. This is characterized by models which either don’t have appropriate real-world dimensions or have far too much surface detail to be printable on your standard desktop 3D printer. You can still use these models, but they’ll need some work.
In a perfect world, you’d find the exact model you needed and it would be printable without jumping through any hoops. But we don’t live in a perfect world, so more often than not you’ll need to fiddle with the STLs for the design you’ve found to get what you need. You’ll then discover if you didn’t know already, that modifying STL files sucks.
The problem is, STL files aren’t really meant to be modified. It’s very similar to how an exported image in GIMP or Photoshop is “flattened”, losing the separate layers used to create it. An STL is a single object, and it can’t be easily separated back into its principle components. Ideally, any model you download would also have the “source” used to create the STL, but in most cases, they don’t, so we just have to play the hand we’re dealt.
In general, this means you’ll have to load up the STL you want to modify and either add or subtract new elements to it to get the desired effect. For the limpet mine, I was lucky enough to find a nice model of it on Thingiverse, but there were certain parts of the original model I wanted to delete.
To make room to insert neodymium magnets inside the base so the mine, I imported the original STL for the base into OpenSCAD, created an array of short cylinders arranged in a circle, and finally used the
difference() command to subtract it from the original STL.
A similar trick was used to delete the “key” at the top of the mine, leaving an empty hole in its place.
Don’t Print What You Don’t Have To
That leads us to the next point: don’t waste time and material printing something you can otherwise source. Many of the designs you’ll find online will have nuts, bolts, and screw heads worked into the design. Printing these little details works well enough if you want to knock something out with the minimum amount of effort, but why not just use real hardware? Adding real hardware to your printed projects will give them a much more realistic final appearance, and all you need to do is put a hole in the STL to insert it.
For the limpet mine, I cruised eBay until I found an old clockwork key that looked close enough to the one used in the game and was about right size-wise to be in scale. Then I just stuck it into the hole created in the previous step. I didn’t even glue it in, the ability to turn and remove the key is a nice interactive feature of the final product.
I also replaced the printed handles with bent pieces of round stock steel and wooden dowels I hollowed out on the drill press. I was especially happy with this addition, as it gives the final mine a much more realistic appearance that would be difficult to duplicate with painted plastic.
The biggest part of creating a good-looking prop is unquestionably the finish work. Printing it, and even adding real hardware, will only get you so far. Unless you put the effort into sanding and painting the printed model, it’s never going to look like anything but extruded plastic and some bits of metal.
I’ve already gone into great detail about the basic approach I take to finishing 3D prints, so I won’t go over them again here. But there’s something I didn’t really mention in the previous article: things don’t always need to be perfect. In fact, they rarely need to be perfect. Real-world objects are often rough and dinged up, and you can use that to your advantage during the finishing process.
If you’re working on a weapon of some type, battle damage is really essential. If you’ve got a ding or nick in the print, consider using that to your advantage rather than attempting to fill it in. Try painting the low spot with a metallic color, followed by the final color on top of it. Then you can use some sandpaper to strategically remove the top color and expose the “metal” underneath. This will give the effect of a dent that caused the paint to flake away.
Similarly, if the object is meant to have a rough texture, don’t waste your time sanding the print smooth. A few layers of filler primer and texture paint will more than cover up the print striations.
Practice Makes Perfect
These are a few tips that came to mind while working on this recent project, but there’s more to building good-looking props than reading a couple of pointers online. Like any other skill, it takes practice to put these ideas to use. It’s something of a vicious circle: to get good at producing high-quality 3D printed objects, you need to keep making more of them. Your shelves will soon be filled with all manner of props and toys in various levels of completion. Of course, there are worse fates than being surrounded with neat little trinkets.
Do the good readers of Hackaday have their own tips and tricks for turning rolls of plastic into something worthy of display on your shelf?