Big news that has Washington’s undies in a bunch is that Defcad.org released the “Liberator” 3D printed gun design for download. This article will attempt to dispel just a little of the smoke and heat generated by the 3D printed gun debate.
For quite awhile now, I’ve been monitoring 3D printer news and I’d make a rough guess that at least half the 3D printer related stories coming out over the last 6 months are talking about 3D printed guns.
I thought it was all pretty amusing – both the guys taking it so seriously that printing a 3D gun was tantamount to an act of civil disobedience by real patriots to protect their 2nd amendment rights and the opposite side freaking out that any Joe-six-pack can now print one out as easily as popping a Bud.
I think both sides are just plain over the top zealous and acting ridiculous. The Defcad videos are melodramatic and we know the politicians can easily match them toe-to-toe in melodrama (they have a lot more practice.) My goal is to take 3D gun printing out of the melodrama realm and try to inject some realism into the discussion.
Being a 3D printer enthusiast, not a gun enthusiast, I couldn’t help but be intrigued and curious to print one myself…as much as anything to show how absurd the fear is around 3D printed guns and to educate people who may have had their first exposure to 3D printing, unfortunately, by way of the gun control debate.
Fear #1) Everyone with a home 3D printer will be pumping out firearms
Fear number one is that all the home and hobbyist 3D printers out there are going to start printing guns straight off the download. This is an absurdity. Here’s why.
Massaging design files
I downloaded the Defcad Liberator and looked at the README and STL files. The first thing to note is that the STL files were created in units of inches, not millimeters which is interesting because a large number of enthusiasts with home 3D printers use Slic3r to create the code used to print on their printers, but Slic3r assumes millimeter based STLs. So the first thing you have to do is to massage the design files for unit conversion.
I loaded the Liberator STL files into my CAD package and re-exported the STLs out in millimeter units so Slic3r could ingest them.
Slic3r (pronounced “slicer”) is the most common software package used in the hobbyist level 3D printing market that virtually slices an object into layers where each virtual layer is an extruded (printed) layer of plastic on a 3D printer.
Slic3r generates code which is a huge list of commands to the 3D printer that govern things like how fast the 3D printed head moves over the layer, how the base platform should move in coordinated unison with the head, how hot the extruder nozzle should be, how much plastic filament should be extruded to get a certain length melted plastic bead given the speed of the head, and all types of other major and minor parameters that govern the print.
This generated code is called GCode. Slicing is practically an art form in itself when it comes to complicated objects, much like operating a CNC milling machine is an art form to a machinist.
Enthusiasts who have succeeded with a particular part could share their slicing configuration files or even the final code generated for a particular 3D printer (usually a variant of GCode), however, at this stage of the market evolution, there are a large number of different types of 3D printers, all of which need to be targeted explicitly by a slicing package in order for random Joe-six-pack to have the code he needs.
This is speed bump for 3D printing guns…you have to do the slicing yourself or find someone who has succeeded with all the parts and printed them on a machine identical to yours to be able to have a hope of printing a gun off the download. Even then, each machine often needs its own tweaks for the most precision it can muster.
Design limitations – Undercuts
The next major speed bump is inherent in the design of the Liberator itself. Most of the home and hobbyist level 3D printers can’t effectively print undercuts. Undercuts are design features in an object where there is open air under a solid feature. Think about a bookshelf – a cantilever pattern – is supported on one side (virtually the wall it’s attached to), but under the shelf is open air and nothing supporting most of the shelf’s surface area.
One example of the problem with undercuts is the Liberator gun’s frame part (the frame connects the barrel and handle, houses the trigger and hammer mechanisms.) I’m showing the frame here in an isometric view where it is laying flat on its side the way it would be printed, so you can see the undercuts I’m pointing out in the design:
These undercuts wreak havoc with most 3D printers in the hobbyist price range (< $2,500). You can’t print into thin air and trying to span across segments often leaves terrible drooping plastic filament.
Imagine something as far from a precisely machined firearm as you can, say a squirt gun left on a hot dash in the summer, and you are getting closer to the right idea of what most home and hobbyist 3D printers would do with undercuts.
Undercuts and 3D printing technology limitations
In order to effectively print parts like this with undercuts, you need what’s called an STL (stereolithography) printer or other much more expensive technologies. Even with STL printers, you often have to add support in order to print the parts. It’s not an accident that the Defcad Liberator started life with a leased 3D Systems printer…3D Systems owns some of the most important patents for STL.
With the exception of FormLabs’ (yet to be released) STL printer, most STL printers are way, way out of the hobbyist’s price range and are more the size of a refrigerator than a laser printer – in other words, not suitable for most homes. This won’t always be the case, but for right now, it’s a terrible exaggeration to think home 3D printers can easily print parts this complicated…STL capability is not in their price range right now.
2.5D – Most 3D printers Are Not True 3D Printers
Many of the home and hobbyist 3D printers that gun control zealots are afraid will be pumping out firearms are not true 3D printers. They’re more like a 2.5D printer. They can’t create an object in thin air. They always start with a solid base and melt layer upon layer to form the shape (fusion deposition modeling – FDM). Once they’ve melted a layer, they are unable to go back and put anything under that layer which is what makes most 3D printers effectively 2.5D printers…that is they can only build up in a vertical sequence much like a traditional skyscraper being erected.
If the undercut is too overhanging – typically less than 45 degrees from horizontal – it cannot be effectively printed without adding support to the printed part to hold up the suspended feature. Later the support is removed (filed, broken, or ground off) after the print is complete.
For my own 3D printer which is typical of a home and hobbyist level printer ( a LulzBot AO-100 ), I need to tell Slic3r to add support to the design when it generates the code for the print. In effect, it creates a matrix of material, hopefully relatively thin to break-away later, in order to hold up the overhanging, undercut features. What you end up with is a Liberator gun frame that will look like this as it’s printing. The thin walls are the support that will be later taken off the frame but is there to hold up higher solid layers that have yet to be printed:
As the print progresses higher and higher you can see the middle solid rib starting to form and that layer is laid over the thin supporting walls so it isn’t printed into thin air. As you can see, once this part is completed on the printer, it’s far from a finished part.
Time to Print Can Be Exorbitant
Just the Liberator frame part above will take over 6 hours to print and I would expect to take another several hours to get it filed or shaped into a semblance of a usable part and get rid of all the supporting ribs. If you don’t own your own printer and take the files to the copy shop that’s providing 3D printing services, if they’ll even take your job, you’re likely to pay by either time or part volume or both. After this part, while it’s the largest, you only have 14 more parts to go.
A Gun Is A System Of Precision Parts
I don’t think I’m going too far out on a limb by stating the obvious: a gun is a precision machine. 3D printers in their current form and especially those at the hobbyist level cannot produce precision parts on the level of a metal machining process. So, what are you left with? Who knows? Most 3D printer hobbyists don’t cite their precision and tolerance stats like a true machinist would.
Besides precision, you need replicability. Can you make the same part the same way, time after time? You can make one part that might work once. Can you make a system of parts repeatably? The print is likely to happen over a period of days and shifting environmental conditions which affect the 3D printer itself. It’s a system. If you have to file parts, usually by hand, how repeatable is your process?
Would you trust your life to a weapon for which the manufacturer (you in this case) can’t truly control the tolerances and conditions under which it’s built? I certainly wouldn’t and I think anyone who does is out of their mind.
A Single-Shot Life-Span
A single-shot gun is probably only interesting to the guy who needs to get a weapon past a metal detector by making it out of plastic. To be generous, the Defcad README states that if you soak your barrel in boiling acetone for “~30 seconds” (like that precision?), the barrel will be smoother and last perhaps up to 10 shots. Of course, this assumes you can get 10 shots of ammo past the same metal detector. The bottom line, for this weapon to be useful, you must hit your mark on the first shot which I find ironically counter to all the gun debate heat about the need for large magazines. In this case, you don’t need a large magazine either – either your gun will disintegrate after the first few shots or you can’t get that much ammo past a metal detector in which case, you don’t really need a plastic gun much less a 30 round magazine.
Materials – Have A Material Science Degree?
Most hobbyist 3D printers print ABS plastic or PLA plastic filament. Of the two, PLA is known to be quite brittle and it has a lower melting point than ABS or Nylon. Nylon is starting to be more common, is stronger than ABS (under all conditions?) and is a more smoothly printed material. The problem is that most hobbyists are fairly clueless about the material science behind plastics.
Don’t get me wrong, I am ignorant as well of material science, however, it scared the B’Jesus out of me when I read the question on the Defcad Liberator page in the comment section from some enthusiast: “Have any tests been done on these printed with PLA?” Somebody was wanting to know if you could print a gun with one of the most brittle, lowest melting point plastics available for 3D printers.
I know little about the chemistry of plastic, but I know enough to know that was a highly ignorant and dangerous train of thought along the same lines as the soldier who ties a tourniquet around the neck of a comrade with a head wound.
A tourniquet is a great thing, a life saver when used correctly. PLA is a great thing when used correctly and it’s biodegradable. However, when applied incorrectly, both become deadly.
The Most Dangerous Part of a 3D Printed Gun
If you’re going to make a gun, you have to know what you’re doing and that’s really the most dangerous part of this – the guy between the computer and the chair or the one printing it is likely to not be up to the standard required to design and print safe guns.
The gun is dangerous in the hands of the shooter, to the shooter. You can do the stand-off, string-pulled trigger stunt like MythBusters a few times and then you have to put your own hand on the grip (that’s after you change the barrel of your 3D gun since they usually only last one round). That’s not exactly what I would call extensive testing.
I can see the whole range of accidents coming that will shut down 3D gun printing a long time before an actual aimed kill does. Despite the 100K downloads in the first two days of the Liberator being published, 3D gun printing has a long ways to go before it is lethal to anyone but its shooter – if he can even print so far as to put a bullet in it.
That is the state of 3D printed guns and why gun control advocates have little to fear and why 3D printed gun advocates need to watch what they’re doing.
[Update: the print completed, you can see how much work there is to do yet on this one part. Using a .3mm layer height, 0.8 density fills, and relatively fast travel times, this print still took over 6.5 hours]