There is no question that additive manufacturing technologies like 3D printing are going to be game-changers in the aerospace industry and manufacturing in general. In the past, most components for aerospace were made using subtractive manufacturing. Processes such as drilling and facing remove material from a piece of stock to reveal a part. Naturally, this leads to a lot of wasted material. Furthermore, to create all part features, multiple processes may be required—one side may need to be faced, two sides may need to be drilled, and one of those sides may need to be counterbored. Already, four different processes are required to create the listed features, processes that cost time and money. With subtractive manufacturing, some features such as cooling channels in turbine blades are practically impossible to make. For this, manufacturers rely on castings, a basic form of additive manufacturing where molten metals are poured into molds. Still, the molds must be made using subtractive processes, presenting the same dilemma as before.
Enter 3D printing. Technology like 3D printing works by depositing layers of material onto a surface to build up a three-dimensional body, much like stacking LEGO bricks to create a much larger model. Of course, rather than depositing large bricks, 3D printers deposit fine layers of material as little as 20 microns in thickness one layer at a time. Because each bit of material is added to a part rather than removed, any physically possible feature, externally visible or invisible can be created using 3D printing. Better yet, the entire part can be created in a single process (not counting finishing processes and coatings) without having to change tooling or part orientation. The process is not instantaneous like printing off a document on an inkjet printer, but it is comparable to the time it takes to make a part with multiple features using subtractive processes. The technology also minimizes wasted material since only necessary material is added to a part. Current 3D printers can make parts out of a variety of materials from thermoplastics to aerospace metals. (It is worth noting that each printer is compatible with a narrow band of materials, so your average desktop 3D printer can’t print a metal nozzle. You’ll need a much more expensive Direct Metal Laser Sintering (DMLS) printer for that.)
The cost of 3D printing has dropped significantly as the technology has developed. You can get a basic Makerbot 3D printer, which prints using ABS or PLA thermoplastics for about $2,000. The models shown in this post were printed in PLA using Makerbots owned by Georgia Tech, and you can see that the quality of the parts is pretty good.
If additive techniques can be applied to so many different fields, I figured why not bring 3D printing into rocketry? Not to be confused with addictive rocketry, which I have found to be an also-truth, additive rocketry has proved to be quite useful in making a variety of parts for my rocket fleet. I’ve made a replacement nosecone for the SpaceX Falcon 9 kit (download my model for free) and a custom transition unit for 3.9 inch body tubes that the Georgia Tech Ramblin’ Rocket Club stocks to 3 inch body tubes. Unfortunately, I have been unable to flight test any of these components, but they appear to be much sturdier than the paper components I typically work with. I am currently in the process of designing an entire rocket to be 3D printed. Since the printer work space is limited, the rocket will be printed in three 6-inch segments and glued together where appropriate, but no other assembly besides parachute, shock cord, and motor installation is required. I am excited to see how it performs.
I am also using 3D printing for my Level 3 project. Rather than using composite skin reinforcements or tube stiffeners, which are either out of my realm of expertise, are too costly, or both, I intend to use 3D printed plastic stiffeners to add strength in shearing situations. This simple, cheap, and lightweight solution promises to add strength where extra strength is required so as not to cause shearing tears in the thin cardboard couplers. I hope this will also aid in accelerating the shear failure of my nylon shear pins during parachute ejection. Below is a picture of the stiffener for riveted inserts. (I’d like to be able to disassemble the rocket for transport since I have a small car, but I’d like it to stay together for the duration of flight.) Each riveted joint will be bound by two rows of 0.163″ nylon pop shank rivets in a hexagonal formation.
I used a similar design for the shear pins. Each shearing section is held together by three #2 nylon screws. These stiffeners are designed to be glued to the interior of a 5.38″ cardboard tube coupler so they don’t interfere with the coupled fit. The shear pin stiffeners are shown below.
Not pictured are some 3D printed drill guides for drilling holes for the rivets and shear pins. Since precision alignment will be critical for the proper function of the stiffening inserts, I took the liberty to print out the tooling to make the job easier. Yet another great use for 3D printing in rocketry!