Over the past few weeks I've been working with my school's AIAA (American Institute of Aeronautics and Astronautics) and ASME (American Society of Mechanical Engineers) chapters to use 3D printers in their prototyping and fabrication. The collaboration between all three clubs (with the addition of the school's 3D Print Club) was very effortless given that there are many overlapping members of the clubs, all three organizations share close lap/shop space, and the meetings for each organization fall back to back.
This season's rocket, a 12 foot, dual stage rocket with a 98mm lower motor and 75mm upper motor (or is it 75 and 54?), is modeled to fly to over 20,000 feet at a maximum speed of close to Mach 1.1. Given these numbers, having anything printed from ABS or PLA (or any FDM material really) would prove to be insufficient as the heat generated from the rocket's high velocity would demolish these low temperature plastics. Additionally, the shear and compression forces exerted on the rocket by it's rapid acceleration (it's got one heck of a 0-60 mph time) would similarly destroy any printed pieces. Due to this, all 3D printed components for the rocket internal, not major load-bearing pieces. Such parts include portions of the electronics bay, namely the central mounting plate which carries the altimeter, telemetry unit, and other electronic components.
However, there is one piece which is printed and is an ideal spot to take the brunt of the wear during launches and landings - the nose cone. Last year the nose cone tip was entirely 3D printed simply to make the fiberglass and carbon fiber fabrication easier (wrapping cones and tight-radius turns is no fun). This year, the upper half of the nose cone assembly has been printed, with the nose cone tip having solid infill. The rest of the cone is only a few layers thick, but is reinforced and shielded from heat and pressure by several layers of carbon fiber and fiber glass, with a section towards the tip being only wrapped in fiber glass. Whereas the majority of the rocket body is made of multi-layer carbon fiber, these section is only fiber glass to allow an antenna to be installed without any radio frequency (RF) interference. Carbon fiber is not RF transparent, meaning that it does not allow radio frequencies to pass through it. Having the 3D printed internal structure of the nose cone allowed us to easily create these RF transparent zone as well as a smooth transition from fiber glass to carbon fiber construction. It also let us exactly match the modeled profile of our nosecone, which has varied this year due to the possibility of flying at transonic speeds.
Right across the room from the rocket team is this year's UAV team. Each year ASME puts out a Student Design Challenge which focuses on the design and prototyping of a small vehicle/robot/device. These competitions are usually loosely themed on recent events, and this past years competition was in response to the outbreak of forest fires. A size-restricted unmanned aerial vehicle (encompassing lighter-than-air blimps, quadcopters/hexacopters, and helicopters) was to carry a payload through a number of gates, release the payload (a simulated water bladder to douse a fire), and fly back to the starting area. Given this task the university's ASME chapter decided to design and build a hexacopter - six small rotors at the ends of radial arms, connected by a central body. Many parts for these devices are readily available, but half the fun was in designing parts yourself so the team turned to 3D printing. To align and secure all six arms a two piece bracket was designed and printed on a Makerbot Replicator 2X, as well as landing leg adapters and feet for each arm. This cut down on weight and gave the team an immediately viable solution to many mounting problems.
The hexacopter competed at the regional competition at the University of Wisconsin - Madison against over 20 other teams. After inspecting the other vehicles it was noted that nearly every single one had utilized 3D printing technologies in their design, including one copter that's frame was entirely printed! It was wonderful to see evidence of 3D printing and rapid manufacturing techniques in each of these schools, all of which were roughly from the Midwest of the United States.
I hope to see more uses like these for 3D printing in the immediate future as students and schools are looking for more and more applications of this technology, and I hope you enjoyed this short narrative and case example for the current use of printing in engineering education!
- Cam
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