Rockets and UAVs - Oh My!

   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

A Take on "Entry" Printers

  The most prominent 3D printers on the market today are what I would deem "entry" level printers.  They are affordable, simple, and readily available.  Starting around $300 dollars these printers can be found everywhere now, from Amazon to Staples and at every major university and hackerspace.  I myself own one of these little printers - a Prusa i3.  For only $500 dollars I was able to assemble a pre-cut wood frame with all the hardware and electronics needed to make my very own 3D printer, and I was up and running within a single day.  But why haven't these little machines taken off and replaced modern manufacturing as we know it?  What's stopping them from reaching the "printer in every home" goal of Bre Pettis, the successful leader of Makerbot?

  As I see it there are three key factors holding these machines back and preventing the common consumer from simply downloading and making everything he or she could ever need.

1) Reliability 

   The success rate of my prints is abysmally low by any manufacturing standards - and I've been tuning continuously for the last 6 months.  Unfortunately there is no such thing as a simple "plug-and-play" printer right now - each one will need some care-taking to remain running smoothly.  But to the hobbyist this probably isn't as much of an issue since the aim in owning a printer for them is not just to use the printer, but is the experience of working on the printer itself.

2) Quality

  For most FDM printers the current advertised range of z-layer resolution (the thickness of each layer) is between 0.1 and 0.3 mm.  By comparison, the resolution of the Objet Eden350 is a minuscule 0.016 mm.  That's  over 6 times as detailed a finish as that from a consumer printer, but even though this comes at the cost of well over $100,000 it's the quality and resolution which is required for professional prototyping.  Now some low end printers can in fact get down to 0.05 mm resolution, but only after months of fine tuning, often by one who is very proficient in FDM machines.

3) Knowledge

  Few people are aware of the prevalence of 3D printers, and even fewer have a working understanding of them.  For an individual to just pick up a printer at the store and expect quality prints within hours is unreasonable, but that is the promise large printing companies such as Makerbot are giving.  Even Makerbot printers, which are marketed as an easy-to-use, reliable machine, have their faults.  The same issues that plague other printers such as bed adhesion, temperature settings, vibration, and constant readjustment and leveling still affect the Makerbot.  So when people expect these machines to work great right out of the box but end up fighting them for months they become deterred from the holy grail of home manufacturing that was pitched to them.

4) Applications and Expectations

  There tends to be a "honeymoon" phase when it comes to printers in which the user ends up printing every overused toy, trinket, and gimmicky item they have files for.  After that interest in the machine fades as it becomes just another tool to be used in specific situations in the shop.  So unless the user is a continual tinkerer or DIYer the effective applications soon plummet, resulting in the negative stigma of printers being only good for those trinket items.  But if that user does have a significant use for their printer it can be an invaluable tool for model prop making, test fitting, and affordable replacement parts, among other things.

The problem arises when the user has an unrealistic expectation of the machine's capabilities and applications.  3D printers are currently most effective and practical as tools - for the shop, for marketing, or for personal projects and design.  They should not, however, be expected to replace the entire process of model making in one fell swoop.  This is where the many people may turn to criticizing printers for not being wonder machines, while in fact the machine performed as was designed but was marketed to be something it's not.


So how should these problems be overcome?

  First and foremost I believe that the first step in remedying the image of rapid prototyping machines in the eyes of the vast majority is changing how these machines and their uses are perceived.  In their current state, entry level printers are not an end all be all solution to replace traditional manufacturing of parts.  It seems to me that any great decentralization of manufacturing will not come in the next decade, but rather in the next few decades.  Secondly printers need to be marketed and publicized as what they are - tools.  They are roughly on the same plane of equipment that CNC mills are, except they add material rather than remove it.  Finally they need to be produced at a similar quality across all price ranges.  A lower cost CNC may not have as many bells and whistles as a higher end one, yet it still performs the job without troublesome, job stopping issues.


I hope this didn't come off as too much of a rant, but the current state of 3D printers is one of misinterpretations, so I wanted to make points that are grounding (or even sobering) to the people who may not yet have extensive exposure to these machines.  I hope this was an informative post, I promise the next one will be in a much better spirit!


- Cam

A rapid prototype...of a blog post

 
I've worked with rapid prototyping technologies and equipment for a while now, but this form of a quick and cheap fabrication of ideas is a first for me.  I'm not a writer by any means, so this medium is quite new, but if it's anything like model prototyping, 3D printing, or rapid design then I think I'll be OK.  To give a bit of background on myself I am a second-year mechanical engineering student in Missouri, USA, with a love for 3D printing (I own a printer myself), modeling and animation, and any accessible and shareable science, engineering, and electronics projects.  These posts will be my way of working through projects, news, and ideas for myself, and hopefully I can make it an entertaining and educational read for you, too!

  For those of you who aren't familiar with this magic "3D printing", it's not nearly as complicated (or all-powerful) as you might think.  Most printers that the average individual is used to seeing is an FDM printer, which stands for Fused Deposition Modeling.  In this process molten plastic is Deposited in a programmed toolpath, Fused on top of another layer of material, to form a computer generated Model.  In practice this all just comes down to simply stacking layers of hot plastic on each other to make an overall shape (I often liken it to a "glorified hot glue gun").  The process usually takes anywhere from 30 minutes to 10+ hours depending on the size of your model, but unlike traditional manufacturing methods complexity is non-issue.  Additional complexity of an object adds an insignificant amount of time to the printing process.  For this reason (among others) rapid prototyping has really taken off in sectors dealing with complicated, one-off parts and pieces.

  My favorite example of using rapid prototyping to create complex shapes not achievable by traditional means is that of unique human and animal bone structure  recreation.  Recently the teams at the University of Missouri College of Engineering and College of Veterinary Medicine partnered up, taking CT scans of an animal in need of surgery, printing that animal's bones around the target area, and using those bones to practice the exact surgery.  This process greatly increased the chance of success for the operation by giving the doctors a way to practice which would have been impossible without this technology.  Normally it would be near impossible for even a skilled modeler to replicate the unique structure of that particular animal, but by taking and converting the data from the CT scan into usable model information a direct replica was able to be produced.

  This project was not done with an FDM machine, however, but instead used an SLS (Selective Laser Sintering) printer.  In the SLS process a vat of powdered material (normally materials such as nylon or metals) is fused together by a high precision and high intensity laser.  This is then repeated until all layers of the piece are fused.  After the part is finished it is post processed, with all the surrounding powder cleaned away.  This additional powder, which surrounds the entire part, serves as support material for the model.  With this SLS can produce structures with large overhangs, a feature that is often difficult for FDM machines.

  In addition to FDM and SLS processes there is also the SLA (stereolithography) process, which utilizes UV-curable resins, and various methods based on the layered binding of powders.  These make up the vast majority of 3D printing (or "additive manufaturing") methods, while FDM machines are often the most simple and affordable, explaining the recent flood of them in the consumer market.

  I hope this is enough to get you well introduced to rapid prototyping techniques, I'll inevitably dive into much that the area has to offer including materials, major companies, new technologies, applications, my own experimentation, and much more!

- Cam