PS70: Intro to Digital Fabrication

<div class="textcontainer"> <h3>Week 3: Hand Tools and Fabrication</h3> <h4>Kinetic Sculpture</h4> <pre class="margin"> When I first realized we were making kinetic sculptures, I wanted to make sure that mine was clean and inspired by something. I was worried that doing a directionless project would mean that I wouldn't be motivated, so I chose a concept that interested me based on a Greek myth. That myth is of Tantalus, who, for several different reasons may have been given a punishment by the gods to stand in a pool of water below a fruit tree, but each time he reaches up to grab the fruit, it pulls up away from him, and each time he dips to get water, the level drops below his reach. There is a real beauty to this myth, the idea that one can sometimes never get what they wish they could have. That makes it tantalizing. When transitioning this thought to a mechanical system, it is interesting to put the human beliefs onto it. I wanted to explore what it feels like to make a machine that can never get something because it is just out of reach. Thus, the idea for my kinetic sculpture was born, from an appreciation of art, philosophy, and mythology that would help me stay inspired by a very human experience during my engineering work. So, I present to you...Tantalus.</pre> SCRATCH WORK <img src="./scratch work.png" alt="Scratch work" style="max-width: 100%; height: auto;"> <pre class="margin"> At first, I did not know how to go about creating the sculpture, so I went into a notes app and started drawing out all of my ideas. Obviously, the key was that wherever the arm was aiming, the fruit and water were no longer there. When I first drew it out, I imagined some sort of spring system that, as the arm swung around, a bar behind the arm would press the water or fruits away right before the arm moved towards it. I quickly realized that the more moving parts I included, the more chaotic this design could become very fast. I then turned to the world of gears, in which I was creating a sort of rack and pinion system that would move up and back as the arm moves. Quickly again, I scrapped that idea, realizing that not only had I not spent the time yet learning about gears and gear ratios, but also that if I only was able to move the motor one way at any time, the whole piece would tear itself apart in a perhaps beautiful display of strength that would end in the arm getting to its goal, but ripping itself apart (how poetic). Then, I had lab, in which we investigated different gear systems. The scotch yoke came to my rescue and that night, right before I was going to start manufacturing the parts, I learned how to translate rotational movement into linear movement, and the pieces worked out in the perfect way to swing and arm around on the gear, while moving other pieces up and down just out of reach of the arm. </pre> DIAGRAM VIDEO <video src="./diagram video.mov" controls style="max-width: 100%;"></video> Documentation: <pre class="margin"> I went right to designing, and decided that I should learn a bit more about joins and animating join relationships while trying to understand the conditions in which a scotch yoke can work under real life forces of friction. I found <a href="https://www.youtube.com/watch?v=Ij-fUrsoY9Y&t=437s" target="_blank" rel="noopener noreferrer" style="text-decoration: underline;">this video</a> to be very useful in my design, and, having followed it, I scaled it up, modified it slightly to fit my use-case, and ended up creating this animation in fusion 360. It moved well, so then I decided it was time to put it into real life. </pre> CARDBOARD SETUP <img src="./cardboard setup.png" alt="Cardboard setup" style="max-width: 100%; height: auto;"> WOOD SETUP <img src="./wood setup.png" alt="Wood setup" style="max-width: 100%; height: auto;"> ART SETUP <img src="./art setup.png" alt="Art setup" style="max-width: 100%; height: auto;"> Documentation: <pre class="margin"> Models in the 3D modeling software needed to be converted into laser cut models, and for this project I decided to use something that would withstand the amount of friction the parts were going to undergo. I was concerned about cardboard and the fact that the texture is not consistent along the cut faces, and after doing a test cut with cardboard just to find my proper scale, I switched to wood and got cutting. The 3 mm plywood was perfect for the job, and I was able to get good cuts more consistently than cardboard. The pieces turned out to be durable and also consistent, so once I got them cut I worked on the art. Because the motor would have to spin up several wooden pieces and then fight through the friction of the yoke, I decided to make sure that the art itself was light. I chose cardboard for its manufacture because it didn't need to be as durable, it would just be spinning or shifting at the whim of the wooden parts. I designed some 3D pears for the fruit section, found a reference image of the arm and used splines to sketch it out, and finally got it finished. The pictures above show the process of me going from cardboard to wood to art. </pre> YOKE MANUAL TEST <video src="./yoke manual.MOV" controls style="max-width: 100%;"></video> YOKE FIRST RUN <video src="./yoke first.MOV" controls style="max-width: 100%;"></video> Documentation: <pre class="margin"> The first pieces I printed out were just the yoke and a rudimentary base, which I miscalculated slightly in terms of the material bending inside the laser cutter and ruining some of my cuts. I adjusted, however, and figured out how to get the pieces cut more consistently. Still, that first iteration (with the help of the scroll saw to clean up some edges), helped me get a manual representation of how the yoke would move. With that success, I decided to cut the rest out with more reliability, gather it all together with some hot glue and nails, and get it running. I hooked it up to the bench power supply, and everything moved exactly how I hoped, if a bit fast because it was powered with 5V. The system worked well, so it was time to get to the more advanced part of the project, and get the art attached while powering it through my laptop and the micro-controller board so that in the future I can control speed and direction of my dc motor. </pre> MOTOR SETUP <img src="./motor img.png" alt="Motor setup" style="max-width: 100%; height: auto;"> CIRCUIT SETUP <img src="./circuit img.png" alt="Circuit setup" style="max-width: 100%; height: auto;"> FINAL SCULPTURE VIDEO <video src="./final video.MOV" controls style="max-width: 100%;"></video> Final Reflection: <pre class="margin"> At last, I got the kinetic sculpture to run, and, having connected up the circuit with a potentiometer in order to attempt some speed control using my 3.7V laptop power supply, I took the final video of the piece in action. Overall, I would say that I am very pleased with how it came out. One of the things that I had to get over was the fear that things would not work the first time. In fact, during the time I spent in the lab, designing components, printing, making mistakes, fixing mistakes, and then putting it all together, my successes took far less time than my failures. At first, I was worried about this, marking it as a sign that I could not do it and it would not work. However, seeing it all work in the end makes that time spent that much sweeter and I believe that I have cut back on that fear of failing the first time. The iteration process was so much fun, and it was really cool to upgrade from material to material as each part functioned how I wished, even if there was some level of luck to my design. It all ended up looking almost exactly like the drawing I first did by hand, which I was pretty proud of. Another key learning that I experienced throughout this process was that more pre-planning will help me in the long run. I included an image of how the motor is attached to the wooden base for a reason. Those are nails for wood, a way to secure the most movable component in a solid way. I tried nuts and bolts, attempted to tap a screw hole in the base, but in the end I chose simplicity. It was a tough process to patch over my earlier mistakes, since in the 3d modeling process I could have considered the fact I would need to secure it, but it was a combination of some savvy woodwork and extra parts that allowed the whole thing to work properly. At least I did build in some redundancy to my laser cuts that would allow me some cushion to make mistakes and fix them right up. There are also other parts that did not work out as expected, but I fixed them, again, with the backup/old versions of parts. Still, I am very happy overall. The sculpture moves how I wished it would, and it has the effect that I was looking for. I wanted it to feel like a human experience, one that could be a punishment for stealing the nectar of the gods and deserving of divine retribution. Something so tantalizing is to see the fruit and water just out of reach, and I believe that this work encapsulates that feeling well. It turned out cleaner than expected, and I think watching it move is so cool. I am glad that I got to learn more through this experience about hardware, and look forward to upgrading it in the future with more pre-planned hardware and some software to go along with it and take it to the next level.</pre> </div>