Back when I was a little freshman, I knew I wanted to study engineering. And not just any old engineering! I wanted to be a rugged spelunker tackling the world’s problems with math, programming, and elbow grease. However, by the end of freshman year, I was still lost in the big world of the School of Engineering, taking a disorganized sequence of classes with some sort of “E” in the title. I took a class in the BioE core, I took CS, I even took… a Chemical Engineering class! (I kid, it was very interesting).
Then, I took E40M. This is great, I thought, squinting at the soldering joint I’d just lovingly crafted. As I was huddled over my lab bench, I envisioned myself instead working out some wiring at a huge, flashy solar farm. I love soldering, I thought happily. I’d picked the major that would enable my McGyver-esque dreams: Electrical Engineering.
Exactly one year later, I was sitting in a different windowless lab room on the first floor of Packard: the infamous Packard 128, Digital Systems Lab. As my lab mates and I were searching through our Verilog modules for whatever had turned our functional music player into static, I asked myself “Why did I choose this life?”
Why did I choose this life? Because, at the same time, I was taking a class that enabled me to see inside my classmate’s skulls (EE 169, Intro to Bioimaging). Because of the satisfaction that comes with understanding something all the way down to the semiconductor physics. Because once you get a little taste of the signal processing behind wireless communication, you stop complaining about dropped calls and remain in awe that cell phones work at all, ever. Luckily, not all EEs need to be digital systems designers. (Shoutout to the ones who are. Y’all are amazing). I didn’t love every core class, but I came out with a hefty amount of knowledge, wonder, and respect.
I am continuously in awe of my classmates. My classmates are the kind of people that make plasma speakers for fun, find time to send balloons into space, and somehow TA two of my core courses while being in the same graduating class. I feel so lucky that I’ve gotten to learn with such talented, hard-working… intense people. We know it isn’t the easiest major at Stanford, but we’re in it because of the powerful things that we learn—concepts that allow us to manipulate the technology we rely on straight down to its core.*
Favorite engineering-related sources for inspiration:
Why did you choose to be an engineer?
Process of elimination
Palo Alto, California
During Autumn quarter this year, all of my class lectures were recorded and available online. I initially tried to attend every lecture, but the ability to skip class and watch it later was too tempting. I soon found myself waking up at 2PM everyday and watching all my lectures through the SCPD video system.
This lifestyle presented couple of problems. First, the SCPD player was annoying to use since bad internet connections would force me to reload and lose my place in the video. Second, I found myself rebooting frequently to switch operating systems – this would also cause me to lose my place. I could use the download feature on the SCPD site to solve the first problem, but the second still remained.
Instead of fixing my life, I decided to fix my technology. What I really needed was a video player that could remember where I left off. This would also allow me to split my lectures into parts and rotate between them (I found that this prevents me from getting bored while watching 2-hr lectures). I looked at a wide variety of video players, but I didn’t find any ideal solutions. Most players don’t remember positions, and those that do typically only remember positions on the last video viewed. Furthermore, I often switch OS’s (primarily OSX and Linux), and I want my timecodes to work on both (and ideally be synchronized). Given these constraints, I figured the only solution was to make my own tool.
I obviously didn’t create a video player from scratch – instead I used MPlayer, a GUI-less video player that is launched from the command-line. What makes MPlayer awesome is that it outputs video progress to stdout as the video plays. Using this feature, I was able to write a simple wrapper script to launch MPlayer and read/store the timecodes.
MPlayer is interesting since, as the video progresses, the application actually erases the previous line in order to write the new timecode. It does so using “\r” (carriage return) to return to the beginning of the line and rewrite the previous data. From there, it was as simple as splitting the stdout stream on that code and extracting the video position with a regex. The timecode is saved every five seconds. When the same video is opened again, the wrapper script uses the “-ss” flag to pass in the saved timecode.
In order to share timecodes between machines, the timecodes are stored in a folder in my home directory, indexed by the SHA-1 hash of the video file’s contents. I then set up that folder to be a symlink into my Dropbox and voila! Cross-platform synchronized video resuming in less than 100 lines of code.
This simple project shows how existing tools can be recombined to solve a daily problem and boost productivity. I’ve encountered tons of these little hacks (every engineer has a couple!) and I’m always blown away by the cool ideas that people think up. Leave a comment if you have any similar projects you’d like to share!
Varun is currently studying the Systems track, but also has interests in Software Theory. He’s interned at Facebook and a startup called Sourcegraph. In his free time he works on side projects and plays video games.
I was definitely excited to come to Stanford – the freedom, the community, the courses – but part of me worried that I wouldn’t find a close-knit group of friends like I did in High School. Within a few weeks of arriving on campus, I realized that meeting people at Stanford happens naturally and happens often.
The freshman dorm community is fantastic. After being dropped into the unknown world of college life, it became clear that everyone else had my back. Whether it was playing Super Smash Bros or pool in the lounge, horrendously failing at cooking in the kitchenette, or staying up way past my bedtime to watch House of Cards, everyone around me was actively trying to form bonds. There was a practically endless list of dorm events that left me chasing people with water guns or hiking a trail at Yosemite. Making friends is a freshman dorm is not only easy – it’s nearly impossible to avoid.
Outside of the dorm, Stanford has clubs and activities for every interest. Enjoy playing music? Join the Orchestra, Jazz Ensemble, a musical, or simply walk down the hall and you’ll find a few guitarists to jam with. Maybe you like to build things? Check out the Solar Car project, the Robotics team, or create your own design in the Product Realization Lab. My favorite aspect of Stanford is that regardless of your passion, you will find humble, talented people who have the same interests as you.
It’s natural to worry about finding your place at a university with thousands of people, but Stanford will become your home. You will meet people with similar interests and jam together, game together, build things together, or whatever else you can imagine. You will meet people wildly different from you, exposing you to ideologies you never knew existed. It is guaranteed at Stanford that you will meet people, and regardless of who you are, you will find a close-knit group of friends.
Jordan Hank enjoys learning guitar and photography, while he is also known to adventure out into the wilderness (hiking, rafting, fishing). He loves dogs, anything sports-related, and drinks a hefty amount of tea each day. Within his field of Computer Science, he likes to explore Unreal Engine and spends most of his time crafting and analyzing algorithms with a special interest in research involving P=NP.
In preparation for traveling throughout Europe for several months with very limited packing space, I have been seeking to adapt all of my needed electronics to Micro-USB charging of rechargeable cells. This limits the number of chargers and cables that I need to lug around. One of these devices, my noise-cancelling headphones, currently uses a single alkaline AAA cell.
Interestingly, a typical rechargeable NiMH AAA cell is not an option here, as there is not a secondary regulator in the headphones after the battery. The sensitive analog circuitry has a fairly narrow acceptable voltage range around 1.5v (V_typ for alkaline cells), precluding the use of 1.2v NiMH cells.
The challenge: in the cavity in the above picture, add a few hundred mAh’s of lithium ion cells and electronics to perform charging over USB and DC/DC regulation to 1.5v.
The space between the AAA battery and the top edge is free, so the plastic cover can be removed to install two 20x30x4mm lips cells (blue), providing 700mAh total. The electronics will be vertically oriented on the left (yellow), with maximum board dimensions of 17mm (long) x 11mm (tall).
For the electronics, a Linear LTC4081 was selected as the main controller. This chip includes a 500mA linear Li-Ion charger, and a 300mA synchronous buck converter at 2.25mhz for system load, in a 3x3mm package. The TI BQ25010 was a close second, with the added benefit of charging using the buck converter rather than linear. However the TI chip had slightly higher Rdson FETs and a larger package. The NTC thermistor option in the LCT4081 was, unfortunately, not implemented due to size constraints.
The only other important component selection was the inductor. As FET I^2R losses (and Iq) are the dominant loss modes, lowering ripply current is desirable, though most available packages are limited by the space constraints. A Coilcraft LPS3015-183, in a 3x3mm package was most suitable here, to achieve <20mA of ripple current.
The schematic and board design was made in Eagle, and are currently being manufactured at OshPark. OshPark is insanely nice for very small boards. Their service is 3 copies for $5/in^2, including shipping, and they pro-rate for fractions of a square inch. For no additional cost except additional lead time, 2oz copper and 0.8mm board thickness is now available; I chose that service this time. I paid $1.30 for these boards, though I try to send some larger jobs to them as well, since this job couldn’t possibly be profitable for them.
The result is a system that should achieve about 30 hours of usage (including DC/DC losses) in a similar form factor to the original, and avoids the need for pricey disposable cells.
I’ll report back and edit this post when I get my boards and assemble the final unit.
Friends mostly, arxiv.org
Alexander focuses on computer architecture (BS+MS) and systems optimization, but also has pursued power electronics. He will be joining SpaceX to work on power electronics in the fall.
While perhaps surprising, strange and/or ironic, the best advice I can give to aspiring engineers, especially those at Stanford, is, more than anything else, to explore. Stanford isn’t amazing because its Introduction to Physics class is the best class ever but because of the opportunities here and the people around you. I don’t mean the research opportunities even though Stanford spent $5.3 million on undergraduate research projects this year or networking with your peers (these are great opportunities are you should check them out!) but the crazy random things not related to your dream job, greatest passion or your major. Weird coming from a member of an engineering honors society huh? Hear me out.
Stanford is filled with the brightest, most passionate, and enthusiastic young minds in the world. And they’re all in your dorm! It is these future novel writers, world leaders, CEOs, activists, artists, musicians, etc. who can and will teach you the most. Ask any of your hallmates about their interests and you can have a multi-hour conversation more engaging than any lecture. You never know when their interests will create yours: I’ve discovered two hobbies and made two of my best friends this way. The first sprang from a late night conversation about martial arts transforming into taking Wushu and Combat Choreography classes and a lifelong passion for martial arts. A conversation about what music I enjoy quickly turned into a forced a cappella audition and my membership in one of my favorite communities on campus. My primary Stanford identity and the one I am most proud of is a freshman RA simply because I get to work, live, and learn with 97 of these inspirational beings. Additionally, the most impactful engineering experience I received was not a class or research on campus but going abroad to Kyoto where I started to discover my design aesthetic, had an opportunity to work at a company overseas, and witnessed the differences in the research, creation, and manufacturing processes between Japan and the United States. It is through these experiences that I better understand myself and how I want to make an impact on the world. My future plans are dramatically different from those I had before I started college and they wouldn’t be nearly as exciting and rewarding if I hadn’t taken the time to explore.
Therefore, I urge you to seek out non-traditional college experiences outside of the classroom. You have the rest of your life to master the skills that will propel your idea or your passion to success but only four years to learn and thrive in the most unique and wonderful environment in the world. Relish it, enjoy it, and graduate knowing that these magical years are behind you but truly inspired to spread your wings and soar!
Favorite engineering-related sources for inspiration:
“Life begins at the edge of your comfort zone.” – Neale Donald Walsch
One of my most vivid memories is from Bhutan, a small country snugly fit between two of the world’s most rapidly growing nations: China and India. Ten years old at the time, I was walking with my family on an unpaved road in the capital city Thimphu, when we encountered a chain-link fence surrounding a construction site. About fifteen yards from the fence were a handful of workers shoveling gravel into a wheelbarrow-sized cement mixer. With each toss of the shovel and turn of the mixer they uttered a resounding cheer, like a group of excited soccer announcers watching a penalty shootout. As we passed by, one of the workers cried out, “Hello!” between cheers. Surprised, we looked around, but when it became clear that he was speaking to us, we waved and said, “Hi!” in return; immediately afterward, their cheers changed to a chorus of “Hi!”, “Hello!”, “How’s it going?”, and other greetings. These cries carried on for quite a while, and it was quickly apparent that, rather continuing the conversation with us, they were simply sharing joy amongst themselves. Later on our trip, we learned that the Bhutanese government aims to foster an economy that maximizes gross national happiness, in contrast to the West’s focus on material development, which is often measured by gross national product. This context certainly shed light on our experience with the construction workers. It was amazing to see how redefining success in terms of happiness instead of material or financial gain could have such a tangibly positive effect.
While this policy has certainly had a beneficial effect for Bhutan, the technique of redefining success in non-traditional ways can be applied in a myriad of situations. For instance, it has helped guide my college experience, where I find that it isn’t difficult to confuse mastery and specialization with success. It is easy to feel successful when one’s research group makes a groundbreaking discovery, or when one’s sports team wins a conference title. Indeed, it is this sort of achievement that, for many individuals, justifies the countless hours of work and preparation. On the other hand, it’s harder to feel successful when pulling out a less-than-stellar grade in a class in a challenging and unfamiliar discipline. It’s harder to feel accomplished after struggling mightily at a new sport, only to make slow but incremental progress. Said alternatively, society rewards excellence. But can we redefine success to encourage the exploration of new things and the departure from our comfort zones?
This is a perspective that calls out to me, and one that I do my best to adopt; for me, college is a time to explore. Having dived into computer science and a cappella in my first two years at Stanford, I’m taking my first classes in philosophy and linguistics, and I’m learning the fundamentals of electrical and mechanical engineering for an extracurricular team project in water purification. In addition, I recently joined a non-audition hip-hop dance crew and am trying to learn to draw. I am a total beginner in each of these areas, but I consider my achievements to be the times when I am willing to stick with something completely new; in this frame of mind, overcoming a lifelong aversion to dance is just as remarkable as becoming an accomplished dancer. While many of these achievements may not be considered traditionally successful, they expand my possibilities for the future and are opportunities for personal growth. I don’t know where my college experiences will lead me, but I have no doubt that my exploration will continue long after graduation, and that in the Bhutanese tradition, I will not stray far from the path of maximal gross personal happiness.
Even though I didn’t take my first engineering class until college, I’ve been drawn to the natural sciences from a young age. Once I got to Stanford, I knew I wanted to build things.
Portola Valley, CA
Computer Science (currently)
Other than a year abroad in Beijing, Griffin was born and raised in the Bay Area. At Stanford he is a section leader for CS 106 and performs regularly with the hip-hop group Common Origins. In his free time, he likes to sing and play guitar/piano, and to find pickup soccer games across campus.
Last winter quarter I took ME 298: Silversmithing and Design which gave me a pretty awesome introduction into the world of small-scale manufacturing with precious metals like silver, bronze, and gold. One project that resulted from that class is the Skeleton Watch.
The Skeleton Watch is a silver investment casted watch housing designed to showcase the intricacy of an automatic mechanical watch movement. The open face and caseback allow you to enjoy the movement’s exposed jewel bearings, gears, and unique detail while the visible screws and faceted bezel are intended to give the watch a more “engineery” feel. The watch was originally modeled in SolidWorks, and prototyping, part validation, and RTV silicon mold creation was done via 3D printing. The molds provided wax parts used in the investment casting process.
My goal for this blog post is to give you a behind the scenes look into how I made this watch using an investment casting process. Below I’ve outlined 10 steps I took to achieve the final product shown above.
- Casting silver
- Watch movement
- Watch stem
- Watch hands
- Watch crown
- Machine screws
- Watch band
- Watch band pins
- Watch crystals
- Injectable wax
- Sprue wax
- RTV silicone
- Investment Casting Plaster
- Wax injector
- X-Acto Knife
- Casting machine
- Manual mill or drill press
- Watch band tool
- Various silversmithing tools (scalpels, kerosene lamp, etc)
- Various metalworking tools (hacksaw, files, taps, etc.)
Step 1: Starting with a sketch
After perusing through hundreds of pictures of different watch designs on Pinterest and Google images, I had an idea of what kind of look I wanted to go for, but I still needed to sketch my ideas out to translate what I envisioned in my head into something I could actually see.
At the time, the front of my CME106 course reader seemed like a good sketching surface. None of my resulting sketches were quality, but they were still helpful in understanding how my watch could look like.
Step 2: Making a CAD model
I knew I wanted an automatic mechanical movement (one that self-winds using your kinetic energy), so I found one that I liked on www.esslinger.com. Important specs I took note of where the movement’s thickness and total height. Using these dimensions, I then began creating a CAD model of my watch using SolidWorks, making sure the watch was big enough to contain the movement yet small enough to not look awkward on my wrist.
I made an assembly which included the two parts of my watch housing, the housing fasteners, the movement, and a cradle meant to secure the movement in the housing. Making the assembly helped to verify that all the parts fit together.
Step 3: Prototyping with 3D printing
Once I finished creating the CAD model, I 3D printed my watch to verify its overall look and feel. I wasn’t completely satisfied with a couple of details of my original design, so I 3D printed my watch again after making changes to the CAD model. I quickly assembled the new 3D printed watch to make sure that all the parts fit.
Step 4: Creating a mold and Injecting wax parts
In order to create the multiple wax parts needed for the investment casting process, I thought it would be a cool idea to create two separate molds, one for each watch housing part. I made the molds using RTV silicone, which is a very gooey substance, and the 3D printed pieces from before. The process involved pouring the RTV silicone over my 3D parts and letting the silicone cure over several hours. Once the silicone hardened, I then cut open the molds in half using an X-Acto Knife and carefully extracted the parts, which left their negative spaces in the silicone. I then used a wax injector to inject wax into the negative spaces. I had to play with the wax injector’s temperature and pressure settings a lot before I could successfully shoot acceptable parts.
Step 5: Spruing the wax parts to a wax tree
The next step involved creating a big wax assembly that resembles a wax tree. Unfortunately, I don’t have a picture of this with my watch parts, but I’m including one of another part I made in the class to give you an idea. This wax tree is necessary in the investment casting process because it eventually forms the negative space in hardened plaster after it is melted away in a kiln. This negative space is what the molten metal flows into to create the final parts.
My watch parts were connected to the tree’s “trunk” via sprues. These sprues are made of wax that should melt at a lower temperature than the wax used in the injection molding process in order to melt them onto the molded parts without deforming them. I used a kerosene lamp and some silversmithing scalpels in order to successfully melt the sprues onto my parts and then onto the tree.
Step 6: Investing the wax trees in plaster
Once all of my parts were connected onto the wax trees, I then had to invest them into plaster. The plaster started off as a powder, but once it was combined with water, it became a gooey substance that I poured over the wax trees, which resembled the silicone mold creation process. Unlike the silicon molds however, the plaster needed to spend several hours in a kiln in order to first cure and then allow the wax to be melted away, leaving the wax tree’s negative space.
Step 7: Casting the parts
After the wax was melted away, it was time to finally cast my parts. Molten silver was poured into the cavities left by the melted wax using a casting machine like the one shown below.
Once all the silver was poured into the plaster, I waited a few minutes for the silver to cool. I then purged the plaster in a water bucket, which enabled me extract the newly casted tree. Below is a photo of what the casted tree looked like.
Step 8: Cleaning up and finishing the parts
I separated my parts from the tree using a hacksaw, and a grinder was then helpful in removing the attached sprues. My next step involved drilling all the holes for the housing screws and the watch band pins on a manual mill. After drilling the holes and tapping those for the housing screws, I then preceded to sand my parts with 500 grit sandpaper until they were shiny. I didn’t use a higher grit sandpaper because I wanted to achieve a brushed look that matched the buckle on a leather watch strap I bought.
Step 9: Assembling the watch
Once I deemed my watch parts ready, I attached the watch crystals to the parts using epoxy. Next, I attached the watch hands to the movement using tweezers, which was a very tricky step and required patience and several tries. An important thing to note is that when applying watch hands, make sure both the hour and minute hands are lined up at 12, otherwise your watch will tell time incorrectly. I fastened the top part of the housing to the bottom with a screwdriver and then screwed on the watch crown after trimming down the movement’s stem. After attaching the straps to the housing using the watch band pins and a watch band tool, I was finally done with assembling my watch!
Step 10: Enjoying the watch
In the end, I was really happy with how the watch turned out and was quick to show it off to my friends and family. The entire process was long and arduous, but I felt it was more than worth it since I learned a ton along the way and ended up with a cool piece of self/hand-made jewelry.
That’s all folks! I hope you enjoyed this behind the scenes of the making of a casted silver watch and also hope this inspires you to make some awesome stuff using a similar process. If you have any questions about the product or the process I used, feel free to email me at firstname.lastname@example.org. Thanks for reading!
Pinterest, Stanford Product Realization Lab (PRL)
I wanted to make products that people could use and enjoy.
Daniel Espinel is a second year ME graduate student with interests in design and manufacturing and also studied ME as an undergraduate at Stanford. Daniel enjoys making most of the resources provided by the Stanford Product Realization Lab to create different things, and on his free time he enjoys playing and watching soccer. You can learn more about Daniel and his work by clicking here.