Using Markforged 3D Printers for BattleBots
BattleBots is a television series where teams design, build, and operate 250lb remote-controlled machines that fight in a hazard-filled arena — the BattleBox. The show began in 2000 on Comedy Central, and its impact has spread worldwide. Dozens of amateur competitions occur every year where anyone can build and fight robots sized from 150 grams to 250lbs. Now, the show airs on the Discovery Channel, with its newest season premiering this Friday, June 7th at 8PM EST. In the past two seasons, I had the opportunity to build and compete on BattleBots as part of team Valkyrie.
What continuously captures my interest in robot fighting is the endless design compromise because every class has a strict weight limit. Do you add weight to weapons for bigger hits? To armor for better defense? Electronics for more power? In each design you must carefully balance your weight budget to build what you view as the optimal design. I entered the robot fighting community in 2016, starting small with a one-pound robot called Foiled. Initially just a fun side-project to test the durability of Markforged parts, I slowly became more and more involved in robot fighting, competing in over 15 competitions in the past 3 years. As part of a team of Boston-area engineers we built robots ranging from 1lb to 30 to 250, and eventually we landed a spot in BattleBots’ 2018 season with Valkyrie.
When the robots scale up, you have to prepare for your bot to get tossed 12 feet in the air, crushed by 35,000 lbs force, or smashed with a 60lb disc spinning at 2,000RPM — and still work afterward. BattleBots has a strict 250lb weight limit. At this size, robots often have aluminum or steel frames, with steel weapons and armor. Valkyrie’s weapon, for example, is cut from AR500 steel — the same material they use for snow plows and armored vehicles. So the compromise becomes more important and more expensive if you don’t balance the scales correctly.
Any weight saved in one area of the robot can be applied to another. For example, a lighter drivetrain could mean thicker armor, which gives the robot better defensive options. But everything also adds up in other ways. If you focus on a heavier weapon, you may need to sacrifice support elements of your drive train, which could increase your motor failure rate, so you need to buy more spare motors. If you strive for a lighter frame, you may need to spend more on materials and manufacturing, taking up more money and time and making the part harder to reproduce if it breaks. This is why we looked to Markforged when starting to design and build Valkyrie in 2018, and further improve the design for the 2019 season of BattleBots.
Markforged printers provided a wide range of materials to choose from depending on the specific needs of the part. In each case, Markforged allowed us to design optimized and lightweight components than we would have otherwise had to produce with heavier materials and more time-intensive manufacturing methods. We could print shock-resistant Kevlar® enclosures for our electronics, parts as strong as aluminum at a fraction of the weight, or geometry-optimized metal brackets to squeeze into low-clearance spaces in the robot.
In all of these cases, we were able to save weight but conserve strength. Valkyrie would be a smaller, weaker robot without 3D printing. We only had a handful of weeks to prepare for the season, so any fast, automated manufacturing method was a huge burden off our shoulders. We sent parts off to the printers without having to worry about making it ourselves, meaning we had more time to focus on the human-essential tasks like welding, machining, testing, and assembly. It also meant we got more sleep.
As a relatively new team compared to many builders who have been competing for decades, we knew we needed to move fast and iterate quickly if we wanted to match the top-tier talent. Markforged printers helped us design smarter throughout the entire process. To prepare for the 2019 season of BattleBots, we printed over 200 parts. Here are four areas where the printers helped us work quickly and efficiently:
Valkyrie is a sleek robot with many oddly shaped geometries that, when combined, make everything just barely fit inside. Before we start manufacturing any new part of the robot, we print it first and install the printed part on the robot to make sure it fits the way we need it to.
Tooling and Fixturing
Since many of the elements of Valkyrie involve complex contours or compound angles, we used 3D printed parts for workholding to set the components we machine up correctly when we make them. This ranged from soft-jaws for machining sprockets, to drill jigs for aligning and tapping holes in the frame, to indexing jigs for job setup.
Valkyrie has 55 3D printed parts installed, made in a range of different materials. Twelve of those parts were metal — primarily brackets and supports that interfaced with the armor or motors to maintain rigidity. Nine parts were Onyx FR to protect parts from any of the flamethrower bots we may fight. The remaining 34 continuous fiber reinforced parts included shock-resistant electronics casings, dust-covers, and structural supports that played key roles in keeping Valkyrie functional during a fight.
With a strict weight limit and a tight build schedule, Markforged printers allowed our team to offload a lot of the manufacturing so we could focus on other tasks at hand to get the robot working. We knew that we could create tough, reliable parts that would hold up in the BattleBox — through all of our fights in 2018, only one part broke. Many of the parts helped us save weight in critical places by designing them to be the optimal geometry necessary to perform.
On-site Repairs and Improvements
It’s my personal opinion that there is no perfect BattleBots design — there is always room for improvement and iteration, no matter your experience. The only way to learn how well a design works is in the BattleBox. Things are expected to unexpectedly fail during fights, so the best robots are the ones with lots of fights under their belts: their builders have discovered and resolved many failure modes. Some of these fixes are often done on the fly, with solutions hacked together from scraps. Others get documented and implemented for the next season.
At the competition, Markforged provided 4 printers to support the 67 teams that competed this season. With a 1-2 day turnaround between fights, teams could identify problems with their robots, design solutions, print them out, and install them on their robot before the next fight. Instead of making temporary repairs or having to settle with design flaws throughout the entire season, teams could make lasting parts with the strength they needed by either printing replacements or modifications to further improve the robots for the next set of fights - so robot performance actually improved as the season went on. Overall we printed over 160 parts for 29 of the teams there.
All in all, using Markforged allowed us to push the limits of Valkyrie’s design. We could iterate and improve quickly, test new concepts, and do more with what we had to create a powerful, sleek design. Catch BattleBots on Fridays on the Discovery Channel starting June 7th at 8PM, or Wednesdays on the Science Channel starting June 12th at 8PM. Tune in to see how Valkyrie fares!
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