September 23, 2019

How to Clone BattleBots Trophy with CNC Machining

By Steve Konick

Hockey awards the Stanley Cup. Football has the Lombardi Trophy. BattleBots, the Discovery Channel TV show that features robots that lift, shove, and sometimes puncture their opponents, has the Giant Nut. The trophy is awarded to the fiercest BattleBot, the one robot that could endure weeks of abuse in the BattleBox and still reign supreme.

Protolabs is the first company allowed to manufacture a copy of this highly sought-after trophy. But first, here’s a little backstory on just how it was made.

The Battlebots Trophy: Copying a Classic

It looks simple, but the actual manufacturing of this award was more complex than you might imagine. Nate Hirt and Mike Kankelfitz, Protolabs manufacturing engineers, were given the assignment to replicate a scaled-down version of the official trophy. It all started with their design in SolidWorks. Then, the CAD model was programmed into one of our precision 3-axis CNC machines to manufacture the part.

The metal of choice—Aluminum 6061-T651—is attractive, rugged, and lightweight. Even using this material, picking up the 8 in. tall and 10 in. wide replica trophy a few times will give you a good workout.


From Concept to Trophy

Starting from an original block size of 12 in. x 16 in. x 4 in., the first stage was to rough out the general shape, removing large areas of unneeded aluminum from the block. The profile was cut with a half-inch flat end mill and the face surfaces with a quarter-inch flat end mill. This process was done one side at a time, milling out the familiar hexagonal shape and round hole before flipping the block over to do the same on the second side.

Freed from the unneeded external aluminum, the process shifted to fine work, ensuring that the subtle curvature that appears in the six corners of the nut, and other features, be perfectly rendered. Here, they used a quarter-inch end mill. The face surfaces were finished with an eighth-inch end mill. Once that was done, lettering was engraved into the faces of the part using a small, high-speed end mill.

The Finishing Touch

The trophy looked great but something was missing. Nate and Mike wanted the trophy to look ultra-realistic, but they needed a special tool to create threads for a hole on that large a part. They used a 60 degree double-angle cutter and a helical interpolation toolpath to create the threads. While you can’t actually thread a screw through there, the thread pitch does resemble actual thread size. Once that was in place, it was time to finish the trophy. They used a light bead blast to remove milling marks and give the part a more neutral matte finish, consistent with the appearance of a nut.