Jonathan Anderson

In mechanical engineering, materials undergo a tensile stress test in order to evaluate the material’s strain under a load. By stretching and breaking materials, we can find their limits as well as their potential for performance.

I think we as people find our capabilities and limits similarly by stretching ourselves, failing, and learning from these failures.

I had kept a fractured aluminum 6061 specimen from a college lab that had been stretched to failure on an Instron machine. It serves as a constant reminder that though failure is usually not the intended outcome, failure can be a productive means of learning.

One on my first CNC milling projects was to make a “failure trophy” that would mount the fractured specimen in a brass housing. This was one of my first experience using an adaptive toolpath in Fusion360 that pushed the tool’s performance. To form the center cavity, I used a 1/4" endmill that was taking 3/4" axial, .04" radial passes at 18 in/min. This was my first “big” cut into metal on the Tormach.

As the brass was machined away, the middle of the brass bar deflected a small amount. The rigidity of the brass bar decreased as thickness was machined away while the vice pressure stayed constant, allowing for some deflection. The toolpath ended up completing successfully, but this project taught me that it’s important to take into account workpiece rigidity which changes as the metal is being cut.

It ended up turning out pretty well! The press fit of the aluminum pieces into the brass bores was pretty much perfect, and the engraving turned out clear.

Overall, I learned a lot about mine and my machine’s capabilities and I’m proud of the end result!