I've designed and made several interesting parts, but this has been one of the bigger and more difficult ones. This electronics bay ("ebay") is designed for an underwater robot (ROV) for a robotics competition. It needs to house electronics, be able to dissipate a few hundred watts of heat into the surrounding water, allow easily servicing the electronics, and perhaps most importantly keep the water out.

After some prototyping and back-and-forth with the EE folks, this is the design that we came up with:

Left: full assembly in CAD. Right: The ebay body machined from a single piece.

The body needs to be machined from a single piece of aluminum. Several people have asked why I didn't fabricate this by welding a plate on the bottom of a tube. Project cost is the biggest factor there - the size of tube needed would cost about the same as a 8" round bar stock, not to mention welding time and the additional complications that might arise due to heat affected zones in aluminum alloys. So, machining it is.

Started with this 8" piece of round bar. Moving the stock around was one of the more difficult parts of the project. The first step was hollowing out the "bucket" on the CNC. Nothing very exciting there, and looks like I didn't take any photos. Instead here is the CAM for that:

I do most of my design in SolidWorks and use HSM for most CAM. It has support for 3/4/5 axis machining and does most of what I need. For really odd parts, I use MasterCam but I've been doing that less and less lately.

Milling a deep pocket with a 5" long end mill is bound to leave an unpleasant surface finish. I roughed out the part on the mill, then I fabricated a long and fat boring bar to bore it out. The surface finish in the end product is much better.

Here is what the CAM looks like for half of the outside work and some shots from machining it:

I'm using a Haas VF-3 with a rotary attachment, both of which are about my age.

And here's the finished part:

All the machining was done over 2-3 days in March 2020. Something very unfortunate happened around the time this part was done and everyone went into lockdown due to the global pandemic and the project had to be set aside. I'm hoping the project will continue in the 2021 season and this part will provide useful.

This project was done for the CWRUbotix ROV team. Get updates from them here!