Milling for Minibot??

Our team would like to make a custom aluminum base for our minibot. We want to produce it by means of milling. Is this legal? Does this count as an aluminum bar (as stated in <R92> H.)??

-Team 3316

Milling something out of an aluminum bar is permitted, because the rules doesn’t prohibit that machining method.

Just because certain types of aluminum bar are larger than what inspectors might be accustomed to seeing on a minibot, I recommend that you bring a receipt that identifies the piece of raw aluminum stock as a bar or sheet (and not a plate).

Thank you!!

This is quite interesting when you thing about it; in fact some parts could be made from the permitted aluminum stock…now it all depends on who made it. Perhaps it could be off the shelf, machined out of aluminum, but purchased.

Anyone else can fill in the rest of that.

As far as I know, the rules do not specify what machining or forming techniques you can use. The rules ARE specific about what materials you can use. And there was a discussion about what constitutes “sheet” aluminum, vs. plate aluminum. My guess is that if it’s less than 1/4" thick then it’s probably allowable as “sheet”, but you’d definitely want to ask on the Q&A to be sure.

I’d be looking into learning about how to design and build thin sheet metal structures, if I were working on that part of the project. Look at some past big robots built by teams such as 148 and 217 among others for inspiration. And think very thin sheet metal, as the minibot need not be very big or strong, and in fact probably wants to be as light as possible. In general, milling a huge chunk of aluminum is NOT the most efficient way to build something as light as possible. Also investigate how aircraft are built. Or old Airstream travel trailers. Or an Avion truck camper (which I’m in the middle of restoring right now!)

the difrence between sheet bar and plate is ambigous. people have claimed its defined by being rolled or extruded. others have claimed it’s a ratio between width and height. if you cut down a plate into smaller and smaller strips theoredicaly at some point it will be considdred a bar.

You can form or machine a sheet of aluminum into a bar, or channel, or tube, or many other shapes. It still started out when you purchased it as a sheet of aluminum, and that’s what the rule specifies.

Aluminum sheet is usually defined as < 0.25". Aluminum bar can literally be anything, but usually refers to something with a significantly longer length than its height or width in raw form (thus differentiating itself from plate); 0.25" x 1", 1" x 2" or 4" x 8" would all be considered aluminum bar stock.

Thank you all!! We’ll definitely consider all of your answers and suggestions.

Good luck to us all this season!

The GDC refined their definition of what an aluminum sheet is here:

“Raw aluminum sheet” is anything marketed as “aluminum sheet” that is not sold in pre-perforated or pre-punched form.

There is no thickness requirement…

Thanks, Mike! I actually just saw that exact Q&A thread.
So, that’s basically really great; we don’t need to worry about the thickness of the aluminum (other than for keeping the minibot light)