pic: How It's Made: 148 & 217 Robots

[JVN]

Originally Posted by Akash Rastogi

John- would it be possible for you to put on a presentation in Atlanta this year, or even a powerpoint presentation up here on CD, detailing your design process in Sheetmetal in Solidworks? This question is also directed to others who use sheet metal fabrication such as 217, 228, 1771, 1477, 1902 and any others I don't know of.

I've been learning the features in SW but I don't know what works or what doesn't in my designs when, hypothetically, I would try to get them manufactured at a fabrication site. Are there limitations using sheet metal during fabrication? What are the advantages? (other than speed of fabrication, weight, duplicates)

Hi Akash,
I already have two presentation proposals in for Atlanta this year, so a third may be a bridge too far. I will work on a whitepaper for this off-season, I'll be sure to pester Paul to help me with it (the two of us working on a paper together would be fun... I think.)

The main advantage in using sheet metal for me is the versatility in design. I use it in 2 major ways:

1. Custom "extrusion" type pieces. You'll see a lot of c-channels, hat sections, question mark channels, and angles on 148 robots. These are made exactly the size we want, with all the mounting and lightening patterns already included.

2. Custom "shell" designs. There are years where our entire robot is one giant box section. This allows for some very rigid, very light structures.

The general rule I tell my students is "get your strength from your cross section, not from your material thickness." This means that if you do it right you can get a LOT out of very little material. Now we consider 1/8" to be "thick". I remember back when I was on a team that made their side-plates out of 1/4"! I distinctly remember Raul looking at our robot at Championship in 2004 and shaking his head: "Why so thick? Just add a flange it'll be 10 times as strong!"

Want to get really good at sheet-metal design? Learn the basic things your shop is capable of. Now learn basic strength-of-materials (I took this as a sophomore MechE at Clarkson). Apply the principles you've learned and think outside the box (or welded tube)...

Take a look at the Tumbleweed and Tornado CAD models. You'll see a few of the ways we utilize this awesome manufacturing technique.

Feel free to PM or email me if you have any questions. Shoot me a design, and I'll be happy to tear it apart for you. Keep at it long enough, and you'll be finding all the times I got lazy in my designs...

-John