I’m very excited to share the product of only four days in the shop. We’ve been so prolific that I didn’t think one picture would be enough, so I went with four. Top left, some milling I’m particularly proud of, top right, the top of our powdercoated and riveted frame. Bottom left is a view of the shop Tuesday afternoon, and bottom right is a close up of our waterjetted and powdercoated electronics board.
Everyone on 100 has been very excited with our results so far. If nothing else, this is going to be one of our prettiest robots in a while!
(For those confused about the jump from #2.0*10^0 to #11, fear not. We’re using binary to in honor of the programmers this teaser.)
Looks nice, that’s a lot of progress for only a few days. In general, what kind of preparations do you make when getting items powder coated? We have never done this but may with our off season bot. We are also considering anodizing the frame and misc components. What made you pick powder?
We do too. I caught our head mentor, who’s been with the team for longer than I’ve been alive, digging the powdercoat too. Pretty much, I like weird numbering systems. I might throw a few logarithms in there too, just for good measure.
I’m a member at a hackerspace called TechShop, which has a powdercoating both and oven. We’re also sponsored for a few pounds of powder from Cardinal Paints (really great guys, by the way). In California, it’s really hard to anodize, as it’s basically illegal to dispose of the chemicals involved. Powder is a lot more benign than the anodizing chemicals too, and since our students do all the work, we wouldn’t want to expose them to stuff that’s too toxic.
Preparation is the most important part of powdercoating. We’ve tried a variety of methods, but the bottom line is that as long as the surface isn’t dirty, you’re going to get fine results. We sandblasted and cleaned the gussets with Simple Green, and for the frame members, we used an angle grinder with a wire brush or flap sander attachment to remove the layer of oxides from the metals surface.
For the actual painting, we just sprayed the gussets and baked them for like 10 mins. The lower frame we did riveted together, which didn’t turn out very well. We tried for two coats, but ended up over baking. This gave us some egg shell. For the top frame members, we baked them first, till they got to like 400 F, then sprayed them. The paint even melted on a bit in the booth, but we baked the parts for another three minutes just to get everything nice and glossy. The bottom line, once the parts look glossy, take them out of the oven. You can over bake them.
Are you guys by any chance creating a Poof style 2013 bot, sans the 30 point climber?
One comment on the gussets: Unless 1/8" was just material you had laying around anyway, you can definitely go with thinner plate for the gussets and avoid pocketing with the plasma (I’m assuming those were cut on a plasma because of the edges, correct me if I’m wrong). You could also just use a large radius on the inside corners to cut out material while keeping them very strong. Just a suggestion.
We did have some 1/8th lying around, but also some 1/16" stuff. We’ve always done 1/8" for gussets, I’ve just never liked how 1/16" is so flexible compared to 1/8". Well definitely try it some time in the future though, where the gussets aren’t taking much of the load.
We waterjetted the gussets ourself, although I can use the plasma cutter too. We prefer to use the waterjet because it leaves a much nicer finish than the plasma cutter and doesn’t tend to warp the part. On the other hand, we did have to pay by the minute for cutting time. Going to 1/16" on the gussets would probably save us a significant amount of money.
The poofs did show us the strategic worth of a fast floor pickup bot, but the design isn’t a copy of theirs (well, we are getting BBD from them, but you get the idea). Our design is closer to 1538’s. However, as a general rule, I really dislike simply copying successful designs. In my mind, there’s a lot of value in seeing what worked before, but making an exact copy of a design is just being lazy. There’s rarely a solution you can’t improve upon. We looked at robots with really effective pickups, did layouts in CAD, prototyped, and based our final design off our prototype. Our final design is inspired by others successes, but at the end of the day a product of our own hard work.
1/16" should work fine for a lot of gussets. We used 1/16" on our drive gussets, though we did have a 1/8" bellypan on the other side. 1/8" is very safe, though you should be able to convert 1/2 of your stuff to 1/16" if you really wanted.
Cool stuff, 1538’s was one of my favorites from this year. Good choice!
And yeah, definitely try thinner gussets on other places (.09 or .08 work too). On the plasma, you can’t get a great hole pattern, but if you finish it off on a drillpress it turns out pretty nicely for most applications. Might have to try various cut speeds and settings to get the best product on the plasma, but it’s definitely possible.
They’re 1/8" 6061 plate over 1/8" wall tubing in that frame. We’re using 3/16" rivets, they’re the same hole as #10 screws, which makes it easy. If you get the right grip, they’re extremely strong. Us using that many is complete overkill, by the way.
We’ve done welded once when I was on the team, and the two years I’ve designed the frame, we’ve used 3/16" rivets. They never gave out, even a lot less with a lot more stress in 1/16" tubing. I would highly recommend riveting, the only difference in my mind is that riveting can be faster and you don’t have to worry about warping things. Rivets are also much faster to replace than bolts if you have a pneumatic riveter.
However, this evidence is completely anecdotal. If anyone wants to post KSI yield numbers for riveted vs welded butt joints, please be my guest. I’d highly recommend at least trying riveting though, if it’s something you’re interested in as a team.