Sheet Metal

Recently I have been researching sheet metal. Obviously it makes many more designs viable, than just 8020. Our team doesn’t have the ability to machine/manufacture a full sheet metal robot, but as leader of our CAD team, I hope to use a hybrid solution of square tube and sheet metal on our 2012 robot. I had a few questions to other teams, preferably ones that have used a design like the one I hope to use, or have done full sheet metal designs:

What would be the possible advantages and disadvantages of doing this?

What thickness would you recommend?(In general, but also for my specific idea)

Thank you so much.

2815 did this in a way in 2011–we used flat aluminum riveted to square tubing acquired from Lowe’s. We had plenty of other issues, but nothing with that frame. I could easily see a team pursuing this strategy if the limits of their equipment meant smaller pieces were an option.

Hybrid is the way to go. I like looking at 228 as one of the really good examples of hybrid sheet/tube done well.

http://team228.org/media/pictures/

As thickness goes, 0.125" will generally do all your fixturing/bracketing needs.

What resources do you have? Also, have you thought of bringing in sponsoring resources?

If you have the design know-how and a sponsor with a laser cutter and press brake, then by all means, sheet metal is an awesome way to go. However, it does take someone who is skilled in sheet metal design to come up with all the proper bends and flanges to get it all to come out strong.

Sorry that I was not clear. We are trying to secure sponsors, but this is our first year that our team is really taking off. We really only have a drill press and mill available to us. In leu of that, I was talking about doing something more like what Billfred suggested. Is it worth it to use sheet metal, even with our limited resources, and inability to make flanges.

Here’s one way to do sheet metal without a brake. http://2008.huntingtonrobotics.org/tutorials/monocoque.html

Thank you so much everybody. After doing more research, I have found what I want to do is build a full chassis out of square tube, connected with gussets and rivets, and with a supplement of sheet metal for it’s cleaner, more adaptable uses. Has any other team done something like this?

This actually isn’t all that uncommon and is a perfectly fine way to build a chassis. 571 has built frames using this method before: http://www.chiefdelphi.com/media/img/f29/f29a1d0cbc946593722189a59efd2731_m.jpg

A hybrid design is an excellent option, you will notice that most teams who build with sheetmetal still use “traditional” round or square tube parts. One idea that you might want to look into is the idea of nesting your drivetrain inside of a larger extruded aluminum tube. This can be seen on teams 177, 816, as well as the “Rock Box” from the 221 Robotics guys.

Other options include designing with standard C-Channel.

1/8" material thickness is common for sheetmetal and a relatively safe bet, some teams use thinner as well such as 0.090". In terms of alloys: Aluminum 5052 is great for bending and is what most of the teams that use sheetmetal use. For extrustions or flat plates/gussets 6061 is common and fine.

Again with all designs, always design within you teams capabilities… Expand your resources and then expand your design.

Our robot has several sheet aluminum covers/guards on it. I bent up several of them in an evening with a vise, hammer, and sheet metal brake. Aluminum is nice if you have few tools becuase it can be bent by hand somewhat. If you’re going to use fasteners aluminum is good but for welding, iron is so much easer.

Here’s a nice tip that I have found out, .125 does not like to bend .090 likes to bend. So if you are planning to bend go .090 but if not go .125. We have a break and it did not like the 1/8th inch alum. we tried to bend the other day, it bent but not very well the .090 bends very well from what we have seen.

This will vary heavily based on the alloy.

And it will vary even more based on the break…

With a dedicated sheet metal sponsor your team would have the ability to make low cost, lightweight, strong, easy to maintain drive train and manipulators. The big trick is getting the students to learn how to CAD up a drive train design and have a manufacturing engineer go through it with them to explain how to build it, how to make it lightweight, stiff and cost effective. The students have ideas sometimes good sometimes bad and it is the learning process while designing a drive train that is invaluable. With the proper instruction the 3D model of the design is used to program the laser cutter. the CAM engineer unflattens the model and createds the G code for the laser.

Learning about all the materials that are available to use while building robots is always fun. The kids learn when to use polycarb or pvc, or steel vs alum for high strength.

Team 971 has been building sheet metal robots and has been highly successful with their designs. Take a look at their website and check out their design photos.

The use of .090 5052 H32 alum and building all the parts from one thickness allows the robot drivetrain to be made in a few hours. The robot comes off a laser cutting machine in one big nest of parts.

Here is a video of the teams design and prototype phase:

I feel compelled to add that, while this is true, it’s also possible to achieve all of those things using other methods of construction.

I get that people are trying to emulate the work of teams that are better than they are, but there’s more than one way to skin a cat.

If your robots aren’t yet performing in the top, say, 10% of those at your events, sheet metal isn’t going to make a lick of difference.

Carry on.

And if they are performing at the top 10% you don’t want to revolutionize you want to iterate. Basically, if you are doing well with what you have iterate. If you aren’t then changing construction methods is not the best solution.

What I’m trying to say is play to your strengths. If you are good with laser cut wood use it. If your resources are such that welded tube is best for you than you should do that.

Excellent point. I’ve posted before that our entire machine shop is a chop saw and a cheap drill press (plus access to simple lathe work.) We’ve done okay over the last few years with AndyMark c-channel frames and standard gear boxes. I don’t even want to mention what kind of wheels we’ve been using…

IMHO it doesn’t help with the team if you stick to the same old construction methods year in and year out. Have the kids see what is available out in the real world. Try to bring something new to the team every year. There are a lot of sheet metal fabricators, machine shops, tube laser cutters, assembly houses, cable houses, injection molding, water jet cutters, etc that are more than willing to help out. A team just has to find a fab sponsor and ask for some help/supervision constructing their robot.

If you want to teach kids about engineering yes you do start with a drill press and chop saw but in the end you want them to know how to design and build a robot using a 5 axis tube cutting laser using the latest in CAD technology.

Obviously, sheet metal does open up a slew of options, especially in manipulators. Our team likes to do everything ourselves, partly contributing to our limited machining capabilities. We definitely won’t go full sheet metal this year, but for future years, does any team that have a brake suggest any models or companies of brakes. Preferably on the cheaper side though.

I wouldn’t trust anyone to design for a 5-axis anything if they can’t make something work with simple tools and simple ideas first.

Designing in sheet metal (or in composites or plastics or for five-axis mills) isn’t the silver bullet that will make a team’s robots work.

Just a difference of opinion, really, but I think building simple, successful robots is a better path than building pretty, heavy paperweights.