Guys fabworks. No question!!!
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Although I’ve never been on a team that uses Fabworks, it can be quite a useful resource for many teams. Essentially, from what I’ve seen, Fabworks is GOATed, lol.
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You’re getting a 30"x30" sheet of 0.125" 6061-T6 for $100? Are you sure that’s not 0.063 thickness? If you are getting 0.125" that cheap, you really need to find out who this supplier is and share with the rest of us, because that’s a good $50 cheaper than anything I’ve seen from places like Metals Supermarket. I’m not even sure how they could do that and not be losing money on the deal.
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We ran 60lb of steel for our bellly pan and if you didn’t have a solid belly pan and collided with us mid field you most likely ended up with a bent frame. A good belly pan provides some structural support.
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As I posted above, it’s only 11lbs of material. Literally any local metals supplier can do $4-7/lb on aluminum sheet. If you go to Coast Aluminum in CA, where many local shops and teams get their metals from, it can be as low as $4/lb. And that’s not even counting rems, which I get for even less at Industrial Metal Supply in Campbell.
Now, if you want a steel bellypan, I think Fabworks is an excellent choice to avoid machining all that steel, at a great price.
Shop around, folks.
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We made belly pans for 15 years before we ever got a CNC. Some from wood, some from polycarb, some from aluminum. Yes, making them with the CNC does let us add additional/better features than we had previously, but they were all perfectly functional and did exactly what we needed them to do in the end.
So no, we would probably not buy a CNC’d belly pan, especially if it meant limiting our design choices (materials or dimensions), and doubly so if it didn’t provide mounting points exactly where we want them - sites like fabworks or sendcutsend already fill that particular need for customization.
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We started using polycarb belly pans in 2020 and frankly, it has been great. We previously used metal (Aluminum) belly pans that were waterjet cut and we could add a nice pocketing pattern to reduce weight. Because polycarb is lighter than aluminum, you can get similar weight without any fancy pocketing. So you don’t need a CNC to get the overall shape
In addition to mounting your electronics, the belly pan is typically the main shear web to keep your frame square. Polycarb has plenty of capability to carry those shear loads (especially without the pocketing), so strength is not an issue, We’ve been mounting bellypan on the top of the frame rails and then mounting the electronics underneath. We typically have some sort of structural members for the superstructure above the belly pan that you can attach the bellypan to to prevent sagging. But even without that, the sagging is not that significant. We typically match drill the holes at the point where we are mounting the pan to the frame/structure such that you really don’t need to pre-drill these holes on a CNC.
If you use the templates that are available for the electronic components you can drill the mounting holes by hand pretty accurately. So, you don’t need a CNC their either.
A plain, clear belly pan may not be as nice looking to some people as a fancy pocketed metal pan that is fully painted, etc. But if you mount some LEDs under there, you can get some great lighting through the clear belly pan that you can’t get with metal. Just make sure your wiring is clean because you can’t hide it…
The only real advantage of buying a belly pan would be if it could be considered COTS and we would be able to re-use it from year to year. Better yet, if there was a COTS frame kit that included side rails in a standard configuration (say 30 x 30 and maybe a few other standard configurations), included a battery holder and a belly pan then it might be worth buying a kit like that to be able to assemble the frame quickly after kickoff to have a drivebase ready to drive by day 2 or 3 and be able to re-use it from year to year. This would obviously constrain your design options for the overall configuration of the robot. But most years, a square 30x30 robot would not be a huge constraint. And it if was, you could design a custom drive base for that season’s game.
5010 is making a little cube runner in the off-season here. Fabworks steel belly pan looks very promising 
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We’ve been using 0.080" aluminum for our bellypan. Structurally, it only needs to do two things: (1) prevent racking, and (2) hold stuff off the ground.
I guess this is what amazon has done to me, going outside to interact with people? 
I also couldn’t find anything under like $140, and I’m not sure if that was with or without shipping.
Highly recommend Industrial Metal Supply for anyone in the south Bay, although they’re located in San Jose, not Campbell 
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Even though we have access to a CNC and a water jet we just used some plywood for our swerve testbed. We had some 16" lengths of 2x1 so adding the swerve drives made the robot 25"x25". Our belly pan is little more than a 24"x24" piece bought from Lowe’s, turned 45 degrees and using a hand saw to cut off the corners (as installed the cuts run along the outside of the frame).
I originally thought of this as just a quick+dirty for summer prototyping, but with a coat of paint it could be competition robot viable.
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Did you have any issues with the structure while driving?
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