Who else prototypes with non-metal materials?

[kingc95]

Today they made dummy 2x1 bar stock out of lumber and put together a prototype chassis so programming team can drive while build is working on the upper half.

We are big fans of prototyping. And we have used a variety of materials over the years but I think my favorite is expanded PVC sheets. It carves like butter, is fairly dimensional and you can get it cut down at Home Depot from a 4x8 sheet into 4 48x24 pieces to fit on an Omio or 3 48x32 pieces for a 30x30 drive base on an XCarve or similar.

I recently found out the same is not true for Acrylic and Polycarbonate. They won’t cut it down anymore so my terrain is no longer the viable pickup machine.

Another example of the PVC for 2020 before we had to stop…

Also 3d printing in sections and applying a resin filler (last year)

Anyone else have other materials they like to use?

[Peter_Johnson]

Plywood cut with a laser. Incredibly fast and easy to work with.

[Skyehawk]

For mechanisms in the early weeks? Cardboard, hot glue and those brass push pin rivets for pivot points.

Next step: wood slats, hot glue and fasteners, maybe 3d printing. Thin plywood or 1/32 polycarbonate if needed.

Beat up double sided intake cardboard mockup from 2022:

Some more 2022 stuff:

[kingc95]

What thickness?

[Cforbes]

Why limit yourself to prototypes? We’ve built regional winning robots out of laser cut 1/4" plywood…

[kswaid]

We use a lot of PVC foam sheet and 3D printed parts as well. Throw in a little PVC or pex pipe, maybe some wooden dowels, and you can make some fast but useful prototypes.

Another fun thing to do with extra PVC sheet is to spray paint one face and then relief carve some art with the router table and an 1/8" endmill. It gives a great surface texture, high contrast, and sharp corners. Example:

[Ankur-Raghavan]

This isn’t the cheapest option, but we use Lexan (polycarb) to test anything that will be cut from aluminum, especially the 1/4 inch thick ones. Lexan can be easily cnc’d and we can usually push it to 200% on the toolpaths in carbide motion. Once we know it works we will take the time to cut from 1/4 aluminum.

On the robot we use mostly 1/4 lexan so any bearings that are pressed into it don’t protrude from the other side. It also is much less flexible than the 1/8 sheets.

[kingc95]

Sponsor plaques!!!

[four]

Some people do not want to be seen with a wooden robot.

That is not a good reason, but I am quite sure that was our reason in 2022.

[kingc95]

I draw the line at wooden structure. Anything like wooden gears, belts, wheels, pulleys seems like a fools errands for a final product. Maybe as a prototype for a turret rack with large teeth or for a large turntable plate

[Cforbes]

all i’m gonna say, done the ‘open alliance’ thing since bf that existed…

[DaltonAvecVitesse]

We tend to use acrylic or polycarb between .125"-.5" thick when testing out our designs. We found out that our laser can handle cutting acrylic really well once we fine-tune the settings (we never laser polycarb due to the toxicity of the fumes). This is the CAD of our shooter prototype from week 1, sorry I don’t have any photos of the physical prototype.

I couldn’t find any photos of our 2nd shooter prototype either, but once we switched to top / bottom rollers instead of side / side we used laser-cut plywood (.125" thickness) to test out our ideas and different vertical compressions of the NOTE before milling out the UHMW for our final design.

[GeeTwo]

Does this count? 2014 Aerial Assist Prototype/practice 'bot on the left, nearly finished competition 'bot on the right.

We tweaked and tuned the dimensions in lumber, and got in way more drive practice with it than the two years before combined while be re-built in metal. . Lester, the mentor in blue jeans at far right, named the prototype Woody.
It was only natural that the aluminum and steel version was named Buzz, especially given that the team’s founder @ExploitSage watched the original Toy Story so so so many times as a toddler. (I’m @ExploitSage’s father). That steel hammer with the spray on bedliner surface to kick the ball never worked as well as the one made of 2x4s.

After that, few prototypes were metal, and when they were, it was scrap or re-used from failed parts. Two more fun non metal prototype stories:

2016 STRONGHOLD Wooden Wedge

No pics, but for 2016 STRONGHOLD, I ripped some 4x4s at a 45 degree angle to make a “duck boat wedge” for one end of our robot to help us over the defenses. [IIRC, we later decided that was the front and the boulder end was the rear.] We planned this wooden wedge to be on the competition robot, much to the head coach’s chagrin, but we had no way to fabricate this in metal at a reasonable weight. It turned out that the folks at AndyMark had the same idea and better fabrication, so we were among the first to order when AM came out with the AM14U Family Wedge Plate (am-3356).

2017 STEAMworks Corrugated Plastic intake

For 2017 STEAMworks, the prototype intake slide was made from a surplus corrugated plastic sign or two about mosquito control. We built in polycarbonate. It didn’t work as well (more friction), so we went back to corrugated plastic, but we did actually buy some white plastic for this. Independent of material*, we also mounted the extension from the frame perimeter to the “bumper perimeter” on spring loaded hinges that popped into place when the robot was enabled thanks to a default method on the climber. No joke; the climber and that extension were attached by a magnet and steel plate in STARTING CONFIGURATION, but were separated when the climber’s default method forced them apart.
pic: Wolfgang - 3946's STEAMworks robot

* I just remembered that the corrugated plastic was not strong enough for hinge mountings. We ended up riveting the hinges to polycarbonate, and gluing those to the corrugated plastic.

[BSV]

@Peter_Johnson

Plywood cut with a laser. Incredibly fast and easy to work with.

I can definitely second this. We just got the laser before the season started and it is a huge difference-maker in prototyping.

@kingc95

What thickness?

We’ve been using 3mm baltic birch for shooter testing and it’s great. Probably would go with something thicker than that (6mm) for anything that required it to be really sturdy during testing.

[ZCam_4415]

we use 0.25” plywood on our laser. combo of brackets and glue and such holding prototypes together and if they break, “eh, it’s prototyping” but yeah, second the plywood recommendation cause it’s just so fast to throw an idea together if your CAD is quick

[Ashray.g]

@kingc95

Anyone else have other materials they like to use?

Polycarb or delrin

[EricH]

Think we’ve still got plywood prototypes around for this year. We’re working on metallizing them.

[sanddrag]

What kind of speeds are you all cutting plywood at on your lasers, and what power lasers?

[jlr]

host space has an Aeon Mira 9 90W laser that I wish we abused earlier in the season to check parts. on that setting, 100% @ 40mm/s cuts through 1/8" baltic birch really quickly, our entire bot would take approximately maybe 10 minutes or so to cut out of minus the belly pan.

[kingc95]

@jlr

Aeon Mira 9 90W laser

Looks like ~$8,000, definetly out of our range for now, but goals… definitely goals.