Castings in FRC

[Ian Curtis]

Has anyone ever used castings on a robot? I realize that there aren't a ton of opportunities where it really makes sense, but it seems like it would be a neat thing to do. I've lurked on Home Model Engine Machinist Forum for a while, and the people there do some insanely impressive castings in backyard foundries. I realize the average school is probably not okay with setting up a foundry in the machine shop, just wondering if someone had done it...

(Apologize in advance for the lost productivity that comes along with combing through HMEM. The finished projects are cool, but the build threads are better!)

[DampRobot]

I'm not sure if this was what you had in mind, but in 2006 one team cast (out of plastic) meccanum rollers. I forget what team it was, but they were featured in the 2006 "Behind the Design" book. With the rise of 3D printing, even printing metal through sintering, I doubt many teams will use casting in the future.

On the other hand, FRC is a wide world with obscure teams that come up with some pretty crazy stuff. I wouldn't be surprised to see examples (especially in early years) of teams using extensive metal casting.

[Kristian Calhoun]

Originally Posted by DampRobot

I'm not sure if this was what you had in mind, but in 2006 one team cast (out of plastic) meccanum rollers. I forget what team it was, but they were featured in the 2006 "Behind the Design" book.

That would be Team 357.

[Ian Curtis]

Originally Posted by Kristian Calhoun

That would be Team 357.

I just remembered 125 cast resin wheels in 2010 as well. If other teams have done plastic casting I'd love to see that too. Probably more likely to happen than metal casting for a variety of reasons.

[dtengineering]

We cast and machined some aluminum hubs for our wheels one year, if I recall correctly... or maybe it was the ends for an intake roller.

We didn't make a big deal of it.... we had the facilities and it was the quickest/easiest way to get the part we needed.

Mind you, that was "back in the day" before Andy Mark had a solution for everything.

Jason

Edit: Oooh! Does that qualify us for "obscure team" status, or just "crazy stuff" status?

[Tristan Lall]

I've long wanted to try graphite permanent moulds for casting something out of aluminum...but never found an application where it really made sense, and therefore never asked any suppliers for assistance with it.

The trouble is, there's always a riser to deal with in that method, so you either need to be able to tolerate one grossly unfinished face, or have to set it up in a mill/lathe to clean the part up. At that point, especially if your machine is CNC, it would have been simpler to let the machine cut the part from a billet.

Casting gets more and more attractive as you scale the process up. A few years ago, someone wanted to make a whole pile of tank treads, and I suggested that they might try casting the links.

Another thing casting is good at is thin sections that aren't stiff enough to withstand rapid machining. That also goes for things that have undercut sections, because you can use cores to support the part.

[R.C.]

FRC 118 did some plastic casting this year.

I got a souvenir wheel! Maybe someone from 118 could chime in and talk about their wheels. They were really cool.

-RC

[Jeff Pahl]

There was a team in MN in 2008 that had several cast gearbox frames on their manipulator. I can't remember the team number. They ended up removing the entire manipulator assembly due to being very significantly overweight, but that was due to overall system design, not just the cast gearboxes. If my memory serves me correctly, each gearbox was a CIM driving a worm gear assembly, and the cast parts were about 1/2" thick.

I know of several teams here in MN that still have machine shops with casting facilities in their schools.

[Brandon Holley]

This year we cast the urethane "tread" for our shooter wheel. We had a ton of issues finding a material we really liked for our 2006 and 2009 shooter wheels. In 2009 we ended up using BaneBots wheels, and because we liked the grip they provided, we wanted to duplicate their material, but with our own wheel setup.

We went for a wheel with high rotational inertia, so we built a central hub/drum using a thick-walled aluminum tube. We 3D printed a mold, that held the drive shaft of the hub, and left a gap for the urethane to fill in and provide the shape we wanted. We ended up going with a concaved wheel to help ensure the ball was centered as it came through our shooter. Due to this shape, we had to build the mold in 3 pieces so we could get it apart.

One cool aspect of 3D printing the mold was we could add patterns to the urethane by adding them to the 3D printed mold. We decided to add some flare to ours with our team number:


The material worked out great. It had a great amount of grip to the ball, and was extremely robust. We never needed to change or even clean the tread material after an entire seasons worth of matches. I imagine if we ever build a shooter wheel again, or even some kind of intake roller, we may go back to this solution.

-Brando

[ahecht]

Originally Posted by DampRobot

I'm not sure if this was what you had in mind, but in 2006 one team cast (out of plastic) meccanum rollers. I forget what team it was, but they were featured in the 2006 "Behind the Design" book. With the rise of 3D printing, even printing metal through sintering, I doubt many teams will use casting in the future.

In 2005, Team 190 cast custom urethane rollers for their mecanum wheels. Team 357 did one better in 2006 by not only casting the urethane rollers, but casting the aluminum hub as well. Their hubs were cast using a 3D-printed mold, if I remember correctly.

[George]

Hi All
Last year we needed 2” x 7” dia. aluminum material for wheels
We had lots of scrap from robots over the years and I have an electric kiln,
I had not done any casting with aluminum for years, (like others I learned foundry at high school) with no green sand we used plaster for a mold (after it was baked to remove the moisture) it worked well enough to get us the billet material at a reasonable cost.
It was a great experience in Up-Cycling and I have hopes that we can explore more options this year,
To that goal I have invested in a set of foundry tools and built a molding bench.
I should say “made” a set of tools and a bench as most of the tooling was outrageously priced for as simple as it is.
I went with petro-bond sand instead of mixing my own “home brew” a little more expensive but better results too.
Altogether total cost was about $400.00 including the kiln + time and brain power
I have found many books on the subject on amazon
If there is an interest I will list materials resources and supplies as I did with 15c machine shop.
Have Fun
Geo.

[Tristan Lall]

Originally Posted by George

Hi All
Last year we needed 2” x 7” dia. aluminum material for wheels
We had lots of scrap from robots over the years and I have an electric kiln,
I had not done any casting with aluminum for years, (like others I learned foundry at high school) with no green sand we used plaster for a mold (after it was baked to remove the moisture) it worked well enough to get us the billet material at a reasonable cost.
It was a great experience in Up-Cycling and I have hopes that we can explore more options this year,
To that goal I have invested in a set of foundry tools and built a molding bench.
I should say “made” a set of tools and a bench as most of the tooling was outrageously priced for as simple as it is.
I went with petro-bond sand instead of mixing my own “home brew” a little more expensive but better results too.
Altogether total cost was about $400.00 including the kiln + time and brain power
I have found many books on the subject on amazon
If there is an interest I will list materials resources and supplies as I did with 15c machine shop.
Have Fun
Geo.

Did you need to adjust the alloy for better casting properties? (I assume you started with mostly wrought Al-Mg-Si alloys like 6061.)

Did you attempt any heat treatment afterward? (If so, what was the process, and how did it go?)

[tsaksa]

Originally Posted by Tristan Lall

Did you need to adjust the alloy for better casting properties? (I assume you started with mostly wrought Al-Mg-Si alloys like 6061.)

Did you attempt any heat treatment afterward? (If so, what was the process, and how did it go?)

If you plan to do some casting, it is best to get your raw metal from scrap castings. That way you know the specific alloy was appropriate for casting in the first place, and not stamping, extruding, machining, etc. There is a lot of scrap metal out there, so if you hook up with the right source it is usually easy to get enough of the correct raw material at modest or even zero cost for casting projects. The real issue with casting is having a safe location and the right tools and experience to do the work in a safe manner.

[JohnSchneider]

Ive seen teams use casting of metals - but have any of these teams tried using this process to create stronger metals.

For instance: say you were making a wheel shaft out of steel. You could add just a trace ammount of beryllium to the steel and close to double your strength. Without adding any weight.

It's sort of a bad example but I'm curious if any teams with a material sciences mentor has experimented with alloying their own metals.

[George]

Originally Posted by Tristan Lall

Did you need to adjust the alloy for better casting properties? (I assume you started with mostly wrought Al-Mg-Si alloys like 6061.)

Did you attempt any heat treatment afterward? (If so, what was the process, and how did it go?)

As our final product was to be wheels other than flux and de-gassing we did not adjust the alloy, nor attempt artificial aging or annealing, this was a spur of the moment measure, the cast billet worked fine and machined well, with no flaws and no failures.
We did not send any of our cast samples out for analyses, so I can’t comment on the alloy content, other than you are correct as most of the material we used was 6061 with a good helping of 6063
If we decide to cast gears, high strength components or wear parts it would be a different story, in this case a bit of zinc would go well,

fyi Blast from the past; http://www.youtube.com/watch?v=fJyD8...eature=related

Have Fun
Geo.