Laser Cutter And FRC

[DampRobot]

Originally Posted by roystur44

Damp,

If you wanted to make a nice compact 3 CIM ABS/Delrin gearbox housing with a PTO port. Think about repackaging the VexPro Ball shifter design.

I would be willing to lend you a hand and get you some Engineering and CNC machining time. I wanted to make a video for our team to show how a Solidworks design is imported to Gibbs Cam and how the geometry is used to create the tool paths and G code and how the part would be made on the CNC mill.

Roy,

Thanks for the offer. We might take you up on that. I was already considering doing a 6 CIM gearbox like that, with the VP shift shaft and delrin plates.

Thanks to everyone else for the ideas and comments. (Now I won't kill myself with toxic fumes.) While TechShop does have other much more appropriate machines for cutting gearbox plates, they currently aren't available to me. As a minor, I can't use most CNC tools, except for the laser cutter, and I was hoping not to have to have a mentor present to work on our summer project. Even if the machine doesn't work out for gearboxes, we can still use it for electronics boards, sprockets, pulleys, etc , as others have suggested.

[fb39ca4]

Originally Posted by dtengineering

Laser? Talk to FRC 1899 Saints Robotics. They know laser.

Jason

Yup. This year we made our entire chassis from laser cut plywood, and the year before, we made belt sprockets with the laser.

[craigboez]

It sounds like Delrin and ABS are the two goto materials. Is there a reason to pick one over the other? Are there specific advantages for certain applications?

[Nate Laverdure]

Originally Posted by craigboez

It sounds like Delrin and ABS are the two goto materials. Is there a reason to pick one over the other? Are there specific advantages for certain applications?

Absolutely! They're on opposite sides of the pyramid (pdf link).

[DonRotolo]

One great use for a laser like an Epilog is to make templates. You use the laser to cut a small X where the center of a hole is to be located in paper, tape the paper to your metal, and center punch almost perfectly. Also great for cutting templates, just follow the dark line...

[roystur44]

Originally Posted by DampRobot

Roy,

Thanks for the offer. We might take you up on that. I was already considering doing a 6 CIM gearbox like that, with the VP shift shaft and delrin plates.

I've seen a transmission plate made from Delrrin. It was light weight but it wasn't as stiff as a aluminum one. I think making a two piece enclosed housing similar to the molded VexPro one would be better and stronger.

[Mk.32]

I have a similar facility that I am allowed to run around in.
http://www.makerplace.com/

They have laser cutters up to 150watt with 5x5 feet bed sizes as well as all the other CNC mill/router goodies. Personally I use very little laser cutting on the robot, and stick mostly to the CNC router to do my plastics (a good chuck of which is polycarb which is NOT laser-able in these shops). And the mills/lathes to do the metal stuff.

My experiences with laser-ing Delrin has been pretty good, running the 80 watt laser at about 70 % power and a medium cut speed I can get a clean out on 1/4 plate no problem.

In the end it's all about making what tools you/your team has work for you. I know 2102 this year had a robot that was mostly laser cut on top of an alum box frame, including wood plate gearboxes and plastic pulleys that worked out pretty good for them. You can make a FRC robot that is competitive with laser-ed cut parts.

Also 254 used to do Delrin gearbox plates, however they later switched to pocketed out Alum because it was lighter and stiffer.

[Madison]

I don't have the specific make and model available, but we have a laser cutter in our shop (and are getting a 2nd). We make significant parts of our robot from laser cut plastics -- mostly delrin and ABS, though we'll cut polycarbonate as well since our laser cutter is vented.

Take a look through the galleries here if you want to get an idea for how we do things. Our 2013 robot was made almost entirely from sheets of ABS.

[Cory]

Originally Posted by Mk.32

Also 254 used to do Delrin gearbox plates, however they later switched to pocketed out Alum because it was lighter and stiffer.

It's not actually lighter, but it is basically identical.

The Delrin was a pretty big PITA. It was more difficult to hold tolerances on the bearing bores, the bearings could come unpressed more easily, and it flexed a bit. If you wanted to thread one plate to avoid the use of nuts when screwing the gearbox together, you had to use PEM nuts, which students can easily strip if not being careful. We much prefer aluminum.

[Mk.32]

Originally Posted by Cory

It's not actually lighter, but it is basically identical.

The Delrin was a pretty big PITA. It was more difficult to hold tolerances on the bearing bores, the bearings could come unpressed more easily, and it flexed a bit. If you wanted to thread one plate to avoid the use of nuts when screwing the gearbox together, you had to use PEM nuts, which students can easily strip if not being careful. We much prefer aluminum.

I have tapped delrin for light duty threads, where they not sufficient to hold the gearbox together?

[Cory]

It's not a very robust solution if you're using it to cantilever the gearbox off your frame rail. Especially since you need to be super careful about how much you torque it. We used PEM nuts when we did Delrin side plates.

You also can't effectively prevent loosening due to vibration since you can't use loctite and nylon patch screws don't mix with threads in Delrin.

[roystur44]

Originally Posted by Cory

It's not a very robust solution if you're using it to cantilever the gearbox off your frame rail. Especially since you need to be super careful about how much you torque it. We used PEM nuts when we did Delrin side plates.

You also can't effectively prevent loosening due to vibration since you can't use loctite and nylon patch screws don't mix with threads in Delrin.

Maybe try Helicoils, Keenserts or EZ-lock hardware, or Pem SI hardware for plastics.

When attaching the parts the trick is to load the force on to the thread of the hardware an and not on the plastic.

There are lots of ways to attach metal hardware to plastics, ultrasonic welding, molded in, press in, etc.

[Cash4587]

I used the Laser cutter today on this, If this helps? lol I find it very useful, Especially since it is a school owned cutter not bought by our team
http://www.chiefdelphi.com/forums/sh...68#post1278668

[MichaelBick]

Originally Posted by Cory

It's not a very robust solution if you're using it to cantilever the gearbox off your frame rail. Especially since you need to be super careful about how much you torque it. We used PEM nuts when we did Delrin side plates.

You also can't effectively prevent loosening due to vibration since you can't use loctite and nylon patch screws don't mix with threads in Delrin.

Was there any problem with plastic melting? For some reason I remember hearing that when CIMs heated up they melted the plastic and that also was one of the reasons you switched back.

[Cory]

Originally Posted by MICHAELABICK

Was there any problem with plastic melting? For some reason I remember hearing that when CIMs heated up they melted the plastic and that also was one of the reasons you switched back.

We were using green loctite to retain some pinions on the CIM shafts where we didn't have length for a retaining washer. We partially melted a small portion of the delrin when we had to apply heat for much longer than normal to break the loctite free to get the pinion off.

We never saw issues due to motor heat though.