Need Help With Sheet Metal Designing

[JTN]

I've become really interested in sheet metal designs over the years of watching FRC competitions and looking at the robots compete. This year I finally decided to start working on a CAD model for a swerve-compatible robot frame that is lighter, takes up less space (or takes up different space so we have more room inside), and more aesthetically pleasing than our current (and past) frames made of Item (similar to 80/20). At the moment we have no engineers who know much about sheet metal, but we do have CNC mills (I know they take a while) and the proper equipment to bend large quantities of metal. What I need help with is how to actually design a frame and/or components and how to attach the parts together. So far all I have been able to come up with in terms of attaching parts is this: https://docs.google.com/file/d/0B9fw...it?usp=sharing
(Sorry for URL instead of direct image. Still have to figure that out.)

All help is appreciated. Thanks!

[James Tonthat]

I'd recommend taking a look at how 971 does their style of sheetmetal.

https://picasaweb.google.com/1177698...ingProgramming

https://picasaweb.google.com/117769834305511597729

They do a very unique hybrid of sheetmetal and tube design (which might be better suited if you do have access to a CNC mill and some bending)

[JTN]

Thanks for the reply. The pictures help a lot. Sorry for the late reply, I was coaching my FTC team after school.

[Travis Schuh]

Attachment methods vary based on what to parts you are trying to join. The trick is to use geometry to give you strength. Imagine you are making the parts out of paper (or even mock them up in paper), and go through the thought exercise of how they will hold up to different forces.

On the picture you have attached, I would at least overlap the two top flanges and add rivets there so that you have more than just the bend resistance of the metal keeping the parts at right angles to each other. Based on the strength needed, you might add more reinforcing features, but overlapping the flanges is a cheap and easy thing to do.

-Travis

[AllenGregoryIV]

JT, We just started using sheet metal last season. We have a laser cutter sponsor so it's easier for us than it will be with you and the mill (remember to fillet your corners to the size of your end mills).

Here is the presentation I put together for the team last season when we decided to start doing this. It's definitely not complete and I was learning at the same time so I don't make any promises that is all correct but it will get you started.

https://www.dropbox.com/s/63ke4hzitw...t%20Metal.pptx

I would also recommend looking at the CAD files and robots from teams that do sheet metal well, 33, 148, 228, 1114, etc.

My favorite is still 148's 2011 Robot Raptor. I have a whole presentation that I go over with the team that is just on this robot.

Here is an interesting read on doing different types of 2D manufacturing (sheet metal, CNC routing, etc) for building things . http://www.instructables.com/id/How-...y-Really-Fast/.

Also go back through and read the threads on other people's designs. Some really smart people, give really helpful advice. Here are a few of the recent threads. 1114 Inspired Chasssis, 488 Fall Project 1 and 2, Sheet Metal Drivetrain Prototype and there are many more like it.

[sanddrag]

Originally Posted by AllenGregoryIV

(remember to fillet your corners to the size of your end mills).

I'd recommend filleting the corners to larger than the size of the end mills, even if just by a little.

[MetalJacket]

Originally Posted by AllenGregoryIV

Here is the presentation I put together for the team last season when we decided to start doing this. It's definitely not complete and I was learning at the same time so I don't make any promises that is all correct but it will get you started.

https://www.dropbox.com/s/63ke4hzitw...t%20Metal.pptx

Do you mind if I use this presentation with some modifications to help with training our members? (I will give you guys credit at the end of the presentation)

[BBray_T1296]

Our team uses aluminum 1" box tubing for our frame, which we temporarily attach somehow (I dont remember?) before having our sponsor (one of their employee's who does nothing but weld aluminum all day) weld it all up nice. This year's frame was far too complex, but it came in at just 13lbs and is stupidly strong (could probably withstand 1,000s of lbs of force in any direction). It also is easy to work with, has nearly infinite practical durability and is very rugged. We subsidize this tubing with sheetmetal for more robot subsystems (shooter, drivetrain assemblies, ramp lowerers, innertube grabbers).

We typically use 1/8" alum (powder-coated of course) for heavy systems like drive train and climbing brackets, and 1/16"-.0404" for shooters and such. We used .0202" (basically IS paper) in 2011 on our gripper because if it got banged up, it was super easy to hand-bend back into shape.

Originally Posted by BBray_T1296

Our team uses aluminum 1" box tubing for our frame, which we temporarily attach somehow (I dont remember?) before having our sponsor (one of their employee's who does nothing but weld aluminum all day) weld it all up nice. This year's frame was far too complex, but it came in at just 13lbs and is stupidly strong (could probably withstand 1,000s of lbs of force in any direction). It also is easy to work with, has nearly infinite practical durability and is very rugged. We subsidize this tubing with sheetmetal for more robot subsystems (shooter, drivetrain assemblies, ramp lowerers, innertube grabbers).

We typically use 1/8" alum (powder-coated of course) for heavy systems like drive train and climbing brackets, and 1/16"-.0404" for shooters and such. We used .0202" (basically IS paper) in 2011 on our gripper because if it got banged up, it was super easy to hand-bend back into shape.

You should try working with 1/2"-3/4" 1/6" wall steel. It's strong, light, and easy to weld!

[topgun]

Originally Posted by Andrew Lawrence

You should try working with 1/2"-3/4" 1/6" wall steel. It's strong, light, and easy to weld!

Do you mean 1/2" square tubing (or 3/4" square tubing) 16 gauge steel? Or do you mean a different gauge steel?

- T

[BBray_T1296]

Originally Posted by topgun

Do you mean 1/2" square tubing (or 3/4" square tubing) 16 gauge steel? Or do you mean a different gauge steel?

I think he means 1/2"x3/4" rectangular tubing with (im guessing 1/16" not 1/6"?) 1/16" wall thickness

[JTN]

Aaaand the results:

[BBray_T1296]

Cool stuff! how much does all this weigh?

[JTN]

I'm not sure yet, but I'll keep you posted.

[AllenGregoryIV]

Originally Posted by MetalJacket

Do you mind if I use this presentation with some modifications to help with training our members? (I will give you guys credit at the end of the presentation)

Feel free, I hope it helps.