Need Help With Sheet Metal Designing

[MetalJacket]

Originally Posted by AllenGregoryIV

Feel free, I hope it helps.

Thanks!

[jspatz1]

JT, we've been doing sheet metal frames for 3 years now. Would be happy to send you those CAD models (Inventor) if you wanted them, along with info on assembly.

[Akash Rastogi]

JTN, I'm also available if you some sheet help.

[roystur44]

JTN,

The function of the part you are needing to attach is the driving force of the attachment method in the design. Let's list some methods to join sheet metal.

Permanent joins

• Spot welding
• Mig
• Tig
• Braze
• Epoxy

Semi permanent

• Pop rivet
• Solid rivet
• Tog-L-Loc
• High bond adhesive tape

Temporary/Removable Joins

• nut and screw
• Screw and tap/thread
• pem nuts
• Pem studs
• self tapping screws
• drilling screws
• Plastic connector
• 1/4 turn fasteners
• Riv-nut

Inter locking joins to position or fixture and increase strength, rigidity

• mixture of tab and notch and hardware
• dowel pins and holes
• interlocking puzzle piece joint
• Dual Lock

What do you think of our list? Did I miss anything?

[JTN]

Thanks for all the replies! Sorry I have not responded yet, I have a habit of forgetting to post... so I will reply to all the posts in one post.

Travis Schuh: Thanks for the tip, I was actually thinking about doing just that, but I'd have to see how I could get a CNC mill to mill those tight corners.

AllenGregoryIV: Yes! I have seen your robot, the sheet metal work looks fantastic! I really admired your robot last year. Thanks for all the great links, I will look into them when I don't have homework piled up... (tomorrow).

Sanddrag: Post taken into consideration, thanks for clarifying.

jspatz1: PM sent.

Akash Rastogi: I will send you an annoying amount of Facebook messages if the need arises, thanks for the offer.

Roystur44: I think we would most likely be using 3/16" rivets and screws. Your addition of dual lock at the end of the list intrigues me, I will look it up.

Thanks for all the great replies! I will work more on the CAD model tomorrow and post an improved corner!

[Chris is me]

It seems like your resources are multiple CNC mills + hand brakes to bend metal. Maybe it's just me, but it sounds like those are resources better suited to tube and plate based construction with bent sheet metal for specific parts rather than a full sheet metal robot. In a lot of cases you can make good, rigid, light structure in less time and about the same weight going that route. If you have a turret punch / laser cutter sponsor and precision bending equipment, sheet metal does get more attractive.

[JTN]

Improved joint: https://docs.google.com/file/d/0B9fw...it?usp=sharing

[AdamHeard]

Originally Posted by JTN

Improved joint: https://docs.google.com/file/d/0B9fw...it?usp=sharing

That bend will be hard (impossible maybe?) to get.

Rather, make the inside dimension of one rail match the outside dimension of the other rail.

Also, it looks like the two flanges on the left rail coming to a sharp corner with each other is a possible issue. Someone more knowledgeable in sheet working can clarify.

[tim-tim]

Originally Posted by AdamHeard

That bend will be hard (impossible maybe?) to get.

Let me start with I design sheet metal parts on a daily basis. While the top bend that would connect the two flanges is rather difficult, the guys in our shop would say its doable. The caveat to that is I work with extremely skilled artisans that do this for a living. That being said I would never ask them to make this.

That "S" bend in the part is what we would call a joggle. There are special tools and techniques that make this easier. Keeping tolerances can be difficult and may take time to get right.

A more simple solution would be to rivet/bolt a gusset plate across the top two surfaces.

Rather, make the inside dimension of one rail match the outside dimension of the other rail.

This will also work, and most likely be stronger than the above mentioned method. Just be sure to leave room for tangent lines when designing the length of the inside piece. I wouldn't design to the exact distances given by CAD. Give yourself some room.

If you decide to use this method or Adam's method, be sure to give yourself more than a single attachment point between the two pieces. I would use 3 points or so.

Also, it looks like the two flanges on the left rail coming to a sharp corner with each other is a possible issue. Someone more knowledgeable in sheet working can clarify.

Again, this is doable but not preferred. In order to do this you would need dies (or fingers) of the exact length of the flange. This could require cutting tooling. It is also a bad idea from a stress standpoint. A sharp corner (the tangent point of two bends) should be relieved. Most software packages have this as an option in the sheet metal tools. I would put about a 1/16" or so relief radius in this part. It generally also applies to bends that are in the middle of the parts (eg the flange doesn't run the full length of the part).

I would also recommend putting a radius or chamfer of decent size on each corner.

Hope this helps!