pic: How It's Made: 148 & 217 Robots

[Collin Fultz]

This video was really cool, but I'm looking forward to next week's episode on pick lists.

[Paul Copioli]

Like John said, it is all about the geometry. There are three thicknesses we use: .0625, 0.90, and .125. I try to start with .0625 and only go up in thickness as required. For the last few years, the major differences in the basic sheet metal construction between 148 & 217 have been:

1. 148 used .090 for the drive base and 217 used .0625
2. 148 primarily used 1/4" rivets and some 1/8" rivets and 217 used 5/32" rivets exclusively.
3. 148 used flat plates with standoffs for the gearboxes and 217 used bent metal and rivets.
4. 217 got most of it's lightening from using .0625 with basic holes and trusses and 148 did it with .090 and a specific focus on visually appealing large lightening patterns.

This year, we decided to try each other' styles and mix and match:

1. Both 148 & 217 are using .090 fir the drive base.
2. Both 217 and 148 are primarily using 5/32" rivets, but using 1/4" rivets for main structural attachments and in place where we may need a bolt due to rivet gun access. We found a very inexpensive pneumatic riveter that can do 1/4" rivets with no problem. Each team owns 1.
3. Both teams are using a bent sheet metal gearbox for the drive directly riveted to the drive base. In addition, our other gearboxes are a combination bent meta / standoffs.
4. Both teams are using the 148 style of lightening.

One major difference between the two designs is the choice of fasteners. 148 uses English (where possible) and 217 uses metric (where possible). This posed interesting design challenges to make interface holes to handle English or metric on the few parts that were the same. We standardized on #10-32 (M5) and 1/4"-20 (M6). That has worked out much better than I planned.

I will probably do a joint white paper with John, but it will have to wait until the VEX stuff settles down as John and I are both extremely busy due to VEX's increasing popularity globally.

[s_forbes]

Thank you John and Paul for the excellent info. I've been looking at the 148 models in solidworks (well, the tumbleweed model... I'm afraid if I open the 09 bot my computer will melt) to get a better idea of how you go about designing some of these parts. There are some parts in there that I wouldn't have even thought were bendable. Really awesome stuff!

[Andy L]

Originally Posted by s_forbes

Thank you John and Paul for the excellent info. I've been looking at the 148 models in solidworks (well, the tumbleweed model... I'm afraid if I open the 09 bot my computer will melt) to get a better idea of how you go about designing some of these parts. There are some parts in there that I wouldn't have even thought were bendable. Really awesome stuff!

I started with Tornado... bad choice

[Ricky Q.]

This video and the info that John and Paul provided are just part of the amazingness that comes with being a part of IFI and the FIRST teams they support. This is a company that truly "gets it" and knows that supporting FIRST and programs like it is key to ensuring the success of younger generations.

There are no words to describe how awesome it is to be on the same team as JVN, Paul, Brandon and the other unsung engineers and students that make the Robowranglers what they are. It provides inspiration, motivation and countless hours of entertainment.

-Ricky

[Akash Rastogi]

Thank you very much, John, Paul, and Sean.

[JVN]

Originally Posted by s_forbes

Thank you John and Paul for the excellent info. I've been looking at the 148 models in solidworks (well, the tumbleweed model... I'm afraid if I open the 09 bot my computer will melt) to get a better idea of how you go about designing some of these parts. There are some parts in there that I wouldn't have even thought were bendable. Really awesome stuff!

Pay careful attention to how the parts interact with other parts. Lots of times you can combine individually "wimpy" parts in a way that makes a "not-wimpy" structure.

Try to visualize how the assemblies will respond to applied forces, not just the individual parts.

-John

[mplanchard]

John,

Your movie was just beautiful!

I used sheet metal for laboratory robot design for 5 years. It is light weight and accurate. A few tips on the SolidWorks design side for teams:
-Work with your Sheet metal shop to know their K-factor. SolidWorks uses .5 by default - but this is never the case. Material and shop equipment produce different values. Build these values into the initial design.

-Where do you obtain the material required for the Bend? The answer comes from the Sheet metal Flange position option. The four options are: Material Inside, Material Outside, Bend Outside and Bend from Virtual Sharp.
Material Inside: The outside edge of the Flange coincides with the fixed edge of the sheet metal feature. Material Outside: The inside edge of the Flange coincides with the fixed edge of the sheet metal feature. Bend Outside: The Flange is offset by the bend radius. Bend from Virtual Sharp: The Flange maintains the dimension to the original edge and varies the bend material condition to automatically match with the flange's end condition. Save manufacturing cost and reduce setup time.

- A sheet metal manufacturer maintains a turret of standard relief tools for Rectangular and Obround relief. Obtain the dimensions of these tools to utilize in your design.

- Alternate between 3D formed and 2D flat for every additional sheet metal feature you create. The Flatten feature alternates a sheet metal part between the flat state and formed state.

-Use interference detection in your assembly. You can create configurations of you part to test for tolerance stack up. Make certain you can get tools in to fasten hardware.

-When looking at mating pattern of holes - make certain that you are refernencing dimensions from the same edge. There may need to be a left and right version of a part if the holes are off. Marie