Just interested, Rivets, Fasteners, Welding, Other

  • Rivets
  • Fasteners
  • Welding
  • Other

0 voters

I’m just interested on what teams prefer or just individuals favorite are. Not sure if this has already once been a poll but wanted to start a conversation. Our team has been welding our frame for a while.

The formatting for the poll is off

But I’d say welding. It’s probably the strongest bond. We used it on our elevator system this year

Hmm, Strange. I used the poll widget so I don’t know why it didn’t work

1 Like

We rivet our chassis together with just a few rivets and then weld every joint. You have to be careful because of warping though, we cut a jig the shape of our chassis and bolt it to the jig so it cant warp

I’d say 95% of the fasteners on our robot are rivets. The rest are bolts, for modularity and strength. I must add, all those days our school was closed due to snow and we had to rivet with our small portable rivet gun built a lot of character…

I prefer rivets and small standardized bolts over welding for anything that may need to get replaced, removed, or iterated.

5 Likes

I’m shocked that the option of “Only duct tape and zipties” is not available

7 Likes

Welding is my preference, but only if there is 0.0000% chance of needing to change something.

Fasteners are best for modular components.

Rivets are the quickest (with a pneumatic riveter).

The frame is welded. Every weld is done by a student. The frame is complete early for powder coating. It is all about the students learning. Go Gems!!!

Do you heat treat your parts after welding? The heat affected zone from a weld hurts the temper of the aluminum, and unless the weld is done properly it will result in a weak bond. I’ve never seen more broken welded joints than at FIRST competitions.

3 Likes

We typically weld sub systems and then bolt them together. We messed up in 2017 welding part of our gear, climber and drivetrain all together, making change impossible. The past couple years we may weld the drivetrain all together, but provide mounting locations to bolt on things like an elevator that is welded together.

We have broke welds before but rarely. We did break a weld from a bad design last season, along with just not getting enough hear into it to get an ideal weld for the load it was taking.

from my knowledge we do not. The parts that are welded on our bot do not get a lot of strain so we havent had to deal with a broken weld, but thats not to say we wont in the future.

The answer for us is…it all depends. Some things are best riveted together (thin materials, anything that doesn’t need too much shear strength or isn’t likely to need to be removed.) Some are better bolted (needs shear strength.) Some many be fastened with specialized hardware (the t-nut/bolt combos for t-track material, for instance.) Some are best welded (high strength parts and units that will never need to be taken apart.) We use all these methods on our robots at the same time, choosing the best for a particular application. This year’s robot had a bolted frame, welded drive-train components, t-nutted track material (the elevator), and riveted struts supporting the elevator, camera mast, electronics board, etc.

Our team uses rivets and fasteners exclusively. Welding might be appropriate for drivetrain frame but other than that I agree with above sentiments regarding weak welds and weakening the aluminum itself. Also it lends to warping and misalignment of pieces, often exactly where precision is needed.

Our frames have been welded since at least 2010 (my rookie year). We do not heat treat the welds and have very few problems. Most problems are not the welds but using too thin of wall tube for some items that were not thought to be high stress. Every thing on and about a robot is high stress!

Not to change topic but the warping and misalignment can be controlled to an extent.

We typically design parts to be easily aligned, using edges as reference points so we can clamp 2 parts to a parallel or 1-2-3 block, and as long as it’s tight, its in the correct spot. When welding 2 parts together that each hold a bearing to the same shaft, we either using bearings and a shaft for alignment, or even a piece of 1.125" steel round stock going through the bearing holes. The round stock worked very well since we needed a total of 6 bearings to line up going across the width of our robot, with a total of 4 separate welded pieces.

Warping is a little harder to deal with but the main idea is to minimize the amount of heat needed and try to spread the heat evenly. Pre-heating aluminum helps a ton, not requiring you to crank so much heat to get the weld started. On the drivetrain for example this year, once everything was clamped together, I would start with one corner and add a weld, then move to another and add a weld, and keep rotating, never running more than one bead at a time at a joint. Once everything is welded, we take the frame to a granite level table and check for flatness. We adjust the frame using 2x4s and C clamps from there (or hammers if it comes to it).

Welding definitely adds time, and takes skill, but allows you to assemble parts in more ways, and in spots where a gusset plate would be impossible to fit. Sorry for derailing a minute, just thought to put this out there for any teams that wanted any tips or strategies for welding.

4 Likes

Welding can definitely work and be accurate, but one thing I’ve noted after looking at almost all top bots in the world (worlds and IRI) is that they rarely use welds on their robots. I will concede that riveting and other fasteners require more time and more cut pieces.

Our decision tree for rivets vs. bolts is:

  1. Use 3/16" aluminum rivets for everything you can
  2. If rivets don’t have enough shear strength for the application (or you won’t be able to get a rivet gun in there), use #10-32 bolts
  3. If #10-32 bolts aren’t strong enough, use 1/4"-20 bolts
  4. If you need smaller bolts (for example, for tapped holes into the side of 1/4" plate) use #8-32 or #6-32

We don’t have welding capabilities.

This topic was automatically closed 365 days after the last reply. New replies are no longer allowed.