Is Welding Worth It?

[courtney.john28]

For the three years I've been on my team, we have always chosen to assemble with steel rivets that fit with stock versaframe gussets. There have always been problems with sheered rivets (especially during our 2014 season) and the problems seem to continue to an extent this season. I've started looking into welding to solve these issues but I was wondering what you guys think of this change. Is it worth the change? while I know there is time constraint since most teams outsource there welding, is it worth this delay? Would students be able to acquire the skills to be proficient at welding over an off season? How big is the difference in strength between a frame mainly assembled with rivets and one that was welded?

[cscottm]

Team 2502 always welds our robot chassis together, and this is the first year where we have done both rivets and welds, that way if a weld cracks we had a failsafe. Our practice bot is not welded and the rivets shear off all the time, and In my opinion welding is something that is worth the time, provided you are using tubing of some sort.

[Kevin Leonard]

Originally Posted by courtney.john28

For the three years I've been on my team, we have always chosen to assemble with steel rivets that fit with stock versaframe gussets. There have always been problems with sheered rivets (especially during our 2014 season) and the problems seem to continue to an extent this season. I've started looking into welding to solve these issues but I was wondering what you guys think of this change. Is it worth the change? while I know there is time constraint since most teams outsource there welding, is it worth this delay? Would students be able to acquire the skills to be proficient at welding over an off season? How big is the difference in strength between a frame mainly assembled with rivets and one that was welded?

Team 20 has welded robots for years, because one of our mentors (who has been around for 20+ years) is an excellent welder. Not only does it fasten our frames together and make them strong, but it's an incredible learning experience for students.

Now I'm working with 5254, who doesn't have that resource. We assemble things with Versaframe, bolts, and rivets.

Both teams have seen success recently, despite very different design methodologies and styles.

You don't need welding to be successful, or to build sturdy machines. Having your components built with geometry that works to strengthen your machine, having components be easily replaceable and maintainable, and having failsafes such that if one bolt breaks, your robot won't fall apart a result have kept 5254 machines (mostly) together the past three years.

[MaGiC_PiKaChU]

Our welded frame this year was basically impossible to break, and it looked great. Not a single weld cracked, even after 50+ matches of this game. It was definitely worth it

[FrankJ]

Welding aluminum generally isn't worth it for FRC application. Aluminum weld joints are weaker than the base metal. Very limited options for repair at competitions. Competition quality welding is not a skill you are going to acquire on the FCR level. (Not say somebody cannot acquire the skill, but it would take a lot more practice than you would get building a robot.) Most of the welded robots I have seen have had their welding farmed out. Nothing inherently wrong with that.

This isn't intended to be critical of teams that weld their chassis. If it works for you, great. As in all things engineering there are trade offs. That is where the fun comes in. Making all those choices.

[Katie_UPS]

Having been a student and mentoring welder: maybe?

In or out of house, there is a huge time sink. Its always been a slow process for me, intentionally. A lot of time is spent lining things up, clamping, and repeating that process after the welding starts (metal tends to warp when it gets hot, so you need to readjust and account for that). Student welders aren't as fast as experienced welders and are more prone to making mistakes (I've lost a few hours to my welds cracking while grinding them down). I've never dealt with out-of-house welding, so I can't speak to that but I can assume there is going to be some time lost.

The biggest pro to welding is also its biggest con: everything is (mostly) permanent. You can't pop the rivets and reorient your arm but also you don't have to worry about sheering. I can't speak to the strength of welding vs bolts, but welding does allow for more creative joints with less headache.

Students, with a mentor and enough practice, are more than capable of acquiring enough skill to weld FRC bots by kickoff. If you have the welding facilities already, there's no harm in experimenting with it in the off-season.

[OccamzRazor]

If you make a lot of design changes then welding is not the way to go. We specifically chose not to weld anything on our robot this year in case we fell from the tower. We did once during build season week 5 and the robot fell 5 feet to the floor (everything was ok!). If you break a weld at competition there is almost nothing you can do and because FIRST Stronghold was such a rough game we made that call early and went with rivets. We had a few shear during one impact on the field but as long as you use enough gussets and use the right diameter rivet for the application they will hold up just fine. They are super easy to replace and you can add more if something fails.

Now we do weld certain joints together on our robot if the assembly is modular and can be removed and replaced. It does make a superb joint if it is welded correctly. Welding joints can save a lot of weight and reduce fabrication time for some systems. If you have the capability then definitely use it. Try building a test frame and drive the wheels off of it.

[Chris is me]

If you guys insist on students doing all the building, you're going to have more headaches than fun welding aluminum for competition. Students can and do get good at welding aluminum, but it's somewhat easy to mess up and not get full depth on the welds and end up with a weaker assembly than what could have been done with rivets and gussets.

Generally if a riveted design breaks, it's a design issue, not that rivets are inherently weaker than welding. Care to post some pictures of your failures? We may be able to help you prevent those in the future.

[MrBasse]

Originally Posted by Katie_UPS

... (I've lost a few hours to my welds cracking while grinding them down)...

Why do you grind your welds down? Are you looking for a smooth appearance or for a strong joint? In my opinion, nothing looks better than a smooth stack of weld material laid down just right especially on aluminum.

[Michael 4499]

Currently I am a student welder and have been for the past 2 years. The biggest suggestion that I can provide is to make sure that you plan maticuously and something that I have learned this year is that making jigs or gussets while welding helps the process immensly. It keeps the final product at the correct angle and from my experience, makes it a lot easier to weld. Whatever your team chooses to do make sure that you practice it in order to evolve you process.

[InFlight]

On your riveted joints failing. It's very important to use the correct grip length and hole size for the rivets. If your riveted joints are failing constantly, it's likely some sort of installation error.

Welding Aluminum requires either a MIG or TIG welder. This requires some considerable practice, and mentor familiar enough with the equipment to teach others how to use it safety. It can only be used with some types of Aluminum, stick with 6061.

While not as strong as a weld, it is also possible to braze Aluminum with a plumbing torch. I'd only try this with 6061 aluminum and use Bernzomatic AL3, Alumaloy, or Durafix braze rods.

[Michael 4499]

Originally Posted by MrBasse

Why do you grind your welds down? Are you looking for a smooth appearance or for a strong joint? In my opinion, nothing looks better than a smooth stack of weld material laid down just right especially on aluminum.

Agreed, the only reason I would grind down a weld is if there needs to be clearance for a bolt or something.

[hutchMN]

Originally Posted by cscottm

Team 2502 always welds our robot chassis together, and this is the first year where we have done both rivets and welds, that way if a weld cracks we had a failsafe. Our practice bot is not welded and the rivets shear off all the time, and In my opinion welding is something that is worth the time, provided you are using tubing of some sort.

Maybe because your frame wasn't well designed... We started welding in 2014 so I wouldn't say we always weld our frames

[RoboChair]

Originally Posted by Chris is me

Generally if a riveted design breaks, it's a design issue, not that rivets are inherently weaker than welding. Care to post some pictures of your failures? We may be able to help you prevent those in the future.

This, very this. You are either using rivets in a manner that they are very poor for(tension is bad), not enough of them, and/or too small of rivets. We used well over a thousand rivets on each of our robots this year, 3/16" aluminum.

[IndySam]

Adding a good epoxy along with your rivets can help eliminate rivet shearing and make a frame as strong as welding. It's a great way to add additional strength to a riveted frame.