Is Welding Worth It?
 

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?

Re: Is Welding Worth It?
 

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.

Re: Is Welding Worth It?
 

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.

Re: Is Welding Worth It?
 

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

Re: Is Welding Worth It?
 

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.

Re: Is Welding Worth It?
 

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.

Re: Is Welding Worth It?
 

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.

Re: Is Welding Worth It?
 

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.

Re: Is Welding Worth It?
 

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.

Re: Is Welding Worth It?
 

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.

Re: Is Welding Worth It?
 

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.

Re: Is Welding Worth It?
 

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

Re: Is Welding Worth It?
 

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

Re: Is Welding Worth It?
 

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.

Re: Is Welding Worth It?
 

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.

Re: Is Welding Worth It?
 

We outsourced the welding of our shooter together to a sponsor for the first time ever because rivets couldn't handle the stress of the ball being shot over and over again, leading to a weaker shooter. We riveted the gussets/metal together, then took it to our sponsor and they welded it for us, and we didn't have any problems. It was definitely worth it. If none of your team has had welding experience and is very confident, i would recommend taking it to get it welded.

Re: Is Welding Worth It?
 

Our team had been told to watch out for aluminum welding for it may give extra strength, but experience is needed and bolts and nuts can hold the frame together just as good. The only downside of that is be prepared to loose some bolts and nuts, but the pros are that you can detach parts in case repairs are needed.

Re: Is Welding Worth It?
 

Not to mention that when you get to <0.100" material, the skill level required to weld aluminum goes way up. Nothing like burning a hole is the last weld, killing the entire piece to ruin your day. :]

If you have the resources, welding is great fun. If I had the resources in place (A good welder for aluminum is $1000+) it is a good resource. If you don't there areas that would get more bang for your buck. YMMV

Re: Is Welding Worth It?
 

The first question that comes to my mind is what kind of rivets are you using? There are different grades and quality rivets. If you are buying them at your local hardware store in retail friendly packages chances are they are low strength. McMaster is one place that does sell high quality, high strength rivets also check for a local fastener supplier, Hi-Strength Bolt has locations in many areas.

I prefer rivets and/or nuts and bolts for the reason of quicker and easier repairs and changes.

Next time you are in traffic sitting next to a large truck take a look at the frame rail. You'll see that the cross-members and brackets are held on by rivets or nuts and bolts. That is so that those pieces can be replaced in the field in an expedient manner and without worry as to maintaining proper alignment or the skill of the welder and subsequent quality.

Re: Is Welding Worth It?
 

Every team is different, but my team has avoided having any welding on our robot at all. The reason being that should a weld break, we are (pretty much) guaranteed to not be able to fix it in the pit. We also have a sponsor that provides us with bolts for each year, as well as another sponsor that helps us with fabricated parts (usually laser cut and bent if needed), making a sheet metal chassis held together with gussets and bolts what we have found is the best option for us given our resources. We have also done drivetrains in the past made primarily from 1x2 aluminum, also held together with gussets and bolts.

Re: Is Welding Worth It?
 

95 welds were it seems to make sense, usually to reduce weight or to simplify a structure. It's not our first pick, but sometimes it solves a lot of problems. But we have a really good welder, and work in a welding training shop. Without those resources I don't think we could justify the time and risk of having welding done by a 3rd party.

We rarely use rivets, though. The basic frame elements are generally put together with screws and captive threaded inserts like rivnuts and pemnuts. We really like the easy serviceability screws give us at competition and during testing. There's also a comfort factor in the relative strength of machine screws.

Installing the inserts has a significant upfront investment in tools materials and time, and probably a measurable cumulative weight penalty. But I think it pays off over the course of a season.

Re: Is Welding Worth It?
 

I don't really remember (that was over 5 years ago) but my guess is that it was either an aesthetic choice made by someone else or a "we need this surface to be flat" type of situation. Either way, I guess I was glad we did, as it caught the bad welds before they were a major problem.

Re: Is Welding Worth It?
 

1836 hasn't welded for the past 4 years, and has been pretty happy. However, rivets, including those in highly stressed shear applications, can loosen up, creating a less than ideal joint (for comparison, we do use aluminum body aluminum mandrel rivets). It in the high load applications that we are considering welding joints as an addition to rivets and gussets.

Re: Is Welding Worth It?
 

As mentioned aluminum welds are typically not as strong as the aluminum itself. Welds can add material so they can add weight. Welds can embrittle material. Welds can cause oxidation. Welds can be deceptive.

Rivets and bolts add material and may be even more prone to do so. Rivets and bolt holes can weaken the material. Dissimilar materials can cause corrosion at the contact points.

All of those things aside - the design may specifically make one choice better than another. I can certainly see with the pits FRC uses that welding can be inconvenient if it fails. Then again maybe if it fails you just bolt or rivet at that point.

I don't think we have the welding equipment at Mount Olive High School anymore.
So if I want to cook some metal I have to do it at home, take it to a friend or take a trip to NextFAB.

Re: Is Welding Worth It?
 

If you have photos of where your rivets failed, please post them. That will make this discussion 1000% more beneficial to your team and other teams.

Your rivets failed most likely due to a poor design - either you're using rivets that are too small (we use 5/32", sometimes 3/16"), not using enough rivets, need a better gusset design, too high of stress to the affected area, etc.

We've used versa-construction with rivets and gussets for 3 years now and have been very pleased. It's simple, our students can build almost anything with it, and we've had no failures that weren't our own fault due to a poor design.

Buy a pneumatic rivet gun and a compressor if you can manage it - it will make your assembly go so much faster and we've found that they hold just as well if not better than ones done by a hand riveting tool.

Re: Is Welding Worth It?
 

Depends.

We use a MIG welder we received through a grant, we purchased a spool gun for it, and we teach a few of our kids to use it.

We normally use 1/4" aluminum plate for our drive train and weld the cross members into place. This year we also welded our shooter chassis (1/8" aluminum) together.

47 matches this year, not one broken weld.

Re: Is Welding Worth It?
 

Make good design decisions!!

Weld where it makes sense. Gusset and rivet where it makes sense. Bolt where it makes sense. Use wood and epoxy where it makes sense.

Re: Is Welding Worth It?
 

Being on a team that does not have welding, there have been many situations where I would want welding this year. 971's tube across their intake this year is a prime example of something that is difficult to do without welding. Of course there are ways to have the design not use that structure that necessitates welds, but the two-plate design for their intake is nice.
That being said I'm usually not impressed by student-made welds. I can't comment on how well actual welding holds up (only used it once in 2015), so don't ask me for execution stuff. Purely from a design standpoint, a lot of gimmicks are way easier to pull off with welds.

Re: Is Welding Worth It?
 

$1000 is getting away cheap. And with GTAW (TIG) welders, a $1000 welder buys you very little in the way of an good amp control such as a pedal or thumb trigger. If you TIG weld without the amp control, it becomes even more an art to get little in avoiding edges turning down - it requires more table time that many teams cannot afford to offer in a short build season.

We recently purchased a Thermal Arc 161 after borrowing 5542's and it did the job. However, if you saw our 2016 robot, we also have a steel subassembly that carried most of the carnage that the Strongholds defenses mustered.

We also used rivets extensively and none broke - replaced, but never failed.

We will continue to use the GTAW process as it provides students a way to learn a new welding process - but it will never be a prominent process of joining for our robots.

Oh - and NDSU's Bison Robotics Greenhorns Robot was named Rivvet for a reason. It was completely assembled using rivets.

Re: Is Welding Worth It?
 

A high school student can absolutely learn to TIG weld proficiently with enough practice. In fact, my student's welds were hanging on Einstein, on 330's robot.... :D

Re: Is Welding Worth It?
 

Re: Is Welding Worth It?
 

What size rivets are you using? If its the 5/32" rivets that fit in the predrilled holes then theirs your problem. 4592 was having them pop out last year quite often and this year switched to 10-32 screws and aluminum 3/16 rivets and had no problems since then. Also the quality of rivet installation makes a huge difference. Getting a pneumatic rivet gun if your not using one already is a great way to improve quality over a hand rivet gun and speed up mechanism assembly.

Welding will most likely work but its a more catastrophic failure and I would not risk it unless you have a drop in replacement for any welded sub-system or have someone experienced in welding aluminum. Another option is to gusset and weld as the gussets will both provide extra strength and hold the pieces together making them easier to weld.

Re: Is Welding Worth It?
 

If a weld breaks at competition? Gusset and rivet to reinforce the failed or failing weld. Not the end of the world. We have outsourced welding before but just purchased a TIG. We have students interested in that craft as a trade. Can't think of a better reason to weld when it is structurally applicable.

Re: Is Welding Worth It?
 

In the past from 1996-2010 all of our frames have been welded, generally using 6061-T6 as the base material. But we also would have our frames sent out for annealing and heat treat post welding because of the HAZ reducing the welded areas back down to T0... This added much delay in getting a rolling chassis up.

After switching to bolted and riveted construction we haven't looked back, mind you we had our frames welded by aerospace welders and we still popped welds in the pre bumper era......... ::ouch::

Re: Is Welding Worth It?
 

Benefits to Welding:
1. It gives some added flexibility to the design process

Benefits to Rivets:
1. Most teams send things out to be welded. This takes time. Even if you think it doesn't - it does.
2. You can take a rivet out. Removing a weld is much harder.
3. You can replace rivets. You can add rivets. At a competition.
4. Rivets are rivets. Not all welds are welds. Welds can look perfect from the outside but if the welder didn't get penetration it will fail at the worst possible time.
5. Rivets are easy.
6. Rivets are cheap.
7. Rivets don't have a safety downside.
8. It's rare you run out of rivet map gas, rivet rod, or jam up your rivet wire auto-spooler.
9. If a rivet joint gets wiggly - add more rivets. If a weld joint gets wiggly, you've got problems.

To be absolutely fair - we welded our chassis this year. We have every year since 2008. We also welded our arms. The connection between our chassis and our arm snapped on our practice bot due to lack of weld penetration. The weld on our arm snapped on our comp bot 3 times because it simply wasn't strong enough. The solution at the competition was flat plates over the weld - riveted on.

In summation, unless you have someone who already knows how to tig weld and you're keen on teaching your students, or you have an over-abundance of time, I'd stick with riveting and focus on other portions of your robot process.

As an afterthought.... look at some of the critical joints on 254's robot. They are both welded, and riveted.

Re: Is Welding Worth It?
 

We also switched over to aluminum rivets with steel mandrels. They are a lot harder to rivet, but all too often we had poor quality Chinese rivets that would break the mandel above the rivet. Never happened again with the steel mandrel, and our forearms all look like popeye's :D

Re: Is Welding Worth It?
 

Anyone have suggestions for which epoxy to use for bonding aluminum?

Re: Is Welding Worth It?
 

We use Hysol E60HP

The long cure time is a bit of a pain but the extra strength it gives you is worth the wait. We have used it for years with great results. Rough up the surfaces you are bonding and you aluminum will break before the bond does.

Re: Is Welding Worth It?
 

You can go down the rabbit hole with this. But. More important than the specific epoxy is surface prep. Epoxy works best in shear with lots of surface area. Preferably you would want to strip the oxide layer of the aluminum. At the very least scuff it with 80 grit. The surface should be thoroughly cleaned and de-greased. Reference one
West systems has a lot of how to for epoxy.

Re: Is Welding Worth It?
 

Welding can be a lot of fun and in my opinion has more pros in terms of creating a lighter and more durable chassis, however there will be some issues if we are letting the students weld. We need to make sure we have a ventilated and high ceiling shop, PPE needs to be addressed to everyone, and who ever is welding needs to be highly supervised. Another perspective is just creating a better designed robot. Stronghold was tough.

Re: Is Welding Worth It?
 

This is quite a vague question that depends much on the team. As Andy A said, 95 welds where it makes sense for us. Welding, especially with sheet metal, opens up a lot of design flexibility that we enjoy taking advantage of.

As with any choice in FRC it's not the choice itself that matters, but the execution. We design self-fixturing or easy-to-fixture components, accessible welding locations, and have access to a lot of nice equipment. A team should not expect to get a welder and see success, it will take practice and expertise to do well.

Using a welder safely is no more difficult than using any other piece of shop equipment safely. In fact, a welder is probably safer than many pieces of shop equipment an FRC team might use.

I would not recommend 'sticking only with 6061.' After welding, an aluminum is generally in the "T0" state, in which 5052 has 28ksi UTS and 13ksi YS whereas 6061 has 18ksi UTS and 8ksi YS. This is just one example, there is much research to be done! Some alloys, such as 7005, can age at room temperature back to essentially full strength.

Furthermore, welding in FRC shouldn't be limited to aluminum only. Low alloy steels are easy to weld or braze, offer great strenth:weight ratios, and are not expensive. There are other design considerations for sure, but steel should be 'on the table' when discussing welding.

Surface prep is paramount here. Look at the epoxy supplier's suggestions for surface prep. I would recommend 3M DP 190, 420, or 460 for most applications, and Hysol 9309 for critical applications (it has glass beads to arrest crack growth and ensure an optimal bond gap). I would strongly recommend an elevated temperature cure rather than an ambient temperature cure for time and strength reasons.

Re: Is Welding Worth It?
 

Not so fast there - we use 5/32" rivets on almost everything, including our drive base (except this season which was brutal) and haven't had any issues.

Our team has found that drilling the correct size hole is the real key to having rivets stay in and be secure. For 5/32", you should be using either a #20 or #21 drill bit. Refer to the handy table on this page - http://www.engineersedge.com/rivet_application.htm

Re: Is Welding Worth It?
 

192 students has been welding for 20 years. Most of our welders learn in the in the fall with some starting the year before. Only a few have welded for years. Early on it was .125 or thicker. About 8 years ago I showed some students how to check for penetration by breaking welds with a hammer.::ouch:: With the increase skill due to their critiquing their own welds we now weld .062 and thicker. 192 also rivets and has found that 3/16 and 1/4 rivets work rather nice and have few problems.

Re: Is Welding Worth It?
 

We've been using E-120HP (same family) and have been happy with it.

We clean and degrease the surfaces after abrading for a better joint as well.

Re: Is Welding Worth It?
 

We've discussed welding but haven't gone down that path. Our frames for the past 3 years have been riveted with 3/16" stainless rivets (they were free...). We sheared no rivets and the frame was easily repaired when it needed to be.

Re: Is Welding Worth It?
 

No one has mentioned brazing aluminum:
http://muggyweld.com/super-alloy-5

Re: Is Welding Worth It?
 

::rtm::

Re: Is Welding Worth It?
 

Well they did not mention MuggyWeld.
So I think you could have snark lite on that but point taken.

Re: Is Welding Worth It?
 

Brazing Aluminum is best done with a specialized Flux first to reduce the oxidation layer and help the braze to flow. There are quite a few different Aluminum braze rods out there. I just mentioned some.

Using a rod with flux in it is fine, but is a poor subistute for applying AL flux first. The Benzomatic AL3 rods are available at Home Depot stores, and are thus the easiest to find for most with no shipping.

Re: Is Welding Worth It?
 

Welding is totally worth it in my opinion. I have welded for my team for the past 3 years, and it takes a lot of practice and patience to get to a place where you can weld for your teams robot. It took my team mate and I a whole summer of practice to be good enough to weld our robot. This year, while I welded our competition bot I was training new students by having them weld our practice bot, so they are ready for next season. The many pros and cons robot wise have allready been said in this thread, and I also think it's a great thing for students to add to their resume, and a good skill to have. I know my teammate and I (and I'm sure many other students) have been given job offers and scholarships because we can weld. If a team can afford a welder and has someone to teach students how to weld, I think the pros definetly outweigh the cons.

Re: Is Welding Worth It?
 

Do you have any comments about brazing versus welding AL? This looks like a really viable option for low-resource teams.

Re: Is Welding Worth It?
 

I generally prefer riveted construction when practicable for frames. Otherwise bolted fasteners. Even with experienced teams, you'll have much more consistent build quality that way.

We did weld some steel bumper attachments this year. We've used some welded structure in the past as well. Welding is a useful capability, but it takes a lot of practice to make good welds.

There are some situations such as a swerve drive pivot tube that welding or brazing simplifies the construction details.

I've brazed repaired aluminum automotive parts. It similar to brazing copper plumbing, it's much easier skill to learn then good TIG welding.

Re: Is Welding Worth It?
 

We had problems in past with riveted joints coming loose over time. We have since switched to Avex 1661 series rivets in 5/32 and 3/16 sizes with proper sized drill bits that we keep stored in our rivet box. The 1661 series seem to be more forgiving related to misalignment and pull the material together very tight before snapping maintaining strong joints throughout the season. We didn't have any issues all year with our rivetted VersaChassis and we will likely use the same approach going forward.

However, if we had the ability to weld, we'd likely utiize it to simplify our construction in key areas of the robot.

Re: Is Welding Worth It?
 

We've welded our robot for the past 2 years. When you design before you weld, it works out very well. We use aluminum TIG welds.
I would say yes, welding is very much worth it.

Re: Is Welding Worth It?
 

They are generally only riveted to serve as fixturing for the welder, so that no hand alignment is necessary. Since we've started doing that we've gotten huge increases in quality and reduction in time it takes for the welding to be completed.

Re: Is Welding Worth It?
 

Interesting lesson learned. Maybe we will put it into practice too.

Re: Is Welding Worth It?
 

Can't recommend this enough. 971 also generally rivets together assemblies before welding. It allows us to fixture the assembly the way we want before its welded, which makes it much easier for the welder, much easier to transport to the welder's shop, and helps eliminate inconsistencies due to the welding process. We have seem much better results with pre-riveted welded assemblies.

Re: Is Welding Worth It?
 

192 also rivets before welding many of the parts.

Re: Is Welding Worth It?
 

Add 696 in there for one more ditto.

Re: Is Welding Worth It?
 

Just adding that although welds do weaken metal you have to keep in mind that drilling lots of holes in a piece of metal for rivets or bolts can weaken it as well. Welds, if done RIGHT are the strongest option, but rivets and bolts are faster.

Re: Is Welding Worth It?
 

This is an impossible statement to make accurately with so little information.

There are applications where each is the best.

Re: Is Welding Worth It?
 

We have a student who is extremely good at welding. So, we've been welding our chassis for a very long time. Personally, I'd recommend it if you have the resources and the skills. We had 0 issues with damage to our chassis going over any of the defenses thanks to robust welds. I don't know much about it, but it seems there's a lot of depth to the skill. I'd go for it if you can.

Re: Is Welding Worth It?
 

+1 Nothing looks nicer than a stack of dimes laid down.

Re: Is Welding Worth It?
 

Welding definitely helped with keeping stress points from bending and/or partially breaking.
Yes, it is expensive when compared to riveting. But the amount of metal shavings created by drilling your own rivet holes makes for a lot more cleanup, and risk of electronics shorting.

Re: Is Welding Worth It?
 

Hi The Swaggy P,

I'd like to address your point about rivet holes creating more cleanup and risk of electronics shorting.

Ideally you should be drilling these holes before installing any electronics! But in the off chance that you have to I'd suggest having a two man crew (never run equipment alone! HSA wouldn't like that!) Where one holds a rag and a vaccum while the other drills. Additionally I would suggest placing a cloth over top of any vital electrical equipment underneath. This should both protect your equipment and reduce the cleanup!

Hopefully this makes your life a little easier and your fastening experiences a bit brighter. Happy popping!

Also happy Memorial day weekend. God bless our troops.

Best Regards,
Rivet Man

Re: Is Welding Worth It?
 

welding is worth it if your design requires more customization than can be done to a kit bot frame. When a student is capable of welding a chassis correctly, the first time, it is quick and not a bad idea. One year a sponsor did it for us it was done wrong, after 2 weeks. That year it would have been better for a kit bot frame.

Re: Is Welding Worth It?
 

Why do you have to weld to have a not kitbot frame?? This year we had an 090 bent sheet metal chassis that had about 600 rivits in it with no welding.

Re: Is Welding Worth It?
 

+1. Our 2014 Aerial Assist chassis was c-channel and tubes bolted together using flat angles and Ts as gussets. Even as violent as AA was, frame strength was not one of our problems.

Re: Is Welding Worth It?
 

We weld, rivet, bolt, bond our robot assembles. Isn't engineering about evaluating and choosing the best method to solve problems?

Re: Is Welding Worth It?
 

If you use thin sheet alum it can sometimes be better to weld. Though usable, rivets and bolts could rip out or bend the metal. A long weld, not just a spot weld, has more surface area connecting the two pieces. However, if you need precise pieces it's easier to rivet or bolt. I'm not saying keeping welded pieces flat is impossible, just harder.

Re: Is Welding Worth It?
 

Hi Spark,

Going to pretend I'm Weld Man here for a second...but if you're talking about bending the metal, a continuous weld is always going to produce more warping in a part than riveting if all else is equal.

Mainly what happens is you heat up the metal and it gets softer (more malleable, and a bunch of other science jargon). So what happens is it'll distort and actually pull to a side. Afterwards there will be additional stresses inside the material (as with all fastening systems, that's how they work) that keep the material bent out of place.

Even if you preset your material and had it exactly in place, a long continuous weld is 100% going to distort a thin sheet of aluminum. Fortunately, rivets have your back and could be used to hold the sheet in place to help reduce warping.

Here's a link that has some good tips on how to mitigate these warps.
http://weldingdesign.com/archive/avo...ion-thin-sheet
Main points from this link are things like, backward walking, non-continuous/stitch welding, and presetting.

It's true that rivets can bend a thin piece of aluminum, but that would mean you have other issues in your setup. If your pieces aren't mated correctly (air gaps, bends aren't proper) when you're about to rivet then yes, rivets will bend your rig...they're trying to pull the pieces together after all! And if we're talking about the retaining mandrel or the head impinging on the surface of the metal...chances are you're using too much force on too soft a material, that ones on you and not the rivet!

Rivets are only as good as the person/design that's using them, and they're definitely not the bad guy!

Best Regards,
RM

Re: Is Welding Worth It?
 

There is a school of though that suggest stitch welding may be superior to seam welding for certain applications. If a crack starts in a stitch weld it will break through one stitch and then stop, providing a good visual cue to the operator/maintainer, and easy access for repair. If a seam weld cracks or un-zips it can propagate a large distance before it is detected and may be more difficult to properly repair.

What makes seam weld cracks harder to repair is guessing where to drill the stop-hole for the crack, because a crack will propagate further than is visually detectable. Of course X-ray or magnaflux (and other technologies) can help, but that's a whole other level from FRC. With a broken stitch weld the whole stitch can be cut and re-welded (if not already broken) with no need for a stop hole.

I'm going to stop myself here on the 'seam vs stitch' discussion unless there is a debate or questions that arise.

To put some 'science jargon' there...

The metal will change shape due to extreme localized heating of the weld pool driving thermal growth of the material. Any softening is secondary this CTE (coefficient of thermal expansion) driven growth.

Warping can be managed by proper design, small or non-existent root gaps, fixtures, and sufficient tack-welding prior to seam welding. If a part comes out warped there are many ways to correct it that include bending, re-heating welds (sometimes with fixtures), cutting, stress-relieving (sometimes with fixtures), or any combination of the above.

Re: Is Welding Worth It?
 

Welding is the most appropriate thing to do in this situation.

Re: Is Welding Worth It?
 

If you want to see lots of examples on how to weld thin sheets, google automotive sheet metal repair. It is mostly done with steel, but lots of YouTube video. Welding in such a way to minimize distortion is an art and science. For heavier weldments you have to calculate and allow for shrinkage. There is only so much that stress relieving will do.

One large scale example of thin sheet frames are airplanes. They are mostly riveted or glued and riveted.

Re: Is Welding Worth It?
 

Some eye candy of the art of welding sheet aluminum...(click on build photos)
http://www.p4bynorwood.com/

Re: Is Welding Worth It?
 

I think I saw some rivets... Anyway I want one. I think it is more than we are allowed to spend on an FRC bot though...

Re: Is Welding Worth It?
 

There are lots of rivets but the welded seams on the front and rear fenders in particular are quite impressive imo. WRT the rear fenders, you can see the use of several holes to enable clecos to hold the panels tight while welding the seam.

Re: Is Welding Worth It?
 

I didn't mean to imply there wasn't welding. I still want one. Or a GT-40, 917...