I guess there really is a large audience of people out there who read these articles! I know this because I received many comments after my last squeeze-type resistance spot welding (STRSW) article ran in BodyShop Business (“See Spot Run,” August 2001). It was, evidently, widely read, and many people even took the time to forward me their questions and comments.
Because of this, my editor – always one to inspire me to greater heights (and more work) – deemed another article on the subject of STRSW was necessary.
Reader interest is a determining factor in these decisions and rightly so – although I sometimes think she (my editor) is just trying to milk every last drop of knowledge (or in her mind: value) out of my poor, blue-collar brain. I give her her due: She is good at what she does, milking brains for the knowledge from which her readership can benefit.
But what more can I give you on STRSW that you’ll benefit from? Plenty.
First, I’d like to make my usual disclaimers. I’m not an electrical engineer, nor a metallurgist. I have no experience on the original equipment (OE) side, as a manufacturer. And I’m not, nor have I ever been, a representative of a collision repair equipment manufacturer.
I’m a product of a vocational school called Emily Griffith Opportunity School in Denver, Colo. I’ve been in the collision repair industry since 1963, and I’ve owned a collision repair shop since 1972. I work on the line every day as a collision repair technician. I’m an ASE Certified Master Collision Repair/Refinish Technician and an I-CAR Platinum Class Individual. With that said, my comments and discussion points will be coming strictly from the practical side – what I’ve actually experienced, pro and con, when using STRSW in the everyday repair of collision-damaged automobiles.
Even the reference to STRSW seems to elicit comments from some quarters, although it shouldn’t since I’m really only discussing STRSW. I won’t go into single-sided spot welding, other than to say that most of the spot welders on the market have the ability to perform single-sided spot welding. Do I use single-sided spot welding myself? Almost never. Is the machine I use capable of performing single-sided spot welds? Yes.
I’ve used all of the attachments and have performed all of the optional functions that my current spot welder offers, which is basically the same as what most of the spot welders on the market today offer. The options are nice. I like the twist-off dent puller option. I use this a lot because I can actually metal finish with it. But your primary reason for purchasing a spot welder should be to perform factory-type, reliable, tested (by you) spot welds. This means, in my opinion, STRSW (even though some of the options offered may become selling points for you).
Before getting started, let me share with you a great quotation I heard on the radio the other day that truly speaks volumes about life – and collision repair: “Good judgment is the result of experience. Experience is the result of bad judgment.”
I have lots of experience.
Do Your Research!
Let’s talk a little bit about testing welds prior to welding your customer’s car. Most of you are probably thinking, “How am I going to do test welds before welding on a customer’s car when I don’t even own a spot welder. That’s why I’m reading this idiot’s article.”
OK … easy now. Take a deep breath. Now let me reason with you, and maybe I can save you a little dust (gold that is).
There’s a reason that I’ve owned four spot welders, and that reason has a lot to do with experience. Holy cow! That brings me back to the quotation about how experience is the result of bad judgment. Oh no! My wife proofreads these articles for me, so through a very small amount of deductive reasoning (that Sherlock Holmes stuff), she’ll be able to deduce that I exercised some bad judgment when I purchased three of those machines.
“But, honey, I used good judgment on the last one!”
Oh man. These things aren’t cheap either.
My point here is, test any potential purchase before you buy it. Would this include a reference or two supplied by the spot welder rep or, better yet, a fellow shop owner? Yes. But trust the competency of the reference with whom you’re talking. Is this a conversation between one desk jockey to another or are you talking with someone who’s really experienced this machine’s capabilities?
Also keep in mind that real-life conditions are different from the trade show floor. The trade show floor is a carpeted paradise, where clean pieces of sheet metal – cut in 3-inch squares – are welded together under the most ideal conditions by a highly qualified factory rep. And the rep religiously operates the demonstration machine well within its recommended limits.
But can you imagine one of your techs welding a side panel on a maxi-van with window openings, performing STRSW every 1.5 seconds as he races down the side thinking, “Hey this is the greatest invention since my new three-pound sledge”? It’s not much of a stretch, and if I can think of it, it can happen. I’m not that imaginative.
We work on the other end of the spectrum – in real life, non-supervised conditions. In our world, there’s more potential for duty cycle abuse – and overheating. I talked to one rep who used to be a tech in my shop. He told me that he’d been to a shop where the tech had actually melted the welder’s handles! This is probably why manufacturers invented the overheat relay switch on most of the current machines on the market.
Rushing Leads to Re-Dos
As a spot welder’s components heat up (cables, transformers, tips, etc.), its welding power can dissipate. Cycle time between welds is very important, and you should impress this upon your technicians using the machine. We’re talking in the six- to eight-second range here. Six to eight seconds! Wow, as compared to punching a hole, MIG welding, burning up the surrounding paint, burning yourself, carefully grinding down the weld, polishing the weld with fine abrasive and feather edging the burn area. Gee, how long would that take? One spot welder manufacturer says seven minutes. Maybe, maybe not, but for sure, making a MIG plug weld takes a hell of a lot longer than six to eight seconds!
Despite the time benefits gained by using a spot welder, human nature being what it is, there’s still a tendency to rush and to reduce that six to eight seconds per weld down to under a second. What this does – besides speeding things up – is compromise the integrity of the job. Still, some idiot will try it.
Don’t get me wrong. When a spot welder becomes overheated, it can still perform – but the welds will pop apart upon performing a test.
Thus, my “good judgment” has been gained by purchasing successively heavier-duty machines – until I finally bought one with sufficient transformer power and duty cycle. Price was the main contributing factor (I’m cheap). I kept hoping (bad judgment) the lighter duty and cheaper machines would fill my needs, all the time demanding the most superior outcome. This was unrealistic – and more costly than the prescribed method I’ve detailed to you. The machine I use now is a 220-volt, three-phase machine of the highest power. I’m completely pleased with it. Expensive? Oh yeah, but when I add up the cost of the predecessors to this machine, I ended up paying about 1.5 times more than if I’d simply bought the proper machine in the first place.
Performing a Test Weld
Because spot welding isn’t fool-proof, education is necessary. I’m an I-CAR Weld Quality Test examiner. Yeah, I’m one of those physical dudes who uses a big chisel and a three-pound hammer to test the ability of a welder to properly join two pieces of zinc-coated 18-gauge steel together according to American Welding Society Standards. But this is a MIG Welding test and is different from the standard STRSW method of testing a spot weld.
When it comes to testing spot welds:
- Perform your spot weld on metal that’s similar to what the vehicle is made from. Use the old panel if possible.
- Warm up the machine by first performing a dozen or so welds.
- Weld two coupons (sheets) prepared the same way as the vehicle and the new part (bare metal at contact points, weld through primer at any bare spots in between the coupons). Use the same power and timer settings as you will on the vehicle.
- Shove a screwdriver between the coupons, and twist until you’ve destroyed the weld. You should have a nugget on one coupon and a hole in the other if you have a successful spot weld.
Other Important Things to Consider …
- What the OEMs say – Do OEMs recommend STRSW? Many Japanese and European manufacturers do in specific situations. This is important to understand because most structural components (frame rails, etc.) still need to be MIG welded.
Daimler-Chrysler does recommend STRSW in conjunction with bonding. The process is called weld bonding and is used in limited applications. Ford and G.M., however, still don’t recommend STRSW – although I was told by Jack Aho, of G.M.’s Collision Repair Technology Center in Warren, Mich., that it’s under consideration.
Be sure to follow I-CAR’s recommended procedures and to use the manufacturer’s recommended method for repairing their particular vehicle.
- The Rule of 95 – The Rule of 95 is a concept I’ve heard put forth by a manufacturer rep that states that through the application of the welder’s attaching arms, pneumatic welding gun, mechanical gun etc., that 95 percent of the welds on a vehicle can be made with his machine.
What’s important for you to consider here is how accessible your future machine will be. Ask for a demonstration or, at least, question the rep on the machine’s versatility. Can it reach all the areas on a vehicle? Better yet, what areas can it reach? Is the only way for a welder to reach a radiator core support (structural) by employing single-sided spot welding? Ask the important questions to find out if the welder is right for you.
- The strength of STRSW compared to OE – Since the size of factory spot welds is larger than most aftermarket STRSWs, it’s an accepted requirement that we use 30 percent more welds on a repair in order to duplicate the strength of the OEM weld. For example: If you have 20 OE spot welds at the weatherstrip pinch weld on the latch pillar of a quarter panel, you should replace it with 26 STRSWs in that location. This will duplicate the original strength designed by the OEM.
- Facility size constraints – Think about this – unless it’s not a concern for you. I’ve had some technicians with toolboxes that take up the space of a car. But this is a production area.
My dream for a machine is to have the most compact, versatile, powerful machine on the market. My point is, determine the physical constraints of the machine and if they match your needs. We’re trying to find the best of both worlds, I know, but this is an important consideration. Think about it … and then think about it again.
- Less disturbance to factory coatings – If you’re located in a high salt or moisture area, you’ll love STRSW. This is a major benefit because this type of welding is much less intrusive – meaning that you destroy less of the factory coatings – than other types of welding. This is a positive in maintaining the integrity of the repair.
- After-purchase support – What kind of after-purchase support is available? Many machines come from outside this country. Will the machine you purchase be readily repairable in a reasonable locale, near you? “Why should it need repair?” you ask. Oh, because human beings will be using it, and many of these people could be hired immediately as Master Testers for Fool-Proof Industries. When abused, these machines can – and will – break. Is Sri Lanka the nearest repair depot, or is there something closer? And what is the turnaround time for a repair? Once you get used to using one of these STRSW machines, you’ll want it in your shop all the time. It’s a fantastic tool.
- Available training – This is truly important because using STRSW equipment is much more than pushing a switch. Why is the failure rate so high on the I-CAR Weld Quality Test? Not because the test is so hard, but because a large number of test takers haven’t been properly trained, nor have they pre-tested their own welds, as prescribed by I-CAR.
STRSW is no different. Although far less manual skill is necessary to become proficient at spot welding, you still need a base of knowledge to understand the machine’s limits and what you’re actually doing. Make sure training is available from the manufacturer of your prospective new STRSW machine.
Learn From My Mistakes … Please
Check out Web sites prior to getting hammered by a salesman, and write down a list of questions to ask the rep or a reference. Be prepared going in. And be thorough in your inquiries.
If you follow my suggestions and all the advice I’ve offered here, you’ll forego the experience-gaining, mistake-ridden portion of my personal journey, and you’ll skip right ahead to the good judgment part. It’s cheaper and easier. Trust me.
Writer Mike West, a contributing editor to BodyShop Business, has been a shop owner for almost 30 years and a technician for almost 40 years. His shop in Seattle, Wash., has attained the I-CAR Gold Class distinction and the ASE Blue Seal of Excellence.
Special thanks to Paul Struhar, owner of Centerline CARSTAR Collision Center in Strongsville, Ohio, for welcoming the BSB staff into his shop to take photos of the STRSW process.