Welding is often a hot and noisy process. It generally involves some fancy chemistry and proper knowledge to achieve good results. Whether you’re talking about arc, TIG, or MIG, these statements all apply.
The same is true for explosion welding, though it’s entirely unlike any traditional hand welding methods you’ve ever seen before. Today, we’ll explore how this technique works and the applications it’s useful for. Fire in the hole!
Don’t Blow Them Apart, Blow Them Together!
The technique of explosion welding is relatively new compared to other metal-joining techniques. In the two World Wars of the 20th century, pieces of shrapnel were often found stuck to armor plating. Close observation showed that shrapnel was in fact welding on to metal armor, rather than simply being embedded in such. Given that collisions between shrapnel and armor often occur without the extreme heat of typical welding operations, it indicated that it was instead great velocity of the impact between shrapnel and armor that was melding the metals together.
The same results were later recreated in the lab, and explosoin welding was developed into a refined technique after World War II. 1962 saw DuPont patent a process for explosion welding later to be known under the “Detaclad” trademark.
YouTuber [Linguoer] has a knack, and it’s one that we don’t often see on the pages of Hackaday: rewinding and rebuilding dilapidated motors and generators. In the video below, you’ll see [Lin] take a hydroelectric turbine and generator that looks like it’s been sitting at the bottom of a lake, and turn it into a working unit, all while wearing her trademark blue and yellow denim jumpsuit.
Where as most makers would have used a MIG or TIG welder, [Linguoer] uses a simple (probably A/C) stick welder. Generator windings are calculated and wound by hand, and the carcass of what used to be the generator is sandblasted out in the open. Missing parts are fabricated from scratch using nothing more than an angle grinder. “Simple” is the order of the day.
[Linguoer] often refers to herself as “Village Girl”. Whatever specialty tools she uses, they are elementary. And whatever methods she uses, they are manual. You will get the idea very quickly that [Linguoer] isn’t just a person with a skill, but a person with a passion for getting things done no matter the circumstances. [Linguoer] is a hacker if there ever was one!
[Julian] needed to weld a bit of nickel to some steel and decided to use a spot welding technique. Of course he didn’t have a spot welder sitting around. Since these are fairly simple machines so [Julian] set out to build a spot welder using a charged supercapacitor. The fundamentals all seem to be there — the supercap is a 100 Farad unit and with a charge of 2.6V, that works out to over 300 joules — yet it simply doesn’t work.
The problem is in how the discharge energy is being directed. Just using the capacitor would cause the charge to flow out as a spark when you got near the point to discharge. To combat this, [Julian] put a microswitch between the capacitor and the copper point he expected to use as the welding tip. The microswitch, of course, is probably not the best for carrying a large surge of current, so we suspect that may be part of why he didn’t get great results.
The other thing we noticed is that he used a single point and used the workpiece as a ground return. Most spot welders use two points near each other or on each side of the workpiece. The current from the capacitor is probably just absorbed by the relatively large piece of metal.
The second video below from [American Tech] shows a 500F capacitor doing spot welding with little more than two wires and it seems to work. Hackaday’s own [Sean Boyce] even made one out of some whopping 3000F caps. It did work, although he’s been pursuing improvements.
Beginning metalworkers are often surprised at just how cheap steel can be. It’s a commodity made by the gigaton, and there are always plenty of extra pieces and scraps left over from big projects that are available for pennies a pound. But what you’ve got is often not what you need, especially when it’s steel tubing with welded seams that prevents one tube from fitting inside another.
[Jason Marburger] from Fireball Tool has some great tips for cleaning interior welds in steel tubing. The first part of the video below details manual methods for cleaning off seam welds, including chiseling, sanding with a narrow belt sander, and grinding them down with a die grinder. Those all work well, but only for short lengths of tubing. Longer tubes need special treatment, which is where the clever tools [Jason] designed come in handy.
By attaching a chunk of high-speed steel to a slug made from the next size tube down and driving it through the tube to be cleaned with a hefty piece of threaded rod, he basically created ain internal shaper to shave the weld down. It works like a charm, as does the tool he made for round tubing by laying a bead of hard facing welding rod around the edge of a mild steel slug. Driving this tool into the seamed round tubing with a shop press cleaned up the weld nicely too.
3D printers hit the scene in a big way in the last decade, and thanks to the constant improvements that we’ve seen since then you can now get a decent one, assembled or as a kit, for a reasonable price. The one major drawback is that almost all of these printers are limited to printing in plastic, which has its obvious limitations. Printing in metal seems like the next logical step, and a group from Michigan Tech has created something that is accessible to most of us. Spoiler: they used plastic and metal printing to print a functioning axe.
Untill now, most metal printers have used a process like laser sintering to achieve the desired effect. This group uses a much more common tool: a MIG welder. MIG welders work by passing a wire through the welding handle, which would normally used as the filler material for the weld. If you use the wire for laying down material rather than for welding specifically, you can build up material on a surface in essentially the same way that a printer that prints plastic would.
From there, all that’s needed is to attach the MIG welder to a CNC machine and get to printing. The team has produced some great results so far, including some metal braces and farm implements, so hopefully their work leads to another revolution in 3D printing for the masses. We think it’s high time.
Welding equipment is always expensive and bulky, right? Heavens no! [Jaromir Sukuba] is making a welder for battery tabs which can fit in a pocket and gets its power from a coin cell. It may be expensive to power compared to a mains welder, but for the sake of portability this is quite the hack. Not only that, but it uses 555 timers in the charging circuit.
His entry for the 2017 Coin Cell Challenge saps every bit of power from a coin cell and stores it up in a 100F supercapacitor bank. All that stored energy takes a long time to get into the supercapacitors but it comes out in a flash. In fact, it can take 12 hours to fully charge. For the convenience of size, we have to trade the convenience of speed. This should be a strong contestant for the Supernova and Heavy Lifting categories.
We see a quick demonstration of a successfully welded tab which shows that using coin cells to weld metal to coin cells is equally ironic and apropos. Other welders on Hackaday feature a quicker way to control your battery tab welding, safety-rich spot welding, or just go off the rails completely and use an arc welder to make a coil gun.
Coin Cell Challenge
Build something cool powered by a coin cell, win prizes!
There are persistent rumors that the main ingredient in JB Weld is magic. This two-part epoxy that you would normally find on a shelf next to your basic 5-minute epoxy, Titebond, various cyanoacrylates, and Gorilla glue is somehow different. Stories of ‘some guy’ in the Yukon using JB Weld on a cracked engine block abound. These stories are of course met with skepticism.
Now, finally, we have evidence you can use JB Weld to fix an engine. [Project Farm] over on YouTube gave it the ultimate test: he took the cylinder head off a lawnmower, took a grinder to the head, and patched the hole with JB Weld. The head had good compression, and the engine actually ran for 20 minutes before the test was concluded.
If this were a test of a field repair, it would be a test of an extremely crappy field repair. [Project Farm] made no attempt to ensure the piston didn’t make contact with the blob of JB Weld, and in fact, there was some slight knocking from the piston tapping against a blob of epoxy. Still, this repair worked.
While this serves as proof of the feasibility of repairing an engine block with JB Weld, there is one ultimate test of JB Weld epoxy: build an engine out of it. For years, I’ve been casting my leftover JB Weld into a small square plastic container. In a few more years, I’ll have a block of JB Weld ‘stock’, large enough to machine the parts for a small (.049 cc) glow engine, like what you would find in ye olde tymie model planes and cars. Will it work? I have no idea, but now I can’t wait to find out.