Fail of the Week: The Spot Welder Upgrade That Wasn’t

Even when you build something really, really nice, there’s always room for improvement, right? As it turns out for this attempted upgrade to a DIY spot welder, not so much.

You’ll no doubt recall [Mark Presling]’s remarkably polished and professional spot welder build that we featured some time ago. It’s a beauty, with a lot of thought and effort put into not only the fit and finish but the function as well. Still, [Mark] was not satisfied; he felt that the welder was a little underpowered, and the rewound microwave oven transformer was too noisy. Taking inspiration from an old industrial spot welder, he decided to rebuild the transformer by swapping the double loop of battery cable typically used as a secondary with a single loop of thick copper stock. Lacking the proper sized bar, though, he laminated multiple thin copper sheets together before forming the loop. On paper, the new secondary’s higher cross-sectional area should carry more current, but in practice, he saw no difference in the weld current or his results. It wasn’t all bad news, though — the welder is nearly silent now, and the replaced secondary windings were probably a safety issue anyway, since the cable insulation had started to melt.

Given [Mark]’s obvious attention to detail, we have no doubt he’ll be tackling this again, and that he’ll eventually solve the problem. What suggestions would you make? Where did the upgrade go wrong? Was it the use of a laminated secondary rather than solid bar stock? Or perhaps this is the best this MOT can do? Sound off in the comments section.

Continue reading “Fail of the Week: The Spot Welder Upgrade That Wasn’t”

Practical Plasma for Thin-Film Deposition

[Nixie] wants to sputter. We know, who doesn’t? But [Nixie] has a specific purpose for his sputtering: thin-film deposition, presumably in support of awesome science. But getting to that point requires a set of tools that aren’t exactly off-the-shelf items, so he’s building out a DIY sputtering rig on the cheap.

If you’re not familiar with sputtering, that’s understandable. In this context, sputtering is a process that transfers particles from one solid to another by bombarding the first solid with some sort of energetic particles, usually electrons or a plasma. When properly controlled, sputtering has applications from mass spectrometry to the semiconductor industry, where it’s used to either deposit thin films on silicon wafers or etch them away selectively.

No matter the application, sputtering needs a stable stream of plasma. [Nixie] has posted a series of articles on his blog walking us through his plasma experiments, from pulling a really strong vacuum to building a high-voltage power supply from a microwave oven transformer. It’s a project that needs a deep well of skills and tools, like glassworking, machining, and high-voltage electronics. Check out the plasma in the video below.

Will [Nixie] be using this for a DIY fab lab? Will it be used to make homebrew LEDs? The world waits to hear.

Continue reading “Practical Plasma for Thin-Film Deposition”

Not Just Your Average DIY Spot Welder

Microwave oven transformer spot welder builds are about as common as Nixie tube clocks around here. But this spot welder is anything but common, and it has some great lessons about manufacturing techniques and how to achieve a next level look.

Far warning that [Mark Presling] has devoted no fewer than five videos to this build. You can find a playlist on his YouTube channel, and every one of them is well worth the time. The videos covering the meat of what went into this thing of beauty are below. The guts are pretty much what you expect from a spot welder — rewound MOT and a pulse timer — but the real treat is the metalwork. All the very robust parts for the jaws of the welder were sand cast in aluminum using 3D-printed patterns, machined to final dimensions, and powder coated. [Mark] gives an excellent primer on creating patterns in CAD, including how to compensate for shrinkage and make allowance for draft. There are tons of tips to glean from these videos, and plenty of inspiration for anyone looking to achieve a professional fit and finish.

In the category of Best Appearing Spot Welder, we’ll give this one the nod. Runners-up from recent years include this plastic case model and this free-standing semi-lethal unit.

Continue reading “Not Just Your Average DIY Spot Welder”

Home-Brew Ruby Laser Packs A Wallop

In the past half-century, lasers have gone from expensive physics experiments using rods of ruby to cheap cutting or engraving tools, and toys used to tease cats. Advances in physics made it all possible, but it turns out that ruby lasers are still a lot of fun to play with, if you can do it without killing yourself.

With a setup that looks like something from a mad scientist movie set, [styropyro]’s high-powered laser is a lot closer to the ray gun of science fiction than the usual lasers we see, though hardly portable. The business end of the rig is a large ruby rod nestled inside a coiled xenon flash lamp, which in turn is contained within a polished reflector. The power supply for the lamp is massive — microwave oven transformers, a huge voltage multiplier, and a bank of capacitors that he says can store 20 kilojoules. When triggered by a high-voltage pulse from a 555 oscillator and an old car ignition coil, the laser outputs a powerful pulse of light, which [styropyro] uses to dramatic effect, including destroying his own optics. We’d love to hear more about the power supply design; that Cockcroft-Walton multiplier made from PVC tubes bears some exploration.

Whatever the details, the build is pretty impressive, but we do urge a few simple safety precautions. Perhaps a look at [Ben Krasnow]’s 8-kJ ruby laser would help.

Continue reading “Home-Brew Ruby Laser Packs A Wallop”

Your Work Won’t Move with a Magnetic Drill Press Vise

Setting up your workpiece is often the hardest part of any machining operation. The goal is to secure the workpiece so it can’t move during machining in such a way that nothing gets in the way of the tooling. Magnetic chucks are a great choice for securely and flexibly holding down workpieces, as this simple shop-built electromagnetic vise shows.

It looks like [Make It Extreme] learned a thing or two about converting microwave oven transformers to electromagnets when they built a material handling crane for the shop. Their magnetic vise, designed for a drill press but probably a great choice for securing work to a milling machine, grinder, or even a CNC router, has a simple but sturdy steel frame. Two separate platforms slide on the bed of the vise, each containing two decapitated MOTs. Wired to mains power separately for selective control and potted in epoxy, the magnets really seem to do the job. The video below shows a very thick piece of steel plate cantilevered out over one magnet while having a hole cut; that’s a lot of down force, but the workpiece doesn’t move.

Like the idea of a shop-made vise but would rather go the old-fashioned way? Check out [Make It Extreme]’s laminated bench vise, which also makes an appearance in this video.

Continue reading “Your Work Won’t Move with a Magnetic Drill Press Vise”

Harvesting Copper from Microwave Ovens

Obsolete appliances were once a gold mine of parts, free for the taking with a few snips of your diagonal cutters. Times have changed, though, and most devices yield only a paltry supply of parts, so much so that only by harvesting raw materials can you get much value out of them. And so we have this example of reclaiming copper from used microwave ovens.

The primary source of copper in most microwaves is the transformer, which we usually see re-tasked for everything from spot welders to material handling electromagnets. But the transformer is not the only source of the red metal; [eWaste Ben] also harvests it from relay coils and the main coil and shading coils of the fan motor.  The bounty is melted down in an electric foundry and cast in a graphite mold into a lovely ingot.

Unless you’re into repeatedly casting copper trinkets, a large bar of reclaimed copper might not be something you have a burning need to possess. But bearing in mind that copper can go for about $2.50 a pound at the scrap yard, there’s some money to be made, especially with dead microwaves essentially free for the taking. As [Ben] points out, taking the extra step to melt and cast the copper harvested from microwaves makes no sense if all you’re going to do is sell the scrap, but it’s nice to know how to do it just the same.

Continue reading “Harvesting Copper from Microwave Ovens”

Dual-Purpose DIY Spot Welder Built with Safety in Mind

Ho-hum, another microwave oven transformer spot welder, right? Nope, not this one — [Kerry Wong]’s entry in the MOT spot welder arms race was built with safety in mind and has value-added features.

As [Kerry] points out, most MOT spot welder builds use a momentary switch of some sort to power the primary side of the transformer. Given that this means putting mains voltage dangerously close to your finger, [Kerry] chose to distance himself from the angry pixies and switch the primary with a triac. Not only that, he optically coupled the triac’s trigger to a small one-shot timer built around the venerable 555 chip. Pulse duration control results in the ability to weld different materials of varied thickness rather than burning out thin stock and getting weak welds on the thicker stuff. And a nice addition is a separate probe designed specifically for battery tab welding — bring on the 18650s.

Kudos to [Kerry] for building in some safety, but he may want to think about taking off or covering up that ring when working around high current sources. If you’re not quite so safety minded, this spot welder may or may not kill you.

Continue reading “Dual-Purpose DIY Spot Welder Built with Safety in Mind”