Joining Sheet Metal Together With A DIY Spot Welder

July 4, 2015 by Rich Bremer 37 Comments

Once in a while there comes a time that you need a tool for one specific job. In these cases, it doesn’t make much sense to buy an expensive tool to use just once or twice. For most of us, Spot Welders would fall into this category. [mrjohngoh] had the need to join two pieces of sheet metal. Instead of purchasing a commercial unit, he set out to make his own spot welder.

A spot welder works by passing an electric current through two thin pieces of metal. The resistance of the metal work pieces and the current passed though them creates enough heat to melt and join the two together at a single spot. To be able to get the high current needed for this project, [mrjohngoh] started with an old microwave transformer. He removed the standard secondary coil and re-wrapped it with 1cm thick wiring to get maximum current out of the transformer. The ends of the coil wire attach to electrodes, which are made from a high-current electrical plug. The electrodes are mounted at the ends of a pair of hinged arms. The weld is made when the two pieces of metal are sandwiched between the electrodes and power is applied.

Spot welding isn’t just for joining two pieces of sheet metal. It’s also used for things like welding tabs onto battery terminals. The versatility and easy of building these welders make them one of the most featured tool hack we’ve ever seen.

Rotary Indexer Gives Mill A 4th Axis (sort Of)

July 4, 2015 by Anool Mahidharia 23 Comments

Rotary indexer’s are standard issue in most machine shops. These allow you to hold or chuck a work piece, and then a graduated handle lets you to rotate the workpiece. Useful when you want to drill or tap axial or radial features. A rack and pinion drive ensures that the workpiece does not move under machining load. Quite often, these indexers also have a manual lock to take care of gear backlash and play. Automating them is not too difficult either. You could use just a stepper motor (open loop) or servo+encoder (closed loop) to drive the turntable.

[smashedagainst] needed to drill six radial holes on a part. And he had to do it on 500 pieces for a total of 3000 holes. That was just for the first initial run, with more drilling likely in the future. The part in question was small and light weight. So instead of using a heavy duty, industrial grade unit, he built an all-electric rotary indexing jig using a stepper motor and an Arduino, giving him a sort of rotary 4th axis. His idea was to directly use the stepper motor to rotate the workpiece without any gearing, but he needed to build his own rig to do so.

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Getting Mixed Up With Home Stir Welding

July 3, 2015 by Kristina Panos 16 Comments

Most processes designed to join two pieces of what-have-you together are consumptive of something, whether it’s some material acting as a third party to work piece and the tool, or the tool itself. In the wonderful world of friction stir welding, the material of the two pieces under union gets swirled together through friction as the tool traverses the join path. There are, of course, professional machines that perform this with relative ease, but with a large amount of beer on the line, [skookum_choocher] was determined to make his own.

In the first video, he machines a friction welding tool by shaping a tungsten carbide button from a drill bit using a diamond grinder. Once he has a rough shoulder and protuberance going, it’s time to let her rip. Despite issues with clamping and the geometry of his tool, the weld is ultimately successful at the tail end.

Undeterred, he has another go at it after making some adjustments to the tool shoulder, changing the belt on his poor old Bridgeport, and increasing the clamping strength by a factor of four. You clamp sixteen tons, and whaddya get? A slightly better butt weld than the first time, it turns out. Fearing this weld is insufficient to win the bet, he goes for the lap weld with the work pieces stacked together in a sandwich. We prefer pizza with beer, but nevertheless congratulate him.

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DIY Air Compressor Made From Refrigerator And Fire Extinguisher

July 1, 2015 by Rich Bremer 59 Comments

[Giorgos] wanted to build a pneumatic solder paste application tool but needed an air compressor to power it. Instead of going out and buying a compressor, he decided to build one himself. It sure is an ugly duckling but we’re impressed with it’s performance.

The air tank is an old spent fire extinguisher. The stock valve was removed and the insides were cleaned out. Out of curiosity, [Giorgos] figured out the volume by filling the tank with water, then measuring how much water came out. It turned out to be 2.8 liters. Two holes were drilled and threaded bungs were welded on to attach inlet and outlet lines.

The compressor portion is straight out of a refrigerator. Besides the compressor being free, the other benefit is that it is super quiet! Check the video after the break, you’ll be astonished. [Giorgos] did some calculations and figured out that his solder paste applicator needed about 8 bar (116 psi) of pressure. The refrigerator compressor easily handles that, filling the tank in 1 minute, 25 seconds.

On the output side of the tank resides a pressure switch for automatically filling the tank and a regulator for ensuring the solder paste applicator gets the required pressure. This isn’t the first time we’ve seen a refrigerator compressor used as an air compressor. Check out this dual setup capable of 400 psi.

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Hacking A $100 Signal Generator

July 1, 2015 by Eric Evenchick 23 Comments

Signal generators are a useful piece of kit to have on your electronics bench. The downside is that they tend to be rather expensive. If you have $100 to drop on a new toy, the MHS-5200A is a low cost, two channel, 25 MHz generator that can be found on eBay.

The downside is the software. It’s an ugly Windows interface that’s a pain to use. The good news is that [wd5gnr] reverse engineered the protocol so you don’t have to. This means other software can be developed to control the device.

When connected to a computer, this function generator shows up as a virtual USB serial port. The documentation that [wd5gnr] assembled lists all the serial commands you can send, and what they do. If you aren’t into manually setting waveforms from a serial terminal (who is?) there’s a tool for doing that automatically on Github. This takes in a CSV file describing a waveform, and programs the generator to make it for you.

The software is also compatible with Waveform Manager Plus, a free GUI tool for defining waveforms. Putting this all together, you can have a pretty capable waveform generator for less than $100.

2D Printed Tachometer For A Lathe

June 28, 2015 by Brian Benchoff 31 Comments

If you ever wanted a reason to have DC lighting pointed at the spinny part of your mill and lathe, [Bill] tells a great story. One day, he noticed the teeth on his lathe chuck would change color – red, then blue, then red. His conclusion was the fluorescent lights above his workbench was flashing, as fluorescent lights normally do.

Imagine if the teeth on [Bill]’s chuck weren’t painted. They would appear stationary. That’s usually a bad thing when one of the risks of using a lathe is ‘descalping.’ Buy an LED or incandescent work light for your shop.

This unique effect of blinking lights got [Bill] thinking, though. Could these fluorescent lights be used as a strobe light? Could it measure the RPM of the lathe?

And so began [Bill]’s quest for a 2D printed lathe tachometer. The first attempt was to wrap a piece of paper printed with evenly space numbers around the chuck. This did not work. The flash from his fluorescent bulb was too long, and the numbers were just a blur. He moved on to a maximum-contrast pattern those of us who had a ‘DJ phase’ might recognize immediately.

By printing out a piece of paper with alternating black and white bands, [Bill] was able to read off the RPM of his chuck with ease. That’s after he realized fluorescent lights blink twice per cycle, or 120 times a second. If you have a 3″ mini-lathe, [Bill] put the relevant files up, ready to be taped to a chuck.

Custom Downdraft Fume Extractor for Soldering

Downdraft Fume Extractor Saves Your Lungs

June 27, 2015 by Eric Evenchick 21 Comments

When you’re soldering, smoke rises from your iron. That smoke is full of a variety of chemicals, depending on what type of solder you’re using, but it’s almost certainly not good for you. That’s why you can buy fume extractors to suck smoke away.

But benchtop extractors tend to suck, and not in the way they’re supposed to. It can be hard to get the extractor to pick up all the fumes, leaving fumes that float into your face.

Over at Other Machine Co., they built up a custom downdraft fume extractor to solve this problem. The downdraft extractor is a table that you work on, providing downwards suction that grabs the fumes. Their table uses a standard MERV13 air filter that’s rated to trap particles as small as 1.0–0.3 μm. Cooling fans provide the airflow, and a piece of perforated sheet metal acts as a work surface.

The table works great for soldering, and is also helpful for working with other chemicals like adhesives and solvents. DXF files for the frame parts are provided, and everything else can be sourced from McMaster.