Plasma Cutter Gets CNC Treatment At Low Cost

[Daniel] has been metalworking on a budget for a while now. Originally doing things like plasma cutting on old bricks, he used his original plasma cutter to make an appropriate plasma cutting table complete with a water bath which we presume was not only safer but better for his back. Since then he’s stepped up a little more with what might be the lowest-cost CNC plasma cutter that can reliably be put together.

The CNC machine uses a handheld plasma cutting torch as its base, which uses a blowback start mechanism making it usable in an automated CNC setup without interfering with the control electronics. This is a common issue with other types of plasma cutters not originally meant for CNC. The torch head only needs slight modifications to fit in a 3D printed housing designed for the CNC machine which involves little more than slightly changing the angle of the incoming copper tubing and wire and changing the location of the trigger.

With those modifications done, the tool head is ready to be mounted to the CNC machine. [Daniel] has put together a bill of materials for building the entire project for less than $400, which includes the sub-$200 plasma cutter. It’s an impressive bit of sleuthing to get the price down this low, but if you’re still using your plasma cutter by hand on bricks in the yard like [Daniel] used to do make sure to check out that DIY plasma cutting table he built a few years ago too.

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High Voltage Turns Welder Into Plasma Cutter

For doing basic steel welding, most of us will reach for a MIG welder. It might not be the best tool for every welding job, but it’s definitely the most accessible since they tend to use only basic parts, easy-to-find gas, and can run from a standard electrical outlet. A plasma cutter isn’t as common, and while they’re certainly useful, [Rulof] wanted to forgo the expense of buying one off the shelf. Instead, he used parts of an old welder and a few other odds and ends to build his own plasma cutter.

The welder he’s working from in this project uses low-voltage alternating current to drive the welding process, but since a plasma cutter ionizes gas it needs high-voltage direct current. A 200 A bridge rectifier with some heat sinks from a Mac and an old stereo get this job done, but that’s not the only step in the process. A driver board and flyback transformer is used to generate the high voltage needed for the cutting head. There are some DIY circuit protection and safety features built in as well, including a spark gap using two nails, galvanic isolation from a transformer built from copper pipe, and some filtering coils made from old copper wire and iron bars.

With everything connected to the old welding machine and some pressurized air inside to push out the plasma, [Rulof] has a functional plasma cutter that can make short work out of a variety of metals at a fraction of the cost of a commercial tool. With the cutting tool finished, we’d recommend mounting it to a home-built CNC machine next.

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Hackaday Links: October 1, 2023

We’ve devoted a fair amount of virtual ink here to casting shade at self-driving vehicles, especially lately with all the robo-taxi fiascos that seem to keep cropping up in cities serving as testbeds. It’s hard not to, especially when an entire fleet of taxis seems to spontaneously congregate at a single point, or all it takes to create gridlock is a couple of traffic cones. We know that these are essentially beta tests whose whole point is to find and fix points of failure before widespread deployment, and that any failure is likely to be very public and very costly. But there’s someone else in the self-driving vehicle business with way, WAY more to lose if something goes wrong but still seems to be nailing it every day. Of course, we’re talking about NASA and the Perseverance rover, which just completed a record drive across Jezero crater on autopilot. The 759-meter jaunt was completely planned by the onboard AutoNav system, which used the rover’s cameras and sensors to pick its way through a boulder-strewn field. Of course, the trip took six sols to complete, which probably would result in negative reviews for a robo-taxi on Earth, and then there’s the whole thing about NASA having a much bigger pot of money to draw from than any start-up could ever dream of. Still, it’d be nice to see some of the tech on Perseverance filtering down to Earth.

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A silver and black bike sits in front of a dark grey bridge. It is on a hard surface next to green grass. The bike has a large basket area in front of the steering tube that then connects to the front wheel which is at the other end of the basket from the handlebars. It is best described as a long john bike, but is a more modern take on it than the wooden box Dutch bike.

Building A Cargo Bike Dream

Cargo bikes can haul an impressive amount of stuff and serve as a car replacement for many folks around the world. While there are more models every year from bike manufacturers, the siren song of a custom build has led [Phil Vandelay] to build his own dream cargo bike.

The latest in a number of experiments in hand-built cargo bike frames, this electrified front-loader is an impressive machine. With a dual suspension and frame-integrated cargo area, this bike can haul in style and comfort. It uses a cable steering system to circumvent the boat-like handling of steering arm long john bikes and includes a number of nice touches like (mostly) internal cable routing.

The video below the break mostly covers welding the frame with [Vandelay]’s drool-worthy frame jig, so be sure to watch Part 2 of the video for how he outfits the bike including the internal cable routing and turning some parts for the cable steering system on the lathe. If you get an urge to build your own cargo bike after following along, he offers plans of this and some of his other cargo bike designs. [Vandelay] says this particular bike is not for the beginner, unlike his previous version built with square tubing.

Looking for more DIY cargo bikes? Checkout this Frankenbike, another front loader, or this Russian trike.

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Hackaday Links: August 27, 2023

We mentioned last week how robotaxi provider Cruise was having a no-good, very bad week, after one of their driverless taxis picked a fight with a semi, and it was revealed that amorous San Franciscans were taking advantage of the privacy afforded by not having a driver in the front seat. It appears that we weren’t the only ones to notice all the bad news, since California’s Department of Motor Vehicles issued an order to the company to cut its robotaxi fleet in half. The regulatory move comes after a recent Cruise collision with a fire truck, which injured a passenger in the taxi. Curiously, the DMV order stipulates that Cruise can only operate 50 vehicles during the day, while allowing 150 vehicles at night. We’d have thought the opposite would make more sense, since driving at night is generally more difficult than during daylight hours. But perhaps the logic is that the streets are less crowded at night, whereas daytime is a more target-rich environment.

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Making Things Square In Three Dimensions

Measure twice, cut once is excellent advice when building anything, from carpentry to metalworking. While this adage will certainly save a lot of headache, mistakes, and wasted material, it will only get you part of the way to constructing something that is true and square, whether that’s building a shelf, a piece of furniture, or an entire house. [PliskinAJ] demonstrates a few techniques to making things like this as square as possible, in all three dimensions.

The first method for squaring a workpiece is one most of us are familiar with, which is measuring the diagonals. This can be done with measuring tape or string and ensures that if the diagonals are equal lengths, the workpiece is square. That only gets it situated in two dimensions, though. To ensure it’s not saddle-shaped or twisted, a little more effort is required. [PliskinAJ] is focused more on welding so his solutions involve making sure the welding tables are perfectly flat and level. For larger workpieces it’s also not good enough to assume the floor is flat, either, and the solution here is to minimize the amount of contact it has with the surface by using something like jack stands or other adjustable supports.

There are a few other tips in this guide, including the use of strategic tack welds to act as pivot points and, of course, selecting good stock to build from in the first place, whether that’s lumber or metal. Good design is a factor as well. We’ve also featured a few other articles on accuracy and precision,

Rocket Stove Efficiently Heats Water

Rocket stoves are an interesting, if often overlooked, method for cooking or for generating heat. Designed to use biomass that might otherwise be wasted, such as wood, twigs, or other agricultural byproducts, they are remarkably efficient and perform relatively complete combustion due to their design, meaning that there are fewer air quality issues caused when using these stoves than other methods. When integrated with a little bit of plumbing, they can also be used to provide a large amount of hot water to something like an off-grid home as well.

[Little Aussie Rockets] starts off the build by fabricating the feed point for the fuel out of steel, and attaching it to a chimney section. This is the fundamental part of a rocket stove, which sucks air in past the fuel, burns it, and exhausts it up the chimney. A few sections of pipe are welded into the chimney section to heat the water as it passes through, and then an enclosure is made for the stove to provide insulation and improve its efficiency. The rocket stove was able to effortlessly heat 80 liters of water to 70°C in a little over an hour using a few scraps of wood.

The metalworking skills of [Little Aussie Rockets] are also on full display here, which makes the video well worth watching on its own. Rocket stoves themselves can be remarkably simple for how well they work, and can even be built in miniature to take on camping trips as a lightweight alternative to needing to carry gas canisters, since they can use small twigs for fuel very easily. We’ve also seen much larger, more complex versions designed for cooking huge amounts of food.

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