3D Printed Axial Compressor Is On A Mission To Inflate Balloons

[Let’s Print] has been fascinated with creating a 3D printed axial compressor that can do meaningful work, and his latest iteration mixes FDM and SLA printed parts to successfully inflate (and pop) a latex glove, so that’s progress!

Originally, the unit couldn’t manage even that until he modified the number and type of fan blades on the compressor stages. There were other design challenges as well. For example, one regular issue was a coupling between the motor and the rest of the unit breaking repeatedly. At the speeds the compressor runs at, weak points tend to surface fairly quickly. That’s not stopping [Let’s Print], however. He plans to explore other compressor designs in his quest for an effective unit.

Attaching motor shafts to 3D printed devices can be tricky, and in the past we’ve seen a clever solution that is worth keeping in mind: half of a spider coupling (or jaw coupling) can be an economical and effective way to attach 3D printed things to a shaft.

While blowing up a regular party balloon is still asking too much of [Let’s Print]’s compressor as it stands, it certainly inflates (and pops) a latex glove like nobody’s business.

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Home Brew Sandblaster Is A Junk Bin Delight

Opinions vary as to what actually constitutes a “complete” shop, but one thing is for sure: the more tools, the better. That doesn’t mean running out to buy a tool every time you have a need, of course. Sometimes you can throw together what you need from scrap, as with this ad hoc sandblaster. (Video, embedded below.)

Fans of junk builds — and we mean that with the highest respect — will want to pay special attention to [GARAGEUA]’s video below. It looks like pretty much everything he uses to make this sandblaster comes from the junk pile — bits of old plumbing fixtures, a blow gun that’s seen much better days, some old nuts and bolts, and even a deceased spark plug all make an appearance. That last one is perhaps the most interesting, since with some clever dissection the spark plug’s body and its ceramic insulator were used for the nozzle of the sandblaster. And best of all, no lathe was needed for this job — everything was done with a hand drill and an angle grinder. Check out the build details in the video below; you might pick up some useful tips.

We’ve featured even junkier sandblaster builds before, but this one is a clever way to save a few bucks and flex a bit on your mechanical ingenuity. If you need a sandblaster and it’s something you’re going to use again and again, by all means go out and buy one — we won’t judge. But rolling your own is cool too.

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A Compressor Of Compressors Breaks The Noise Barrier

Having compressed air available in a workshop can be extremely useful. Having a compressor isn’t such a pleasure though, because unless it’s a very expensive model, it will be one of the noisier devices you own. Other than putting your compressor outside, is there a solution to the noisy side of having an air line? [Dominik Meffert] may have found one for his CNC plasma cutter in the shape of a rack of much quieter fridge compressors arranged in parallel with an air tank.

Of course, there’s nothing new about using a fridge compressor in the workshop. Indeed, such units are even commercially available as compressors for low-capacity tasks such as airbrushing. But we’ve never seen so many at once. It’s not entirely apparent how he’s handling the replacement of any lubricating oil that’s being caught in his filters, and we hope the refrigerant was disposed of safely, but we can see he’s on to something.

Fridge compressors have appeared here many times over the years, for more than compressing, we’ve even seen one as an engine. They aren’t always as strongly built as they should be though.

Fridge Compressor Teardown Reveals Engineering Compromises

Probably one of the most reliable devices you will have in your house is the refrigerator, as its compressor has the minimum of moving parts and carries its own lubrication. It’s not uncommon to find fridges many decades old still in use, and fridges are far more likely to be discarded due to broken fittings rather than a failed compressor. An interesting teardown of a failed fridge compressor comes from [turbokinetic], who gives us a professional analysis of how shortcomings in its construction caused it to fail. It’s both an opportunity for a look at the inside of a fridge compressor, and a commentary on the quality of consumer grade hardware.

Electrically the unit seemed unhurt, but the motor wouldn’t pump anything. Cutting the lid off revealed the motor, and it was soon established that the bearing had failed. As the teardown proceeded the conclusion was that the fault lay in the oil being too low viscosity. The designer had picked a very light oil in pursuit of low friction for lower energy consumption, but had ended up with one too light to provide adequate coverage within the bearing. The compressor has a lifetime of around ten years baked into it from manufacture, whether the designer intended it to or not.

You can see the full video below the break, but meanwhile this isn’t the first fridge compressor we’ve seen.

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Air-Assist Analysis Reveals Most Effective — And Quietest — Methods

If there’s one thing that continues to impress us about the Hackaday community as the years roll by, it’s the willingness to share what we’ve learned with each other. Not every discovery will be news to everyone, and everything won’t be helpful or even interesting to everyone, but the mere act of sharing on the off chance that it’ll help someone else is really what sets the hardware hacking world apart.

Case in point: this in-depth analysis of laser cutter air-assist methods. Undertaken by [David Tucker], this project reads more like a lab writeup than a build log, because well, that’s pretty much what it is. For those not into laser cutters, an air assist is just a steady flow of air to blow smoke and cutting residue away from the beam path and optics of a laser cutter. It’s simple, but critical; without it, smoke can obscure and reflect the laser beam, foul lenses and mirrors, and severely degrade cut quality.

To see what air-assist methods work best, [David] looked at four different air pumps and compressors, along with a simple fan. Each of these methods was compared to a control of cuts made without air assist. The test was simple: a series of parallel lines cut into particle board with the beam focused on the surface at 80% power, with the cut speed slowly decreasing. It turned out that any air-assist was better than nothing, with the conspicuous exception of using just a fan, which made things worse. Helpfully, [David] included measurements of the noise levels of the compressors he tested, and found there’s no advantage to using an ear-splitting shop compressor over a quieter aquarium air pump. Plus, the aquarium pumps are cheap — always a bonus.

Not sure how to get up to speed with lasers? Laser Cutting 101 might be a great place to start.

Clever Gas Mixer Gets Just The Right Blend For Homebrew Laser Tubes

[Lucas] over at Cranktown City on YouTube has been very busy lately, but despite current appearances, his latest project is not a welder. Rather, he built a very clever gas mixer for filling his homemade CO2 laser tubes, which only looks like a welding machine. (Video, embedded below.)

We’ve been following [Lucas] on his journey to build a laser cutter from scratch — really from scratch, as he built his own laser tube rather than rely on something off-the-shelf. Getting the right mix of gas to fill the tube has been a bit of a pain, though, since he was using a party balloon to collect carbon dioxide, helium, and nitrogen at measuring the diameter of the ballon after each addition to determine the volumetric ratio of each. His attempt at automating the process centers around a so-called AirShim, which is basically a flat inflatable bag made of sturdy material that’s used by contractors to pry, wedge, lift, and shim using air pressure.

[Lucas]’ first idea was to measure the volume of gas in the bag using displacement of water and some photosensors, but that proved both impractical and unnecessary. It turned out to be far easier to sense when the bag is filled with a simple microswitch; each filling yields a fixed volume of gas, making it easy to figure out how much of each gas has been dispensed. An Arduino controls the pump, which is a reclaimed fridge compressor, monitors the limit switch and controls the solenoid valves, and calculates the volume of gas dispensed.

Judging by the video below, the mixer works pretty well, and we’re impressed by its simplicity. We’d never seriously thought about building our own laser tube before, but seeing [Lucas] have at it makes it seem quite approachable. We’re looking forward to watching his laser project come together.

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Fridge Compressor Turned Into Capable Little Four-Stroke Engine

Never underestimate the power of a well-stocked junk bin. Along with a TIG welder and mechanical ingenuity bordering on genius-level, all of which come to bear on this fridge compressor to four-stroke engine build.

The video posted by [Let’s Learn Something] is long, but watching it at double speed doesn’t take away much from the enjoyment. By using a piston-type compressor, a lot of the precision machining is already taken care of here. Adding the intake and exhaust valves, camshaft, timing chain, carburetor, and ignition system are still pretty challenging tasks, though. We loved the home-made timing chain sprockets, made with nothing more than a drill and an angle grinder. In a truly inspired moment, flat-head screws are turned into valves, rocker arms are fabricated from bits of scrap, and a bolt becomes a camshaft with built-up TIG filler. Ignition and carburetion are cobbled together from more bits of scrap, resulting in an engine that fired up the first time — and promptly melted the epoxy holding the exhaust header to the cylinder head.

Now, compressor-to-engine conversions aren’t exactly new territory. We’ve seen both fridge compressors and automotive AC compressors turned into engines before. But most of what we’ve seen has been simple two-stroke engines. We’re really impressed with the skill needed to bring off a four-stroke engine like this, and we feel like we picked up quite a few junk-box tips from this one.

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