Casting Gears At Home

Automatic doors and gates are great, except when they fail, which seems to be about every three days in our experience. [MAD WHEEL] had just such a failure, with a plastic gear being the culprit. Rather than buy a new drive unit, they set about casting a replacement in metal.

The video is light on instructions and heavy on progressive rock, and may be a little difficult to follow for beginners. The process begins by gluing the original plastic part back together, and filling in the gaps with epoxy putty. A mould is then created by setting the gear in a gelatine/glycerine mixture. This mould is then filled with wax to create a wax copy of the original part. The wax gear is fitted with cylindrical stems to act as runners for molten metal, and then a plaster mould is made around the wax positive. Two plaster moulds are made, which are placed in an oven to melt out the wax.

The aim was to cast a replacement part in aluminium. The first attempt failed, with the aluminium cooling too rapidly. This meant fine details like the gear teeth simply didn’t cast properly, creating a useless metal blob. On the second attempt, the plaster mould was heated first, and this kept things hot enough to allow the aluminium to fill in the finer details. With that done, it was a simple matter of some post-processing to remove the runners, clean up the gear teeth and refine the shape of the gear on the lathe.

The resulting part does its job well, meshing properly with the other gears in the drivetrain and moving the gate effectively. Many in the comments have stated that the original gear being plastic was likely as a safety measure, to strip out in the event the gate is jammed. While this may be true, it’s a far more robust design practice to instead use a breakable plastic key rather than breaking an entire gear in the event of a problem.

Casting is quite accessible to the dedicated home maker. It’s a great way to make custom metal parts once you’ve learned the fundamentals! Video after the break.

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KiCad Action Plugins

The last two years has been a particularly exciting time for KiCad, for users, casual contributors, and for the core developers too. Even so, there are many cool new features that are still in process. One bottleneck with open-source development of complex tools like KiCad is the limited amount of time that developers can devote for the project. Action plugins stand to both reduce developer load and increase the pace of development by making it easier to add your own functionality to the already extensible tool.

Sometime around version 4.0.7 (correct us if we’re wrong), it was decided to introduce “action plugins” for KiCad, with the intention that the larger community of contributors can add features that were not on the immediate road map or the core developers were not working on. The plugin system is a framework for extending the capabilities of KiCad using shared libraries. If you’re interested in creating action plugins, check out documentation at KiCad Plugin System and Python Plugin Development for Pcbnew. Then head over to this forum post for a roundup of Tutorials on python scripting in pcbnew, and figure out how to Register a python plugin inside pcbnew Tools menu. Continue reading “KiCad Action Plugins”

Used EDM Electrodes Repurposed As Air Bearings For Precision Machine Tools

If you’ve ever played air hockey, you know how the tiny jets of air shooting up from the pinholes in the playing surface reduce friction with the puck. But what if you turned that upside down? What if the puck had holes that shot the air downward? We’re not sure how the gameplay would be on such an inverse air hockey table, but [Dave Preiss] has made DIY air bearings from such a setup, and they’re pretty impressive.

Air bearings are often found in ultra-precision machine tools where nanometer-scale positioning is needed. Such gear is often breathtakingly expensive, but [Dave]’s version of the bearings used in these machines are surprisingly cheap. The working surfaces are made from slugs of porous graphite, originally used as electrodes for electrical discharge machining (EDM). The material is easily flattened with abrasives against a reference granite plate, after which it’s pressed into a 3D-printed plastic plenum. The plenum accepts a fitting for compressed air, which wends its way out the micron-sized pores in the graphite and supports the load on a thin cushion of air. In addition to puck-style planar bearings, [Dave] tried his hand at a rotary bearing, arguably more useful to precision machine tool builds. That proved to be a bit more challenging, but the video below shows that he was able to get it working pretty well.

We really enjoyed learning about air bearings from [Dave]’s experiments, and we look forward to seeing them put to use. Perhaps it will be in something like the micron-precision lathe we featured recently.

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Needling Your Projects: 3D Printed PCB Probing Jig Uses Accupuncture Needles

Trying to probe a modern electronic circuit with tiny SMD components, without letting the magic smoke escape in the process, can be quite a challenge. Especially since we hackers have not yet developed the number of appendages required to hold 3 different probes in place while operating both an oscilloscope and a computer. [Giuseppe Finizia] solved this problem with a 3D printed PCB probing jig that uses acupuncture needles.

As part of [Giuseppe] day job as an engineer at an electronic forensics laboratory, he does technical investigations on seized devices, which involves quite a bit of probing. The jig consists of a base plate with slots in which PCB holders of various configurations slide to hold all shapes and sizes of PCBs. Around the circumference of the plate there are multiple positions for adjustable probing “cranes”, each of which hold an acupuncture needle that is crimped or soldered to a wire. Each needle holder has a bit of flex which allows it to maintain downward pressure for a positive connection.

Making one-off tools and jigs is arguably one of the best applications for 3D printing, of which this is a perfect example. You can of course point solder wires or use test hooks if you have something to grab onto, but for easily probing multiple point on any PCB, this looks like a damn good solution. If you’re trying to trace a single signal, a precision pantograph might be your friend, or you can add a foot switch to your oscilloscope for quickly checking a circuit by hand.

[Jonathon Oxer] from the YouTube channel SuperHouse did a very nice video on the jig and made some small modifications. Check out the video after the break.

Review: Ear Wax Cleaning Cameras As Cheap Microscopes, We Take A Closer Look

Those of us who trawl the world of cheap imported goods will most often stay in our own comfortable zones as we search for new items to amaze and entertain us. We’ll have listings of electronic goods or tools, and so perhaps miss out on the scores of other wonders that can be ours for only a few dollars and a week or two’s wait for postage.

Who knew sticky ears were such big business!
Who knew sticky ears were such big business!

Just occasionally though something will burst out of another of those zones and unexpectedly catch our eye, and we are sent down an entirely new avenue in the global online supermarket.

Thus it was that when a few weeks ago I was looking for an inspection camera I had a listing appear from the world of personal grooming products. It seems that aural hygiene is a big market, and among the many other products devoted to it is an entire category of ear wax removal tools equipped with cameras. These can get you up close and personal with your ear canal, presumably so you can have a satisfying scoop at any accumulated bodily goop. I have a ton of electronics-related uses for a cheap USB close-up camera so I bought one of these so I could — if you’ll excuse the expression — get a closer look.

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DIY Electrolysis Tank: Removing Rust While You Sleep

Anyone who’s done a bit of metalworking will know how quickly your stockpile will pick up a coating of rust with even just a bit of humidity. While welding requires only a bit of wire brushing at the joint areas, cleaning a large frame for paint is a completely different story. The projects [Make it Extreme] gets himself into tend to involve a lot of steel, so he built his own electrolysis tank for rust removal.

Electrolytic rust removal involves placing the piece of steel to be cleaned into an alkaline electrolyte solution (water and washing soda) with a sacrificial steel anode and connecting a low voltage DC supply over the two pieces. [Make it Extreme] started with an old plastic container, around which he built a very neat trolley frame. He obviously put some thought into how the tank will be cleaned, since it can be removed by unscrewing six bolts and removing the top part of the frame.

The high current, low voltage power supply that is required for the process was built using an old microwave transformer. The secondary coil is removed and replaced with coil of thick insulated wire, to convert it into a step down transformer. After the rewinding the transformer outputs about 13 VAC, which is then run through beefy bridge rectifier modules to get a DC current. A custom machined copper bolt terminal is mounted through the side of the tank to attach the sacrificial anode plate to the positive lead of the power supply, while the negative lead is clamped to the rusty steel to be cleaned.

[Make it Extreme]’s projects never get old, with everything from rideable tank tracks to rotary electric guns. Check out the video after the break to see the build and an impressive demo. Continue reading “DIY Electrolysis Tank: Removing Rust While You Sleep”

3D-Printed Magazines Tame The SMD Tape Beast

Chances are pretty good that you’ve got a box or a bin somewhere in your shop with coils of SMD component tapes in it. If you’re lucky, the coils are somewhat contained in their conductive Mylar bags; if you’re more like us, the tapes are flopping around loose in an attempt to seemingly tie themselves together. In either case, these 3D-printed SMD magazines will bring a little order to the chaos, and make board assembly a little bit easier.

When we saw [Robin Reiter]’s build, we thought these would be cassettes for some sort of pick-and-place machine. But while they certainly look like they could be adapted to an automated PnP setup, [Robin]’s main goal was to provide organized storage for loose tapes. Each magazine has a circular reservoir to hold the coiled tape, with an exit slot at the front and a wedge that directs the cover tape in the opposite direction. This removes the cover tape to expose the components, clears it away from the pickup area, and as a bonus, allows the component tape to be advanced just by pulling back on the cover. Each magazine has a spring-loaded latch that clips onto a base that looks a bit like a DIN-rail; the weighted base holds several magazines and makes it easy to set up a manual pick-and-place session. The video below shows all the details.

For certain personality types, this really scratches an itch. We love the modular design, and the organization that these would bring to our shop would really help clean things up a bit. And if [Robin] were ever to take this design to the next level, adding something like this could be useful.

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