More Microwave Metal Casting

April 16, 2024 by Dan Maloney 10 Comments

If you think you can’t do investment casting because you don’t have a safe place to melt metal, think again. Metal casting in the kitchen is possible, as demonstrated by this over-the-top bathroom hook repair using a microwave forge.

Now, just because it’s possible doesn’t mean it’s advisable. There are a lot better ways to fix something as mundane as a broken bathroom hook, as [Denny] readily admits in the video below. But he’s been at the whole kitchen forging thing since building his microwave oven forge, which uses a special but easily constructed ceramic heat chamber to hold a silicon carbide crucible. So casting a replacement hook from brass seemed like a nice exercise.

The casting process starts with a 3D-printed model of the missing peg, which gets accessories such as a pouring sprue and a thread-forming screw attached to it with cheese wax. This goes into a 3D-printed mold which is filled with a refractory investment mix of plaster and sand. The green mold is put in an air fryer to dry, then wrapped in aluminum foil to protect it while the PLA is baked out in the microwave. Scrap brass gets its turn in the microwave before being poured into the mold, which is sitting in [Denny]’s vacuum casting rig.

The whole thing is over in seconds, and the results are pretty impressive. The vacuum rig ensures metal fills the mold evenly without voids or gaps. The brass even fills in around the screw, leaving a perfect internal thread. A little polishing and the peg is ready for bathroom duty. Overly complicated? Perhaps, but [Denny] clearly benefits from the practice jobs like this offer, and the look is pretty cool too. Still, we’d probably want to do this in the garage rather than the kitchen.
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Hackaday Links: September 3, 2023

September 3, 2023 by Dan Maloney 16 Comments

Right-to-repair has been a hot-button topic lately, with everyone from consumers to farmers pretty much united behind the idea that owning an item should come with a plausible path to getting it fixed if it breaks, or more specifically, that you shouldn’t be subject to prosecution for trying to repair your widget. Not everyone likes right-to-repair, of course — plenty of big corporations want to keep you from getting up close and personal with their intellectual property. Strangely enough, their ranks are now apparently joined by the Church of Scientology, who through a media outfit in charge of the accumulated works of Church founder L. Ron Hubbard are arguing against exemptions to the Digital Millennium Copyright Act (DMCA) that make self-repair possible for certain classes of devices. They apparently want the exemption amended to not allow self-repair of any “software-powered devices that can only be purchased by someone with particular qualifications or training or that use software ‘governed by a license agreement negotiated and executed’ before purchase.

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Laser-Cut Solder Masks From Business Cards

April 9, 2021 by Bryan Cockfield 22 Comments

There are plenty of ways to make printed circuit boards at home but for some features it’s still best to go to a board shop. Those features continue to decrease in number, but not a lot of people can build things such as a four-layer board at home. Adding a solder mask might be one of those features for some, but if you happen to have a laser cutter and a few business cards sitting around then this process is within reach of the home builder too.

[Jeremy Cook] is lucky enough to have a laser cutter around, and he had an idea to use it to help improve his surface mount soldering process. By cutting the solder mask layer into a business card with the laser cutter, it can be held on top of a PCB and then used as a stencil to add the solder paste more easily than could otherwise be done. It dramatically decreases the amount of time spent on this part of the process, especially when multiple boards are involved since the stencil can be used multiple times.

While a laser cutter certainly isn’t a strict requirement, it certainly does help over something like an X-acto knife. [Jeremy] also notes that this process is sometimes done with transparency film or even Kapton, which we have seen a few times before as well.

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Knockoff Kapton Nearly Sinks DIY Flex PCB Project

January 10, 2021 by Donald Papp 16 Comments

[TinkersProjects] experimented with making their own flexible PCB for LED modules inside a special fixture, and the end result was at least serviceable despite some problems. It does seem as though the issues can be at least partially blamed on some knockoff Kapton tape, which is what [TinkersProjects] used as a backing material.

Incomplete etching on this DIY flexible PCB, but still salvageable.

The approach was simple: after buying some copper foil and wide Kapton tape, simply stick the foil onto the tape and use the toner transfer method to get a PCB pattern onto the copper. From there, the copper gets etched away in a chemical bath and the process is pretty much like any other DIY PCB. However, this is also where things started to go wonky.

Etching was going well, until [TinkersProjects] noticed that the copper was lifting away from the Kapton tape. Aborting the etching process left a messy board, but it was salvageable. But another problem was discovered during soldering, as the Kapton tape layer deformed from the heat, as if it were a piece of heat shrink. This really shouldn’t happen, and [TinkersProjects] began to suspect that the “Kapton” tape was a knockoff. Switching to known-good tape was an improvement, but the adhesive left a bit to be desired because traces could lift easily. Still, in the end the DIY flexible PCB worked, though the process had mixed results at best.

Flexible PCBs have been the backbone of nifty projects like this self-actuating PoV display, so it’s no surprise that a variety of DIY PCB methods are getting applied to it.

Slipping Sheets Map Multiple Bends In This Ingenious Flex Sensor

June 26, 2020 by Dan Maloney 23 Comments

When thoughts turn to measuring the degree to which something bends, it’s pretty likely that strain gauges or some kind of encoders on a linkage come to mind. Things could be much simpler in the world of flex measurement, though, if [Fereshteh Shahmiri] and [Paul H. Dietz]’s capacitive multi-bend flex sensor catches on.

This is one of those ideas that seems so obvious that you don’t know why it hasn’t been tried before. The basic idea is to leverage the geometry of layered materials that slip past each other when bent. Think of the way the pages of a hardbound book feather out when you open it, and you’ll get the idea. In the case of the ShArc (“Shift Arc”) sensor, the front and back covers of the book are flexible PCBs with a series of overlapping pads. Between these PCBs are a number of plain polyimide spacer strips. All the strips of the sensor are anchored at one end, and everything is held together with an elastic sleeve. As the ShArc is bent, the positions of the electrodes on the top and bottom layers shift relative to each other, changing the capacitance across them. From the capacitance measurements and the known position of each pad, a microcontroller can easily calculate the bend radius at each point and infer the curvature of the whole strip.

The video below shows how the ShArc works, as well as several applications for the technology. The obvious use as a flex sensor for the human hand is most impressive — it could vastly simplify [Will Cogley]’s biomimetic hand controller — but such sensors could be put to work in any system that bends. And as a bonus, it looks pretty simple to build one at home.

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Arduboy Goes Thin And Flexible For Portable Gaming

April 18, 2019 by Brian McEvoy 5 Comments

We all have a gaming system in our pocket or purse and some of us are probably reading on it right now. That pocket space is valuable so we have to budget what we keep in there and adding another gaming system is not in the cards, if it takes up too much space. [Kevin Bates] budgeted the smallest bit of pocket real estate for his full-size Arduboy clone, Arduflexboy. It is thin and conforms to his pocket because the custom PCB uses a flexible substrate and he has done away with the traditional tactile buttons.

Won’t a flexible system be hard to play? Yes. [Kevin] said it himself, and while we don’t disagree, a functional Arduboy on a flexible circuit makes up for practicality by being a neat manufacturing demonstration. This falls under the because-I-can category but the thought that went into it is also evident. All the components mount opposite the screen so it looks clean from the front and the components will not be subject to as much flexing and the inputs are in the same place as a traditional Arduboy.

cost = low, practicality = extremely low, customer service problems = high

~[Kevin Bates]

These flexible circuit boards use a polyimide substrate, the same stuff as Kapton tape, and ordering boards is getting cheaper so we can expect to see more of them popping up. Did we mention that we currently have a contest for flexible circuits? We have prizes that will make you sing, just for publishing your flex PCB concept.

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Flexible PCB Contest Round Up

April 15, 2019 by Dan Maloney 19 Comments

The 2019 Hackaday Prize, which was announced last week, is very much on everyone’s mind, so much so that we’ve already gotten a great response with a lot of really promising early entries. As much as we love that, the Prize isn’t the only show in town, and we’d be remiss to not call attention to our other ongoing contest: The Flexible PCB Contest.

The idea of the Flexible PCB Contest is simple: design something that needs a flexible PCB. That’s it. Whether it’s a wearable, a sensor, or a mechanism that needs to transmit power and control between two or more moving elements, if a flexible PCB solves a problem, we want to know about it.

We’ve teamed up with Digi-Key for this contest, and 60 winners will receive free fabrication of three copies of their flexible PCB design, manufactured through the expertise of OSH Park. And here’s the beauty part: all you need is an idea! No prototype is necessary. Just come up with an idea and let us know about it. Maybe you have a full schematic, or just a simple Fritzing project. Heck, even a block diagram will do. Whatever your idea is for a flexible PCB project, we want to see it.

To get the creative juices going, here’s a look at a few of the current entries