RC Car Repair With Beer Can Solder Stencil

June 12, 2022 by Sven Gregori 24 Comments

Sometimes it might seem as if your electronics are just jinxed. For [Niva_v_kopirce] it was the control board of his nephew’s RC car that kept frying the transistors. In situations like this, you can either throw it in the bin, invest your time in troubleshooting, hoping to find the error and try to fix it then, or get creative. He chose the latter, and designed and etched a replacement board.

Of course, etching your own PCB isn’t that noteworthy for the average Hackaday reader, although [Niva_v_kopirce] did go the extra mile and added purple solder mask to it, turning the stylishness definitely up to 11. This is also where it gets interesting, when you think of the solder mask as complementary layer for a solder paste stencil. Growing tired of manually applying solder paste, he thought to give a DIY stencil a try this time — using a beer can.

After cutting the can open and flattening it, along with some sanding, he transferred the cutouts from the solder mask onto it, and started etching holes in it. While the result may not be exactly precise, it did the job, especially for a homemade built.

Despite their convenience, stencils are still a rather exotic addition for hobbyists as they rarely pay off for a one-off project with limited SMD component usage. But maybe this was a new inspiration for you now. And if etching metal is outside your comfort zone, cutting plastic can be an alternative, as well as 3d printing.

Automate Parts Kitting With This Innovative SMD Tape Slicer

June 7, 2022 by Dan Maloney 5 Comments

Nobody likes a tedious manual job prone to repetitive stress injury, and such tasks rightly inspire an automated solution. This automatic SMD tape cutter is a good example of automating such a chore, while leaving plenty of room for further development.

We’re used to seeing such tactical automation projects from [Mr Innovative], each of which centers on an oddly specific task. In this case, the task involves cutting a strip containing a specific number of SMD resistors from a reel, perhaps for assembling kits of parts. The mechanism is simple: a stepper motor with a rubber friction wheel to drive the tape, and a nasty-looking guillotine to cut the tape. The cutter is particularly interesting, using as it does a short length of linear bearing to carry a holder for a razor blade that’s mounted perpendicular to the SMD tape. The holder is mounted to a small motor via a crank, and when the proper number of parts have been fed out, the motor rotates one revolution, driving the angled blade quickly down and then back up. This results in a shearing cut rather than the clipping action seen in this automated wire cutter, also by [Mr Innovative].

Curiously, there seems to be no feedback mechanism to actually measure how many resistors have been dispensed. We assume [Mr Innovative] is just counting steps, but it seems easy enough to integrate a photosensor to count the number of drive sprocket holes in the tape. It also seems like a few simple changes would allow this machine to accommodate SMD tapes of different sizes, making it generally useful for SMD kitting. It’s still pretty cool as a tactical project, though, and does a great job inspiring future improvements.

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A wood-and-plastic jig to make dovetail joints

3D Printed Template Makes Perfect Dovetail Joints

June 3, 2022 by Robin Kearey 14 Comments

Dovetail joints on a piece of furniture are one of those features that make it say “master carpenter” rather than “IKEA”. Traditional hand-made dovetails require accurate measurements and even more accurate sawing and chiseling, skills that may take years to develop. A slightly less artisanal method is to use a router and a dovetail template; the router makes perfectly straight cuts while the template makes sure it goes only where it needs to go.

If you haven’t got one of those templates yet, check out [Guy Perez]’s design for an adjustable dovetail template that’s easy to produce with a 3D printer. It consists of ten separate pieces mounted on a T-rail, which enables them to slide sideways and thereby generate pins and tails of varying widths. The T-rail is mounted on a wooden body with an integrated clamp to hold the target piece, as well as an endstop to provide a reference for all measurements.

As you can see in the video embedded below, the resulting jig is easy to use and should result in near-perfect dovetails each time. [Guy] made the CAD files available as well as detailed instructions on their design, so you can easily adjust them if you need pieces with a different tail angle or want to use thicker wood.

While this jig will make cutting ordinary dovetail joints a lot easier, you can still show off your manual skills by making an impossible mallet. Want to join metal bits instead? Check out this cute little dovetail cube.

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A Rotocasting Machine Sized For The Home Shop

June 3, 2022 by Dan Maloney 5 Comments

If you’ve ever wondered how large, hollow plastic structures like tanks and drums are formed, you’re in luck: [Andy] not only fills us in on the details of rotational casting and molding, but he also built this sweet little rotational casting machine to help him with his DIY projects.

Granted, [Andy]’s build won’t be making anything too large, like a car fuel tank or a kayak. Not only is it sized more for smallish parts, but those structures are generally made with the related process of rotational molding. Both processes use an enclosed multipart mold that’s partially filled with plastic resin, and then rotate the mold around two axes to distribute a thin layer of resin around the inside of the mold. The difference is that roto-molding uses a thermoplastic resin, whereas roto-casting uses resins like polyurethane and silicone that set at room temperature.

The machine looks simple, but only because he took great pains to optimize it. The videos below cover the build in detail — feel free to skip to the 11:38 mark of the second video if you just want to see it in action. Though you’ll be missing some juicy tidbits, like welding a perfect 90° joint in square tubing. There’s also the custom tool [Andy] built to splice the beaded chain he used to drive the spinning of the mold, which was pure genius.

Using the machine and a complex nine-piece mold, [Andy] was able to create remarkably detailed tires for RC cars from polyurethane resin. We’d love to see what else this rig is good for — almost as much as we want to see details on how the mold was made. We’ve seen other rotational casting machines before, but this one takes the cake for fit and finish.

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A frosted glass disk with geometrical markers

Using A Laser Cutter To Replicate An Optical Comparator Screen

May 30, 2022 by Robin Kearey 13 Comments

Precision instruments often contain specialized components that are essential to their function, but nearly impossible to replace if they fail. [Andre] had just such a problem with an optical comparator, which is an instrument typically used in machine shops to help check the tolerances of a finished part. It does this by projecting a magnified picture of an object onto a glass screen with markings showing angles and distances.

In the old comparator [Andre] bought on eBay, the markings on the glass had faded to such a degree that the instrument was almost unusable. So he contacted [James] over at Clough42, who was able to create a near-perfect replacement screen by using a laser cutter, as shown in the video embedded below.

The first step was to replicate the screen’s markings in a CAD program. [James] explains the process in Fusion 360, demonstrating how you can generate all the different scales nearly automatically through the proper use of constraints, variables and patterns. He then transferred the drawing to Lightburn, which drives the laser cutter and etches the markings into a sheet of glass covered with CerMark, a marking solution that turns a deep black when heated by a laser.

After etching, the final step was to apply frosting to the glass to turn it into a projection screen. While there are several ways to achieve this, [James] went for a simple spray-based method that gave surprisingly good results. It took a few experiments to find out that etching the markings on the back of the glass and applying the frosting on that side as well gave the best combination of sharpness and durability.

[James]’s project shows that even delicate instruments with custom glass components can be repaired, if you just have the right tools. A similar strategy might also work for creating custom scales for analog meters, or even old radio dials. If you’re not familiar with laser cutters, have a look at our experiments with an Ortur model. Thanks for the tip, [poiuyt]!

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Adjustable Workholding For Honeycomb Tables, With A Bit Of DIY

May 29, 2022 by Donald Papp 6 Comments

Honeycomb tables are often found on laser cutters, where they provide a way for work material to be laid flat while not interfering with things like airflow. This leads to a cleaner laser cut and a nicer finish, but if one’s work depends on precise positioning and placement, they leave something to be desired because there’s no good way to attach rails, jigs, or anything of the sort in an easy and stable fashion.

The solution [Ed] found for this was to make himself some adjustable offset stops designed to fit into his laser cutter’s honeycomb table. Each consists of a laser-cut disc of wood, which is screwed off-center into an acetal “plug” sized to fit into the vertical gaps in the honeycomb table. This allows each disc to be rotated to fine-tune positioning. With the help of some T-shaped pegs that are also sized to fit into the honeycomb table, [Ed] has all he needs to fix something like a workpiece or jig into a particular and repeatable position.

The whole thing depends on a friction fit, so the sizing of the plug needs to match a particular honeycomb table’s construction. We think this makes it a good match for 3D printing, as one can measure and print plugs (perhaps employing the Goldilocks approach) that fit with just the right amount of snug.

Honeycomb tables are fantastic for laser cutting, but if you find yourself in a pinch for a replacement, an old radiator can make a pretty decent stand-in.

Toothbrush Goes From Mouth-Whitening To Room-Brightening

May 27, 2022 by Kristina Panos 18 Comments

Some of the hacks we see make us wonder why they aren’t already a commercial product, and this electric toothbrush turned rechargeable flashlight is one of them. Sure, these things exist, but we haven’t seen one with a dedicated charging stand. They usually just take micro USB or whatever, so it’s on you to remember to plug it in. How great would it be to have a fully-charged flashlight always at the ready, especially one in a position to illuminate the room? Although [wannabemadsci] makes it look easy, this conversion took quite a bit of doing.

Perhaps the most amazing part is that [wannabemadsci] found a halfway decent flashlight at the dollar store. Better than average, this thing has a main light, a side light, and takes 3xAAs instead of a couple of AAAs. The only issue is that the toothbrush batteries don’t quite put out enough voltage for the flashlight’s LED, so [wannabemadsci] used a booster board.

Of course, there’s a lot more to this hack than sawing off the USB connector from the boost converter so it fits. The toothbrush handle had to be modified to accept the flashlight guts, and the threads relocated from the flashlight. Since the battery charge indicator shines through the momentary button on the toothbrush, [wannabemadsci] wanted to reuse it, but it required a small board that converts it to a latching push button. Finally, the flashlight bezel had to be painted white. Paint is such an easy thing to do, and this detail makes all the difference in how professional this looks.

There’s a lot you can do with a functioning electric toothbrush as your base, like brute-forcing the pins of a lock with vibration.