epoxy

82 Articles

LED Layer Makes Plywood Glow

May 14, 2025 by 4 Comments

Plywood is an interesting material: made up of many layers of thin wood plys, it can be built up into elegantly curved shapes. Do you need to limit it to just wood, though? [Zach of All Trades] has proved you do not, when he embedded a light guide, LEDs, microcontrollers and touch sensors into a quarter inch (about six millimeter) plywood layup in the video embedded below.

He’s using custom flexible PCBs, each hosting upto 3 LEDs and the low-cost PY32 microcontroller. The PY32 drives the RGB LEDs and handles capacitive touch sensing within the layup. In the video, he goes through his failed prototypes and what he learned: use epoxy, not wood glue, and while clear PET might be nice and bendy, acrylic is going to hold together better and cuts easier with a CO2 laser. Continue reading “LED Layer Makes Plywood Glow” →

Laser-Cut Metal Endoskeleton Beefs Up 3D Prints

January 24, 2025 by 24 Comments

There are limits to what you can do with an FDM printer to make your parts stronger. It really comes down to adding more plastic, like increasing wall thickness or boosting up the infill percentage. Other than that, redesigning the part to put more material where the part is most likely to fail is about the only other thing you can do. Unless, of course, you have access to a fiber laser cutter that can make internal metal supports for your prints.

As [Paul] explains it, this project stemmed from an unfortunate episode where a printed monitor stand failed, sending the LCD panel to its doom. He had taken care to reinforce that part by filling it with fiberglass resin, but to no avail. Unwilling to risk a repeat with a new tablet holder, he decided to test several alternative methods for reinforcing parts. Using a 100 W fiber laser cutter, he cut different internal supports from 0.2 mm steel shim stock. In one case he simply sandwiched the support between two half-thickness brackets, while in another he embedded the steel right into the print. He also made two parts that were filled with epoxy resin, one with a steel support embedded and one without.

The test setup was very simple, just a crane scale to measure the force exerted by pulling down on the part with his foot; crude, but effective. Every reinforced part performed better than a plain printed part with no reinforcement, but the clear winner was the epoxy-filled part with a solid-metal insert. Honestly, we were surprised at how much benefit such a thin piece of metal offered, even when it was directly embedded into the print during a pause.

Not everyone has access to a fiber laser cutter, of course, so this method might not be for everyone. In that case, you might want to check out other ways to beef up your prints, including just splitting them in two.

Continue reading “Laser-Cut Metal Endoskeleton Beefs Up 3D Prints” →

DIY Air Bearings, No Machining Required

October 20, 2024 by 26 Comments

Seeing a heavy load slide around on nearly frictionless air bearings is pretty cool; it’s a little like how the puck levitates on an air hockey table. Commercial air bearings are available, of course, but when you can build these open-source air bearings, why bother buying?

One of the nice things about [Diffraction Limited]’s design is that these bearings can be built using only simple tools. No machining is needed past what can be easily accomplished with a hand drill, thanks to some clever 3D-printed jigs that allow you to drill holes with precision into stainless steel discs you can buy on the cheap. An extremely flat surface is added to the underside of these discs thanks to another jig, some JB Weld epoxy, and a sheet of float glass to serve as an ultra-flat reference. Yet more jigs make it easy to scribe air channels into the flat surface and connect them to the air holes through a bit of plaster of Paris, which acts as a flow restriction. The video below shows the whole process and a demo of the bearings in action.

[Diffraction Limited] mentions a few applications for these air bearings, but the one that interests us most is their potential use in linear bearings; a big CNC cutter using these air bearings would be pretty cool. We seen similar budget-friendly DIY air bearings before, including a set made from used graphite EDM electrodes.

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Curing CRT Cataracts Freshens Up Retro Roundy TVs

September 29, 2024 by 12 Comments

It’s been a long time since the family TV has had a CRT in it, and even longer since that it was using what was basically an overgrown oscilloscope tube. But “roundies” were once a thing, and even back in the early 80s you’d still find them in living rooms on TV repair calls, usually sporting a characteristic and unsightly bullseye discoloration.

Fast-forward a few decades, and roundy TVs have become collectible enough that curing their CRT cataracts is necessary for restorationists like [shango066], a skill he demonstrates in the video below. The defect comes from the composite construction of CRTs — a safety feature added by television manufacturers wisely concerned with the safety aspects of putting a particle accelerator with the twin hazards of high vacuum and high voltage in the family home. The phosphor-covered face of the tube was covered by a secondary glass cover, often tinted and frosted to improve the admittedly marginal viewing experience. This cover was often glued in place with an epoxy resin that eventually oxidized from the edges in, making the bullseye pattern.

The remedy for this problem? According to [shango066], it’s heat, and plenty of it. After liberating the tube from the remarkably clean TV chassis, he took advantage of a warm summer’s day and got the tube face cooking under a black plastic wrap. Once things were warmed up, more heat was added to really soften the glue; you can easily see the softening progress across the face of the tube in the video below. Once softened, gentle prying with wooden chopsticks completes the job of freeing the safety lens, also in remarkably good shape.

With the adhesive peeled off in an oddly satisfying manner, all that’s left is a thorough cleaning and gluing the lens back on with a little silicone sealant around the edges. We’d love to see the restored TV in operation, but that’s left to a promised future video. In the meantime, please enjoy a look at the retro necessities TV owners depended on in the good old days, which really weren’t all that good when you get down to it.

Continue reading “Curing CRT Cataracts Freshens Up Retro Roundy TVs” →

Steel Reinforcement Toughens Cracked Vintage Knobs

September 21, 2024 by 8 Comments

Nothing can ruin a restoration project faster than broken knobs. Sure, that old “boat anchor” ham rig will work just fine with some modern knobs, but few and far between are the vintage electronics buffs that will settle for such aesthetic affrontery. But with new old stock knobs commanding dear prices, what’s the budget-conscious restorationist to do? Why, fix the cracked knobs yourself, of course.

At least that’s what [Level UP EE Lab] tried with his vintage Heahkit DX60 ham transmitter, with pretty impressive results. The knobs on this early-60s radio had all cracked thanks to years of over-tightening the set screws. To strengthen the knobs, he found some shaft collars with a 1/4″ inside diameter and an appropriate set screw. The backside of the knob was milled out to make room for the insert, which was then glued firmly in place with everyone’s go-to adhesive, JB Weld. [Level UP] chose the “Plastibonder” product, which turns out not to be an epoxy but rather a two-part urethane resin, which despite some initial difficulties flowed nicely around the shaft collar and filled the milled-out space inside the knob. The resin also flowed into the channels milled into the outside diameter of the shaft collars, which are intended to grip the hardened resin better and prevent future knob spinning.

It’s a pretty straightforward repair if a bit fussy, but the result is knobs that perfectly match the radio and still have the patina of 60-plus years of use. We’ll keep this technique in mind for our next restoration, or even just an everyday repair. Of course, for less demanding applications, there are always 3D printed knobs.

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Laser Fault Injection, Now With Optional Decapping

September 20, 2024 by 3 Comments

Whether the goal is reverse engineering, black hat exploitation, or just simple curiosity, getting inside the packages that protect integrated circuits has long been the Holy Grail of hacking. It isn’t easy, though; those inscrutable black epoxy blobs don’t give up their secrets easily, with most decapping methods being some combination of toxic and dangerous. Isn’t there something better than acid baths and spinning bits of tungsten carbide?

[Janne] over at Fraktal thinks so, and the answer he came up with is laser decapping. Specifically, this is an extension of the laser fault injection setup we recently covered, which uses a galvanometer-scanned IR laser to induce glitches in decapped microcontrollers to get past whatever security may be baked into the silicon. The current article continues that work and begins with a long and thorough review of various IC packaging technologies, including the important anatomical differences. There’s also a great review of the pros and cons of many decapping methods, covering everything from the chemical decomposition of epoxy resins to thermal methods. That’s followed by specific instructions on using the LFI rig to gradually ablate the epoxy and expose the die, which is then ready to reveal its secrets.

The benefit of leveraging the LFI rig for decapping is obvious — it’s an all-in-one tool for gaining access and executing fault injection. The usual caveats apply, of course, especially concerning safety; you’ll obviously want to avoid breathing the vaporized epoxy and remember that lasers and retinas don’t mix. But with due diligence, having a single low-cost tool to explore the innards of chips seems like a big win to us.

Repairing A Gear With A Candle (and Some Epoxy)

March 19, 2024 by 19 Comments

You have a broken gear you need to fix, but there’s no equivalent part available. That’s the issue [Well Done Tips] faced with a plastic gear from a lawnmower. While we’d be tempted to scan the gear, repair the damage in CAD and then 3D print a new one, we enjoyed hearing about his low-tech solution. In addition to the write up, there’s a video showing the process you can watch below.

The idea is pretty simple. Using a piece of pipe and melted candle wax, he prepared a mold of an undamaged section of the gear. Then he cast epoxy resin in place to recreate the missing pieces. There are a few tricks, like putting holes in the remaining part of the gear so the epoxy flows into the existing part. Depending on the gear’s purpose and original material, you might be able to just use it as-is. However, you could also use the repaired gear as a template to create another mold and then cast an entire gear from resin or even metal if you can cast metal.

You can argue whether resin is better or worse than PLA, but of course, it depends on the kind of resin—photopolymers are different from epoxy resins you’d use for this sort of thing. If you think you might like to make your new gear out of aluminum, you might find some inspiration in a previous post.

Continue reading “Repairing A Gear With A Candle (and Some Epoxy)” →