Magnetocuring: Curing Epoxy With A Magnetic Field

December 30, 2020 by Maya Posch 20 Comments

Who doesn’t love epoxy? Epoxy resins, also known as polyepoxides, are an essential adhesive in many applications, both industrially and at smaller scales. Many polyepoxides however require the application of heat (around 150 °C for most types) in order to cure (harden), which can be complicated when the resin is applied to or inside layers of temperature sensitive materials. Now researchers at Nanyang Technological University (NTU) in Singapore have found a way to heat up resins using an alternating magnetic field (PDF), so-called magnetocuring.

As detailed in the research article by R. Chaudhary et al., they used commercially available epoxy resin and added nano particles of a Mn_xZn_1-xFe₂O₄ alloy. This mixture was exposed to an alternating magnetic field to induce currents in the nano particles and subsequently produce heat that served to raise the temperature of the surrounding resin to about 160 °C in five minutes, allowing the resin to cure. There is no risk of overheating, as the nano particles are engineered to reach their Curie temperature, at which point the magnetic field no longer affects them. The exact Curie temperature was tweaked by changing the amount of manganese and zinc in the alloy.

After trying out a number of different alloy formulations, they settled on Mn_0.7Zn_0.3Fe₂O₄ as the optimal formulation at which no resin scorching occurred. As with all research it’s hard to tell when (and if) it will make it into commercial applications, but if this type of technology works out we could soon be gluing parts together using epoxy resin and an EM field instead of fumbling with the joys of two-component epoxy.

(Thanks, Qes)

Friendly Fiberglassing: Can Hide Glue Replace Epoxy?

September 11, 2020 by Brian McEvoy 40 Comments

Hide glue has been around for thousands of years, and some of it is holding wood pieces three thousand years after application. It is made from animal protein, so vegetarians may want to stick to the petroleum-based adhesives. [Surjan Singh] wanted to see if its longevity made it a contender with modern epoxy by casting a couple of fiberglass car parts with the competing glues. In short, it doesn’t hold up in this situation, but it is not without merit.

Musical instrument makers and antique restorers still buy and use hide glue, but you would never expose it to heat or moisture. To its credit, hide glue doesn’t require a ventilator. All you need is boiling water and a popsicle stick, and you are in business. [Surjan] writes his findings like a narrative rather than steps, so his adventures are a delight to read. He found that a car part made with fiberglass and epoxy will withstand the weather better than the alternative because heat and humidity will soften hide glue. His Saab 96 isn’t the right application, but since it is nearly as strong as epoxy once set, you could make other fabric shapes, like a flannel nightstand or a lace coffee table, and you could shape them in the living room without toxifying yourself

No matter how you want to work with glues and substrates, Bil Herd has you covered, and here is an excellent tip for a cheap degassing setup.

Using Additives For Better Performing Epoxy

March 17, 2020 by Zoe Skyforest 13 Comments

Epoxy resins are an important material in many fields. Used on their own as an adhesive, used as a coating, or used in concert with fiber materials to make composites, their high strength and light weight makes them useful in many applications. [Tech Ingredients] decided to explore how combining basic epoxy resin with various additives can make it perform better in different roles.

The video primarily concerns itself with explaining different common additives to epoxy resin mixtures, and how they impact its performance. Adding wood flour is a great way to thicken epoxy, allowing it to form a bead when joining two surfaces. Microbeads are great to add if you’re looking to create a sandable filler. Other additive like metal powders lend the mixture resistance to degradation from UV light, while adding dendritic copper creates a final product with high thermal conductivity.

The video does a great job of not only explaining the additives and their applications, but also shares a few handy tips on best workshop practices. Things like triple-gloving and observing proper mixing order can make a big difference to your workflow and lead to better results.

We’ve seen practical applications of epoxy mixes before – with epoxy granite being a particularly popular material. Video after the break.

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Making Flexible Overmolded Parts With Urethane Resin

July 19, 2019 by Zoe Skyforest 11 Comments

Resin casting videos have taken social media by storm of late. Everything from inlaid driftwood tables to fancy pens are getting the treatment. Pouring some nicely colored epoxy is straightforward enough, but it’s just the tip of the iceberg. [Eric Strebel] has some serious skills in resin casting, and has lately been working on some overmolded electroniics with urethane resin (Youtube link, embedded below).

The build starts with the creation of a silicone mold, using a 3D printed SLA master. The part in question is for a prototype medical device, and requires overmolding, in which a flexible PCB is covered in flexible urethane. Wooden pins are used to allow the flexible PCB to clip into the mold for accurate location, and a small shield is placed over the metal contacts of the PCB to avoid them being covered in silicone.

Initial tests are done with an empty mold to determine the correct material to use, before the actual parts are ready to produce. [Eric] takes great care with the final production, as any mistakes would waste the expensive prototype PCBs provided to him by the client. With the electronics placed in the mold, the resin is degassed and carefully injected, using a syringe to minimise the chance of any air bubbles. With some delicate cleanup by hand, the completed parts are ready for delivery.

It’s a process that covers the basics of overmolding for a prototype part, as well as showing off [Eric]’s skill at producing quality prototype parts. We’ve seen [Eric]’s work before, too – like his discussion of the value of cardboard in product design. Video after the break.

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These 3D Printed Supports Can Take Hard Use, Thanks To Resin Filling

September 29, 2018 by Donald Papp 16 Comments

Liquid two-part resins that cure into a solid are normally used for casting, and [Cuddleburrito] also found them useful to add strength and rigidity to 3D printed pillar supports. In this case, the supports are a frame for some arcade-style buttons, which must stand up to a lot of forceful mashing. Casting the part entirely out of a tough resin would require a mold, and it turns out that filling a 3D print with resin gets comparable benefits while making it easy to embed fastener hardware, if done right.

Cap design shows how the nut will be encased and the cap anchored even if the pillar is slightly underfilled with resin. The screw can be backed out after the resin cures.

Filling the inside of an object with some kind of epoxy or resin to reinforce it isn’t a new idea, but [Cuddleburrito] learned how a few small design considerations can lead to less messy and more successful results. The first is that resin can be poured with screws in place without any worry of trapping the screws in the resin, if done correctly. As long as only the threads of the screw are in the resin, they can be backed out after the resin has cured. Embedding nuts into the resin to act as fasteners becomes a much easier task when one can simply pour resin with both nut and screw in place, and remove the screw afterwards. A thin layer of a lubricant on the threads to act as a release may help, but [Cuddleburrito] didn’t seem to need any.

The second thing learned was that, for a pillar that needs a cap and embedded nut on both ends, it can be tricky to fill the object’s void with the perfect amount of required resin before capping it off. On [Cuddleburrito]’s first attempt, he underfilled and there wasn’t enough resin to capture the nut on the top lid of the pillar he was making. The way around this was to offset the nut on a riser, and design in either a witness hole or an overflow relief. A small drain hole or a safe area for runoff allows for filling things right up without an uncontrolled mess in the case of overfilling.

Something worth keeping in mind when experimenting in this area is that in general the faster a resin cures, the more it heats up in the process. It may be tempting to use something like 5 minute epoxy in a pinch, but the heat released from any nontrivial amount of it risks deforming a thin-walled 3D print in the process. For cases where resin would be overkill and the fasteners are small, don’t forget we covered the best ways to add fasteners directly to 3D printed parts.

Epoxy Fix For A Combusted PCB

September 26, 2018 by Dan Maloney 29 Comments

When the Magic Smoke is released, chances are pretty good that you’ve got some component-level diagnosis to do. It’s usually not that hard to find the faulty part, charred and crusty as it likely appears. In that case, some snips, a new non-crusty part, and a little solder are usually enough to get you back in business.

But what if the smoke came not from a component but from the PCB itself? [Happymacer] chanced upon this sorry situation in a power supply for an electric gate opener. Basking in the Australian sunshine for a few years, the opener started acting fussy at first, then not acting at all. Inspection of its innards revealed that some unlucky ants had shorted across line and neutral on the power supply board, which burned not only the traces but the FR4 of the board as well. Rather than replace the entire board, [Happymacer] carefully removed the carbonized (and therefore conductive) fiberglass and resin, leaving a gaping hole in the board. He fastened a patch for the hole from some epoxy glue; Araldite is the brand he used, but any two-part epoxy, like JB Weld, should work. One side of the hole was covered with tape and the epoxy was smeared into the hole, and after a week of curing and a little cleanup, it was ready for duty. The components were placed into freshly drilled holes, missing traces were replaced with wire, and it seems to be working fine.

This seems like a great tip to keep in mind for when catastrophe strikes your boards. There are more extreme ways to do it, of course, but perhaps none so flexible. After all, epoxy is versatile stuff.

Epoxy Embedded Electronic Art Running On Pyramid Power

September 2, 2018 by Steven Dufresne 25 Comments

We sometimes get our inspirations from art. When [kodera2t] saw some Japanese art of fish drawings embedded in clear epoxy he just had to make his own. But while skilled in electronics, he wasn’t skilled at drawing. We’d still call him an artist, though, after seeing what he came up with in his electronics embedded in crystal clear epoxy.

His first works of electronic art were a couple of transistors and some ICs, including an 80386, encased in epoxy. But then he realized that he wanted the electronics to do something interesting. However, once encased in epoxy, how do you keep the electronics powered forever?

He tried a solar cell charging a battery which then powered an LED but he didn’t like the idea of chemical batteries encased in epoxy for a long time.

He then switched to wireless power transmission with a receiving coil in the base of epoxy pyramids. For one of them, the coil powers a BLE board with an attached LED which he can control from his phone. And his latest contains an ESP32-PICO with an OLED display. The code allows him to upload new firmware over the air but on his Hackaday.io page, he shows the difference between code which can brick the ESP32 versus code which won’t. But don’t take our word for it. Check out the video below to see his artistry for yourself.

While embedding electronics in epoxy is new to [kodera2t], we’ve seen it a few times before. once in the form of an amplifier circuit done beautifully, dead bug style, and a more experimental attempt with a solar lantern.

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