More LEDs Means Faster Print Times For 3D Printer, But There’s A Catch

[Jan Mrázek] is no stranger at all to home-grown improvements with his Elegoo Mars SLA 3D printer, and there is a lot going on in his experimental multi-LED upgrade which even involved casting his own lens array. In the end it did speed up his prints by a factor of three to four, though he cooked an LCD to failure in the process. Still, it was a fun project done during a COVID-19 lockdown; as usual there is a lot to learn from [Jan]’s experiences but the mod is not something he necessarily recommends people do for themselves.

[Jan] started by wondering whether better print quality and performance could be obtained by improving the printer’s UV light source. The stock printer uses a single large UV LED nestled into a reflector, but [Jan] decided to try making a more precise source of UV, aiming to make the UV rays as parallel as possible.

Custom LED array molded in clear epoxy.

To do this, he took a two-pronged approach. One was to replace the single large UV LED with a 4×7 array of emitters plus heat sink and fans. The other was to make a matching array of custom lenses to get the UV rays as parallel as possible.

Casting one’s own lens array out of clear epoxy was a lot of work and had mixed results, but again, it was a lockdown project and the usual “is-this-really-worth-it” rules were relaxed. In short, casting a single custom lens out of clear epoxy worked shockingly well, but when [Jan] scaled it up to casting a whole 4×7 array of them, results were mixed. Mold deformation and artifacts caused by the areas between individual lenses robbed the end result of much of its promise.

More success was had with the array of UV emitters, which enabled faster curing thanks to higher power, but the heat needs to be managed. The stock emitter of the printer is about 30 W, and [Jan] was running his new array at 240 W. This meant a blazing fast one second exposure time per layer, but the heat generated by the new lighting was higher than anticipated. After only ten hours the LCD failed, probably at least in part due to the heat. [Jan] halved the power of the array down to 120 W and added an extra fan, which appears to have done the trick. Exposure time is two to three seconds per layer, and it’s up to 150 hours of printing without problems.

Again, it’s not a process [Jan] necessarily recommends to others (and he definitely recommends buying lenses if at all possible instead of casting them) but as usual there is a lot to learn from his frank sharing of results, both good and bad. We’ve seen 3D-printed lenses as well as adding WiFi connectivity to one of these hobbyist printers, and it’s great to see the spirit of hacking alive and well when it comes to these devices.

Improved Flexible Build Plate For SLA Is Ready To Rock

The Elegoo Mars is an affordable SLA (resin-based) 3D printer, and there are probably few that have seen more mods and experimentation than [Jan Mrázek]’s machine. The final design of his DIY flexible build plate is a refinement of his original proof of concept, which proved a flexible build platform can be every bit as useful on an SLA printer as it is for FDM; instead of chiseling parts off a rigid build platform, simply pop the flexible steel sheet off the magnetic base and flex it slightly for a much easier part removal process. His original design worked, but had a few rough edges that have since been ironed out.

[Jan]’s magnetic build platform.
We love how [Jan] walks through all of the design elements and explains what worked and what didn’t. For example, originally he used a galvanized steel sheet which was easy enough to work with, but ended up not being a viable choice because once it’s bent, it stays bent. Spring steel is a much better material for a flexible build platform, but is harder for a hobbyist to cut.

Fortunately, it’s a simple job for any metal fabrication shop and [Jan] got a variety of thicknesses cut very cheaply. It turns out that the sweet spot is 0.3 mm (although 0.2 mm is a better choice for particularly fragile parts.) [Jan] also suggests cutting the sheet a few millimeters larger than the build platform; it’s much easier to peel the sheet off the magnetic base when one can get a fingertip under an edge, after all.

The magnetic base that the steel sheet sticks to is very simple: [Jan] converted a stock build platform by mounting an array of 20 x 20 x 1 mm magnets with 3M adhesive mounting tape. He was worried that resin might seep in between the magnets and cause a problem, perhaps even interfering with the adhesive; but so far it seems to be working very well. Resin is viscous enough that it never penetrates far into the gaps, and no effect on the adhesive has been observed so far.

Watch how easily parts are removed in the short video embedded below, in which [Jan] demonstrates his latest platform design.

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Put That New Resin Printer To Work Making PCBs

With all the cool and useful parts you can whip up (relatively) quickly on a 3D printer, it’s a shame you can’t just print a PCB. Sure, ordering a PCB is quick, easy, and cheap, but being able to print one-offs would peg the needle on the instant gratification meter.

[Peter Liwyj] may just have come up with a method to do exactly that. His Instructables post goes into great detail about his method, which uses an Elegoo Mars resin printer and a couple of neat tricks. First, a properly cleaned board is placed copper-side down onto a blob of SLA resin sitting on the print bed. He tricks the printer into thinking the platform is all the way down for the first layer by interrupting the photosensor used to detect home. He lets the printer go through one layer of an STL file that contains his design, which polymerizes a thin layer of plastic onto the copper. The excess resin is wiped gently away and the board goes straight into a ferric chloride etching bath. The video below shows the whole process.

As simple as it sounds, it looks like it works really well. And [Peter] didn’t just stumble onto this method; he approached it systematically and found what works best. His tips incude using electrical tape as a spacer to lift the copper off the print surface slightly, cleaning the board with Scotchbrite rather than sandpaper, and not curing the resin after printing. His toolchain is a bit uncoventional — he used SketchUp to create the traces and exported the STL. But there are ways to convert Gerbers to STLs, so your favorite EDA package can probably fit in to the process too.

Don’t have a resin printer? Don’t worry — FDM printers can work too.

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Sunshine In A Bag

Ultraviolet (UV) curing lamps are crucial if you have a resin 3D printer or work with UV adhesives. Some folks line an old Amazon shipping box with foil and drop a spotlight somewhere inside. Other folks toss their work under the all-natural light source, Sol. Both options have portability and reliability problems, but [AudreyObscura] has it covered with a reflective mat lined with UV strip lights. This HackadayPrize2020 finalist exemplifies the ideal that good ideas are often simple, and this has a remarkably short bill of materials.

Foil bubble insulation is the medium because it provides structure and reflectivity, but it doesn’t cooperate with the LED strip’s adhesive. [AudreyObscura] demonstrates that masking tape as an interfacing layer makes everyone play nicely. A fine example of an experienced maker, their design covers bundling wires and insulating connections to keep everything tidy and isolated. With different arrangements, this can form a tunnel lit from above, a chimney lit from the walls, or you can drape it over some scaffolding.

If you need something a little less portable for your own shop you might consider a mirror-filled chamber. One nice touch to add is a turntable to help make sure the entire part is cured without any missing areas.

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Friendly Fiberglassing: Can Hide Glue Replace Epoxy?

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.

Printing, Plating, And Baking Makes DIY Microlattices Possible

To be honest, we originally considered throwing [Zachary Tong]’s experiments with ultralight metallic microlattices into the “Fail of the Week” bucket. But after watching the video below for a second time, it’s just not fair to call this a fail, so maybe we’ll come up with a new category — “Qualified Success of the Week”, perhaps?

[Zachary]’s foray into the strange world of microlattices began when he happened upon a 2011 paper on the subject in Science. By using a special photocurable resin, the researchers were able to use light shining through a mask with fine holes to create a plastic lattice, which was then plated with nickel using the electroless process, similar to the first half of the electroless nickel immersion gold (ENIG) process used for PCBs. After removing the resin with a concentrated base solution, the resulting microlattice is strong, stiff, and incredibly light.

Lacking access to the advanced materials and methods originally used, [Zachary] did the best he could with what he had. An SLA printer with off-the-shelf resin was used to print the skeleton using the same algorithms used in the original paper. Those actually turned out pretty decent, but rather than electroless plating, he had to go with standard electroplating after a coat of graphite paint. The plated skeletons looked great — until he tried to dissolve the resin. When chemical approaches failed, into the oven went the plated prints. Sadly, it turns out that the polymers in the resin expand when heated, which blew the plating apart. A skeleton in PLA printed on an FDM printer fared little better; when heated to drive out the plastic, it became clear that the tortuous interior of the lattice didn’t plate very well.

From aerogels to graphene, we love these DIY explorations of new and exotic materials, so hats off to [Zachary] for giving it a try in the first place.

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Denim Sunglasses Frames Use A Wicked Set Of Jigs

An obligatory “Future’s so bright I gotta wear… denim” joke is the only way to kick off this article. Sorry!

Now that that’s out of the way, how would you turn your own blue jeans into sunglasses? Well you wouldn’t, unless you’ve built an intricate jig for assembling sunglasses frames like [Mosevic] has done. Boiled down, this is like making parts out of carbon fiber, except you swap in denim for the carbon fiber. Several layers of blue jean material are layered in a mold and impregnated with resin. Once hardened, parts can be milled or laser cut from this stock and then assembled into the frames all of the hipsters are after.

For us its the assembly jig that’s so interesting to see. [Mosevic] shared it in an unlisted video of an update to the Kickstarter campaign which ran at the end of 2019. The jig is used to align machined parts into stack ups that include brass reinforcement and pins to align layers, as well as the joining for the three parts of the frame via the metal hinges. Most of the jig is made from machined plywood. The plates that hold the three parts of the frame, the “frame front” and the two “temples” in eyeglass parlance, are interchangeable so that the same jig can be used to assemble several variants of the frame design. The most notable non-plywood part of the jig are two metal clamps that hold the hinge into the frame front as the glue dries, holding a couple of tiny chunks of denim/resin block in place.

Here you can see the jig with all clamps fully closed. There is not an insignificant amount of time just getting the parts into this jig. But parts still need quite a bit of cleanup after this process to sand, shape, and polish all edges and surfaces of the frames. And of course you have to figure in the time it took to make the parts that went into the jig in the first place. The finished frames are gorgeous, but we have a lot more respect having seen what it takes to pull it off.

Now if you like your glasses like George Washington liked his false teeth, here’s how you can pull a set of shades out of your woodshop.

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