UV Resin Perfects 3D Print, But Not How You Think

January 4, 2022 by 18 Comments

At this point, everyone knows that the print quality you’ll get from even an entry level UV resin printer far exceeds what’s possible for filament-based fused deposition modeling (FDM) machines. But there’s a trade-off: for the money, you get way more build volume by going with FDM. So until the logistics of large-format resin printers gets worked out, folks looking to make things like replica prop helmets have no choice but to put considerable time into post-processing their prints to remove the obvious layer lines.

But thanks to this somewhat ironic trick demonstrated by [PropsNstuff], you can actually use UV resin to improve the finish quality of your FDM prints. The idea is to put a layer of resin over the layer lines and other imperfections of the 3D print, cure it with a handheld UV flashlight, and then sand it smooth. Essentially it’s like using resin in place of a body filler like Bondo, with the advantage here being that the resin cures in seconds.

The thick resin fills in tough spots quickly.

Now to be clear, this isn’t a new idea. Our very own [Donald Papp] investigated the process back in 2018, and [Thomas Sanladerer] covered the idea in a video of his own the following year. But the difference here is that [PropsNstuff] doesn’t just coat the whole print with resin, he takes a more methodical approach. Working in small sections, he targets areas that really need the high-build properties offered by this technique.

With the tough spots addressed, he then moves on to coating larger areas with resin. But this time, he mixes leftover resin from his SLA printer with talcum powder to make a mix that can be brushed on without running everywhere. It takes a few thin coats, but with this mix, he’s able to build up large swaths of the print without losing any surface detail.

Is it still a hassle? Absolutely. But the final result does look spectacular, so until we figure out how to build the replicators from Star Trek, it looks like we’ll have to make up for our technological shortcomings with the application of a little elbow grease.

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Potassium ferrioxalate crystal

Growing Spectacular Gem-Like Crystals From Rust And Simple Ingredients

January 4, 2022 by 33 Comments

When we talk about crystals around here, we’re generally talking about the quartz variety used to make oscillators more stable, or perhaps ruby crystals used to make a laser. We hardly ever talk about homegrown crystals, though, and that’s a shame once you see how easy it is to make beautiful crystals from scratch.

We’ve got to say that we’re impressed by the size and aesthetics of the potassium ferrioxalate crystals [Chase Lean] makes with this recipe, and Zelda fans will no doubt appreciate their resemblance to green rupees. The process starts with rust, or ferric oxide, which can either be purchased or made. [Chase] chose to make his rust by soaking steel wool in a solution of saltwater and peroxide and heating the resulting sludge. A small amount of ferric oxide is added to a solution of oxalic acid, a commonly used cleaning and bleaching agent. Once the rust is dissolved, potassium carbonate is slowly added to the solution, turning it a bright green.

The rest of the process happens more or less naturally, as crystals begin to form in the saturated solution. And boy, did they grow — long, prismatic lime-green crystals, with a beautiful clarity and crisp edges and facets. The crystals don’t last long under light, though — they quickly lose their clarity and become a more opaque green.

[Chase]’s crystal-growing efforts have shown up here before, when he turned humble table salt into beautiful cubic crystals. We find the whole crystal-growing process fascinating, and we’re looking forward to more of this in the future.

Detail of an LED display made using ping-pong balls

Modular Design Enables Huge Ping-Pong Ball LED Displays

January 4, 2022 by 22 Comments

Ping-pong balls have many uses: apart from playing table tennis, they have been used for countless art projects, science experiments, and even to raise ships from the bottom of the ocean. As it turns out, they also come in handy as diffusers for LED pixels, allowing the construction of large-size displays without requiring large individual LEDs.

[david] designed an LED ping-pong ball display using 3D printed components, which allows for the construction of arbitrarily-large LED displays thanks to a strictly modular design. The basic unit is a small piece that holds a single LED module and has a cup-like structure for attaching a standard table tennis ball. Twenty-five of these basic units combine together into a panel that also contains wiring ducts. Finally, any number of these panels can be combined into a display, thanks to clips that give the structure rigidity in the out-of-plane direction.

A 3D-printed frame for making an LED display
A single panel holds 25 LEDs and comes with cable ducts. On the right is a clip for connecting multiple frames together.

Of course, simply mounting LED modules is not enough to create a display: the LEDs also need to be connected to power and data lines. [david] didn’t relish the thought of having to cut and strip 1,800 pieces of wire, and therefore devised a clever way of automating this process: he put a bunch of wires onto a piece of card stock and used a laser cutter to burn off the insulation at regular intervals. Then it was simply a matter of soldering these wires onto the LEDs and snipping off pieces along the data bus.

The finished panel is driven by a combination of a Teensy 3.2 to generate the data signals and a Raspberry Pi to process the images. You can see the rather impressive result in the video embedded below; if this inspires you to build your own, you’ll be happy to hear that the STL files and all code are available on [david]’s project page.

Massive LED displays are always fun to watch, and although this is not the first one to use ping-pong balls as diffusers, its modularity and open-source design makes this one perhaps the easiest to replicate. Assuming you have a good supplier of ping-pong balls, of course.

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What You Should Know Before Buying An Industrial Sewing Machine

January 4, 2022 by 48 Comments

I’ve been sewing off and on since I was a kid, and I really started to get into it about ten years ago. Even though I technically outgrew my little 3/4 size domestic machine pretty quickly, I kept using it because it always did whatever I asked it to. I even made my first backpack on it before deciding it was time for something bigger. Don’t ask me how I managed to not kill that machine, because I have no idea.

Left: a 3/4 size Janome 11706. Right: a full-size Singer Heavy Duty 4452.

Last year, I got a so-called heavy duty Singer that claims to have 50% more power than a standard domestic machine. This bad boy will make purses and backpacks with ease, I thought. And it does. Well, most of the time.

I found its limits when I tried to make a bag out of thick upholstery material. And honestly, when it comes down to finishing most bags — sewing the thickest and most difficult seams — the machine often lifts up from the table on the end opposite the needle.

What I really need is an industrial sewing machine. Not to replace the Singer at all, but to complement it. I can totally justify this purchase. Let me tell you why.

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The Cucumber House That LEGO Built

January 4, 2022 by 19 Comments

How far are you prepared to go to build a novelty seasonal ornament? Maybe a gingerbread house, or perhaps a bit of 3D printed glitter to hang on your Christmas tree. For [The Brick Wall], none of this was enough. Instead what was needed was a complete LEGO automated factory that builds a log cabin, from the unlikely raw material of cucumbers.

What has been created is the LEGO equivalent of a timber mill, with the various machines served by an overhead gantry crane. The cucumbers are trimmed to square, before being transferred to a saw which cuts out the notches for the interlocking corners. Another saw line chops the sections around door and windows to length, and finally the roof planks are cut in a vertical saw. The video below is reported as taking 83 days to complete from planning to filming, and 18 cucumbers to build the house. We’re not sure the cucumber will become a regular building material, but we salute the effort involved here.

Though this may be one of the biggest we’ve seen, we’ve featured many LEGO machines making things before.

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Painted Over But Not Forgotten: Restoring Lost Paintings With Radiation And Mathematics

January 4, 2022 by 23 Comments

An intrinsic property of paintings, that makes them both wonderful and very annoying, is the fact that they are physical objects. Sometimes they survive across the ages as amazing artifacts of their era, but they are also susceptible to being lost and even destroyed. Sometimes this destruction is deliberate, such as when a painting is painted over.

Artists reuse canvas all the time — painting over what was already there. Sometimes they might be coerced by a client into altering a painting, or removing entire elements from a scene. Fortunately, nowadays we have many techniques, involving x-rays and infrared radiation, that can analyze paintings to determine not only the composition of what we can see with the naked eye, but also that what lies underneath.

In some cases, we can then reconstruct what was previously hidden, returning to physical reality paintings and sketches which haven’t seen the light of day for sometimes centuries. Continue reading “Painted Over But Not Forgotten: Restoring Lost Paintings With Radiation And Mathematics” →

Angel Investor Gives Open Source PnP A Massive Boost

January 4, 2022 by 18 Comments

We love it when an Open Source hardware project grows up and turns into a sustainable business, bootstrapped with nothing but hard work and great ideas, but it’s a really tough prospect to do it using your own money, ploughing the profits from any sales back into development and not taking a dime in wages whilst you do so. People obviously need an income to live off, and that time spent working on a startup is time you can’t spend earning your keep. So it’s with great pleasure that we can bring you the latest news from [Stephen Hawes] and his pick-and-place machine plans. In the year since we last checked in with the project, development has continued at a steady pace, with the guys quickly outgrowing the garage workspace, whilst they prepare PnP machine kits ready for sale.

The big news is that [Joel Spolsky], co-founder of Stack Exchange, creator of Kanban management tool, Trello, and angel investor, has made a sizable ($100K USD) investment in the company which has allowed them to take on a 3,000+ sq. ft office space, and given them the funds for stock and all that boring business overhead stuff. [Stephen] takes time to explain that [Joel] will not have any control of the company, and all hardware and software will remain fully Open Source. For those interested [Joel] implemented his investment as a SAFE note (Simple Agreement for Future Equity) and as such, [Joel] will only make a return in the form of a small share allocation, if they hit the big-time in the future. Can’t really say fairer than that!

[Stephen] did recently receive a ‘cease and desist’ notice regarding his use of the ‘Index’ name for the project, since that is already a trademarked term, defended by somebody else, the project will need change name very soon. A minor setback, but it is a bit annoying that a chunk of that investment now has to go to a lawyer to make sure that the name they do eventually choose isn’t already taken and is safe to use.

In terms of the machine itself, it is now is fully operating, with multiple automatic tape feeders, featuring up and down-facing machine vision, and all that OpenPnP goodness. It has even been demonstrated placing parts for its own custom motherboard PCB, reprap style. Nice!

We wish [Stephen] and partner [Lucian] all the success they deserve, and hope they get those kits out there, because there are people around these parts that need an affordable, hackable, desktop PnP machine ASAP, this scribe included!

Here’s the earlier story covering the machine, but it’s not the only Open Source PnP machine we’ve seen – here’s another one from a few years ago.

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