[James] and his Lemontron portable 3D printer

If Life Gives You Lemons, Build This Lemontron

What if your 3D printer could fit in a box of filament but still rival the build plate size of heavyweights? Enter the Lemontron, a free and open source portable printer making waves in the maker community for its compact form factor and budget-friendly price. Watch [James]’ video on his build story here. Built around the Positron drive—a unique mechanism introduced by [Kralyn] in 2022—the Lemontron is the latest evolution of this innovative design. Although Kralyn mysteriously disappeared, their work inspired other projects like the Positron JourneyMaker and this Lemontron.

The Lemontron started as a unibody chassis mod for the JourneyMaker but grew into a complete redesign, cutting costs in half without sacrificing performance. By eliminating expensive CNC parts, it’s entirely made from off-the-shelf components, bringing the build cost to just $413. Compare that to $800 for the JourneyMaker and $699 for the Positron v3.2 kit.

Overhead photo of [James]' hands assembling the Lemontron Portable 3D printerRecent video updates show the Lemontron in action, printing impressively large and complex models. It tackled a marble run with 80-degree unsupported overhangs and a ‘comically large’ Benchy, proving its capability. Its compact design, paired with robust performance, is an exciting alternative for tinkerers seeking quality on a budget.

The Lemontron is in its final development stages, with frequent updates dropping on its YouTube channel. If you’re in the market for a more “traditional” mini-printer, check out this cool suitcase model from 2014.

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With Core ONE, Prusa’s Open Source Hardware Dream Quietly Dies

Yesterday, Prusa Research officially unveiled their next printer, the Core ONE. Going over the features and capabilities of this new machine, it’s clear that Prusa has kept a close eye on the rapidly changing desktop 3D printer market and designed a machine to better position themselves within a field of increasingly capable machines from other manufacturers.

While some saw the incremental upgrades of the i3 MK4 as being too conservative, the Core ONE ticks all the boxes of what today’s consumer is looking for — namely high-speed CoreXY movement with a fully enclosed chamber — while still offering the build quality, upgradability, and support that the company has built its reputation on. Put simply it’s one of the most exciting products they’ve introduced in a long time, and exactly the kind of machine that many Prusa fans have been waiting for.

Unfortunately, there’s one feature that’s ominously absent from the Core ONE announcement post. It’s easy to overlook, and indeed, most consumers probably won’t even know it’s missing. But for those of us who are concerned with such matters, it’s an unspoken confirmation that an era has finally come to an end.

With the Core ONE, Prusa Research is no longer in the business of making open source 3D printer hardware, but that doesn’t mean that the printer isn’t hackable. It’s complicated, so read on.

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FreeCAD Version 1.0 Released

After 22 years of development, FreeCAD has at long last reached the milestone of version 1.0. On this momentous occasion, it’s good to remember what a version 1.0 is supposed to mean, as also highlighted in the release blog post: FreeCAD is now considered stable and ready for ‘real work’. One of the most important changes here is that the topological naming problem (TNP) that has plagued FreeCAD since its inception has now finally been addressed using Realthunders’ mitigation algorithm, which puts it closer to parity here with other CAD packages. The other major change is that assemblies are now supported with the assembly workbench, which uses the Ondsel solver.

Other changes include an updated user interface and other features that should make using FreeCAD easier and closer in line with industry standards. In the run-up to the 1.0 release we already addressed the nightmare that is chamfering in FreeCAD, and the many overlapping-yet-uniquely-incomplete workbenches, much of which should be far less of a confabulated nightmare in this bright new 1.0 future.

Naturally, the big zero behind the major version number also means that there will still be plenty of issues to fix and bugs to hunt down, but it’s a promising point of progress in the development of this OSS CAD package.

Boss Byproducts: Calthemites Are Man-Made Cave Dwellers

Some lovely orange calthemite flowstone colored so by iron oxide from rusting steel reinforcing.
Some lovely orange calthemite flowstone colored so by iron oxide from rusting steel reinforcing. Image via Wikipedia

At this point, we’ve learned about man-made byproducts and nature-made byproducts. But how about one that’s a little of both? I’m talking about calthemites, which are secondary deposits that form in those man-made caves such as parking garages, mines, and tunnels.

Calthemites grow both on and under these structures in forms that mimic natural cave speleothems like stalactites, stalagmites, flowstone, and so on. They are often the result of an hyperalkalinic solution of pH 9-14 seeping through a concrete structure to the point of coming into contact with the air on the underside. Here, carbon dioxide in the air facilitates the necessary reactions to secondarily deposit calcium carbonate.

These calcium carbonate deposits are usually white, but can be colored red, orange, or yellow thanks to iron oxide. If copper pipes are around, copper oxide can cause calthemites to be blue or green. As pretty as all that sounds, I didn’t find any evidence of these parking garage growths having been turned into jewelry. So there’s your million-dollar idea.

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An Animated Walkthrough Of How Large Language Models Work

If you wonder how Large Language Models (LLMs) work and aren’t afraid of getting a bit technical, don’t miss [Brendan Bycroft]’s LLM Visualization. It is an interactively-animated step-by-step walk-through of a GPT large language model complete with animated and interactive 3D block diagram of everything going on under the hood. Check it out!

nano-gpt has only around 85,000 parameters, but the operating principles are all the same as for larger models.

The demonstration walks through a simple task and shows every step. The task is this: using the nano-gpt model, take a sequence of six letters and put them into alphabetical order.

A GPT model is a highly complex prediction engine, so the whole process begins with tokenizing the input (breaking up words and assigning numerical values to the chunks) and ends with choosing an appropriate output from a list of probabilities. There are of course many more steps in between, and different ways to adjust the model’s behavior. All of these are made quite clear by [Brendan]’s process breakdown.

We’ve previously covered how LLMs work, explained without math which eschews gritty technical details in favor of focusing on functionality, but it’s also nice to see an approach like this one, which embraces the technical elements of exactly what is going on.

We’ve also seen a much higher-level peek at how a modern AI model like Anthropic’s Claude works when it processes requests, extracting human-understandable concepts that illustrate what’s going on under the hood.

Junk Box Build Helps Hams With SDR

SDRs have been a game changer for radio hobbyists, but for ham radio applications, they often need a little help. That’s especially true of SDR dongles, which don’t have a lot of selectivity in the HF bands. But they’re so darn cheap and fun to play with, what’s a ham to do?

[VK3YE] has an answer, in the form of this homebrew software-defined radio (SDR) helper. It’s got a few features that make using a dongle like the RTL-SDR on the HF bands a little easier and a bit more pleasant. Construction is dead simple and based on what was in the junk bin and includes a potentiometer for attenuating stronger signals, a high-pass filter to tamp down stronger medium-wave broadcast stations, and a series-tuned LC circuit for each of the HF bands to provide some needed selectivity. Everything is wired together ugly-style in a metal enclosure, with a little jiggering needed to isolate the variable capacitor from ground.

The last two-thirds of the video below shows the helper in use on everything from the 11-meter (CB) band down to the AM bands. This would be a great addition to any ham’s SDR toolkit.

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