The Case Against Calibration Cubes

February 2, 2024 by Danie Conradie 27 Comments

Calibration cubes have long been a staple for testing and adjusting 3D printers, but according to [Stefan] of CNC Kitchen, they’re not just ineffective—they could be leading us astray. In the video after the break he explains his reasoning for this controversial claim, and provides a viable alternative.

Such cubes are often used to calibrate the steps per millimeter for the printer’s steppers, but the actual dimensions of said cube can be impacted by over or under extrusion, in addition to how far the machine might be out of alignment. This can be further exacerbated by measuring errors due to elephant’s foot, over extruded corners, or just inaccuracies in the caliper. All these potential errors which can go unnoticed in the small 20 x 20 mm cube, while still leading to significant dimensional errors in larger prints

So what’s the solution? Not another cube. It’s something called the “CaliFlower” from [Adam] of Vector 3D. This is not a typical calibration model — it’s carefully designed to minimize measurement errors with ten internal and external measuring points with stops for your calipers. The model costs $5, but for your money you get a complete guide and spreadsheet to calculate the required of corrections needed in your firmware or slicer settings.

If you regularly switch materials in your 3D printer, [Stefan] also advises against adjusting steps per millimeter and suggests defining a scaling factor for each material type instead. With this method validated across different materials like PLA, PETG, ABS, and ASA, it becomes evident that material shrinkage plays a significant role in dimensional inaccuracy, not just machine error. While [Stefan] makes a convincing case against the standard calibration cube for dimensional calibration, he notes that is is still useful for evaluating general print quality and settings.

[Stefan] has always done rigorous testing to back his claims, and this video was no different. He has also tested the effects of filament color on part strength, the practicality of annealing parts in salt, and even printing custom filament.

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3D Printed Axial Compressor Is On A Mission To Inflate Balloons

January 29, 2024 by Donald Papp 5 Comments

[Let’s Print] has been fascinated with creating a 3D printed axial compressor that can do meaningful work, and his latest iteration mixes FDM and SLA printed parts to successfully inflate (and pop) a latex glove, so that’s progress!

Originally, the unit couldn’t manage even that until he modified the number and type of fan blades on the compressor stages. There were other design challenges as well. For example, one regular issue was a coupling between the motor and the rest of the unit breaking repeatedly. At the speeds the compressor runs at, weak points tend to surface fairly quickly. That’s not stopping [Let’s Print], however. He plans to explore other compressor designs in his quest for an effective unit.

Attaching motor shafts to 3D printed devices can be tricky, and in the past we’ve seen a clever solution that is worth keeping in mind: half of a spider coupling (or jaw coupling) can be an economical and effective way to attach 3D printed things to a shaft.

While blowing up a regular party balloon is still asking too much of [Let’s Print]’s compressor as it stands, it certainly inflates (and pops) a latex glove like nobody’s business.

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Hotshot 3D Printed Hovercraft Is Devastatingly Fast

January 27, 2024 by Lewin Day 8 Comments

These days, it’s pretty cheap and easy to build your own little RC hovercraft. [ValRC] demonstrates just that with a hovercraft build that is surprisingly nimble, and fast to boot.

The build started with a design [ValRC] found online. It was simple enough to print and assemble, needing only a pair of a brushless motors, a speed controller, a receiver, and a servo to run the show. The design uses a plastic bag as a skirt, assembled around a 3D printed frame. That proved to be the hardest part of the build, as hot glue didn’t want to play nice with the thin garbage bag.

Even despite the challenges, once assembled, the hovercraft performed well. It readily slid around on a cushion of air, drifting across asphalt with abandon. Upgrades included a better rudder and a skirt made of thicker and more resilient plastic. The final craft looked mesmerizing as it glided over the smooth concrete of a parking garage with ease.

A hovercraft is, honestly, one of the cooler printable projects for beginners. All you need is a simple design, some powerful motors, and you’re good to go.

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A DIY E-Ink Tank Watch

January 26, 2024 by Dave Rowntree 9 Comments

[Augusto Marinucci] liked the classic Cartier Tank series of dress watches aesthetic, but wanted something a bit more techy, with a decent runtime on a single battery. E-Ink displays are often used in such applications, but finding one to fit a custom case design, is a tall order. When ordering one off the shelf is not easy, the solution is to make one from scratch.

Building a programming jig is a great idea for small-scale production

The article doesn’t have much information on the E-Ink side of things, which is a bit of a shame. But from what we can glean, the segment shapes — in this case, based on the famous Apollo DSKY — are formed in the top copper of a four-layer PCB, using filled and capped vias to connect invisibly from below.

A donor E-Ink display is cut to size with scissors (we don’t know much more than this!) and glued in place around the edge to make the common electrode connection. The display PCB attaches to the control PCB, at the rear using low-profile board-to-board connectors. This board hosts a PIC16 micro, as well as an RV-3028-C7 RTC which keeps time whilst consuming a paltry 45 nA.

Five volts are provided via a MAX1722 low-power boost converter which is fed power from the CR1616 cell via a couple of logic-controllable load switches. With a low-power design such as this, it’s critical to get this correct. Any mistakes here can easily result in a very low runtime. It is easy to over-stress small button cells and kill them prematurely.

The case looks like it’s printed in a translucent resin, with the PCB stack sealed inside with a UV-cured resin pour. It’s not immediately obvious if the rear panel can be removed to access the battery and programming port. There are what appear to be screw holes, so maybe that’s possible, or maybe they’re the rear side of the PCB mounting posts. Who can tell?

If DIY hardware is but too much effort for you, then there’s the option of hacking new firmware onto an existing watch, or perhaps meeting in the middle and making something out of all those junk E-ink tags you can get from time to time?

Thanks to [JohnU] for the tip!

Kinetic Clock Is A Clean Modern Way To Tell Time

January 16, 2024 by Lewin Day 11 Comments

Hackers and makers aren’t usually too interested in basic round analog clocks. They tend to prefer building altogether more arcane and complicated contraptions to display numbers for the telling of time. [alstroemeria] did just that with this nifty kinetic clock build.

The basic concept of the kinetic clock is to have a flat plate, which individual segments raise out of to create a physical (instead of illuminated) 7-segment display. This is achieved with servos which push the segments in and out using a small rack mechanism. It’s not a sophisticated build; it simply uses 30 servos to handle all the segments needed to tell time. Thus, the Arduino Mega was the perfect tool for the job. With a sensor shield added on, it has an abundance of IO, driving a ton of servos is a cinch. There’s also a DS3231 real time clock to help it keep accurate time.

Incidentally, it’s a hefty thing to print, according to YouTuber [Lukas Deem] who replicated the project. It took around 85 hours to print, and a total of 655 grams of filament – not counting mistakes and trashed parts.

And if you think you’re having deja-vu, you might well be. We’ve seen a take on this exquisite design before. We liked it then, and we like it now.

Overall, it’s a stylish build that looks as good as your 3D printer’s output will allow. A resin printer would be a massive boon in this regard. Video after the break.

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Möbius Tank’s Twisty Treads Became Bendy

January 14, 2024 by Donald Papp 14 Comments

[James Bruton]’s unusual Möbius Tank has gotten a little more unusual with the ability to bend itself, which allows it to perform turns even though it is a single-track vehicle.

The turning radius isn’t great, but three-point turns are perfectly feasible.

The Möbius Tank was a wild idea that started as a “what if” question: what if a tank tread was a Möbius strip? We saw how [James] showed it could be done, and he demonstrated smart design and assembly techniques in the process.

He’s since modified the design to a single-track, and added a flex point in the center of the body. Two linear actuators work together to make the vehicle bend, and therefore give it the ability to steer and turn. A normal tread would be unable to bend in this way, but the twist in the Möbius tread accommodates this pivot point perfectly well.

It works, but it’s not exactly an ideal vehicle. With the tread doing a 90-degree twist on the bottom, there isn’t a lot of ground clearance. In addition, since the long vehicle has only a single tread, it is much taller than it is wide. Neither does it any real favors when it comes to stability over uneven terrain, but it’s sure neat to try.

Even if it’s not practical, Möbius Tank is wild to look at. Check it out in the video, embedded just under the page break.

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Tips For 3D Printing Watertight Test Tubes

January 13, 2024 by Donald Papp 12 Comments

[DaveMakesStuff] uses 3D printed test tubes for plants and similar purposes, and he’s shared how to make them on a 3D printer, complete with different models each optimized for different nozzle sizes.

The slots in the model are a means of manipulating how the slicer creates a toolpath when printing in spiral vase mode. These areas end up denser and stronger than they otherwise would be.

It’s not too hard to get clear-looking prints in spiral vase mode by using a transparent filament, but the real value in his design is that it comes out reliably watertight, with an extra-strong base and rim.

How is this accomplished when using spiral vase mode, which extrudes only a single wall perimeter? By using fancy geometry on the part, which makes the nozzle follow a high-density path that turns back onto itself multiple times, in concept a little like a switchback trail. The result is extra-dense areas on both the rim and the bottom of the tubes. This helps make them not only watertight, but far stronger than a single wall.

This technique is reminiscent of an earlier method we saw of enhancing the strength of vase mode prints by modeling thin slots into an object. After slicing, the model still consists of a single unbroken spiral extrusion. But in practice, the extruded plastic forms what resemble structural ribs. Why? Because those technically-adjacent extruded lines are so close to one another that they end up sticking together. Something similar is being done here by [DaveMakesStuff] to ensure that the bottom and top of the tubes are extra strong.

You can see a short video (embedded below) that showcases the tubes, as well as some modular 3D-printable racks that [DaveMakesStuff] also makes. And should you want some tips on getting better transparency from your 3D prints, the essentials boil down to printing with transparent filament, slightly hotter, and with a slightly higher extrusion rate.

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