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.

Continue reading “The Case Against Calibration Cubes” →

This Week In Security: Glibc, Ivanti, Jenkins, And Runc

February 2, 2024 by Jonathan Bennett 4 Comments

There’s a fun buffer overflow problem in the Glibc __vsyslog_internal() function. This one’s a real rollercoaster, because logging vulnerabilities are always scary, but at a first look, it seems nearly impossible to exploit. The vulnerability relies on a very long program name, which can overflow an internal buffer. No binaries are going to have a name longer than 1024 bytes, so there’s no problem, right?

Let’s talk about argv. That’s the list of arguments that gets passed into the main() function of every Linux binary when it launches. The first string in that list is the binary name — except that’s a convention, and not particularly enforced anywhere. What really happens is that the execve() system call sets that list of strings. The first argument can be anything, making this an attacker-controlled value. And it doesn’t matter what the program is trying to write to the log, because the vulnerability triggers simply by writing the process name to a buffer.

There is a one-liner to test for a vulnerable Glibc:

exec -a "`printf '%0128000x' 1`" /usr/bin/su < /dev/null

and the Qualys write-up indicates that it can be used for an escalation of privilege attack. The good news is this seems to be a local-only attack. And on top of that, a pair of other lesser severity issues were found and fixed in glibc while fixing this one.
Continue reading “This Week In Security: Glibc, Ivanti, Jenkins, And Runc” →

Fixing A Malfunctioning Keithley Model 179 Digital Multimeter

February 2, 2024 by Maya Posch 6 Comments

Inspired by electronics repair videos on YouTube, [Steven Leibson] recently found himself hunting down something to fix on eBay. This ‘something’ ended up being a certified classic: a Keithley Model 179 digital multimeter from 1978. Listed as non-functional, the unit arrived at his door for less than $50. There weren’t any exciting pops or smoke when he powered it on, but the display seemed to be showing nothing but random nonsense.

The Keithley Model 179 multimeter has a convenient calibration sequence printed on its electrostatic shield cover and a deadly exposed ac line fuse in the upper left part of the photo. (Image credit: Steven Leibson) — The meter has a convenient calibration sequence printed on its electrostatic shield cover and a deadly exposed AC line fuse in the upper left part of the photo.

Ultimately reviving this little piece of history was quite simple, with the main issue turning out to be a dodgy inter-board connector between the main and display boards. After admiring an old repair attempt made on the component, he removed both the male and female connectors, replacing them with new ones.

This uncovered issues with the PCB, as the FR4 material and the traces on it had begun to delaminate, probably due to the old adhesive giving up due to age. With pretty low trace density this wasn’t anything that a bit of care couldn’t work around, fortunately.

Before finding this dodgy connector, [Steven] first tried to clean the front mechanical connectors, which took multiple sessions. This was followed up by oiling the mechanism. With the connector fixed and some cleaning, the meter’s display now read correctly. It still has some issues with starting up though, which [Steven] reckons are due to the old capacitors in the device.

Presumably some recapping will round off this fun device revival experience, but for the time being a Keithley Model 179 has been saved from e-waste, to inspire generations to come.

Retro-Styled Rasti Laptop Packs Framework Mobo

February 2, 2024 by Tom Nardi 7 Comments

Today, every laptop pretty much looks like every other laptop. Sure you might run into a few different colors and screen sizes out there, but on the whole, all the manufacturers have pretty much agreed on the basic shape and nobody is looking to rock the boat with something different.

Ah, but it wasn’t always so. Before the form factor we all recognize today took over, there were all sorts of interesting variations on the basic portable computer concept. For the Rasti, creator [Penk Chen] definitely took some inspiration from the iconic (and largely unobtanium) GRiD Compass of NASA and Aliens fame. But while its 3D printed case might look like a product of the early 1980s, on the inside, it features a Framework Laptop 13 mainboard using an 11th gen Intel CPU.

In addition to the widescreen 10.4 inch (1600 x 720) QLED display from Waveshare, the Rasti also includes a custom mechanical keyboard that’s actually been spun off into its own project. So even if you can’t swing building the whole Rasti, you could still find yourself tapping away on its vintage-styled input device.

Somewhat unsurprisingly, this isn’t the first time we’ve seen somebody 3D print a computer inspired by the GRiD Compass. The GRIZ Sextant we covered back in 2021 was another triumph that would be the envy of any hacker meetup.