Cheap Endoscopic Camera Helps Automate Pressure Advance Calibration

March 21, 2025 by Dan Maloney 27 Comments

The difference between 3D printing and good 3D printing comes down to attention to detail. There are so many settings and so many variables, each of which seems to impact the other to a degree that can make setting things up a maddening process. That makes anything that simplifies the process, such as this computer vision pressure advance attachment, a welcome addition to the printing toolchain.

If you haven’t run into the term “pressure advance” for FDM printing before, fear not; it’s pretty intuitive. It’s just a way to compensate for the elasticity of the molten plastic column in the extruder, which can cause variations in the amount of material deposited when the print head acceleration changes, such as at corners or when starting a new layer.

To automate his pressure advance calibration process, [Marius Wachtler] attached one of those dirt-cheap endoscope cameras to the print head of his modified Ender 3, pointing straight down and square with the bed. A test grid is printed in a corner of the bed, with each arm printed using a slightly different pressure advance setting. The camera takes a photo of the pattern, which is processed by computer vision to remove the background and measure the thickness of each line. The line with the least variation wins, and the pressure advance setting used to print that line is used for the rest of the print — no blubs, no blebs.

We’ve seen other pressure-advanced calibrators before, but we like this one because it seems so cheap and easy to put together. True, it does mean sending images off to the cloud for analysis, but that seems a small price to pay for the convenience. And [Marius] is hopeful that he’ll be able to run the model locally at some point; we’re looking forward to that.

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Ask Hackaday: Do You Calibrate Your Instruments?

May 9, 2024 by Jenny List 54 Comments

Like many of you, I have a bench full of electronic instruments. The newest is my Rigol oscilloscope, only a few years old, while the oldest is probably my RF signal generator that dates from some time in the early 1950s. Some of those instruments have been with me for decades, and have been crucial in the gestation of countless projects.

If I follow the manufacturer’s recommendations then just like that PAT tester I should have them calibrated frequently. This process involves sending them off to a specialised lab where their readings are compared to a standard and they are adjusted accordingly, and when they return I know I can trust their readings. It’s important if you work in an industry where everything must be verified, for example I’m certain the folks down the road at Airbus use meticulously calibrated instruments when making assemblies for their aircraft, because there is no room for error in a safety critical application at 20000 feet.

But on my bench? Not so much, nobody is likely to face danger if my frequency counter has drifted by a few Hz. Continue reading “Ask Hackaday: Do You Calibrate Your Instruments?” →

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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Upgrade Puts A Lot Of Zeroes On Kit-Built Frequency Counter

December 7, 2023 by Dan Maloney No comments

If there’s anything more viscerally pleasing than seeing an eight-digit instrument showing a measurement with all zeroes after the decimal point, we’re not sure what it could. Maybe rolling the odometer over to another 100,000 milestone?

Regardless, getting to such a desirable degree of accuracy isn’t always easy, especially when the instrument in question is a handheld frequency counter that was built from a kit 23 years ago. That’s the target of [Petteri Aimonen]’s accuracy upgrade, specifically by the addition of a custom frequency reference module. The instrument is an ELV FC-500, which for such an old design looks surprisingly modern. Its Achille’s heel in terms of accuracy is the plain crystal oscillator it uses as a frequency standard, which has no temperature compensation and thus drifts by about 0.2 ppm per degree.

For a mains-powered lab instrument, the obvious solution would be an oven-controlled crystal oscillator. Those are prohibitive in terms of space and power for a handheld instrument, so instead a VCTCXO — voltage-controlled, temperature-compensated crystal oscillator — was selected for better stability. Unfortunately, no such oscillators matching the original 4.096-MHz crystal spec could be found; luckily, a 16.384-MHz unit was available for less than €20. All that was required was a couple of flip-flops to divide the signal by four and a bit of a bodge to replace the original frequency standard. A trimmer allows for the initial calibration — the “VC” part — and the tiny PCB tucks inside the case near the battery compartment.

We enjoyed the simplicity of this upgrade — almost as much as we enjoyed seeing all those zeroes. When you know, you know.

Commodore Datasette Does Its Own Calibration

November 7, 2022 by Jonathan Bennett 41 Comments

Ah, the beloved Commodore 64. The “best-selling computer system of all time”. And hobbyists are keeping the dream alive, still producing software for it today. Which leads us to a problem with using such old equipment. When you get your copy of Petscii Robots on cassette, and try to fastload it, your machine might just consistently fail to load the program. That’s fine, time to pull out the cue-tips and rubbing alcohol, and give the read heads a good cleaning. But what if that doesn’t do the job? You may just have another problem, like tape speed drift.

There are several different ways to measure the current tape speed, to dial it in properly. The best is probably a reference cassette with a known tone. Just connect your frequency counter or digital oscilloscope, and dial in the adjustment pot until your Datasette is producing the expected tone. Oh, you don’t have a frequency counter? Well good news, [Jan Derogee] has a solution for you. See, you already have your Datasette connected to a perfectly serviceable frequency counter — your Commodore computer. He’s put out a free program that counts the pulses coming from the Datasette in a second. So play a reference cassette, run the program, and dial in your Datasette deck. Simple! Stick around after the break for a very tongue-in-cheek demonstration of the problem and solution.

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3D Printable Bearings That Actually Work, No CAD Tweaking Required

September 17, 2022 by Donald Papp 22 Comments

3D printing bearings with an FDM printer can be an iffy endeavor, but it doesn’t have to be that way. [Matvey Kukuy]’s Ultimate 608 Bearing with Calibration Kit is everything you’ll need to dial in and print functional 608-style print-in-place bearings on your 3D printer.

Calibration pieces have a handy label attached for identification.

[Matvey] found that there are two key tolerances to get right. And by “get right” he means “empirically determine which works best with your filament and printer”. But don’t worry, there’s no need to get into CAD work to make that happen. [Matvey] has exported a staggering 64 slightly different calibration models (and their matching production versions) along with a printable testing tool. With the help of a step-by-step process that resembles a sort of binary search, one can take the Goldilocks approach to find just the right model for one’s filament and printer in a minimum of steps.

There’s one more tip as well: [Matvey] says that once you determine the best model to use, don’t fill the print bed with copies, unless you want a bed full of possibly non-working bearings! Why is this? A 3D printer prints a bed full of objects slightly differently than it prints a single one, and since the margin for error on the perfectly-selected bearing is so small, that can be enough to keep it from working. To print more than one bearing at a time, position them far from each other and use something like PrusaSlicer’s sequential printing, which is an option to print each object completely before starting the next one.

[Matvey]’s own best results came from printing with PLA at a layer height of 0.16 mm. He also used grease in the bearing to improve performance and extend its life. He doesn’t specify what kind of grease he used, but we’d recommend a plastic-safe grease like PTFE-based Super Lube.

Have you used 3D printed bearings in a project? Would [Matvey]’s design be helpful to you? Let us know all about it in the comments.

Programmable Resistance Box

July 19, 2022 by Bryan Cockfield 32 Comments

For prototype electronics projects, most of us have a pile of resistors of various values stored somewhere on our tool bench. There are different methods of organizing them for easy access and identification, but for true efficiency a resistance substitution box can be used on the breadboard to quickly change resistance values at a single point in a circuit. Until now it seemed this would be the pinnacle of quickly selecting differently-sized resistors, but thanks to this programmable resistor bank there’s an even better option available now.

Unlike a traditional substitution box or decade box, which uses switches or dials to select different valued resistors across a set of terminals, this one is programmable and uses a series of sealed relays instead. That’s not where the features stop, though. It also comes equipped with internal calibration circuitry which take into account the resistance of the relay contacts and internal wiring to provide a very precise resistance value across its terminals. It’s also able to be calibrated manually to account for temperature or other factors.

For an often-overlooked piece of test equipment, this one surely fits the bill of something we didn’t know we needed until now. Even though digital resistor substitution boxes are things we have featured in the past, the connectivity and calibration capabilities of this one make it intriguing.