Last week, we noted an attempt to fix a hardware problem with software, which backfired pretty dramatically for Ford when they tried to counter the tendency for driveshafts to fall out of certain of their cars by automatically applying the electric parking brake.
This week, the story is a little different, but still illustrates how software and hardware can interact unpredictably, especially in the automotive space. The story centers on a 2015 Optima recall for a software update for the knock sensor detection system. We can’t find the specifics, but if this recall on a similar Kia model in the same model year range and a class-action lawsuit are any indication, the update looks like it would have made the KSDS more sensitive to worn connecting rod damage, and forced the car into “limp home mode” to limit damage to the engine if knocking is detected.
A clever solution to a mechanical problem? Perhaps, but because the Kia owner in the story claims not to have received the snail-mail recall notice, she got no warning when her bearings started wearing out. Result: a $6,000 bill for a new engine, which she was forced to cover out of pocket. Granted, this software fix isn’t quite as egregious as Ford’s workaround for weak driveshaft mounting bolts, and there may very well have been a lack of maintenance by the car’s owner. But if you’re a Kia mechanical engineer, wouldn’t your first instinct have been to fix the problem causing the rod bearings to wear out, rather than papering over the problem with software?
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.
[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.
Can you turn 47 pounds (21 kg) of PLA filament into a gigantic working 3D-printed RC car? No, no you can’t — at least not if you eschew proper bearings in favor of printed bushings.
That’s the hard lesson that [Joel Telling] learned with his scaled up version of the OpenRC F1 car, an RC car that can be mostly 3D-printed. The small version still has its share of non-printed parts, mainly screws and bearings. In his video series documenting the build of the upsized version, [Joel] elaborates on some of the reasons for going with printed bushings rather than bearings, which mainly boil down to hoping that the graphite lubricant powder he added would reduce friction enough to prevent the parts from welding themselves together.
The car came out looking great, and even managed to scoot about nicely for a few seconds before its predictably noisy and unhappy demise. But what was unexpected was the actual failure mode. The plastic-on-plastic running gear seemed to handle the rolling loads fine; it was the lateral force exerted on the axle by the tension of the drive belt that was too much for the printed bushing to bear.
As [Joel] rightly points out, it’s only a failure if you fail to learn something, so kudos to him for at least giving this a try. And all that PLA won’t go to waste, of course — everything else on the car worked fine, so adding one bearing should get it back on the road. He should check out our primer on bearings for a few tips on selecting the right one.
Over the past few decades, numerous space probes sent to the far-flung reaches of the Solar System have fallen silent. These failures weren’t due to communications problems, probes flying into scientifically implausible anomalies, or little green men snatching up the robotic scouts we’ve sent out into the Solar System. No, these space probes have failed simply because engineers on Earth can’t point them. If you lose attitude control, you lose the ability to point a transmitter at Earth. If you’re managing a space telescope, losing the ability to point a spacecraft turns a valuable piece of scientific equipment into a worthless, spinning pile of junk.
The reasons for these failures is difficult to pin down, but now a few people have an idea. Failures of the Kepler, Dawn, Hayabusa, and FUSE space probes were due to failures of the reaction wheels in the spacecraft. These failures, in turn, were caused by space weather. Specifically, coronal mass ejections from the Sun. How did this research come about, and what does it mean for future missions to deep space?
A few months ago we showed you a bar bot built by [GreatScott] that uses peristaltic pumps to food-safely move the various spirits and mixers around behind the curtain. The bar bot uses three of them, and at $30 each for pumps with decent flow rate, they added a lot to the parts bill. These pumps are pretty much the ideal choice for a bar bot, so what do you do? [GreatScott] decided to see if it was worth it to make them instead.
Peristaltic pumps are simple devices that pump liquids without touching them. A motor turns a set of rollers that push a flexible tube against a wall. As the motor turns, the rollers move liquid through the tube by squeezing it flat from the outside in turns. Typically, the more you pay for an off-the-shelf peristaltic, the higher the flow rate.
[GreatScott] figured it was cheaper to buy the motor and the control circuitry. He chose a NEMA-17 for their reputation and ubiquity and a DRV8825 controller to go with it. The pump is driven by an Arduino Nano and a pot controls the RPM. After trying to design the mechanical assembly from scratch, he found [Ralf]’s pump model on Thingiverse and modified it to fit a NEMA-17.
The verdict? DIY all the way, assuming you can print the parts. [GreatScott] was trying to beat the purchased pumps’ flow rate of 100mL/minute and ended up with 200mL/minute from his DIY pump. Squeeze past the break for the build video and demonstration.
They lie at the heart of every fidget spinner and in every motor that runs our lives, from the steppers in a 3D printer to the hundreds in every car engine. They can be as simple as a lubricated bushing or as complicated as the roller bearing in a car axle. Bearings are at work every day for us, directing forces and reducing friction, and understanding them is important to getting stuff done with rotating mechanisms.
So you’re looking to buy your first 3D printer, and your index finger is quivering over that 300 US Dollar printer on Amazon.com. Stop! You’re about to have a bad time. 3D printing has come a long way, but most 3D printers are designed through witchcraft, legends, and tall tales rather than any rigorous engineering process. I would say most 3D printer designs are either just plain bad, or designed by a team of Chinese engineers applying all their ingenuity to cost cutting. There are a few that are well designed, and there is a comparatively higher price tag attached.
I’ll start by going through some of the myths and legends that show up in 3D printers. After that I’ll go through some of the common, mostly gimmick, features that typically hinder your printer’s ability, rather than adding any useful function. Next I’ll go onto the things that will actually make your printer better. Finally, I’ll add some special consideration if you’re a beginner buying your first printer.