This Service Life Study Really Grinds Our Gears

3D printing is arguably over-used in the maker community. It’s just so easy to run off a quick prototype and then… well, it’s good enough, right? Choosing the right plastic can go a long way to making sure your “good enough” prototype really is good enough for long term use. If you’re producing anything with gearing, you might want to cast your eyes to a study by [Mert Safak Tunalioglu] and [Bekir Volkan Agca] titled: Wear and Service Life of 3-D Printed Polymeric Gears.

Photograph of the test rig used in the study.
No spin doctoring here, spinning gears.

The authors printed simple test gears in ABS, PLA, and PETG, and built a test rig to run them at 900 rpm with a load of 1.5 Nm against a steel drive gear. The gears were pulled off and weighed every 10,000 rotations, and allowed to run to destruction, which occurred in the hundreds-of-thousands of rotations in each case. The verdict? Well, as you can tell from the image, it’s to use PETG.

The authors think that this is down to PETG’s ductility, so we would have liked to see a hard TPU added to the mix, to say nothing of the engineering filaments. On the other hand, this study was aimed at the most common plastics in the 3D printing world and also verified a theoretical model that can be applied to other polymers.

This tip was sent in by [Benjamin], who came across it as part of the research to build his first telescope, which we look forward to seeing. As he points out, it’s quite lucky for the rest of us that the U.S. government provides funding to make such basic research available, in a way his nation of France does not. All politics aside, we’re grateful both to receive your tips and for the generosity of the US taxpayer.

We’ve seen similar tests done by the community — like this one using worm gears — but it’s also neat to see how institutional science approaches the same problem. If you need oodles of cycles but not a lot of torque, maybe skip the spurs and print a magnetic gearbox. Alternatively you break out the grog and the sea shanties and print yourself a capstan.

What Happened To The 100,000-Hour LED Bulbs?

Early adopters of LED lighting will remember 50,000 hour or even 100,000 hour lifetime ratings printed on the box. But during a recent trip to the hardware store the longest advertised lifetime I found was 25,000 hours. Others claimed only 7,500 or 15,000 hours. And yes, these are brand-name bulbs from Cree and GE.

So, what happened to those 100,000 hour residential LED bulbs? Were the initial estimates just over-optimistic? Was it all marketing hype? Or, did we not know enough about LED aging to predict the true useful life of a bulb?

I put these questions to the test. Join me after the break for some background on the light bulb cartel from the days of incandescent bulbs (not a joke, a cartel controlled the life of your bulbs), and for the destruction of some modern LED bulbs to see why the lifetimes are clocking in a lot lower than the original wave of LED replacements.

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Solar Heart Engineered To Beat For Decades

It’s often said that if something is worth doing it’s worth doing right, or maybe even worth overdoing. This is clearly a concept that [ANTALIFE] takes very seriously, as made abundantly clear by projects like the solar powered “beating” heart he made as a gift for his wife. What for most of us would have ended up being a junk bin build becomes a considerable engineering project in his hands, with a level of research and fine tuning that’s frankly staggering.

But [ANTALIFE] didn’t put this much thought into the device just for fun. He wants it to remain functional for as long as 30 years, and hopes he and the missus can still look on it fondly in their retirement years. Keeping an electronic device up and running for decades straight means you need to look carefully at each component and try to steer clear of any potential pitfalls.

The biggest one was the battery. More specifically, the fact he couldn’t use one. The lifetime of most rechargeable batteries is measured in hundreds of cycles, which for a device which will be charged by solar every day, means the battery is going to start showing its age in only 4 to 5 years. That simply wasn’t going to cut it.

[ANTALIFE] did some digging and realized that the solution was to use a supercapacitor, specifically the AVX SCMS22C255PRBA0. This is little wonder is rated for a staggering half million cycles, which in theory means that even with daily use it should still take a charge in the year 3300. In practice of course there are a lot of variables which will reduce that lifetime such as temperature fluctuations and the Earth being conquered by apes; but no matter what caveats you put on the figure it should still make 30 years without breaking a sweat.

Similar thought was given to choosing a solar cell with a suitably long lifetime, and he did plenty of testing and experimentation with his charging circuit, including some very nice graphs showing efficiency over time, to make sure it was up to snuff. Finally he walks the reader though his light-sensitive ring oscillator circuit which gives the device its pleasing “breathing” effect once the lights go down.

We’d love to bring you an update on this device in 30 years to see how close [ANTALIFE] got, but as we’re still trying to work the kinks out of the mobile version of the site we can’t make any guarantees about what the direct-brain interface version of HaD might look like. In the meantime though, you can read up on the long term battle between supercapacitors and traditional batteries.

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