Simple Sensor Makes Filament Measurements A Snap

Just how tight are the manufacturing tolerances of modern FDM printer filament. Inquiring minds want to know, and when such minds are attached to handy fellows like [Thomas Sanladerer], you end up with something like this home-brew filament measurement rig to gather the data you seek.

The heart of this build is not, as one might assume, some exotic laser device to measure the diameter of filament optically. Those exist, but they are expensive bits of kit that are best left to the manufacturers, who use them on their production lines to make sure filament meets their specs. Rather, [Thomas] used a very clever homemade device, which relies on a Hall effect sensor and a magnet on a lever to do the job. The lever is attached to a roller bearing that rides on the filament as it spools through the sensor; variations in diameter are amplified by the lever arm, which wiggles a magnet over the Hall sensor, resulting in a signal proportional to filament diameter.

The full test rig has a motor-driven feed and takeup spools, and three sensors measuring across the filament in three different spots around the radius; the measurements are averaged together to account for any small-scale irregularities. [Thomas] ran several different spools representing different manufacturers and materials through the machine; we won’t spoil the results in the video below, but suffice it to say you probably have little to worry about if you buy from a reputable vendor.

When we see a filament sensor, it’s generally more of the “there/not there” variety to prevent a printer from blindly carrying on once the reel is spent. We’ve seen a few of those before, but this is a neat twist on that concept.

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PLA-F Blends PLA And ABS

In the early days of 3D printing, most people used ABS plastic. It is durable and sticks well to simple surfaces. However, it smells and emits fumes that may be dangerous. It also tends to warp as it cools which causes problems when printing. PLA smells nicer and since it is made from corn is supposed to be less noxious. However, PLA isn’t as temperature resistant and while it will stick better to beds without heat, it also requires more airflow to set the plastic as it prints. [Kerry Stevenson] recently reviewed PLA-F which is a blend of the two plastics. Is it the best of both worlds? Or the worst?

[Kerry]  did several tests with interesting results. He did a temperature test tower and found the material printed well between 190 and 240 °C. He did note some stringing problems, though.

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Can A 3D Printer Print Better Filament For Itself?

3D printed parts are generally no way near the strength of an equivalent injection moulded part and techniques such as a sustained heat treatment, though effective usually distort the part beyond use.

[CNC Kitchen] was investigating the results (video, embedded below) of a recent paper, that described a novel ABS filament reinforced by a “star” shaped Polycarbonate core, an arrangement the authors claim is resilient to deformation during the annealing process often necessary to increase part strength. While the researchers had access to specialised equipment needed to manufacture such a composite material, [CNC Kitchen’s] solution of simply using his dual extruder setup to directly print the required hybrid filament is something we feel, strongly resonates with the now old school, RepRap “print your printer” sentiment.

The printed filament seems to have reasonable dimensional accuracy and passing the printed spool through a heater block without the nozzle attached, ensured there would be no obvious clogs. The rest of the video focuses on a very thorough comparison of strength and deformation between the garden variety Polycarbonate, ABS and this new hybrid filament after the annealing process. Although he concludes with mixed results, just being able to combine and print your own hybrid filament is super cool and a success in its own right!

Interested in multi-material filaments? Check out our article on a more conventional approach which does not involve printing it yourself!

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Can Lego Break Steel?

Betteridge’s Law of Headlines holds that any headline ending in a question mark can be answered with a resounding “No”. But as the video below shows, a Lego machine that twists steel asunder is not only possible, it’s an object lesson in metal fatigue. Touché, [Betteridge].

In pitting plastic against metal, the [Brick Experiment Channel] relied on earlier work with a machine that was able to twist a stock plastic axle from the Technics line of parts like a limp noodle. The steel axle in the current work, an aftermarket part that’s apparently no longer available, would not prove such an easy target.

Even after beefing up the test stand with extra Technics struts placed to be loaded in tension, and with gears doubled up and reinforced with extra pins, the single motor was unable to overcome the strength of the axle. It took a second motor and a complicated gear train to begin to deform the axle, but the steel eventually proved too much for the plastic to withstand. Round Two was a bit of a cheat: the same rig with a fresh axle, but this time the motor rotation was constantly switched. The accumulated metal fatigue started as a small crack which grew until the axle was twisted in two.

The [Brick Experiment Channel] is a fun one to check out, and we’ve featured them before. Along with destructive projects like this one, they’ve also got fun builds like this Lego playing card launcher, a Technic drone, and a Lego submarine.

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Annealing 3D Prints: A Scientific Approach

We’ve all been taught the scientific method: Form a hypothesis, do some experiments, gather some data, and prove or disprove the hypothesis. But we don’t always do it. We will tweak our 3D prints a little bit and think we see an improvement (or not) and draw some conclusions without a lot of data. Not [Josef Prusa], though. His team printed 856 different parts from four different materials to generate data about how parts behaved when annealed. There’s a video to watch, below.

Annealing is the process of heating a part to cause its structure to reorganize. Of course, heated plastic has an annoying habit of deforming. However, it can also make the parts firmer and with less inner tension. Printed parts tend to have an amorphous molecular structure. That is to say, they have no organization at all. The temperature where the plastic becomes soft and able to reorganize is the glass transition temperature.

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Anti-Lock Brakes For Bike Might Make Rides A Little Safer

Crashing one’s bike is a childhood rite of passage, one that can teach valuable lessons in applied physics. Assuming the kid is properly protected and the crash is fairly tame, scrapes and bruises are exchanged for the wisdom to avoid sand and gravel patches, and how to avoid a ballistic dismount by not applying the front brakes harder than or before the rear brakes.

But for many of us, those lessons were learned long ago using a body far more flexible than the version we’re currently in, and the stakes are higher for a bike ride that includes braking mistakes. To help with that, [Tom Stanton] has been working on anti-lock brakes for bicycles, and in the process he’s learned a lot about the physics and engineering of controlled deceleration.

It seems a simple concept – use a sensor to detect when a wheel is slipping due to decreased friction between the tire and the roadway, and release braking force repeatedly through an actuator to allow the driver or rider to maintain control while stopping. But that abstracts away a ton of detail, which [Tom] quickly got bogged down in. With a photosensor on the front wheel and a stepper motor to override brake lever inputs, he was able to modulate the braking force, but not with the responsiveness needed to maintain control. Several iterations later, [Tom] hit on the right combination of sensors, actuators, and algorithms to make a decent bike ABS system. The video below has all the details of the build and testing.

[Tom] admits bike ABS isn’t much of an innovation. We even covered an Arduino-instrumented bike that was to be an ABS testbed a few years back. But it’s still cool to see how much goes into anti-lock systems.

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ABS: Three Plastics In One

It would be really hard to go through a typical day in the developed world without running across something made from ABS plastic. It’s literally all over the place, from toothbrush handles to refrigerator interiors to car dashboards to computer keyboards. Many houses are plumbed with pipes extruded from ABS, and it lives in rolls next to millions of 3D-printers, loved and hated by those who use and misuse it. And in the form of LEGO bricks, it lurks on carpets in the dark rooms of children around the world, ready to puncture the bare feet of their parents.

ABS is so ubiquitous that it makes sense to take a look at this material in terms of its chemistry and its properties. As we’ll see, ABS isn’t just a single plastic, but a mixture that takes the best properties of its components to create one of the most versatile plastics in the world.

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