Bolt-On Clog Detection For Your 3D Printer

Desktop 3D printing technology has improved by leaps and bounds over the last few years, but they can still be finicky beasts. Part of this is because the consumer-level machines generally don’t offer much in the way of instrumentation. If the filament runs out or the hotend clogs up and stops extruding, the vast majority of printers will keep humming along with nothing to show for it.

Looking to prevent the heartache of a half-finished print, [Elite Worm] has been working on a very clever filament detector that can be retrofitted to your 3D printer with a minimum of fuss. The design, at least in its current form, doesn’t actually interface with the printer beyond latching onto the part cooling fan as a convenient source of DC power. Filament simply passes through it on the way to the extruder, and should it stop moving while the fan is still running (indicating that the machine should be printing), it will sound the alarm.

Inside the handy device is a Digispark ATtiny85 microcontroller, a 128 x 32  I2C OLED display, a buzzer, an LED, and a photoresistor. An ingenious 3D printed mechanism grabs the filament on its way through to the extruder, and uses this movement to alternately block and unblock the path between the LED and photoresistor. If the microcontroller doesn’t see the telltale pulse after a few minutes, it knows that something has gone wrong.

In the video after the break, [Elite Worm] fits the device to his Prusa i3 MK2, but it should work on essentially any 3D printer if you can find a convenient place to mount it. Keep a close eye out during the video for our favorite part of the whole build, using the neck of a latex party balloon to add a little traction to the wheels of the filament sensor. Brilliant.

Incidentally, Prusa tried to tackle jam detection optically on the i3 MK3 but ended up deleting the feature on the subsequent MK3S since the system proved unreliable with some filaments. The official line is that jams are so infrequent with high-quality filament that the printer doesn’t need it, but it does seem like an odd omission when even the cheapest paper printer on the market still beeps at you when things have run afoul.

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3D Printering: Will A Resin Printer Retire Your Filament-based One?

Adding a resin printer to one’s workbench has never looked so attractive, nor been so affordable. Complex shapes with effortlessly great detail and surface finish? Yes, please! Well, photos make the results look effortless, anyway. Since filament-based printers using fused deposition modeling (FDM) get solid “could be better” ratings when it comes to surface finish and small detail resolution, will a trusty FDM printer end up retired if one buys a resin printer?

The short answer is this: for users who already use FDM, a resin-based stereolithography (SLA) printer is not likely to take over. What is more likely to happen is that the filament printer continues to do the same jobs it is good at, while the resin printer opens some wonderful new doors. This is partly because those great SLA prints will come at a cost that may not always justify the extra work.

Let’s go through what makes SLA good, what it needs in return, and how it does and doesn’t fit in with FDM.

When SLA Is Good, It’s REALLY Good

Objects with organic curves and no real “up” or “down” are much better suited to SLA than FDM.

The sweet spot for resin printing is this: small objects with smooth finishes, organic curves, and surface details. With SLA, these objects print more reliably and at a consistently higher quality than with FDM — as long as the operator does a good job with layout and support placement, anyway.

A big reason for this is that SLA does not produce layer lines the way FDM does. FDM prints are notorious for visible layer lines, and those lines are at their worst when spread across curved surfaces. SLA still creates objects one layer at a time, but the process doesn’t leave obvious lines.

There is also more freedom in part orientation when printing in resin. Unlike FDM, resin prints are isotropic. In the context of 3D printing, this means that the printed object’s physical properties do not change with respect to physical orientation. As long as a part is supported enough to print properly, a resin printer doesn’t much care in which orientation or at what angle it builds an object; the result will come out the same. This gives SLA printers more flexibility when it comes to part orientation, which helps when trying to keep presentation surfaces and details free from supports.

Niche Applications for SLA’s Strengths

One example of a niche for what resin printing is good at is gaming miniatures and figures. Tabletop enthusiasts are buying printers and resin, and designers of gaming-related models are finding success as well. The more successful ones thrive on sites like Patreon, with thousands of monthly supporters.

Engineering applications can have a place with SLA, so long as the objects are small enough. The build volume of most SLA printers is revoltingly tiny compared to FDM, but they make up for it with the ability to handle shapes and details that FDM would have problems with.

Beware SLA’s Added Costs

SLA printing brings some annoying buddies everywhere it goes in the form of added costs. These aren’t costs for the machines themselves; hobbyist SLA printers are very affordable. These ongoing costs are for consumables, increased time for upkeep and part processing, and storage space.

SLA requires more setup and cleanup than FDM. Printed parts need to be washed (usually in an alcohol bath) after printing, and possibly post-cured with additional UV exposure. Since resin is messy, disposable gloves and a spill-resistant work area are required. Another thing to consider is that resin isn’t meant to be left sitting in a printer for long periods, so when printing is done for the forseeable future, it’s time to empty the printer and clean the parts.

All of this takes time, but it also takes up valuable space in a work area. Bottles of resin, containers of alcohol, wash bins, gloves, a drip-proof work space, all of it takes up storage and table space. SLA printing as a whole will take up far more room than just the printer itself.

The other thing to consider is the need for manual post-processing. Resin prints tend to require a lot of supports, and those supports need to be removed by hand. These leave behind small marks that may need to be sanded away. With FDM, supports are a last resort that are used only if needed, but with SLA they are the rule rather than the exception.

Things FDM Is Still Good At

A well-maintained FDM printer is a fantastic tool for prototyping, iterating on designs, and creating functional parts. FDM also has other advantages that really stand out when contrasted with resin printing.

FDM is perfectly happy to wait patiently until needed, at which point a print can be started with a minimum of fuss. The consumables are few and reasonably priced. Filament is best stored in a dry environment, but besides that, it doesn’t ask for much. Swapping filament types or colors is simple, clean, and easy. Even a failed print doesn’t usually involve much more than sweeping away a mess of plastic and trying again.

The biggest disadvantages are related to layer line visibility, the resolution of surface detail, and working with curved organic shapes. None of these can be waved away, but they can be mitigated to some extent. Variable Layer Height tries to address layer line visibility, and it is a feature that has worked its way into most slicer software. The ability to render very small details and features can be improved, to some extent, by swapping a printer’s standard 0.4 mm nozzle for a smaller one.

FDM printers are most challenged by being asked to print curved objects that have no flat areas and no real “up” or “down”. One option is splitting these objects into smaller and more easily-printed ones, but that’s not always practical. Printing a tricky model will require supports, and supports with FDM always result in degraded surface quality. Water-soluble support structures can help mitigate this, but doing so requires multi-material printing. SLA, on the other hand, is far more suited to such objects.

Is There Room for Both?

Resin prints look fantastic and it may be tempting to think of SLA as superior to FDM, but that is not the whole story. They are different tools, and good at different things. Unless your needs are very specific, you’ll probably benefit from access to both.

If you need to print small objects with good surface finish and detail resolution, and you can deal with the added hassles of working with resin, then SLA is definitely for you. But even if you only print small objects, a working FDM printer can easily earn its place on your workbench with the ability to create functional parts without any significant setup and cleanup. If you’re considering an SLA printer, don’t plan to ditch FDM just yet.

I regularly use both but personally, I always choose a filament-based printer if possible; even if a final model will eventually be printed in resin, it’s simply cheaper and faster and easier to prototype and iterate with FDM.

If you have access to both, has this also been your experience? Do you know of a niche for resin printing that hits the spot in a way nothing else does, the way SLA has done with tabletop enthusiasts? We want to hear all about it, so let us know in the comments.

Bubbly Filament Works Better Than You Think

Normally bubbles appearing in your extruded filament would be considered a bad sign, but it turns out you can now buy filament that has been specifically formulated to foam. [Stefan] from CNC Kitchen has doing some experiments with these bubbly filaments, and the results have been very interesting.

The filaments in question are VARIOSHORE TPU and LW-PLA, both by ColorFabb. Both filaments have a blowing agent added to the formulation, which releases gas as the temperature is increased. This causes bubbles to form, creating a cellular structure, which decreases the density and increases the flexibility of the printed part. This isn’t the first time that foaming is sold as a feature, but previously it was only done for aesthetic purposes in Polymaker’s Polywood filament.

Before putting the materials through his excellent test procedures, [Stefan] first goes through the process of tuning the print settings. This can be tricky because of the foaming, which increases the effective volume of the plastic, requiring careful adjustment of the extrusion rate. Foaming in the PLA filament reached its maximum foaming at 250 C, at which its density was 44% of the unfoamed filament.

In testing the physical properties, [Stefan] found that the tensile strength and stiffness of printed parts are reduced as foaming increases, but the impact strength is improved. He concludes that the lightweight PLA can have some interesting applications because of the reduced weight and increased impact strength, with 3D printed RC aircraft being an excellent example of this. It should also be possible to change the between layers, effectively sandwiching the foamed layers between solid skins.

[Stefan]’s videos are an excellent resource for those looking to master the finer points of 3D printing with different materials. He has reinforced prints with carbon fiber, played with extrusion widths and developed an ingenious gradient infill technique.

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A Beginner’s Guide To X-Ray Crystallography

In graduate school, I had a seminar course where one of the sections was about X-ray crystallography. I was excited, because being able to discern the three-dimensional structure of macromolecules just by shining X-rays on them seemed like magic to me. And thanks to a lackluster professor, after the section it remained just as much of a mystery.

If only I’d had [Steve Mould] as a teacher back then. His latest video does an outstanding job explaining X-ray crystallography by scaling up the problem considerably, using the longer wavelength of light and a macroscopic target. He begins with a review of diffraction patterns, those alternating light and dark bands of constructive and destructive interference that result when light shines on two closely spaced slits — the famous “Double-Slit Experiment” that showed light behaves both as a particle and as a wave and provided our first glimpse of quantum mechanics. [Steve] then doubled down on the double-slit, placing another pair of slits in the path of the first. This revealed a grid of spots rather than alternating bands, with the angle between axes dependent on the angle of the slit pairs to each other.


To complete the demonstration, [Steve] then used diffraction to image the helical tungsten filament of an incandescent light bulb. Shining a laser through the helix resulted in a pattern bearing a striking resemblance to what’s probably the most famous X-ray crystallogram ever: [Rosalind Franklin]’s portrait of DNA. It all makes perfect sense, and it’s easy to see how the process works when scaled down both in terms of the target size and the wavelength of light used to probe it.

Hats off to [Steve] for making something that’s ordinarily complex so easily understandable, and for filling in a long-standing gap in my knowledge.

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Automatic Rewinder Makes Kite Retrieval A Breeze

So you’ve built a fine kite, taken it to the beach, and let it ride the wind aloft on a spool of line. Eventually it has to come down, and the process of reeling all that line that was so easily paid out is likely a bigger chore than you care to face. What to do?

If you’re like [Matt Bilsky], the answer is simple: build a motorized kite reel to bring it back in painlessly. Of course what’s simple in conception is often difficult to execute, and as the second video below shows, [Matt] went through an extensive design and prototype phase before starting to create parts. Basic questions had to be answered, such as how much torque would be needed to reel in the kite, and what were the dimensions of a standard kite string reel. With that information and a cardboard prototype in hand, the guts of a cordless drill joined a bunch of 3D-printed parts to form the running gear. We really liked the research that went into the self-reversing screw used to evenly wind the string across the spool; who knew that someone could do a doctoral dissertation on yarn-winding? Check out the “Reeler-Inner” in action in the first, much shorter video below.

With some extra power left from the original drill battery, [Matt] feature-crept a bit with the USB charger port and voltmeter, but who can blame him? Personally, we’d have included a counter to keep track of how much line is fed out; something like this printer filament counter might work, as long as you can keep the sand out of it.

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Assessing Nozzle Wear In 3D-Printers

How worn are your nozzles? It’s a legitimate question, so [Stefan] set out to find out just how bad 3D-printer nozzle wear can get. The answer, as always, is “It depends,” but exploring the issue turns out to be an interesting trip.

Reasoning that the best place to start is knowing what nozzle wear looks like, [Stefan] began by printing a series of Benchies with brand-new brass nozzles of increasing diameter, to simulate wear. He found that stringing artifacts, interlayer holes, and softening of overhanging edges and details all worsened with increasing nozzle size. Armed with this information, [Stefan] began a torture test of some cheap nozzles with both carbon-fiber filament and a glow-in-the-dark filament, both of which have been reported as nozzle eaters. [Stefan] found that to be the case for at least the carbon-fiber filament, which wore the nozzle to a nub after extruding only 360 grams of material.

Finally, [Stefan] did some destructive testing by cutting used nozzles in half on the mill and looking at them in cross-section. The wear on the nozzle used for carbon-fiber is dramatic, as is the difference between brand-new cheap nozzles and the high-quality parts. Check out the video below and please sound off in the comments if you know how that peculiar spiral profile was machined into the cheap nozzles.

Hats off to [Stefan] for taking the time to explore nozzle wear and sharing his results. He certainly has an eye for analysis; we’ve covered his technique for breaking down 3D-printing costs in [Donald Papp]’s  “Life on Contract” series.

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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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