Fail Of The Week: How Not To Build A Filament Extruder

It would be great if you could create your own filament. On the face of it, it seems easy to do, but as [Thomas Sanladerer] found out when he was a student, there are a lot of details that can bedevil your design. His extruder sort of works, but he wouldn’t suggest duplicating his effort. In fact, he hopes you can learn what not to do if you try to do it yourself.

In all fairness, [Thomas] was a low-budget student and was trying to economize. For example, he tried using a drill to drive the auger. Why not? It looks like a drill bit. But he found out that wasn’t satisfactory and moved to a pair of wiper motors with their built-in gear train.

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Under Pressure: How Aluminum Extrusions Are Made

At any given time I’m likely to have multiple projects in-flight, by which of course I mean in various stages of neglect. My current big project is one where I finally feel like I have a chance to use some materials with real hacker street cred, like T-slot extruded aluminum profiles. We’ve all seen the stuff, the “Industrial Erector Set” as 80/20 likes to call their version of it. And we’ve all seen the cool projects made with it, from CNC machines to trade show displays, and in these pandemic times, even occasionally as sneeze guards in retail shops.

Aluminum T-slot profiles are wonderful to work with — strong, lightweight, easily connected with a wide range of fasteners, and infinitely configurable and reconfigurable as needs change. It’s not cheap by any means, but when you factor in the fabrication time saved, it may well be a net benefit to spec the stuff for a project. Still, with the projected hit to my wallet, I’ve been looking for more affordable alternatives.

My exploration led me into the bewilderingly rich world of aluminum extrusions. Even excluding mundane items like beer and soda cans, you’re probably surrounded by extruded aluminum products right now. Everything from computer heatsinks to window frames to the parts that make up screen doors are made from extruded aluminum. So how exactly is this ubiquitous stuff made?

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This Four-Axis Stencil Printer Is The Ultimate In SMD Alignment Tools

Here at Hackaday we love all kinds of builds, and we celebrate anytime anyone puts parts together into something else. And while we love the quick and dirty builds, there’s just something about the fit and finish of this four-axis SMD stencil printer that really pushes our buttons.

This build comes to us from [Phillip], who like many surface-mount users was sick of the various tape-and-PCB methods that are commonly used to align the solder stencil with the PCB traces. His solution is this fully adjustable stencil holder made from aluminum extrusions joined by 3D-printed parts. The flip-up frame of the device has a pair of clamps for securely holding the stainless steel stencil. Springs on the clamp guide rods provide some preload to keep the stencil taut as well as protection from overtensioning.

The stencil can move in the X-, Y-, and Z-axes to line up with a PCB held with 3D-printed standoffs on a bed below the top frame. The bed itself rotates slightly to overcome any skew in alignment of the PCB. [Phillip] was aghast at the price of an off-the-shelf slew-ring bearing for that axis, but luckily was able to print up some parts and just use simple roller bearing to do the same thing for a fraction of the cost. The frame is shown in use below; the moment when the pads line up perfectly through the stencil holds is oddly satisfying.

This puts us in mind of a recent, similar stencil printer we covered. That one was far simpler, but either one of these beats the expedient alignment methods hands down.

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Make Your Own Filament

According to [Alex] it is easy to make your own rolls of 3D printing filament, even though existing off-the-shelf solutions don’t work very well. His explanation for this is economics. He built a filament extruder using a high torque induction motor and gearbox that was locally sourced. He argues that shipping heavy gear around would make a similar extruder commercially unattractive. He sunk about $600 into the device but estimates that a company would need to charge at least $1,500 or more for the same thing. That may seem steep but as [Alex] points out, a 1 kg roll of filament really only has about 750 grams for filament and plastic pellets cost $2 to $3 per kilogram.

There are other costs, of course, like the electricity required to heat and move the plastic. Still, the system appears to use about $1 of electricity for every 10 kg of filament. You can see the process in the video below.

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Open-Source Grinder Makes Compression Screws For Plastic Extruders Easy

In a world that’s literally awash in plastic waste, it seems a pity to have to buy fresh rolls of plastic filament to feed our 3D-printers, only to have them generate yet more plastic waste. Breaking that vicious cycle requires melding plastic recycling with additive manufacturing, and that takes some clever tooling with parts that aren’t easy to come by, like the compression screws that power plastics extruders.

This open-source compression screw grinder aims to make small-scale plastic recyclers easier to build. Coming from the lab of [Joshua Pearce] at the Michigan Technological University in collaboration with [Jacob Franz], the device is sort of a combination of a small lathe and a grinder. A piece of round steel stock is held by a chuck with the free end supported by bearings in a tailstock. On the bed of the machine is an X-Y carriage made of 3D-printed parts and pieces of electrical conduit. The carriage moves down the length of the bed as the stock rotates thanks to a pulley and a threaded rod, carrying a cordless angle grinder with a thick grinding wheel. A template attached to the front apron controls how deep the grinder cuts as it tracks along the rod; different templates allow the screw profile to be easily customized. The video below shows the machine in action and the complicated screw profiles it’s capable of producing.

We’ve seen lots of homebrew plastic extruders before, most of which use repurposed auger-type drill bits as compression screws. Those lack the variable geometry of a proper compression screw, so [Joshua] and [Jacob] making all the design documents for this machine available should be a boon to recycling experimenters.

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Hackaday Links: November 24, 2019

It barely seems like it, but it’s been a week since the 2019 Hackaday Superconference wrapped up in sunny Pasadena. It was an amazing weekend, filled with fun, food, camaraderie, and hacks galore. For all who were there, it’ll likely take quite some time before spinning down to Earth again from the post-con high. For those who couldn’t make it, or for those who did but couldn’t squeeze in time for all those talks with everything else going on, luckily we’ve got a ton of content for you to review. Start on the Hackaday YouTube channel, where we’ve got videos already posted from most of the main stage talks. Can’t-miss talks include Chris Gammell’s RF deep-dive, Kelly Heaton’s natural electronic art, and Mohit Bhoite’s circuit sculpture overview. You’ll also want to watch The State of the Hackaday address by Editor-in-Chief Mike Szczys. More talks will be added as they’re edited, so watch that space for developments.

One of the talks we missed – and video of which appears not to be posted yet – was Adam Zeloof’s talk on thermodynamic design for your circuits. While we wait for that, here’s an interesting part that might prove useful for your next high-power design. It’s a Thermal Jumper Chip, which is essentially a ceramic SMD component that can conduct heat but not electricity. It’s intended to be used where a TO-220 case needs to be electrically isolated but thermally connected to a heatsink. Manufacturer TT Electronics has a whole line of the chips in various sizes and specs, plus a lot of other cool components like percussive igniters.

We got an interesting tip this week about a new development in the world of 3D-printing. A group from Harvard demonstrated a multinozzle extruder that can print multimaterial objects in a single pass. The work is written up in a Nature article entitled “Voxelated soft matter via multimaterial multinozzle 3D printing”, which is unfortunately paywalled, but the abstract and supplementary videos are really interesting. This appears not to be a standard hot plastic extrusion process; rather, the extruder uses elastomeric inks that cure after they’re extruded. They manage some clever tricks, including a millipede-like, vacuum-powered soft robot extruded in one pass from both soft and rigid silicone elastomers. It’s genuinely interesting stuff, and watching the multimaterial extruder head switch materials at up to 50 times per second is mesmerizing.

People really seemed to get worked up over the transit of Mercury across the face of the Sun last week, and for good reason – astronomical alignments such as these which can be seen from Earth are rare indeed, and worth taking time to see. Not everyone was in the right place at the right time with the right gear to view the transit directly, though, which is why we were glad that Justin over at The Thought Emporium did a video on leveraging online assets for space-based observations. We’ve featured a ton of hacks using SDRs and the like to intercept data from weather satellites, and while those hacks are fun and you should totally try them, Justin points out that most of these streams are readily available for free over the Internet. Clouds, lightning, forest fires and Earth changes, and yes, even the state of the Sun can all be monitored from the web.

Speaking of changes, do you know what has changed in Unix over the last 50 years? For that matter, did you know that Unix turned 50 recently? Sean Haas did after reading this article in Advent of Computing, which he shared on the tipline. The article compares a modern Debian distro to documentation from 1971 that pre-dates Unix version 1; we assume the “Dennis_v1” folder in the doc’s URL refers to none other than Dennis Ritchie himself. It turns out that Unix is remarkably well-conserved over 50 years, at least in the userspace. File system navigation and shell commands are much the same, while programming was much different. C didn’t yet exist – Dennis was busy – but there were assemblers and linkers, plus a FORTRAN compiler and an interpreter for BASIC. It’s comforting to know that if you drop into a wormhole and end up sitting in front of a PDP-11 with Three Dog Night singing “Joy to the World” on the radio in the background, you’ll at least be able to look like you belong there.

And finally, it’s nearly Sparklecon time again. Sparklecon VII will be held on January 25 and 26, 2020, at the 23b Shop hackspace in Fullerton, California. We’ve covered previous Sparkelcons and we’ve even sponsored the meetup in the past, and it looks like a blast. The organizers have put out a Call for Proposals for talks and workshops, so if you’re in the mood for some mischief, get your application going. And be quick about it – the CFP closes on December 8.

No Filament Needed In This Direct Extrusion 3D-Printer

Ground plastic bits go in one end, finished 3D-prints come out the other. That’s the idea behind [HomoFaciens]’ latest build: a direct-extrusion 3D-printer. And like all of his builds, it’s made from scraps and bits most of us would throw out.

Pellet agitator is part of the extruder. All of this travels along with the print head.

Take the extrusion screw. Like the homemade rotary encoders [HomoFaciens] is known for, it appears at first glance that there’s no way it could work. An early version was just copper wire wrapped around a threaded rod inside a Teflon tube; turned by a stepper motor, the screw did a decent job of forcing finely ground PLA from a hopper into the hot end, itself just a simple aluminum block with holes drilled into it. That worked, albeit only with basically powdered PLA. Later versions of the extruder used a plain galvanized woodscrew soldered to the end of a threaded rod, which worked with chunkier plastic bits. Paddles stir up the granules in the hopper for an even flow into the extruder, and the video below shows impressive results. We also picked up a few tips, like using engine gasket paper and exhaust sealant to insulate a hot end. And the slip coupling, intended to retract the extruder screw slightly to reduce stringing, seems brilliant but needs more work to make it practical.

It’s far from perfect, but given the inputs it’s pretty amazing, and there’s something attractive about reusing all those failed prints. It reminds us a bit of the trash printer we featured recently, which is another way to stick it to the filament man. Continue reading “No Filament Needed In This Direct Extrusion 3D-Printer”