Casting A Simple 3D Print In Aluminium

June 25, 2021 by Lewin Day 21 Comments

3D printing with plastics and resins is great for quickly prototyping parts with all manner of geometries, but strength and durability of the parts produced is often limited. One way around this is to use your 3D printed parts as patterns for casting in something tougher like aluminium. That’s precisely what [Brian Oltrogge] did to produce an attractive wall hook from a 3D printed design.

The process starts with the design and printing of a wall hook, with [Brian] taking care to include the proper draft angles to allow the pattern to be properly removed from the mold. The print is carefully sanded down and post-processed to be highly smooth, so that it doesn’t spoil the mold when its removed for the casting process. From there, a sand casting mold is built around the pattern using sodium silicate in a 3-4% mix by weight with fine masonry sand. Once ready, the pattern is removed, and the mold is assembled, ready for the pour.

[Brian] completes the process with a simple gravity casting method using molten aluminium. The part is then removed from the mold, and filed down to improve the surface finish from the sand casting process. It’s then polished up to a nice shine and hung on the wall.

[Brian] does a great job of explaining the basics of what it takes to get gravity casting right; draft angles in particular are something often ignored by beginners, yet are crucial to getting good results. You needn’t just settle for casting inanimate objects though; we’ve featured DIY casting processes for gears before, too. Video after the break.

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Active Ball Joint Uses Spherical Gear

June 24, 2021 by Al Williams 41 Comments

A common CAD operation is to take a 2D shape and extrude it into a 3D shape. But what happens if you take a gear and replicate it along a sphere and then rotate it and do it again? As you can see in the video below, you wind up with a porcupine-like ball that you can transfer power to at nearly any angle. There’s a paper describing this spherical gear as part of an active ball joint mechanism and even if you aren’t mechanically inclined, it is something to see.

The spherical gear — technically a cross spherical gear — is made from PEEK and doesn’t look like it would be that difficult to fabricate. There’s also a simpler version known as a monopole gear in the drive system that provides three degrees of freedom.

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Print Your Own Flexures

June 22, 2021 by Chris Lott 12 Comments

Game developer and eternal learner [David Tucker] just posted a project where he’s making linear flexures on a 3D printer. Tinkerer [Tucker] wanted something that would be rigid in five of the six degrees of freedom, but would provide linear motion along one axis. In this case, it is for a pen or knife on a CNC flatbed device. [David]’s design combines the properties of a 1-dimensional flexure and a spring to give a constant downward force. Not only is this an interesting build in and of itself, but he gives a good explanation and examples of more traditional flexible constructs. He also points out this site by MIT Precision Compliant Systems Lab engineer [Marcel Thomas] which provides a wealth of information on flexures.

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3D Printing Food University Style

June 18, 2021 by Al Williams 5 Comments

While refitting a 3D printer for food printing isn’t really a new idea, we liked the detailed summary that appeared from a team from the University of Birmingham which converted an i3 clone printer to use a syringe extruder.

The syringe in question was meant for veterinarian use and is made of metal. The paper suggests that the metal is a better thermal conductor, but it was’t clear to us if they included a heating element for the syringe. In the pictures, though, it does appear to have some insulation around it. In any case, we imagine a metal syringe is easier to keep clean, which is important if you are depositing something edible.

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Printed Catamaran

June 15, 2021 by Al Williams 8 Comments

If you want to send some instruments out on the lake or the ocean, you’ll want something that floats. Sure, if you need to be underwater, or if you can fly over the water there are other options, but sometimes you want to be on the surface. For stability, it is hard to beat a catamaran — a boat with two hulls that each support one side of a deck. If that sounds like the ocean sensor platform of your dreams, try printing the one from [electrosync].

The boat looks super stable and has a brushless motor propulsion system. The design purpose is to carry environmental and water quality monitoring gear. It can hold over 5 kg of payload in the hull and there’s an optional deck system, although the plans for that are not yet included in the STL files.

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Smooth 3D Prints With Alcohol

June 14, 2021 by Al Williams 26 Comments

There was a time when most 3D printers used ABS, which is a great plastic for toughness, but is hard to print with since it tends to warp. Worse still, it stinks and the fumes may be bad for you. Most people have switched over to printing in PLA these days, but one thing you might miss with this more forgiving plastic is vapor smoothing with acetone; a smoothed print doesn’t show layer lines and looks more like plastic part that didn’t go through a nozzle.

[Major Hardware] likes the look of vapor smoothed parts, but doesn’t like working with ABS and acetone fumes, so he’s started using Polysmooth. As you can see in the video below, the results look good, but be warned that the filament is relatively pricey. Plus you need to use a $300 machine that atomizes your alcohol into a mist. We feel certain you could do the same thing for less since it appears to just be like a humidifier, but we’d also suggest being careful putting flammable substances in a consumer-grade humidifier and certainly don’t use a vaporizer.

The filament sounds like it is on par with PLA for ease of printing. The material has a higher glass temperature than PLA but less than ABS. The tensile strength and Young’s modulus (a measure of stiffness) numbers are comparable to ABS. Although all smoothing has some imperfections and you probably need to experiment with times and other parameters. The smoothing did fuse some movable joints, so anything that moves or fits together is probably a bad candidate for this process. We’ve also heard that thin-walled parts can get soft in water due to alcohol residue, but you can dry or soak the part clean to avoid that.

If you want to try your own hand at making a mist, this might get you started. After all, if it can handle acetone, we imagine alcohol isn’t any worse. While it isn’t as easy to handle as alcohol, we hear the solvents such as THF or ethyl acetate can smooth regular PLA. Heat guns and open flames are popular, too.

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Recore Hacks The Hidden Microcontroller For 3D Printing

June 14, 2021 by Chris Lott 24 Comments

No stranger to the world of 3D printers, [Elias Bakken] from the [Intelligent Agent] workshop has released a new controller board called Recore. The typical 3D printer has a dedicated controller which handles the real-time aspects of driving stepper motors. Many setups also have a second computer, often Linux-based, which is dedicated to supporting tasks like running an Octoprint server and interfacing to a digital camera to monitor print progress remotely. [Elias]’s design merges these together into one compact 12 x 12 x 4 cm package.

The Recore board is powered by an AllWinner A64 system on chip (SoC) which packs four ARM Cortex-A53 AArch64 cores running Debian Linux. The applications include Klipper, a project we wrote about when it was first introduced, and the OctoPrint print server. “But Linux is not a real-time operating system”, we hear you cry, “and controlling stepper motor drivers from an A64 SoC is just asking for trouble”. [Elias] could have addressed this problem by putting a secondary microcontroller on the board, but he found an even more elegant solution instead.

It turns out that there is already a secondary microcontroller hidden in plain sight, integrated into the A64 itself. See that small box labeled AR100 at the top of the block diagram? Meet the AR100, a controller originally intended to manage low-power operations of the A64. It is an OpenRISC 32-bit OR1k processor. But the AR100 is extremely underutilized, and [Elias] takes good advantage of this by repurposing it to those real-time tasks associated with a 3D printer controller. Watch the short video down below to learn how he solves a few of the nitty-gritty implementation details such as timers and communicating with the Linux processors. You might learn some tips from the other short videos in the series featuring some interesting debugging and problem solving sessions. There is a project GitHub repository and a Wiki full of good information and testing results.

[Elias] has a long history of building printer controllers. While his last one had to be abandoned because of manufacturing issues, he learned from that experience. Manufacturability was a top priority in the design of the Recore. We’re jealous of the well-appointed [Intelligent Agent] facility in Norway, but even more so of the nomadic lifestyle that [Elias] appears to enjoy — in his videos, he can be seen working from far-flung locales such as a tropical island resort and a laboratory floating in high Earth orbit. We’ve featured [Elias]’s projects in the past, including the Replicate 3D printer controller, a semi-automatic liquor cabinet, and the dog-operated treat dispenser.

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