SLA 3D Printed Vortex Cooled Rocket Engine

3D printing is an incredible tool for prototyping and development, but the properties of the materials can be a limiting factor for functional parts. [Sam Rogers] and colleagues at [AX Technologies] have been testing and developing a small liquid-fueled rocket engine and successfully used vortex cooling to protect a resin 3D printed combustion chamber. (Video, embedded below.)

Vortex cooling works by injecting oxygen into the combustion chamber tangentially, just inside the nozzle of the engine, which creates a cooling, swirling vortex boundary layer along the chamber wall. The oxygen moves to the front end of the combustion chamber where it mixes with the fuel and ignites in the center. This does not protect the nozzle itself, which only lasts a few seconds before becoming unusable. However, thanks to the modular design of the test engine, only the small nozzle section had to be reprinted for every test. While this part could be manufactured using a metal 3D printer, the costs are still very high, especially at this experimental stage. The clear resin parts also allow the combustion observed and more accurate conclusions to be drawn from every test.

This engine intended to be used as a torch igniter for a much larger rocket engine. Fuel is injected into the front of the combustion chamber, where a spark plug is located to ignite the oxygen-fuel mixture. The flow of the oxygen and fuel is controlled by two servo-operated valves connected to a microcontroller, which is mounted with the engine on linear rails. This allows the test engine to move freely, and push against a load cell to measure thrust. The spark is created before the valves are opened to prevent a delayed ignition, which can blow up the engine, and getting the valve sequence and timing correct is critical. Many iterations and destroyed parts later, the [AX Technologies] team achieved successful ignition, with a clear supersonic Mach diamond pattern in the exhaust.

This is just one more example of 3D printing and cheap electronics allowing impressive progress on a limited budget. Another example is [Joe Barnard]’s progress in getting a model rocket to land itself with a solid fuel engine. Companies and organisations have been using 3D printed components in rocket engines for a few years now, and we’ve even seen an open source version.

Improving Exposure On A Masked SLA Printer

It’s taken longer than some might have thought, but we’re finally at the point where you can pick up an SLA 3D printer for a few hundred bucks. These machines, which use light to cure a resin, are capable of far higher resolution than their more common FDM counterparts, though they do bring along their own unique issues and annoyances. Especially on the lower end of the price spectrum.

[FlorianH] recently picked up the $380 SparkMaker FHD, and while he’s happy with the printer overall, he’s identified a rather annoying design flaw. It seems that the upgraded UV backlight in the FHD version of the SparkMaker produces somewhat irregular light, which in turn manifests itself as artifacts on the final print. Due to hot spots on the panel, large objects printed on the SparkMaker show fairly obvious scarring.

Now you might expect the fix for this problem to be in the hardware, but he’s taken it in a different direction. These printers use an LCD panel to block off areas of the UV backlight, thereby controlling how much of the resin is exposed. This is technique is officially known as “masked SLA”, and is the technology used in most of these new entry level resin printers.

As luck would have it, the SparkMaker FHD allows showing various levels of grayscale on the LCD rather than a simple binary value for each pixel. At least in theory, this allows [FlorianH] to compensate for the irregular backlight by adjusting how much the UV is attenuated by the LCD panel. He’s focusing on the printer he personally owns, but the idea should work on any masked SLA printer that accepts grayscale values.

The first step was to map the backlight, which [FlorianH] did by soaking thin pieces of paper in a UV reactant chemical, and draping them over the backlight. He then photographed the illumination pattern, and came up with some OpenCV code that takes this images and uses the light intensity data to compensate for the local UV brightness underneath the sliced model.

So far, this method has allowed [FlorianH] to noticeably reduce the scarring, but he thinks it’s still possible to do better. He’s released the code for this backlight compensation script, and welcomes anyone who might wish to take a look at see how it could be improved.

An uneven backlight is just one of the potential new headaches these low-cost “masked” SLA printers give you. While they’re certainly very compelling, you should understand what you’re getting into before you pull the trigger on one.

What Actually Happens At A Hardware Hacking Con

The Hackaday Superconference was last weekend, and it was the greatest hardware con on the planet. What can you build out of a conference badge? If you answered “a resin-based 3D printer” you would have won a prize. If you decided to put your badge in a conference water bottle and make a stun gun you’d receive adoration of all in attendance. Yeah, it got that crazy.

Yes, there’s a Supercon badge in that bottle and it’s now a stun gun.

At other tech conferences, you’ll find gaggles of nerds sitting around a table with MacBooks and Thinkpads. The Superconference is different. Here, you’ll find soldering irons, tackle boxes filled with components, and loose WS2812s scattered about the floor. The smell of solder flux wafts through the air. You detect a hint of ozone.

The depth and breadth of hacks that came out of this were simply stunning. We a binocular virtual reality hack, an internet trolling badge, blinky add-on boards, audio add-on boards, a film festival was shot on the badge, and much more which you’ll find below.

We have started a Badge Hacks list and want to see details of all of the hacks. So if you were at Supercon be sure to publish them on and send a DM to be added to the list.

Starting Up An Extra Day of Hacking

To get all of this creativity rolling we did something a bit different for this year’s Superconference. Instead of opening the doors up on Saturday morning, we set up a badge hacking area and party on Friday afternoon. The drinks flowed like the meniscus on a properly soldered lead, and by 2pm on Friday, everyone was hacking firmware on the incredible camera badge for this year’s con.

We didn’t stop on Friday. The Superconference is a hardware hacking conference, and that meant we brought out the soldering irons, experimented with melting aluminum with gallium, reflowed a few boards, and created a few deadbug LED cubes. This went on all weekend.

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3D Printed Nozzles Turbocharge Microsphere Production

Researchers at MIT have used 3D printing to open the door to low-cost, scalable, and consistent generation of microencapsulated particles, at a fraction of the time and cost usually required. Microencapsulation is the process of encasing particles of one material (a core) within another material (a shell) and has applications in pharmaceuticals, self-healing materials, and dye-based solar cells, among others. But the main problem with the process was that it was that it was slow and didn’t scale, and it was therefore expensive and limited to high-value applications only. With some smart design and stereolithography (SLA) 3D printing, that changed. The researchers are not 3D printing these just because they can; they are printing the arrays because it’s the only way they can be made.

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Open Source SLA Printer Software Slices From The Browser

Resin-based SLA printers need a different slicing algorithm from “normal” melted-plastic printers. Following their latest hackathon, [Matt Keeter] and [Martin Galese] from Formlabs have polished off an open source slicer, and this one runs in your browser. It’s Javascript, so you can go test it out on their webpage.

Figuring out whether or not the voxel is inside or outside the model at every layer is harder for SLA printers, which have to take explicit account of the interior “empty” space inside the model. [Matt] and [Martin]’s software calculates this on the fly as the software is slicing. To do this, [Matt] devised a clever algorithm that leverages existing hardware to quickly accumulate the inside-or-out state of voxels during the slicing.

[Matt] is stranger to neither 3D mesh manipulation nor Hackaday. If you’re just getting started in this realm, have a look at Antimony, [Matt’s] otherworldly CAD software with a Python interface to get your feet wet with parametric 3D modeling.

OpenExposer, The DIY SLA Printer


Precisely applied ultraviolet light is an amazing thing. You can expose PCBs, print 3D objects, and even make a laser light show. Over on the Projects site, [Mario] is building a machine that does all of these things. It’s called the OpenExposer, and even if it doesn’t win the Hackaday Prize, it’s a great example of how far you can go with some salvaged electronics and a 3D printer.

The basic plan of the OpenExposer is a 3D printer with a small slit cut into the bed, and a build platform that moves in the Z axis. The bed contains a small UV laser and a polygon mirror ripped from a dead tree laser printer. By moving the bed in the Y direction, [Mario] shoot his laser anywhere on an XY plane. Put a tank filled with UV curing resin on the bed, and he has an SLA printer. Put a mounting bracket on the bed, and double-sided PCBs are a cinch.

The frame is made of 3D printed parts and standard RepRap rods, with the only hard to source component being the polygonal mirror. These can be sourced from scrounged laser printers, but there’s probably some company in China that will sell them bulk. The age of cheap SLA printers is dawning, friends. Video below, github here.

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