PCTG Filament Has Interesting Properties

March 24, 2021 by Al Williams 37 Comments

Early 3D printers used ABS, but bad fumes and warping made most people go to PLA. However, PETG has a lot of the great properties of ABS along with some of the ease-of-use of PLA. According to a recent [VisionMiner] video, however, PCTG — Polyethylene Terephthalate-Glycol — could be the next filament of choice. The filament itself is from Essentium, but it appears that [VisionMiner] is a reseller of the filament (along with other engineering plastics). Thus the video below has a bit of marketing speak in it, but it also has good information and examples of using PCTG.

The plastic is relatively inexpensive, but still not as cheap as PLA or even PETG. A 750g roll is about $40 The benefits? According to the video, this plastic is stronger, tougher, and clearer than other common options.

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3D Printed Vortex Cooled Rocket Needs To Stop Leaking

March 23, 2021 by Lewin Day 27 Comments

Rocket engines are known for one thing above all else, and that’s getting hot. It’s this very property that makes them such a challenge to build and run from a materials engineering standpoint. It’s hard enough to build one with advanced metal alloys, but [Integza] presses on with trying to make one on a 3D printer. Progress is being made, but success remains elusive. (Video, embedded below.)

To try and mitigate the thermal effects of burning propellants in his engine design, [Integza] looked to vortex cooling. This is where oxygen is swirled around the outer edge of the combustion chamber in a vortex, acting as a buffer layer between the burning fuel and the chamber walls. With 3D printed chamber components, keeping temperatures as low as possible is key, after all. Unfortunately, despite using a special ceramic-laden resin for printing and lathering the rocket components in various refractory materials, it wasn’t possible to stop the chambers leaking. Solid combustion was possible for a few seconds at a time, but eventually each motor tested turned into a ball of flames as the walls broke down.

Thankfully, nobody was hurt in testing, and [Integza] has a clear idea of the problems that need to be fixed in the next iteration. We’ve featured other vortex cooled rockets before – the theory is sound. As always, the devil is in the implementation.

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Get A Better Look At E3D’s Tool-changing 3D Printer Kit

March 20, 2021 by Donald Papp 4 Comments

Want a closer, in-depth look at E3D’s motion system and tool-changing platform? [Kubi Sertoglu] shared his impressions after building and testing the system, which comes in the form of a parts bundle direct from E3D costing just under $3000 USD. The project took [Kubi] about 15 hours and is essentially built from the ground up. The system is definitely aimed at engineers and advanced prosumers, but [Kubi] found it to be of remarkable quality, and is highly pleased with the end results.

E3D Motion system and toolchanger, with four extruders

We first saw E3D’s design announced back in 2018, when they showed their working ideas for a system that combined motion control and a toolchanger design. The system [Kubi] built uses four 3D printing extruders for multi-material prints, but in theory the toolheads could just as easily be things like grippers, lasers, or engravers instead of 3D printing extruders.

One challenge with tool changing is ensuring tools mount and locate back into the same place, time after time. After all, a few fractions of a millimeter difference in the position of a print head would spell disaster for the quality of most prints. Kinematic couplings are the answer to being sure something goes back where it should, but knowing the solution is only half the battle. Implementation still requires plenty of clever design and hard engineering work, which is what E3D has delivered.

Want a closer look at the nitty-gritty? Check out E3D’s GitHub repository for all the details on their toolchanger and motion system.

Experimenting With 3D Printed Rocket Nozzles

March 17, 2021 by Lewin Day 7 Comments

Rocketry is an exacting science, involving a wide variety of disciplines, encompassing everything from fluid mechanics to thermodynamics and materials engineering. As complex as it sounds, that doesn’t mean it’s beyond the purview of the average maker. [Sciencish] demonstrates this with a series of experiments on rocket nozzles in the home lab. (Video, embedded below.)

The video starts with an amusing analogy about nozzle design based on people fleeing a bad pizza. From there, [Sciencish] 3D prints a wide variety of nozzle designs for testing. The traditional bell nozzle is there, of course, along with the familiar toroidal and linear aerospikes and an expansion deflection design. Of course, 3D printing makes it easy to try out fun, oddball geometries, so there’s also a cowbell nozzle , along with the fancy looking square and triangular aerospikes too. Testing involves running the nozzles on a test stand instrumented with a load cell. A soda bottle is filled with rubbing alcohol vapour, and the mixture is ignited, with each nozzle graded on its thrust output. The rockets are later flown outside, reaching heights over 40 feet.

[Sciencish] notes that the results are a rough guide only, as the fuel/air mixture was poorly controlled. Despite this, it’s a great look at nozzle design and all the science involved. It also wouldn’t be too hard to introduce a little more rigour and get more accurate data, either. However, if solid fuels are more your jam, consider brewing up some rocket candy instead.

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Photorender Your 3D Models

March 15, 2021 by Al Williams 7 Comments

Of course, you’ll want to take your latest 3D design and print it so you’ll have a physical object. But in some cases, you’d like to have a rendering of it. If you use OpenSCAD, FreeCAD, or most other CAD programs you can get a simple rendering of your object, but what if you want something that looks real? [Teaching Tech] shows how you can use a website, Vectary, to get realistic photo renderings of your 3D models. (Video, embedded below.) The free plan has a few limits, but nothing that should bother most people.

Vectary is sort of like a super version of TinkerCad with a lot of options for realistic modeling and augmented reality. Some of the more advanced features are behind a subscription plan, but for what [Teaching Tech] is showing, you can use the free plan.

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Motorcycle Needs Custom Latching Switches For Turn Signals

March 13, 2021 by Bryan Cockfield 42 Comments

While modern cars have been getting all kinds of fancy features like touch screens, Bluetooth, crumple zones, and steering wheel controls, plenty of motorcycles have remained firmly in the past. Some might have extra options like a fuel gauge or even ABS if you’re willing to spend extra, but a good percentage of them have the bare minimum equipment required by law. That equipment is outdated and ripe for some improvements too, like this ergonomic custom turn signal switch built with custom latching switches.

Since motorcycle turn signals don’t self-cancel like car signals the rider has to cancel it themselves, usually by pushing an inconveniently tiny button. This assembly consists of four separate switches, two of which control the left and right turn signals. Since both can’t be on at the same time, they include circuitry that can detect their position and a small motor that can physically de-latch them if the other one is pressed. The entire assembly is 3D printed, including the latching mechanism, and they are tied together with a small microcontroller for the controls.

The truly impressive part of this build is the miniaturization, since all four buttons have to be reached with the thumb without removing the hand from the handlebar. The tiny circuitry and mechanical cam for latching are impressive and worth watching the video for. And, if you need more ergonomic improvements for your motorcycle there are also some options for cruise control as well, another feature often lacking in motorcycles.

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A Different Kind Of 3D Printer: Desktop Holograms

March 12, 2021 by Al Williams 38 Comments

Holograms aren’t new, but a desktop machine that spits them out could be available soon, presuming LitiHolo’s Kickstarter pans out. The machine will have a $1600 retail price and fits in a two-foot square. It can generate 4×5 inch holograms with 1mm hogels (the holo equivalent of a pixel).

The machine allows for 23 view zones per hogel and can create moving holograms with a few seconds of motion — like the famous kiss-blowing holograms.

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