Cleaner Laser Cutting With A 3D-Printed Nozzle

November 25, 2020 by Donald Papp 24 Comments

[Nervous System] does a lot of laser cutting, and [Jesse] shared a fascinating experimental improvement to their laser cutter that consists of a 3D-printed nozzle for cleaner cuts. You can see the results for yourself above, where the difference between the two cuts is striking.

[Jesse]’s modification doesn’t affect the laser beam itself; it is an improvement on the air assist, which is the name for a constant stream of air that blows away smoke and debris as the laser burns and vaporizes material. An efficient air assist is one of the keys to getting nice clean laser cuts, but [Jesse] points out that a good quality air assist isn’t just about how hard the air blows, it’s also about how smoothly it does so. A turbulent air assist can make scorch marks worse, not better.

3D-printed nozzle to promote laminar air flow on the left, stock nozzle on the right.

As an experiment to improve the quality of the air flowing out the laser nozzle, [Jesse] researched ways to avoid turbulence by creating laminar flow. Laminar flow is the quality of a liquid having layers flowing past one another with little or no mixing. One way to do this is to force liquid through individual, parallel channels as it progresses towards a sharply-defined exit nozzle. While [Jesse] found no reference designs of laminar flow nozzles for air assists, there were definitely resources on making laminar flow nozzles for water. It turns out that interest in such a nozzle exists mainly as a means of modifying Lonnie Johnson’s brilliant invention, the Super Soaker.

Working from such a design, [Jesse] created a custom nozzle to help promote laminar flow. Sadly, a laser cutter head carries design constraints that make some compromises unavoidable; one is limited space, and another is the need to keep the laser’s path unobstructed. Still, after 3D printing it in rigid heat-resistant resin, [Jesse] found a dramatic improvement in the feel of the air exiting the nozzle. Some test cuts confirmed a difference in performance, which results in a noticeably cleaner kerf without scorching around the edges.

One of the things [Nervous System] does is make their own custom puzzles, so any improvement to laser cutting helps reliability and quality. When production is involved, just about everything matters; a lesson [Nervous System] shared when they discussed making the best plywood for creating their puzzles.

Big Nerf Bazooka Packs A Wallop

November 20, 2020 by Lewin Day 4 Comments

Nerf blasters are a fun toy, often confiscated from children once they hit one too many precious ornaments around the home in the midst of battle. [Ivan Miranda] is bigger than most children however, and set about building a much larger blaster.

The bazooka-like design uses a several meters of 160mm PVC pipe, firing “darts” constructed out of foam yoga rollers and buffing pads. The build uses a littany of 3D printed components in its construction, both as part of the firing mechanism and as jigs to help machine the pipe. A large plunger is used to propel the darts, which is pulled back against the tension of thick rubber tubes before being released by the trigger mechanism.

It’s an intimidating device, to be sure. However, we suspect its short range, huge size, and slow reload time should stop it from breaking the meta-game at your local Nerf battles. That said, we still wouldn’t want to take a shot from this bad boy to the head. Hackers do love a good Nerf build, and they’re particularly popular in sentry applications. Video after the break.

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3D Printable Cloth Takes Advantage Of Defects

November 20, 2020 by Al Williams 24 Comments

Normally, a 3D printer that under extrudes is a bad thing. However, MIT has figured out a way to deliberately mix full extrusions with under extruded layers to print structures that behave more like cloth than normal 3D printed items. The mesh-like structure apparently doesn’t require any modification to a normal 3D printer, just different software to create special code sequences to create the material.

Called DefeXtiles, [Jack Forman] is producing sheets and complex structures that appear woven. The process is known as “blob-stretch” because of the way the plastic makes blobs connected by fine filaments of plastic.

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3D Printer Lets You Play “Will It Shred?”

November 19, 2020 by Mike Szczys 22 Comments

[Brian Brocken] is at it again, building mechanisms that are as striking in their aesthetic as they are in their function. This time around, he’s extended a project we recently featured by adding a menacing 3D-printed shredder attachment. When you hear “3D-printed shredder” you think that paper is all you’ll be able to feed it, but this beast can eat its own by shredding parts from failed prints.

His original goal in building the high-torque 3D-printed gear box we looked at back in August was to show that 3D printed parts can be functional and not merely decorative. Using it as a winch to pull a car did a good job of that, but this goes much further. The very nature of shredder blades is to tear apart objects, but the forces that destroy those things are also present on the shredder parts themselves. Still, as you can see in the video below, the counter-rotating twin-shaft shredder mechanism does its work without catastrophic damage to the blades which were printed with “least 25 percent infill for the structural parts”, and up to five outer perimeters.

The result is a shredder that can gobble up small pieces of failed prints, in addition to chewing on paper, cardboard, and polystyrene with ease. [Brian] does show a few failures along the way, all in the gearbox itself. The first was a defect in the housing that let an gear shaft pop loose and was fixed up with a reprint. The second is a catastrophic gear failure when trying to shred a soda bottle. This is not surprising as PET is quite tough and not brittle like the waste prints were. The shredder teeth got bogged down, and the power of the motor strips teeth from a few gears. But when working, it’s oddly satisfying to watch that powerful gear ratio chip away at sacrificial materials.

If you’re more on the prowl for a way to usefully recycle your plastics, set the 3D-printed stress test of this one aside and take a look at the plastic shredder Fablab RUC built out of metal and plywood a few years back.

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More LEDs Means Faster Print Times For 3D Printer, But There’s A Catch

November 18, 2020 by Donald Papp 13 Comments

[Jan Mrázek] is no stranger at all to home-grown improvements with his Elegoo Mars SLA 3D printer, and there is a lot going on in his experimental multi-LED upgrade which even involved casting his own lens array. In the end it did speed up his prints by a factor of three to four, though he cooked an LCD to failure in the process. Still, it was a fun project done during a COVID-19 lockdown; as usual there is a lot to learn from [Jan]’s experiences but the mod is not something he necessarily recommends people do for themselves.

[Jan] started by wondering whether better print quality and performance could be obtained by improving the printer’s UV light source. The stock printer uses a single large UV LED nestled into a reflector, but [Jan] decided to try making a more precise source of UV, aiming to make the UV rays as parallel as possible.

To do this, he took a two-pronged approach. One was to replace the single large UV LED with a 4×7 array of emitters plus heat sink and fans. The other was to make a matching array of custom lenses to get the UV rays as parallel as possible.

Casting one’s own lens array out of clear epoxy was a lot of work and had mixed results, but again, it was a lockdown project and the usual “is-this-really-worth-it” rules were relaxed. In short, casting a single custom lens out of clear epoxy worked shockingly well, but when [Jan] scaled it up to casting a whole 4×7 array of them, results were mixed. Mold deformation and artifacts caused by the areas between individual lenses robbed the end result of much of its promise.

More success was had with the array of UV emitters, which enabled faster curing thanks to higher power, but the heat needs to be managed. The stock emitter of the printer is about 30 W, and [Jan] was running his new array at 240 W. This meant a blazing fast one second exposure time per layer, but the heat generated by the new lighting was higher than anticipated. After only ten hours the LCD failed, probably at least in part due to the heat. [Jan] halved the power of the array down to 120 W and added an extra fan, which appears to have done the trick. Exposure time is two to three seconds per layer, and it’s up to 150 hours of printing without problems.

Again, it’s not a process [Jan] necessarily recommends to others (and he definitely recommends buying lenses if at all possible instead of casting them) but as usual there is a lot to learn from his frank sharing of results, both good and bad. We’ve seen 3D-printed lenses as well as adding WiFi connectivity to one of these hobbyist printers, and it’s great to see the spirit of hacking alive and well when it comes to these devices.

Prusa Mini Gets Custom Heavy Duty Enclosure

November 17, 2020 by Tom Nardi 15 Comments

Still waiting on your Prusa Mini to arrive? Join the club. Between the incredible amount of interest in the inexpensive 3D printer and the COVID-19 pandemic, it can take months for the machine to arrive at your doorstep. But patient makers are finally taking delivery of their new printers, and as such the hacks and modifications are starting to trickle their way in.

First up is this gloriously over-engineered enclosure from [Build Comics]. While PLA and PETG usually print fine with nothing more exotic than a heated bed, trickier materials like ABS work best when the printer is enclosed as it helps maintain a consistent temperature. Plus it keeps any curious hands and paws a safe distance from the hot moving bits, and if things go really pear-shaped, can help contain smoke and flames.

The enclosure is made from welded steel square tube, wood, and fire-retardant fiber board. A hinged polycarbonate cover, taking the form of a four-sided cube, is lowered over the printer with some heavy-duty hinges that look like they were intended for a fence. To keep the cover from slamming back down, [Build Comics] came up with a simple locking mechanism that can easily be operated from the front or side of the enclosure. With the addition of a small temperature and humidity display, the conditions inside the chamber can easily be monitored.

But [Build Comics] didn’t stop there. He also rigged up a relay box that will cut power to the printer should the smoke detector mounted above it trip. While there’s no reason to think the Prusa Mini would suffer the same fate of earlier budget desktop 3D printers, but there’s certainly no harm in taking precautions.

Will you need to build a similar enclosure whenever your Prusa Mini shows up? Maybe not. But if you felt so inclined, at least now you’ve got plenty of images and details that can help you spin up your own solution.

FreeCAD Debugging

November 16, 2020 by Al Williams 20 Comments

Powerful software programs often have macro programming languages that you can use, and if you know how to program, you probably appreciate them. However, sometimes the program’s built-in debugging facilities are lacking or even nonexistent If it were just the language, that wouldn’t be such a problem, but you can’t just grab a, for example, VBA macro from Microsoft Word and run it in a normal Basic interpreter. Your program will depend on all sorts of facilities provided by Word and its supporting libraries. [CrazyRobMiles] was frustrated with trying to debug Python running inside FreeCAD, so he decided to do something about it.

[Rob’s] simple library, FakeFreeCad, gives enough support that you can run a FreeCAD script in your normal Python development environment. It only provides a rude view of what you are drawing, but it lets you explore the flow of the macro, examine variables, and more.

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