Used Facemasks Turned Into Rapid Antigen Tests With Injection Molding

March 24, 2022 by Dan Maloney 15 Comments

Here’s a little eye-opener for you: next time you’re taking a walk, cast your eyes to the ground for a bit and see how far you can go without spotting a carelessly discarded face mask. In our experience, it’s no more than a block or two, especially if you live near a school. Masks and other disposal artifacts of the COVID-19 pandemic have turned into a menace, and uncounted billions of the things will be clogging up landfills, waterways, and byways for decades to come.

Unless they can be recycled into something useful, of course, like the plastic cases used for rapid antigen tests. This comes to us by way of [Ric Real] from the Design and Manufacturing Futures lab at the University of Bristol in the UK. If any of this sounds or looks familiar, refer back to October when the same team presented a method for turning old masks into 3D printer filament. The current work is an extension of that, but feeds the polypropylene pellets recovered from the old masks into a desktop injection molding machine.

The injection molding machine is fitted with 3D-printed molds for the shells of lateral flow devices (LFD) used for COVID-19 rapid antigen testing. The mold tooling was designed in Fusion 360 and printed on an Elegoo Mars MSLA printer using a high-strength, temperature-resistant resin. The molds stood up to the manual injection molding process pretty well, making good-quality parts in the familiar blue and white colors of the starting material. It’s obviously a proof of concept, but it’s good to see someone putting some thought into what we can do with the megatonnes of plastic waste generated by the pandemic response.

Dog Bowls Show The Versatility Of Ceramic Slip Casting

January 3, 2021 by Dan Maloney 18 Comments

Here at Hackaday, we feature projects that are built of just about every material imaginable. Silicon-spangled fiber-reinforced epoxy resin is our primary medium, but we see plastic, wood, steel, aluminum, and even textiles from time to time. It’s not often we see slip-cast ceramic molding, though, and when it pops up, it’s always good to take a look at this versatile manufacturing method.

The back-story on this one is that [thoughtfulocean], a mechanical engineer idled by COVID lockdowns, wanted custom water bowls for his dogs, one of whom is clearly a grumpy Ewok. The design started with a 3D-print of the final vessel, printed in sections and glued together. These were used to create a two-piece plaster mold into which a watery slurry of clay, or slip, was poured. The plaster mold dehydrates the slip, leaving behind a semi-solid layer of clay of the desired thickness once the excess slip is poured off. The resulting casting is then fired in a kiln and glazed.

Of course, [thoughtfulocean] ran into a few problems along the way. The first mold was warped thanks to the mold box bowing under pressure from the plaster, so the whole molding process had to be revamped. The finished bowl also shrunk less than expected after firing, which led to some more revisions. But the finished bowl look really nice, and the included pump and filter keeps the Ewok’s water free from the yuck a dog’s face can introduce. As a bonus, it sounds like [thoughtfulocean] might have created a marketable product from all this. Take that, COVID!

Slip-casting ceramic may not be all that common around here, but ceramic as a material isn’t exactly a stranger. And who says slip casting is limited to ceramic? After all, we’ve seen a similar method used with plastic resin.

[via r/engineering]

Mixing Up Your Own Supersized Sidewalk Chalk

August 20, 2020 by Brian McEvoy 12 Comments

When folks started quarantining, chalk art spilled onto driveways and sidewalks to remind us that there’s still beauty and creative people doing what they always do. Now it’s time to strut your stuff and show your neighbors that things are greener on your slab of concrete. [friedpotatoes] has shared their giant sidewalk recipe with the world so you can paint the town red. With chalk.

Name brand sidewalk chalk is expensive considering how easy it is to make. What Big Chalk doesn’t want you to know is that the ingredients are just water, plaster of Paris, and tempera paint; meaning this project should be safe enough for the junior hackers to get some hands-on time. Some folks use food coloring instead of paint, but we know what happens to clothing when kids get their mitts on food coloring. [friedpotatoes] also includes extensive repurposing of recyclables, which is commendable.

The instructions suggest filling potato chip (crisp) tubes through a milk jug funnel to make giant pieces, but you can use any mold you like. If you have a CNC machine, it should be no trouble to make stamp-like pieces of chalk for tagging on the go, or shapes like arrows when you have to direct a miniature parade.

For permanent and precise sidewalk decorations, you can check out a graffiti paint machine and for totally temporary messages there is a water-dispensing writer.

Cheap Strain Relief By Casting Hot Glue In A 3D Print

February 11, 2020 by Donald Papp 52 Comments

[Daniel Roibert] found a way to add cheap strain relief to JST-XH connectors, better known to hobby aircraft folks as the charging and balance connectors on lithium-polymer battery packs. His solution is to cast them in hot glue, with the help of 3D printed molds. His project provides molds fitted for connectors with anywhere from two to eight conductors, so just pick the appropriate one and get printing. [Daniel] says to print the mold pieces in PETG, so that they can hold up to the temperature of melted glue.

The 3D models aren’t particularly intuitive to look at, but an instructional video makes everything clear. First coat the inside surfaces of the mold with a release agent (something like silicone oil should do the trick) and then a small amount of hot glue goes in the bottom. Next the connector is laid down on top of the glue, more glue is applied, and the top of the mold is pressed in. The small hole in the top isn’t for filling with glue, it’s to let excess escape as the mold is closed. After things cool completely, just pop apart the mold (little cutouts for a screwdriver tip make this easy) and trim any excess. That’s all there is to it.

One last thing: among the downloads you may notice one additional model. That one is provided in split parts, so that one can make a mold of an arbitrary width just by stretching the middle parts as needed, then merging them together. After all, sometimes the STL file is just not quite right and if sharing CAD files is not an option for whatever reason, providing STLs that can be more easily tweaked is a welcome courtesy. You can watch a short video showing how the whole thing works, below.

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Acrylic Mold Makes For Professional-Looking Silicone Keyboards

February 3, 2020 by Dan Maloney 17 Comments

The border between consumer electronics and DIY projects is getting harder and harder to define. First it was PCBs, which quickly went from homemade to professional with quick-turn services. Then low-cost CAD/CAM packages and high-end fabrication services gave us access to enclosures that were more than black plastic boxes with aluminum covers. Where will it end?

That’s a question [arturo182] begins to answer with this custom-molded silicone keyboard for a handheld device. There’s no formal writeup, but the Twitter thread goes into some detail about the process he used to make the tiny qwerty keypad. The build started by milling a two-part mold from acrylic. Silicone rubber was tinted and degassed before injecting into the mold with a baster. The keys are connected by a thin membrane of silicone, and each has a small nub on the back for actuating a switch.

There’s clearly room for improvement in this proof of concept – tool marks from the milling process mar the finish of the keys slightly, for instance. There may be tips to be had from this article on silicone keyboard refurbishment to improve the process, but overall, we’d say [arturo182] is well on his way here.

3D Printing Paper — Sort Of

December 26, 2019 by Al Williams 31 Comments

There are only a few truly ancient engineered materials, and among the oldest is paper. Traditionally, paper is flat and can be bent into shapes. However, paper can be molded into for example packing material or egg cartons. [XYZAidan] has a process that can recycle paper into 3D cardboard-like objects. You need a 3D printer, but it doesn’t actually print the paper. Instead, you use the printer to create a mold that can form paper pulp you make out of recycled paper and a blender.

[Aidan] provides seven different molds ranging from a desk tray and a dish to simple cubes and coasters. The molds are made in three parts to assist in removing the finished product.

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Watch A Sand-Cast Slingshot Made, From Start To Finish

December 18, 2019 by Donald Papp 13 Comments

Sand-casting metal parts is a technique that has been around for a very long time, but it can be educational to see the process from start to finish. That’s exactly what [Frederico] shows us with his sand-cast slingshot of his own design, and it’s not bad for what he says is a first try!

First, [Frederico] makes a two-part green sand mold of the slingshot body. Green sand is a sand and clay mix, and is only green in the sense that it is wet or “raw” and not further processed. After the mold is made, it’s time to melt aluminum in the propane-powered furnace, and the molten aluminum is then poured into the mold.

After cooling, [Frederico] breaks up the sand to reveal the rough cast object. There is post-processing to do in the form of sprues to cut and some flashing around the seams to remove, but overall it looks to have turned out well. You can watch the whole process in the video, embedded below.

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