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 53 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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Solar-Harvesting Blinkenlights

September 3, 2019 by Bryan Cockfield 15 Comments

A few years ago a fad ripped through the makersphere where people would build cheap, solar powered LED blinkers, glue a magnet to them, and throw them on anything metal. It was an interesting time, but luckily did not last for too long. With some effort and craftsmanship, though, the solar throwie idea can be turned into something more elegant, though, such as this solar harvesting blinking gadget.

Like its predecessors, the device itself behaves simply, although this one is equipped with a small supercapacitor which can run the device for 8 hours without sun. It has a small solar panel which can charge the capacitor in five minutes, and from there the LEDs inside simply blink. The quality shows in the final packaging, as [Jasper] has taken to encasing them in epoxy shapes such as pyramids, for a nice paperweight or tchotchke. It is also noteworthy because of Jasper’s test device; since he is mass producing them he needed something to test each board for functionality before encasing them in the epoxy, and he built a small pen tester specifically for them too.

While the build is pretty straightforward, anyone looking to enclose a simple circuit in epoxy without bubbles or other problems might want to check this one out. It would also be a good platform for building other throwie-like projects on top of. In the past they didn’t just blink lights but also did things like run small Linux servers.

3D Printed Wheels Get Some Much Needed Grip

January 30, 2019 by Tom Nardi 11 Comments

You’d be hard-pressed to find more ardent supporters of 3D printing then we here at Hackaday; the sound of NEMA 17 steppers pushing an i3 through its motions sounds like a choir of angels to our ears. But we have to admit that the hard plastic components produced by desktop 3D printers aren’t ideal for a number of applications. For example, the slick plastic is useless for all but the most rudimentary of wheels. Sure there are flexible filaments that can give a printed wheel a bit of grip, but they came with their own set of problems (not to mention, cost).

In the video after the break, [Design/Forge] demonstrates a clever method for fitting polyurethane rubber “tires” onto 3D printed hubs which is sure to be of interest to anyone who’s in the market for high quality bespoke wheels for their project. The final result looks extremely professional, and while there’s a considerable amount of preparation that goes into it, once you’re set up you should be able to pump these out quickly and cheaply.

The process begins with a 3D printed mold pattern, which includes the final tire tread texture. This means you can create tire treads of any design you wish, which should have some creative as well as practical applications. The printed part is then submerged in silicone rubber and allowed to cure for 8 hours. Once solidified, the silicone rubber becomes the mold used for the next steps, and the original printed part is no longer needed.

The second half of the process is 3D printing the wheels to which the tires will be attached. These will be much smaller than the original 3D printed component, and fit inside of the silicone mold. The outside diameter of the printed wheel is slightly smaller than the inside diameter of the mold, which gives [Design/Forge] the space to pour in the pigmented polyurethane rubber. The attentive viewer will note that the 3D printed wheel has a slight ribbed texture designed into it, so that there will be more surface area for the polyurethane to adhere to. Once removed from the mold and cleaned up a bit, the final product really does look fantastic; and reminds us of a giant scale LEGO wheel.

Whether you’re casting metal parts or just want a pair of truly custom earbuds, creating silicone molds from 3D printed parts is an extremely useful skill to familiarize yourself with. Though even if you don’t have a 3D printer, there’s something to be said for knowing how to mold and cast real-world objects as well.

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