These Keycaps Are 100% Recycled Plastic

March 20, 2024 by Kristina Panos 4 Comments

Artisan keycaps are generally meant to replace your Escape key, though they can be used anywhere you like (as long as they fit, of course). Keycap maker [tellybelly] of jankycaps has been experimenting with making keycaps out of 100% recycled plastic, and offers an interesting post detailing their development and production process.

What do you do when normal injection molding tooling is out of your budget, and silicone molds simply won’t do? You turn to 3D printing if you can. In this case, [tellybelly] and company found a resin designed to withstand high temperatures.

[tellybelly] was able to design the mold using a plethora of online resources, and even verified the flow using a special program. Although the first two versions worked, they had some flaws. Third time’s the charm, though, and then it was time to sort plastic and fire up the shredder.

After heating up the shreds to 200 °C or so, it was time to start the injecting. This part isn’t exactly a cakewalk — mixing different plastics together can vary the workable temperature range that doesn’t degrade the plastic. Although it sounds like the end, [tellybelly] reports that they spent just as much time here as they did at the drawing board, experimenting with pressure on the mold, various cool-down methods, and how long to wait before opening the mold.

Via reddit

Recreating The Pop Ball

February 24, 2024 by Kristina Panos 14 Comments

Those who were kids in the 80s may remember a sweet little toy called the Pop Ball. A simple rubber hemisphere, this rubber cup could be turned inside out and thrown on the ground, where it would hit and bounce sky high whilst knocking itself right side out. The black ones worked particularly well, and were the first to be banned from [electrosync]’s school along with yo-yos, slap bracelets, and any number of toys that eventually became weaponized by enterprising children.

An industrial Vegemite injection-molded version that only kind of worked.

You can still find Pop Balls today, but they don’t work nearly as well as they did originally because of a lower Shore hardness in the rubber. Naturally, as an adult with futuristic toys at hand, [electrosync] just had to try re-creating the ’80s version. But it wasn’t easy.

They started by studying the patents and anything else they could find. They even managed to get a hold of Peter Fish, the original creator of the Pop Ball, to get some questions answered about the things. According to Peter, the black Pop Ball was made from recycled rubber and worked almost too well. Peter sent [electrosync] an old-stock Pop Ball, which they used to modify their CAD design.

It’s easy to root for [electrosync] throughout this journey, which consists of many failed prints and injection molding attempts. At last, they are able to at least recreate the snap of the modern Pop Ball once they finally found the right filament — the extremely elastic Recreus Filaflex 60A TPU. Of course, it wasn’t all lollipops and rainbows from there, because the filament is notoriously difficult to print with, but [electrosync] made it work. Check it out after the break.

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Lessons Learned: Plastic Injection Molding For Products

October 14, 2023 by Donald Papp 19 Comments

Injection molding is one of the technologies that makes the world go round. But what does it actually look like to go through the whole process to get a part made? [Achim Haug] wrote up a blog post that does a fantastic job of explaining what to expect when getting plastic enclosures injection molded in China.

These air quality monitors required a two-part enclosure.

Injection molding a part requires making a custom mold, which is then used by an injection molding machine in a shop to crank out parts. These are two separate jobs, but in China the typical business model is for a supplier to quote a price for both the mold as well as the part production. [Achim] describes not only what navigating that whole process was like, but also goes into detail on what important lessons were learned and shares important tips.

One of the biggest takeaways is to design the part with injection molding in mind right from the start. That means things like avoiding undercuts and changes in part thickness, as well as thinking about where the inevitable mold line will end up.

[Achim] found that hiring a been-there-done-that mold expert as a consultant to review things was a huge help, and well worth the money. As with any serious engineering undertaking, apparently small features or changes can have an outsized impact on costs, and an expert can recognize and navigate those.

In the end, [Achim] says that getting their air quality monitor enclosures injection molded was a great experience and they are very happy with the results, so long as one is willing to put the work in up front. Once the mold has been made, downstream changes can be very costly to make.

[Achim]’s beginning-to-end overview is bound to be useful to anyone looking to actually navigate the process, and we have a few other resources to point you to if you’re curious to learn more. There are basic design concerns to keep in mind when designing parts to make moving to injection molding easier. Some injection molding techniques have even proven useful for 3D printing, such as using crush ribs to accommodate inserted hardware like bearings. Finally, shadow lines can help give an enclosure a consistent look, while helping to conceal mold lines.

Making An Injection Mold For Yourself

August 28, 2023 by Jenny List 29 Comments

Injection molding is the obvious onward step from 3D printing when the making of a few plastic parts becomes their series manufacture. The problem with injection molding is though, that making a mold can be prohibitively expensive. Has the advent of affordable CNC machining changed that? [Teaching Tech] takes a look, and machines a mold for part of a bicycle bracket.

With a diversion into home-made silicone seals for the injection molding machine, he proceeds to machine the mold itself from a block of aluminium. It’s a basic introduction to mold construction for those of us who’ve never ventured in this direction before, and it provides some interesting lessons. As we’d expect he does a rough machining pass before returning with a ball-end tool to smooth off those curves, but there’s a lesson in measuring rather than believing the paperwork. The tool he used was a bit smaller then the spec, so his path left some rough edges that had to be returned to. Otherwise the use of a removable pair of bolts to form holes in the finished part is we guess obvious after watching the video, but it’s something we learned as injection molding newbies.

This video follows on from a previous one we also covered, in which we’re introduced to the machine itself.

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Enhance Your Enclosures With A Shadow Line

August 7, 2023 by Donald Papp 15 Comments

Some design techniques and concepts from the injection molding world apply very nicely to 3D printing, despite them being fundamentally different processes. [Teaching Tech] demonstrates designing shadow lines into 3D printed parts whose surfaces are intended to mate up to one another.

This is a feature mainly seen in enclosures, and you’ve definitely seen it in all kinds of off-the-shelf products. Essentially, one half of the part has a slight “underbite” of a rim, and the other half has a slight “overbite”, with a bit of a standoff between the two. When placed together, the combination helps parts self-locate to one another, as well as providing a consistent appearance around the mating surfaces.

Why is this necessary? When a plastic part is made — such as an enclosure in two halves — the resulting surfaces are never truly flat. Without post-processing, the two not-quite-flat surfaces result in an inconsistent line with a varying gap between them.

By designing in a shadow line, the two parts will not only self-locate to each other for assembly, but will appear as a much more consistent fit. There will be a clear line between the two parts, but no actual visible gaps between them. Watch the whole thing explained in the video, embedded below.

This isn’t the only time design techniques from the world of injection molding have migrated to 3D printing. Crush ribs have been adapted to the world of 3D printed parts and are a tried-and-true solution to the problem of reliably obtaining a tight fit between plastic parts and hardware inserts.

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Repairing A Home Injection Molding Machine

August 5, 2023 by Maya Posch 10 Comments

When [Michael] over at the Teaching Tech YouTube channel bought a hobby injection molding machine a long time ago, one of the plans he had with it was to use it for grinding up waste bits of PLA filament for injection molding. Since the machine was bought from a US shop and [Michael] is based in Australia it required some modifications to adapt it to the local 220+ VAC mains, followed by adding a PID temperature controller and a small compressor to provide the compressed air rather than from a large shop compressor.

Although [Michael] had discussed using the machine for PLA with the seller to confirm that this would work, a user error meant that the now defective unit had been sitting idly for many years, until recently.

Since the machine had been gathering dust and rust in the garage, fixing the machine up took a complete teardown to remove corrosion and resolve other issues. After this the original fault was identified, which turned out to be a shorted wire near the heater which had been turned up to a too high temperature, leading to the release of magic smoke and banishment of the machine to the Pit of Despair, AKA the shadowy depths of one’s garage.

In this first installment, [Michael] cleaned up the machine and restored it to a working state. In the next part injection molding will be attempted again, which should give some idea of the feasibility of turning scraps of PLA and failed 3D prints into smooth injection molded parts, assuming you have the CNC machine or patience to carve out the requisite molds, of course.

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Hackaday Prize 2022: Recycled Plastic Skateboard Decks Demonstrate Small-Scale Injection Molding

October 21, 2022 by Danie Conradie 25 Comments

Injection molding is usually focused on high-volume production, but that doesn’t always need to be the case. The Recycled Plastic Skateboard Deck project centers on the use of injection molding for a relatively low-volume production line using open-source tooling.

RPSD is part of the Precious Plastics ecosystem and uses the existing and open-source shredder and extruder to turn locally-sourced plastic waste into melted plastic. The core of the tooling is in the aluminum CNC-machined top, bottom, and edge mold sections bolted to a thick steel support structure that give the skateboard deck its shape. The edge section defines the deck’s perimeter, and 64 cartridge heaters are inserted into it to bring the mold up to temperature. The mold is mounted on a scissor lift mechanism to allow it to be aligned with the extruder, and temperature control electronics are housed in a laser-cut metal enclosure, which is bolted to the base of the mold structure.

To be clear, this is not a cheap way to make a couple of skateboard decks, but rather a way for small shops to do injection molded decks in-house. At ~$7500 for the components of this relatively large mold, excluding the extruder, you’d still have to sell quite a few decks to make it economically viable.

Although small-scale injection molding has become a lot more accessible, the cost of machined metal molds will remain high for the foreseeable future. However, if you only need small, flexible parts, you could probably do it for under $50 using 3D printed molds and silicone.

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