It would be really hard to go through a typical day in the developed world without running across something made from ABS plastic. It’s literally all over the place, from toothbrush handles to refrigerator interiors to car dashboards to computer keyboards. Many houses are plumbed with pipes extruded from ABS, and it lives in rolls next to millions of 3D-printers, loved and hated by those who use and misuse it. And in the form of LEGO bricks, it lurks on carpets in the dark rooms of children around the world, ready to puncture the bare feet of their parents.
ABS is so ubiquitous that it makes sense to take a look at this material in terms of its chemistry and its properties. As we’ll see, ABS isn’t just a single plastic, but a mixture that takes the best properties of its components to create one of the most versatile plastics in the world.
When the crank handle on [Eric Strebel]’s cheapo drill press broke in two, did he design and print a replacement? Nah. He kicked it old school and cast a new one in urethane resin.
In his newest video, [Eric] shows us his approach to molding and casting a handle that’s likely stronger than the original. The old crank handle attached to the shaft with a brass collar and a grub screw, so he planned around their reuse. After gluing the two pieces together and smoothing the joint with body filler, he packs the back of the handle with clay. This is a great idea. The original handle just has hollow ribbing, which is probably why it broke in the first place. It also simplifies the cast a great deal.
Here’s where things get really interesting. [Eric] planned to make a one-piece mold instead of two halves. At this point it becomes injection molding, so before he gets out the reusable molding box, he adds an injection sprue as an entry point for the resin, and a plug to support the sprue and the handle. Finally, [Eric] mixes up some nice bright Chevy orange resin and casts the new handle. A few hours later, he was back to drilling.
Crank past the break to watch [Eric]’s process, because it’s pretty fun to watch the resin rise in the clear silicone mold. If you want to take a deeper dive into injection molding, we can fill that need.
We imagine you’ve heard this already, but waste plastic is a problem for the environment. We wrap nearly everything we buy, eat, or drink in plastic packaging, and yet very little of it ends up getting recycled. Worse, it doesn’t take a huge industrial process to melt down a lot of this plastic and reuse it, you can do it at home if you were so inclined. So why aren’t there more localized projects to turn all this plastic trash into usable items?
That the question that [Precious Plastic] asks, and by providing a centralized resource for individuals and communities looking to get into the plastic recycling game, they hope to put a dent in the worldwide plastic crisis. One of their latest projects is showing how plastic trash can be turned into functional iPhone cases with small-scale injection molding.
The video after the break goes into intricate detail about the process involved in creating the 3D CAD files necessary to make the injection molds. Even if you don’t plan on recycling milk jugs at home, the information and tips covered in the video are extremely helpful if you’ve ever contemplated having something injection molded. The video even demonstrates a neat feature in SolidWorks that lets you simulate how molten plastic will move through your mold to help check for problem areas.
Once you’ve designed your mold on the computer, you need to turn it into a physical object. If you’ve got a CNC capable of milling aluminum then you’re all set, but if not, you’ll need to outsource it. [Precious Plastic] found somebody to mill the molds through 3DHubs, though they mention in the video that asking around at local machine shops isn’t a bad idea either.
With the mold completed, all that’s left is to bolt the two sides together and inject the liquid plastic. Here [Precious Plastic] shows off a rather interesting approach where they attach the mold to a contraption that allows them to inject plastic with human power. Probably not something you’d want to do if you’re trying to make thousands of these cases, but it does show that you don’t necessarily need a high tech production facility to make good-looking injection molded parts.
Every so often, a project is worth some extra work to see if the idea can go any further. [JohnSL] has been busy doing exactly that with his spring-loaded SMT tape holder project. Having done the original with 3D printing, he has been working on designing for injection molding. This isn’t a motorized feeder, it’s still a manual tool but it is an improvement over the usual workshop expedient method of just sticking segments of tape down to the desktop. Tape is fed into the holders from one end and spring tension holds the tape firm while a small slot allows the cover tape to be guided backward after peeling. As anyone who has used cut segments of tape to manually deal with SMT parts knows, small vibrations — like those that come from peeling off the clear cover — can cause the smaller components to jump around and out of their pockets, and any length of peeled cover gets awkward quickly.
In [JohnSL]’s design, all SMT tapes sit at an even height regardless of size or tape thickness. A central support pushes up from the bottom with tension coming from a spring pulling sideways; the central support is forced upward by cams and presses against the bottom surface of the tape. As a result, the SMT tape gets supported from below with even tension and the whole assembly maintains a narrow profile suitable for stacking multiple holders side by side. The CAD files are available online along with a McMaster-Carr part number for the specific spring he used.
After working out the kinks on 3D printed prototypes, [JohnSL] decided to see if it would be feasible to design an injection molded version and made a video outlining the process, embedded below.
3D printing is great for prototyping, and not bad for limited runs of parts. Unfortunately though it really doesn’t scale well beyond a few pieces, so when you’re ready for the mass market you will need to think about injection molding your parts. But something like that has to be farmed out, right? Maybe not, if you know a thing or two about designing your own injection molds.
The video below comes from [Dave Hakkens] by way of his Precious Plastic project, whose mission it is to put the means of plastic recycling into the hands of individuals, rather than relying on municipal programs. We’ve covered their work before, and it looks like they’ve come quite a way to realizing that dream. This tutorial by [Dave]’s colleague [Jerry] covers the basic elements of injection mold design, starting with 3D modeling in Solidworks. [Jerry] points out the limitations of a DIY injection molding effort, including how the thickness of parts relates to injection pressure. Also important are features like gentle curves to reduce machining effort, leaving proper draft angles on sprues, and designing the part to ease release from the mold. [Jerry] and [Dave] farmed out the machining of this mold, but there’s no reason a fairly complex mold couldn’t be produced by the home gamer.
3D printing is a technique we’ve all been using for ages at home, or via Shapeways, but if you are designing a product, 3D printing will only get you so far. It’s crude, slow, expensive, and has lots of limitations. While it’s great for the prototyping stage, ultimately products manufactured in volume will be manufactured using another method, and most likely it will be injection molding. Knowing how to design a part for injection molding means you can start prototyping with 3D printing, confident that you’ll be able to move to a mold without major changes to the design.
The 2017 Hackaday Prize includes a $30,000 prize for Best Product as we seek products that not only show a great idea, but are designed for manufacturing and have thought through what it takes to get them into the hands of the users. Some of the entries seem to be keenly aware of the challenges associated with moving from prototyping to production. Here are some examples of best practices when prototyping with future injection molding in mind.
The most popular crowdfunding campaign of the month is Lego tape. It’s an adhesive-backed tape with studs on the top, allowing you to clip Lego pieces into place. How easy would this be to create at home? It’s really just a silicon mold and some 3M stickytape. Anyone up for a home casting challenge?
You guys know the Hackaday Overlords have a Design Lab, right? What’s a Design Lab? It’s a place filled with tools where we allow residents to come in for free, build stuff, give them training, and let them keep all their IP. It’s like a hardware accelerator, but focused on Open Source hardware. It is our gift to the community and we ask nothing in return. But that’s not important right now. We’re doing shots.
2017 will be the first year Maker Faire will have three flagship faires. New York is a given, as is the Bay Area. and A few weeks ago, Chicago grabbed the third flagship faire. If you’ve already bought tickets and scheduled your trip, terrible news: the Chicago Maker Faire has been postponed until late fall.
Flip clocks are cool. What’s a flip clock? The clock in Groundhog Day, or a bunch of flaps, gears, and a synchronous motor that displays the time. You know what’s not cool about flip clocks? They’re usually stuffed in horrible 70s plastic enclosures painted Harvest Gold or Avacado. [bentanme] found a flip clock and stuffed it in a glass jar. It’s kept in place by a few 3D printed parts that ingeniously keep the clock from moving around while still allowing you to see the gears. Neat.
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