injection molding

49 Articles

Milling Dies And Injection Moulding Some Acrylic Lenses

July 7, 2020 by 18 Comments

[Zach] over at his channel Breaking Taps has put up an extraordinary account on manufacturing some homemade acrylic lenses. In the end, not only does he produce some beautiful concave lenses, he also covers the complete manufacturing process, from milling the aluminium die used for injection moulding to tweaking the parameters associated with injecting the actual acrylic, he even goes over the limitations of optics produced in this fashion.

What caught our eye in particular, was how [Zach] used the finished product to practically demonstrate photoelasticity originating from the stress induced by the moulding process. You might be familiar with describing the optical properties of a material by a single number, i.e its permittivity. But what happens if in addition to altering speed, the material also alters the polarisation and direction of light depending on the stress distribution within the material? Whilst a quantitative answer gets a bit complicated you can check out [Zach’s] additional videos to visualise the answer in a pretty and colourful way, without resorting to fancy computer simulations! If however, you really want to persist with the simulation route, check out our article on stress analysis in a totally different setting using Finite Element Analysis.

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Gain An Understanding Of Injection Molding’s Design Gotchas

April 19, 2020 by 11 Comments

When it comes to manufacturing, sheet metal and injection molding make the world go ’round. As a manufacturing method, injection molding has its own range of unique design issues and gotchas that are better to be aware of than not. To help with this awareness, [studiored] has a series of blog posts describing injection molding design issues, presented from the perspective of how to avoid and address them.

Design of screw bosses demonstrating conflict between molder’s guidelines and vendor’s recommendations. Compromising between both is a science and an art.

Because injection molding involves heat, warp is one issue to be aware of and its principles will probably be familiar to anyone with nitty-gritty experience in 3D printing. Sink marks are also an issue that comes down to differential cooling causing problems, and can ruin a smooth and glossy finish. Both of these play a role in how best to design bosses.

Minimizing and simplifying undercuts (similar to overhangs in 3D printer parlance) is a bit more in-depth, because even a single undercut means much more complex tooling for the mold. Finally, because injection molding depends on reliably molding, cooling, and ejecting parts, designing parts with draft (a slight angle to aid part removal) can be a fact of life.

[studiored] seems to have been working overtime on sharing tips for product design and manufacture on their blog, so it’s worth keeping an eye on it for more additions. We mentioned earlier that much of the manufacturing world revolves around injection molding and sheet metal, so to round out your knowledge we published a primer on everything you need to know about the art and science of bending sheet metal. With a working knowledge of the kinds of design issues that affect these two common manufacturing methods, you’ll have a solid foundation for any forays into either world.

Injection Molding With A Hot Glue Gun

June 11, 2019 by 11 Comments

Injection molding is an industrial process used the world over for the quick and economical production of plastic parts. [Nikodem Bartnik] wanted to experiment with this at home, so whipped up some molds and got to work (Youtube link, embedded below).

[Nikodem] produced aluminium molds, using a Dremel-based CNC platform. This allowed for the design to be created in CAD software, and helps with the production of the geometry for both the part, as well as the gates and vents. Having learned about thermal issues with an early attempt, the mold was then clamped in a vice. Wood was used as an insulator to minimise heat lost to the vice.

With this setup, it was possible to mold M5 washers using hot glue, with good surface finish. Later attempts with a larger mold were unsuccessful, due to the glue cooling off before making it through the entire mold. [Nikodem] has resolved to improve his setup, and we look forward to seeing what happens next. We’ve seen others experiment in this area before, too. Video after the break.

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Innovative Bird Feeder Design Recycles Recycling’s Garbage

May 2, 2019 by 17 Comments

Recycling beverage cartons isn’t 100% efficient. The process yields some unusable garbage as a byproduct. Why? Because containers like juice boxes are mostly paper, but also contain plastic and aluminum. The recycling process recovers the paper fibers for re-use, but what’s left after that is a mixture of plastic rejects and other bits that aren’t good for anything other than an incinerator or a landfill. Until now, anyway!

It turns out it is in fact possible to turn such reject material into a product that can be injection-molded, as shown here with [Stefan Lugtigheid]’s SAM bird feeder design. The feeder is not just made from 100% recycled materials, it’s made from the garbage of the recycling process — material that would otherwise be considered worthless. Even better, the feeder design has only the one piece. The two halves are identical, which reduces part count and simplifies assembly.

[Stefan] makes it clear that the process isn’t without its quirks. Just because it can be injection-molded doesn’t mean it works or acts the same as regular plastic. Nevertheless, the SAM birdfeeder demonstrates that it can definitely be put to practical use. We’ve seen creative reprocessing of PET bottles and sheet stock made from 3D printed trash, but recycling the garbage that comes from recycling drink cartons is some next-level stuff, for sure.

The Greatest Computer Ever Now Gets A New, Injection Molded Clear Case

January 21, 2019 by 55 Comments

The Macintosh SE/30 is the greatest computer ever made. It was a powerhouse when it was launched almost exactly thirty years ago today. You could stuff 128 Megabytes of RAM into it, an absolutely ludicrous amount of RAM for 1989. You could put Ethernet in it. You could turn the 1-bit black or white internal display into an 8-bit grayscale display. I think there was a Lisp card for it. These were just the contemporaneous hacks for the SE/30. Now, people are actively developing for this machine and putting Spotify on it. There’s a toolbar extension for Macs of this era that will let you connect to a WiFi network. You’ll be hard pressed to find a computer that still has a fanbase this big thirty years after release.

Now, there’s a project to create new injection molded cases for the Mac SE/30 (and the plain ‘ol SE). These cases will be clear, just like Apple prototypes of the era. It’s also one of the most difficult injection molding projects retrocomputer enthusiasts have ever taken up.

Over the years, we’ve seen some interesting projects in the way of creating new plastic cases for old computers. The most famous is perhaps the remanufacturing of Commodore 64C cases. Instead of a purely community-driven project, this was an accident of history. The story goes that one guy, [Dallas Moore], went to an auction at an injection molding factory. The owner mentioned something about an old computer, and wheels started turning in someone’s head. A Kickstarter later, and everyone who wanted a new C64 case got one. You could get one in translucent plastic to go with the retro aesthetic.

New cases for the Amiga A1200 have also been made thanks to one fan’s Solidworks skills and a Kickstarter campaign. There is, apparently, a market for remanufactured cases for retrocomputers, and it’s just barely large enough to support making new injection molding tooling.

So, about that SE/30. The folks on the 68k Macintosh Liberation Army forums are discussing the possibility of making a new case for the greatest computer Apple will ever make. The hero of this story is [maceffects] who has already modeled the back ‘bucket’ of the SE/30 and printed one out on a filament printer (check out the videos below). This was then printed in clear SLA, and the next step is crowdfunding.

While this isn’t a complete case — a front bezel would be needed to complete the case — it is an amazing example of what the retrocomputing community can do. The total cost to bring this project to fruition would be about $15,000 USD, which is well within what a crowdfunding campaign could take in. Secondary runs could include a translucent Bondi Blue polycarbonate enclosure, but that’s pure speculation from someone who knows what would be the coolest project ever.

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ABS: Three Plastics In One

December 11, 2018 by 31 Comments

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.

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An Old Way To Make A New Crank Handle

March 3, 2018 by 24 Comments

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.

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