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.

Omnibot Shows Off Over A Decade Of CNC Prowess

April 23, 2022 by Ryan Flowers 17 Comments

At first glance, you might think the Omnibot v3 wasn’t anything more than a basic 3D printed robotics platform, but you’d be wrong on both counts. There’s actually no 3D printed parts on the build, and while you could describe the platform as simplistic, calling it basic certainly doesn’t do the clever design justice. In the video after the break, creator [Michal] takes us through the process of designing and building this high quality bot.

The build starts with huge amounts of time and effort in a CAD program designing the Omnibot v3 with its four wheel steering and ability to do fancy things like spin in place. With the CAD and 3D renders out of the way, the process of transforming the digital into the physical began with a CNC router.

Rather than routing the individual components out of a suitable material, [Michal] cut forms. Those forms were made only for the creation of silicone molds. Those silicon molds where then used to pour the actual parts with polyurethane resin. It is these resin parts that make up the actual Omnibot v3, which is manually demonstrated at the end of the video.

All in all, it’s a neat project with a neat process. If we were to stop here, things would be mostly complete and you’d click on to the next great Hackaday article. But there’s more to be had here. You see, [Michal] is also fellow behind the Guerrilla guide to CNC and resin casting. In his own words: “CNC machining and resin casting are an underappreciated method for producing engineering-grade parts, but the process is fast, predictable, and garage-friendly.” After seeing the results, we can’t help but to agree.

By the way, before anybody in the comments can yell “DUPE!”, we already know. You see, we featured the Guerrilla guide to CNC and resin casting once before, almost exactly 11.5 years ago! It’s been updated since then, and appears to be an absolute gold mine of information for anybody wanting to walk in [Michal]’s shoes.

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Modular Box Design Eases Silicone Mold-Making

June 16, 2021 by Donald Papp 13 Comments

Resin casting is a fantastic way to produce highly detailed parts in a wide variety of colors and properties, and while the process isn’t complicated, it does require a certain amount of care and setup. Most molds are made by putting a part into a custom-made disposable box and pouring silicone over it, but [Foaly] was finding the process of making and re-making those boxes a bit less optimized than it could be. That led to this design for a re-usable, modular, adjustable mold box that makes the workflow for small parts considerably more efficient.

The walls of the adjustable box are four identical 3D-printed parts with captive magnets, and the base of the box is a piece of laser-cut steel sheet upon which the magnetic walls attach. The positioning and polarity of the magnets are such that the box can be assembled in a variety of sizes, and multiple walls can be stacked to make a taller mold. To aid cleanup and help prevent contamination that might interfere with curing, the inner surfaces of each piece are coated in Kapton tape.

The result is a modular box that can be used and re-used, and doesn’t slow down the process of creating and iterating on mold designs. The system as designed is intended for small parts, but [Foaly] feels there is (probably) no reason it can’t be scaled up to some degree. Interested? The design files are available from the project’s GitHub repository, and if you need to brush up a bit on how resin casting works, you can read all about it here.

Mold-Making Masterclass In Minutes

August 5, 2020 by Kristina Panos 11 Comments

Making silicone molds seems easy, but there are a lot of missteps to be made along the way that can mean the difference between a great, reusable mold, and one that’s a sad waste of silicone. If you’re helpless to know the difference, then check out [Eric Strebel]’s 9-minute masterclass teaser video on making a two-part mold for resin casting, which is also embedded below.

Even if you already know how to do this, there’s probably a good tip in here somewhere. One of them being that you should always pour your silicone from one place and let it coat the piece being copied. Otherwise, there might be lines on the mold. Another tip is for DIY mold release made from petroleum jelly thinned with naphtha.

Our favorite tip has to do with the way [Eric] makes this a reusable two-part mold, which is more akin to injection molding. To pour silicone for the second part and get it to separately nicely, [Eric] uses sprues made out of resin rods that were cast inside of drinking straw molds. These he chamfers against a belt sander to minimize the contact with the cast part, which makes them a snap to break off. [Eric] says this is just the beginning, and there are more videos to come that will break down the steps.

There’s more than one way to make a mold, especially for casting in metal. We’ve seen everything from 3D-printed molds to kinetic sand.

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Hackaday Podcast 070: Memory Bump, Strontium Rain, Sentient Solder Smoke, And Botting Browsers

June 5, 2020 by Mike Szczys No comments

Hackaday editors Elliot Williams and Mike Szczys bubble sort a sample set of amazing hacks from the past week. Who has even used the smart chip from an old credit card as a functional component in their own circuit? This guy. There’s something scientifically devious about the way solder smoke heat-seeks to your nostrils. There’s more than one way to strip 16-bit audio down to five. And those nuclear tests from the 40s, 50s, and 60s? Those are still affecting how science takes measurements of all sorts of things in the world.

Take a look at the links below if you want to follow along, and as always, tell us what you think about this episode in the comments!

Direct download (60 MB or so.)

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Pumping Concrete

March 29, 2020 by Mike Szczys 39 Comments

Due to social distancing, gym rats throughout the world are turning everyday objects into exercise equipment to keep up the routine without actually hitting the gym. A particularly pleasing version of this are these concrete dumbbells whipped up by the unfortunately named hacker [ShitnamiTidalWave].

If you happen to have half a bag of concrete — quick set or otherwise — out in the shed you can follow the lead on this one. But even if you’re not the kind of person who has “arm day” on your calendar (most of us here in the Hackaday bunker do not) this hack is still worth your time. Mold making is one of the uber-useful skills you should have in your hacker toolkit and [ShitnamiTidalWave] has done both an excellent job of building a mold, and of explaining the process.

Raw material for this one couldn’t be easier; each mold is made out of plywood, 2×4 stud, and nails, along with handles made of 3/4″ PVC pipe. The studs were ripped down and used to create the 45 degree chamfers at each edge. Mold-making veterans will tell you that release agent is a must and in this case rubbing the insides of the molds with wax made it a snap to pry the wooden forms off of the set concrete.

Concrete has a tendency to crack as it cures so if you’re casting large pieces like this touch-sensitive concrete countertop you might want to throw in some fiber reinforcement to the mix. If you’re keen on seeing some of the more impressive mold-making skills at work, check out how metal parts are cast from 3D-printed molds and how a master duplicates parts using silicone molds.

[via r/DIY]

Giant LEDs, Ruby Lasers, Hologram Displays, And Other Cool Stuff Seen At Maker Faire Rome

October 25, 2019 by Mike Szczys 16 Comments

Hackers from all over Europe descended upon Rome last weekend for the Maker Faire that calls itself the “European Edition”. This three-day event is one of the largest Maker Faires in the world — they had 27,000 school students from all over Italy and Europe attend on Friday alone.

This was held at Fiera Roma, a gigantic conference complex two train stops south of the Rome airport — kind of in the middle of nowhere. I was told anecdotally that this is the largest event the complex hosts but have no data to back up that claim. One thing’s for certain, three days just wasn’t enough for me to enjoy everything at the show. There was a huge concentration of really talented hardware hackers on hand, many who you’ll recognize as creators of awesome projects regularly seen around Hackaday.

Here’s a whirlwind tour of some of my favorites. On that list are a POV holographic display, giant cast-resin LEDs, an optical-pump ruby laser built out of parts from AliExpress, blinky goodness in cube-form, and the Italian audience’s appreciation for science lectures (in this case space-related). Let’s take a look.

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