Multi-Material Printing Enables Low Cost Silicone Prototypes

September 4, 2024 by Tom Nardi 9 Comments

While it’s the ideal choice for mass production, injection molding is simply no good for prototyping. The molds are expensive and time-consuming make, so unless you’ve got the funding to burn tens of thousands of dollars on producing new ones each time you make a tweak to your design, they’re the kind of thing you don’t want to have made until you’re absolutely sure everything is dialed in and ready. So how do you get to that point without breaking the bank?

That’s not always an easy question, but if you’re working with silicone parts, the team at OpenAeros thinks they might have a solution for you. As demonstrated through their OpenRespirator project, the team has developed a method of 3D printing single-use molds suitable for large silicone parts that they’re calling Digital-to-Silicone (D2S).

In the video below, [Aaron] and [Jon] explain that they started off by simply printing injection molds in the traditional style. This worked, but the molds can get quite complex, and the time and effort necessary to design and print them wasn’t a great fit for their iterative development cycle. They wanted to be able to do from design to prototype in a day, not a week.

Eventually they realized that if they printed the mold out of a water-soluble filament, they could simplify its design greatly. They’ve documented the design process in detail, but the short version is that you essentially subtract the 3D model of the design you want to produce from a solid shape in your CAD package, and add a few holes for injecting the silicone. Once the silicone has cured, the mold can be dissolved away in warm water to reveal the finished part.

They then took this concept a step further. Thanks to the multi-material capabilities offered by some of the latest 3D printers, it’s possible to print structures within the mold. Once the silicone is injected, these structures can become part of the finished part. For the OpenRespirator, this lets them add PETG stiffening rings around where the filters to snap into the silicone mask body.

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Print Wave Metal Casting

July 13, 2024 by Navarre Bartz 4 Comments

Direct 3D printing of metal remains out of reach for the hobbyist at the moment, so casting is often the next best thing, particularly given the limitations of 3D printed metals. [Denny] from Shake the Future shows us how to simplify the process with “print wave metal casting.”

The first step of printing a PLA object will seem familiar to any 3D print to metal process, but the main differentiator here is pouring the investment casting on the printer build plate itself. We like how he used some G-code to shake the build plate to help remove bubbles. Once the plaster solidifies, the plastic and mold are placed in the microwave to soften the plastic for removal.

The plaster is dried in an oven (or air fryer) and then [Denny] bolts the mold together for the casting process. Adding a vacuum helps with the surface finish, but you can always polish the metal with a generous helping of elbow grease.

If [Denny] seems familiar, you might remember his very detailed breakdown of microwave casting. We’ve seen plenty of different approaches to metal casting over the years here. Need a part in another material? How about casting concrete or resin?

Thanks to [marble] on the Hackaday Discord for the tip!

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How To Cast Silicone Bike Bits

April 26, 2024 by Jenny List 23 Comments

It’s a sad fact of owning older machinery, that no matter how much care is lavished upon your pride and joy, the inexorable march of time takes its toll upon some of the parts. [Jason Scatena] knows this only too well, he’s got a 1976 Honda CJ360 twin, and the rubber bushes that secure its side panels are perished. New ones are hard to come by at a sensible price, so he set about casting his own in silicone.

Naturally this story is of particular interest to owners of old motorcycles, but the techniques should be worth a read to anyone, as we see how he refined his 3D printed mold design and then how he used mica powder to give the clear silicone its black colour. The final buses certainly look the part especially when fitted to the bike frame, and we hope they’ll keep those Honda side panels in place for decades to come. Where this is being written there’s a CB400F in storage, for which we’ll have to remember this project when it’s time to reactivate it.

If fettling old bikes is your thing then we hope you’re in good company here, however we’re unsure that many of you will have restored the parts bin for an entire marque.

A red hot crucible is held with metal tongs above a white plaster mold. The mold is held in a bright pink silicone sleve atop a metal pan on a wooden workbench. Red cheese wax holds the sleeve to a metal funnel connected to a vacuum cleaner.

Lost Print Vacuum Casting In A Microwave

March 2, 2024 by Navarre Bartz 16 Comments

Hacks are rough around the edges by their nature, so we love it when we get updates from makers about how they’ve improved their process. [Denny] from Shake the Future has just provided an update on his microwave casting process.

Sticking metal in a microwave certainly seems like it would be a bad idea at first, but with the right equipment it can work quite nicely to develop a compact foundry. [Denny] walks us through the process start to finish in this video, including how to build the kilns, what materials to use, and how he made several different investment castings using the process. The video might be worth watching just for all the 3D printed tools he’s built to aid in the process — it’s a great example of useful 3D prints to accompany your fleet of little plastic boats.

A lot of the magic happens with a one minute on and six minutes off cycle set by a simple plug timer. This allows a more gradual ramp to burn out the PLA or resin than running the microwave at full blast which can cause some issues with the kiln, although nothing catastrophic as demonstrated. Vacuum is applied to the mold with a silicone sleeve cut from a swimming cap while pouring the molten metal into the mold to draw the metal into the cavities and reduce imperfections.

We appreciate the shout out to respirators while casting or cutting the ceramic fiber mat. Given boric acid’s effects, [PDF] you might want to use safety equipment when handling it as well or just use water as that seems like a valid option.

If you want to see where he started check out this earlier version of the microwave kiln and how he used it to make an aluminum pencil.

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Slime Mold-Powered Smart Watches See Humans Fall In Love With The Goo

February 16, 2024 by Lewin Day 13 Comments

Humans are very good at anthropomorphising things. That is, giving them human characteristics, like ourselves. We do it with animals—see just about any cartoon—and we even do it with our own planet—see Mother Nature. But we often extend that courtesy even further, giving names to our cars and putting faces on our computers as well.

A recent study has borne this out in amusing fashion. Researchers at the University of Chicago found that human attitudes towards a device can change if they are required to take actions to look after it. Enter the slime mold smartwatch, and a gooey, heartwarming story of love and care between human and machine, mediated by mold.

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Make Better 3D Printed Molds, For Thermoforming Plastics

September 2, 2023 by Donald Papp 6 Comments

Thermoforming — which includes vacuum-forming — has its place in a well-rounded workshop, and Mayku (makers of desktop thermoforming machines) have a short list of tips for getting the best results when 3D printing molds on filament-based printers.

A mold is put into direct, prolonged contact with a hot sheet of semi-molten plastic. If one needs a mold to work more than once, there are a few considerations to take into account. The good news is that a few simple guidelines will help get excellent results. Here are the biggest ones:

The smoother the vertical surfaces, the better. Since thermoforming sucks (or pushes) plastic onto and into a mold like a second skin, keeping layer heights between 0.1 mm and 0.2 mm will make de-molding considerably easier.
Generous draft angles. Aim for a 5 degree draft angle. Draft angles of 1-2 degrees are common in injection molding, but a more aggressive one is appropriate due to layer lines giving FDM prints an inherently non-smooth surface.
Thick perimeters and top layers for added strength. The outside of a mold is in contact with the most heat for the longest time. Mayku suggests walls and top layer between 3 mm to 5 mm thick. Don’t forget vent holes!
Use a high infill to better resist stress. Molds need to stand up to mechanical stress as well as heat. Aim for a 50% or higher infill to make a robust part that helps resist deformation.
Ensure your printer can do the job. 3D printing big pieces with high infill can sometimes lift or warp during printing. Use enclosures or draft shields as needed, depending on your printer and material.
Make the mold out of the right material. Mayku recommends that production molds be printed in nylon, which stands up best to the heat and stress a thermoforming mold will be put under. That being said, other materials will work for prototyping. In my experience, even a PLA mold (which deforms readily under thermoforming heat) is good for at least one molding.

Thermoforming open doors for an enterprising hacker, and 3D printing molds is a great complement. If you’re happy being limited to small parts, small “dental” formers like the one pictured here are available from every discount overseas retailer. And of course, thermoforming is great for costumes and props. If you want to get more unusual with your application, how about forming your very own custom-shaped mirrors by thermoforming laminated polystyrene?

Cart Cruises Abandoned California Rail

February 25, 2023 by Bryan Cockfield 20 Comments

Southern California is known for its nearly perfect year-round climate, excellent surf, and extremely high cost of living, but once you get away from the coast things are radically different. Rural California has huge tracts of land run by the Bureau of Land Management (BLM), which is publicly accessible to anyone willing to venture into the deserts. There’s not much in the way of infrastructure out there, but [Ryan] does have a unique way of traveling through it using abandoned railroad lines and this custom rail cart.

The frame of this cart is simple enough, it’s little more than 2×3 framing with a plywood deck. Some extra support is added for the motor mount and for the seating location. It uses slightly longer go-kart axles to accommodate the width of the railroad, and a small six horsepower gas engine with a single gear to power the rear axle. There are no brakes other than the riders’ shoes, and while this all seems straightforward enough the real hack here is [Ryan]’s custom wheels. He found that steel or cast wheels were not particularly comfortable on long journeys so after a few attempts he has come up with a home-built polyurethane wheel which is cast in a mold around a steel go-cart wheel and then trimmed on a lathe.

For pure exploration, there’s almost no better place to go than the American west thanks to all the public BLM land available. In this cart, you can explore long distances using an extremely low-cost method of transportation. We’ve added another video of [Ryan] exploring this area below the break to show the cart being used, too, but if you’d like a more multipurpose vehicle to use on abandoned rail near you, take a look at this bicycle which is converted to operate on the railroad.

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