3D Printing for Preppers: Funding Casting with PolyCast Filament –

3D Printing for Preppers: Investment Casting with PolyCast Filament -

While my humble family has not yet been struck by a disaster, there is no shortage of emergencies worldwide, and the COVID-19 pandemic has shown how useful even desktop 3D printing can be in disaster situations. Given the ability to review an Ultimaker S3 3D printer and several unique filaments, I thought I’d explore 3D printing simple goods that might come in handy in emergency situations to get an idea of ​​how useful a desktop 3D is -Printer could be.

As well as providing an overview of the subject, I also reviewed the Ultimaker S3 and spoke to Ultimaker about using desktop 3D printers in emergency and disaster scenarios. I also had the opportunity to test out some copper filaments from The Virtual Foundry that were sintered by Sapphire3D. I spoke to the manufacturer about the material as well as its myriad other unique metal filaments.

We tested the Ultimaker S3 device.

While metal filaments open up some interesting opportunities for making metal parts with a desktop 3D printer, some additional equipment and expertise is required to be able to make suitable parts. However, there is a 5,000 year old process that recently received a 3D printed makeover that anyone with a home 3D printer can try if they’re careful.

I’m referring to investment casting, of course. The oldest discovered object made with lost wax casting is a 6,000 year old amulet from the Indus Valley Civilization, a Bronze Age society in northwestern South Asia. The technique is to make a model out of a material like wax before making a mold from that model, and then pour molten model into the mold to create a solid metal replica. Obviously, these are more specific details than given here, and we’ll get to them a little later.

The oldest known piece of lost wax casting, a 6,000 year old amulet from Mehrgarh (today’s Pakistan). Image courtesy of Nature Communications.

As one of the oldest metal-making methods, it comes in many forms. Although the models were originally made by hand from clay or wax, 3D printing has lowered the barrier to artistic skill required to create these designs. It is now possible to take a model from an online repository, create a replica of a physical object with 3D scanning, or use CAD tools to design something to be cast.

There are also a number of 3D printers and materials available for exactly these purposes. For professional applications such as jewelry or tooth crowns, vat photopolymerization (digital light processing) [DLP] and stereolithography[SLA]) or inkjet 3D printing (solidscape wax printing) are usually the technologies of choice as they can achieve much higher resolution with the right materials. Inexpensive material extrusion (production of molten filaments) [FFF]) and DLP systems can also make models for casting.

As an FFF printer, the Ultimaker I tested had far fewer material options to choose from when compared to cheap DLP machines. Typically, DIY casting enthusiasts have used your standard PLA or flexible filaments to print their first models. However, there are some filaments specifically designed for casting on the market. The two most notable are MOLDLAY by Kai Parthy and PolyCast by Polymaker.

PolyCast 3D printing filament for casting Polymaker. Image courtesy of Polymaker.

The Polymaker team were kind enough to send me a free sample of their polycast material to try out. This filament is designed to have so-called low burnout, as only a minimal amount of ash remains when it is poured. In this way, when pouring into the mold, the liquid metal does not receive any defects from dirt in the mold cavity. For this reason, it is also important to post-process prints, sand down support structures and polish them smooth. This ensures a smoother cast object with fewer defects.

By this point in the verification process, I had clogged my second nozzle sufficiently that I no longer had access to detachable supports. I didn’t want to risk having too many flaws from PolyCast supports, so I printed objects with no overhangs. These should still be useful in an emergency. I chose a wrench and surgical retractor, the same models as the ones I made from PLA in a previous article in this series.

A surgical retractor and wrench 3D printed by PolyCast.

Printing was as easy as PLA. Since the material was in a sealed bag with desiccant, there was no problem with moisture. I just added the PolyCast printer profile to Cura and when the Ultimaker started the profile was loaded. After loading the filament, the printer had no problems at all.

The hard part came when I had to cast the prints. With a toddler and baby at home and quarantined during a deadly pandemic, creating your own casting station isn’t easy or safe, but I’ve thought about it. I’ll explain below how some people approached their own casting (somewhat interesting) before I got into it (less interesting). This is not a guide as I did not conduct the casting myself, but should be informative enough to give readers a sense of how it is being conducted.

Based on numerous online accounts, doing your own casting isn’t difficult if you take the right precautions, and it’s pretty doable in an emergency situation. As the video below shows, it’s actually possible to build a backyard foundry for under $ 20 to make ingots from aluminum cans.

This video shows that you can even make one with a soup can:

Once you have a model that you want to water, you need to make a tree. This wax structure holds the figure in place and burns out when pouring with the model. This process, known as spruing, is typically performed with a wax stick and wax wires that are fused together. However, it is also possible to 3D print the sprues directly with your model if you have CAD (or automated software) skills.

With the positive pattern from the last part, the next step is to create a negative. You can buy casting kits that come with all of the equipment you need, but you can also buy and make a lot of what is needed for reasonably priced. Basically, you need a container and medium that can withstand the heat of the molten metal that is poured into your mold.

Plastering process for investment casting with 3D printed samples. Picture one shows a 3D printed part in a drywall tray. Picture two, this tub as soon as the embedding plaster has been poured in. Picture three, the mold removed from the tub. Images courtesy of user Scottiek on Instructables.

I’ve seen a home improvement worker use a drywall tub on the container and enough investment plaster to protect the tub from heat. The model is then placed in the container and dipped in investment plaster, a toxic material that requires goggles, gloves, an N95-style respirator, and a well-ventilated area. Some home improvement makers have made their own investment plaster by mixing hobby plaster with fine quartz sand.

If you’re using a larger container, at the end, take your plaster cast out of the container and follow the steps below. However, if you use a sufficiently small steel container, this could be your piston going into an oven with the plaster of paris and the 3D printed pattern.

The key to a good final cast is eliminating air pockets from the slurry, which requires the use of a vacuum chamber. One caster, Adam Zeloof, relied on a mechanical pump attached to a coffee can before pouring it into the container you use for your mold. Another method is to clean the 3D printed part with isopropyl alcohol immediately before coating it with the embedding plaster.

Both techniques are designed to prevent bubbles from forming in the next step. In this case, put your 3D print with sprues in your container and fill the area with investment plaster. The plaster then hardens overnight.

Once you’ve hardened the plaster of paris mold around your 3D printed pattern, you can heat it in an oven or oven to burn out the pattern. This leaves a negative that you then fill with molten metal. Yes, that means we are almost at the direct production step. This requires heating metal to its melting temperature, whether through a backyard forge or a store-bought furnace, and then pouring it into the mold.

Adam Zeloof pours molten metal into a fine plaster mold, into a steel piston and onto his vacuum chamber for coffee pots. Image courtesy of Adam Zeloof / Hackaday.

The Zeloof mentioned above explains that there are different techniques to achieve the best metal part, as simply tipping the molten metal into the mold may not result in an even coating and pouring. His preferred method is to use the same DIY vacuum chamber, which consists of a pump and a can of coffee.

Once the metal has cooled, the shape can be dropped into a bucket of cold water. The plaster mold will break apart to reveal a metal replica of your 3D printed part as well as sprues. Finally, you need to saw off the sprues and polish the part.

It’s a bit of a complicated process, especially if you haven’t already done it, but once you get the hang of it, once you have the supplies and workspace it doesn’t seem too difficult. Although there is obviously a lot of trial and error and expertise to actually do a decent job. Then again, I didn’t!

What I did was find the nearest casting shop. Since I live in a remote part of the country, I had to send my 3D printed parts to Reinmuth Bronze Studio a few hours north of where I live and have them professionally staffed. In an SHTF scenario, a two hour drive for an emergency part might not be bad. When I worked for a medical clinic in a rainforest in Bolivia, it was a pretty normal standard for bringing a patient into town when the equipment or expertise needed wasn’t available in the middle of the jungle. Of course, it all depends on the scenario.

My last parts are cast in bronze.

Casting these two pieces in bronze cost $ 118. They arrived in very good condition and I learned that due to the presence of copper in bronze, they may even have some antibacterial properties. If I were a prepper I would definitely want to build my own forging and casting station where I could melt aluminum cans in my garden.

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