Fused deposition modeling (FDM), also known as fused filament fabrication (FFF), is the most widely used form of 3D printing at the consumer level, fueled by the emergence of hobbyist 3D printers.
This technique is well-suited for basic proof-of-concept models, as well as quick and low-cost prototyping of simple parts, such as parts that might typically be machined.
Consumer level FDM has the lowest resolution and accuracy when compared to other plastic 3D printing processes and is not the best option for printing complex designs or parts with intricate features. Higher-quality finishes may be obtained through chemical and mechanical polishing processes. Industrial FDM 3D printers use soluble supports to mitigate some of these issues and offer a wider range of engineering thermoplastics or even composites, but they also come at a steep price.
As the melted filament forms each layer, sometimes voids can remain between layers when they don’t adhere fully. This results in anisotropic parts, which is important to consider when you are designing parts meant to bear load or resist pulling.
Although the field of 3D printing has a lot of complexities, the theory behind the technology is elegantly simple. Instead of removing material from something larger to shape it—a method humans have used to create things for millennia—3D printing adds material to a manufacturing substrate, giving it the more technical term additive manufacturing.
It’s a quiet revolution, and now material innovations are driving the field to unimagined heights.
As a technology, 3D printing still has a lot of problems to iron out before it can become truly mainstream. And even then, it’ll only be as good as the materials. Many still equate 3D printing with polymers, an idea left over from the surge of consumer interest in the 2010s.
In reality, the history, applications, and materials used are much more far-reaching. And as other materials catch on in additive manufacturing, making stuff will become cheaper, faster, safer, and more sustainable.
Polymer plastics are still the most widespread 3D-printed material, but if you think they’re only good for fantasy chess pieces or cute desktop models, you might be surprised how versatile they are.
3D-printing polymers come in filaments or resins. As the name suggests, filaments come in long strings that are heated as they pass through the print extruder and shaped as they’re laid down on top of the previous layer.
Resin is used in stereolithography (SLA) or digital light processing (DLP), where the material comes from a tank of liquid resin and exposed to light as it extrudes, the light curing it into a solid layer as it’s laid down on the previous one.
So which is best? Filaments generally suit larger pieces that need to be stronger whereas resins suit smaller pieces that need less post-processing.
But aside from the material quirks inherent in the manufacturing process itself, the criteria used in traditional manufacturing can be broadly applied. Will the material be strong enough in a critical joint? Will a load-bearing surface take the mass of the rest of the object? Will it be flexible enough for the application?
The most widespread 3D-printing material, polylactic acid (PLA), is a biodegradable plastic made from renewable sources like corn starch. PLA has many benefits, such as a low melting point ideal for lightweight and consumer use. It’s also strong, doesn’t expand as much as other materials when heated, and has good adhesion to other materials.
It’s such a versatile manufacturing material that you might not realize there’s PLA all throughout your home and workplace in disposable cutlery, appliance and electronics parts, “scrunchable” plastic like food packaging, fishing line, diapers, feminine hygiene products, and more.
Acrylonitrile butadiene styrene (ABS) is suited to applications that need strength alongside flexibility—think Lego bricks. It’s durable, cheap, lightweight, and extrudes through a 3D printhead easily.
Because it’s as tough and rigid as it is cheap, ABS has better impact resistance and shock absorption than many polymers, which makes it great for products like bike helmets and golf-club heads.
It can also be injection-molded, so it suits slightly more outlandish shapes—think of musical instruments with complex inner structures, like clarinets or oboes; car bumper bars; and binoculars.
As the name suggests, this plastic is related to the polyethylene terephthalate of water and soda bottles but modified with glycol, hence the added “G.” It has high strength and flexibility, and when compared to the more widely used PLA, it has good temperature resistance.
PETG is ideally suited to applications that need to be sturdy and smooth and aren’t prone to excessive shrinkage. It has great adhesive properties, but because it’s “stickier” than most, clumping at the extruder nozzle can cause more problems than other polymers.
And because it can be sterilized, it’s considered the perfect plastic for food packaging.
Although there are many types, resin 3D printing refers to any process where liquid from a small tank is sent to the extruder to be heated or cured to dry, also called “vat polymerization.” Liquid resin is a photopolymer, which means it reacts/solidifies when exposed to light, and there are a couple of varieties.
Clear resins are used for small objects needing highly detailed surfaces or finishes. Colorless, see-through, light, smooth, and water resistant, they’re perfect for products that will be sanded or painted in post processing.
Most resin 3D-printed parts need some sort of clean-up to remove errant edges or excess deposits, a process usually done with alcohol solutions. Washable resins don’t need such chemical treatments—you can post-process them with water for a smooth finish.
Used when your final product needs to come back to its original shape after bending or compression, these rubbery resins are perfect for prototypes of handles, shock absorbers, or parts that need to withstand sustained twisting or flexing.
Resins are best suited to aesthetic parts and nonfunctional prototypes, and there are three major types of photopolymerization that create them.
Mirrors are used to direct one or several laser beams across the resin as it’s laid down on the bed of the printer, curing the object as each new layer is applied.
A flash of light cures or sets an entire layer in one go, directed to the build surface by a network of tiny mirrors.
Just like in stereolithography, except that a light source shines through an LCD screen that contains a mask of the single layer so the light can cure only that layer in each step.
Discussion about 3D printing today goes far beyond polymers, and that’s actually been the case for additive manufacturing’s entire history: The first movements in the field involved metal fabrication.
Now, many of the materials that have been used only in traditional manufacturing are in active development for the 3D-printed world.
One of 3D printing’s superpowers is composites, which can be used to mimic materials like marble, ceramic, and wood (though it’s not a huge leap to imagine a mysterious process of tomorrow that cures heated wood pulp instantly).
Wood filaments for 3D printing are about 70% PLA with 30% coming from sawdust or similar wood fibers.
The obvious benefit is that the end product looks, feels, and even smells like wood rather than plastic. It’s great for aesthetic uses and is also less brittle than PLA resin alone.
Just like in traditional manufacturing, carbon fiber is extremely strong but vastly lighter with the same performance, making it manna from heaven for the automotive, aviation, aerospace, and racing industries.
Carbon doesn’t melt until around 3,600 degrees Celsius, so it’s mostly out of reach for the consumer and prosumer market. It doesn’t shrink when it cools, which means your shaped layer will be closer to your final output. Carbon-fiber filaments also need more specialized handling, but it has the means to seriously disrupt the steel and iron supply chains.
Metal is harder to work with. It needs to be heated to a much higher temperature or forced through a 3D-printer extruder at much stronger force in powdered form. But that’s still far healthier for factory staff and the environment than huge, hot, dirty, smelly, and dangerous smelters.
There are moves to make the process more affordable and democratized, and instead of the voluminous infrastructure of silicon molds and glowing-hot molten iron, you can rapidly retool for low volume or specialty pieces.
There are also cost and volume savings to be made. For example, NASA used additive manufacturing to fabricate a rocket fuel pump with approximately half the parts of traditional methods.
In health care, metal is an ideal material for replacement bones or joints that have to stand up to the corrosive effects inside the human body. And to adorn the outside of the body, metal lets designers and customers make unique, 3D-printed jewelry.
When it comes to the new generation of 3D-printed materials, the most urgent need might be for construction materials.
The ability to build a 3D-printed house, which was done in Russia for less than $11,000 in 24 hours by a Boston company, has obvious benefits when compared to traditional building techniques, but there’s far more to it.
Globally, construction is responsible for 23% of air pollution, 40% of drinking water pollution, 50% of landfill, and 40% of greenhouse gas emissions.
3D-printed dwellings save money and time, which will allow for better-made low cost or emergency housing. There will also be far less need for hauling materials to sites and transporting waste out, making construction even more sustainable.
In fact, on-site additive construction has even been suggested as the most likely path to extraplanetary exploration and settlement.
Plenty of technologies have a blue-sky endpoint, and the journey toward that point can yield incremental benefits for society. 3D printing is no different.
Consider the future of subtractive manufacturing in a world with fully developed material science, where additive-manufacturing technology deploys from the smallest desktop unit to behemoths the size of aircraft hangars. Imagine a global, industry-wide, 1:1 manufacturing ratio, with the materials needed no longer exceeding the materials used, signaling an end to manufacturing waste.
Current recycling systems are far from perfect, and transporting by-products only adds to the carbon-emissions burden—it seems much better to remove them at the source where they’re created.
It’s also about prototyping far more cost-effectively. Tweaking a digital model and sending a new version to a 3D printer 1,000 times is still faster and cheaper than spinning up an entire live-production workflow just to perfect a single test piece.
What’s more, it enables an entirely new consumer paradigm of customization and print-on-demand, able to create bold, outlandish, or innovative new geometries.
Subtractive manufacturing by lathes or mills is great at making lots of one relatively simple thing. But—just like it applies to rapid prototyping—3D printing gives the ability to endlessly revamp a design to make a single object at virtually the same per-unit price as 10,000 of them.
And because it adds material instead of subtracting it, 3D printing can make endlessly variable and unusual shapes that can’t be achieved with even the most precise CNC machine tools. That’s especially the case when you add concepts like generative design, which can take so much of the heavy computational lifting of design out of human hands.
And, finally, it gives you a much faster time to market, whether you’re prototyping in a small studio much more responsively than in a major production environment or building comfortable dwellings in days to help families unhoused by a natural disaster.
Because of the capabilities and advances in materials, 3D printing has already changed several industries forever.
In manufacturing, it’s not an either-or proposition of using subtractive or additive methods. A London design company is already deploying a huge additive-manufacturing tool in traditional factory settings to create a hybrid model.
It’s also expanding the possibilities for what can be made. Health care is a great example, where additively manufactured skin, titanium bones and joints, and even blood vessels count among the innovations.
The construction innovations are even more advanced—and have great potential to change the industry. Additive practices are already established enough for calls to properly regulate the field with relevant and updated building codes.
To benefit the social good, you can start with the fact that dwellings are expensive. Lots of people simply can’t afford them, so if it’s possible to build a home in a single day for the cost of a decent second-hand car, this could help lift tens of millions out of poverty.
Additive manufacturing also offers efficiencies regular construction doesn’t. Housing is normally built in a linear process: erecting the frame, laying bricks, applying roof trusses—all readying the project for glaziers and plumbers to work on later.
But as far back as 2016, a unique multi-material additive method was expanding 3D printing’s capabilities. Assuming the science can work with any possible material, imagine a future where a printer can run off a home’s wall complete with electrical wiring, air conditioning piping, window glass, and paint in one step?
Additive technology still seems futuristic to many, but you’d be surprised how many of your favorite products already use 3D printing. And that’s before discussing the futuristic materials that might one day enter your home on a mass scale when additive manufacturing can use them effectively.
Just like pioneers of generations past have forged new paths for additive manufacturing with wood, metal, and beyond, there’s a tinkerer somewhere in a garage today doing the same thing with aerogel, graphene, carbon nanotubes, electronics-embedded fabrics, or some other substance that will become commonplace in the years to come.
This article has been updated. It was originally published in November 2014. Jeff Yoders contributed to this article.
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