How Does a 3D Printer Work?


How does a 3D printer work?

3D printing is an incredible technology. 3d printer have the potential to alter every aspect of how we make, use, and think of the physical objects around us in our daily lives.

Before describing how a 3D printer works, though, it’s helpful to go back a bit and explain what 3D printers are and where they came from.

What is 3D printing?

In its simplest form, 3D printing does for computer-generated objects what paper printing does for computer-generated text. It transforms data visualized on a monitor into an object that can be held in your hand. It’s both that simple and that extraordinary.

The process of 3D printing originally evolved from the same technology as the printing of text. Printers that were originally designed to lay down layers of ink from inkjets, were modified to instead spray layers of a binding material down onto a layer of powder. The binder would solidify the powder in precisely the way the printer heads defined, and when the excess powder was blown away, a solid object would remain. This is why the term “3D printing” remains popular today, although the technologies have evolved greatly since then, and many techniques no longer resemble paper printing so closely.

3D printing was revolutionary in two ways:

  • It enabled people to create physical objects from digital ones, without going through the lengthy traditional manufacturing process
  • It creates objects in an additive method, instead of a subtractive method. (For example: When a woodworker seeks to make a wooden spoon, they start with a stick and then whittle away the excess until a spoon remains. A sculptor chips and hammers and sands a block of marble until only a statue remains. A drill or lathe strips material from a rod of metal until only a screw remains.)

These traditional methods of making something involve removing excess material until the desired shape is achieved. But 3D printing is additive: Material is laid down and built up in successive layers, creating the desired final shape with little to no excess or waste.

In the past, manufacturing an object required an array of different tools, depending on the desired object and the material you were working with. Manufacturing specialized objects often takes a long time, because first the factory has to manufacture the necessary tools in order to remove precisely the amount of material required from the raw object. This new method of manufacturing objects much faster, without requiring the prerequisite manufacturing of tools, is why 3D printing also became known as “rapid prototyping.”

Origins and history of 3D printing

Today, 3D printing technology is highly complex and specialized, due to the variety of materials, methods, and terminologies used. Once again, it’s helpful to look back at the origins of the current technologies in order to understand all the different terms and processes used in 3D printing today.

Here’s a brief timeline of 3D printing.

1980s

Hideo Kodama of Nagoya Municipal Industrial Research Institute in Japan invented an additive prototyping method, in which a vat of photopolymer material was selectively exposed to UV light that hardened the material in successive layers. The UV light was masked to define the specific shape the polymer would harden into, successively creating the desired 3D object.

Alain Le Méhauté, Olivier de Witte, and Jean Claude André from the French National Center for Scientific Research designed a system in which two lasers crossed beams, and thus hardened a liquid monomer into a solid polymer at the precise laser intersection. By building each layer one at a time, their method leveraged laser printing technologies to construct a solid object.

Patent for first commercial 3D printer

Chuck Hull, a US-based physics engineer was working in a company where household objects were made more durable by applying an outer layer that was toughened and cured with UV lamps. Frustrated with the lengthy process (sometimes as long as two months) to prototype small plastic parts for new product designs, he began to experiment. He developed acrylic-based photopolymers that remained liquid until selectively exposed to UV light, at which point they would solidify. His method also used layers, or bottom-up cross-sections, of the desired finished object. His stereolithography process and 3D object file format are still widely in use today.

While Hideo Kodama could be credited with the invention of the first 3D printer, Chuck Hall was the first to receive a patent. Find out more about when the first 3D printer was made.

Carl Deckard, a mechanical engineering undergraduate at the University of Texas, developed Selective Laser Sintering (SLS) technology. With SLS, a laser is aimed at a point in space defined by a computer CAD model, and powdered polyamide material is hardened into a solid structure at the points defined by the laser.

1990s

Scott Crump, a mechanical engineer, created the first operational Fused Deposition Modeling (FDM) printer, in which special coils of thermoplastic filaments are hardened as they pass through a printer head. The printer head moves through space, extruding the filament as it goes, and leaving behind a length of hardened plastic filament that defines a shape in space.

Researchers at MIT developed a powder-bed system in which inkjet-like printer heads moved across a layer of powder substrate. As the printer heads moved, they selectively bound and hardened the powder into a solid, then another layer of powder was added, and another pass was made by the printer heads, successively building an object. It is this process that coined the term “3D printing” and is widely used today due to the range of colors and gradations available for the final product.

Royden Sanders began marketing a desktop printer that used dots of wax to create high-precision solid wax objects, which could then be used for wax casting and molding.

Throughout the mid-to-late 90s, more techniques and technologies were developed, using different substrate materials, different printing technologies, and different hardening techniques. People began including sacrificial and support materials in their 3D designs, increasing the range and complexity of solid objects that could be produced with these techniques.

This was also the time 3D printers were first used in medicine.

2000s

While the 90s saw an explosion of methods and techniques, the 2000s were the decade in which 3D printing saw an exponential increase in practical applications. Companies in all aspects of commercial manufacturing began applying these technologies in different ways, and industries as diverse as design, food, health care, fashion, construction, and firearms began employing 3D printing, rapid prototyping, or additive manufacturing techniques.

Today

The sudden expansion of 3D printing methods and technologies all over the world have left us with a nearly bewildering array of different machines and techniques that are specialized for slightly different end applications.

Terms

We also have these three terms that are often used interchangeably:

3D printing

Originally used to describe machines that operated much like a traditional printer, but instead built up solid 3D objects, this term is now more generally applied to all processes that build objects out of computer data.

Rapid prototyping

This term generally refers to the ability to quickly produce unique, custom, or one-off-designs, regardless of the specific 3D prototyping technology employed.

Additive manufacturing

This term generally refers to the process of making objects with additive methods, rather than subtractive, regardless of the specific 3D technology employed. This term is also used because these kinds of objects are made at scale and volume, in a factory setting, rather than the small numbers of objects produced in prototyping.

How 3D Printing is Done

As we have seen, there are a variety of different specific 3D printing machines and technologies, but the basic principle is that a plastic or polymer material is converted from liquid or powder form, into a solid form, by specific application of light, heat, or a hardening agent to layer after layer of the substrate material. But all 3D printing begins with a 3D model.

3D modeling

3D modeling is the creation of a virtual object within a specialized 3D software. It can be done at home using a number of different software applications. Or pre-made 3D models can be downloaded or purchased from websites that offer these models. And 3D models can also be made from 3D scans and photographs, with technology designed to digitize real-world objects.

However, software designed to make a 3D model that looks good on screen, the kind of model one might use for a visualization, animation, or rendering, isn’t generally immediately suited for printing on a 3D machine. Before converting a Maya, CAD, or Blender file into an STL file for printing, it must be first checked for errors that will keep the model from printing correctly. Files created from real-world scanning are particularly susceptible to these errors.

Common 3D model errors include:

  • Holes in the mesh
  • The model intersects itself
  • Errors in the geometry

There is software available that will identify and help you correct errors in your 3D file before exporting the STL, but these repair tools are more limited in function than the original 3D software used to make the model. It is better to have the model as clean and correct as possible before using one of these checking tools, and then export the STL file.

Then a third piece of software, known as a “slicer,” will process the virtual object in the STL file and create all the individual cross sections necessary for the layering process of 3D printing. This “sliced” settings and file format depends on which specific model of 3D printer the file is destined for.

3D printing

3D printing itself can take anything from several hours to several days to complete, once you have sent your sliced file to the printer. There are currently nine different types of 3D printer, and each type is produced by different companies who have different printer models and product lines, leading to a proliferation of 3D printers on the marketplace. Each one uses different materials and different processes, making each one better for some applications than others. The types of 3D printer are:

  • Stereolithography (SLA)
  • Digital Light Processing (DLP)
  • Fuse Deposition Modeling (FDM)
  • Selective Laser Sintering (SLS)
  • Selective Laser Melting (SLM)
  • Electronic Beam Melting (EBM)
  • Laminated Object Manufacturing (LOM)
  • Binder Jetting (BJ)
  • Material Jetting (MJ)

Here’s a brief overview of how these methods work.

SLA

Resin Based 3D Printing

Converts liquid photopolymers into solid 3D objects, one layer at a time. The polymer is heated to a semi-liquid form, then hardens on contact with a mirror-guided UV laser. The printer creates objects from the bottom up, with a series of thin layers of polymer exposed to the laser in sequence.

DLP

Converts liquid photopolymers into solid objects using arc lamps instead of lasers. Every successive layer of resin is exposed to a masked light source. This is faster than SLA, because the layer is exposed to the light source all at once, instead of traced along a path with a laser.

FDM

How does a 3D printer work?

Builds objects one layer at a time by heating and then extruding thermoplastic filament onto the build surface. Objects are basically drawn into place by the print head placing plastic that solidifies in the air.

The most popular materials used in FDM printing is Acrylonitrile Butadiene Styrene (ABS) and Polylactic Acid (PLA). Check out this comparison of the strength of printed objects that use PLA vs ABS.

SLS

Laser sintering

Uses a high-powered CO2 laser to sinter solid materials out of powder. A fabrication bed is filled with powdered metal, nylon, ceramic, or glass. The laser beam solidifies the powder into a solid form. The bed is lowered incrementally, another layer of powder is added, and another pass of the laser hardens that powder, and so on. As the 3D object is built, it is always surrounded by an ever-deepening bed of powder, making this method require fewer supporting structures during the printing process.

SLM

This method is almost exactly like SLS, except that instead of simply sintering the powder into a solid, the laser melts the powder into a solid, resulting in a finished object that is structurally stronger than SLS.

EBM

Like SLS and SLM, EBM uses a powder bed and selective exposure to create solid objects. However, instead of using a laser like SLS and SLM, EBM uses a powerful electron beam in a vacuum to harden the powder material. EBM requires less equipment than laser methods.

LOM

Layers of paper or plastic are laminated down, then a laser cuts the desired shape, then another layer is added and cut, and so forth. This technique is both additive, since layers of paper or plastic are built up over time, and subtractive, since the desired shape is cut out of the layer.

BJ

Like SLS, SLA, and EBM, with BJ printing objects are formed in a powder bed. However, instead of sintering or melting the powder, inkjet-like heads extrude a liquid bonding agent, like a glue, that binds the loose powder together and adheres it to the layer below. This method allows for full-color object printing, since CMYK pigments can be added to the binding agent.

MJ

Printer-like nozzles heat wax or polymers and then sweep across the build platform, depositing tiny drops of wax or polymer precisely in layer after layer. The wax or polymers cool upon exposure to air, solidifying naturally or with the assistance of UV light, until the final object is constructed.

Finishing

Remember that even if you sent your files electronically to a company to 3D print the object for you, you will still need to finish it. Regardless of the specific printing method used, most 3D printers create an object with some degree of visible lines on the surface, due to the layered construction. And some 3D objects require support structures, necessary during the printing process, that can be removed after printing is complete. In any case, it is almost always necessary to clean and smooth the surface.

Smoothing can be done in a variety of ways, depending on the material used in the 3D process. It is frequently done with sanding, but some polymers can be smoothed with solvents like acetone.

The degree of sanding, filling, priming, and painting depends to a large degree on the printer used and the object created. However it’s often a necessary step for achieving a professional-looking prototype.

How to use a 3D printer

Today, makers and hobbyists are using 3D printers at home, employing a simpler version of the process described above. For the average home user, here’s how to use a 3D printer.

Get or create a 3D model

Existing 3D models already optimized for printing can be found on websites (Thingiverse and MyMiniFactory are my favorites), forums, and community pages for 3D enthusiasts. These models are a great place to begin. Not only do you not have to learn how to use 3D software, but the fixing and troubleshooting has already been done.

Creating your own 3D model involves learning a software like Blender (free), Solidworks, AutoCad, Zbrush, etc. For the beginner, Meshmixer is a good choice, because it is specifically designed for making objects for printing, meaning that there is reduced chance for errors when the design is exported to the printer. Also, MeshMmxer is free. Once you have a finished model, you will export it as an OBJ or STL file to a slicer program. The slicer will slice it and optimize the image for 3D printing. Cura is a popular slicer choice, but if you own a 3D printer, the manufacturer may recommend particular print-prep software.

Send the file to your printer

This is frequently done with a physical SD card, but sometimes you can transfer files via USB or Wi-Fi, depending on the model of printer. Octoprint can be used to send files by Wi-Fi if you printer does not support Wi-Fi directly. If you have a consumer desktop 3D printer, it is probably the FDM type. In these printers plastic filaments are heated and traced onto the build surface, creating your 3D object. Many of these printers will evaluate your file and give you an estimate of how much filament you will need to complete the object, and how long it will take.

Make sure you have enough filament material, in order to avoid running out or experiencing an error halfway through printing. Start the job, and then wait. It generally takes a number of hours to finish a build, depending on size and complexity of the desired object.

If you don’t have your own personal 3D printer, you can send your finished 3D file to an online service that will print it for you.

Finish your object

Whether you’ve opened a shipping box or your own printer, your object still needs to be sanded, primed, painted, or otherwise treated to have a smooth, professional appearance. I have had good luck using Filabot XTC24 XTC-3D High Performance Print Coating, which fills in the print lines and give a smooth glossy surface.

What is 3D printing used for?

3D printers are used in an enormous variety of ways, for a broad range of applications.

  • Jewelry making: 3D printers make molds and casts for custom jewelry
  • Dentistry: 3D printed perfectly-fitted orthodontic devices
  • Manufacturing: 3D printing to build custom tools
  • Food: 3D print unique chocolates and candies using edible filament instead of plastic
  • Fashion: 3D print custom-fitting athletic shoes
  • Optometry: 3D print eyeglasses on demand
  • Cars, trucks, and aircraft: 3D printing is used to streamline and strengthen bodies and fuselages
  • Medicine: 3D print customized surgical tools and medical implants

Currently, researchers are exploring the use of 3D printing in biotechnology, hobbyists use it to create personalized toys and decorative objects, schools are using it to create low-cost scientific equipment for the classroom, museums and anthropologists are using it to study and re-create cultural artifacts. The applications for these technologies seems virtually endless.

Many researchers imagine a future in which every home has a 3D printer, and every one downloads the plans for objects and devices from the cloud, then customize and produce them on demand in the home. This idea has the potential to transform not only the manufacturing industry, but also shipping, retail, and logistics industries globally.

Conclusion

3D printing is an exciting technology. It has the potential to transform how we think of objects, how we make them, and how we use them. These devices are continually lowering in price, making it easier than ever before to explore this whole new way of manufacturing and prototyping. Create and share your own unique designs, and prepare yourself for the world of the future.

Check out “How hard is it to use a 3D printer?”

And remember to check out our list of the best 3D printers.

Verl Humpherys

I have been 3D printing since 2017, using both FDM and SLA printers. My prints have varied from small D&D figurines to full sized baby Groot. I printed mounts for my various game consoles and my Oculus Rift. Any problem you can have with a 3D printer, I have had. And I am here to tell you what I have learned.

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