How Exactly Does 3D Printing Work?

3D printing offers unprecedented opportunities for manufacturing in many industries, but how does it work?
Christopher McFadden

3D printing is a highly versatile method of production and rapid prototyping. Over the last few decades, it has been making waves in many industries around the world.

3D printing is part of a family of manufacturing technology called additive manufacturing. This describes the creation of an object by adding material to the object layer by layer. Throughout its history, additive manufacturing has gone by various names, inlcuding stereolithography, 3D layering, and 3D printing, but 3D printing is the best-known.

So how do 3D printers work? 


How does a 3D printer work?

The process of 3D printing begins by making a graphic model of the object to be printed. These are usually designed using Computer-Aided Design (CAD) software packages, and this can be the most labor-intensive part of the process. Programs used for this include TinkerCADFusion360, and Sketchup.

For complex products, these models are often extensively tested in simulation for any potential defects in the final product. Of course, if the object to be printed is purely decorative, this is less important. 

One of the main benefits of 3D-printing is that it allows the rapid prototyping of pretty much anything. The only real limitation is your imagination.

In fact, there are some objects that are simply too complex to be created in more traditional manufacturing or prototyping processes like CNC milling or molding. It is also a lot cheaper than many other traditional manufacturing methods.

After design, the next phase is digitally slicing the model to get it for printing. This is a vital step as a 3D printer cannot conceptualize a 3D model in the same way as you or I.  The slicing process breaks down the model into many layers. The design for each layer is then sent to the printer head to print, or lay down, in order. 

The slicing process is usually completed using a special slicer program like CraftWare or Astroprint. This slicer software will also handle the "fill" of the model by creating a lattice structure inside a solid model for extra stability if required. 

This also happens to be an area where 3D printers excel. They are able to print very strong materials with very low densities through the strategic addition of pockets of air inside the final product.

The slicer software will also add in support columns, where needed. These are required because plastic cannot be laid down in thin air, and the columns help the printer to bridge the gaps. These columns are then later removed if needed.

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Once the slicer program has worked its magic, the data is then sent to the printer for the final stage. 

how 3d printers work

From here, the 3D printer itself takes over. It will begin to print out the model according to the specific instructions of the slicer program using different methods, depending on the type of printer used. For example, direct 3D printing uses technology similar to inkjet technology, in which nozzles move back and forth, and up and down, dispensing a thick waxes or plastic polymers, which solidify to form each new cross-section of the 3D object. Multi-jet modeling uses dozens of jets working simultaneously, for more rapid modeling.

In binder 3D printing, the inkjet nozzles appliesa fine dry powder and a liquid glue, or binder, that come together to form each printed layer. Binder printers make two passes to form each layer. The first pass deposits a thin coating of the powder, and the second pass uses the nozzles to apply the binder. 

In photopolymerization, drops of a liquid plastic are exposed to a laser beam of ultraviolet light, which converts the liquid into a solid. 

Sintering is another 3D printing technology that involves melting and fusing particles together to print each successive layer. The related selective laser sintering relies on a laser to melt a flame-retardant plastic powder, which then solidifies to form the printed layer. Sintering can also be used to build metal objects.

The process of 3D can take hours or even days, depending on the size and complexity of the project.

"There are some faster technologies making splashes in the industry, like the Carbon M1, which uses lasers shot into a bed of liquid and pulls the print up out of it, speeding the process up significantly. But these kinds of printers are many times more complicated, much more expensive, and only work with plastic so far." -

No matter which type of 3D printer is used, the overall printing process is usually the same.

  • Step 1: Produce a 3D model using CAD software. 
  • Step 2: The CAD drawing is converted to the standard tessellation language (STL) format. Most 3D printers use STL files in addition to other file types such as ZPR and ObjDF.
  • Step 3:  The STL file is tranferred to the computer that controls the 3D printer. There, the user designates the size and orientation for printing. 
  • Step 4: The 3D printer itself is set up. Each machine has its own requirements for setup, such as refilling the polymers, binders and other consumables the printer will use. 
  • Step 5: Start the machine and wait for the build to complete. The machine should be checked regularly during this time to make sure there are no errors.
  • Step 6: The printed object is removed from the machine. 
  • Step 7: The last step is post-processing. Many 3D printers require some type of post-processing, such as brushing off any remaining powder or washing the printed object to remove water-soluble supports. The new object may also need curing.

What can a 3D printer make?

As we have already seen, 3D-printers are incredibly versatile. They can, in theory, create almost anything you can think of. 

But they are limited by the kinds of materials they can use for "ink" and by their size. For very large objects, say a house, you would need to print individual pieces - or use a very large 3D printer

3D printers are able to print in plastic, concrete, metal and even animal cells. But most printers will designed to use only one type of material. 

Some interesting examples of 3D-printed objects include, but are not limited to: -

  • Prosthetic limbs and other body parts 
  • Homes and other buildings 
  • Food
  • Medicine 
  • Firearms
  • Liquid structures
  • Glass products
  • Acrylic objects
  • Movie props
  • Musical instruments 
  • Clothing
  • Medical models and devices

3D printing clearly has applications in many industries. 

What are some types of 3D printing software?

Different CAD software will use a variety of file formats but some of the most common are: 

  • STL - Standard tessellation language, or STL is a 3D-rendering format that can usually only handle a single color. This is typically the file format most desktop 3D printers use. 
  • VRML - Virtual Reality Modeling Language,  VRML file is a newer file format. These are typically used for printers with more than one extruder and can handle multi-color model creation.
  • AMFAdditive Manufacturing file format, this is a .xml based open standard for 3D printing. It can also support multiple colors. 
  • GCode - GCode is another file format which can contain detailed instructions for the 3D printer to follow for laying down each slice. 
  • Other formats - Other 3D printer manufacturers also have their own proprietary file formats. 

What are the benefits of 3D printing?

As we have already touched upon above, 3D printing can have various advantages over more traditional manufacturing processes like injection molding or CNC milling. 

3D printing is an additive process, rather than subtractive like CNC milling. 3D printing builds things up layer-by-layer while the later gradually removes material from a solid block to create a product. This means that in some instances, 3D printing can be more resource-efficient than CNC. 

Another example of traditional manufacturing processes, injection molding, is great for making lots of objects in large volumes. While it can be used for creating prototypes, injection molding is best suited for large scale mass production of approved product design. However, 3D printing is better suited for small-scale, limited production runs or prototyping. 

Depending on the use, there are some other advantages of 3D printing over other production processes. These include, but are not limited to: 

  • Faster production - While slow at times, 3D printing can be quicker than some conventional processes like injection molding and subtractive production. 
  • Easily accessible - 3D printing has been around for a few decades now and has exploded since around 2010. There are now a wide variety of printers and software packages available (many are open-source) making it easy for almost anyone to learn how to do it.
how 3d printers work pros
Source: Pixabay
  • Better quality products - 3D printing produces a consistent quality of product. So long as the model is accurate and fit for purpose, and the same type of printer is used, the final product will usually always be of the same quality. 
  • Great for design and product testing - 3D printing is one of the best tools for product design and testing. It offers opportunities to design and test models to allow refinement with ease.
  • Cost-effective - 3D printing, as we have seen, can be a cost-effective means of production. Once the model is created, the process is usually automated, and raw material waste tends to be limited.
  • Product designs are almost infinite - The possibilities of 3D printing are almost limitless. So long as it can be designed in CAD and the printer is big enough to print it, the sky is the limit. 
  • 3D printers can print using various materials - Some 3D printers can actually blend or switch between materials. In traditional printing, this can be difficult and expensive.
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