How Does 3D Printing Work?

3D printing is an amazing technology that allows us to rapidly design and create physical objects, especially when injection molding processes take too much time or money to meet the need. If a design needs to be modified, or if you want something truly custom just for you, 3D printing is a much more realistic option.

For a quick rundown of how 3D printing works, take a look at our logo, which is a stylized 3D printer. Filament (plastic) is fed into a heated nozzle which then melts and is pressed onto the printer bed plate or a previously laid down layer of plastic. Many, many layers of plastic are built up on top of each other to create a final product. It’s a much slower process than injection molding, but there is no need to create expensive molds and the accompanying issues of scale when making a limited run or one-off item.

That’s the short version, and now for gory details!


We start with a .STL file, which is a solid three dimensional digital object. The file can come from a place like Thingiverse where somebody else already made it, or we can use our own Computer Assisted Design (CAD) software to make our own model.

At IGL Printing, we sell three kinds of prints:

  • Publicly available open source prints under a Creative Commons License
  • Licensed prints from professional 3D artists
  • Original designs which we have created in programs like Fusion 360.

The .STL is then loaded into a Slicer program, and this where a lot of art and science come together to get the best quality 3D print.


Slicers take the 3D model, and literally slice it up into multiple layers. These layers typically range from 0.1 mm to 0.3 mm in height. With shorter layers you get higher resolution (smooth lines), so this is commonly seen on parts where there are curves or high detail. Larger 0.3 mm layers have lines with lower resolution, but make much stronger parts.

Finished items are rarely solid. Instead they contain infill material arranged in a pattern such as honeycomb to keep the item strong but reduce the time and materials needed to make the object. The pattern and percentage of inner volume filled by the infill can range from as little as 5% to as much as 90% in certain prints. Our average print uses 15% infill. That might not seem like a lot, but it offers tremendous strength relative to the weight of the final product and the time needed to make it.

The slicer also allows the person who is actually printing the part to change a tremendous number of variables such as how wide each line is, how much hollow or partially filled space exists within the object, or how fast the filament and print head move.

An experienced printer can adjust these variables to meet the intended use of the product. Sometimes it makes sense to use thick layers and low infill. An object is rarely made better by being completely solid. A model can have a combination of thick thick and thin layers, different outer shell thicknesses, and changes in how much infill is used. All of these factors are controlled by the person who prepared the file to work on a specific printer, not the original artist.

A quality print depends on slicing that is specific to the design, the printer, and the type and brand of filament being used. This is why the same item found on Thingiverse can look really good coming from one printer but absolutely terrible from another shop.


Once all of the slicing is done, the easy part begins. Load the G-Code created by the slicer to the printer, and hit start. It’s not quite the replicator from Star Trek, but in minutes to hours (or even days) the print is complete.

The nozzle will lay down a first layer on a plastic coated steel sheet that’s 0.2mm thick. This first layer is pressed onto the sheet at a speed of 20 – 40 mm per second to ensure a solid bond to the plate. If this first layer isn’t fully set on the plate, it can later separate and cause the print to fail.

Once the first layer is complete, we can see speeds of anywhere from 20 – 200 mm per second for the nozzle depending on what part of the model is being printed. The slicer sets the nozzle speed differently based on which parts are infill, outer shells, or top surfaces.

Each layer typically prints in the following order:

  • Support Material
  • Inner Shell Layer
  • Outer Shell Layer
  • Infill

This provides a solid foundation for subsequent layers and provides the best appearance for the surfaces of the print.


Post-processing refers to any work done to a print after it is removed from the printer. This could be as simple as removing and small stringing plastic bits from the print. Support material is removed with pliers, cutters, and picks at this point. This step would also include any assembly, gluing, or painting if applicable.

That’s the basics of a how a 3D printed object is created here at IGL Printing. Please feel free to ask any questions in the comments below.

Leave a Reply