So what's on the inside of all 3D printed objects? All we get to see is what's on the outside. What does the 3D printer do for the inside?
Well, the inside part is what we call infill. The infill provides a structure for the inside of the 3D printed object that will serve as support for the outside layers. The infill will provide extra strength and rigidity for the object.
Just like other aspects of a 3D printing, the infill can be configured for a print in slicer software (as mentioned in my other posts "About Scaffolds/Supports" and "Design Process"). Typically, there are two settings to consider: percentage of infill and infill pattern.
Infill percentage determines the amount of infill. 0% means no infill while 100% means a solid object. The trick is balancing the the amount of infill vs. efficient use of material. The more infill that is selected, the more material that is used. It is possible to provide a structurally sound and strong object without making a solid infill.
Infill pattern dictates the arrangement or shapes in which the infill will be printed. Different patterns have their own sets of pros and cons regarding strength, print time, and the amount of material used. Examples include honeycomb, rectilinear, grid, and triangular.
Infill percentage combined with pattern will determine what the inside of your printed object will look like. A smaller percentage will create larger patterns while larger percentages will create smaller patterns. This will also determine the weight of the object: larger patterns create larger gaps for trapping air where smaller patterns use more material adding more weight.
In case you haven't gotten your "fill" on infills, the following link on 3DPlatform.com has some great pictures to illustrate the different percentages and patterns: https://3dplatform.com/3d-printing-tech-tips-infill-percentage-and-pattern-explained/.
Thanks for your interest!