The shell refers to the outer wall structure of a 3D printed object, consisting of the perimeters that define the external shape and provide structural integrity. The shell is what gives the print its visible surface and much of its strength, making it a critical component of any 3D printed part.
The shell is composed of perimeters, which are the continuous lines that trace the outline of each layer. The number of perimeters determines the thickness of the shell walls. Common settings range from 2-4 perimeters, with more perimeters providing greater strength and better surface quality but using more material.
The outer perimeter is the most important as it defines the visible surface of the print. It's typically printed at a slower speed than inner perimeters to ensure better surface finish. Inner perimeters provide structural support and help maintain dimensional accuracy.
Shell settings can be fine-tuned in the slicer software. Parameters include the number of perimeters, perimeter speed, and perimeter overlap with the infill. The overlap ensures good adhesion between the shell and the internal infill structure, which is crucial for overall part strength.
For functional parts that need to bear loads, thicker shells (more perimeters) are generally better. For decorative objects, fewer perimeters may be sufficient. Some slicers also offer variable shell thickness, where the number of perimeters can change based on the geometry or stress requirements of different parts of the model.
The shell works together with the infill to provide the overall strength and structure of the printed object. A well-configured shell with appropriate infill density ensures that the part will be both strong and efficient in terms of material usage.
