The Perimeters vs Infill Myth
When engineers need a stronger part, their instinct is often to bump infill from 20% to 70% or 100%. In finite element and destructive testing, this is one of the least efficient ways to add strength.
Structural rigidity in bending is governed by the moment of inertia (I = b*h^3 / 12). Material placed at the outer boundary resists bending stress far more effectively than core material. Increasing wall perimeters from 2 to 4 or 5 walls yields 2-3x greater rigidity than doubling infill density-while printing substantially faster.
Evaluating Popular Infill Patterns
- Gyroid: The modern benchmark. Based on minimal surfaces, Gyroid provides isotropic (uniform in X, Y, and Z) mechanical strength, does not cross toolpaths on the same layer, and allows easy resin or moisture drainage. Best for structural parts.
- Grid / Cross-Hatch: Fast and simple, but toolpaths cross each other at 90° intersections on the same layer, causing nozzle clicking, nozzle drag, and vibration.
- Honeycomb: High strength-to-weight ratio, but requires frequent printhead direction changes that increase print time and machine wear.
- Support Cubic: Varies infill density automatically, printing sparse infill at the bottom and dense infill near top surfaces. Excellent for rapid concept prints.
Recommended Production Settings
For functional brackets: 4 perimeters, 4 top/bottom solid layers, and 20-25% Gyroid infill. This combination routinely withstands 80-90% of the load of a solid 100% infill part at 40% of the cost.
