Why model settings control your print cost and quality
Most 3D printing beginners focus on material choice (PLA vs. PETG) and print speed as the main variables. But two model settings often have a larger impact on both material cost and final part quality: scale and infill percentage. Understanding how these interact lets you optimize for your specific use case — whether that's minimizing material use, maximizing strength, or matching a specific size requirement.
Scale: the cubic relationship that surprises everyone
When you scale a 3D model in your slicer, you're changing all three dimensions simultaneously. This causes volume — and therefore material use — to change by the cube of the linear scale factor, not linearly.
Practical implications:
- Scaling from 100% to 110% (a modest 10% increase) increases volume by 1.10³ = 1.331× — 33% more material.
- Scaling from 100% to 150% increases volume by 1.50³ = 3.375× — more than triple the material.
- Scaling from 100% to 200% increases volume by 2.00³ = 8× — 800% more material.
- Scaling down from 100% to 75% reduces volume by 0.75³ = 0.422× — less than half the material.
Use the 3D Model Scale Calculator before scaling any model to understand the material and time implications before you commit to the print.
Infill: balancing strength, weight and cost
Infill is the internal structure that fills the space between the outer walls of a 3D print. It serves three purposes: supporting top surface layers, providing compressive strength, and adding stiffness to the overall structure.
The key insight: infill percentage affects infill weight linearly, but infill weight is only a fraction of total print weight. Outer walls and top/bottom layers (which scale with surface area, not volume) often dominate material usage, especially for small prints. For a small, thin-walled object, infill might represent only 20–30% of total material weight even at 25% infill — so doubling infill from 15% to 30% might only increase total print weight by 5–10%.
For a large, mostly-hollow object, infill represents a much larger fraction of total material, and changing infill percentage has a more proportional impact. The Infill Weight Calculator helps you understand the infill component specifically.
Infill vs. wall count: which gives better strength per gram?
This is one of the most important decisions in FDM printing, and the answer often surprises beginners:
For bending resistance and tensile strength: Adding perimeters (wall count) is almost always more material-efficient than increasing infill. Outer walls carry bending loads; infill transfers loads between walls but contributes less to bending stiffness. Going from 2 to 4 perimeter walls on a bracket often provides better load resistance than going from 20% to 60% infill, at lower total material cost.
For compressive strength: Infill matters more for vertical compression. A part being squished straight down gets significant support from the infill, particularly with grid or honeycomb patterns.
For impact resistance: Increasing wall count and using tougher materials (PETG, ABS, TPU) is more effective than increasing infill. Infill pattern matters here too — gyroid and cubic patterns absorb impact better than rectilinear because they're isotropic.
Practical starting points: for general functional parts, 3–4 perimeter walls at 20–25% gyroid infill provides better all-around performance than 2 walls at 50% rectilinear infill, while using similar material amounts.
Infill patterns explained
Slicers offer many infill patterns. Here's what matters for real decisions:
Grid / Rectilinear / Lines: Simple, fast, aligned with print axes. Strong in vertical compression, weak in horizontal or diagonal directions. Best for parts under purely vertical loads. Lines/zig-zag are the fastest and lightest option for decorative parts where infill only supports surfaces.
Gyroid: Complex curved pattern that creates equal strength in all directions (isotropic). Excellent for functional parts that see loads from multiple directions — joints, brackets, connectors. Slightly heavier than grid at the same percentage due to the pattern's geometry. Prints slower than grid. Many experienced makers use gyroid as their default for functional parts.
Honeycomb / Cubic: Strong under compressive load, good isotropy. The 3D cubic variant distributes loads well in all three axes. Good for impact-resistant applications.
Lightning: Extremely lightweight — generates only the minimal structure needed to support top surfaces. Excellent for display models, figurines and any print where infill is purely structural filler. No strength benefits; purely for surface support at minimal material cost.
Adaptive Cubic / Adaptive: Increases infill density near surfaces and walls, decreases toward the center. Smart balance of strength and weight for structural parts. Available in OrcaSlicer, Bambu Studio and newer versions of Cura.
Practical settings guide by use case
Decorative objects, figurines, cosplay props:
Infill: 10–15% (gyroid or lightning for best surface quality with minimal material)
Walls: 2–3 perimeters
Top/bottom layers: 4–5
Material: PLA (easiest, lightest, best detail)
General household items (organizers, holders, hooks):
Infill: 15–25% (gyroid or grid)
Walls: 3–4 perimeters
Material: PLA+ or PETG for better durability
Light mechanical parts (brackets, mounts, clips):
Infill: 25–40% (gyroid or cubic)
Walls: 4–5 perimeters
Material: PETG for flexibility and impact resistance, or PLA+ for stiffer applications
Load-bearing structural parts:
Infill: 40–60% (gyroid or cubic)
Walls: 5–6 perimeters
Material: PETG, ABS, ASA, or engineering materials like PA-CF for maximum performance
Maximum strength (rarely needed):
Infill: 80–100%
Walls: 6+ perimeters
Material: Nylon, PC, PA-CF, or specialty engineering materials
Note: At this extreme, you're almost entirely into engineering filament territory, and the prints are heavy and slow. Consider whether the application is better served by a different manufacturing method (machined aluminum, for instance).
Scale and infill: how they interact for cost optimization
Here's a practical decision framework when you need to reduce material cost for a print:
- Can you scale down? Even a 10% linear reduction (100% → 90%) saves 27% of material (0.9³ = 0.729). If the object's function allows a slightly smaller size, this is the most efficient cost reduction lever.
- Can you reduce infill? If the model is non-structural, dropping from 20% to 10% infill reduces infill weight by 50%. Impact on total weight depends on the wall-to-infill ratio for that geometry — typically a 5–20% total weight reduction.
- Can you reduce wall count? Going from 4 to 3 perimeters reduces wall material proportionally. Only do this for decorative, non-structural items.
- Can you hollow the model? Manual hollowing in CAD (adding drain holes) can eliminate the interior entirely, saving 50–80% of material for solid-looking parts. This is standard practice in resin printing and useful for large FDM decorative pieces.