How strong are 3D printed parts compared to injection-moulded?

FDM printed parts typically achieve 50-80% of the strength of injection-moulded equivalents in XY, but only 20-50% in the Z direction (between layers). Higher infill, more walls, and optimal orientation can close this gap significantly.

Does infill percentage affect strength linearly?

No. Going from 10% to 20% infill roughly doubles internal strength, but the walls contribute most of the structural strength. Beyond 40% infill, strength gains diminish. More walls are often more effective than more infill.

Why is Z-axis strength so much lower?

The Z-axis (layer direction) relies on layer adhesion rather than continuous filament strands. Layer adhesion is typically 20-60% of the filament tensile strength. Increasing print temperature and reducing cooling can improve inter-layer bonding.

Which material is strongest for 3D printing?

Nylon Carbon Fibre (PA-CF) offers the highest strength-to-weight ratio among common FDM materials (~85 MPa tensile). Polycarbonate (PC) is also very strong. For easy-to-print strength, PLA has surprisingly high tensile strength at 50 MPa.

3DPrintCalcs

Material Strength Calculator — Tensile & Compressive Strength

Estimate tensile and compressive strength based on material and print orientation.

MaterialFilament type — sets the base tensile/compressive figures used in the estimate

Load OrientationDirection the load acts relative to the print layers — Z (between layers) is weakest

Infill

Infill density of the interior — only the solid wall shell plus this fraction of the core carries load

Wall Count

Number of perimeter/wall lines — walls carry most of the load (3-4 is typical for structural parts)

Section Width

Width of the part's cross-section under load (mm)

Section Height

Height/depth of the part's cross-section under load (mm)

Line Width

Extrusion line width, typically nozzle dia x 1.0-1.2 (e.g. 0.45 mm on a 0.4 mm nozzle)

How We Calculate This

Strength Estimation

Effective area = Wall area + (Infill area x Infill%)
Solid material fraction = Effective area / Total cross-section area
Tensile strength = Material tensile x Solid material fraction x Orientation factor
Break force = Tensile strength x Total area

The calculation accounts for the hollow interior of printed parts by computing the solid material fraction of the cross-section (the proportion that is actually plastic, not air). This is a geometric area ratio, not the filament's mass density. The orientation factor reduces strength when loads act across layer lines.

Frequently Asked Questions

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Last updated: February 2026

All calculations are estimates. Always verify settings with test prints before committing to final prints.