Stronger Prints: Best Practices for FDM 3D Printing

Fused Deposition Modeling (FDM) is one of the most widely used 3D printing technologies in the world. Its versatility, cost-effectiveness, and ability to print in engineering-grade materials make it a favorite for prototypes, functional parts, and even low-volume production. But not every FDM print is created equal.

Parts can warp, delaminate, or fail under stress if not designed or appropriately printed. When strength matters, a more thoughtful approach is required. This guide covers what affects strength in FDM, how to create smarter, which materials to choose, and how MakerVerse supports stronger prints.

Why FDM Parts Fail

Before improving strength, it’s essential to understand where weaknesses come from. The most common causes are:

• Layer adhesion – FDM prints are anisotropic: they are stronger along filament paths than across layers. Poor bonding between layers leads to cracks or delamination.

• Warping and shrinkage – Thermoplastics contract when cooling. Larger flat parts, corners, or high-temperature polymers are especially prone to curling or distortion.

• Weak infill or walls – Thin shells or low infill density result in fragile parts that may collapse under load.

• Geometric stress points – Sharp inside corners, unsupported overhangs, or very thin features concentrate stress.

• Printer calibration issues – Incorrect extrusion settings, nozzle temperatures, or cooling speeds weaken the printed structure.

Key Factors for Stronger FDM Prints

1. Choosing the Right Material

Material selection is the foundation of print strength. Different polymers have dramatically different mechanical properties.

• Standard polymers (PLA, ABS, PETG): Good for prototypes, low-stress applications.

• Engineering polymers (Nylon, PC, ABS blends): More toughness and chemical resistance.

• High-performance polymers (PEEK, PEKK, Ultem™): Exceptional mechanical strength, high heat tolerance, used in aerospace and automotive.

👉 Learn more:

• Choose the Right FDM 3D Printing Material

• Ultem FDM 3D Printing

2. Wall Thickness and Perimeter Shells

Wall thickness has a bigger impact on strength than infill. Increasing the number of perimeter shells adds continuous extruded paths, which are much stronger than sparse infill patterns.

• Recommended minimum wall thickness: 1.2–1.5 mm (about 3 perimeter lines).

• For structural parts: Consider 2–3 mm or more, depending on load.

• Add ribs instead of just thicker walls: Reinforcement ribs improve stiffness without dramatically increasing print time.

3. Infill Density and Pattern

Infill affects weight and internal strength. While 20% infill is sufficient for a visual prototype, functional parts often require 40–80% infill.

• High infill (60–100%): Better compressive strength, ideal for load-bearing areas.

• Pattern choice matters: Grid and gyroid infills distribute stress more evenly than simple lines.

• Hybrid strategy: Use high infill only where needed (localized strength) and keep the rest lighter to save material.

4. Layer Orientation and Part Placement

FDM parts are weakest across layers. Orienting parts so the layers align with the direction of applied forces makes a huge difference.

• Align layers with load: For a beam under bending, orient so the filament runs along the length.

• Reduce supports: Supports can scar surfaces and reduce quality — orienting smartly minimizes them.

• Large flat surfaces: Place them on the print bed when possible for better adhesion and less warping.

5. Geometry Design for Strength

Geometry choices have a significant influence:

• Fillets on inside corners: Sharp corners are stress concentrators; fillets spread load smoothly.

• Avoid unsupported thin features: The minimum wall thickness should respect the nozzle size and material shrinkage.

• Use chamfers instead of overhangs: Chamfers print more cleanly and reduce stress.

• Holes and pins: Holes often print undersized; allow extra clearance or plan to machine afterwards.

👉 More guidance: The FDM Design Guide

6. Print Settings That Improve Strength

Optimizing printer settings increases part durability:

• Temperature: Higher nozzle temperatures improve layer adhesion (but avoid overheating).

• Speed: Printing slower allows better bonding.

• Layer height: Thinner layers improve interlayer adhesion and surface finish.

• Cooling: Too much cooling weakens adhesion; balance cooling with strength requirements.

7. Post-Processing for Strength

Post-processing isn’t just cosmetic — it can add strength:

• Annealing: Controlled heating of parts relieves stresses and increases crystallinity in polymers.

• Machining critical surfaces: Reaming holes or milling flat surfaces ensures proper fits and higher accuracy.

• Coatings or infiltration: Epoxy coatings or chemical smoothing can seal surfaces, reducing crack initiation points.

MakerVerse Approach to FDM

At MakerVerse, we offer industrial-grade FDM printing services to ensure your parts meet the required strength.

• FDM 3D Printing Services – An Overview of Our Process, Capabilities, and Applications.

• Achieving Color Uniformity in FDM – For when strength and consistent appearance both matter.

We guide customers through material selection, orientation, and post-processing options, ensuring parts are not just printed but engineered for function.

Practical Examples

• Aerospace bracket (Ultem FDM): Required high heat resistance and structural load. Designed with 3 mm walls and gyroid infill oriented along the load direction. Post-processed with machining.

• Automotive jig: Needed dimensional stability under repeated use. Printed in Nylon with 50% infill, reinforced with fillets and ribs.

• Consumer prototype: PLA print, low infill but thicker shells for drop-test durability.