Annealing in 3D Printing: What It Is and When to Use It – 2025 Guide

The term annealing refers to a heat treatment used to modify the physical and mechanical properties of a material.
From metals to polymers—and even 3D-printed parts—annealing is a key step for improving strength, ductility, and dimensional stability.

In this guide, you’ll learn what annealing is, how the process works, and what benefits it provides for industrial and additive manufacturing applications.

What is Annealing for 3D-Printed Polymers

Annealing is a controlled thermal process consisting of three stages:

• Heating below the melting point

• Soaking to allow stress relaxation and, in semi-crystalline materials, increased crystallinity.

• Controlled cooling, slow and uniform, to prevent new stress formation.

Expected outcomes:

• Reduced deformation and warping

• Increased stiffness and fatigue resistance

• Long-term dimensional stability

• Possible increase in heat resistance for semi-crystalline polymers

When to choose annealing

• Functional components exposed to repeated loads or heat
• Mating parts or tight-tolerance assemblies that must remain stable
• High-performance or semi-crystalline polymers
• Pre-series or small production runs, to achieve “end-use” material behaviour

Note: Annealing does not replace good design (wall thicknesses, reinforcements, print orientation or strategy); it complements it.

How the annealing process works

While the exact procedure varies depending on the material, the underlying principle remains the same.

1. Heating

The material is brought to a specific temperature—below its melting point—allowing atomic mobility without melting the structure.
Examples:

• Steels: 500–900 °C

• Aluminium: 300–500 °C

• Polymers (3D printing): 70–150 °C

2. Soaking

The temperature is maintained long enough to allow atomic diffusion and stress redistribution.
Duration depends on the material and its thickness.

3. Controlled cooling

Cooling must be slow and uniform to avoid introducing new internal stresses. In some cases, this takes place in a closed furnace or controlled atmosphere (air, inert gas, oil).

Types of annealing

Different annealing methods serve specific purposes:

• Full annealing – restores metals to their original condition after heavy deformation.

• Stress-relief annealing – removes residual stresses from welding or machining.

• Isothermal annealing – involves gradual cooling at constant temperature to achieve a uniform microstructure.

• Process annealing – improves ductility before further forming operations.

• Polymer annealing (plastic annealing) – increases crystallinity and dimensional stability in 3D-printed materials.

Main Advantages of Annealing

Annealing treatment offers several benefits for both metals and polymers:

Limitations and Precautions

• Possible micro dimensional variations – test samples recommended for critical tolerances

• Aesthetic changes in some polymers

• Longer processing times compared to “as-printed” parts

• Risk of deformation without proper fixtures – controlled temperature profiles advised

• Material-technology compatibility – not all polymers/resins benefit equally

Annealing in 3D printing

In recent years, annealing has become a crucial step in 3D printing to enhance the performance of components made from thermoplastic materials.

During printing, layers are deposited and cooled unevenly, generating internal stresses and microvoids.
Annealing helps relieve these stresses and optimise mechanical properties.

How 3D Printing Annealing Works

1. The printed part is heated close to its glass transition temperature (Tg).

2. Temperature is held steady for a set period (from 30 minutes to several hours).

3. The part is then cooled slowly in the switched-off furnace or a controlled environment.

Focus on high-Performance materials

PEEK and PEI/ULTEM (FDM)

• ↑ Crystallinity and microstructural stability
• ↑ Mechanical and fatigue strength
• ↓ Deformation in service

Typical materials and Temperature Ranges

At Weerg we use certified annealing profiles for each material and technology.

Annealing FAQ

Does annealing alter the dimensions of a 3D-printed part?
Minor variations may occur. At Weerg, we compensate through specific profiles and fixtures; for critical dimensions, we recommend producing a sample before full production.

How long does an annealing cycle take?
It depends on material, technology, and thickness – typically from around 30 minutes to several hours, including heating and cooling phases.

Is annealing compatible with other finishes?
Yes. It’s generally performed before aesthetic finishes (such as sandblasting or painting) to avoid altering their appearance.

Conclusion

Annealing is a key process for enhancing the quality of both metallic and plastic materials.
For high-performance materials such as PEEK and ULTEM, it can make a decisive difference in achieving consistent, industrial-grade results.

Annealed PEEK, in particular, stands out as one of the most advanced and reliable materials available—ideal for those who need precision, strength, and long-term stability.

Order annealed PEEK directly from our online quoting tool