Guide to Annealing 3D Prints [+ Why & How]

Learn how to anneal 3D printed parts for better strength, heat resistance, and dimensional stability. Covers thermoplastics and metals, temperatures, equipment, and safety tips.

Introduction

Annealing is a heat treatment that improves the strength, stability, and heat resistance of 3D printed parts. By carefully heating and cooling your prints, you can reduce internal stress, warping, and shrinkage—making parts more durable and reliable for real-world use.

This guide covers everything you need to know to anneal your prints effectively.

What is Annealing?

Annealing is a heat treatment process that improves the mechanical and thermal properties of thermoplastic and metal 3D prints by relieving internal stresses, increasing crystallinity (in thermoplastics), and enhancing dimensional stability.

Why Anneal 3D Prints?

Annealing enhances the mechanical and thermal performance of 3D printed parts by changing the internal structure of the material. Key benefits include:

Improve Strength and Stiffness

Heat treatment promotes better polymer chain alignment, which increases tensile strength, rigidity, and durability—especially in semi-crystalline materials like Nylon, PLA, or PETG.

Increase Thermal Resistance

Annealing raises the heat deflection temperature, allowing your prints to maintain shape and function in higher-temperature environments without softening or deforming.

Reduce Internal Stress and Warping

During printing, uneven cooling can introduce internal stresses. Annealing relieves these stresses, helping parts maintain dimensional accuracy and resist cracking or warping.

Minimize Shrinkage Over Time

Annealed parts are less prone to gradual deformation or shrinkage caused by residual stress or post-use heating, making them more stable for long-term applications.How Annealing Works

Thermal Process

Heating the printed object just below the material’s melting point and holding it for a specified time, followed by gradual cooling.

Effects on Polymers

• Promotes crystal growth in semi-crystalline filaments (e.g., PLA, PETG, Nylon)

• Reduces residual stresses from printing

• Alters internal molecular alignment

Effects on Metals

• Reduces brittleness and increases ductility

• Refines grain structure

• Relieves residual stress from laser sintering or machining

Suitable Materials for Annealing

Thermoplastics

Different 3D printing materials respond differently to annealing. Some show clear improvements in strength, heat resistance, and stability—others require caution or show minimal benefit.

Metals

Summary: What to Anneal and Why

• Best for Annealing: PLA, Nylon, and Stainless Steel show clear benefits like higher strength, better heat resistance, and reduced stress.

• Use with Caution: PETG, ABS, and ASA may shrink or warp—results vary and require careful control.

• Metals: Inconel and Titanium need special furnaces but gain strength and stability.

  In short: Annealing works best with crystalline plastics and industrial metals. Know your material, control the process, and you’ll get better, stronger parts.

Equipment for Annealing

The annealing process differs depending on the material—particularly between metals and thermoplastics. While industrial parts often require specialized furnaces, many thermoplastics can be annealed at home under the right conditions.

Below is a breakdown of equipment types, their suitability, and safety notes.

Common Annealing Equipment

Safety Tips:

• Use a dedicated oven—do not reuse it for food preparation.

• Ensure the space is well-ventilated.

• Avoid heating unknown or filled filaments (carbon, glass) in indoor, poorly ventilated areas.

• Use oven thermometers, infrared thermometers, or thermal cameras to monitor temperature accurately.

Thermal Monitoring Tools

To ensure consistent and safe annealing:

• Oven Thermometer – For real-time temperature monitoring.

• Infrared Thermometer – For non-contact surface temperature readings.

• Thermal Camera (optional) – For mapping heat distribution, especially useful in industrial or research settings.

Safety Note:

When annealing thermoplastics, avoid using your food oven. Some filaments may emit fumes during heating. Use a dedicated convection oven in a well-ventilated area, and always monitor the temperature with a reliable thermometer.

Step-by-Step Annealing Process

1.  Preparation

• a.  Clean and dry the part thoroughly

• b.  Support fragile features with sand, molds, or fixtures

• c.  Measure dimensions for shrinkage tracking

2.  Preheat Oven/Furnace

• a.  Stabilize the temperature before inserting the part

3.  Place the Part

• a.  Use a tray of sand or a mold to prevent warping

4.  Annealing Phase

• a.  Maintain target temperature for specified time

• b.  Duration depends on part size and material

5.  Controlled Cool Down

a.  Let the part cool inside the oven slowly

b.  Rapid cooling may cause cracking or warping

Recommended Annealing Temperatures and Times

Thermoplastics

Metals

Notes:

• Annealing parameters can vary based on part geometry, wall thickness, and printer-induced stress.

• Always consult material datasheets or follow standards such as ASTM F2924, AMS 2759, or supplier-specific heat treatment recommendations for critical parts.

• Use vacuum or argon-controlled furnaces for alloys prone to oxidation (like titanium and copper).

Dimensional Accuracy and Shrinkage

Annealing can improve performance but may also cause parts to shrink or warp. Understanding typical shrinkage rates and how to control them is key to preserving dimensional accuracy.

Typical Shrinkage Rates (Thermoplastics)

• PLA: 2–5%

• PETG: 1–3%

• Nylon: 2–5%

Shrinkage varies based on material type, print settings, part geometry, and the annealing process itself.

How to Minimize Deformation

• Use a support mold or bed of sandHelps maintain shape during softening.

• Orient the part to reduce stressDesign and print orientation can influence how stress distributes during heating.

• Apply design compensationSlightly oversize parts in CAD to offset expected shrinkage.

• Control heating and cooling ratesGradual temperature changes reduce internal stress and deformation.

By planning ahead, you can minimize distortion and ensure your annealed parts retain their intended dimensions.

Troubleshooting and Tips

Even with careful control, issues can occur. Here’s how to address common problems:

• Warping: Use supports, molds, or sand to stabilize shape

• Uneven Annealing: Calibrate oven; avoid hot or cold spots

• Part Deformation: Reduce temperature or shorten annealing time

• Cracking or Layer Separation: Indicates rapid temperature change or poor print bonding

Advanced Techniques

For professionals or advanced hobbyists, these methods offer enhanced results:

• Annealing in Molds: Preserves complex geometry and dimensional accuracy

• Multi-Stage Annealing: Gradual temperature increases and staged holds

• Annealing with Pressure: Uses compression fixtures in industrial setups

Optimize Your Production with Unionfab

Unionfab offers professional services including annealing, stress relief, and hot isostatic pressing (HIP) to help you achieve higher-performance parts. Whether you're working with plastic or metal prints, we've got you covered.

Annealing is a powerful post-processing method that can significantly enhance the performance and reliability of 3D printed parts—both thermoplastic and metal. With the right materials, equipment, and process control, even hobbyist-grade prints can benefit from improved strength, heat resistance, and dimensional stability.

FAQs

Can all 3D printed materials be annealed?

Not all materials are suitable for annealing. Thermoplastics like PLA, PETG, Nylon, PC, and PEEK benefit from annealing. Some resins and metal powder-based materials can also be annealed but require specific procedures.

Does annealing always improve strength?

In most cases, yes. Annealing helps realign the internal structure of the material, improving strength, stiffness, and heat resistance. However, if not done correctly, it can lead to warping, deformation, or cracking.

What temperature should I anneal PLA at?

PLA is typically annealed at 70–90°C for 30–60 minutes. It’s important to heat and cool gradually to reduce the risk of warping.