How to Anneal PLA for Heat Resistance: Ingeo 850 & 870 Guide

NatureWorks Ingeo PLA filaments are engineered for applications where standard PLA isn't enough. Through a simple post-print annealing process, both Ingeo 850 and 870 reach a heat deflection temperature of 85°C — on par with ABS and ASA — while remaining as easy to print as standard PLA. Eolas Prints manufactures both variants in-house in Cantabria, Spain.

Ingeo 850 vs Ingeo 870: What's the Difference?

In practice, both variants perform similarly for most applications. Choose 870 when maximum impact resistance is the primary requirement.

Recommended Print Settings

Slightly slower print speeds (40–80 mm/s) improve inter-layer adhesion, which matters because annealing applies thermal stress to the part. Better layer bonding before annealing means the part emerges from the oven stronger and better-defined.

The Annealing Process Step by Step

Annealing is a controlled crystallisation process that permanently raises the heat deflection temperature and increases impact resilience. It takes 15–20 minutes and requires only a standard kitchen oven.

1. Print your part as normal. Allow it to cool fully on the bed before removing.
2. Prepare an annealing surface. Place the print on a flat piece of borosilicate glass, a ceramic tile, or a flat metal tray. This prevents the part from warping during crystallisation. For complex parts with internal overhangs, fill voids with sand or fine salt to provide internal support during annealing.
3. Preheat the oven to 120°C. Allow the oven to reach temperature fully before placing the part inside — sudden heat exposure from a cold start can cause warping.
4. Place the part in the oven for 15–20 minutes. Thicker parts (wall thickness above 3mm) may benefit from 20–25 minutes.
5. Cool slowly inside the oven. Turn the oven off and leave the door closed. Allow the part to cool to room temperature inside the oven before removing. Rapid cooling after annealing can introduce new stresses and undo some of the crystallisation benefit.
6. Check dimensions. Annealing causes approximately 1–2% shrinkage in all directions. For precision parts, design with this allowance built in. A part designed at 50mm will typically anneal to approximately 49–49.5mm.

Dimensional Allowance for Annealing

The 1–2% shrinkage during annealing is predictable and consistent. For functional parts with tight tolerances (holes, threads, snap fits, interference fits), design 1–2% oversized in all critical dimensions and anneal before measuring final dimensions. After annealing, the part is dimensionally stable and can be post-processed (drilled, tapped, sanded) to final dimensions.

Flat parts anneal with the least distortion when supported on a flat surface. Tall, thin parts are most vulnerable to leaning during annealing — support them against a vertical surface or print them at a slightly thicker wall count (4–5 perimeters rather than 3) for annealing stability.

Colour Behaviour During Annealing

Most colours anneal without visible surface change. Darker colours (especially black and dark grey) may show a very slight surface dulling after annealing as the crystalline structure changes the light scattering properties slightly. This does not affect mechanical performance. Lighter colours (white, natural, pastels) typically show no visible change.

Recommended Applications

• Functional prototypes requiring heat resistance — parts near car interiors, electrical enclosures, or kitchen appliances
• End-use parts exposed to elevated temperatures
• Mechanical components and fixtures requiring impact toughness
• Food-contact safe parts requiring sterilisation by hot water (up to 80°C)
• Consumer products requiring both durability and precision
• Replacement for ABS in applications where enclosure-free printing is preferred

Storage and Moisture

Store Ingeo PLA in sealed containers with silica gel desiccant. Like all PLA variants, Ingeo absorbs atmospheric moisture over time. Dry at 45–50°C for 4–6 hours if the filament has been stored open in a humid environment. Printing with moisture-affected Ingeo PLA will cause brittleness and stringing that annealing cannot correct.

Shop the Range

PLA Ingeo 850 | PLA Ingeo 870 — manufactured in Spain with ISO 9001 and ISO 14001 certifications, food contact safe, REACH compliant.

For standard PLA printing, see our PLA printing guide.