4. Improving thermal properties of printed parts by annealing

In this article:

Introduction
How to anneal parts printed with LehVoss 9825 NT

Introduction

Annealing is a process where the part is kept at elevated temperature for a certain period of time (to be specific between the glass temperature and crystallization temperature). Annealing results in changes in the molecular structure of the polymer, with a higher percentage of crystallization as a result.

At higher crystallization, the thermal and mechanical properties of parts are typically improved. Annealing of LV 9825 NT PAHT parts produce an increase in HDT A from 60 C to 80C and a +20% increase in young modulus and Tensile strength.

However, annealing can generate distortions in the part and changes in thin walled features. For this reason, thin walled parts needs to be performed in sand bath in a dehumidier oven or vacuum oven for a maximum of 6h at 110 C.

Also, annealing may result in lower dimensional accuracy, as the part is deforming during the annealing process. Therefore, this is only usable for situations where thermal resistance is more important than dimensional accuracy.

How to anneal parts printed with LehVoss 9825 NT

Place the part(s) in a specialized drying / annealing oven that supports exact temperature regulation as well as slow temperature increase / decrease rates. Recognized products are the products from Memmert and Binder.

The annealing procedure is to heat the part slowly up to 100 °C and leave it on the plateau for 1 hour per mm thickness or size of the part. Use very gentle ramps for heating and cooling down to maximize the effectiveness of the treatment (max 60 degrees C / hour for heating, max 20 degrees C / hour for cooling).

Thin walled parts needs to be performed in sand bath in a dehumidier oven or vacuum oven for a maximum of 6h at 110 C.

 

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