What is the impact of discoloration?
First and foremost, please note that discoloration is a purely optical issue, it has no impact on the functionality of the part. Discoloration has no negative influence on the density, the mechanical properties, or the dimensional accuracy.
If the visual appearance plays a role for your part, please consider ordering a paint or color-dye finish to solve optical aspects.
How is discoloration caused?
Discoloration in PA12 is caused by minor changes (=degradation) of the polymer structure of a very small number of molecules (in the range of parts per million, ppm). These few molecules will assume a darker color leading to the optical effect of discoloration of the whole polyamide part. In most cases the part will be a shade of light yellow.
Discoloration can occur under the influence of UV radiation and aging over time, or it can be present directly after the building of a part. In the second case the polymer structure changes are caused by the influence of thermo-oxidative stress seeing that the Laser Sintering process uses high temperatures over longer periods of time.