PLA (Polylactic acid):

It is the most commonly used material in desktop 3D printing due to its easiness to print and low ecological footprint. It is a renewable thermoplastic used by traditional manufacturing methods in fabricating food packaging containers and biodegradable implants. Within the 3D printing community it is used to make 3D models for presentation purposes due to its beautiful visual appearance. PLA filament comes in both translucent and solid colors, all having a nice luster. It is a brittle material that will break or chip under low to average impact (dropping a part onto a hard surface can chip it), unlike engineering thermoplastics. Does not withstand temperatures higher than 50 C (it will heat deform in a hot car for example). While there are cases where it was used for technical applications, it is normally to be avoided for functional parts unless when used at room temperature and low stress applications.

Newer variants of this material with slightly increased glass transition temperature and/or increased flexibility are providing an eco-friendly solution for a larger range of properties of the 3D printed parts if operation close to room temperature is desired.

PLA 3D printing:

PLA has a low glass transition temperature of around 50 °C to 60 °C, therefore it can be extruded at temperatures starting at around 180°C to 200 °C. It is possible to extrude PLA using systems that incorporate plastic parts as thermal shields for the hot-end. Historically, DYI open source community favored those kind of designs due to their simplicity and easiness to implement in a hobby 3D printer. 

Another consequence of PLA's low transition temperature is that thermal stress in 3D printed parts is practically never an issue when 3D printing at room temperature. PLA is also a very sticky material with a very fluid, sirup like viscosity at extruding temperature, so adhesion on the printed surfaces is good on many surfaces, even at room temperature. 

All these properties make PLA a very easy material to 3D print, without the need of a heated bed or enclosure, and 3D printable on DIY extruder systems.

Extruder systems with an all metal hot-end construction can print PLA as long as they have proper cooling. 3FXtrud Uno and 3FXtrud Duo have all metal hot ends that have been extensively tested to print PLA. 

3D printing requirements:

An extruder with a hot-end capable of withstanding 220 °C continuously. A heated bed is not required but it helps if it is to be printed on a glass or metal surface. An enclosed printer is not needed since PLA does not warp and softens at around 50 - 60 °C.

PLA is available in 1.75 mm and 3 mm.

Pyra 2 uses 3 mm filament, while the newer 3FXtrud 20 Uno, 3FXtrud 25 Uno, 3FXtrud 25 Duo, and 3FXtrud 30 Duo use 1.75 mm.