Rigour (BrE) or rigor (AmE) (see spelling differences) describes a condition of stiffness or strictness. Rigour frequently refers to a process of adhering absolutely to certain constraints, or the practice of maintaining strict consistency with certain predefined parameters.
PLA stands for polylactic acid and is a resin made from corn starch. PLA is used to make clear compostable containers and PLA lining is used in cups and containers as an impermeable liner. PLA is biodegradable, and fully compostable. It uses 65 percent less energy to produce than conventional oil-based plastics and generates 68 percent fewer greenhouse gasses and contains no toxins.
It is one of the two most common filaments, along with ABS, purchased for use in 3D printers in many western countries. PLA is harder than ABS, melts at a lower temperature (around 180Â°C to 220Â°C), and has a glass transition temperature between 60-65 Â°C, so is potentially a very useful material. It does exhibit higher friction than ABS however which can make it difficult to extrude and more susceptible to extruder jams.