Choosing a 3D printer is a personal decision. From mom-and-pop crowd-sourced startups to massive, corporate giants, every printer has its own advantages and disadvantages. Machines intended for printing predominantly with acrylonitrile butadiene styrene plastic have heated build plates, while ones with ambient build plates are intended mainly for polylactic acid or polylactide (PLA). While being extruded, PLA has been described as smelling slightly sweet – like toasted corn or waffles with maple syrup. The filament mechanism typically consists of a filament spool holder and a guide tube that directs the plastic into the extruder. With long-term exposure, thermoplastics can absorb moisture from the air, which can cause the filament to swell and vary its diameter. A DeltaBot positioning system uses a stationary build plate and a spider-like arm assembly that moves in all three axes. Leveling, or tramming, is usually achieved by adjusting several points on the bottom of the build plate.