Sterile environment for additive manufacturing

In sterile, additive manufacturing wherein one lamella is successively built upon an underlying lamella until an object is completed, a sterile manufacturing environment is provided. A major chamber large enough to accommodate the manufactured object has sterile accordion pleated sidewalls and a sterile top closed with flap valves. A minor chamber for supporting the nozzles positioned above the major chamber has similar valves in corresponding positions. Nozzles for material deposition penetrate the pair of valves to block air and particles from entry into the major chamber where the nozzles make layer by layer deposition of the object using XY areawise nozzle motion relative to the object as well as Z nozzle vertical motion with the major chamber expanding as the object is formed.