Thermal curing methods and systems for forming contact lenses

An oven for curing contact-lens precursor materials in molds to form contact lenses, wherein the oven comprises:

• a source of an inert gas operable to provide an inert atmosphere in the oven during the curing;
• a plurality of zones separated from one another by at least a wall;
• a mold advancement system for moving the molds between the plurality of zones;
• a plurality of vertically stacked transport units for supporting the molds, each transport unit including a baffle portion arranged to form at least part of a zone wall so that when the vertically stacked transport units are in one of the zones, the zone wall acts to restrict heat flow into an adjacent zone, and the baffle portion of one of the transport units is arranged to co-operate with a corresponding baffle portion of another transport unit to form at least part of a zone wall when the transport units are stacked vertically;
• the oven is operable to maintain simultaneously a first zone of the plurality of zones at a first temperature and a second zone of the plurality of zones at a second, different, temperature;
• and
• the plurality of zones are in gas communication with each other so that the inert atmosphere is a single inert atmosphere extending throughout the plurality of zones.