Methods for preventing oxygen inhibition of a light-initiated polymerization reaction in a 3D printing system using uniform planar surfaces

A method of preventing oxygen inhibition of a light-initiated polymerization reaction at ambient conditions, said method comprising:

• depositing a layer of ultraviolet (UV) light-curable material on a print surface of an object under fabrication;
• purging oxygen from a UV curing space, within which the object under fabrication with the layer of UV light-curable material thereon is located, to facilitate, within the UV curing space, UV curing of the UV light-curable material at times when a first light source emits UV light onto the layer of UV light-curable material, wherein purging oxygen from the UV curing space comprises after depositing the layer of UV light-curable material, raising the print surface of the object under fabrication with the layer of UV light-curable material thereon towards a UV-transparent planarizing surface and evaluating reflective properties of the UV-transparent planarizing surface with a camera arranged for said evaluating while the layer of UV light-curable material has not yet been cured by the first light source so as to determine whether contact has been achieved between the layer of UV light-curable material on the print surface of the object under fabrication and the UV-transparent planarizing surface;
• detecting a height of the object under fabrication by a height sensor comprising a second light source for emitting a beam of light and a detector for detecting the beam of light, the second light source and detector arranged on opposite sides of the object under fabrication and adjacent to the UV-transparent surface such that detection of the beam of light by the detector indicates that the object under fabrication has not yet been raised to an appropriate height for UV curing of the UV light-curable material to begin, and failure to detect the beam of light by the detector indicates that the object under fabrication has been raised to the appropriate height for the UV curing of the UV-light curable material to begin;
• and
• after determining that the contact has been achieved between the layer of UV light-curable material on the print surface of the object under fabrication and the UV-transparent planarizing surface by both the evaluation of the reflective properties of the UV-transparent planarizing surface and the detection of the height of the object under fabrication by the height sensor, activating the first light source to cure at least a portion of the layer of UV light-curable material disposed on the print surface of the object under fabrication.