Methods and systems are provided for making an ophthalmic lens. The present methods and systems are effecting in coupling two mold sections together at two or more discrete regions. Embodiments of the methods and systems form a bore that extends completely through one of the mold sections and only partially through the other mold section. During formation of the bore, the mold material in proximity to the bore being foamed becomes molten and diffuses from the bore. A portion of the molten mold material is provided at a contact point between the two mold sections and when the molten material cools, the material foams a spot weld between the mold sections. By foaming multiple hollow spot welds in a mold assembly, the two mold sections can be securely coupled to each other during the manufacture of an ophthalmic lens, such as a silicone hydrogel contact lens.