Methods and apparatuses for compensating for forming body dimensional variations

A method for forming a glass ribbon, comprising:

• directing molten glass into a trough of a forming body, the trough defined by an inlet end, a distal end, a first weir and a second weir opposite and spaced apart from the first weir, and a base extending between the first weir and the second weir along a length of the forming body, the forming body enclosed within an enclosure with a top panel, wherein the first weir and the second weir extend from the inlet end to the distal end with an incline relative to horizontal, and the top panel is positioned above and extends substantially parallel to and across top surfaces of the first weir and the second weir along the length of the forming body;
• flowing the molten glass over the first weir and the second weir and down along a first forming surface and a second forming surface extending from the first weir and the second weir, respectively, the first forming surface and the second forming surface converging at a root and the molten glass flowing down along the first forming surface and the second forming surface converging at the root and forming the glass ribbon;
• locally heating or cooling the molten glass in the trough with a plurality of thermal elements positioned above the forming body and suspended from a support plate, the support plate positioned above and extending substantially parallel to the top panel of the enclosure along the length of the forming body;
• wherein the locally heating or cooling the molten glass in the trough manipulates temperature and viscosity of the molten glass along the length of the trough.