Method of predicting gravity-free shape of glass sheet and method of managing quality of glass sheet based on gravity-free shape

A method of predicting a gravity-free shape of a glass sheet, comprising:

• determining, using a shape-measuring part that operates a plurality of sensors to measure a property of the glass sheet at a plurality of locations, an initial shape of the glass sheet during a process of forming the glass sheet based on the property measured at the plurality of locations, the initial shape of the glass sheet comprising a one-dimensional shape which the glass sheet has during the process of forming the glass sheet and prior to application of an external force as part of a flattening process;
• applying an external force to the glass sheet having the initial shape as part of the flattening process to form a flattened glass sheet;
• during application of the external force to the glass sheet as part of the flattening process, measuring stress values applied to the flattened glass sheet at the plurality of locations as a result of the application of the external force;
• generating a glass sheet model having the initial shape and to which the stress values are applied;
• predicting a shape which the glass sheet model will have after removal of the stress values, as a gravity-free shape of the glass sheet;
• and
• storing the gravity-free shape of the glass sheet in a database with defect information associated with the gravity-free shape to stop a supply subsequently-produced glass sheets comprising the gravity-free shape to customers based on the defect information.