Abstract: An edge forming tool is pressed into a thermoplastic sheet which is supported on an anvil or counter tool. The edge forming tool is maintained at a temperature below the melting temperature of the thermoplastic sheet and a high frequency electric field is established between the edge forming tool and the counter tool. The high frequency electric field softens the thermoplastic sheet which is deformed by the edge forming tool. Thereafter, the softened and deformed portions of the thermoplastic sheet are allowed to cool and re-harden before the sheet is folded to form a bend therein.