Method for fabricating contour muntin bars from sheet material

The present invention relates to the fabrication of insulating glass units for windows, and more particularly to a system for fabricating muntin bars used in the construction of insulating glass units. Method and apparatus for making a contoured muntin bar. A supply of sheet material having a finished surface on at least one side in the form of a coiled ribbon is unwound and fed along a strip path of travel to a punch station. At the punch station a ribbon punching mechanism punches the ribbon at a precisely predetermined locations along the ribbon to form one of a plurality notch patterns that define a portion of a contoured muntin bar. Downstream along the travel path from the punch station the ribbon is fed through a forming station having a succession of forming rolls that define a succession of forming roll nips to bend the ribbon and form a generally closed cross-sectional tube. The rolls form a number of bending stages to produce a muntin bar tube having a contoured shape with raised sides to provide an attractive appearance to a muntin grid.