The present invention relates to a method of injection molding comprising providing an injection molding apparatus having a first mold member (18) and at least one movable mold member (20) that can move toward and away from the first mold member to close the mold, in which there is a mold cavity (33), in at least one of the first or movable mold members injecting a polymer melt into the mold cavity while it is closed, applying ultrasonic vibrations to the mold cavity by means of an ultrasonic horn (42), characterized by positioning a carrier web (34) so that, when the mold is closed, the carrier web is between the first mold member and the moving mold member, part of the web faces the mold cavity and part of it is outside of the closed mold, and injecting polymer melt into mold cavities in both the first and movable mold members between which the carrier web is positioned.
