Abstract: A tray forming machine comprising an infeed station for accepting a blank of corrugated plastic, and a transfer mechanism which automatically conveys the blank along a plane into a blank receiving station between a tray forming ram and a forming tool frame. The tray forming ram moves downward along a vertical path carrying the blank through the forming tool frame, during which the blank is folded into a generally upright tray configuration by a series of vertically displaced side and end forming bars and brackets. The tray forming ram and blank emerge from the forming tool frame and are received in a clamping and welding assembly which holds the blank in position while it is secured by sonic welds into the upright tray. The clamping assembly releases while the tray forming ram returns to its raised position, and the tray is stripped off the tray forming ram by the bottom of the forming brackets.