Abstract: A method of press forming plastic material by a press having upper and lower moulds, in which melt plastic material is extruded from an extruder and is supplied to a metering chamber. The metering chamber supplies a metered amount of material into a movable arm which moves over the mould surface area of the lower mould and injects the material from an injection port of the arm, while the arm is moving. By suitably controlling the movement of the arm and material supply from the metering chamber, a desired charge pattern formed by a parapet shaped injected material can be formed. Automatic programming by a microprocessing unit is also easy.