Calculation model and mesh division for parison shape prediction: (a) entire extruded parison; (b) cylindrical calculation model for calculating the parison molding process; (b-1) state of the calculation model before extrusion; (b-2) constraints set in the model before extrusion, while in the model after extrusion, sequential calculations are performed with constraints released at each Δt; (b-3) state of the calculation model after extrusion; (c) mesh division of the calculation model extruded during unit time Δt; and (d) enlarged figure. Here, r is thickness direction and z is extrusion direction.