Patent ID: 7504056

Claim:
A method of controlling an extrusion molding system which comprises a die having an opening including a first part with an unvariable shape and a second part with a variable shape, an extruder which feeds a material to the die, a first gear pump arranged between the die and the extruder, a branch part arranged upstream of the first and second parts of the opening of the die which divides the die into a first passage connected with the first part of the opening for supplying the material and a second passage connected with the second part of the opening for supplying the material, and a valve mechanism arranged in the second passage, wherein the valve mechanism adjusts a flow rate of the second passage, and being arranged to fully close the second passage when the second part is fully closed, the method comprising: conducting a first sequence control to change the shape of the second part of the opening; conducting a second sequence control to change a rotation speed of the first gear pump in synchronism with the change in the shape of the second part of the opening; and conducting a third sequence control to open and close the valve mechanism within a width of the second passage to control an amount of the material to be supplied to the first and second passages such that the amount the valve mechanism is open in the second passage is directly proportional to the cross section of the second part of the opening achieved in said conducting a first sequence control.