Compression molding method and mold clamping apparatus

A method of compression molding that is effected by using a mold including a stationary mold half and a movable mold half that cooperate to define therebetween a mold cavity, and by executing a mold clamping operation to clamp together said stationary mold half and said movable mold half that are parted by a predetermined amount with a molding compound such as plasticized synthetic resin material present in said mold cavity with a mold clamping force exerted across said stationary mold half and said movable mold half by means of a plurality of mold clamping mechanisms, said method comprising the steps of:

• sensing said mold clamping forces in said plurality of mold clamping mechanisms to obtain sensed mold clamping forces;
• calculating an average value of said sensed mold clamping forces;
• obtaining a first control signal on the basis of deviation between a preset target mold clamping force for said mold clamping mechanisms and said average value of said sensed mold clamping forces;
• sensing positions of movable members of said plurality of mold clamping mechanisms to obtain sensed positions of said movable members;
• calculating an average value of said sensed positions of said movable members of said plurality of mold clamping mechanisms;
• setting said average value of said sensed positions of said movable members as a successive target position;
• obtaining a second control signal on the basis of deviation between each of said sensed positions of said movable members of said plurality of mold clamping mechanisms and said successive target position;
• obtaining a clamping control signal for each of said plurality of mold clamping mechanisms by adding said first control signal and said second control signal;
• and executing the mold clamping operation using the clamping control signal.