| 摘要 |
<p>According to the invention, a preliminary extrusion is performed to find an optimum back pressure which can provide a predetermined sectional size for respective portions of a movement pattern DA of a movable die, which pattern is determined by a shape of a product. It is assumed that the movable die is positioned at a position DA1 corresponding to a side portion of a product and a value of a back pressure BP, at which a molded product has a predetermined sectional size while rotations of a screw are variously changed during molding of a molding material, is made an optimum back pressure BPO. An optimum back pressure for an upper portion of a product is determined in a like manner to decide a pattern of the optimum back pressure BPO. Taking into account time lag, a timing, at which an initial set pattern R1 for rotations of the screw is changed, is set a period of time T11 to T14 ahead of a timing, at which the pattern DA is changed. In a regular extrusion, an actual take-up speed is measured, and when the measured speed is different from that at the time of the preliminary extrusion, the movement pattern DA of the movable die is corrected. When the measured back pressure BP is deviated from the pattern of the optimum back pressure BPO after several cycles of extrusion molding have been executed, the pattern R1 for rotations of the screw is corrected.</p> |
