Mold protection method for mold clamping apparatus

A mold protection method for a mold clamping apparatus, in which a predetermined mold protection zone is set in a mold closing zone, and presence of a foreign object is detected as an anomaly on the basis of a change in at least two physical quantities in the mold protection zone so as to protect a mold, the method comprising the steps of:

• moving a crosshead in a mold closing direction at a first speed until reaching a crossover point;
• moving the crosshead at a second speed less than the first speed until a preset threshold is reached, the preset threshold being a threshold for change that has been set in advance in each of the at least two physical quantities, and the closure of the mold being detected on the basis of detection of the change in each of the at least two physical quantities having reached the preset threshold;
• previously setting, as a reference position, a closed position of a movable platen at which a target mold clamping force is obtained;
• setting an end position of the mold protection zone with respect to the reference position;
• detecting, during a production operation, an actual closed position of the movable platen;
• and
• correcting the end position of the mold protection zone on the basis of a deviation between the detected position and the reference position,
• wherein the mold clamping apparatus has a toggle mechanism, and has a closed position detection mode in which closure of the mold is detected on the basis of a change in the at least two physical quantities because of closure of the mold, a position of the crosshead of the toggle mechanism is detected at the time of detection of the closure of the mold, and a closed position of the movable platen at the time of the closure of the mold is obtained from the detected position of the crosshead, wherein the at least two physical quantities include:
• an estimated torque (E) based on detection of an anomalous change in acceleration of the crosshead at a time of closure of the mold, and
• an acceleration (A) at the time of closure of the mold, the anomalous change in the acceleration (A) being detected when the change in the acceleration (A) reaches the preset threshold.

A mold protection method for a mold clamping apparatus, in which a predetermined mold protection zone is set in a mold closing zone, and presence of a foreign object is detected as an anomaly on the basis of a change in a least three physical quantities in the mold protection zone so as to protect a mold, the method comprising the steps of:

• moving a crosshead in a mold closing direction at a first speed until reaching a crossover point;
• moving the crosshead at a second speed less than the first speed until a preset threshold is reached, the preset threshold being a threshold for change that has been set in advance in each of the at least three physical quantities, and the closure of the mold being detected on the basis of detection of the change in each of the at least three physical quantities having reached the preset threshold;
• previously setting, as a reference position, a closed position of a movable platen at which a target mold clamping force is obtained;
• setting an end position of the mold protection zone with respect to the reference position;
• detecting, during a production operation, an actual closed position of the movable platen;
• and
• correcting the end position of the mold protection zone on the basis of a deviation between the detected position and the reference position,
• wherein when the mold is closed at the second speed, foreign object is detected in a foreign object detection zone, and the closure of the mold is detected in a closed point detection zone subsequent to the foreign object detection zone, wherein the at least three physical quantities include:
• an estimated torque (E) based on detection of an anomalous change in acceleration of the crosshead at a time of closure of the mold,
• an acceleration (A) of the crosshead at the time of closure of the mold, the anomalous change in the acceleration (A) being detected when the change in the acceleration (A) reaches the preset threshold, and
• at least one other physical quantity.