Quality control method and quality control apparatus for glass gob in the formation of a glass product

A quality control method for a glass gob in the formation of a glass product, comprising:

• a glass gob production step for producing a glass gob in which a feeder plunger is advanced through a feeder tube toward an orifice at a bottom portion of a container in a manner that said feeder tube is pressed in molten glass held in the container and facing said orifice, the molten glass is pushed out through said orifice to form a column-like glass body, and the column-like glass body is cut into glass gob by shear blades so that the glass gob falls with the weight thereof through a drop guide;
• a glass gob delivery step for receiving the fallen glass gob in a scoop funnel and for delivering the glass gob toward a predetermined position;
• and
• a molding step for forming a glass product in which said delivered glass gob is introduced into a mold and formed into a predetermined shape;
• wherein the quality control method further comprises:
• a three-dimensional data producing step for generating three-dimensional coordinates data of the entire surface of the glass gob by observing the glass gob, which is in a falling position between said glass gob production step and said glass gob delivery step, through a plurality of optical observing means spaced apart from each other;
• a measurement data producing step for generating, based on said three-dimensional coordinates data, measurement data relating to at least one of a volume, a weight, a surface shape, a length, a thickness, an angle in a falling direction, and a cut surface shape of the glass gob;
• a defect detecting step for detecting the presence or absence of a defect in the quality of the glass gob by comparing the measurement data with quality standard data being a selected plurality of a volume, a weight, a surface shape, a length, a thickness, an angle in a falling direction, and a cut surface shape of a normal glass gob so that quality defect data is provided when said detected defect in the quality of the glass gob is determined outside a permissible range;
• a cause evaluating step for assessing a type of the quality defect detected in said defect detecting step and identifying causal relationships between said type of the quality defect and all operational factors of the gob feeder as the cause of said type of the quality defect including a glass temperature in the container, a level of the molten glass, a pressing depth of the feeder tube in the molten glass, a height of the feeder plunger, advance and retraction speeds and/or strokes of the feeder plunger, an operation timing of the shear blades, a tension of the shear blades, an overlapping amount of the shear blades, a temperature of the shear blades and a position of the drop guide, by checking said quality defect data with reference to cause criterion data which contains information of causal relationships between types of the quality defects and the operational factors;
• an operational factor ranking determining step for determining the priority rank of the operational factors to be controlled for fault correction, by checking evaluated data including a plurality of the operational factors specified in said cause evaluating step with reference to priority ranking data of the operational factors that are prioritized in the rank from a high probability to a low probability depending on the type of the quality defect occurred;
• and
• a control driving step for automatically correcting the operational factors in accordance with the priority rank determined in said operational factor ranking determining step;
• wherein said cause evaluating step comprises checking the quality defect data obtained through said defect detecting step by comparing the defect data with cause criterion data that identifies the causal relationship between the type of the quality defect of the glass gob and the operational factor as the cause of the quality defect;
• and
• wherein said control driving step performs a control executing routine in which the operational factors are successively controlled for adjustment in accordance with the order of priority until the measurement data of the successively produced glass gobs are restored back to within the permissible range of the quality standard data;
• and
• wherein the method further comprises an updating step for storing a plurality of or at least one of the results including the result of said defect detecting step, the result of said cause evaluating step, and the result of said control driving step is stored to be used as experienced quality control record, and whereby said quality standard data and/or said cause criterion data and/or said priority ranking data is updated.