Diagnostic method for manufacturing processes

Abstract

A method for use in a system for diagnosing the causes of manufacturing defects involves process characterization. A set of forms is identified for a workpiece and for a piece of manufacturing equipment that acts upon the workpiece. The forms for the workpiece are preferably a hierarchic set of geometric forms. Each such geometric form corresponds to an aspect of the action of the manufacturing equipment upon the workpiece. A plurality of measurements is made on a defective workpiece following the hierarchical order of forms. The measurements are compared to a reference datum, and a deviation from the datum is computed. If the deviation exceeds a preselected threshold, an alert condition results, attributable to the action of the manufacturing equipment. Targeted adjustment corresponding to the action that caused the defect can then be made to the equipment.

1 . A method for diagnosing a cause of deviation from an intended form in a workpiece produced by a manufacturing process, in which at least one form is defined for the workpiece and manufacturing equipment acts upon the workpiece according to the manufacturing process to impart the form, the method comprising the steps of:
 defining a plurality of measurements for the workpiece, each relative to a respective reference datum;   taking the defined measurements for the workpiece;   generating a record of the measurements;   comparing the recorded measurements for each workpiece; and   inferring from the comparison of the measurements the existence of an alert condition associated with the action of the manufacturing equipment on the workpiece.