Monitoring system for determining progress in a fabrication activity

This invention relates to fabrication operations and, more specifically, to a system and a method for monitoring progress during fabrication of a part. Method for fabricating a structure. According to an exemplary embodiment, a structure is made by forming a layer of removable material with a first surface spaced a part from a second surface. The first surface is formed along a first region from which the material is removable. The first surface is altered by removal of material from the layer. Removed material from the first surface is monitored to detect fluctuations in a variable of composition in the layer, and removal of material from the first surface is terminated when the composition of monitored material meets a predetermined criterion. In an alternate embodiment a variable characteristic is imparted to a layer of material as a function of layer thickness and an operation is performed on the layer resulting in removal of material. Samples of removed material are monitored for variation in the characteristic and the operation is modified when a variation conforms with a criterion.