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  In-process vision detection of flaws and fod by back field illuminationUSPTO Application #: 20060108048Title: In-process vision detection of flaws and fod by back field illumination Abstract: A flaw and foreign object debris (FOD) detection system (11) for use during fabrication of a structure (12) includes an illumination device (13). The illumination device (13) is configured to be in proximity with a fabrication system (10) and illuminates a portion (18) of the structure (12). The illumination device (13) directs light rays (16) at acute angles relative to the portion (18). A detector (14) monitors the portion (18) and detects FOD in the portion (18) during fabrication of the structure (12) in response to the reflection of the light rays (16) off of the portion (18). (end of abstract)
Agent: Artz & Artz, P.C. - Southfield, MI, US Inventors: Roger W. Engelbart, Reed Hannebaum, Tim Pollock USPTO Applicaton #: 20060108048 - Class: 156064000 (USPTO) Related Patent Categories: Adhesive Bonding And Miscellaneous Chemical Manufacture, Methods, Surface Bonding And/or Assembly Therefor, With Measuring, Testing, Or Inspecting The Patent Description & Claims data below is from USPTO Patent Application 20060108048. Brief Patent Description - Full Patent Description - Patent Application Claims
TECHNICAL FIELD [0001] The present invention relates generally to the fabrication of composite structures. More particularly, the present invention relates to systems and methods of detecting flaws and foreign object debris (FOD) during the fabrication of a composite structure. BACKGROUND OF THE INVENTION [0002] Composite structures have been known in the art for many years. Although composite structures can be formed in many different manners, one advantageous technique for forming composite structures is a fiber placement or automated collation process. According to conventional automated collation techniques, one or more ribbons of composite material, known as composite strands or tows, are laid down on a substrate. The substrate may be a tool or mandrel, but more conventionally, is formed of one or more underlying layers of composite material that have been previously laid down and compacted. [0003] Conventional fiber placement processes in the formation of a part utilize a heat source to assist in the compaction of the plies of composite material at a localized nip point. In particular, the ribbons or tows of the composite material and the underlying substrate are heated at the nip point to increase resin tack while being subjected to compressive forces to ensure adhesion to the substrate. To complete the part, additional strips of composite material can be applied in a side-by-side manner to each layer and can be subjected to localized heat and pressure during the consolidation process. [0004] Unfortunately, defects can occur during the placement of the composite strips onto the underlying composite structure. Such defects can include tow gaps, overlaps, dropped tows, puckers, and twists. Additionally, foreign objects and debris (FOD), such as resin balls and fuzz balls, can accumulate on a surface of the composite structure. Resin balls are small pieces of neat resin that build up on the surfaces of the fiber placement head as the preimpregnated tows pass through the guides and cutters. The resin balls become dislodged due to the motion and vibration of the fiber placement machine, and drop on to the surface of the ply. Subsequent courses of applied layers cover the resin ball and a resultant bump is created in the laminate whereat there may be no compaction of the tows. The fuzz balls are formed when fibers at the edges of the tows fray and break off as the tows are passed through the cutter assembly. The broken fibers collect in small clumps that fall onto the laminate and are covered by a subsequent layer. [0005] Composite laminates fabricated by fiber placement processes are typically subjected to a 100 percent ply-by-ply visual inspection for both defects and FOD. Typically, these inspections are performed manually during which time the fiber placement machine is stopped and the process of laying materials halted until the inspection and subsequent repairs, if any, are completed. In the meantime, the fabrication process has been disadvantageously slowed by the manual inspection process and machine downtime associated therewith. [0006] Current inspection systems are capable of identifying defects in a composite structure during the fabrication process without requiring machine stoppage for manual inspections. The inspection systems are capable of detecting and identifying FOD "in-process" or during the fabrication of a composite structure. This, in turn, eliminates the need for manual FOD inspections and the machine downtime associated therewith. [0007] A split illumination technique has been introduced for the detection of flaws and FOD simultaneously. A first half of a viewing area, referred to as the bright field, is illuminated. A second half of the viewing area, referred to as the dark field, is not illuminated. The flaws in the composite structure are detectable within the bright field, but are indistinguishable in the dark field. The FOD is detectable in the dark field, but is indistinguishable in the bright field. Thus, the split illumination technique requires the use of dual illumination levels. The use of dual illumination levels complicates the inspection process by causing a single field to be viewed twice, which is time consuming. A single field must be viewed twice to inspect for both flaws and FOD. [0008] Thus, there exists a need for an improved system and method of the detection and identification of flaws and FOD within a composite structure during the fabrication thereof that simplifies and minimizes the time involved in the inspection of that composite structure. SUMMARY OF THE INVENTION [0009] The present invention provides a flaw and foreign object debris (FOD) detection system for use during the fabrication of a structure. The detection system includes an illumination device. In one embodiment of the present invention, the illumination device is configured to be in proximity with a fabrication system and illuminates a portion of the structure. The illumination device directs light rays at acute angles relative to the portion. A detector monitors the portion and detects FOD in the portion during fabrication of the structure in response to reflection of the light rays off of that portion. [0010] In another embodiment of the present invention, the illumination device directs light rays, having a single illumination level, at the portion and at acute angles relative to the portion. A detector monitors the portion and detects a flaw and FOD simultaneously in the portion during fabrication of the structure. [0011] The embodiments of the present invention provide several advantages. One such advantage is the provision of a composite structure in-process fabrication inspection technique that allows for the simultaneous detection of flaws and FOD for a single field of inspection. [0012] Another advantage provided by an embodiment of the present invention, is the provision of a composite structure in-process fabrication inspection technique that allows for the simultaneous detection of flaws and FOD using a single illumination level. [0013] Furthermore, the present invention simplifies the composite structure inspection process and minimizes the time involved therein. [0014] Moreover, the present invention allows for the in-process repair of a composite structure upon detection of a flaw or FOD. [0015] The present invention itself, together with further objects and attendant advantages, will be best understood by reference to the following detailed description, taken in conjunction with the accompanying drawing. BRIEF DESCRIPTION OF THE DRAWINGS [0016] FIG. 1 is a side schematic view of a fabrication system incorporating a flaw and FOD detection system in accordance with an embodiment of the present invention; [0017] FIG. 2 is a perspective view of an application portion of a fabrication system incorporating a flaw and FOD detection system in accordance with another embodiment of the present invention; [0018] FIG. 3 is a perspective view of light sources according to the embodiment of FIG. 2; [0019] FIG. 4 is a perspective view of a fabrication system incorporating a flaw and FOD detection system in accordance with another embodiment of the present invention; [0020] FIG. 5 is a logic flow diagram illustrating a method of detecting flaws and FOD in a composite structure in accordance with an embodiment of the present invention; Continue reading... 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