Image analysis – Applications – Manufacturing or product inspection
Reexamination Certificate
1999-04-09
2001-07-24
Noland, Thomas P. (Department: 2856)
Image analysis
Applications
Manufacturing or product inspection
C382S111000, C700S110000, C700S144000, C700S302000, C702S036000, C702S081000, C702S123000, C702S189000
Reexamination Certificate
active
06266436
ABSTRACT:
BACKGROUND
This invention relates to apparatus and methods for automatically monitoring and evaluating manufacturing processes, and goods made by manufacturing processes. The invention relates to, for example, operations which produce an ongoing stream of outputs such as discrete absorbent articles, for example disposable diapers, effective to absorb body fluids. Such absorbent article products are typically fabricated as a sequence of work pieces being processed on a continuous web, typically operating on a processing line. Such absorbent article product generally comprises an absorbent core confined between a moisture impervious baffle of e.g. polyethylene and a moisture pervious body side liner of e.g. non-woven fibrous material. The absorbent articles are typically made by advancing one of the webs along a longitudinally extending path, applying the absorbent core to a first one of the webs, and then applying the second web over the combination of the first web and the absorbent core. Other elements such as elastics, leg cuffs, containment flaps, waste bands, and the like are added as desired for the particular product being manufactured, either before, during, or after, applying the second web. Such elements may be oriented longitudinally along the path, or transverse to the path, or may be orientation neutral.
Typical such manufacturing processes are designed to operate at steady state at a pre-determined set of operating conditions. While such process is operating at steady state conditions, the result desired from the process is desirably and typically achieved. For example, where the process is designed to produce a certain manufactured good, acceptable manufactured goods are normally produced when the process is operating at specified steady state conditions. As used herein, “steady state” conditions represents more than a single specific set of process conditions. Rather, “steady state” represents a range of specified process conditions which correspond with a high probability that acceptable goods will be produced, namely that the products produced will correspond with specified product parameters.
While a conventional such process is operating, sensors and other monitoring apparatus are typically used individually at various locations along the processing line to automatically sense various respective parameters with respect to, and to otherwise monitor the condition of, the good being manufactured. For example, in a diaper manufacturing operation, a sensor such as a photoelectric eye may be used to sense the presence or absence of a particular element of the diaper such as an ear, the edges of a waist band, the edge or edges of the absorbent core, or the like. In addition, a vision imaging system may be used as another form of sensor to detect and/or measure important dimensions or components on, the units of goods being manufactured.
Known analytical models and control models are based on assumptions that errors related to such sensings, collectings, and recordings are negligible, and thus that all determination signals, or absence of such determination signals, including quantitative signals, as well as the visual images and image analysis measurements made therefrom, are in fact accurate representations of the elements purportedly being detected and/or measured.
However, actual operation of many manufacturing processes, including highly automated processes, typically includes the occurrence of periodic, and in some cases numerous, errors, inaccuracies, or omissions in the determination signals and/or the visual images. Such errors, inaccuracies, or omissions may be caused by any of a variety of factors. Such factors may be, for example and without limitation, complete catastrophic failure of the sensor, intermittent failure of the sensor, error in sensor calibration, a transient out-of-calibration condition of the sensor, an effective obstruction between the sensor and the element to be sensed, or a loose or broken connection between the sensor and the computer or other controller to which the sensor is connected. Such factors also generally apply to vision imaging systems, including the lighting or camera, as well as numerous product component and process irregularities.
A variety of possible events in the manufacturing operation can cause the production of units of product which fall outside the specification range. For example, referring to manufacture of absorbent articles, stretchable materials can be stretched less than, or more than, the desired amount. Elements can become misaligned relative to correct registration in the manufacturing operation, or improperly folded over, or creased, or crimped, or torn. Timing between process steps, or speed of advance of an element, can stray from the target ranges. If non-catastrophic changes in process conditions can be detected quickly enough, typically process corrections can be made, and the variances from target conditions can accordingly be controlled such that the product remains within accepted specification ranges, without having to shut down the manufacturing operation, and preferably without having to cull, and thereby waste, product.
A variety of automatic product inspection systems are available for carrying out routine ongoing automatic inspection of product being produced on a manufacturing line, and for periodically and automatically taking samples for back-up manual evaluation. Indeed, periodic manual inspection and evaluation of product samples is still important as a final assurance that quality product is being produced. However, in high-speed manufacturing processes, the primary tool for ongoing product inspection is one or more computer controlled automatic inspection systems which automatically, namely without necessary direct human intervention, inspect the product being manufactured, preferably inspecting every unit of such product.
Where product is outside the accepted specification range, and should be culled, it is desired to cull all defective product, but only that product which is in fact defective. If too little product is culled, or if the wrong product is culled, then defective product is inappropriately released for shipment. On the other hand, if product which in fact meets accepted product specification is culled, then acceptable and highly valuable product is being wasted.
Body-fluid-absorbing absorbent articles such as are of interest herein for implementing the invention are typically manufactured at speeds of about 50 to about 1200 articles per minute on a given manufacturing line. Accordingly, and especially at the higher speeds, it is impossible for an operator to manually inspect each and every absorbent article so produced. If the operator reacts conservatively, culling product every time he/she has a suspicion, but no solid evidence, that some product may not meet specification, then a significant amount of in-fact-good product will have been culled. By contrast, if the operator takes action only when a defect has been confirmed using visual or other manual inspection, defective product may have already been released into the stream of commerce before the defective condition has been confirmed.
One way for the operator to inspect the product for conformity with the specification range is for the operator to periodically gather, at random, samples of the product being produced, and to inspect such random samples off-line. Random such inspections stand little prospect of detecting temporary out-of-specification conditions. On the other hand, where samples are taken by an operator in response to a suspected out-of-specification condition, given the high rate of speed at which such articles are manufactured, by the time the operator completes the inspection, the suspected offensive condition may have existed long enough that a substantial quantity of questionable or defective product will have either been shipped or culled without the operator having any solid basis on which to make the ship/cull decision. Further, automated manufacturing process controls may have self-cor
Bernhardt Wayne Allen
Bett Thomas Arthur
Giza Robert Jeffrey
Lemery Shawn Timothy
Ungpiyakul Tanakon
Kimberly--Clark Worldwide, Inc.
Noland Thomas P.
Wilhelm Thomas D.
Wilhelm Law Service
Yee Paul Y.
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