Data processing: measuring – calibrating – or testing – Calibration or correction system
Reexamination Certificate
1999-02-08
2001-06-26
Shah, Kamini (Department: 2857)
Data processing: measuring, calibrating, or testing
Calibration or correction system
C702S159000, C702S199000
Reexamination Certificate
active
06253159
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 process line. Such absorbent article product generally comprises and 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 absorber 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 the 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. Namely, “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 are typically used individually at various locations along the processing line to automatically sense various respective parameters with respect to 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 leading edge of the absorbent core, or the like.
Known analytical models and control models are based on assumptions that errors related to such sensing are negligible, and thus that all determination signals, or absence of such determination signals, including quantitative signals, 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 in the determination signals. Such errors 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 the other controller to which the sensor is connected, as well as numerous component and process irregularities.
A variety of possible events in the manufacturing operation can cause the production of absorbent articles which fall outside the specification range. For example, 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 turn. Timing between process steps, or speed of advance of an element, can be out-of-tolerance. If such 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 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 into the stream of commerce. 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, it is impossible for an operator to manually inspect each and every 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 and inspect, off-line, physical samples of the product being produced. Random such inspections stand little prospect of detecting temporary out-of-specification conditions. 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 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-corrected the defect condition before the operator can complete the visual inspection and act on the results of such visual inspection. Thus, conventional manual inspection by an operator, while potentially providing the highest level of inspection quality, has little prospect of effectively monitoring and controlling temporary out-of-specification conditions, or of pro-actively controlling processing conditions which run higher than average risk of producing out-of-specification product.
While off-line inspection can be a primary determinant of quality, and typically defines the final quality and disposition of groups of the product, on-line inspection, and off-line evaluation of on-line-collected da
Arseneau Gerald Bernard
Bett Thomas Arthur
Ungpiyakul Tanakon
Kimberly--Clark Worldwide, Inc.
Miller Craig Steven
Seurer Jerad G.
Shah Kamini
Wilhelm Thomas D.
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