Data processing: generic control systems or specific application – Specific application – apparatus or process – Product assembly or manufacturing
Reexamination Certificate
2001-08-13
2003-02-25
Gaffin, Jeffrey (Department: 2182)
Data processing: generic control systems or specific application
Specific application, apparatus or process
Product assembly or manufacturing
C700S110000, C702S081000, C702S182000
Reexamination Certificate
active
06526326
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a method and a system for evaluating qualities of articles such as electric/electronic apparatuses for home use, products for office-automation (OA) and the like which are manufactured by assembling constituent parts. More particularly, the present invention is concerned with a fraction defective estimating method for estimating likelihood of occurrence of failure in the works involved in assembling an article, a system for carrying out the fraction defective estimating method and a storage medium storing therein data, information and program for executing the method.
Methods known heretofore for determining the fraction defective are primarily so designed as to estimate the causes for occurrence of defects, failures or the like, starting from the defect events or failure phenomena which have actually taken place. As the hitherto known typical methods of estimating the cause of failure or detect on the basis of the contents of the failure phenomenon or the defect event actually or really taken place at a stage in the course of manufacturing process, there may mentioned those disclosed in Japanese Unexamined Patent Application Publication No. 167631/1989 and Japanese Unexamined Patent Application Publication No. 196900/1994. These methods are based on such techniques that real records of defects occurred in the past are stored together with data concerning the causes of such defects in order to allow a degree of correlation between a defect pattern and the cause for the defect to be determined, whereon the cause for the defect is estimated on the basis of the correlation as determined. Further, as the diagnosis techniques in which the similar techniques are adopted, there may be mentioned those disclosed in Japanese Unexamined Patent Application Publication No. 13617/1995 and Japanese Unexamined Patent Application Publication No. 271587/1995.
However, any one of the known methods mentioned above is directed to the technique for estimating directly the causes of defect events or failure phenomena on the basis of the contents of such defects or failures which have really taken place for the purpose of allowing correcting or repairing work to be carried out speedily and properly.
On the other hand, as a method or procedure for performing in advance a quality evaluation of an article to be manufactured before failure or defect really occurs, there is known an FMEA (Failure Mode and Effects Analysis) technique which can already be adopted in the stage of designing the article to be manufactured. According to this method, an evaluator himself or herself predicts “failure phenomena which may occur in relation to individual parts constituting an article” and summarizes the “failure phenomena or events together with relations to the individual parts in the form of a list. Thus, by referencing the list, the evaluator himself or herself can predict “what sort of influence the article as manufactured will suffer when certain failure(s) or defect(s) occurs”. In this way, high-quality design suffering substantially no unintentional omissions can be realized.
Further, there is known a method or procedure for estimating seriousness of defects or failures relating to individual parts, respectively, by determining the probability of occurrence of failure phenomenon in relation to the individual parts as estimated by the evaluator (which probability is termed the fraction defective) and then estimating the degree of seriousness of defect of an article as manufactured which can be considered as being ascribable to the defect(s) of the individual parts. As a typical one of such techniques, there may be mentioned FMECA (Failure Mode, Effects and Criticality Analysis) technique.
However, any one of the conventional methods or techniques mentioned above is not in the position to estimate the potential of detector failure to occur in a given article with high accuracy. This is because substantially all the failure phenomena which may actually occur have to be grasped in the case of the conventional methods.
Under the circumstances, not a few manufacturing failures actually take place due to insufficiency of examination or studying, presenting one of the factors for deterioration of the quality of the manufactured article.
SUMMARY OF THE INVENTION
In the light of the art described above, it is an object of the present invention to provide a method and a system for estimating the potential of occurrence of failure in assembling a given article already in the stage preceding to manufacturing process, e.g. at a stage of design, manufacturing process planning or the like.
At this juncture, it should be mentioned that with the term “part”n used herein, it is contemplated to encompass both an elementary part and an assembled part or subassembly constituted by a plurality of the elementary parts. Accordingly, with a phrase “part attaching work”, it is intended to encompass both the attaching works not only for an elementary part but also an assembled part, respectively. Further, an elementary part or an assembled part which is to be attached to another elementary part or assembled part will be collectively referred to as “attachment-destined part” while the latter which is subjected to or undergoes the attachment will be referred to as “attachment-subjected part”.
In view of the above and other objects which will become apparent as the description proceeds, it is taught according to the present invention that an estimated value of assembling-related fraction defective which indicates likelihood of occurrence of defectives in an assembled article is determined on the basis of information concerning factors which exert influence to the probability of occurrence of failure in relation to the operations which are involved in part attaching works and which can not always be performed by a worker without fail. (The probability mentioned above will hereinafter be referred to also as the uncertainty.) In a preferred mode for carrying out the invention, the estimated value of the assembling-related fraction defective is arithmetically determined on the basis of information concerning the contents of operations involved in part attaching works, information concerning properties of an attachment-destined part or parts and information concerning properties of an attachment-subjected part or parts.
To this end, according to an aspect of the present invention, species or types of operations required for expressing the contents of the operations involved in the part attaching works (such as operation for downward movement, operation for horizontal movement and the like which are correctively referred to as standard attaching operation) are determined, and numerical values indicating low or high probabilities that standard attaching operations can not be performed without fail under predetermined conditions inclusive of “condition imposed by an operator or worker, condition imposed by a part and conditions imposed by a work-shop” (these conditions will be referred to as basic conditions) is determined or set for each of the standard attaching operations as determined. (The numerical values mentioned above will be referred to also as the standard-attachment-operation-based fraction defective coefficient.)
In another mode for carrying out the invention, an object under evaluation is expressed in terms of a combination of preset standard attaching operation elements for the purpose of facilitating user interface.
Furthermore, according to another aspect of the present invention, it is taught with a view to enhancing the estimation accuracy of the assembling-related fraction defective that in addition to the aforementioned standard attaching operation elements used for expressing the contents of attaching operations involved in the part attaching work, properties of the attachment-destined part and the attachment-subjected part which exert influence to the uncertainty of the attaching operation are expressed in terms of part-condition-related supplementary factors ment
Asano Masaaki
Kubota Takashi
Miyakawa Seii
Ohashi Toshijiro
Suzuki Tatsuya
Antonelli Terry Stout & Kraus LLP
Gaffin Jeffrey
Hitachi , Ltd.
Mai Rijue
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