Feature-based Determination Method of Process Capability Index for Multi-variety and Small-batch Production Parts

Abstract

The invention discloses a multi-kind and small-quantity part production process capability index determining method based on features. The multi-kind and small-quantity part production process capability index determining method based on the features is characterized in that firstly, processing features are taken as objects, processing feature quality characteristic values which are different in size and identical in processing technology and tolerance grade are defined as the same processing feature sample, wherein the ratio of the standard deviation and the tolerance of the processing feature quality characteristic values is a constant; secondly, sample individuals are normalized, the mean values of the sample individuals are the same, namely the sample individuals conform to the same type of distribution; finally, a process capability index is calculated based on processing feature samples. According to the multi-kind and small-quantity part production process capability index determining method based on the features, the problem of sample size of multi-kind and small-quantity production is fundamentally solved, and conversion from interval estimation to point estimation of the process capability index oriented to multi-kind and small-quantity production is achieved. The obtained process capability index can be used for calculating the disqualification rate of the processing feature quality characteristic values, the processibility analysis is performed on feature design structures according to the disqualification rate, the proper design structures are selected, 100 percent detection is avoided, and the detection efficiency is improved.

Description

technical field [0001] The invention relates to a process control method of mechanical processing, especially a process control method that can greatly improve processing efficiency and reduce the number of inspections without affecting the overall product quality, specifically a feature-based multi-variety and small-batch production Confirmation method of part process capability index. Background technique [0002] As a quantitative evaluation of process capability, Process Capability Index (PCI) is an important content of Statistical Process Control (SPC) theory, and has been widely used in product structure design, tolerance optimization, cost control, process decision-making and quality management And so on. The traditional process capability index calculation has strict requirements on the statistical sample size, the larger the sample size, the better the obtained process capability index can reflect the actual process capability. For multi-variety and small-batch pr...

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Problems solved by technology

[0009] The purpose of the present invention is to solve the problem that the process capability index is difficult to calculate accurately due to insufficient sample capacity in multi-variety and small-batch production. The index calculates the unqualified product rate of the processing characteristic quality characteristic value, analyzes the machinability of the characteristic design structure according to the unqualified rate, and selects the appropriate design structure; automatically selects the typical processing technology plan, so that each quality characteristic value on the part reaches The required rate of qualified products; analysis of the necessity of detection for each processing state of the feature, avoiding 100% detection, and improving the efficiency of detection

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