Integrated control scheme for optimal relaxed single-level continuous sampling inspection and process capability index

Abstract

The invention discloses an optimal relaxed single-level continuous sampling OCSP-V and process capability index Cpmk integrated control scheme. The method comprises the following steps: setting a detection number limit, a detection quality upper limit and a risk value; carrying out normality test on the latest production data, if the latest production data are qualified, calculating a process qualification rate and a lower confidence limit, otherwise, stopping the machine; calculating a pIOL value, a process capability and an index in a limit process state; and comparing the process qualified rate with the effective working interval, and deciding to execute the optimal scheme. In the effective interval, the number of continuous qualified products, the inspection score, the sample size and the process capability index key value are calculated, and an integrated control scheme is executed; and keeping recording the latest # imgabs0 # data, calculating a process capability index and a process qualification rate, and comparing the process capability index and the process qualification rate. The method is suitable for production quality control with tolerance upper and lower limit requirements and limited inspection capability, can meet quality, cost and two kinds of risk control at the same time, and can control the risk at a set level.

Description

Technical Field

[0001] The present invention relates to the field of quality control and statistical process control, in particular to a method based on optimal relaxed single level continuous sampling inspection (OCSP-V) and process capability index (C pmk ). This technical solution achieves real-time monitoring and optimization of the production process by dynamically adjusting the sampling inspection strategy and process capability assessment, and optimizes the risk control of the production process based on the process capability index. The present invention is suitable for large-scale continuous production environments. It streamlines the inspection process by optimizing risk control, reduces inspection costs, and ensures the stability and consistency of product quality. This solution is widely used in industries with strict quality requirements such as aviation, aerospace, automobiles, electronics, and pharmaceuticals. It is particularly suitable for scenarios with limited inspection capabilities and can control both types of risks within a predetermined level at the same time. Background Art

[0002] In modern manufacturing processes, the stability and consistency of product quality are the key to ensuring production efficiency and market competitiveness. Traditional quality control usually relies on fixed-ratio sampling inspection, which is prone to over-inspection or missed inspection, increasing production costs and quality risks. The optimal relaxed single-level continuous sampling inspection scheme (OCSP-V) is a dynamically adjusted inspection method that can reduce the sampling frequency and inspection costs while ensuring the effectiveness of the inspection. However, relying solely on OCSP-V for quality control may ignore the volatility and capability level of the production process. For this reason, OCSP-V is combined with the process capability index (CPI) to achieve a dynamic adjustment of the inspection method. pmk ) is combined with the sampling strategy to dynamically adjust the sampling strategy according to the production process capacity level and optimize the quality control plan. In the production process, this integrated control solution can effectively evaluate whether the process is stable and meets the specification requirements. pmk With OCSP-V, production efficiency can be significantly improved and quality risks can be reduced while ensuring product quality. This solution is particularly suitable for mass production environments with strict quality requirements such as aviation, aerospace, automobiles, electronics and pharmaceuticals, and is of great significance in improving the intelligence and automation level of production processes. Summary of the invention

[0003] To achieve the above object, the present invention provides the following technical solutions: 1. An optimal relaxed single-level continuous sampling inspection (OCSP-V) and process capability index (C pmk ) includes the following steps: (1) Given the current long-term average test number limit AFI L , average detection quality upper limit AOQL, first-class risk α and second-class risk β; (2) Use the latest n production data to perform a normality test. If the normal fitting value P-value ≥ 0.05, calculate the qualified product rate estimate and the lower confidence limit q * , otherwise stop and adjust; Calculate the process yield estimate using n numbers: Among them: USL is the upper tolerance limit, LSL is the lower tolerance limit, is the maximum likelihood estimate of the process qualification rate, Φ(·) is the normal distribution cumulative distribution function, Using sample variance S and sample mean Estimate the process standard deviation σ and process mean μ respectively, where n is the number of samples, x i =(i,...,n) is the sample observation value; Calculate the lower confidence limit for the process yield: in: is the value of the alpha quantile of the chi-square distribution with n-1 degrees of freedom; Calculate an estimator for the process failure rate: (3) When p = p IOL In normal process, AOQ=AOQL, AFI=AFI L Established at the same time. Find p IQL value; (4) Compare with the effective working range (1-10AOQL, 1-AOQL] and make a judgment: Exemption from inspection; Stop production for repairs; Perform OCSP-V; known p IQL Value, find the process capability C of the process that is equal to the quality requirement AOQL , the process capability index C of the limiting process IQL ; Then calculate the number of consecutive qualified products i in the optimal relaxed single-level continuous sampling inspection plan oV and the test score f in the score test phase oV , and determine the sample size and process capability index key value C pk0 ; Quality control parameters of the integrated control scheme ioV and f oV is the solution of the following system of equations: Risk control parameters for integrated control schemes and C pmk0 is the solution of the following system of equations: Where: b1 = 3C AOQL +|ξ|,b2=3C IQL +|ξ|, G(·) is the χ with n-1 degrees of freedom 2 Distribution function, φ(·) represents the density function of the standard normal distribution. (6) The execution parameters are (i oV ,f oV )'s OCSP-V scheme; (7) Keep records up to date Test data, using Process capability index estimator and process yield estimator and will With C pmk0 , With q * Make comparisons; The calculation method is: like and Then continue to step (4); if Then stop and adjust; if and Then return to the normality test step. Compared with the prior art, the present invention has the following advantages: 1. Improve inspection efficiency: By combining OCSP-V and C pmk , the solution can significantly reduce unnecessary comprehensive inspections, optimize sampling strategies, reduce inspection costs and improve overall production efficiency. 2. Dynamically adjust the sampling plan: Improve the accuracy of quality management: By introducing q * Indicators and plans can adjust the inspection plan in real time according to the capacity level of the production process to ensure that the sampling inspection matches the actual production situation, thereby improving the accuracy and effectiveness of quality management. 3. Quantitative control of the first and second types of risks: This solution can control both types of risks (accepting defective products and rejecting qualified products) at the same time, ensure the reliability of product quality, and reduce costs and losses caused by quality problems. 4. Reduce the risk of over- or under-inspection: Use the yield estimator Real-time monitoring and comparison with quality requirements AOQL ensures that when process capability is high, excessive inspection is reduced, when process capability is low, inspection is strengthened, and when process capability seriously deteriorates, production is stopped for repairs to avoid the risk of excessive or insufficient inspection. 5. Real-time monitoring of process status; effectively preventing cost increases caused by process deterioration: by introducing C pmk Build C pmk0 The process capability fluctuation control indicator and solution can not only reflect the capability level of the production process in real time, but also ensure timely stop loss when the process capability deteriorates and causes cost increase, thereby improving the accuracy of process control. 6. Applicable to complex production environments: This solution can adapt to the quality control needs under high variation and complex production conditions, and is particularly suitable for production lines that require frequent adjustments to inspection strategies. 7. Reduce overall quality control costs: By optimizing the design of sampling inspection, this integrated solution can reduce unnecessary inspection resource investment and reduce overall quality control costs while ensuring quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0004] Figure 1 It is a flow chart of the present invention. DETAILED DESCRIPTION

[0005] The following will be combined with the appended Figure 1 , combined with examples, the technical solutions in the embodiments of the present invention are clearly and completely described. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of invention protection. See also Figure 1 As shown, a technical solution provided by the present invention is: An Optimal Relaxed Single-Level Continuous Sampling Test OCSP-V and Process Capability Index C pmk When using, follow the steps below. (1) Given the current long-term average test number limit AFI L =0.7, average detection quality upper limit AOQL=0.00143, first category risk α=0.01 and second category risk β=0.05. (2) Under the limit process, find p IOL The process capability is equal to the process capability C of the quality requirement. AOQL , the process capability index C of the limiting process IQL . p IOL =0.004767 C AOQL =1.062842 C IQL =0.940798 (3) Use the latest 100 production data to perform a normality test. If the normal fitting value P-value ≥ 0.05, calculate the qualified product rate estimate and the lower confidence limit q * , otherwise stop and adjust. 100 cylinder head inner diameter fine grinding data of the grinder Unit: mm The normal fitting value P-value of this batch of processing data is: P-value=0.355≥0.05 Process yield estimator: Process Nonconformance Rate Estimator: Lower confidence limit for process pass rate: q * =0.993837 (4) Implement the optimal continuous sampling inspection plan for quality control. (5) Calculate the control parameter i of the integrated control scheme oV 、f oV , and C pmk0 . i oV =2451 f oV =0.003138 C pmk0 =0.99122 (6) The execution parameters are (i oV ,f oV )=(2451,0.003138). (7) At the same time, keep records of the latest 849 inspection data and use the 849 data to calculate the process capability index estimate and process yield estimator when and Then continue to step (6); if Then stop and adjust; if and Then return to the data collection step. The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. The above embodiments and descriptions are only preferred examples of the present invention and are not intended to limit the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. An optimal relaxed single-level continuous sampling inspection (OCSP-V) and process capability index (C pmk ) includes the following steps: (1) Given the current long-term average test number limit AFI L , average detection quality upper limit AOQL, first-class risk α and second-class risk β; (2) Use the latest n production data to perform a normality test. If the normal fitting value P-value ≥ 0.05, calculate the qualified product rate estimate and the lower confidence limit q * , otherwise stop and adjust; Calculate the process yield estimate using n numbers: Among them: USL is the upper tolerance limit, LSL is the lower tolerance limit, is the maximum likelihood estimate of the process qualification rate, Φ(·) is the normal distribution cumulative distribution function, Using sample variance S and sample mean Estimate the process standard deviation σ and process mean μ respectively, where n is the number of samples, x i =(i,...,n) is the sample observation value; Calculate the lower confidence limit for the process yield: in: is the value of the alpha quantile of the chi-square distribution with n-1 degrees of freedom; Calculate an estimator for the process failure rate: (3) When p = p IOL In normal process, AOQ=AOQL, AFI=AFI L Established at the same time. Find p IQL value; (4) Compare with the effective working range (1-10AOQL, 1-AOQL] and make a judgment: Exemption from inspection; Stop production for repairs; Implement OCSP-V; Known p IQL Value, find the process capability C of the process that is equal to the quality requirement AOQL , the process capability index C of the limiting process IQL ; Then calculate the number of consecutive qualified products i in the optimal relaxed single-level continuous sampling inspection plan oV and the test score f in the score test phase oV , and determine the sample size and process capability index key value C pmk0 ; Quality control parameters of the integrated control scheme i oV and f oV is the solution of the following system of equations: Risk control parameters for integrated control schemes and C pmk0 is the solution of the following system of equations: Where: b1 = 3C AOQL +|ξ|,b2=3C IQL +|ξ|, G(·) is the χ with n-1 degrees of freedom 2 Distribution function, φ(·) represents the density function of the standard normal distribution. (5) The execution parameters are (i oV , f oV )'s OCSP-V scheme; (6) Keep records up to date Test data, using Process capability index estimator and process yield estimator and will With C pmk0 , With q * Make comparisons; The calculation method is: like and Then continue to step (4); if Then stop and adjust; if and Then return to the data collection step.

2. An optimal relaxed single level continuous sampling test (OCSP-V) and process capability index (C pmk ) is an integrated control solution that is suitable for quality control of production processes with upper and lower tolerance requirements and limited inspection capabilities, achieving simultaneous control of quality, cost and two types of risks.

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