A progressive approach to joint monitoring of process parameters

Self Cite

Process control measures are mostly applied in production and manufacturing industries. The most important tool used in these disciplines is control chart. In manufacturing and production processes, when the quality characteristic of interest cannot be directly measured, it becomes essential to apply attribute control charts. To monitor fraction nonconforming of the output, quality practitioners mostly prefer p‐chart. In this article, a new progressive mean (PM) control chart is being proposed for monitoring drift in proportion of nonconforming products. The design evaluations of the proposed chart are made and compared through different properties of run length distribution, such as average run length (ARL), standard deviation of run length (SDRL), and some percentile points. The performance of the proposed chart is assessed under zero‐state and steady‐state scenarios. The proposed PM chart is compared with p‐chart, moving average (MA) chart, optimal CUSUM chart, modified exponentially weighted moving average (EWMA) chart, and runs rules p‐charts for monitoring fraction nonconforming. The proposed chart spots efficiently sustained disturbances in the process as compared with their existing counterparts. Two illustrative examples are also provided; one from real‐life application of nonconforming bearing and seal assemblies data and the other from simulated data for the implementation of PM chart.

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

On designing an efficient control chart to monitor fraction nonconforming

Abbas

Nazir

Akhtar

et al. 2019

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“…Abbasi suggested a new attribute control chart Poisson progressive mean (PPM) control chart for monitoring attribute. Zafar et al suggested joint monitoring of process parameters under the setup of PM. Most recently, Saeed et al proposed PM setup for simultaneous monitoring of linear profile parameters.…”

Section: Introductionmentioning

confidence: 99%

An enhanced approach for the progressive mean control charts

Abbas

Nazir

Akhtar

et al. 2018

Self Cite

To maintain and improve the quality of the processes, control charts play an important role for reduction of variation. To detect large shifts in the process parameters, Shewhart control charts are commonly applied but for small shifts, exponentially weighted moving averages (EWMA), cumulative sum (CUSUM), double exponentially weighted moving average (DEWMA), double CUSUM, moving average (MA), double moving average (DMA), and progressive mean (PM) control charts, are used. This study proposes double progressive mean (DPM) and optimal DPM control charts to enhance the performance of the PM chart. As the proposed DPM control charts use information sequentially, hence their performance is compared with natural competitors EWMA, CUSUM, DEWMA, double CUSUM, MA, DMA, and PM control charts. Run length and its different properties are evaluated to compare the performance of the proposed charts and counterparts. Results reveal that proposed optimal DPM outperforms the other charts. An example related to voltage on fixed capacitance level is also provided to illustrate the proposed charts.

“…Abbas et al 36 proposed a progressive mean (PM) chart for monitoring the mean of a process, and it was found very effective in detecting small and moderate shifts. Zafar et al 41 proposed a control chart based on PM statistic for the joint monitoring of location and dispersion parameters. Zafar et al 38 used the progressive structure to monitor the variance of a process.…”

mentioning

confidence: 99%

“…Abbasi 40 investigated the PM chart based on Poisson distribution. Zafar et al 41 proposed a control chart based on PM statistic for the joint monitoring of location and dispersion parameters. Abbas et al 42 proposed the double PM (DPM) and the optimal DPM to enhance the sensitivity of the PM chart.…”

mentioning

confidence: 99%

A progressive mean control chart for monitoring time between events

Alevizakos

Koukouvinos

2019

Control charts based on time between events (TBE) are widely used in highquality manufacturing processes where the events occur rarely. For monitoring such data, a new two-sided TBE control chart called progressive mean control chart (regarded as PM-TBE chart) is proposed in the present study. Through a simulation study and using the average run-length (ARL) measure, it is shown that the proposed chart outperforms the t r , ARL-unbiased gamma, GWMA-TBE, and DEWMA-TBE charts in detecting very small to moderate downward shifts, as well as in some cases small upward shifts. Moreover, the PM-TBE chart is very robust for moderate to large shifts when the true distribution of the TBE observations is a Weibull or a lognormal. Finally, examples are given to display the application of the proposed chart. KEYWORDSaverage run length, Erlang distribution, progressive mean, robustness, time between events | INTRODUCTIONControl charts based on time between events (TBE) are frequently used in high-quality processes where the rate of occurrences is low. The traditional Shewhart control charts for attributes, such as c chart, u chart, p chart, and np chart, are used to monitor the number or the proportion of nonconformities or defective products, 1 whereas TBE control charts are used to monitor the inter-arrival times between the occurrences of events, which are assumed to be exponentially distributed. 2 Many researchers have focused on the study of TBE control charts. Lucas 3 studied the cumulative sum (CUSUM) chart for exponentially distributed observations, while Vardeman and Ray 4 used integral equations to calculate the average run-length (ARL) of the exponential CUSUM chart. Gan 5 investigated the optimal design of the exponential CUSUM chart, and Gan and Choi 6 presented a program for calculating the ARL of the above control chart. Gan 2 proposed the exponentially weighted moving average (EWMA) control chart for exponential data computing its ARL using differential equations, and he found it slightly less sensitive than the exponential CUSUM chart. Chan et al 7 proposed a Shewhart-type chart, called cumulative quantity control chart (CQC chart) for monitoring exponential TBE data. Jones and Champ 8 studied the phase I of Shewhart-type TBE control charts. Xie et al 9 proposed a Shewhart-type control chart, namely, t r chart, based on the Erlang distribution, to monitor the time between r (r ≥ 1) failures. Borror et al 10 studied the robustness of the exponential CUSUM chart assuming that the TBE observations follow a Weibull or a lognormal distribution, and they showed that it is very robust for both small and large shifts of parameters. Liu et al 11 compared various one-and two-sided exponential TBE control charts. Liu et al 12,13 proposed CUSUM and EWMA schemes, respectively, for monitoring exponential data after transforming it to an approximate normal distribution using the double square root transformation. Zhang et al 14 proposed a TBE control chart based on gamma distribution using the Let Y t ∼ iid ExpðθÞ, t=1,2,… r...