259. Application of SPC and quality tools for process improvement
The implementation of quality tools and methodologies is necessary to reduce defective items, and thus reducing the overall quality costs. This can be achieved by reducing process variability, allowing further increase in organization’s competitiveness and sustainability.
The quality function within a company ensures compliance with product specifications and implements process improvements , to produce with greater efficiency.
This work was developed at a metal parts production company with the objective of improve the company's production through the application of quality methodologies and tools. From a large set of items produced by the company it was selected as object of this study the one that presented higher percentage of nonconformities. These nonconformities were related to the non-compliance with the specification of one variable (dimension 51).
The methodology used in this work can be structured in the following steps:
Step 1: Sample data collection of the critical variable in the production phase;
Step 2: Construction of X-s charts ;
Step 3: Assessment of process capability (calculation of Capability index Cpk);
Step 4: Analysis of the control charts and, comparison with historical data obtained during pre-production.
Step 5: Identify assignable causes of variability. If necessary, conduct Measurement System Analysis;
Step 6: Development of improvement proposals, to reduce variability of the critical variable.
3. Results and Discussion
The implementation of the SPC chart showed the process in statistical control but lacking the ability to produce parts within specification limits (Cp<1).
An analysis of SPC charts allowed to identify changes in the mean and the variability of the process, when compared with the data obtained in the pre-production (Cpk_pre-production >1.33).)
For the analysis of the causes of process variability brainstorming sessions were held and cause-effect diagram was designed.
Through the R&R study  it was verified that the measuring system is unacceptable for dimensional control and thus improvement suggestions were given.
This study allowed to identify the main causes of variability in the production process of a metal part, through the application of quality tools, and to propose measures to improve process and reducing the percentage of defective parts.
Loss of process capability from the pre-production phase to the production phase can be seen as a measure of process degradation.
 J. M. Juran, and A.B. Godfrey, “Juran's Quality Handbook”, 5th ed., McGraw-Hill, 1999.
 N. Rodrigues, “Aplicação de ferramentas da Qualidade para melhoria da produção numa empresa de soluções industriais”, MSc thesis in Quality Eng and Mgmt, University of Minho, 2016.
 D. Montgomery, “Introduction to Statistical Quality Control”, Arizona, John Wiley & Sons, 2008.