Competitive market conditions have brought the concept of “continuous improvement” to the fore. As a result of this, continuous quality improvement has an important role for the organization. Organizations that want to ensure continuous improvement need to use the most appropriate quality tools and techniques. Quality tools have the task of organizing and managing improvement across the organization. These basic tools and techniques collect, analyze and monitor data to solve process problems. This article describes the role of basic quality tools in the quality management system (PDCA cycle), 6 sigma (DMAIC), design for 6 sigma (DFSS-DMADV) and lean 6 sigma.

Introduction

The seven quality tools have a long history. All of these tools have been in use since 1920’s.

Seven quality control tools can be used for improving the performance of the all processes of production or service.

These seven quality tools which are basic for all other tools are:

• Check sheet
• Histogram
• Pareto diagram
• Cause-and-effect diagram.
• Scatter plot
• Flow chart
• Control chart

Tools are included for generating and organizing ideas, evaluating ideas, analyzing processes, determining root causes, planning, and basic data-handling and statistics.

7QC TOOLS – PDCA-CYCLE

Continuous improvement process is based on application of Deming’s quality cycle or PDCAcycle, shown on Fig. 1. The PDCA-cycle is integral part of process management and is designed to be used as dynamic model. The completion of one turn of cycle flows into the beginning of the next. [1]

A PDCA-cycle consists of four consecutive steps or phases, as follows:

• Plan – analysis of what needs to be improved by taking into consideration areas that hold opportunities for change.Decision on what should be changed.
• Do – implementation of the changes that are decided on in the Plan step.
• Check – Control and measurement of processes and products in accordance to changes made in previous steps and in accordance with policy, goals and requirements on products. Report on results.
• Act – Adoption or reaction to the changes or running the PDCA-cycle through again. Keeping improvement on-going. [2]

Main purpose of PDCA-cycle application is in process improvement. When the process improvement starts with careful planning it results in corrective and preventive actions, supported by appropriate quality assurance tools, which leads to true process improvement. Application of seven basic quality tools in correlation with four steps of PDCA-cycle is shown in Table 1.[1]

As it is shown in Table 1, for problem identification can be used most of the 7QC tools: Flow chart, Cause-and-Effect diagram, Check sheet, Pareto diagram, Histogram and Control charts. For problem analysis are used following tools: Cause-and-Effect diagram, Check sheet, Pareto diagram, Scatter plot and Control charts. When the team is developing a solution for analyzed problem Flow chart and Scatter plot can be useful. In the phase of achieved results evaluation can be also most of 7QC tools successfully implemented: Check sheet, Pareto diagram, Histogram, Scatter plot and Control charts [3].

7QC TOOLS IN SIX SIGMA

The tools of Six Sigma and operational excellence are most often applied within the framework of DMAIC. As such, DMAIC is an integral part of a Six Sigma initiative. DMAIC (Define, Measure, Analyse, Improve, and Control) refers to a data-driven life-cycle approach to Six Sigma projects for improving process; it is an essential part of a company’s Six Sigma programme. DMAIC is an acronym for five interconnected phases: define measure, analyse, improve and control. [4]

• Define by identifying, prioritizing and selecting the right project,
• Measure key process characteristic, the scope of parameters and their performances,
• Analyse by identifying key causes and process determinants,
• Improve by changing the process and optimizing performance,
• Control by sustaining the gain

Each of these processes (phases) can be realized with different quality tools and techniques (also 7QC) while some tools can be used in more than one processes (phases). One possible classification (use) of different quality tools and techniques in the Six Sigma methodology, proposed by the authors is presented in Fig. 2 [5].

DFSS (Design for Six Sigma) is a systematic and structured approach to new products or processes design that focuses on “problem prevention”. This is done with the aim of meeting or exceeding all the needs of the customer and the CTQ (critical to quality) output requirements when the product is first released. The major objective of DFSS is to “design things right the first time” One fundamental characteristic of DFSS is the verification, which differentiates it from Six Sigma. The proponents of DFSS are promoting it as a holistic approach of re-engineering rather than a technique to complement Six Sigma. [4]

Most frequently reported methodologies for putting DFSS into practice are DMADV (Define, Measure, Analyze, Design and Verify) and IDOV (Identify, Design, Optimise and Validate). DMADV is often described as the next stage of DMAIC (Six Sigma) and thus may lead to a generic approach [7]

In Table 2 a possible inclusion of 7QC tools in three methodologies is presented: continuous improvement PDCA-cycle, Six Sigma and Design for Six Sigma [6].

7QC TOOLS IN LEAN SIX SIGMA

 Lean Six Sigma are a set of methods that companies can apply to any manufacturing, transactional or service process to reduce waste, eliminate non-value-added actions and cut time. Combining “Lean” with “Six Sigma” can produce a program that brings both short-term results through the power of Lean, and long-term change through the power of Six Sigma. It is for this reason that many companies are turning to a combined Lean and Six Sigma effort.

• Lean means speed and quick action (reducing unneeded waiting time).
• Six Sigma means identifying defects and eliminating them.
• Lean Six Sigma Engineering means bestin- class and. It creates value in the organization to benefit its customers and saves money without capital investment. [2]
• The preceding steps with quality tools (also 7QC tools) and techniques for Lean Six Sigma Black Belt are shown in Fig. 3 below

Conclusion

 The basic quality tools (Check sheet, Histogram, Pareto diagram, Cause-and-effect diagram, Scatter plot, Flow chart, Control chart) has an important role of quality management system and this paper presents the roles of seven quality tools in continuous improvement process. Basic Quality Tools are often used in  PDCA cycle – DMAIC and DMADV phases and lean six sigma for data collecting, analyzing, visualizing.

Zeynep Ayça Gürel, Electrical Engineer – Quality Assurance

REFERENCES

[1] Pavletić, D., Soković, M., & Paliska, M. S. G. (2008). Practical application of quality tools. In 2nd International Quality Conference, Kragujevac.

[2] Soković, M., Jovanović, J., Krivokapić, Z., & Vujović, A. (2009). Basic quality tools in continuous improvement process. Journal of Mechanical Engineering, 55(5), 1-9.

[3] Pimblott J.G., Managing Improvement – Where to Start, Quality Forum, Vol. 16 (1990), No. 4, pp. 165-173.

[4] Sokovic, M., Pavletic, D., & Pipan, K. K. (2010). Quality improvement methodologies–PDCA cycle, RADAR matrix, DMAIC and DFSS. Journal of achievements in materials and manufacturing engineering, 43(1), 476-483.

[5] Soković, M. Jovanović, J. Krivokapić, Z.Vujović, A. Quality tools in improvement process, Proceedings of 2nd International Conference ICQME 2007, 12-14 September 2007, Budva, Montenegro, pp. 21-28.

[6] http://quality.dlsu.edu.ph/tools

[7] Scholtes, P. Brian, J.L. Streibel, B.J. The Team Handbook, Madison, WI: Joiner/Oriel Inc., USA, 2003.

[8] Taghizadegan, S. Essentials of Lean Six Sigma, Butterworth-Heinemann, UK, 2006.