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Deploying Six Sigma

The Six Sigma improvement model is designed to dramatically improve performance in existing processes. It was originally conceived at Motorola using a Juran breakthrough improvement model, and it is considered one of the most successful process improvement models ever developed because it enables a systematic analysis of current process performance

TABLE 9.3

Current Quality Programs and Methods

Quality Method

Description

Deming/Shewart

Dr. W. Edward Denting advocated that the system was the problem, not the people. Deming and Walter Shewart proposed a process improvement model called the Deming Wheel, which consists of four phases: Plan, Do, Study, Act.

Juran

Key concepts of Dr. Joseph Juran were quality improvement could be achieved using continuous improvement or breakthrough methods; quality experts need to speak the language of senior management and ensure quality is customer- and business-focused, and organizations should invest in preventive measures to reduce failure costs associated with quality, such as scrap, rework, and warranty expenses.

Total Quality Management (TQM)

A continuous-improvement program that is designed to involve everyone in an organization to improve their processes using simple quality- oriented tools. Although the concept is good, deployments are usually targeted isolated processes, so customer and business benefits are sporadic.

Continuous Improvement

A variation of the total quality management concept, it has been recently revitalized by the tool sets contained in Lean and Six Sigma.

Kaizen Events

Similar to continuous improvement, except the process analysis and improvements are focused on a small portion of a process or workstream over a short time period, resulting in immediate benefit to an organization. Simple Lean and Six Sigma tools are used in Kaizen Events.

Lean

A process improvement program that focuses on simplification, standardization, elimination of process waste, and mistake-proofing of processes to improve quality.

Six Sigma

A phased methodology to improve quality characterized by five phases: define, measure, analyze, improve, and control. It was initially developed at Motorola using Juran’s breakthrough method.

(continued)

TABLE 9.3 (Continued)

Current Quality Programs and Methods

Quality Method

Description

Malcom Baldrige Award

A system for measuring organizational performance relative to measurement and control of processes; it is based on how well procedures are followed, and it utilizes a point system. Quality is improved through an auditing process that identifies process breakdowns.

International Standards Organization (ISO)

A group of standards that organization must follow. These standards set forth a minimum level of quality that organizations must maintain to sell their products around the world.

Automotive Industry Action Group (AIAG)

The AIAG system consists of five sets of deliverables designed to design and produce a product to service: (1) quality product planning and VOC; (2) product design and design for manufacturing; (3) process design and development; (4) product and process validation; and (5) control plan methodology.

and provides a detailed roadmap to identify root causes and eliminate them to improve process capability. It aligns to the VOC and the voice of the business (VOB) to increase quality and productivity and to sustain higher performance. An effective quality improvement strategy drives operational excellence across an organization, from the business- unit level to the local process level. Figure 9.1 describes a general quality improvement model. This deployment process is generally faster than that of TQM, but it depends on well-defined and well-executed projects. Figure 9.2 shows the major differences between TQM and Six Sigma. TQM focuses on the elimination of a problem’s root causes using simple quality tools and methods. TQM activities have migrated into the Six Sigma Green Belt role in some organizations. Six Sigma offers several advantages that were initially absent from TQM deployments.

Six Sigma is a top-down alignment versus the bottom-up approach that is a characteristic of TQM. A second advantage is that Six Sigma provides significant business benefits for organizations, and these benefits can be realized relatively quickly once projects are deployed. As a result, TQM was augmented by Six Sigma in the mid-1990s. Different organizations approach quality improvement from either a TQM focus with Six Sigma augmentation or vice versa. Six Sigma has often been deployed as

FIGURE 9.1

Quality improvement model. Quality improvement projects are selected to improve operational competencies, drive improvements in profit & loss statements and the balance sheet, and improve customer value.

a project-based initiative that must be integrated into an organization’s quality assurance systems. A reliance on Six Sigma alone to improve and sustain process improvements is risky because, in the absence of formal quality systems and TQM, in which most employees are trained, Six Sigma process improvements will deteriorate over time. The program was always

FIGURE 9.2

Rate of process improvement.

FIGURE 9.3

Key characteristics of Six Sigma. Six Sigma helps organizations make the transition from tactical problem solving to business process development and customer excellence.

designed to include a fraction of employees to achieve breakthrough improvement while most employees engage in continuous improvement.

The concept of “breakthrough” improvements in quality and aligning projects with goals that are important to leadership helps secure resources for projects. Figure 9.3 shows important characteristics of an effective Six Sigma program. The deliverables are achieved using the five Six Sigma phases: define, measure, analyze, improve, and control (DMAIC). The DMAIC phases are further expanded into ten to twelve steps (depending on the organization), with each step having key deliverables. Over an extended period, an organization will mature into a Six Sigma performing culture if it has quality assurance and management infrastructure that supports continual improvement.

The DMAIC methodology is applied to improve the performance of customer critical-to characteristics (CTs). Figure 9.4 shows the breakthrough concept applied to a single CT characteristic, namely a critical- to-quality (CTQ) variable or key process output variable (KPOV). This could be processing defect percentage, lead time, or another quantified variable. Notice that this KPOV exhibits variation around its average (or mean) level. There may also be periodic disruptions occurring within a process, or spikes in the CTQ, causing non-random patterns. These are called assignable causes of process variation. In the absence of assignable causes of variation, a process exhibits common case variation or random variation of the CTQ around its mean value.

The concept of assignable versus common cause variation will be discussed later in this chapter in the control charts discussion. A process that exhibits common cause variation remains at its mean, which may good or bad from a customer’s perspective. If the mean is not at an optimum level or exhibits high variance (or both), then the root causes of the common

FIGURE 9.4

What is Six Sigma? Six Sigma is a methodology to proactively enable the transformation of an organization from a functionally oriented, reactionary operation to a cross-functional, process-focused, continuously improving, learning organization.

cause variation should be investigated through data collection and analysis to eventually eliminate it from the process. If this is a chronic problem and the process variable is stable, it can be a difficult task to eliminate root causes without a project having focused resources. The goal of the DMAIC methodology to achieve breakthrough performance levels. This concept is shown in Figure 6.4 as before-and-after curves. Figure 9.4 also lists some common “Sigma” levels correlating to customer satisfaction. These “Sigma” levels will be discussed later in this chapter.

The DMAIC phases are broken down as shown in Table 9.4, with deliverables and the tools and methods used to achieve the deliverables within each phase. There may be additional tools depending on the application. Some of these tools and methods may be used in more than one DMAIC phase. This methodology helps define a process problem relative to its extent, occurrence, and impact on customers. A Six Sigma team first estimates accurate CT baselines using measurement system analyses,

TABLE 9.4

DMAIC Problem-Solving Methodology

Phase

Deliverables

Tools and Methods

Define

Define the problem including its extent, occurrence frequency, customer and business impact.

  • • Problem statement
  • • High-level process mapping
  • • Metrics analysis
  • • Cost of Quality Analysis (COQ)

Measure

Verify the CT can be measured accurately and precisely, determine baseline capability of the CT and develop a data collection plan on the inputs and the CT.

  • • Problem statement
  • • High-level process mapping
  • • Metrics analysis
  • • Cause and effects
  • • Failure mode and effects (FMEA)
  • • Measurement system analysis (MSA)
  • • Basic statistics/process capability
  • • Cost of Quality Analysis (COQ)

Analyze

Eliminate the trivial inputs and develop a short list of KPIVs impacting the CT or KPOVs.

  • • Basic statistics
  • • Graphical analysis tools
  • • Hypothesis testing/contingency tables
  • • One-way ANOVA
  • • Multi-Vari analysis
  • • Correlation/regression
  • • Detailed process map

Improve

Experiment with the KPIVs and KPOVs to determine their interrelationships and select the best combination of KPIV levels to optimize the KPOVs.

  • • General full factorials
  • 2k full factorials
  • • Fractional factorials
  • • Response surface designs

Control

Ensure the improved process will be sustainable and remain in control.

  • • Statistical process control/ mistake-proofing
  • • Measurement control
  • • Maintenance/training
  • • Validate capability
  • • Control plans
  • • Final Cost of Quality Analysis (COQ) review

CT = critical-to characteristic; KPIV = key process input variables; KPOV = key process output variables; ANOVA = analysis of variance.

capability analyses, and data collection and analysis. The analysis is completed in sequence in the define, measure, and analyze phases. In the improve and control phases, the process is modified based on the root- cause analysis, and solutions are implemented to eliminate the root causes to a move the CT to a new performance level. We will now discuss the tools and methods of each DMAIC phase.

 
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