Intended learning outcomes: Identify the cause of differences between stakeholders’ expectations and actual product or process characteristics. Explain quality function deployment – the house of Quality and 10 steps of implementation. Describe the SIPOC diagram and the CTQ matrix.
Quality planning is a term used today for all planning activities prior to the start of production; quality planning sets goals and works toward achieving the goals and preventing failures.
Analogously to this definition, in the PDCA Plan phase as well as in the Six Sigma Define phase, the project team identifies what is important to the customer (captures the “voice of the customer”[note 1801]), the goals, and the scope and boundary of the project. Inclusion of stakeholders in quality planning means that, for all of these tasks and activities, the quality of the outcome must be evaluated to determine whether it satisfies stakeholders’ needs. Figure 18.2.3.1 shows potential discrepancies between stakeholder needs and product characteristics that can arise during execution of the whole task from subtask to subtask.
Fig. 18.2.3.1 Cause of differences between stakeholders’ expectations and actual product or process characteristics.
Discrepancies can arise due to the following:
- Assumed or implied needs have to be translated into words or symbols — that is, identified and established — in the language used by stakeholders. Here, there is the danger that the translation will fail to be accurate.
- The stated expectations determined have to be broken down into ideas or expectations concerning requirements for the product and the process to be developed. This is often connected with a transition from relatively general quality characteristics to more specific ones. The result is a detailed, functional picture or functional model, which again is expressed in the language used by stakeholders.
- The functional pictures or models determined for the product and the process are translated into specific quality requirements, but now in the language used by the provider/supplier. Finally, the requirements are described in specifications, called product requirement specifications, which are more technical descriptions.
- The technical descriptions are transferred into designs, plans, and recipes. This is the actual development and design of product and process. The output then undergoes validation, which is the process of ensuring that the product conforms to the original stakeholder needs and requirements.
A typical method used in the quality planning phase is quality function deployment.
Quality function deployment (QFD) is step-by-step development of quality functions. The QFD process uses matrices to translate customer requirements into technical design parameters or characteristics.
To do this, a quality chart called the “House of Quality” is employed as a correlation matrix linking quality characteristics and target values and their tendency. See Figure 18.2.3.2.
Fig. 18.2.3.2 Quality function deployment: House of Quality and 10 steps of implementation (Source: [Guin93]).
The 10 steps of implementation in Figure 18.2.3.2 are taken from [Guin93]:
- Gather customer requirements for the product or service.
- Customers weight the importance of each of the requirements.
- Ask customers to rate competitors’ products or services.
- Technical descriptors. Translate customer requirements into quality characteristics.
- Determine relationship matrix between customers’ needs and technical descriptors.
- Estimation of the importance of the technical descriptors.
- Conduct analysis of competitor’s technical descriptors.
- Estimate degree of difficulty, technical feasibility.
- Determine target values for each technical descriptor.
- Determine variation for each technical descriptor and examine mutual reaction.
The first-pass yield (FPY) is the percentage of results (i.e., units) that pass on first test — that is, without requiring rework.
An increased FPY entails reduced costs due to rework. Development is successful if the defect rate can be rapidly reduced once the product is introduced or if it is zero from the start (zero-defect rate). As the development process is essentially a creative one and can contain errors, defects can always be expected with an innovation. The need to reduce development time and development costs also speaks against a zero-defect rate. For these reasons, defects will be accepted at first, and importance will be placed on reducing this rate rapidly once the product is introduced. Then, it is important to have sufficient capacity for rapid revision and a comprehensive information system for capturing the responses of the first customers.
For example, during quality planning, quality requirements — together with the original ideas about the requirements — are translated into an offer to customers that describes the company’s product or service. This description, which is often a component of a contractual agreement, can already deviate decisively from the customer’s expectations, so that at this point in time at the latest, a decision must be made as to whether the individual steps of quality planning should be repeated (non-first-pass yield).
With this, the Define, or quality planning, phase entails capturing the relevant processes. In Six Sigma, this is represented in SIPOC diagrams.
The SIPOC diagram shows the system with Inputs, Process, and Outputs as well as the Suppliers and the Customers. See Figure 18.2.3.3.
In this phase, the diagrams show the actual state, before all work begins. On the basis of the diagramming of the process, the critical elements will then be worked out.
Fig. 18.2.3.3 SIPOC diagram.
CTQs (Critical to Quality) are key measurable characteristics (e.g. regarding quality, costs, or delivery), elements of the process, or practices that have a great and direct effect on the customer’s perception of the quality of a product or service. See Figure 18.2.3.4.
Fig. 18.2.3.4 CTQ matrix.
CTQs are usually represented in a matrix, or CTQ tree, that shows the (sub-)products and their critical attributes on the horizontal axis. The processes that can lead (or not lead) to these critical characteristics, process elements, or practices are shown on the vertical axis.
The Six Sigma method revisits the outcomes to be delivered (deliverables) again and again:
- Are the project teams well trained and motivated?
- Have the customers been identified and CTQs defined?
- Has the project management handbook been drawn up?
- Have the business processes been diagrammed appropriately (e.g. using SIPOC)?
Each of these questions is revisited repeatedly throughout the entire phase in greater detail, in order to ensure that they are handled comprehensively.
Course section 18.2: Subsections and their intended learning outcomes
18.2 Quality Management Tasks at the Operations Level
Intended learning outcomes: Produce an overview on the Deming Cycle (PDCA Cycle) and the Shewhart Cycle as well as the Six Sigma Phases. Present the phases of quality planning, control, assurance, and activation of the Deming Cycle. Describe the Six-Sigma phases of define, measure, analyze, improve, and control. Differentiate between continual improvement and reengineering.
18.2.1 The Deming Cycle (PDCA Cycle) and the Shewhart Cycle
Intended learning outcomes: Produce an overview on The Shewhart cycle developed in statistical quality control. Present the Deming cycle. Describe quality management tasks in the Deming cycle.
18.2.2 DMAIC — The Six Sigma Phases
Intended learning outcomes: Present DMAIC, the Six Sigma phases. Describe the tasks in the Six Sigma phases. Differentiate between DMAIC, RDMAIC, DMAICT, and DMADV.
18.2.3 Quality Planning: PDCA Plan Phase — DMAIC Define Phase
Intended learning outcomes: Identify the cause of differences between stakeholders’ expectations and actual product or process characteristics. Explain quality function deployment – the house of Quality and 10 steps of implementation. Describe the SIPOC diagram and the CTQ matrix.
18.2.4 Quality Control: PDCA Check Phase, Part 1 — DMAIC Measure Phase and Analyze Phase, Part 1
Intended learning outcomes: Produce an overview on tools used in quality control in their original usage stemming from production engineering. Identify deliverables of the Measure phase as well as the Analyze phase.
18.2.5 PDCA Do Phase — DMAIC Improve Phase
Intended learning outcomes: Produce an overview on tools of the jidoka concept, such as Andon (or a visual control system in a job shop) and Poke yoke (or fail-safe techniques).
18.2.6 Quality Assurance: PDCA Check Phase, Part 2 — DMAIC Measure Phase and Analyze Phase, Part 2
Intended learning outcomes: Identify changing definitions of terms over time in quality assurance and quality management.
18.2.7 PDCA Activation Phase — DMAIC Control Phase
Intended learning outcomes: Produce an overview on tools used in quality activation. Identify deliverables of the Control phase.
18.2.8 Project Management, Continual Improvement, and Reengineering
Intended learning outcomes: Differentiate between continual process improvement and (business) process reengineering.
