Chapter 8. Quality Maintenance. Part 2

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5.10 Step 10 Revise Standards

We have now established certain conditions relating to the causes of defects, which, if adhered to, will ensure perfect quality. The next thing we must do is to perform the required checks reliably, at pre-set intervals and using the specified methods, to ensure that these conditions are maintained. We must also monitor trends in the conditions over time. To establish a condition monitoring system of this kind, we must ensure that operators and maintenance personnel understand the need for the checks, the methods to be used, and so on, and coach them on incorporating this information into their standards and manuals, following the steps illustrated in Figure 8.13

Figures 8.14 shows an example of how the Quality Check matrix can be integrated into standards.

Figure 8.13 Standardisation

Figure 8.14 Example of Work Standard

In addition, by examining the items to be checked and the standard values for individual items of equipment, we can identify any components that will inevitably produce a quality defect if they deviate from the standards. Such components are called Q Components (Quality Components). To make sure that these components are a maintenance priority, we can draw up Q Component Tables and display them on the relevant parts of the equipment. We can achieve zero defects by strictly observing the relevant standards and continually monitoring the trends in these components.

Figure 8.15 shows an example of a Q Component Table for one piece of equipment. Another good idea is to create a maintenance calendar based on cards (see Photo 8.1), to ensure that regular Autonomous Maintenance checks are carried out.

Figure 8.15 Example of Q Component Table

Photo 8.1 Example of Autonomous Maintenance Calendar

 

 

5.11 Results

Perfect, right-first-time quality has been achieved in numerous cases through the painstaking application of Quality Maintenance to model products on model lines or machines, followed by rollout to other areas. This also leads to reduced inspection labour-hours and fewer complaints. Figure 8.16 shows an example of the positive results that can be achieved.

Figure 8.16 The Results of One Company’s Quality Maintenance Programme

6. The Figure-of-Eight Method for Quality Maintenance

6.1 The History of Quality Maintenance and the Emergence of the Figure-of-Eight Method

Many Japanese companies started building Quality Maintenance systems in the early 1980s. As these companies strove to improve the quality of their products through Quality Maintenance, they came to see that it consists of two principal activities, quality sustainment, and quality improvement. By the mid-1990s, a large number of them had arrived at an approach consisting of the following 7 steps:

(1) Identify Existing Situation

(2) Eliminate deficiencies

(3) Analyse Causes

(4) Eradicate Causes

(5) Establish Conditions

(6) Improve Conditions

(7) Maintain Conditions

The Figure-of-Eight method aims to establish a system that builds in quality by means of the process, from the twin perspectives of sustainment and improvement. It should therefore only be started after the 10-step Quality Maintenance procedure has been completed at least once. The Figure-of-Eight Method includes the QM matrix but not the QA matrix, because it assumes the latter has already been compiled.

Table 8.8 The Evolution of Quality Maintenance

6.2 The Figure-of-Eight Method : Basic Concepts and Development Steps

Many different companies have adopted the Figure-of-Eight method over recent years. It is based on the 7 steps noted above, distributed around two interconnecting loops (a ‘sustainment’ loop on the left and an ‘improvement’ loop on the right), and it seeks to improve the level of both these activities in a never-ending upward cycle. Figure 8.17 illustrates the basic concepts and the steps to be followed.

Figure 8.17 Overview of the Figure-of-Eight Method for Quality Maintenance

Only by fully understanding the aim of each step can we create a reliable, robust system for building quality into the product. The steps and their objectives are described below.

(1) Step 1 : Identify Existing Situation

In the Figure of Eight method, ‘identify existing situation’ has a slightly different meaning to the usual. The difference is that, as well as investigating the quality situation and identifying current rules and procedures, it is also necessary to assess how strictly they are being complied with.

1 Investigate quality situation

The current quality situation is identified by finding out what quality characteristics must be maintained in each work area or process, together with their standard values.

2 Identify rules and procedures

Here, we examine QC process charts, work standards, processing condition tables, etc., to find out all the rules and procedures that are currently seen as necessary in each work area or process for building quality into the product.

3 Assess compliance
Next, we examine the extent to which these rules and procedures are being observed.

By carrying out these three sub-steps, we can summarise the existing quality situation in the form of a QM Matrix (or Quality Assurance Level Evaluation Table) for each work area.

(2) Step 2 : Restore

Any deficiencies discovered in Step 1 are now addressed, with the aim of restoring the situation to what it should be. The results are then checked and evaluated, to indicate what to do next.

1 Restore to current optimal state

If we find in Step 1 that any of the existing rules or procedures are not being observed, then we must ensure that they are, in order to restore the situation to what it should currently be.

2 Check results

Next, we check the results obtained by restoring the current optimal state.
The key point in Step 2 is to determine what to do next, by checking the results (see Figure 8.18). The action required will be one of the following three types:

Type I : If satisfactory results are not achieved by restoring the current situation, then we move on to Step 3 in the Improvement loop, where we examine the conditions and reassess the standard values to find out where our current rules and procedures are incomplete or insufficiently rigorous.

Type II : If the results are good, we advance to Step 6, where we revise our sustainment systems.

Type III : If the results are better than before but still do not clear our targets, then as well as moving to Step 6 to maintain the results achieved so far, we also advance to Step 3 to rise to our targeted level.

Figure 8.18 Actions Taken After Checking Results

(3) Step 3 : Analyse Causes

If we have still not got the results we are looking for, even after ensuring that all the current rules and procedures are being observed, this means that either the rules and procedures are incomplete or the standards are too lenient. We must therefore analyse the causes of poor quality in order to determine exactly what standards we do need.

Analyse causes
When analysing causes, it is important to get back to basics and clarify the exact phenomena that occur, expressing these phenomena as deviations in physical quantities, based on an accurate understanding of the principles and parameters involved. We must then identify possible causes of these deviations by taking account of the processing mechanisms and the functions and structure of the equipment used. P-M Analysis is an extremely powerful tool for doing this.

Revise standard values
When revising the standard values, we need to check how ‘robust’ they are. Many firms have recently introduced Quality Engineering (Taguchi Methods) to help them with this.

(4) Step 4 : Eradicate Causes

Here, we carry out three sub-steps based on the analysis of causes carried out in Step 3.

Investigate causes
Using Quality Engineering, optimal conditions must be determined for all the possible causes of poor quality identified by P-M Analysis. In other words, we must identify what necessary conditions were missing from the existing system, and which of the existing standards were too lenient.

Restore and improve
Next, we add any missing conditions, revise any insufficiently robust standards, and make improvements where necessary. It is important to devise improvements that are easy to maintain, in order to facilitate the sustainment activities carried out later on.

Check results
We then devise quick methods for evaluating the results of our improvements. When we have confirmed that the results are satisfactory, we can move on to the next step (Step 5).

(5) Step 5 : Establish Conditions

If we have obtained satisfactory results, we establish exactly what is required to maintain this state. The key to this is revising the QM matrix.

Revise QM matrix
First of all, we take the provisional QM matrix created in Step 1 and amend it in the light of all the items highlighted by our P-M Analysis and Quality Engineering studies. This involves revising standard values, adding or removing certain items, altering methods, and so on.

Revise standards
It is important that each revision made to a standard is referenced clearly to a technical report, improvement report, or other such document, so that everyone understands the reasons for the revision.

(6) Step 6 : Improve Conditions

Having resolved the defect phenomena by restoring the situation in Step 2, it is vital to think hard about why the conditions were not observed, and how we can adapt our methods of sustainment to ensure that they are. The ideal situation may be hard to maintain, or it may be hard to notice when conditions have slipped.

When we look at what actually happens on the factory floor, it is more usual that workers are not able to observe the conditions, rather than that they do not want to observe them. So, in order to achieve a reliable sustainment system, it is essential to make the conditions easy to comply with. To do this, we must come up with ideas for reducing the number of different actions required and making it possible to perform them quicker and less often.

(7) Step 7 : Maintain Conditions

One possible reason for not sustaining the required conditions is failure to notice when this is happening. This requires us to do two things:

Revise checksheets
If we want to make sure that what ought to be done is actually being done, and done reliably, by the people who ought to do it, then it is crucial to establish a checking system for confirming that each worker and manager is fulfilling his or her responsibilities.

Monitor trends
Any conditions that tend to deteriorate should be extracted from the QM matrix and monitored on charts to predict the occurrence of defects.

Having dealt with the first problem by completing one cycle of the Figure-of-Eight, we now need to move on to the next problem and make a second trip, starting again from Step 1, while sustaining the solution we have installed for the first problem. By continually repeating this cycle of sustainment and improvement, we can progressively improve our workplaces’ capacity to build in quality, which is in fact the aim of the Figure-of-Eight method for Quality Maintenance.

Figure 8.19 shows a general view of how Quality Maintenance can be developed using the Figure-of-Eight method

7. Quality Maintenance in a Manual Operation

This section describes what must be done to develop Quality Maintenance in processes where quality is built into the product by manual work, as opposed to processes where machines are the major determinant of product quality. This approach uses Process Quality Assurance Rate Evaluation Tables, rather than the QM Matrix. It also uses the Figure-of- Eight Method from the start, without first applying the 10-Step Procedure.

7.1 Step 1 : Identify Existing Situation (Clarify Quality Characteristics and Work Conditions)

In this step, we identify the quality characteristics that are to be built into the product during the process, along with the work conditions that must be fulfilled to achieve this quality. This gives us the framework of the Process Quality Assurance Rate Evaluation Table, and puts us in a position to assess the assurance rate. It involves the following sub-steps:

(1) Clarify the quality characteristics

(2) Investigate the situation of in-process defects and passed-on defects

(3) Identify the work conditions for each process

(4) Create a Process QA Rate Evaluation Table

7.2 Step 2 : Restore (Assess Control Level and QA Level, and Calculate Process QA Rate)

Here, we assess the control level for each work condition, and find the current QA rate for the process. This involves:

(1) Evaluating the control level for each work condition (see Table 8.9)

(2) Evaluating the QA level for each quality characteristic

(3) Calculating the QA rate for the process

Table 8.9 Standards for Evaluating Level of Control of Rules and Procedures

7.3 Step 3 : Analyse Causes (Investigate Relationship between QA Level and Defects (In-Process Defects and Passed-On Defects)

This requires us to look for cause–effect relationships between the defect situations examined in Step 1, and the QA levels identified in Step 2. If we can find what causes lead to what effects, then we can move on to the next step and improve the QA level. But if these relationships are not clear, then we must go back and re-evaluate the control levels for each work condition.

7.4 Step 4 : Eradicate Causes (Establish Improvement Targets)

Improvement topics are listed in order of importance, starting from the control levels that currently show the greatest degree of error. From experience, the target QA rate should be set to 80% or above.

7.5 Step 5 : Establish Conditions (Propose Improvements and Implement)

When proposing improvements, it is important that we start by searching for ideas at control level A, rather than just being content to find easy solutions at level B. Although it may be possible to reach level A by applying a combination of different ideas, we must first try to find one-shot solutions.

(1) Think of ways to prevent defects occurring before ways to prevent passing them on. (2) Think of single solutions to assure quality before applying combinations of solutions.

7.6 Step 6 : Improve Conditions (Check Results and Evaluate)

Check the results to ensure that the improved control levels are translating into fewer defects.

7.7 Step 7 : Maintain Conditions (Consolidate Gains and Sustain)

If the results are favourable, then we must find ways of locking down the situation so that the improved work conditions are maintained, and we must sustain these improvements consistently.

Figure 8.20 gives an outline of how Quality Maintenance can be developed through the use of Process Quality Assurance Rate Evaluation Tables.

Figure 8.20 Procedure for Developing Quality Maintenance in Manual Work Processes

Chapter 8. Quality Maintenance. Part 3
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