rare in practice. Only 100% inspection can hope to detect these types of errors, and even 100% inspection is not 100% accurate, so errors can still be unde- tected. An engaged and empowered work force is perhaps the best prevention.
Implementation and Verification
Once the improvement methodology and new process levels have been de- termined, they can be implemented. Even in the simplest of improvements, caution and diligence must be exercised at this point.
One of the most obvious, yet still overlooked, reasons for problems at this point is due to lack of communication. Previous chapters have discussed the need for regular updates with the stakeholder groups to avoid surprises at the improve stage. These updates allow the vision of the solution to be formed over time by the stakeholders, increasing the likelihood of buy-in to the so- lution. Through proper communication, stakeholders will understand the need for a solution in the define stage, appreciate the extent of the problem in the measure stage, and realize its complexity through the analyze stage.
Exercising rigor during the improve stage brings clarity to the solution for each of the stakeholder groups.
Nonetheless, even when the solution is evident, the project team must focus on proper communication to ensure support through the implementation of the solution. Starting with the project sponsor, each step of the solution, with a contingency plan in the event of failure, must be presented in a clear and orderly fashion to the stakeholder groups. The sponsor must convey the specific authority to the project team, properly communicated through the organizational hierarchy, to implement the specific solution beginning at a specific date and time. Process personnel, and their immediate management, must be cognizant of the authority vested in the project team in implement- ing the solution, and provide the necessary support to ensure its proper implementation.
The process personnel must be provided with clear instructions on their new procedures, especially with regard to process failures. While the control stage includes detailed training on the new process procedures, at this point the procedures may still be somewhat in flux until the solution has been deployed.
Depending on the extent of the solution, in-depth training of all personnel could be premature until the process and its procedures have been stabilized. This state of transition requires oversight by the project team and/or process per- sonnel (under the direction of the team) to ensure the process output meets the expectations of the authorized solution. The goal is to quickly establish the
merits of the solution so that the project team can move to the control stage, where in-depth training can be conducted. Until this training takes place, the project team must work closely with process personnel to communicate proper action and understanding of the process conditions.
Statistical analysis of these conditions, generally using control charts, is needed to verify the results. As discussed in Chapter 8, statistical control of the process is necessary if project success is to be measured. Hypothesis tests on the difference in means may be used to compare the process before and after implementation of the solution.
Recommended Tools
The following tools (discussed in detail in Part 3) are applicable to the improve stage of DMAIC:
Determine Operating Conditions
Activity network diagramsand PERT analysisto verify the reduction in process critical path cycle time.
Five S toolsto reduce non-value-added cycle times due to movement, search time, ineffective use of floor space; to improve inventory management; or to reduce accidents and improve working conditions.
Level loadingto balance the flow of orders.
Matrix diagramsandprioritization matricesto ensure that process solutions are aligned with customer needs.
Box-whisker chartsto graphically compare before and after states of process improvement.
Cause and effect diagramto generate a list of potential failure modes that should be addressed in the solution.
Designed experiments, regression analysis, residuals analysis, response surface analysis, ridge analysis, factorial designs, evolutionary operations, interaction plots, andcontour plots to determine where a maximum or minimum response is expected within or close to the data range.
Investigate Failure Modes
Procession decision program chartsandfailure modes and effects analysis to determine high-risk process activities or product features in the proposed improvement.
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Implement Improvement
Flowchartsandprocess mapsto define the process level activities necessary.
Hypothesis testing of two samplesand nonparametric test on the equality of meansto compare process averages after improvements versus baseline estimates.
SPC control charts, includingC,Np,P, U, Individual-X,X-Bar, and EWMA charts, andprocess capability indexto verify the effects of the improvement.
Goodness of fit testsandnormal probability plotsto verify the statistical distributions assumed in the various statistical tools.
In addition, the consensus building tools noted at the end of Chapter 4 are also applied, as needed.
Quiz for Chapter 7
1. A process decision program chart is useful to:
a. Identify problems in implementing a project solution.
b. Define the tasks required to complete a project.
c. Develop contingency plans for problems.
d. All of the above.
2. Of the following three types of controls, which is the most desirable?
a. Those that prevent the cause or failure mode from occurring or reduce their occurrence.
b. Those that detect the cause and lead to corrective action.
c. Those that detect the failure mode.
d. These are not design controls.
3. A reduction in the occurrence ranking in an FMEA can be achieved by:
a. Removing or controlling one or more of the failure mode causes through a design change.
b. An increase in design validation/verification actions.
c. All of the above.
d. None of the above.
4. In a process FMEA, process and/or design changes can:
a. Reduce the probability of occurrence.
b. Reduce the severity ranking.
c. Increase the probability of detection.
d. All of the above.
5. With regard to the detection of process errors:
a. 100% inspection is a preferred approach.
b. SPC will detect all errors that can occur.
c. A picture or graphic of the known defects is helpful to guide process operators.
d. It is not necessary to develop detection plans once you achieve high sigma levels.
6. We might choose to simulate a process:
a. When the cost of experimentation is high.
b. To test a wide variety of conditions.
c. To generate data useful for training.
d. All of the above.
7. A necessary prerequisite for simulation includes:
a. Reasonable estimates of the process model and its operating conditions.
b. A computer capable of running millions of calculations.
c. Training on the derivation of stochastic models.
d. All of the above.
8. Simulation results:
a. Are usually not useful in preventing errors, but often useful to predict errors.
b. Can be more exact than process data when real distributions are modeled.
c. Should be verified using process data.
d. All of the above.
9. A process critical to daily operations is in need of improvement, but management is not willing to shut the process down for investigation.
A reasonable method of gaining process improvement is through:
a. A Taguchi experiment.
b. A classical designed experiment.
c. Evolutionary operation.
d. One factor at a time experimentation.
10. The powerof an experiment refers to:
a. The statistical significance of the effects.
b. The ability to detect that an effect is significant.
c. The ability to reject the alternative hypothesis when it is false.
d. All of the above.
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Control Stage
The final stage of the DMAIC process improvement methodology is the control stage.
Objectives
There are several objectives to be completed within the control stage of DMAIC:
The new methods must become standardized in practice.
The predicted impact of the improvements, the project deliverables, must be continually verified, especially the financial return.
Lessons learned should be documented.
Standardize on the New Methods
In the improve stage, changes are made to the process. Many times, the process procedures will be changed. The old way of doing things is replaced with new and improved methods.
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Process variation may have been reduced by controlling the variation in one or more key input variables, or by redefining more appropriate levels for these parameters. These changes may result in the need for more manpower available at certain times of the day or for control of the variation in key parameters, such as room temperature, to control the size of a key dimension.
The natural response of process personnel may be to gradually, or even abruptly, return to past practices. This may occur the first time the process experiences a shift in behavior, when personnel return from vacation and fall into old habits, or when you’re just not looking.
There are several practices useful for standardizing on the new process methods: