DOE

Question 1

What are the objectives of DOE? (5)

Answer 1

1) Identify the cause of variation in critical products or processes parameters
2) Limits the effect of the variation identified
3) Achieve reproducibility of best system performance in manufacturing
4) Assist in optimising a product or process
5) Reduce cost

Question 2

What are the four methods covered in DOE? Explain each

Answer 2

Trail and error: change variable until something works. No direction and focus

Single factor experiment: change one variable at a time. consuming and slow. Interaction cannot be detected.

Fractional factorial experiment: only select a number of factors and adjust simultaneously. reducing the total number of experiment whole allowing complex interactions

Full factorial experiment: examine every possible combination of factors at all levels. time consuming but complete.

Question 3

What is the Taguchi method?

Answer 3

This Taguchi method tests pairs of combinations, selected using Taguchi
arrays. These can be derived using deterministic algorithms but generally can be found online
or in textbooks. The arrays are selected by the number of factors (variables) and the
number of levels to be tested

Question 4

The systematic application of DOE should be based on three distinct phases, what are they?

Answer 4

Phase 1 – Preparation: this is often referred to as the pre-experimental stage. Experiments
can take considerable time and resources, and good preparation is all-important.

• Define the problem to be solved.
• Agree the objectives and prepare a project plan.
• Obtain and study all available data related to the problem.
• Define what needs to be measured to satisfy the project objectives.
• Identify the factors to be controlled during the experiment
• Establish an effective measuring system.

Phase 2 - Experimentation and analysis: carrying out the planned trials:

• Select the techniques to be used.
• Plan the trials. Consecutive trials should not affect each other.
• Conduct the trials as planned. Results should be carefully recorded in a table
• Analysis and reporting of results.

Phase 3 – Implementation: communicating the lessons learnt by:

• Applying the findings to resolve the problem.
• Adopting a procedure for measuring and monitoring results such as statistical
process control (SPC) to detect any future changes that could influence quality.
• Communicating lessons learnt through business and included in training