【正文】 answers tp the first two. ? What is the working environment? Do you have unlimited access to the process to be able to change settings (production line Vs pilot plant access to experimentation)? How many runs can you afford in terms of time and money? Is cost a limiting issue? Will experimental results apply directly to the process or will they need verification? These are key concepts because you want to minimize the cost of obtaining information. ? What is your knowledge of the process? What do you know about important factors and how they work together (interactions)? How close to optimum are you currently running? What is the operating range of each factor? Once you define your goal, your environment and your knowledge, you can choose an adequate experimental design. Four questions to determine the type of design EN/FAD 109 0015 169。EN/FAD 109 0015 169。 Ola Johansson, 1999 Ericsson Quality Management Institute DOE Objectives ? To determine those variables / predictors (time, temperature etc) that are most influential on the response ? To assess the best settings / levels of those significant variables that result in a response near a desired value maximum / minimum / nominal. ? To assess the best settings / levels of those significant variables that miminise variability in the response. ? To assess the best settings / levels of those significant variables that reduce the effect / impact of ?noise? nuisance variables EN/FAD 109 0015 169。 Ola Johansson, 1999 Ericsson Quality Management Institute DOE The Benefits ? Far fewer trials than conventional approach ? Identifies those process parameters that affect output quality ? Reduce process / product variability ? Enables output quality average to be closer to target ? Minimise the effects of ?noise? ? Enable products to be developed that seldom fail ? Reduce product development lead time ? Reducing time and cost to mission new plant and equipment EN/FAD 109 0015 169。 Conduct Trials Analyse amp。 Ola Johansson, 1999 Ericsson Quality Management Institute ? Define the problem a clear statement of the problem to be solved involving all appropriate people who can contribute ? Determine the objective identify the output quality characteristics(dependent response variables) define the measurement system ? Identify key parameters for design brainstorm all independent variables categorise (control / constant / nuisance) and prioritise assess for interaction effects ? Select parameters agree number variables and their values ? Design the experimental array select the best (least trials) orthogonal array(s) for independent variables assign variables (and interactions) to array columns ? Plan the experiment establish plans for process stability and taking measurement answer questions。 Ola Johansson, 1999 Ericsson Quality Management Institute A Two Level Factorial Design ? Effect of pressure is difference in mean response between runs where it is at plus (high) level and minus (low) level ? Effect is units but do not know if this is significant ? Analysing the design calculating the “effect” of changing the factors : level minus (low) to level plus (high) Std Order 1 2 3 4 5 6 7 8 Run Order 4 7 3 1 5 8 6 2 Pressure 55 70+ 55 70+ 55 70+ 55 70+ Heat Med Med High + High + Med Med High + High + Time 6 6 6 6 8+ 8+ 8+ 8+ Response