04-07-2012, 04:31 PM
Robust Design: Experiments for Better Products
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Goals for Designed Experiments
Understanding relationships between design parameters and product performance
•Understanding effects of noise factors
•Reducing product or process variations
Brownie Mix
•Controllable Input Parameters
–Recipe Ingredients (quantity of eggs, flour, chocolate)
–Recipe Directions (mixing, baking, cooling)
–Equipment (bowls, pans, oven)
•Uncontrollable Noise Factors
–Quality of Ingredients (size of eggs, type of oil)
–Following Directions (stirring time, measuring)
–Equipment Variations (pan shape, oven temp)
•Measurable Performance Response
–Taste Testing by Customers
–Sweetness, Moisture, Density
Plan the Experiment
Step 3: Plan experimental runs to elicit desired effects.
•Use full or fractional factorialdesigns to identify interactions.
•Use an orthogonal arrayto identify main effects with minimum of trials.
•Use inner and outer arraysto see the effects of noise factors.
Key Concepts of Robust Design
Variation causes quality loss
•Two-step optimization
•Matrix experiments (orthogonal arrays)
•Inducing noise (outer array or repetition)
•Data analysis and prediction
•Interactions and confirmation