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Robust Design Robust Design StrategiesStrategies

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Pertemuan ke-820 November 2014

Dr. Eko Pujiyanto, S.Si., M.T.

Jurusan Teknik Industri - Universitas Sebelas Maret

Ambitious Business GoalsAmbitious Business Goals

Make product robust (rugged, insensitive) such that they work, all the time, the way that they are supposed to.


Try to achieve:� Consistent performance� Robust design � Performance that is unaffected by

influence of uncontrollable factors.



� Why does the performance vary?Noise factors

� How do we minimize the influence of noise factors?


noise factors?Not by controlling them, but by adjusting The Controllable Factors

� What is the design strategy:– Robust design strategy– Outer array design with noise factors



� Why do we need to repeat experiments(trials)When performance varies, we need to test more samples to get a representative performance reading.


performance reading.

� What is the purpose?Our purpose is to reduce variation of performance around the target.


What causes variations?What causes variations?� Variation in performance is caused by factors

we cannot control, do not want to control or are not aware of their influence (Noise Factors)

� What do we want to do about the influence


� What do we want to do about the influence of the noise factors? Contrary to the traditional approach to determine the causes of variation and try to control them, in ROBUST DESIGN strategy, the approach is to reduce the influence of the noise factors by simply controlling the controllable factors.


What can you do to reduce the influence of the noise factors? What can you do to reduce the influence of the noise factors?

� Design experiments with controllable factors as usual.

� Identify the applicable noise factors for the subject project and determine their


the subject project and determine their combinations by using the appropriate orthogonal array.

� Repeat the trial conditions by exposing them to the influence of the noise factors.


What can you do to reduce the influence of the noise factors? What can you do to reduce the influence of the noise factors?

© 2004 By Default!A Free sample background from www.awesomebackgrounds.com Jurusan Teknik Industri - Universitas Sebelas Maret

Robust Design StrategyRobust Design Strategy

1. Identify noise factors2. Control them during tests in laboratory

environment and work with at least two levels.

3. Combine the noise factors using the


3. Combine the noise factors using the orthogonal array (outer array) to produce a number of noise conditions.

4. Repeat samples in the same trial conditions exposing each to the noise conditions.


Robust Design StrategyRobust Design StrategyExample 1 :� Consider that we have three 2-level noise factors

in the experiment with the cake baking process.� Noise Factors:

– Oven type (N1)– Humidity (N2)– Room temperature (N3)

These 3 noise factors, at 2-level each, can be


� These 3 noise factors, at 2-level each, can be combined to produce 8 conditions.

� Alternatively we can use Taguchi L4 OA to produce 4 conditions.

� Objectives:Determine the optimum condition by selecting the controllable factor levels such that variations due to uncontrollable factors is minimized.



Mechanics of the Outer Array Designs



Advantages: � Information about noise factors� Interaction between control and noise factors� Number repetitions� Noise conditions


� Disadvantages: � Higher level of disciplines� Costlier



Benefits of Outer Array designs� Optimum condition determined using outer

array is least sensitive to the variation of noise factors. (robust design)

� Number repetition and the conditions of the noise factor levels are discretely determined


noise factor levels are discretely determined by the size of the outer array.

� Influence of noise factor can be easily calculated in the same manner as control factors (main effect of noise factors).

� Interaction between control factors and noise factors can also be determined if desired.



Example 2 : Robust Bearing Design StudyDesigns factors and their levels : 4 factors at 2-levels each , 3 interactions and 3 noise factors at 2-levels each


Robust Design StrategyRobust Design StrategyExample 3 : Proses dan produk injection molding

Kode Faktor Terkontrol Level

A Waktu pendinginan 2

B Temperatur nozzle 2

C Kecepatan injeksi 2

D Tekanan penahan 2


E Tekanan injeksi 2

F Temperatur zone - 2 2

G Waktu penahan 2

Kode Faktor Tidak Terkontrol ( Noise ) Level

M Persen runner 2

N Kandungan uap air 2

O Temperatur lingkungan 2

Robust Design StrategyRobust Design StrategyExample 3 : Proses dan produk injection molding


Robust Design StrategyRobust Design StrategyExample 3 : Proses dan produk injection moldingRencana Eksperimen


Robust Design StrategyRobust Design StrategyExample 3 : Proses dan produk injection moldingHasil Eksperimen


Robust Design StrategyRobust Design StrategyExample 3 : Proses dan produk injection moldingAplikasi Metode Taguchi1. Rata-rata


Robust Design StrategyRobust Design StrategyExample 3 : Proses dan produk injection molding1. Rata-rata


Robust Design StrategyRobust Design StrategyExample 3 : Proses dan produk injection molding2. Variansi


Robust Design StrategyRobust Design StrategyExample 3 : Proses dan produk injection moldingMenentukan level terbaik


Robust Design StrategyRobust Design StrategyExample 3 : Proses dan produk injection moldingMenentukan level terbaik

Kode Faktor Terkontrol Rata-rata Variansi

A Waktu pendinginan 1 1

B Temperatur nozzle -1 1


C Kecepatan injeksi 1 1

D Tekanan penahan -1 1

E Tekanan injeksi 1 1

F Temperatur zone - 2 - -1

G Waktu penahan -1 1

Robust Design StrategyRobust Design StrategyExample 3 : Proses dan produk injection moldingPrediksi rata-rata


Robust Design StrategyRobust Design StrategyExample 3 : Proses dan produk injection moldingPrediksi variansi


Robust Design StrategyRobust Design StrategyExample 3 : Proses dan produk injection moldingPerbandingan Taguchi dan Metode Pledger


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