Quality Control for PH of Tea
Final Presentation
YU Jiayi, CUI Liwen, CHEN Rui, GUO Dingcheng, CAO Qing
1
Project Overview
Suggestions
PH value
Control
DOE
Define
Improve
Measure
Gage R&R
Analyze
Off-line Experiments
2
Project Overview
Control
Define
Improve
Measure
Analyze
3
Define (1/3)
• Study Problem
– As the PH value of tea beverage is an important
quality index, we would like to study the factors
that would affect the PH value through off-line
experiments.
– We expect to obtain the recommended values of
the related influence factors to obtain the
recommended PH value, thus guiding the real
production of tea beverage.
4
Define (2/3)
• Response (y)
– PH value of tea beverage
• Green Tea: PH value of 6.2 recommended
• Factors (x)
– Temperature
– Time
– Percentage of Tea
– Container (stainless steel, glass, ceramic, etc.)
5
Define (3/3)
• Methodology: Design of Experiment
– Off-line experiments
– Gage R&R study
– GLM
• Identify significant factors
• Specify relationships between x and y
6
Project Overview
Control
Define
Improve
Measure
Analyze
7
Measurement Instruments
Temperature-control Pot
Measuring Cup
Electronic PH-meter
Electronic Scale
8
Gage R&R (1/6)
• Experiment setting
– pH meter
– 3 operators
– 3 cups of tea
– 3 replicates
– Parameters
• 3g tea
• 200 mL water
• 8 min
9
Gage R&R (2/6)
• Experiment without SOP
– Effect of operator is significant
– Contributions of total Gage R&R: nearly 100%
• Repeatability: 62.57%
• Reproducibility: 37.43%
Source
Part
Operator
Part*operator
Repeatability
Total
DOF
2
2
4
18
26
SS
0.01982
1.01682
0.02482
1.7272
2.78867
MS
0.009911
0.508411
0.006206
0.095956
F
1.5971
81.9284
0.0647
P
0.309
0.001
0.992
10
Gage R&R (3/6)
• Experiment without SOP
11
Gage R&R (4/6)
• Experiment with SOP
– Effect of part and interaction are significant
– Contributions of total Gage R&R: 35.21%
• Repeatability: 14.72%
• Reproducibility: 20.49%
Source
Part
Operator
Part*operator
Repeatability
Total
DOF
2
2
4
18
26
SS
MS
0.005341 0.00267
0.001252 0.000626
0.000704 0.000176
0.001133 0.000063
0.00843
F
15.1789
3.5579
2.7941
P
0.014
0.129
0.058
12
Gage R&R (5/6)
• Experiment with SOP
13
Gage R&R (6/6)
• The gage has acceptable repeatability and
reproducibility
– Different operations of operators have large
influence in R&R
– A proper SOP is required to improve the
performance of operators
14
Project Overview
Control
Define
Improve
Measure
Analyze
15
Design of Experiment (1/2)
•
•
•
•
34−1 fractional factorial design
Response variable: pH value (using pH meter)
Tea: 憩园甘露
Initial model:
– 𝑦 = 𝜇 + 𝐴 + 𝐵 + 𝐶 + 𝐷 + 𝐴𝐵 + 𝐴𝐶 + 𝐵𝐶 + 𝜖
Factor
Level
A
Temperature (C)
60
80
98
B
Time (min)
2
5
8
C
Volume of water (ml)
50
100
200
D
Material of cup
Glass
Ceramic
Stainless steel
16
Design of Experiment (2/2)
• Sequence of experiment
– Three cups of tea are tested in the same period.
– The cups are made of different materials.
– The total time of each cup is different.
– Measure their PH at their own time point.
• Control of factors
– Temperature: air-conditioner, thermos
– Volume of water: measuring glass
– Weight of tea: electronic balance
17
Design of Experiment
0 min
2 min
4 min
不锈钢
陶瓷
玻璃
8 min
7 min
6 min
8-0=8 min
7-2=5 min
6-4=2 min
18
Experiment process (1/4)
• Experiment notes
– Cleaning acidometer & container everytime after
reading PH value to get accurate data
– Put acidometer into tea at least 1 min before
reading to get stable PH value
– To save time, we compress 3 experiments into one
8 min cycle, with same water temperature
19
Experiment process (2/4)
• Preparation
– Make sure the 3 experiments’ parameter
combination (3g tea-leaf, same temperature)
• 2min, A mL water, B1 container
• 5min, A mL water, B2 container
• 8min, A mL water, B3 container
– Measuring required water & three 3g tea-leaf
– Put tea-leaf into 3 container
20
Experiment process (3/4)
• Experiment cycle
Pour A mL
water into
B3 container
0 min
Pour A mL
water into
B2 container
1 min
Measuring
A mL water
2 min
•
Pour A mL
water into B1
container
• Wash acidometer
3 min
Measuring
A mL water
4 min
•
•
•
Read PH value
•
Wash acidometer
•
Put acidometer
•
into B2 container
• Wash B3 container
5 min
6 min
•
•
Put acidometer
•
into B1 container •
7 min
Read PH value
Wash acidometer
Wash B1 container
8 min
Read PH value
Wash acidometer
Put acidometer into B1 container
Wash B2 container
8 min
5 min
2 min
21
Experiment process (4/4)
Measure 3g tea
All experiment instruments
Experime
nt
Snapshot
s
Read PH value
3 cups per cycle
22
Design of Experiment (1/9)
• Result of the initial model
– All main effects are significant
– Three interactions are not significant
Source
Temperature
Time
Volume
Material
Temperature*Time
Temperature*Volume
Time*Volume
Residual
Total
DOF
Adj MS
0.055144
0.149344
0.438611
0.048678
F
10.48
28.38
83.34
9.25
P
0.011
0.001
<0.001
0.015
4 0.019822 0.019822 0.004956
0.94
0.5
0.9
0.73
0.52
0.602
2
2
2
2
4
4
6
26
Seq SS
0.110289
0.298689
0.877222
0.097356
Adj SS
0.110289
0.298689
0.877222
0.097356
0.018889 0.018889 0.004722
0.015422 0.015422 0.003856
0.031578 0.031578 0.005263
1.469267
23
Design of Experiment (2/9)
• Residual plot
24
Design of Experiment (3/9)
• Mean of main effect
25
Design of Experiment (4/9)
• Interaction
26
Design of Experiment (5/9)
• Result of model without interaction
–𝑦 =𝜇+𝐴+𝐵+𝐶+𝐷+𝜖
Source
DOF
Seq SS
Adj SS Adj MS
F
P
0.001
Temperature
2 0.11029 0.11029 0.05514
11.58
Time
2 0.29869 0.29869 0.14934
31.36 <0.001
Volume
2 0.87722 0.87722 0.43861
92.11 <0.001
Material
2 0.09736 0.09736 0.04868
10.22
Residual
18 0.08571 0.08571 0.00476
Total
26 1.46927
0.001
27
Design of Experiment (6/9)
• Residual plot
28
Design of Experiment (7/9)
• Mean of main effect
29
Design of Experiment (8/9)
• Residual vs. sequence
30
Design of Experiment (9/9)
• Recommended parameter
– Time: 2min
– Volume of water: 200ml
– Material of cup: Ceramic
– Temperature: 98C
– Estimated pH: 6.231
• Limitation: no consideration on the effect of
– Reusing tea
– Type of tea
31
Project Overview
Control
Define
Improve
Measure
Analyze
32
Improve & Control
• Improvements can be made to the production
line to obtain a recommended PH value
– Temperature: 98 ℃ recommended
– Time: 2 minutes
– Tea/water ratio: 3g tea/200 ml water
recommended
– Container: change the original stainless steel
container to the porcelain container
33
Thanks
2014/06/13
34