Six Sigma Case Study 1 -MFI
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Transcript of Six Sigma Case Study 1 -MFI
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1.0 Objective :
To determine the effect of critical injection parameters on MFI
(Degradation %).
2.0 Machine/ Material:
Machine : 7E3, Screw diameter : 22mm
Resin : Cycoloy C1100HF
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3.0 Experiment Flow
Molding D.O.E
Melt Flow
Index Test
• Use Cutter to cut part
• Study effect of
parameters on MFI
• Study effect of six critical
molding parameters
Trial sample
preparation
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Melt Flow Rate : Introduction
One of the most common causes of plastic part failure is
polymer degradation during melt processing.
In most materials, this degradation results in a reduction in the
average molecular weight of the polymer.
This reduction is readily measured by a variety of techniques,
the simplest being the melt flow rate test. - Michael Sepe
Simple Interpretation :
Melt flow Rate/ index is an inverse measure of molecular weight.
When polymer encountered degradation, average molecular
weight will reduce and MFR value will high.
- Shan, Handbook of
Plastic Technology
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1. Injection Speed : 20 - 40
2. Injection Pressure : 50 - 100
3. Holding Pressure : 10 - 30
4. Hot runner temperature : 240 – 2600C
5. Meld Temperature : 240 – 2600C
6. Mold Temperature : 70 – 900C
Responses : MFI Degradation %
MFI Degradation % = (MFI – MFI resin) / MFI resin
4.0 Design Of Experiment
(DOE : ¼ Fractional Factorial 26, Resolution IV )
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4.1 DOE Matrix and Result :
Factional Factorial 26 (R IV)
Response
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Inj press
Inj Sped
Mold temp
Hold press
Melt temp
Hot runner
43210
Term
Standardized Effect
2.262
Pareto Chart of the Standardized Effects(response is Degrad. %, Alpha = .05)
Factorial Fit: Degrad. % versus Inj Sped, Hot runner, ...
Estimated Effects and Coefficients for Degrad. %
Term Effect Coef SE Coef T P
Constant 26.726 0.7905 33.81 0.000
Inj Sped 0.834 0.417 0.7905 0.53 0.611
Hot runner 6.114 3.057 0.7905 3.87 0.004
Melt temp 4.249 2.124 0.7905 2.69 0.025
Mold temp -1.446 -0.723 0.7905 -0.91 0.384
Inj press 0.649 0.324 0.7905 0.41 0.691
Hold press -2.311 -1.156 0.7905 -1.46 0.178
Ct Pt 2.654 3.2595 0.81 0.436
4.2 ANOVA : Degradation
From the ANOVA analysis :
1. Hot runner temperature is a significant factor for MFI Degradation.
2. Melt temperature is a significant factor for MFI Degradation.
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403020
30.0
28.5
27.0
25.5
24.0
260250240 260250240
908070
30.0
28.5
27.0
25.5
24.0
1007550 302010
Inj SpedMean
Hot runner Melt temp
Mold temp Inj press Hold press
Corner
Center
Point Type
Main Effects Plot for Degrad. %Data Means
4.3 Main Effect Plot : Degradation
From the Respond Graph :
1. When Hot runner temperature increase, MFI Degradation % will
increase.
2. When Melt temperature increase, MFI Degradation % will increase.
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4.4 Interaction Plot
260250240 260250240 908070 1007550 302010
30
25
20
30
25
20
30
25
20
30
25
20
30
25
20
Inj Sped
Hot runner
Melt temp
Mold temp
Inj press
Hold press
20 Corner
30 Center
40 Corner
Inj Sped Point Type
240 Corner
250 Center
260 Corner
runner
Hot
Point Type
240 Corner
250 Center
260 Corner
temp
Melt
Point Type
70 Corner
80 Center
90 Corner
temp
Mold
Point Type
50 Corner
75 Center
100 Corner
Inj press Point Type
Interaction Plot for Degrad. %Data Means
From the Interaction Plot Graph :
No significant interaction among the six factors.
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4.6 Response Optimzer
Inj Speed = 20
Hot runner = 240
Melt temp = 240
Mold temp = 90
Inj press = 50
Hold press = 30
Coincidently, same to Trial 9 condition
Predicted Responses
Degradation % = 18.9
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4.7 Transfer Function :
Degradation % = -96.933 + (0.306*Hot runner temperature) + (0.212*Melt
temperature) –(0.072*Mold temperature)-(0.116*Hold pressure)
Estimated Coefficients for Degrad. % using
data in uncoded units
Term Coef
Constant -94.7094
Hot runner 0.305688
Melt temp 0.212438
Mold temp -0.0723125
Hold press -0.115563
Ct Pt 2.65437
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5.0 Summary :
� Hot Runner Temperature and Melt Temperature are significant
factors for MFI Degradation.
� Hot Runner Temperature and Melt Temperature need to be
controlled at low setting. The Optimum condition, which
coincidently has the same condition as Trial 9.