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Application of TRIZ and Taguchi Methods: Two Case Examples

| On 05, Jan 1999

First published in the Proceedings of the Taguchi Methods Conference, 4th Total Product Development Symposium, 1998, American Supplier Institute

By: Dr. Leslie Monplaisir, Rajesh Jugulum and Mahfoozulhaq Mian
Department of Industrial and Manufacturing Engineering
Wayne State University, Detroit MI 48202.

Abstract

During the past several years many techniques have been developed in the area of quality engineering. All these techniques are aimed at improving the quality of a product/service. The focus has been shifted from customer satisfaction to customer delightment. In this paper, we present two case studies where TRIZ and Taguchi Methods (TM) are applied. The first case study is aimed at improving process of Flourination and in the second case study we developed an innovative concept for Coordinate Measuring Machine (CMM) to support all kinds of manufactured parts for measurements.

Study 1: Improving the process of Flourination

Objectives of the Study
The objectives of this study are as follows:

  1. To improve the performance (uniformity) of Flourination process.
  2. To maximize yield (number of batches/day) of Flourinated plastic bottles.

These objectives are accomplished in two stages. The description of these stages is given below:

Stage 1: In the first stage, it is required to find a source that would take the fluorine gas to each of the plastic bottles without increasing the cost and without making the system complicated. TRIZ methodology is used to accomplish the objective of this stage.

Stage 2: In the second stage the yield of Flourinated plastic bottles (number of batches/day) is maximized using Taguchi Methods.

Fluorination Process

Fluorination process is a gas modified plastic technology that reduces permeability and improves chemical resistance through surface treatment of the polymer. Fluorine gas is a strong oxidant that reacts with the plastic surface to replace the weak Hydrogen molecule in the polymer. In the other words, Fluorination enhances the usability of plastic container so that it can carry different solvents to help maintain product shelf life without solvent penetration. Basically, the cost for fluorinating any plastic surface outweighs the cost and usage of multi-layer (an expensive resin), metal, and glass. Pesticides, 2-cycle oil, mineral spirits, and solvents are just a few of the many solvents that are stored in fluorinated containers.

Customers are provided with four different types of Flourinated plastic bottles depending on the application.

  • B-24 20-40% of total surface uniformly flourinated
  • B-46 40-60% of total surface uniformly flourinated
  • B-68 60-80% of total surface uniformly flourinated
  • B-810 80-100% of total surface uniformly flourinated

It should be noted that production of each type of these bottles is the same.

Stage 1
Application of Algorithm for Inventive Problem Solving (ARIZ)

Primary Function:
Fluorination of plastic bottles by introduction of fluorine gas in process reactor.

Component List

  • Fluorine Gas
  • Process Reactor
  • Injection Ports
  • Conveying Trolley
  • Plastic Bottles

Conflicting Components

  • Article(s): Plastic Bottles
  • Main Tool(s): Fluorine Gas

System Conflicts

(SC-1) Increasing the amount of fluorine gas will enhance the uniformity of Fluorination in plastic bottles, but it will increase the process cost substantially.

(SC-2) Decreasing the amount of fluorine gas will not enhance the uniformity of fluorination among plastic-bottles, but it will decrease the process cost. This makes the process more competitive.

Conflict Intensification

(SC-1) Infinite amount of fluorine gas will fluorinate the plastic bottles with high uniformity, but it will increase the process cost infinitely.

(SC-2) Zero amount of fluorine gas will not fluorinate the plastic bottles, but it will reduce the process cost to a minimum.

Conflict Diagrams

1.gif (2103 bytes)


2.gif (1710 bytes)

Su-field Analysis

3.gif (2240 bytes)

We need F2, a mechanical force that can transport the gas to each bottle and also distribute it uniformly in the process chamber with out complicating the system.

Mini Problem

It is required to find such an X source that would take the fluorine gas to each of the plastic bottle without increasing the cost and without making the system complicated.

Conflict Domain

The area occupied by plastic bottles and fluorine gas.

Operation Time

Pre-Conflict Time: Before putting the plastic bottles in process reactor.

Conflict Time: When the fluorine gas will be introduced in the process reactor.

Post Conflict Time: After Completion of Fluorination.

Resources

Fluorine Gas, Gravity, Vacuum, Plastic Bottles.

Selection of the X-Resources

Gravity

Ideal Final Result

Gravity in the conflict domain during the operation takes the fluorine gas up to each plastic-bottle without complicating the system.

Solution

The process reactor is under vacuum during the reaction (0-10 Tore. pressure). Since fluorine gas is 1.5 heavier than air, it always tends to move downward due to gravitational force. If we position the fluorine gas molecules on the top of the plastic bottles it will automatically move down. This will not increase the cost and complicate the system. The gas dynamics is an important property of the gas distribution. Therefore by placing showerhead injection ports at the top of the process reactor one can generate better gas dynamics and hence uniform distribution. This will enhance the reaction to achieve an optimal solution to the distribution problem.

Therefore, the ports are placed on the top of the reactor. Earlier the ports were on the sides of the reactor. For improving the uniformity a blower was kept below the ports. With this arrangement, the uniformity was greatly increased because of above mentioned gas dynamics properties.

Application of Taguchi Methods

The main aim after identifying the source, which would take fluorine gas to all plastic bottles, is to maximize the number of batches of plastic bottles per day by improving Fluorination process. To accomplish this TM is used. TM was applied on one the type (B-24) of the plastic bottles.

While using Taguchi Methods following steps were followed:

  • Identify the Intent and Perceived Result
  • Determine the factors and their levels
  • Formulate the experiment
  • Analyze Data and choose the best design

After conducting a series of brainstorming sessions the factors, as shown in table 1, have been chosen for the experiment.

Table 1: Factors and Levels

Factor

Factors

Level 1

Level 2

Level 3

Level 4

A

Conc. Of fluorine
/carbon dioxide (%)

3

5

7

8

B

Dwell Time (min)

60

90

150

210

C

Internal
Temperature (F)

120

130

D

Differential
Pressure (PSIG.)

2

1.5

E

Shift (min)

480

600

F

Size (vol.)

Large

Small

G

Pre-heat

On

Off

H

Chamber (#)

1

2

Selecting Experimental Layout

To accommodate above factors, L16 (215)
Orthogonal Array was chosen. The factor allocation to this array is shown in table 2.

Table 2: Factor Allocation for the Experiment

Exp. No

Col. 1,2,3

col. 5,10,15

col. 4

Col. 6

col. 7

col. 8

col. 9

col. 11

Col 12, 13 &14: Error

A

B

C

D

E

F

G

H

F2/CO2 (%)

Dwell Time (min)

Int. Temp (F)

Diff. Press. (psig)

Shift (hr.)

Size (vol.)

Preheat

Chamber (#)

1

1

1

1

1

1

1

1

1

2

1

2

1

1

1

2

2

2

3

1

3

2

2

2

1

1

1

4

1

4

2

2

2

2

2

2

5

2

2

1

2

2

1

1

2

6

2

1

1

2

2

2

2

1

7

2

4

2

1

1

1

1

2

8

2

3

2

1

1

2

2

1

9

3

3

1

1

2

1

2

2

10

3

4

1

1

2

2

1

1

11

3

1

2

2

1

1

2

2

12

3

2

2

2

1

2

1

1

13

4

4

1

2

1

1

2

1

14

4

3

1

2

1

2

1

2

15

4

2

2

1

2

1

2

1

16

4

1

2

1

2

2

1

2

Experimental Results

The experiments were conducted as per above layout. The results of
these experiments are given in table 3.

Table 3: Experimental Results

Exp. No

Yield

(No. of batches)

S/N Ratio

1

0.66

-3.609

2

0.96

-0.355

3

0.50

-6.021

4

0.93

-0.63

5

0.89

-1.012

6

0.55

-5.192

7

0.92

-0.724

8

0.63

-4.013

9

0.75

-2.498

10

0.56

-5.036

11

0.87

-1.21

12

0.97

-0.264

13

0.67

-3.479

14

0.83

-1.618

15

0.58

-4.731

16

0.91

-0.819

After analyzing results, it is concluded that B2, E1, and H2 are the optimal

Confirmation Test

The confirmation tests are conducted for all types of the bottles. The test results closely matched with predicted results. With the optimal results, the yield is improved to 90%. The yield before the experiment was 65%.

Study 2: CMM Support Problem

Objective of the Study:

The objective of this study is to develop an innovative concept for the universal support by using TRIZ. This is necessary to solve a very common problem that people in industry face; supporting various kinds of parts of plastic or metal with different types of supports during the process of inspection.

Application of Algorithm for Inventive Problem Solving (ARIZ)

Primary function

Different types of supports are used to align the components on the bed of a CMM machine to accurately perform various types of measurement operations.

Component List

CMM Bed, Supports, Parts, Measurement Probs.

Conflicting Components

  • Article Parts to be measured
  • Main Tool CMM Bed, Supports

System Conflicts

SC-1: Different types of supports can support one type of
component parallel to surface of machine bed.

SC-2: Same supports cannot support a different component, which makes the system complicated and inaccurate.

Conflict Intensification

ISC1: Infinite types of supports can support virtually any shape but complicates the system infinitely.

ISC2: Zero support simplifies the system but cannot support the parts at all.

We selected the ISC2 for further analysis, as it makes the system very simple.

Conflict Diagram

4.gif (2060 bytes)


5.gif (2314 bytes)|

Su-field Analysis

6.gif (3080 bytes)

Mini Problem

It is required to find such an X source that would

  • support the parts parallel to CMM bed accurately
  • not make the system complex

Conflict Domain

Area of contact between the part and supports.

Operating Time

Pre Conflict Time: Before putting a part on machine bed.

Conflict Time: When a part will be placed at the top of supports.

Post Conflict Time: After completion of inspection.

Resources

Air, Gravity, Magnetic Field, Atmospheric Pressure

Selection of X Resource

Atmospheric Pressure

Ideal Final Result

Atmospheric Pressure in the conflict domain during operation time
supports the part without complicating the system.

Physical Contradiction

During conflict time and within conflict domain to support a part,
Atmospheric Pressure must behave lake a solid. To take the shape of part’s profile
Atmospheric Pressure must also be flexible.

Elimination of the Physical Contradiction

Separation of opposite properties in time:

Atmospheric Pressure must be solid in the vicinity of the part’s profile and it must become flexible in the vicinity of part’s profile during conflict time and within conflict domain.

Solution

We can think of two possible solutions to this problem. Thy are as
follows:

Solution 1

We should have a mechanism, which will behave like a solid rock by using Atmospheric Pressure during the conflict time and within conflict domain. The mechanism should become flexible after the completion of operation. Such an arrangement is described below:

If we enclose sand (Silica) in an elastic bag and evacuate the air inside the bag with out removing the sand, the Atmospheric Pressure will be applied to the grains of sand to make it a solid support. By introducing the air again the sand will become flexible. We can make this type of arrangement at the conflict domain only, as we normally don not require to support the entire area of the part to be inspected. The details are clearly depicted in figure 1.

Figure 1: Solution 1 for Universal CMM Support

Solution 2

Another solution is as follows: We can also use small steel balls instead of sand. We can apply the pressure (mechanical or atmospheric) on balls to make them solid. To make the bonding of balls stronger, we can enhance the solidification stage by introducing the magnetic field at the conflict domain and during the conflict time.

Applications

This innovative support has number of applications in the industry. Some of the applications are as follows.

  1. Supporting Parts on CMM bed.
  2. Supporting parts on CNC machining center’s bed.
  3. Supporting parts on granite table for manual inspection.

Conclusions

With these examples the following conclusions can be drawn.

  • It is possible to integrate TRIZ and TM to enhance customer satisfaction. This will in
    turn reduce time, effort and cost.
  • By doing so these techniques will be part of standard operating practices so that every
    member of organization is aware of these techniques.
  • The case studies show how powerful these methodologies are. The yield improvement from
    65% to 90%, in the first example, is quite significant.
  • The subject has great potential for future research. In Wayne State University
    substantial research is being carried out to improve product development process by
    integrating these techniques.

Acknowledgement

The authors are grateful to Mr. Allie Abraham of Flourodynamics for helping us during stage I and stage II of Fluorination case study. They are also thankful to Mr. Victor Fey for his suggestions during the ARIZ analysis.

References

  1. Altshuller, G. S., (1988). Creativity as an Exact Science
  2. Victor R. Fey; Eugene I. Rivin (1997). The Science of Innovation, TRIZ group.
  3. John Terninko, Alla Zusman, Boris Zlotin (1998), Systematic Innovation, An Introduction to TRIZ, St.Lucie Press.
  4. Taguchi, Genichi. (1993). Taguchi on Robust Technology Development, ASME Press.
  5. Taguchi, Genichi. (1994). Taguchi Methods: Vol. 1 Research & Development, Japan
    Standard Association & ASI Press.
  6. Taguchi. G (1987). Systems of Experimental Design, ASI press.