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Chapter 6: Case Studies and discussion

CHAPTER 6

CASE STUDIES AND DISCUSSION

Two case studies are performed to demonstrate the performance of the developed CAPP

system. Since the top plate and window clamp are the most important components of the

lead frame wirebonding clamping assembly and the process planning for these

components are more complex than rest of the components, only case studies for these

components are discussed in this chapter. For each case study, two major areas of the

system, generation of process plan and generation of CNC tool path are discussed with an

example. In the section, generation of process plan, two major steps, preliminary

selection of process plan parameters and the final selection of the parameters by using

optimization technique are also discussed.

6.1 CASE STUDY 1

The case study is performed for the particular top plate type (type 2). The features of the

specific top plate type are shown in the Fig. 6.1. From the figure, it can be observed that

the component consists of manufacturing features such as face, angle face, through hole,

counter sink hole, slot, dove tail face, pocket, profile and so on. Each of these features

can be machined in one or more operations and an operation may have more than one sub

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operations. The generated optimal process plan and CNC tool path for these operation

and sub-operation for this case study, is described in next two sections.

Fig. 6.1 Feature identifications of a specific Top plate type

Face 3

Fitting

hole

Face 1

Face 2

Face 8

Face 4

Hole 2

Slot 2

Slot 1

Angle face 1

Face 7Hole 1

Counter

sink Hole

Angle face 2

Face 6

Face 10

Face 9

Face 11

Face 12

Vacuum ways

Vacuum holes

Face 13

Dove tail 1

Dove tail 2

Face 5

Face 3Face 3

Fitting

hole

Face 1Face 1

Face 2Face 2

Face 8

Face 4

Hole 2

Slot 2

Slot 1

Angle face 1

Face 7Hole 1

Counter

sink Hole

Angle face 2

Face 6

Face 10

Face 9

Face 11

Face 12

Vacuum ways

Vacuum holes

Face 13

Dove tail 1

Dove tail 2

Face 5

6.1.1 Generated process plan

There are 33 operations needed to manufacture the component shown in Fig. 6.1. For

each operation, various constraints are applied to select the process plan parameters

preliminarily such as preliminary selection of machine tool, cutter, cutting conditions etc.

For the final solution for each operation, a SA-based algorithm searches, which

combination gives optimum or near optimum solution for minimum processing cost for

the component. Fig. 6.2 shows the convergence of the algorithm with the decreasing of

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the temperature. From the figure, it is shown that in the initial stages; up to an iteration of

100, the algorithm does not reject the solution, which is worse than the previous one,

instead it selects the solution with certain probability, which ensure that the system is not

trapping for the local minima. After 100 iterations, the system starts to converge and end

up with the final value of the processing cost of the component as S$ 280.

0

100

200

300

400

500

600

0 20 40 60 80 100 120 140 160 180 200 220 240 260

No. of iteration

Fitness

Value

(in

S$)

Fig. 6.2 Convergence of SA algorithm with the iteration number for case study 1

After optimizing, the list of the operations and generated process plan to manufacture the

features are shown in the table 6.1. The first operation of the manufacturing process of

the component is to select the appropriate raw material. For that, the specification of the

designed component is extracted from the CAD model and it is

. Keeping 2 mm machining allowance in all direction, the

dimension of the minimum blank size is calculated as110 .From

mm5.9mm50mm108

mm5.11mm52mm

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the available stocks (as shown in table 3.2), it is found that the smallest blank size is

and B50 is assigned as the raw material to be used. In operation

2, the extra material in selected raw blank, B50 is premilled to the blank size,

by a saw cutter. In column 3 of Table 6.1, the generated

process plan for each operation are represented according to the representation equation

(4.1).

mm15mm55mm110

mm5.11mm52mm110

In operation 3, a step in face 5 is machined with process of P05, which is step-machining

process (please refer to Fig. 3.5). Machine number 2 (M02) of Machine type CNC

milling machine (MY04) is selected for this process. Under Machine number 2, cutter

number 31 (T31) of Cutter type end mill (CT02) is selected. Selected cutting conditions

for this operation are speed 800 rpm, feed 120 mm/min and depth of cut 0.6 mm.

In operation 9, a countersink hole is machined by 4 sub-operations. Machine number 01

(M01) of machine type Radial drill (MY02) is used for these 4 sub-operations. In first

sub-operation, a cutter type center drill (CT06) is used to initialize the hole by the process

of hole initializing (P12). In the second sub-operation, cutter type drill (CT05) is selected

to make the hole by process of hole making (P02).

6.1.2 Generated CNC tool path

By inputting into the CNC template from the selected process plan parameters and

retrieving the CNC template for the component, the CNC tool path is generated. Fig. 6.3

shows the generated tool path and the generated cutter location source file (text file) for

operation 4. Table 6.2 shows the parameters used for this tool path.

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Table 6.1 Optimal Process plan generated for the Top plate type shown in Fig. 6.1

Opera-tionNo.

Feature Process Plan parameterProcessingcost (in S$)

1Raw

Materialselection

Material: AISI 420Blank Size: 110 mm X 55 mm X 15 mm

2 Premill Sawing

3Step forface 5

S (P05, MY04, M02, CT02, T31, {800, 120, 0.6})

4 Face 6 S (P04, MY04, M02, CT02, T23, {2500, 250, 0.85})

5 Face4 S (P04, MY04, M01, CT2, T31, {800, 120, 0.65})

6Chamfer-

ing onface 4

S (P09, MY04, M02, CT08, T05, {8000, 50, 0.95})

7 Face 7 S (P04, MY04, M01, CT02, T31, {800, 120, 1})

8Chamfer-

ing onface 7

S (P09, MY04, M01, CT08, T05, {8000, 50, 1.5})

9Counter-sink hole

S (P12, MY02, M01, CT06, T09, {2000, 100, N/A})S (P02, MY02, M01, CT05, T09, {1300, 100, N/A})S (P03, MY02, M01, CT13, T01, {1300, 100, N/A})S (P03, MY02, M01, CT12, T01, {2500, 100, N/A})

10Slot 1 on

face 5S (P12, MY04, M01, CT06, T01, {2000, 100, N/A})S (P06, MY04, M01, CT02, T07, {8000, 100, 1.3})

11 Face 1 S (P04, MY04, M02, CT01, T36, {900, 1000, 0.95})

12 Face 2 S (P04, MY04, M01, CT02, T21, {1000, 100, 1.3})13 Face 3 S (P04, MY04, M01, CT02, T25, {1000, 100, 1.5})

14Angleface 1

S (P04, MY04, M02, CT08, T04, {9000, 50, 0.85})

15Angleface 2

S (P04, MY04, M02, CT08, T04, {9000, 50, 1.5})

16 Face 8 S (P04, MY04, M02, CT01, T38, {500, 250, 0.75})

17 Face 9 S (P04, MY04, M01, CT01, T37, {600, 550, 1.4})

18 Face 10 S (P04, MY04, M01, CT02, T30, {2400, 300, 1})

19 Face 11 S (P04, MY04, M02, CT02, T29, {800, 120, 1.2})

20Dove tail

1S (P08, MY04, M02, CT09, T03, {6000, 60, 1.3})

21Dove tail

2S (P08, MY04, M01, CT09, T02, {5000, 60, 0.5})

22Blind

pocket onface 9

S (P12, MY04, M02, CT06, T01, {2000, 100, N/A})S (P07, MY04, M02, CT02, T27, {1200, 150, 1.4})

23Slot 3 on

face 9S (P12, MY04, M02, CT06, T01, {2000, 100, N/A})S (P06, MY04, M02, CT02, T05, {10000, 100, 1.2})

280

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24Grinding

in all facesS (P10, MY05, M01, CT10, T01, {3000, 4500, 0.01})

25Heat

treatmentSand blasting Heat treatment

26 Hole 1S (P12, MY04, M01, CT06, T01, {2000, 100, N/A})

S (P02, MY04, M01, CT05, T03, {2500, 100, N/A})27 Hole 2

S (P12, MY04, M01, CT06, T01, {2000, 100, N/A})S (P02, MY04, M01, CT05, T03, {2500, 100, N/A})

28 Slot 2S (P12, MY04, M08, CT06, T01, {2000, 100, N/A})

S (P06, MY04, M08, CT02, T05, {10000, 100, 0.45})

29Face 12 incompositefeature 4

S (P04, MY04, M08, CT08, T03, {8000, 60, 0.5})

30

Face 13and

vacuum

ways incompositefeature 4

S (P11, MY04, M08, CT02, T04, {18000, 100, 0.45})

31

BlindVacuumholes in

compositefeature 4

S (P12, MY04, M10, CT06, T01, {2000, 100, N/A})S (P02, MY04, M10, CT02, T04, {18000, 100, 0.55})

32Fittingholes

Super drill

33 Polishing

Table 6.2 Tool path parameters for the operation 4 shown in table 6.1

Component Top Plate type 2

ProcessCutterCutter diameterNumber of fluteStepoverBlank distance

Depth per cutCut patternCut methodMachining strategySpeedFeed

End millingEnd mill carbide cutter4 mm230% of cutter diameter1.7 mm

0.85 mmSerial patternZig with contourDown milling2500 rpm250 mm/min

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Fig. 6.3 Generated tool path and CLSF in Unigraphics for case study 1

6.2 CASE STUDY 2

In this case study, the features, generation of optimal process plan and the CNC tool path

for the particular window clamp type (type 1) is presented. The features of the specific

window clamp type are shown in the Fig. 6.4a and 6.4b. From the figures, it can be

observed that the component consists of manufacturing features such as face, angle face,

through hole, slot, pocket, profile and so on. Each feature on this list, can be machined in

one or more operations and an operation may have more than one sub- operations. The

generated optimal process plan and CNC tool path is described in next two sections.

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Fig. 6.4a Feature identifications in the top view of a specific Window clamp type

Face 5

Angle

face 2

Face 3

Angle

face 1 Face 4Face 6

Hole 2Hole 3

Hole 1

Slot 1

Window

Clamp cavity

Face 1

Angle

face 3

Angle

face 4

Face 2

Face 5

Angle

face 2

Face 3

Angle

face 1 Face 4Face 6

Hole 2Hole 3

Hole 1

Slot 1

Window

Clamp cavity

Face 1

Angle

face 3

Angle

face 4

Face 2

Face 7

Face 9

Face 14

Angle face 8

Face 12

Face 13

Pocket on face 13

Face 11

Angle face 5

Pocket on face 14

Angle face 6

Face 3

Face 7

Face 9

Face 14

Angle face 8

Face 12

Face 13

Pocket on face 13

Face 11

Angle face 5

Pocket on face 14

Angle face 6

Face 3

Fig. 6.4b Feature identifications in the bottom view of a specific Window clamp type

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6.2.1 Generated process plan

There are 33 operations needed to manufacture the component shown in Fig. 6.4a and

6.4b. For each operation, various constraints are applied to select the process plan

parameters preliminarily such as selection of machine tool, cutter, cutting conditions etc.

For final solution of each operation, a SA-based algorithm searches, which combination

gives optimum or near optimum solution for minimum processing cost for the

component. Fig. 6.5 shows the convergence of the algorithm for the case study with the

decreasing of the temperature. From the figure, it is shown that in the initial stages; up to

an iteration of 135, the algorithm does not reject the solution, which is worse than the

previous one. After 135 iterations the system starts to converge and end up with the final

value of the processing cost of the component as S$ 246.23.

After optimizing, the list of the operations and generated process plan to manufacture the

features are shown in the table 6.3. The first operation of the manufacturing process of

the component is to select the appropriate raw material. For that, the specification of the

designed component is extracted from the CAD model and it is

. Keeping 2 mm machining allowance in all direction, the

dimension of the minimum blank size is calculated as119 .From

the available stocks (as shown in table 3.2), it is found that the smallest blank size is

and B59 is assigned as the raw material to be used. In

operation 2, the extra material in the selected raw blank, B59 is premilled to the blank

size, by a saw cutter. . In column 3 of Table 6.3 the generated

mm10mm55mm120

mm75.6mm52mm119

mm75.4mm50mm117

mm75.6mm52mm

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process plan for each operation are represented according to the representation equation

(4.1).

200

220

240

260

280

300

320

0 50 100 150 200

No. of iteration

F

itness

Value

(in

S$)

Fig. 6.5 Convergence of SA algorithm with the iteration number for case study 2

In operation 3, a face is machined with the process of P04, which is face milling process.

Machine number 2 (M02) of Machine type CNC milling machine (MY04) is selected for

this process. Under Machine number 2, cutter number 37 (T37) of Cutter type face mill

(CT01) is selected. Selected cutting conditions for this operation are speed 600 rpm, feed

550 mm/min and depth of cut 0.95 mm.

In operation 4, a step in face 2 is machined by the process of step machining (P05).

Machine number 2 (M02) of machine type CNC milling machine (MY04) is used for the

process. Under Machine number 2, cutter number 30 (T30) of Cutter type end mill

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(CT02) is selected. It is noted here, that for this operation, face milling is not selected for

the process knowledge constraints. The leftover of the feature is two sidewalls, which

cannot be created by the face milling.

In operation 8, an angle face is machined by the process of chamfer milling (P09). Cutter

number 5 (T05), under the cutter type chamfer cutter (CT08) is selected for this

operation. Selected cutting conditions for this operation are speed 9000 rpm, feed 50

mm/min and depth of cut 0.95 mm.

Table 6.3 Optimal Process plan generated for the Window clamp type shown in Fig. 6.4a

and 6.4b

Opera-tionNo.

Feature Process Plan parameterProcessingcost (in S$)

1Raw

Materialselection

Material: AISI 420Blank Size: 120 mm X 55 mm X 10 mm

Blank No. B59

2 Premill Sawing

3 Face 1 S (P04, MY04, M02, CT01, T37, {600, 550, 0.95})

4

Step on

Face 2 S (P05, MY04, M02, CT02, T30, {2400, 300, 0.85})5 Face 3 S (P04, MY04, M01, CT01, T37, {600, 550, 0.95})

6 Face 4 S (P04, MY04, M01, CT02, T22, {8000, 400, 0.85})

7 Face 5 S (P04, MY04, M02, CT02, T23, {1300, 150, 0.85})

8Angleface 1

S (P09, MY04, M01, CT08, T05, {9000, 50, 0.95})

9Angleface 2

S (P09, MY03, M01, CT08, T05, {9000, 50, 0.95})

10Angleface 3

S (P09, MY04, M02, CT08, T05, {9000, 50, 0.95})

11

Angle

face 4 S (P09, MY04, M01, CT08, T05, {9000, 50, 0.95})12 Face 8 S (P04, MY04, M02, CT01, T37, {600, 550, 0.95})

13 Face 6 S (P04, MY04, M01, CT01, T38, {500, 250, 0.95})

14Step onface 6

S (P05, MY04, M02, CT02, T17, {2500, 120, 0.85})

15Angleface 7

S (P09, MY04, M01, CT08, T05, {9000, 50, 0.95})

246.23

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16 Face 7 S (P04, MY04, M01, CT01, T38, {500, 250, 0.95})

17Step onface 7

S (P05, MY04, M02, CT02, T15, {3000, 150, 0.85})

18Angleface 5

S (P09, MY04, M02, CT08, T02, {8000, 60, 0.95})

19 Face 12 S (P04, MY04, M02, CT01, T38, {500, 250, 0.95})

20Step on

face 12 forface 13

S (P05, MY04, M02, CT02, T30, {2400, 300, 0.85})

21Step on

face 12 forface 14

S (P05, MY04, M01, CT02, T20, {9000, 270, 0.85})

22Angleface 8

S (P09, MY04, M01, CT08, T05, {9000, 50, 0.95})

23Angleface 6

S (P09, MY04, M01, CT08, T05, {9000, 50, 0.95})

24 Pocketson face 13

S (P07, MY05, M02, CT02, T16, {12000, 350, 0.85})

25Pockets

on face 14S (P07, MY04, M02, CT02, T20, {9000, 270, 0.85})

26 Hole 1S (P12, MY03, M01, CT06, T09, {2000, 100,N/A})S (P02, MY03, M01, CT05, T09, {1300, 100, 1.2})

27 Hole 2S (P12, MY03, M01, CT06, T09, {2000, 100,N/A})S (P02, MY03, M01, CT05, T12, {1100, 100, 1.2})

28Grinding

in all facesS (P10, MY04, M01, CT10, T01, {3000, 4500, 0.01})

29Heat

treatmentSand blasting Heat treatment

30 Hole 3S (P12, MY04, M01, CT06, T09, {2000, 100,N/A})S (P02, MY04, M01, CT05, T04, {2500, 100, 0.6})S (P03, MY04, M01, CT12, T01, {2500, 100, N/A})

31 Slot 1S (P12, MY04, M08, CT06, T09, {2000, 100,N/A})

S (P06, MY04, M08, CT02, T05, {10000, 100, 0.45})

32Windowclampcavity

S (P11, MY04, M02, CT02, T23, {1300, 150, 0.85})

33 Polishing

6.2.2 Generated CNC tool path

By inputting into the CNC template from the selected process plan parameters and

retrieving the CNC template for the component, the CNC tool path is generated. Fig. 6.6

shows the generated tool path and the portion of the generated cutter location source file

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(text file) for operation 4. Table 6.4 shows the parameters used for this tool path.

Appendix B shows the full details of the generated cutter location source file.

Fig. 6.6 Generated tool path and CLSF in Unigraphics for case study 2

Table 6.4 Tool path parameters for the operation 4 shown in table 6.3.

Component Window Clamp type 1

ProcessCutterCutter diameterNumber of fluteStepoverBlank distanceDepth per cut

Cut patternCut methodMachining strategySpeedFeed

End millingEnd mill carbide cutter16 mm240% of cutter diameter0.85 mm0.85 mm

Serial patternZig with contourDown milling2400 rpm300 mm/min

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