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5.35 - Rank Order Clustering (ROC) Analysis

Application

When designing cellular manufacturing processes we need to find what machines and tasks can be assigned to a particular cell or group of cells.

This is done finding which processes are common to what products. The parts or products are first selected as possible candidates for common manufacture by sorting them into similar types. Once we have a coarse grouping we can then do a finer sort to find common processes. Rank Order Clustering (ROC) analysis done in a spreadsheet to help with that.

An Example -

Five parts (A, B, C, D and E) similar in form use a number of processes but to what degree do they share the processes?

Parts Right Arrow


A

B

C

D

E

Totals

↓ Processes

Binary

Dec.

1

1

 

1

1

 

10110

22

2

 

1

   

1

01011

9

3

1

 

1

1

 

10110

22

4

1

 

1

1

 

10110

22

5

       

1

00001

1

6

1

1

1

1

1

11111

31

7

 

1

   

1

01001

9

8

1

   

1

 

10010

18

9

1

 

1

1

 

10110

22

10

1

 

1

1

 

10110

22

11

 

1

   

1

01001

9

12

1

 

1

1

 

10110

22

13

 

1

   

1

01001

9

14

 

1

   

1

01001

9

Binary Total

             

Decimal

             

By a cursory inspection we can quickly see that products A, C and D share common processes 1, 3, 4, 9, 10 and 12.

First Stage Sorting

The next stage is to re-order the processes according to their binary totals thus:-

Parts Right Arrow


A

B

C

D

E

Totals

↓ Processes

Binary

Dec.

6

1

1

1

1

1

11111

31

1

1

 

1

1

 

10110

22

3

1

 

1

1

 

10110

22

4

1

 

1

1

 

10110

22

9

1

 

1

1

 

10110

22

10

1

 

1

1

 

10110

22

12

1

 

1

1

 

10110

22

8

1

   

1

 

10010

18

2

 

1

   

1

01011

9

7

 

1

   

1

01001

9

11

 

1

   

1

01001

9

13

 

1

   

1

01001

9

14

 

1

   

1

01001

9

5

       

1

00001

1

Binary Total

             

Decimal

16320

8254

16256

16320

8255

   

Second Stage Sorting

Then sort the columns by their totals and we get the result below. We have two clear cell configurations (brown and green) highlighted as shown below. An issue that remains is that ALL the products go through process 6. This could be resolved by duplicating the machines for that process - if practical.

Parts Right Arrow


A

D

C

E

B

Totals

↓ Processes

Binary

Dec.

6

1

1

1

1

1

11111

31

1

1

1

1

   

10110

22

3

1

1

1

   

10110

22

4

1

1

1

   

10110

22

9

1

1

1

   

10110

22

10

1

1

1

   

10110

22

12

1

1

1

   

10110

22

8

1

1

     

10010

18

2

     

1

1

1011

9

7

     

1

1

1001

9

11

     

1

1

1001

9

13

     

1

1

1001

9

14

     

1

1

1001

9

5

     

1

 

1

1

Binary Total

             

Decimal

16320

16320

16256

8255

8254

   

After sorting the binary and decimal values for the rows actually change their values, but it does not affect the results.

See guide 6.19 for information on finding common parts in similar assemblies to assist with part rationalisation and modular design. Some common parts analysis software that comes with part and shape classification tools can also do this by analysing the part routing and Bill of Material files.

 
Further Reading