String Diagram
Consider five different parts (#1, #2, #3, #4, #5) which travel from R (receiving) to S(Shipping) departments by following different routes. Between receiving and shipping, there are machines located at A, B, C, D, E and F. Our job is to find a layout which will reduce the travel time and increase the efficiency. We can make improvements by rearranging the flow.
|
Part Number |
Route |
|
1 |
R A B D C F S |
|
2 |
R B D C A S |
|
3 |
R E F B A C D S |
|
4 |
R F A C D S |
|
5 |
R C A D S |
Table 1. Part Number and Route each part travels
Figure 1. Route for Part 1
Figure 2. Route for Part 2
Figure 3. Route for Part 3
Figure 4. Route for Part 4
Figure 5. Route for Part 5
Best layout would require only:
7 steps x 5 parts = 35 steps (From R to S)
|
Part |
Number of Steps |
|
1 |
9 |
|
2 |
13 |
|
3 |
17 |
|
4 |
17 |
|
5 |
11 |
|
TOTAL |
67 |
|
EFFICIENCY |
52 % |
Efficiency = Total steps (best layout) / Total actual steps
Efficiency = 35 / 67 = 52 %
After the flow analysis is performed, one of the goals is to reduce the total number of steps required to complete a process. Reduction in number of steps will improve the efficiency. To improve the layout, look for important relationships, such as more than one part taking the same route. As an example, look at the C to D route. Four of the five parts make this trip, so this relationship is important and C must stay close to D. Here are the routes that are used more than once:
C-D line 4 times
A-C line 4 times
D-S line 3 times
B-D lines 2 times
Flow C-D is considered forward flow and flow D-C is considered backtracking flow. Another goal of flow analysis techniques is to reduce the number of backtracking.
Let us rearrange the layout. In the previous layout R-F; A-S; B-F; R-E were the routes that produced high number of steps, thus causing longer travel distances. We are going to rearrange the layout and make R-F; A-S; B-F; R-E routes shorter. Since we had C-D and A-C repeated four times we are going to keep C-D and A-C as close as possible. Our new layout is given below:
|
Part Number |
Route |
Number of Steps |
|
1 |
R A B D C F S |
19 |
|
2 |
R B D C A S |
11 |
|
3 |
R E F B A C D S |
11 |
|
4 |
R F A C D S |
7 |
|
5 |
R C A D S |
9 |
|
TOTAL |
57 |
|
|
EFFICIENCY |
61.4 % |
Efficiency = Total steps (best layout) / Total actual steps
Efficiency = 35 / 57 = 61.4 %
|
Last Update: September 20, 1999 |
|
Prepared by : Serdar Z. Elgun |
