Because of some advantages of Flow Manufacturing, that is why we set the cell on the conveyor to inherit these advantages. And that is why cell have to balance on the production flow to avoid bottleneck on the line. All cells have to balance about time.
Due to the movements and operating of cell, Cell 1, cell 2, Cell 5, Cell 6 is called Assembly Cell. The other is machining cell. Machining cell is one kind of cell which almost contain machine. Machine is main component of cell, on the contrary, the operator do all the movements of cell. And the time of Cell is shown in the table 4.7
Number Type of cell Time (seconds)
Cell 1 Assembly cell 89.06s
Table 4. 7 Duration of cell
Time of cell is not equal, but this cell will set on the production flow. That is why we have to make it even in order to make the production flow go smoothly. Cells are divided into 2 groups which are Machining cell and Assembly Cell.
4.4.1. Assembly Cell
From the above writing and table, there are four assembly cells. And the cycle time of cell 1, cell 2, cell 5, cell 6 is CT1 = 89.06s, CT2 = 87.05s, CT5 = 116.03s, CT6 = 107.59s.
Those are different from cell to cell.
To increase the capacity of the cell or reduce time of cell, it is necessary to add more operators or by using the chasing method. With chasing method, adding a second operator will cut the cycle time in half, and double the output; adding a third operator will reduce the
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cycle time and increase the output. The reducing time base on the number of worker, then the cycle time calculates again by:
The time of cell also adjusts by this method. From the table…, it is easy to see the time is unbalance, if we arrange those cells on the line (conveyor), the combined production line does not so smoothly. Using this method to balance time for cell, that is other purpose of this method. Time of assembly cell divides into to group, under 100 second, cell1 and cell 2 and over 100 second, cell 5 and cell 6. For this method, the time can make approximate by using three operators for cell 1 and cell 2 (under 100 second) and four operators for cell 5 and cell 6. Then, the cycle time is recalculated in table 4.8.
Cell CTa
1 CTa1 =
2 CTa2 =
5 CTa5 =
6 CTa6 =
Table 4.8 Actual cycle time for assembly cell
The time for cell is known, and the number of operator is determined. Then, the cell operation is going reconstruct. Assembly cell is being reconstructed cell by cell.
i. Cell 1 (structure):
The average time for each operator is 29.7 seconds. And this cell has three operators to implement in three stations in the figure
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Figure 4. 10 Cell 1 separated From figure 4.10 , we have the time:
Station 1 = 10.4 + 2.19 + 5.85 + 5.84 + 7.12 = 30.04 seconds Station 2 = 10.73 + 6.54 + 6.25 + 4.25 =27.77 seconds Station 3 = 12.78 + 6.15 + 7.71+ 3.25 = 29.89 seconds
So the actual cycle time of cell: CTa1 = max (station 1, station 2, station 3) = 30.04 seconds. And the layout of cell 1 creates with three operators.
ii. Cell 2 - AFT (Assembly Function test)
The average time for each operator is 29 seconds. And this cell has three operators to implement in three stations in the figure
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Figure 4. 11 Separating cell 2
From figure 4.11, we have the time:
Station 1 = 6.10 + 5.96 + 12.38 + 5.51 = 29.95 seconds Station 2 = 24.28 + 5.56 = 29.84 seconds
Station 3 = 13.78 + 4.16 + 6.6 + 4.51 = 29.35 seconds
So the actual cycle time of cell: CTa1 = max (station 1, station 2, station 3) = 29.95 seconds. And the layout of cell 1 is operated by three operators.
iii. Cell 5 and cell 6 ( Program function test and Packing)
From the above writing, the time of cell 5 and cell 6 is different, some action of cell is exceed cycle time. In the cell 5 the test item takes 43.81 seconds and the other action took smaller time. In cell 6, the duration for disassembly is 31.04 second. In addition, it is hard to merge action of station because the time of actions have big gap. So the chasing method is not suit in this problem. Then, we have to use the other method that is the adding operator. It is different from the chasing method. Cell has fours operator, each operator has to finish one completed product. And the layout of cell 5 and cell 6 is shown in the figure:
In conclusion, the assembly cells have actual cycle time as follow, CTa1 = 30.04 seconds, CTa1 = 29.95 seconds, CTa5 = 28.4 seconds, CTa6 = 26.9 seconds. The actual cycle time for cell is the maximum time of this assembling cell. Thus, actual cycle time is 30.04 seconds.
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Time in the machining cell is not equal too. But in this case study, it is very simple for machining cell. Computer just put on the stand and it will run by itself. However, we have to calculate the number of stand to meet the time of assembly cell. The cycle time of machine cell is less than the cycle time of assemble cell. The cycle time is calculated as:
So the cycle time is known from the assemble cell. Number of machine is found by the formula:
Then, we have number of machine with the cycle time 30.04 seconds. And, the average time for take the part to the other line is 5 second.
Cell Number of machine (Brackets)
3 Bracket = (Brackets)
4 Bracket = (Brackets)
7 Bracket = (Brackets)
Table 4. 9 Number of bracket
In the cell machine, the part runs itself that is why we only need the bracket to put the unfinished part. On the bracket, some needed equipments already prepare such as LAN wire, power. The figure 4.12 shown one kind of bracket can use for machine cell.
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Figure 4. 12 Structural of Bracket