MALB Assignment Rules

Dar-El’s modified rules are as follows:

1. Begin by selecting the lowest cycle time corresponding to each of the number of work stations possible by, for example, referring to the balance delay graphs. Record the slack units available.
2. Select the task with the highest positional weight and assign it to the first work station.
3. Calculate the unassigned time for the station by calculating the cumulative time for all the tasks assigned to the station and subtracting this sum from the cycle time.
4. Select the task the next highest positional weight and attempt to assign it to the station after making the following checks:

i) Check the list of already assigned tasks. If the immediate predecessor tasks have been assigned, precedence will not be violated; proceed to step 4b. If the immediate predecessor tasks have not been assigned, proceed to step 5.
ii) Compare the task time with the unassigned time. If the task time is less than the station unassigned time, assign the task and recalculate the unassigned time. If the task time is greater than the unassigned time, proceed to step 5.

5. Continue to select, check, and assign tasks, if possible one of the following two conditions is met:
i) A combination is obtained where the remaining unassigned time is less than or equals the slack units available; proceed to step 8.
ii) No unassigned task remains that can satisfy both the precedence and the unassigned time requirements; proceed to step 6.

6. Cancel each assigned task in turn, starting with the one having steps 4 and 5 until either:

i) A combination is obtained where the remaining unassigned time is less than or equals the slack units available; proceed to step 8.
ii) All combinations possible have unassigned times in excess of the slack units available so that no solution is possible; proceed to step 7.

7. Select a cycle time having one more unit and start again with step 2.
8. Assign the unassigned task with the highest positional weight to the second station and proceed through the preceding steps in the same manner.
9. Continue assigning tasks to stations until all the tasks have been assigned.

Note that rules 2,3,4,5,8 and 9 are the same as the rules for the basic procedure with a minor modification to rule 4. The important modifications are to rules 1, 6, and 7. Applying these rules to the same problem, Dar-El products the solution shown with cycle time of c = 62 seconds, one slack unit unassigned, and a balance delay of only 0.5 percent. Dar-El shows results for 4 stations and 2 stations.

Combination layouts:

There are variants of the functional and line types of layouts that commonly occur. First, many layouts are a combination of functional and line layouts, usually with fabrication operations being organized functionally and assembly being laid out in line fashion. The reasons the combinations occur are that the line layout requirements discussed are not always met for fabrication operations, particularly with regard to poor equipment utilization. Since fabrication machinery involves large investments, lower costs for this portion of the system can be obtained by time sharing equipment for a variety of parts and products. Therefore, even through the other requirements stated for a product focus may apply to the fabrication portion of the system, a combination process-product system is more appropriate.

Group Technology (GT) Layout:

Recall from our discussion of GT that the concept exploits advantages that accrue from the computerized classification and coding of part families to increase productivity for small lot manufacture. One of the advantages is in the layout of the physical facilities. GT layout takes a position between functional and line layouts providing some of the advantages offered by each basic type.

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