OM/U2 Topic 5 Line Balancing
Assembly line balancing operates under two constraints:-
- Precedence requirement
- Cycle time restriction
Precedence requirement: – It is physical restriction on the order in which operations are performed.
Cycle time: – Cycle time is the total time from the beginning to the end of your process, as defined by you and your customer. Cycle time includes process time, during which a unit is acted upon to bring it closer to an output, and delay time, during which a unit of work is spent waiting to take the next action.
Desired cycle time (Cd) = Total time available for production
Number of units to be Produce
Actual Cycle Time (Ca) =
STEPS IN LINE BALANCING PROCESS
- Draw and label a precedence diagram.
- Calculate the desired cycle time required for the line.
- Calculate the theoretical minimum number of workstations.
- Group elements into workstations, recognizing cycle time and precedence constraints.
- Calculate the efficiency of the line.
6. Determine if the theoretical minimum number of workstations or an acceptable efficiency level has been reached. If not, go back to step 4.
COMPUTRIZED LINE BALANCING
Line balancing by hand becomes unwieldy as the problems grow in size. Fortunately, there are software packages that will balance large lines quickly. IBM’s COMSOAL (Computer Method for Sequencing Operations for Assembly Lines) and GE’s ASYBL (Assembly Line Configuration Program) can assign hundreds of work elements to workstations on an assembly line. These programs, and most that are commercially available, do not guarantee optimal solutions. They use various heuristics, or rules, to balance the line at an acceptable level of efficiency. The POM for Windows software lets the user select from five different heuristics: ranked positional weight, longest operation time, shortest operation time, most number of following tasks, and least number of following tasks. These heuristics specify the order workstations. Elements are assigned to workstations in the order given until the cycle time is reached or until all tasks have been assigned.
- HEURISTIC LINE BALANCING
An efficient single-pass heuristic method capable of finding good solutions for the single-model deterministic line balancing problem is presented. The method involves four phases for simplifying a given problem, reducing its size and decomposing it into smaller subproblems when appropriate. The solution is then found by using combinations of various heuristic rules.