About Automatic Line Balancing

Automatic line balancing consists in balancing a group of operations from an initial system to a target system.

The top structure (that is, the first level of children) of the target system must comprise a single sequence of systems connected by a product flow.

In the figure below, if the global time of all operations in the initial system is 80 seconds, then the target system shows three balanced systems. With each system having a cycle time of about 30 seconds.

Automatic Line Balancing takes into account constraints defined between operations. In the figure above, the blue operation 2 precedes the orange operation 2 and this constraint is respected in the balancing result. The supported constraints are precedence constraints and product flows.

The initial system is the system that contains the unbalanced operations.

The initial system can be a workplan system or any other system type and it can contain any type of operation. It has no relationship with any resource in a resource layout.

The target system is the system that receives the balanced operations. It can be the same as the initial system.

The target system must be made up of general systems.

The target system has child systems connected through a single product flow. The product flow must not have any "Y" branches. Each child system can comprise a system structure that ends with leaf systems. A leaf system is a system with no child system nodes.

The target system can include operations that are not Transfer, Buffer, or Sink operations, see figure below.

After Automatic Line Balancing, all operations are balanced on the leaf systems of the target structure. If any of the existing operations were locked, they will not be moved by the automatic balancing.

The target system can have a substructure of systems. In the figure below, the second system Sb of the product flow has two subsystems Sb-1 and Sb-2.

After Automatic Line Balancing, the operations are balanced on the leaf systems Sa, Sb-1, Sb-2, and Sc, but not on Sb, since Sb is not a leaf system.

The initial and target systems must have a scope to the same item. This ensures a correct balancing of the operations assigned to the item, and that assignment links are maintained.

The initial and target systems must not have a scope to a resource structure. At the time when operations are balanced, there is no relation between systems and resources.

In any case, the planner intervenes before the resource assignment stage. The systems can be assigned to resources after the balancing stage.

Each system that can receive operations shares a common cycle time known as maximum cycle time.

The maximum cycle time is an Automatic Line Balancing parameter. Its value cannot be less than the maximum time of any operation to be balanced, nor can it be negative or zero. You can enter or edit the value in the Automatic Line Balancing dialog box when using the Minimum Number of Systems mode.

When you select the initial system, the Maximum Cycle Time is set by default to the longest operation time among its operations. You can specify an operation time in the properties of an operation, as Estimated Time.

After you select the target system, the Maximum Cycle Time is updated. Its value is now set by default to the longest cycle time among its systems. You can specify a cycle time in the properties of a system.

Automatic Line Balancing also considers the Time Mode specified in the properties of each operation.

You can balance operations based on a percentage of utilization of your resources.

The cycle time of each system in the target system is multiplied by the utilization percentage and used for balancing. This is useful, for example, to simulate activity when assembly stations cannot perform at full capacity.

You can enter the percentage value in the Automatic Line Balancing dialog box, when using the Minimum number of systems mode. This value cannot be negative nor zero. In addition, all systems in the target system must have a cycle time greater than zero.

You can allow balancing of operations that exceed the cycle time or utilization percentage.

These operations are balanced according to existing product flows and time constraints, and can overflow the system they are assigned to.

If you do not allow overflow, exceeding operations remain unbalanced.

Overflowing and unbalanced operations are flagged in the Automatic Line Balancing report. For more information, see Automatic Line Balancing Report below.

An operation can be locked using a Pin Operation contextual command to prevent moving it during automatic balancing.

The behavior of pinned operations for Automatic Line Balancing is as follows:

• When the initial and target systems have a common parent system, only the initial system's unpinned operations are moved to the target system. The initial system's pinned operations do not move.
• When the initial and target systems do not have a common parent system, all the initial system's pinned and unpinned operations are reinstantiated in the target system.

You can use the DELMSDCheckOperationMove_ID business logic to ensure that an operation is compatible with a system during Automatic Line Balancing.

This business logic enables you to allow or prevent balancing between right-handed and left-handed operations and systems.

For example, the figure below shows System A and System B (stations) that have subsystems SA Right/Left and SB Right/Left (working areas). You can use the DELMSDCheckOperationMove_ID business logic to ensure that only left-handed operations can be moved to subsystem SA Left.

The report provides a summary of balanced operations with their status and assigned system.

Once the Automatic Line Balancing is completed, the reports automatically opens in a dialog box. Operations are divided into three states:

Status	Status Explanation	Possible Messages in Report
Success	Operation successfully balanced without overflow	Operation successfully assigned. Operation successfully reassigned to same system. Operation successfully reassigned to different system.
Warning	Operation balanced with overflow	Operation has overflowed. Operation has overflowed and it has time greater than cycle time.
Error	Operation unbalanced	Overflowed operation not assigned. Overflowed operation not assigned as it has time greater than cycle time.