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Sequence operations

From time to time, you may need to re-plan your scheduleThe name of the default schedule file. It also refers to the production schedule represented by the sequencer Overview window in Graphical Planner.. You can sequence operations to accommodate your changing needs. Sequencing allocates operations onto resources in the sequencer.

Methods of sequencing

The Graphical Planner offers three methods of sequencing operations which you can use to suit your needs:

Forward sequencing

This method automatically allocates operations onto the appropriate resources in the sequencer. The application looks at the earliest start date and time of the operations and positions them from that point onwards.

The advantage of forward scheduling is that work is placed in the factory as soon as possible, using resources and ensuring the shortest possible delivery time.

However, it could mean that there is more work in progress and finished goods are placed in stock earlier than needed. This could cause practical issues such as a strain on warehouse storage, if space is limited.

Care needs to be taken when setting products up in the Bill of Materials module if there are sub-assemblies.

Backward sequencing

This method starts at the due dateThe date by which an invoice should be paid. This is used for the Aged Creditors or Aged Debtors reports. of the works orderThe authority to produce a part using the components specified on a BOM and the process specified on the routing., based on the customer delivery date. It applies to any safety planning time specified during MRPMaterials Requirements Planning (MRP). MRP recommends purchase orders, transfers and work orders to balance supply and demand.. This is the date it sets as the target date for the completion of the last operation of the works order.

Based on the routing and available capacity, it then works backwards, calculating when that operation should start in order to achieve the target date. The previous operation is then calculated by working backwards. This is repeated until the start of the first operation is calculated.

The advantage to backward sequencing is that the finished goods inventory is kept at a low level. This could potentially reduce the risk of write-offs, if changes are made to the demand.

On the other hand, if the due dates are too far in advance, and process times are short, the sequencer will leave resources idle until it is time to start. Also, if due dates are near, or process times are long, there may be insufficient time to backward sequence the work on time. Therefore, operationsThe labour, machine and tool processes required to manufacture an item. would remain unallocated.

Bi-directional sequencing

This method is very useful in identifying bottlenecks and rescheduling unscheduled operations around them. This method allocates operationsThe labour, machine and tool processes required to manufacture an item. on the sequencer around a calculated bottleneckResources with a critical impact on the schedule. Calculated by Graphical Planner using the waiting time of jobs to be processed on the resource. Those with a long queue of work are likely to be identified as bottlenecks. operation. Operations before the bottleneck are backward sequenced from its start time. Operations after the bottleneck are forward sequenced from its end time.

Operations can be reallocated to resources that may otherwise have remained idle due to the disruption. It aims to ensure that the Sequencer prioritises work before the bottleneck resource. This is to minimise potential delays.

This method may also be used to schedule around a fixed operation, which may only be carried out at a specific time, e.g. a subcontractor booked to paint an item on a Tuesday morning.

Note: When applying bi-directional sequencing, you should be aware of the potential impact on sub-assemblies. You can highlight top level tags to see the relationship between a product and its sub-assemblies. See Locating orders and operations.

Each method allows Graphical Planner to govern the order in which the sequencer processes the operations. Each method can be processed by priority, reverse priority, due date, or order file. These processes are specific to sequencing all operations. Depending on the nature of your business, you may favour one method over another. Or you can use any method depending on the circumstances.

To sequence operations

Select what you want to do:

To sequence forwards
  1. Right-click an order in the Unscheduled Operations window.

    2. An options menu appears.

  2. Select Place On Planning Board > Forward, All Operations.

    3. All the operations assigned to the order are allocated onto the Overview, starting from the earliest start date.

    Note: The calendar is displayed in the Overview window.

To sequence backwards
  1. Right-click an order in the Operations window.

    2. An options menu appears.

  2. Select Place On Planning Board > Backward, All Operations.

    3. All the operations assigned to the order are allocated onto the Overview, starting from the order's due date.

    Note: The operations in the sequencer are not displayed in backward order. This is because resources are displayed in alphabetical order, rather than the order of the actual manufacturing process.

To sequence bi-directionally
  1. Forward sequence work from the Unscheduled Operations window.

    2. Click the Generate Schedule  icon on the Sequence toolbar.

    All of the allocations appear forwarded on the Overview window.

  2. Highlight the bottlenecked operations.

    3. Select the drop-down beside the Locate  icon on the Main toolbar and select the Highlight Bottleneck Operations  icon.

    Those operations causing the bottleneck are highlighted.

  3. Lock the highlighted operations.

    4. Select the drop-down beside the Locate icon and select the Lock Highlighted Operations  icon.

  4. Assess the problem.
  5. Unlock the bottleneck.

    6. Select the drop-down beside the Locate icon and select the Highlight Bottleneck Operations  icon again. This clears the selection.

    All operations revert to active mode in the Unscheduled Operations and Overview windows.

  6. Remove the unlocked operations from the schedule.

    7. Click the Remove Operations from Schedule  icon on the Sequence toolbar.

    The bottlenecked operations remain locked on the relevant resources in the Overview.

  7. Bi-directionally sequence the unscheduled operations around the locked operations.

    8. Select Sequence > Bi-Directional Sequence for All Operations > Bi-Directional By Priority or Bi-Directional By Reverse Priority or Bi-Directional By Due Date or Bi-Directional By Schedule File Order.

    The operations that contain a bottleneck are identified and the operations are reallocated around the bottleneck. Any proceeding operations are sequenced with a higher priority.

    Note: Not all operations may have been reallocated.

  8. Forward sequence any remaining unscheduled operations.

    9. Click the Generate Schedule  icon on the Sequence toolbar.

    All of the allocations appear forwarded on the Overview window.

  9. Repair the schedule.

    10. Click the Repair Schedule  icon on the Sequence toolbar.

    Any errors in the schedule are automatically repaired.

  10. Click the Save  icon on the Main toolbar.

To record why some operations remain unallocated after sequencing

After sequencing, some operations will remain unallocated in the Unscheduled Operations window.

  1. Right-click a finished product on the Unscheduled Operations window.
  2. Select Reason not Allocated.

    3. The reason will be shown in a pop-up window. If the reason is that the resource cannot be fitted into the plan before the due date, you must extend the resource's capacity. See Analysing late or at risk orders and operations.

  3. Click OK.
See also

Other tasks

View operation details

Edit operation details

Edit operation details

Place operations

Unscheduling operations

Lock and unlock operations

Analysing late or at risk orders and operations

Locating orders and operations

Reference

The Bill of Materials module

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