Scheduling Strategy Window
Unless a default scheduling strategy has been set, the Scheduling strategy window is shown each time orders are scheduled:
The settings in this window define how the selected orders and operations are scheduled.
Orders being scheduled
List of order-numbers of the orders you are about to schedule/reschedule. The order numbers are separated by semicolon, and would look like this:
Order-1; Order-2; Order-3
Direction and start/end of scheduling
Option 2 to 4 are used to select the scheduling direction and when the orders should start/end.
The strategy used when scheduling orders or operations.
The following scheduling strategies are available:
- Forward from material date (limited or unlimited capacity) : Schedule the orders forward setting the start time of the first operation of each order to when the material is ready for the order.
- Forward from NOW (limited or unlimited capacity) : Schedule the orders forward setting the start time of the first operation of each order to now.
- Forward from custom date (limited or unlimited capacity) : Schedule the orders forward setting the start time of the first operation of each order to the custom date entered in the *Date*-field.
- Forward from last operation (limited capacity) : Schedule the orders forward, setting the start time of the first operation of each order to the finish time of the operations resource last operation.
- Backward from custom date (limited or unlimited capacity) : Schedule backwards from the last operation of the order. setting the end date of the last operation to the custom date entered in the *Custom Date*-field.
- Backward from Due date (limited or unlimited capacity) : Schedule backwards from the last operation of the order. setting the end date of the last operation to the due date of the order.
- No Scheduling : Leave the operations as they are currently scheduled. If the order is new, or not previously scheduled, each operation is placed at the current time on the first resource of the operations available resources.
Select a strategy in the list and see a description of the strategy by selecting the “Description” tab.
The strategy filter is used to narrow the list of available strategies. You can choose to show only forward or backward strategies or all strategies.
With Minimize lead time enabled, the order is initially scheduled according to the strategy selected. Immidiately after a bottleneck sort is carried out in the opposite scheduling direction, from the latest (forward scheduling) or earliest (backward scheduling) operation(s) found during the initial scheduling. This will ensure a reduced lead time of the production order, where bottleneck resources will impact how early or how late the order is scheduled to start. Reducing the order lead time results in reduced work in progress and also this will create “white spaces” where other priority orders may be scheduled.
The picture above illustrates results from a forward scheduling from NOW, respectively without and with the minimize lead time option enabled. Notice that the scheduled end is the same, but earliest operations are scheduled to start later, compared to the without case.
If Minimize lead time is used on a backward scheduling strategy, the start time of the order is the same as scheduling without. The difference in that case is a potentially earlier scheduled completion date of the order.
The custom date field is used when strategy 4 (Forward from custom date) or 6 (Backward from custom date) is chosen. The date entered is used as start or end date according to if a forward or backward strategy is chosen.
Common Scheduling Settings
Option 5 to 11 are common scheduling settings visible in the Settings-tab. these settings apply to both forward and backward scheduling strategies.
External dependencies are defined as sub order dependencies and material transaction dependencies
There are several strategies to handle external dependencies. Based on the following example with an orange order having sub order constraints to the green and the red order:
The orange order is scheduled forward from 8:00, the different strategies will have the following effect:
|The orange order is scheduled forward from 8:00 as if the green and red orders did not exist (breaking the sub order dependency!)
|All sub order constraints are respected (no red lines) but not rescheduled!
|Schedule direct dependencies:
|Direct dependencies are determined by the scheduling direction. If forward scheduling is used, all external constraints going out of the selected orders are rescheduled. As seen, this results in the red order being rescheduled. The green order is not rescheduled since it is not directly dependent on the orange order being scheduled forward!
|Schedule complete network:
|In this strategy all external dependencies (both forward and backward) are rescheduled as seen in the picture.
Limited capacity means that ROB-EX schedules the activities in the order with no overlap to other activities.
Unlimited capacity means that ROB-EX schedules the activities in the order no matter if there is overlap with other activities.
Limited capacity strategy takes into consideration if resources are defined as unlimited capacity under Resource scheduling settings”. If limited capacity strategy is selected, this strategy will be used for all resources except resources that have been set as unlimited capacity. An example of an resource with unlimited capacity is Subcontractors. Often they can be considered as unlimited capacities, while the company’s own resources has limited capacities.
If set, the ROB-EX will respect the material and delivery dates on the individual operations.
If a forward strategy is chosen, ROB-EX respects the material-dates of each operation.
If a backward strategy is chosen, ROB-EX respects the delivery-dates of each operation.
How this option works depends on if the operation is scheduled on a resource group or a simple resource:
Operation scheduled on a resource-group
- Option set: The operation will not move to another resource!
- Option NOT set: Other resources in the resource-group will be considered for the operation.
Operation scheduled on a normal resource
- Option set: The operation will not move to another resource!
- Option NOT set: The operation will not move to another resource unless option is set.
If this option is set, ROB-EX will try to move the operation to the best resource available for the operation.
NOTE: The best resource is chosen based on the scheduling settings of the resources available for the operation.
NOTE: This option is disabled if Stay on resource group is enabled!
This will allow sub-operations to change resource while planning.
When planning backward avoid that operations are planned before now.
WARNING: If set, already started operations will be rescheduled.
If this option is set, the scheduled operations/orders are validated afterward scheduling. If warnings or errors where found they are shown in a log-window.
The following validations are performed:
- Start before now: When scheduling backwards, and the initial operations are scheduled after the current point in time, a warning is shown if some operations are scheduled prior to the current point in time.
- Delivery dates: If a operation ends after it’s delivery-date a warning is shown.
- Material dates: If a operation starts before it’s material-date a warning is shown.
- Synchronization errors: If for some reason it was impossible to maintain a synchronization between some operations a error is shown.
With this setting enabled, the scheduling algorithm will, in addition to the normal capacity scheduling rules, search forward for the first point in time where all BOM-line constraints are fulfilled. This will ensure that operations are not scheduled where consuming BOM-line requirements are unfulfilled. And operations with producing BOM-lines are not scheduled where the maximum warehouse space is exceeded.
Note that “All BOM-line constraints” means all BOM lines with master material” setting “Use in planning” enabled.
If the BOM constraints are never met for one or more BOM-lines, in the horizon specified with setting “Horizon in days”, the operations will be scheduled forward from the latest operation consuming the same material and warehouse (regardless of what resource these other operations are assigned to). I.e. the rules will “intelligently” suggest from what date these “failed orders” must be scheduled – in order to avoid that they “steal” material from already scheduled orders. A warning message is sent also to the log-viewer when this happens.
From ROB-EX Scheduler 220.127.116.115/18.104.22.168 the “failed operations” will never be scheduled forward from a date being later than the end date+time of the “Horizon in days” window. I.e. if “Horizon in days=10”, you schedule Forward from Now and no capacity is available in that time window, then operations with unfulfilled requirements will be scheduled forward from Now+10 days (note that limited capacity constraints may cause the operation to still be scheduled to a later date in time than the 10 days from Now). For prior versions, operations will be scheduled after the latest operation consuming the same material and warehouse, regardless if this is several month later.
If min/max stock levels are defined those will also be considered. E.g. if the min safety stock of material M1 is set to 1000 pcs, then operation O1 consuming 500 pcs. of M1, will search forward in time until both capacity is available and the total stock level is 1500 pcs. or above. If no min stock level is specified, it is assumed to be 0. If no max stock level is specified, then the storage capacity is assumed to be infinite.
Read more about the BOM scheduling settings you can specify to fine-tune the forward BOM scheduling.
Note: This option is only supported with a FORWARD planning strategy – for backward strategies this option is disabled! Backward planning with BOM is not supported, since the tool would not be able to cope in an automatic way, with a situation where an operation is backward scheduled at time T1 consuming material X. Another operation already located later at time T2 would now suddenly not have enough stock of material X.
If this option is set, the scheduler will try to add operations to the first campaign, according with the scheduling strategy, where the operation is allowed to be added (for more info see How to use Campaigns) and there is enough available quantity left.
Important: Campaign scheduling will only have effect on Resource with the “Use in campaigns”-setting enabled.
Default Scheduling Strategy
Option 15 enables or disables the use of a default scheduling strategy.
Option used to set a default scheduling strategy.
If there is no check mark in “Define as standard” ROB-EX will show the scheduling strategy window every time an order is scheduled.
If there is a check mark in “Define as standard” ROB-EX will use the strategy and settings entered at the time the “Define as standard” check mark was set.
If you don’t want to see the scheduling strategy window each time you schedule a order you can use a default scheduling strategy. This is enabled by putting a check mark in the box next to Define as standard.
If you at a later time want to disable the default scheduling strategy it is done through the menu Functions -> Settings -> Scheduling strategy, which brings up the scheduling strategy window. Here you can remove the check mark in the box next to Define as standard.
|Enable Default Scheduling Strategy:
|In the menu choose Functions->Settings->Scheduling strategy. Choose the settings for the default scheduling strategy and put a check mark in the box next to Define as standard.
|Disable Default Scheduling Strategy:
|In the menu choose Functions->Settings->Scheduling strategy. Remove the check mark in the box next to Define as standard.