Date and Time Calculation for WOs

Use this document to learn how the calculation of date and time works for work orders. Check the steps that follow if the result is incorrect.

The start date, finish date, and release dates on planned WOs and WOs are calculated based on different rules.

Variants

The functionality has two main variants, controlled by the 'MO lead time method' on 'Item. Connect Facility' (MMS003/F).
- 0-Manual lead time
  No calculation takes place. Dates are kept as specified.
  
  Manually set lead times in 'Service. Open' (MOS300) or 'Item. Connect Warehouse' (MMS002), if acquisition code is 6, affect the duration of the work.
- 1-Automatic
  Lead time is calculated based on operation runtime.
  
  The setting in (MMS003) can be overridden using parameter '197 Manual override lead time method' in 'Work Order Type. Open' (MOS120). This allows a specific order type to behave as if the parameter is set to 0 in (MMS003).
- 2-Manually set lead time offset on operations
  The overriding parameter '197 Manual override lead time method' in (MOS120) can also be set to 2. This parameter enables manually set lead times on each operation to remain unchanged and not be recalculated when equipment calculation is performed. This way, you can set parallel operations by defining the same number of days before the finish date that each operation must start. For example, in Manufacturing, operation 1 starts 20 days before the finish date, operation 2 and 3 start 10 days before the finish date, and operation 4 starts 2 days before the finish date. The duration of each operation is controlled by the runtime through production days, similar to MO lead time method 1.
Parameter '080 Should maintenance limits affect start/finish dates' in (MOS120) controls if the WO must use forward or backward planning.
Transit time (SLAC) between operations is calculated if it is set up in 'Work Center. Enter Queue & Transit Time' (PDS020).
On the facility record in 'Facility. Open' (CRS008), you can define whether shift planning is used. If shift planning is not used, the time fields are not displayed on the orders.
Time zone handling is controlled using the F13 setting in most programs.

MO lead time method 0 - manual

Dates specified at order creation are retained. Operations are given the same date and time as the order header.

MO lead time method 1 - automatic

Note: If no record exists in (MMS003), automatic lead time is used.

Equipment calculation is performed automatically when you leave (MOS300) after editing or adding a service. You can also trigger the calculation manually using related option 21='Equipment Calc' in 'Service. Connect to Facility' (MOS301). The calculation is performed in the background through function program (PDS900) (Calculate DBF and leadtime).

The product or equipment calculation starts from the operations runtime or setup time, the capacity per person of work centers, and the utilization rate. Equipment calculation always starts from the last operation number and calculates how many days the operation takes. This calculation results in a value for 'Production days' and 'Lead time offset'.

Lead time offset is the number of days from the finish date that the operation must start. For each previous operation, the lead time offset is added so that the first operation gets the total number of days that is required for the job.

Note: Transit time is set up on local facilities and is not included in the calculation if the service is defined on a consolidated facility.

Work center capacity

Capacity is created based on the settings on the work center, capacity, number of workers, and utilization rate. Capacity is also based on the employee calendar in 'Employee. Connect Calendar' (CRS510) for the employees connected to the work center in 'Person. Open' (CRS530). The method is specified in 'Settings - Capacity Requirements Planning' (CRS786).

If shift planning is activated in (CRS008), and shift schedules are set up in 'Shift Pattern. Open' (PDS033) and 'Shift Pattern. Open Lines' (PDS034), and shift models are set up in 'Shift Model. Open' (PDS031) and 'Shift Model. Open Lines' (PDS032), daily capacity is created based on the shift pattern and the system calendar in (CRS900).

If the shift is not working on weekends, records in the daily capacity exist only for days that are set to 'General capacity' in 'System Calendar. Open (CRS900). If the shift is set up for 7 days but has no working time for weekends, the days are created in the daily capacity, but no capacity is available. If a lunch break is defined in the shift pattern or two real shifts are defined, two records are created for each day.

If shift planning is not used, daily capacity is not used. In this case, the general capacity days in (CRS900) are used as working days.

Planned WOs

Automatic lead time calculation with shift planning

When a planned WO is created manually in 'Work Request. Open' (MOS170), 'Maint CO. Quick Entry' (COS130), 'Maintenance Customer Orders. Open Line' (COS101), 'Work Request. Quick Entry' (MOS185), or through service requirements planning (SRP), 'Work Request. Create Work Order' (MOS912) creates or recalculates the dates.

Depending on parameter '080 Should maintenance limits affect start/finish dates' in (MOS120), you can specify and consider start date or finish date.

The planned WO header, operations, and material lines are created. Each operation is then analyzed. The estimated time is retrieved, capacity is checked for each day in 'Work Center. Update Daily Capacity' (PDS016), and the number of required days is calculated.

For each operation, the dates in 'Work Request. Open Line' (MOS171) are updated for operations and connected material. The time represents the start and end time for the shift in (PDS016).

Note: The exact time of the day when the operation is finished is not considered, as it is for released WOs.

When operations are changed, added, or deleted in (MOS171), the dates are recalculated in (MOS912) in the same way as when operations are created. The dates are also recalculated when the API transactions AddOp, ChgOp, or DelOp in MOS170MI are used.

Automatic lead time calculation without shift planning

In this scenario, there are no fields with time of the day to use and no daily capacity in (PDS016). The calculation is based only on days with general capacity in (CRS900). Apart from this exception, the functionality works in the same way as automatic lead time calculation with shift planning.

Note: For subcontracted operations, runtime is not used. Instead, use the field 'Production days'. Include runtime and possible shipping or inspection lead time. You can edit the field in (PDS002) on the service, in (MOS171), or in (MOS101) on the WO.

Released WOs

During release, and when operations are changed, added, or deleted in 'Work Order. Open Line' (MOS101) during rescheduling, the dates and time are calculated through function program (MOS905).

The biggest difference from planned WOs is that time of the day is considered on a detailed level. If an operation takes three hours and a specific start or finish date is defined, the operation runs between 08:00 and 11:00 if the work center shift starts at 08:00.

This behavior is applicable if shift planning is activated. If shift planning is not used, only the dates are calculated, the same way as for planned WOs.

What can go wrong

Incorrect capacity

Verify whether the capacity for the work center is generated for the current year.
If not, regenerate the capacity in 'Work Center. Change Capacity' (PDS015) or (PDS016).
Verify whether the general capacity is set correctly.
Check the system calendar and review weekend settings.
Verify whether the shift pattern date is expired.
Check (PDS034).
Verify whether the shift model lines are correct.
Check (PDS032).
Verify whether capacity is based on the work center capacity or the employees in the work center.
Check (CRS786).

If capacity is based on employees, check the employee calendars for all employees that are connected to the work center, using (CRS530) or (CRS510).

Incorrect dates on planned WO, WO, or operations

Verify capacity settings as described for incorrect capacity issues.
Verify whether the transit time is correct.
Check the setup in (PDS020) for the local facility. Verify the transit unit of measure and overlap code in 'Work Center. Open' (PDS010) and 'Product. Connect Materials/Operations' (PDS002). Check the utilization rate in (PDS010).
Verify whether forward or backward planning is used.
Check parameter 080 in (MOS120).
Verify the setting for 'MO lead time method' in (MMS003).
If no record exists, automatic lead time is used.

Check parameter '197 Manual override of lead time method' in (MOS120).
Verify that the time zone settings using F13 in WO programs are correct.
Verify whether 'Production days' is defined for subcontracted operations to act as runtime.

Incorrect dates or time on the MCO lines or planned WO connected to an MCO

Verify that the time zone settings using F13 in MCO programs are correct.