The manufacturing lead time calculation can be done for the current and future revisions and for all routing alternates for a part. The calculation considers setup, move, operation times, efficiency factor and overlap entered for the operations. The system also considers the information about queue time and shifts such as the number of work hours per day from the work center where the operation is performed. You can run the calculation for one part at a time or for all parts in a specific site. Optionally the inventory part can be updated with the lead time calculated for the default routing alternate (*) and the current revision.
The lot size on which the lead time calculation is based, is normally the standard lot size specified on the inventory part. It is possible to simulate lead time for other lot sizes using Calculate Lead Time from the Routing, Routing Alternate or Routing Alternates pages.
Manufacturing lead time calculations can be based on machine time, labor time or the maximum of machine and labor time. The work center capacity used in the calculation can be either the demonstrated capacity or the average capacity as specified on the work center. The average capacity represents the projected usage based on the current work center parameters. The demonstrated capacity represents the past actual usage.
Manufacturing lead time is used in several places like in IFS/Material Requirements Planning (MRP) and IFS/Master Scheduling (MS) when creating supply.
The fixed lead time is the time that does not vary based on the lot size. For a routing alternate having no parallel or overlapping operations, the fixed lead time is the sum of setup time, transport time and queue time for all operations.
The variable lead time is the time that is needed for each unit produced. For a routing alternate having no parallel or overlapping operations, the variable lead time is the sum of machine or labor time for all operations.
For parallel operations only the operation that takes the longest to complete will be considered when calculating the fixed and variable lead time. For an operation that overlaps with the previous operation the contribution depends on the overlap and the difference in run time between the operations.
The formula below is used when calculating manufacturing lead time. The formula does not cover calculations for operations with overlap. For parallel operations only the operation with the longest lead time will be considered.
Where:
The routings in the below examples only include machine time. Unit for run time is in hours/unit and the overlap is defined in units. The lot sizes for all examples are five (5) pieces.
Work Center
Work Center | Work Center Description | Queue Time | Average/Demonstrated Capacity |
A1 | Assembly | 0 | 8 |
P1 | Painting | 0 | 8 |
T1 | Testing | 0 | 8 |
Routing - Without Overlap
Op No | WC No | Setup | Run Time | Efficiency | Transport Time | Parallel Operation | Overlap | Setup Inside Overlap |
10 | A1 | 2 | 1 | 100 | 1 | No | 0 | No |
20 | P1 | 1 | 2 | 100 | 0 | No | 0 | No |
30 | T1 | 1 | 1 | 100 | 2 | No | 0 | No |
Fixed Lead Time: 7h, Variable
Lead Time: 4h, Total Lead Time: 7h + (4h *5 pcs) = 27h
Routing - With Overlap (Overlap Units= Units)
Op No | WC No | Setup | Run Time | Efficiency | Transport Time | Parallel Operation | Overlap | Overlap Units | Setup Inside Overlap |
10 | A1 | 2 | 1 | 100 | 1 | No | 0 | Units | No |
20 | P1 | 1 | 2 | 100 | 0 | No | 1 | Units | No |
30 | T1 | 1 | 1 | 100 | 2 | No | 1 | Units | No |
Fixed Lead Time: 7h, Variable Lead
Time: 2h, Total Lead Time: 7h + (2h *5 pcs) = 17h
Comment:
Routing - With Overlap (Overlap Unit = Percent)
Op No | WC No | Setup | Run Time | Efficiency | Transport Time | Parallel Operation | Overlap | Overlap Unit | Setup Inside Overlap |
10 | A1 | 2 | 1 | 100 | 1 | No | 0 | Percent | No |
20 | P1 | 1 | 2 | 100 | 0 | No | 20 | Percent | No |
30 | T1 | 1 | 1 | 100 | 2 | No | 20 | Percent | No |
Fixed Lead Time: 5h,
Variable Lead Time: 2.4h, Total Lead Time: 5h + (2.4h *5 pcs) = 17h
Comment:
Routing - With Overlap and Setup Inside Overlap
Op No | WC No | Setup | Run Time | Efficiency | Transport Time | Parallel Operation | Overlap | Setup Inside Overlap |
10 | A1 | 2 | 1 | 100 | 1 | No | 0 | No |
20 | P1 | 1 | 2 | 100 | 0 | No | 1 | Yes |
30 | T1 | 1 | 1 | 100 | 2 | No | 1 | No |
Fixed Lead Time: 8h, Variable
Lead Time: 2h, Total Lead Time: 7h + (2h *5 pcs) = 18h
Comment:
In the examples above the work centers are assumed to have no queue time. If queue time would have been defined, that time will be added as a fixed lead time.