Calculating Manufacturing Lead Time

General Information

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 the Calculate Lead Time right-click option in the Routing Alternates window.

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 Requisitions Planning (MRP) and IFS/Master Scheduling (MS) when creating supply.

Fixed and Variable Lead Times

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.

Formula for Manufacturing Lead Time calculation

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

Setup time = Time entered on each operation of the routing.
Run time = Time entered on each operation of the routing.
Lot Size = Default value is the standard lot size, can also be entered manually in the Calculate Manufacturing Lead Time dialog box.
Operation efficiency = Time entered on each operation of the routing.
Work Center Capacity = The average or demonstrated capacity entered on the work centers.
Transportation time = Time entered on each operation in the routing.
Site Manufacturing Calendar Hour = Average number of working hours on a work day for the site manufacturing calendar.
Queue time = Time entered on the work centers
Work Center Calendar Hour = The number of working hours on the work center on the day the calculation is performed.

Sample Scenarios

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.