My reply from epicor support:
I am not sure what parameters you have selected to calculate the Manufacturing Lead time. Here is some information that might be of help:
Manufacturing Lead Time is the elapsed time from when production begins on a quantity to when the quantity is considered complete on the costing lot. This time includes how long it takes to acquire any constrained materials for the current assembly and how long it takes to manufacture subassemblies needed to create the current part. You can use the Manufacturing Lead Time Calculation process to automatically calculate lead time values; this process considers all the variables for manufacturing the complete part from beginning to end. However, you can override these calculated values and enter the number of days as an exception value.
Enter a Cumulative Time value. This value is the sum of the manufacturing lead time plus the material lead time. It incorporates the lead time of the longest constrained material requirement found on any of the sub-assemblies.
Enter a This Level Time value. This value is the time required to build the job cost quantity of the part; it assumes the required materials are available.
Plan as Assembly – Select this check box to indicate this material requirement is fulfilled from stock, but if not enough stock is available during the manufacturing lead time, it will be planned as a subassembly by the MRP process.
You can use the Manufacturing Lead Time Calculation process to calculate the manufacturing lead time for a single part, all parts, product group, or plant. Manufacturing lead time is the elapsed time from when production begins on a quantity to when the quantity is considered complete on the costing lot.
Menu Path: Production Management > Engineering > General Operations > Mfg Lead Time Calculation
To set up this process:
- Review the processing options. The As of Date defaults to today’s date. It defines the effective date of the revision.
- Click the Product Code drop-down list to select a product group.
- Click the Filter tab to specify parts and sites for processing. Individual parts can be selected. The plant defaults to the current plant but can also be changed to include multiple sites.
- To run the calculation, click Process on the Standard toolbar.
When the process starts, rough cut scheduling is used to calculate the lead time (in days) for the Costing Lot Size specified by the part planning parameters. Rough cut scheduling uses the Need By Dates and Lead Time Values on each material and operation to calculate how much time is required for each job to finish
its operations and gather its materials.
You can view the calculation values within Part Maintenance on the Parts > Sites > Planning sheet.
Within the Manufacturing Lead Time section, review the lead time fields. These values are either calculated by a process or entered manually. You directly enter these values by selecting the Manual check box.
• The Cumulative Lead Time field displays the lead time of the longest constrained material requirement(s) on all sub assemblies below the main parent assembly.
• This Level Time displays the time required to build the job cost quantity of the part. This value assumes all of the materials required for the assembly are available.