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Production Lead Time and the Relational Dependence on the Load Calculation

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MRP is a calculation process that looks at the requirements of products and calculates the necessary production/purchasing schedule considering the production/purchasing lead time of each product. The product site record is located Common data, Product, Product-site. MRP related settings are found on the Planning tab. The Lead Time block shows various lead times which can be entered for the Product at the site level. Typically, the settings on this block determine when to replenish inventory. Production lead time is the projected time needed from the work order release to the work order completion. There is a relational dependence between the Production lead time setting and the Load calculation field. Load calculation is the duration in weeks from the calculation start date for which a load calculation must be executed. 

If the Load Calculation field is zero, the Production lead time options are Product lead times and Always Routing lead times. Planning will consider either the Product lead time or the Routing lead time. Lead time calculations from routings significantly increase processing times. When a routing is not obtained from a product, the default data is obtained from the product-site, planning tab record.

The routing lead time is made up of the Setup time and the Run time (Operational time) set in Routing Operation Detail.  This is found under Manufacturing, Technical data, Routings, Routing management (GESROU). Select a Routing, click on the Routings tab, select the Action card on an operation line, click Routing operation detail. The Routing lead time is set up under the Charged time block. Lead time calculations from routings significantly increase processing times. When a routing is not obtained from a product, the default data is obtained from the product-site, planning tab record.

If the Load Calculation field not zero, the Production lead time options are Routing/product lead times and Always routing lead times. Planning will consider the Products lead time and Routing lead time (the greater of the two is usually used) or the Routing lead time. Lead time calculations from routings significantly increase processing times. When a routing is not obtained from a product, the default data is obtained from the product-site, planning tab record.

The routing lead time is made up of the Setup time and the Run time (Operational time) set in Routing Operation Detail.  This is found under Manufacturing, Technical data, Routings, Routing management (GESROU). Select a Routing, click on the Routings tab, select the Action card on an operation line, click Routing operation detail. The Routing lead time is set up under the Charged time block. Lead time calculations from routings significantly increase processing times. When a routing is not obtained from a product, the default data is obtained from the product-site, planning tab record.

  • in reply to Julien Patureau

    Thank you for this information. We wish that this setting was at the product or product-site level so that, for products that do vary significantly with volume, they could be routing-driven while the rest were treated generically. Having this set at the site requirements parameters level means that all are treated the same for that site, and there is little flexibility there. While MRP theory encourages us that accurate lead times are less important than requirements dates, this would contribute significantly to the leveraging of MRP as a production scheduler. Otherwise, much work is required to adjust timing according to the reality of the floor.

  • Please don't forget when you are using the product lead-time, you have a ponderation of lead-time based on the quantity released/suggested. Basically more you produce longer last your production process. 

    To do so, you need to set an EOQ (that will be used as reference quantity for the production lead-time) and the reduction factor (field MIC). The field help is very well done to understand in detail the use of this ponderation factor.

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