Factivity's John Leibert discusses the two general methods of using an APS and outlines the 3 critical prerequisites necessary to add an APS system to your operation.
Over a half century ago, MRP (Materials Requirements Planning) was first used by Black and Decker. Not much has changed in this logic designed to calculate (plan) material lead-time requirements. In essence, this logic is basically using inventory levels and estimated "lead time" to determine material replenishment quantities (purchase orders) as well as estimated completion time of production orders (schedules).
Many things have changed in the last 50 years regarding how manufactures go about planning and scheduling production of pieces/parts/items yet many production facilities still believe that using MRP as a tool to schedule production is appropriate. It is not. One can find several major faults with this style of planning.
The first major problem with MRP systems is the integrity of the data. That is, MRP systems often plan production schedules using "fixed" production "lead times." This erroneous data field is usually found at the part master level. However, as everyone knows, lead times are dynamic and are subject to variations in demand and changing floor constraints.
The other major drawback of MRP is that it fails to account for work center capacity constraint in its calculations. And any effective production schedule must be constrained to that realistic level or the results will be misleading.
The ability to accurately schedule production is greatly enhanced by the use of finite constraint based scheduling logic and even better yet when this logic is also is aware of the material inventory levels. This functionality is the essence of an Advanced Planning and Scheduling System or APS. APS is a general component part of an overall Manufacturing Execution System (MES) approach to advanced Shop Floor Control.
MES collects data from the factory floor and provides metrics needed to implement lean manufacturing practices. The system monitors equipment availability, performance and quality to visually display Overall Equipment Effectiveness (OEE) in real-time and integrates fully with your ERP.
Black Box vs. Value-Add
There are two general methods of using an APS. Some companies prefer to set-up "rules" in the APS. These rules emulate what a good Production Planner would try to accomplish when evaluating MRP data. This is known as a "Black Box" approach and can run unattended once implemented. It produces a new updated schedule at predetermined times. This approach has its value in saving expense personnel (scheduler) time while still delivering a realistic schedule based on multiple capacity constraints (machine output, personnel, tools, etc.), inventory levels and customer demand.
Another approach is to use the Black Box schedule as a starting point and from it allow a knowledgeable person to Value-Add the schedule. For example, finite scheduling will not infinitely (and inaccurately) overload work centers like MRP. The APS will constrain on the work center capacity so when the work center is projected to be overload the APS logic will push the schedules out in the future and project "late" orders. With this knowledge a person "value-adding" the APS output can simulate, for example, expanding the capacity available with additional overtime schedules that will minimize lateness with the least amount of overtime dollars.
Another value-added example might relate to optimizing the setting-up of machines based on a specific line-up of parts to be produced at that machine. An optimized line-up of parts can, under APS rules, minimize set-up times by scheduling certain characteristics of parts together to automatically create a scheduling sequence that takes advantage of the same die/tool, similar raw material components and/or mixes, optimize size/color changeovers, etc. However, having someone evaluate the possibility of breaking the rules (value-adding the schedule) on an as-needed basis to help improve the optimization can save substantial time and money.
Before making an APS decision and prior to considering the two approaches outlined above are three critical basic steps that must be taken prior to installing software. These three basic prerequisites must be in place to make a successful APS implementation. These perquisites are as follows:
A two way integration with the MRP system to allow the APS a method of obtaining part and production information as well as the ability to send back "due date" changes.
An automated factory floor data collection system, or better yet, MES system that can provide up-to-the-minute updates of floor activities such as production reporting during the shift(s).
A consultant that not only understands the APS product features/functions but has experience with MRP logic/systems and has knowledge from prior APS/MRP integrations.
Want more information? Click below.