Understand SAP EWM – The purpose of wave management & resource management

Understand SAP EWM

The purpose of wave management & resource management

Note: This post belongs to the blog-series ‘Understand SAP EWM the purpose of wave management & resource management in SAP EWM. The purpose of these series of blog-posts is to explain the concept of the core features of SAP EWM in a simple way. It is intended to target EWM beginners and focuses on the basic understanding rather than the smallest details.

Before we start doing anything in our warehouse we receive different kind of requests to move specific objects from A to B. These requests might come from inside or outside our company and can be based on deliveries, stock transfers or posting changes. So it might be a request to move a given product from our warehouse to our end-customer or simply to move a pallet from reserve storage to the pick-face.
In SAP EWM we call these documents warehouse requests and for the matter of simplicity we will now concentrate on outbound deliveries as one representative group for these warehouse requests. So the delivery is our warehouse request and the items of our deliveries are our warehouse request items. First lesson learned – save the word: Warehouse request.
To make it understandable –
Imagine a big box of big balls with each big ball containing a number of small balls. The box is our request buffer, the big balls are our warehouse requests and the small balls are the warehouse request items:

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From now onwards we ignore the big balls as we (and EWM also) are only interested in the small ones – our warehouse request items.
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So what happens now in between the receipt of such requests and the actual execution on a RF, tablet, smartphone or any other device?
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Having theses warehouse requests in our EWM system we know now that we have to do something. Ok so far. As a first step we have to make a decision about when to do what. So basically out of everything that we have in our box we have to separate one part in order to define a load of work which is to be executed in a given time frame (start at a given point in time and complete at a given point in time). Try to think about a couple of smaller boxes into which we distribute the small balls based on their characteristics (recipient, type of products, physical area of the warehouse etc.). Each small box has a start and end time (and some more characteristics which we ignore for now):
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Each of these small boxes now defines a load of work for a given time frame. In EWM we call them Waves. Second lesson learned – save the word: Wave. Waves can be created based on so called wave templates which hand down times (e.g. start/cut-off/end time) and a couple of other attributes to the waves. In SAP EWM we find these templates based on the condition technique which is enabling us to consider any fields from our warehouse request header/item in order to find a specific wave template. So far so good. Now we do have our wave and need to decide who in the warehouse is going to do what? Not everybody or every kind of equipment should/can do everything due to technical preferences/constraints. However, all resources should be utilized in the most efficient way. For the following explanations we do only need one of our waves (boxes) created above:
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We split our wave now into smaller work packages which should later be assigned to resources, having the characteristics which are required to execute the tasks within the specific work package. In SAP EWM we call these executable work packages warehouse orders and they are created based on the warehouse tasks which in turn are created once our wave is being released. At this point in time we apply the so called warehouse order creation rules which represent the technical base to cut our total workload into the work packages. Third lesson learned – the wave release triggers the creation of the Warehouse Tasks based on the Warehous Request items and the Warehouse Order Creation Rules build Warehouse Orders based on the Warehouse Tasks. In easy words to make it sticky:
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