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:

Understanding SAP EWM wave management and resource management_1
From now onwards we ignore the big balls as we (and EWM also) are only interested in the small ones – our warehouse request items.
Understanding SAP EWM wave management and resource management_2
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:
Understanding SAP EWM wave management and resource management_6
Fine. We know what we have to do in a given time frame (remember the term Wave) and we know what we want to be executed by one resource at a time (remember the term Warehouse Order). In the next step we need to make sure that the most urgent work packages are to be executed before the less urgent ones and we need to make sure that work packages which require specific handling are assigned to resources which are able to execute specific handling. To achieve this we make use of the Resource Management features of SAP EWM. First we assign our warehouse orders to different groups. In EWM we call these groups Queues. We are usually working with many different queues (e.g. due to the fact that the warehouse orders require different handling or due to the fact that some have to be processed in one area of my warehouse and others in different area).
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Next we bring these queues in one or more sequences and assign one sequence of queues to one group of resources. The same queues might follow sequence A for resource group X and sequence B for resource group Y:

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Now we finally know which resources will have access to which work packages and we know which group of work packages is going to be processed at first (to reduce the complexity here we will ignore how the warehouse orders are sorted within the queues). Still we might not know whether all resources belonging to the given resource group are able to process all warehouse orders from the given queue. To implement the required rules here we use so called Resource Types in SAP EWM. Every SAP resource working in our warehouse (‘Resource’ either in terms of a human being or in terms of a device operated by a human or autonomously) will be assigned to one resource type. This ‘type’ hands down the ability of handling specific types of handling units and accessing types of bins to the resources. The settings are evaluated against each warehouse order (remember our work packages) which should potentially be processed. Imagine it happening like this (technically not 100% correct but good approach to understand the concept):
Understanding SAP EWM wave management and resource management_9

That’s it. Not that difficult I think!
So next time we open our RF, tablet, smartphone or whatever we are using to work in our warehouse we will know now why the given request to move stuff from A to B is shown on our device and how it got there.

Note: As always, there are some exceptions and the terms mentioned above are not always used by the given definition (e.g. warehouse orders in the context of Pick & Pass process). The purpose of this article is to communicate a broad understanding of the main concept behind the given objects. Details & exceptions will be described in further posts!

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