What's the difference between WMS and WCS …. and WES, PLC, and MFC?
The world of warehouse management and automation control is full of abbreviations and definitions. And it is easy to get confused by the contradicting descriptions of capacity and functionality in different types of systems. In this blog post we will try to iron out some of the confusion and answer the question; what do I really need to run my warehouse?
Photo: Consafe Logistics.
Ok, let’s start to de-tangle this mess. First we must define the different levels we need to control our warehouse with software systems. In an average-sized warehouse, with both automated and manual picking, we find two basic levels of control; Machine control and Business logic. We can consider these two as below and above the line (as shown in the illustration below).
The purpose of the systems below the line is to control and optimize the automation equipment, individually and together, while the systems above the line adds the business dimension and optimizes warehouse operations in relation to type of goods, deliveries etc. To put it simple, Machine control is all about HOW while the business logic level focuses on WHAT.
SOFTWARE SYSTEMS FOR MACHINE CONTROL
Depending on the set-up three different levels of machine control systems can be needed in an automated warehouse. An individual piece of automation equipment, e g a crane or conveyer is controlled by a rugged computer called a programming logic controller (PLC) or programmable controller, while a system for material flow control (MFC) connects a group of automation equipment from the same supplier, e g a number of cranes.
The highest level of machine control in an automated warehouse is run by a warehouse control system (WCS). Much like a “traffic cop”, the WCS is responsible for keeping everything running smoothly, maximizing the efficiency of the material handling systems. It provides a uniform interface to a broad range of material handling equipment such as AS/RS, carousels, conveyor systems, sorters, palletizers, etc.
SOFTWARE SYSTEMS FOR BUSINESS LOGIC
In most warehouses operations are run with a combination of automated and manual processes. To avoid isolated “islands of automation” you need software systems based on business logic, to optimize all activities in the warehouse, both manual and automated, in relation to type of goods and delivery priorities.
One type of system used as intermediate software between machine control and manual resource planning is the warehouse execution system (WES). WES first emerged as a hybrid system with specific WMS functionality with Warehouse Control system (WCS) functionality, for warehouses with advanced automation solutions.
A warehouse management system (WMS) has the same general function, but with more capabilities towards combining automated and manual processes. The WMS is the brain of your warehouse and makes it possible to optimize replenishment and pick rounds, reduce picking errors, and keep constant real time track of performance.
On the highest level, all warehouse activities need to be integrated with the enterprise resource planning system (ERP), where all long-term business planning takes place.
SO, WHAT DO I NEED IN MY WAREHOUSE?
As always, the boring answer is: it depends. On factors such as size, type of goods, level of automation, and need for flexibility. But even more important than WHAT is actually FOR WHAT, as in for what am I going to use each system.
Because it is here things tend to become a bit messy. Your automation supplier might say their WCS is actually a WMS, a WMS-solution might include WCS functionality, and many ERP-systems have WMS-modules, and is a WES really both a WMS and a WCS at the same time? The result can become patchwork of overlapping functionality, as shown in the illustration below.
To make all activities in the warehouse, automated and manual, as efficient as possible we recommend a clear separation of functionality, between different levels of warehouse software systems. Choosing the right setup from the beginning is important. Depending on the amount of automation equipment in your warehouse operations or if your business model requires complex logistics solution one good solution is a best of breed WMS that can grow with your business, together with a seamless integrated WCS, enabling the same business logic, independent of automation vendor.
In this model the WMS handles all customer and order data, business rules implementation in the warehouse and box calculation/synchronization over different warehouse areas. The WCS handles coordination of automation equipment (assignment based and prioritized by the WMS) and acts as the ”traffic cop” for the automation, the MFCs (one or several depending on set-up) controls individual segments of the automation (set of conveyors, crane system etc) and executes assignments as orchestrated by the WCS. The MFCs also handles low-level communication with the PLCs.
It is also a good idea to choose WMS and WCS from the same supplier. With this so called white box solution you can operate with the same setup and logic in both the manual and automated parts of the warehouse. This also means only having to make development in one system, and use it in the whole warehouse. This also gives you the freedom to choose and combine automation equipment from any supplier.
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