MES vs ERP Critical Manufacturing, 2015
Defining MES Loosening the categories The case for modular MES Modular MES in practice Strategic enterprise integration still matters 3 6 7 8 9
Originally written for Control Engineering Magazine as Define, integrate, implement MES with controls, ERP Modern manufacturing execution systems (MES) can deliver the flexibility to enable manufacturers to define the solutions that meet their strategic needs. MES is what you make it: Define the MES functions needed, use standards, consider modularity, and integrate controls with MES and MES with enterprise resource planning (ERP), as needed. Strategic enterprise integration has been in the making for the past two decades. While much of the technology to accomplish this integration is available, the number of companies actually claiming to have achieved any grand integration is few. The first generation of manufacturing execution system (MES) implementations were among the first technological categories tasked with providing the glue that would integrate all parts of the enterprise and established the potential of this category. However, their success was limited, partially by narrow and often conflicting definitions of what MES scope and functionality actually are. Today, a new generation of more open, flexible systems allows manufacturers to define MES in the way that works best for their operations. 2
Defining MES An MES is a dynamic information system that drives effective execution of manufacturing operations. Using current and accurate data, the MES guides, triggers, and reports on plant activities as events occur. Ideally, an MES is composed of a set of functions that manage production operations from the point of order release to manufacturing through the point of product delivery, depicting all stages of the overall production process. One of the most significant programs to define MES technology and its role in improving manufacturing excellence was the ISA-95 standard developed by the International Society of Automation (ISA), in league with the manufacturing community and system suppliers, including control, enterprise resource planning (ERP), and MES providers. (See sidebar at the end of the story: ISA-95 Enterprise-Control System Integration, Parts 1 to 6.) ISA-95 addresses MES concepts using the somewhat broader term of Manufacturing Operations Management (MOM), but both attempt to model the exchange of information between business logistics software and manufacturing operations software. They also model which activities the software can play and the exchange of information within manufacturing operations systems. 3
Figure 1 shows the ISA-95 functional hierarchy of levels of manufacturing decision making. At level 4, there are business planning and logistics decisions, which are supported by ERP and supply chain management (SCM) systems. Level 3 has been where traditional MES lives, providing tracking and trending information to support decisions in areas such as workflow, recipe control, and maintenance. At levels 0, 1, and 2 are decisions related to real-time production events, such as process sensing, manipulation of supervisory control, and process automation technology. This is the domain of distributed control, supervisory control and data acquisition (SCADA), and programmable logic controller (PLC) systems. Figure 1. ISA-95 functional hierarchy of levels of manufacturing decision making. 4
In addition to mapping out the hierarchies of manufacturing operations, ISA-95 also aims to improve interoperability among them, particularly between the ERP and MES systems. Figure 2 is a compact systems view of the ISA-95 standard mapped to the Purdue Reference Model. The dashed line indicates a possible border between ERP and the control system. In the most typical flow, scheduled orders pass to the control layer, which then returns the production response and capability information. The standard describes material, personnel, equipment, and other information required for an effective scheduling model. But it is critical to note that the standard does not intend to dictate exactly which system to use in which situations. It provides only neutral guidelines and data exchange structures that companies are expected to adapt to their own situations. The ISA-95 standard also provides guidelines for defining the functional scope of manufacturing operations management activity. This includes definition management, resource management, detailed scheduling, dispatching, execution management, data collection, tracking, and analysis as they apply to the production, maintenance, quality, and inventory areas. Traditionally, MES has been viewed as a translation layer between ERP (level 4) and the controls and Figure 2. ISA-95 functional hierarchy of levels of manufacturing decision making. automation layer (level 2). In this role, the purpose of the MES system is to register and control-in near real time-all production orders coming from the ERP level. It does so by interfacing with the control levels to collect and provide real-time production data and return all the necessary logistics and financial relevant data back to the ERP. But defining the function of the MES in only this way does not do justice to its tremendous potential for improving manufacturing productivity, quality, and flexibility. Its ability to process real-time data, enforce business rules, and integrate them with engineering, quality, and production workflows make it the ideal platform for continuous improvement. 5
Loosening the categories Realizing the true potential of MES requires shifting focus from trying to define where anything fits in the categories, to looking at what is needed to maximize production value for the end user. Ever since the Manufacturing Enterprise Solutions Association (MESA) created the first model, MESA and the industry in general have acknowledged that the boundaries between the different systems which co-exist in a manufacturing company are fluid, not rigid. When looking at the barriers between the ERP and MES software, for example, there is a clear overlap among many functions, such as planning, order control, human resources (HR), and maintenance management, to name a few. And likewise, there are overlaps between what might constitute the activities at the MES level and at the supervisory control level (level 2). CGI/Logica, for example, categorizes 15 questions that can help manufacturers determine their software needs. (Click here for more information) The following are examples of criteria that can be used in deployment: Resolution: What data resolution is required for tracking and tracing? Response: Does the operation require real time data, or can it be processed in batch mode? Configurability: Is the configuration possible through out-of-the-box product features, or does it require custom development? Changeability: Is the manufacturing process expected to be stable over a given period of time, or does it require frequent changes and adaption? Answering such questions guides the determination of the right system to implement each of the MES functions. While the ISA-95 standard makes it clear that such level-3 functions fit into the overall MOM scope, it does not dictate that all shall be necessarily implemented by a given MES solution. In fact, for some segments and for some industrial contexts, some of these functions might even be better fulfilled by the ERP. A modern analytical framework can help us determine the feasibility, the effort and cost, the flexibility, and the maintainability of deploying systems at various levels of the enterprise. Framework created by 6
The case for modular MES Achieving optimal productivity requires a mix of functions performed selectively by either the ERP or the MES software. The ISA-95 standard helps define such a solution by modeling the exchange of the information between business logistics systems and manufacturing operations systems and also by modeling the information exchanged within level 3 of manufacturing operations systems. This implementation strategy depends, however, on a critical factor: the existence of a truly modular MES. More precisely, it must be possible to run specific modules without implementing the complete application. And it must be possible to integrate those modules easily with functional modules residing in different applications, including the ERP software, as well as others. Rather than functioning as a monolith covering all possible functions, the MES must be a set of modular building blocks, from which a specific plant can choose to implement or not according to its business situation. In addition to enabling end users to build their ideal solution, this modularity helps in the following ways: Scaling: Manufacturers want to implement functionality step-by-step, for methodology reasons or in accordance to their human or financial resource capacities. Migration: Similar to scaling, functional modules need to be introduced stepby-step, while interacting strongly with legacy solutions. Domain specialization: Despite the wide functionality set provided by the MES, it may not include very specialized requirements required for some industries. Modularity is not, however, something that can be added to an existing software product. The solution must be designed for modularity at inception, through an architectural or solutionbased framework that remains open to the later addition of a variety of solutions. Another virtue of this more modular and systematic approach to software development is a more generic system that is more broadly applicable to manufacturing challenges in a range of different industries. It also means that one is capable of modeling more complex scenarios that incorporate very different processes. 7
Modular MES in practice An interface between the ERP and the MES was implemented for a large integrated circuit (IC) substrate manufacturer. While the project included the full-scope MES and automation aspects of a large volume facility, one of the critical areas was the interface to the SAP ERP software. The company uses SAP R/3 for planning and SAP APO- Advanced Planning Optimization for mid- and long-term planning. The first aspect considered was the reliability of the interface. Required for several functional areas, the interface was bidirectional and composed of synchronous and asynchronous calls. Given the different nature of systems integrated, however, particularly in terms of the realtime and criticality, the installation required advanced buffering and error management techniques. Buffering was essential because of significant differences in the uptime related service-level agreements (SLAs) of the two systems. If the ERP is offline for any reason, the MES could not stall, because it helped protect the required 24/7 operation by buffering calls and then performing them when the ERP system was back online. Advanced error management was also a must, since the systems were controlled by different groups within the organization and dispersed geographically. Changes at the ERP level could be done, sometimes not completely considering all the implications in the different manufacturing facilities, so advanced error management procedures were also of utmost importance. Functionally, the data integration had been performed in different areas, the following being the most critical: Synchronize material master data from ERP: The client's ERP system maintained the master files including product information, bill of materials, flows, equipment, and production steps. The target was for this to be the only source of such information, so that all changes made would synchronize with MES immediately. Production orders: Likewise, production orders were synchronized from the ERP into the MES, with the MES applications reporting back to the ERP system with regular and event-based updates on anything that impacted order status. Engineering orders: Engineering orders were created at the MES level and shared with the ERP system. Maintenance orders: Because MES applications track closely to the real usage of the manufacturing equipment, it was most efficient to perform the maintenance management functions at the MES level, including time- and usagebased events. The maintenance related information was sent to the ERP. Material inventory: Material inventory was regularly updated from MES into the ERP. Warehouse management: Warehouse management was implemented at the ERP level, but requests from the shop floor that impacted warehouse inventory were synched with the MES. Human resources (HR): Several MES functions required up-to-date HR information. This included potentially critical information on employee training, certifications, roles, and authorizations, etc., that must be synched regularly with ERP and MES on HR data. 8
Among the most used functional areas designated by ISA-95 is the sending of production schedules from ERP systems to MES and synchronizing actual production status and performance info back to the ERP. This enables two-way communication between corporate level planning and scheduling to increase visibility of the production floor. Beyond the interfaces mentioned above, scheduling interface was implemented for this client. In this model, planning and scheduling are done at different levels, at the ERP and at the MES, enabling the combination of the tactical and operational level scheduling capabilities. The ERP system provides infinite capacity planning based on ship and start dates. This is then sent into the SAP Advanced Planning and Optimizer (APO), which does finite planning based on capacity and ship dates, not at the resource/equipment level, but at the work-center level. This high-level rough plan is then sent to the MES, which in turn translates it into the operational plan, considering additional operational factors. These include resource availability and capabilities, recipe and durable dependencies, shift management (employee availability, qualifications, and certifications), stock levels, setup times, preparation and acclimation times of consumables, and time constraints of products and consumables, beyond manual prioritizations. The operational planning, at the MES level, has a higher granularity and, based on additional information, fine tunes the sequences previously determined by the higher level planning done at the ERP level. Moreover, because conditions might change at the shop-floor level, the system reschedules the operational plan with a much higher frequency than what the tactical planning does. Strategic enterprise integration still matters Viewing the MES/MOM space as much more than a simple translation layer puts strategic enterprise management back on the table. As a control and a continuous improvement platform, it enables the improvements in productivity, quality, and flexibility that are essential for competitive survival in today's hyper-dynamic in global markets by enabling at least the following: Synchronizing manufacturing operations within the supply chain; Increasing visibility of the production plan to operations and all other stakeholders; Increasing the decision confidence, helping everyone to know what to do when the situation changes. These are essential to improve productivity, quality, and responsiveness. MES can boost productivity by increasing yields and reducing maintenance and labor costs. It improves quality, through monitoring and controlling production processes and properly managing manufacturing exception processes, while providing systematic enforcement of established norms and guidelines. And it enables faster reaction to market variations and contingencies as well as enables faster introduction of new products. 109
About Critical Manufacturing Critical Manufacturing provides manufacturers in highlycomplex environments with a modular, scalable manufacturing execution and intelligence system that enables users to flexibly address market demands, increase efficiency and bolster reliability across the supply chain while lowering TCO. The company is part of the Critical Group, a private group of companies founded in 1998 to provide solutions for mission and business critical information systems. www.criticalmanufacturing.com HQ: Porto, Portugal t: +351 229 446 927 Austin, TX t: +1-512 291 0068 Dresden, Germany t: +49 (0)351 4188 0639 Suzhou, China t: +86 512 626 05371