Manufacturing Execution Systems are the Missing Link Between the Office and the Plant Floor
Most manufacturers use a manufacturing resource planning (MRP) system for operational tasks—everything from customer orders to planning production and inventory, sourcing, scheduling, and shipping/invoicing. However, a typical MRP system doesn’t do much to support the actual manufacturing. That shortcoming brought us manufacturing execution systems (MES), which provide the tools to produce quality products effectively and efficiently.
How We Got Here
MRP evolved from basic accounting systems, about the only functions early machines could handle. In the 1960s, better systems, software, and data structures learned to play together, illustrating, for example, bill-of-material relationships. These early material requirements planning (MRP) applications combined operational functions (inventory management, planning, purchasing, customer order management, and production activity control) in a suite known first as MRP (or MRPII), and eventually as enterprise resource planning (ERP). Nowadays, the term MRP may refer to either the manufacturing portion of ERP or to the material planning application. Yes, it can be confusing.
MRP/ERP Stops at the Door to the Plant
While MRP and ERP are considered comprehensive, integrated systems, their definition restricts production activity control to scheduling only—tracking start and due date for manufacturing orders or activity—based on “standard” lead times and work completion reports from the factory floor. MES offers something extra. It adds a level of granularity to these schedules, detailing work centers and resources (people, skills, tooling) and tracking projects to the hour/minute/workpiece. It can help with planning and real-time reporting for maintenance and quality management, too.
Keeping It Real(time)
MES brings the tools to manage, track, and optimize activities and resources to the shop floor, in real time. It integrates scheduling and tracking with automated data collection from CNC controls and IIoT (Industrial Internet of Things) sensors, quality management systems, local networking, and MRP/ERP.
Typically, MRP/ERP planning only plans to the order level—start date, due date, and quantity. The production control app lays out a rough schedule based on standard times required for set-up, run time for the quantity, and average wait time at the specified work center. As the work proceeds through the plant, workers report completions at individual work centers, updating both order status and expected completion date at each step. This last projection gets compared to the MRP-generated due date, informing work center priority calculation and sequencing. This neat trick ties production activity to the master schedule and to customer demand.
Note that some MRP systems offer optional advanced planning and scheduling (APS) systems, or finite scheduling, which schedules production based on actual resource availability, optimizing workflow and helping you hit that due date. An MES, meanwhile, will create its own schedule based on the MRP’s required due date and quantity. This schedule differs from that of an MRP in two major ways:
- Work schedules represent actual backlog rather than standard or average wait times at various work centers. This data-driven shortcut produces the best workflow for effective resource use, creating accurate, achievable—and realistic—schedules.
- MES scheduling sequences the tasks at each work center and predicts start and completion times throughout the work period (how about that granularity!). These predictions can account for the availability of tooling or other resources needed for specific processes and tasks, if defined in the routing and included in the resource definitions.
Just as importantly, MES is designed to expect real-time reports from the plant floor, from the production equipment itself (CNC controllers), installed sensors, barcode scans, touch screens, and other devices. This data updates order status in near-real time across the enterprise, and dynamically re-calculates schedules to address unforeseen changes and minimize delays, conflicts, and idle time.
Tracking every tiny detail of every production activity supports integrated quality management applications that help you improve quality control and meet compliance requirements. All of this data accumulates in the ERP database, where MES can also account for other influences on schedule and workflow. Quality measurement and reporting requirements themselves, of course, can slow things down. They add measurement tasks to standard operations, and, at times, signal the need for additional work (e.g., rework or documentation) not anticipated in the standard routing. Similarly, full system integration with MES includes planned maintenance activities in equipment availability.
New Frontiers in Manufacturing Execution Systems
With the rise of Big Data, advanced analytics make MES even better. The latest innovations bring dashboards and other powerful tools that help functional managers and company executives make informed decisions without a data scientist at the keyboard. The most advanced MES and APS schedulers employ machine learning (ML) and artificial intelligence (AI) to analyze operations, such as scheduling accuracy, in a more meaningful, understandable, and useful way. Every new datum (actual experience) “teaches” the system more about how things really happen out in the plant. These lessons tweak the digital model of plant activity and workflow that guides scheduling, resulting in daily improvements in accuracy.
MES data also provides unique insights into production efficiency metrics, like cycle time, scrap rates, and machine performance. ML/AI-based analytics and simulation can provide the basis for process improvements by identifying alternate routings, bottleneck processes, resource contention, and other clues.
Selecting a Manufacturing Execution System
Many leading ERP developers have added MES capabilities as enhancements to their product suite, released optional MES system add-on applications, or offered pre-integrated solutions in partnership with external providers. If you have an installed, operating ERP system in place, check for these solutions first. If those are unavailable, selecting and implementing a third-party MES might be tricky. Custom integration of MES and ERP involves a large number of touch-points in order to maintain and adapt the integration middleware across any product change.
All that aside, the process for selecting and implementing MES should follow standard project management practice:
- Document your current processes and needs.
- Survey the market for appropriate solutions.
- Identify the right product to fit your needs, situation, and budget.
- Map out the acquisition and implementation plan and get backing and budget approval from senior management.
- Assemble your implementation team.
- Map out the full project plan, including schedule, resources required, and progress measurement points, and plug in your preferred project management scheduling and tracking tools.
- Complete the project, training users and developing operating procedures (link to SOP article).
- Finally, hold a post-mortem meeting to summarize the experience, identify “lessons learned,” document results (benefits), brainstorm the next area for improvement (next project), and formally close things out.
Bridging the Gap Between ERP and the Plant Floor
MES is the missing link between administrative systems like ERP and the real-time world of manufacturing on the plant floor. As a full partner with ERP in the shared database, MES data feeds real-time plant status upwards, to higher-level strategic planning, customer service, and supporting functions like procurement, finance, and engineering/design. Meanwhile, these systems fulfill their role in keeping plant activity fully in line with corporate objectives and customer demand.
