Shortened product lifecycles, increased product variety, changing regulatory requirements, squeezed profit margins and global markets continually present manufacturers with new and complex challenges.

Moreover, manufacturing has become a cross-plant, cross-country, cross-enterprise process involving the entire supply chain.
To remain competitive, manufacturers need simultaneously to: reduce time to market; increase process visibility and production flexibility; optimise forecasting and scheduling; and reduce rejects, stocks, and downtime - all while ensuring optimal quality and production efficiency across global facilities.
Meeting these goals requires an integrated IT infrastructure that helps coordinate production on a global scale and, if necessary, in real time. This optimised coordination must cover such things as specifications, equipment, facilities, processes and procedures, quality tests, and personnel resources.

Functionality gap

Current IT infrastructures, however, are typically not able to effectively accommodate such levels of integration. There is an information and functionality gap between the business processes run by ERP systems and the automation of production processes and equipment.
The objectives and capabilities of business systems are different from those of control systems, yet there is a fundamental need for them to work in synchronisation with each other. Any distortion leads to inefficient operations, higher costs, and lower quality, which ultimately translates into lower profits. Therefore, ensuring tight integration, perfect communication, and efficient coordination between these systems is vital.

Linking systems

A new family of software - manufacturing execution systems (MES) - has emerged, which provides effective integration of production processes and enterprise business systems. Manufacturing execution systems not only provide a layer of communication between business and control, they also represent a set of coordinated functions capable of optimising plant activity during all phases of production.
An MES solution usually includes support for the following functions: resource management and resource allocation, dispatching, data collection and acquisition, quality assurance management, maintenance management, performance analysis, scheduling, document control, and labour management, as well as material and production tracking.

ISA-95

International organisations have established a clear definition of MES functionality and have developed models that describe and standardise MES systems.
The ANSI/ISAS95 - ISA-95 for short - international standard defines terminology and models used in the integration of MES systems and has achieved broad industry acceptance. The first two parts of the standard have already been published, and the final part is currently under development by the ISASP95 committee.
A typical MES environment helps manufacturers to answer critical production questions: How to produce? What can be produced? Where and when must it be produced? What was produced and when?
These questions have a direct and immediate counterpart in terms of ISA-95 modelling. Product definition, production capability, production scheduling, and production performance represent the fundamental business processes to create the link between control and business systems.

Essentially, ISA-95 defines the critical modules required for the development of an effective MES system: software functions, a physical model of production capabilities, and the corresponding business and production processes.
ISAS95 consists of three parts:
* Part one, 'Models and Terminology', was published in 2000 and provides basic models and the terminologies needed to define the interfaces between a company's business processes and the process and production control systems.
* Part two, 'Object Model Attributes', was published in 2001. This part defines, in conjunction with part two, the interface content between manufacturing control functions and other enterprise functions.
* Part three, 'Models of Manufacturing Operations', is still under development. Closely related to parts one and two of the S95 standard, part three will provide detailed definitions of the main activities of production, maintenance, inventory, and quality control.

A solution

The functionality and architecture of Siemens' MES offering, Simatic IT framework and components, are fully compliant with ISA-95. Each Simatic IT component is dedicated to a specific task, which corresponds to one ISA-95 software function. Together they cover all standard production functions required by ISA-95.
The Simatic IT framework provides an object-oriented methodology to model the physical plant and all equipment constraints.
This physical model allows for a clear, well-structured, and self-documenting approach during the analysis phase of an MES project. Due to their object-oriented nature, these physical models are highly reusable and therefore reduce rollout and maintenance costs.
Simatic IT framework offers a graphical environment allowing for intuitive business and production process modelling.
The resulting workflows (production operations) define the behaviour of the plant and coordinate all manufacturing-related software and equipment functions. This dramatically increases the flexibility, responsiveness, and transparency of the system.
Again, these workflows are easily reusable, reducing risk, cost, and duration of solution development, rollout, and maintenance.

Matt Holland is the MES UK Manager at Siemens. Additional information is available on the Internet at: www.siemens-industry.co.uk or call +44 44(0)161 446 6645