Sensors Mag

Meeting Manufacturing Operational Objectives

November 14, 2007 By: Jack Wilkins


Jack Wilkins

Current economic conditions, global competition, and delays of new equipment purchases are causing manufacturers to be sensitive about all aspects of operational costs. In this environment, it pays to consider both creative and proven methods that you can use to bring your product to market at minimum cost. Overall Equipment Effectiveness (OEE) is a method that meets this objective.

The OEE Approach

Fundamentally, OEE is a performance metric compiled from machine-availability data. OEE also captures the reasons for downtime (e.g., machine conditions, material status, production personnel, or quality issues) and can encompass the individual machine level, a line or cell level, or the entire plant. At the plant level, OEE metrics can be correlated with other plant metrics to provide key performance indicators. With enterprise-level technologies, such as executive dashboards, managers can monitor OEE plant metrics and drill down to find the root causes of problems, getting minute-by-minute updates to enable real-time process improvement. Downtime reductions can be readily achieved by using OEE to gain visibility into machine status and to analyze problems.

An OEE system enables the shop floor to go paperless. Typically, facility operators and supervisors spend an enormous amount of time recording, analyzing, and reporting on downtime, then further explaining these reports to management. An OEE system captures and reports downtime and efficiencies automatically. This eliminates the time wasted in non-value-added reporting and allows personnel to focus on more valuable tasks. With OEE, everyone from the plant floor to the boardroom is more informed, more often, more easily.

OEE also enables predictive maintenance, which can dramatically reduce repair costs. As the information on factors contributing to downtime grows in the historical database, the maintenance department can discern trends and predict impending failures. Also, by interfacing the OEE system with a Computerized Maintenance Management System, the maintenance department can take proactive steps to do predictive maintenance. For example, maintenance can order the necessary part in advance and get better rates. It can allocate repair personnel from an existing pool of resources instead of hiring someone on an emergency basis. All this can result in huge savings compared with repairing a machine after the breakdown has happened.

The net effect of reduced machine downtime, higher productivity of operators, and reduced defects is the ability to achieve higher production levels with the same amount of resources.

Supporting Systems

Other systems meld with OEE systems and enhance the overall drive for process control and optimization. Among these are Asset, Automation, and Change Management Systems.

Asset and Automation Management Systems are important to manufacturing because they can reduce downtime, re-engineering costs, and equipment loss due to misplaced databases or other preventable errors.

Change Management Systems allow you to gain more control over your plant by requiring authorization to make changes to devices and projects. These systems are designed to manage data assets in the industrial environment, such as PLC programs, HMI/SCADA application files, Computerized Numerical Control (CNC) programs, CNC data, CAD drawings, and robot programs. These are important assets because of the time and money invested in configuring and programming them. Change Management Systems typically supply the analysis and reporting tools necessary to meet validation or quality system requirements and to optimize engineering practices throughout system life cycles. These systems are a key component in managing the life cycle of automation projects. By using traceability, security, and the ability to approve changes, the system helps you manage your projects.

Version control is a key piece of the system because it ensures that only one person at a time is making changes and it archives versions as changes are made. It also provides the ability to revert to previous versions. If unauthorized changes are made, for example, it is easy to restore a previous version to keep your operation running. Ideally, version numbers are automatically assigned when revised versions are saved to the server. Typically, versions can be labeled in such a way that it is easy to locate the master copy or engineering changes. Alternatively, you can take advantage of an existing labeling system.

Access control in a Change Management System allows you to determine which employees have access to projects and devices in the system. The system can grant access based on user IDs, passwords, or group affiliations. For example, in a control application, a user may be allowed to monitor a device or project but denied online programming privileges. Access control allows you to reduce the number of errors that occur due to unauthorized access.

Change Management systems also allow you to build audit trails. These let you track activity affecting programs and devices in your plant. The system automatically maintains a history of who has logged onto the system, what projects have been accessed, and what software has been used. The user also has the ability to enter comments about the changes made. You should be able to specify what information is logged so that you collect only information that is needed.

Change Management Systems offer real value to manufacturing operations, whether you want to better meet regulatory requirements, such as 21 CFR Part 11, or just improve your manufacturing practices.


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