"A journey of a thousand miles starts with a single step."

This ancient Chinese proverb is good to keep in mind when thinking about how a factory begins to move toward a plant-wide electronic production monitoring system. The vision of the future destination may be luminous and compelling, but turning this vision into reality is no hop, skip and a jump. It has to be taken earnestly and carefully, step by step.

In the end, plant managers will be able to access the system and get instant, up-to-the-moment reports summarizing the OEE (Overall Equipment Effectiveness) rating of the whole plant, separate production lines or even individual machine tools. Analysis of the collected data used to calculate this rating will pinpoint where problems or opportunities for improvement appear.

Here is an example of what is to come when a production monitoring system is in place: Managers are alerted to a report showing that a certain machine in one of the machining lines needed an average of 3 minutes cycle time during the last shift when it should have been closer to 2 minutes at programmed feed rates and spindle speeds. Reviewing the log of events that occurred during this shift shows that a grinding wheel was not cutting as aggressively as intended and had to be replaced at 50 percent of its expected life as a result of excessive wear. A recent change in wheel grade is recorded in notes entered by the manufacturing engineer. At the start of the next shift, a message to the cell operator gives instructions to install a harder grade wheel. Cycle times monitored during the day show a return to the required output. Problem solved.

This vision is not new. It's been talked about and dreamed about for years. In fact, the software and hardware to make it happen not only exist, but they also have a proven track record. What is becoming clear is that making the transition to this future state will be neither quick nor effortless. The first steps are the toughest, but that is where the journey begins, as the proverb reminds us.

Tecumseh Products' compressor plant near Tupelo, Mississippi, has taken those first steps, and the benefits are already clear and substantial. The plant has installed software-only CNCs on several "bottleneck" machine tools and is running key portions of a bidirectional production monitoring system that integrates the CNCs with the plant's existing computer network and ERP software. Plant management is taking the results of these initial installations as proof that these steps are definitely moving in the right direction.

Under Pressure

Although Tecumseh Products is best known for its small engines found on leading brands of lawn mowers, snow blowers and similar products, the company is a major producer of compressor motors for refrigerators and air conditioners. Consumers are not likely to be aware that the reason these products run so quietly and efficiently is the unseen presence of a Tecumseh-built compressor inside, yet the reliable performance they enjoy is dependent on the quality of those compressors. Because many of the major brands of refrigerators and air conditioners have moved production offshore, Tecumseh has had to redouble its efforts to maintain profitable operation of its compressor plants in the face of the cost pressures brought on by the severe contraction in U.S.-based appliance manufacturing.

In Tupelo, Tecumseh operates three main machining lines that feed an assembly line on which the various compressor models are built in a mix that is determined by a schedule of firm customer orders. This plant houses about 100 active metalcutting machine tools. A shop control system that relies on manual data entry allows managers to monitor production, but the information is at least 1 day old by the time it is available for analysis and response. The system tells managers basic information about labor input, machine output and scrap rates. This gives them a somewhat sketchy picture of where the bottlenecks are and when part shortages may affect the assembly line. It is adequate to tell them how to react but rarely helps them anticipate and avoid shortages that hamper the assembly line. It can't tell them what is happening inside each machine to reveal the causes of bottlenecks.

"What we have in place is now the framework for a much more capable production control and communications system," says Joe Kulovitz, a manufacturing engineering manager.

The system will eventually supplant the existing one and provide a much more detailed picture of machine performance in real time. The new system has two main elements, both from Manufacturing Data Systems, Inc. (MDSI) in Ann Arbor, Michigan. One is OpenCNC, an open-architecture machine control that replaces OEM-installed CNCs. The other is MaximumFactory, a suite of software modules that collect and analyze real-time data generated at machine control units. This software suite is tailored for the ability of OpenCNC to extract data, but the software can also be interfaced (although less conveniently) with proprietary legacy CNCs.