Improving Plant Performance

Part 1

by Roger A.P. Fielding, BENCHMARKS

Benchmark studies comparing the performance of extrusion plants reveal great differences in the productivity levels achieved by extruders supplying similar markets—often within the same country or geographical area. How can they compete with one another? One explanation is to be found in the differences between the level of capital employed in the “benchmark” plant and its—often “low-tech”—competitor.

Because many extruders still operate presses and related equipment that are fully amortized, the relatively low level of capital employed has enabled companies to continue to stay in business in spite of low levels of machine and people productivity. However, an analysis of the sensitivity of such business to fluctuations in the spread between the cost of billet and the selling price of extrusions will invariably show that the low-tech producer cannot survive extended periods of low selling prices.

Increasing business volume is sometimes seen as the way to stave off competition from the low-cost producer. This approach is illusory, for even though average costs will indeed be reduced, the low-cost producer will benefit more.

Competition, real and perceived, from inherently low-cost extruders, whether because of low labor rates or high levels of productivity, encourages the acquisition and installation of modern extrusion presses and related automated or semi-automated equipment. But, many such investments have failed to yield the promised benefits, and productivity levels have not reached the levels required to justify the investment. How can this be?

1) Failure to measure and record the factors affecting the current levels of machine and people productivity.

2) Failure to understand the factors affecting current levels of machine and people productivity.

3) Failure to control the current production system.

4) Failure to improve—to get the most out of—the current production system.

5) Incomplete or inadequate due-diligence in assessing the factors affecting the performance of proposed “new” equipment.

6) Failure to properly implement the acquisition, installation, commissioning, and operation of “new equipment.”

Measure, understand, control, improve, optimize, automate! This six-step process should be the credo of those who wish to manage the improvement to the performance of an extrusion or, for that matter, any production system.

Benchmark Productivity

References to the performance of extrusion presses—which have appeared in the public domain during the last 35 years—show continual improvement in the productivity of machines and people. From the benchmarks established by Robert T. Ferguson in his paper to the first International Extrusion Technology Seminar in 1969, to data circulated in 2000, the productivity of a typical eight-inch press extruding a limited range of AA6xxx shapes has increased from 2400 to 6000 pounds per hour. And in another reference, from 1994, recovery at the extrusion press has increased from 75% to 90%. In the same time period, the press crew has been reduced from seven persons to—depending on the level of automation—two or three persons:

1969—Seven-man press crew—2400 pounds per scheduled hour; 75% recovery (Robert T. Ferguson).

1977—Seven-man press crew—23 million pounds per annum.

1984—Three-man press crew—18,000 pounds per shift; 80% recovery.

1984—Two-man press crew—a reduction of one!

1988—Three-man press crew—24,000 pounds per shift; 1100 pounds/lot; 82.5% recovery.

1989—Three-man press crew—2 million pounds per month (30,000 pounds per shift).

1992—Two-man press crew—400 dies (100/150 per day); 450 pounds/lot.

1994—Four-man press crew—90% recovery.

2000—Five-man press crew—200 dies; 50,000 pounds per shift (6000 pounds per hour).

Measurement

The productive utilization of the aluminum extrusion press, which converts billet to extrusion, can be analyzed using traditional “work study” methods to describe the utilization of time. Productive work is only done when the press is extruding good material. But, much of the available time—24 hours times 365 days—is lost when the press is not—for whatever reason—manned. Additional time is lost during die tests, when the press is stopped because of “full tables,” when training operators, or during breakdowns.

Even when ostensibly “operating,” time is lost when the press is “idling” or when it is subjected to minor stops, during die changes, and during the dead cycle between successive billets. The press is not productive when extruding scrap—a common occurrence.

Measurement highlights opportunities to improve performance:

For the engineers: the extrusion press’ dead cycle must be as designed by the press builder—or better. And, maintenance downtime must be minimized.

For the die supplier—and the die correctors—die trials must be eliminated.

For the process engineers—those aspects of the die change time and the extrusion cycle time that relate to “process”—for example, the temperatures of the billet, the die, and the container must be correct.

The production supervisor is responsible for minimizing the time wasted at the extrusion press through extended dead cycles and die changes. Full tables—usually a factor of planning and organization—should be prevented.

The routine analysis of press operations is completed with an ongoing, detailed analysis of recovery.

Process scrap should be measured at the extrusion press and at the finish cut saw. Scrap should be retained in long lengths at the finish cut saw until its source has been identified. The source of extrusion scrap—the butt, the first and last billet scrap, shape scrap, etc.—should be recorded and every effort made to reduce or eliminate each occurrence.

In Part 2 of Improving Plant Performance, we’ll look at two additional measurements that demonstrate the impact of process improvements on productivity.

——

Abridged from “Managing the Performance of an Extrusion Plant,” Proceedings of the Eighth International Extrusion Technology Seminar ET ‘04 Orlando, Florida, May 18-21, 2004, pp. 565-570