Improving Plant Performance
by Roger A.P. Fielding, BENCHMARKS
In Part 4 of this series of articles on “Improving Plant Performance,” we continued to focus on recovery—as measured at the finish cut saw, and productivity—measured as the average time taken to extrude each billet, and recorded in the format of the Extrusion Press Cycle. We discussed how the Double Puller should be used to maximize recovery—by reducing extrusion scrap, and to maximize productivity—by minimizing the extrusion press cycle.
However, benchmarking studies of practices employed in aluminum extrusion plants—even those equipped with double pullers—continue to highlight opportunities to increase profits by maximizing recovery and productivity. Clearly, some extrusion operations are missing the opportunity to increase profitability!
In our ET2004 paper, and in a subsequent article which appeared in Light Metal Age, we illustrated the potential impact of managing recovery and productivity on the performance of an extrusion press.
To improve understanding of how the performance of the “Benchmark” extruders is achieved, the data on recovery and the extrusion press cycle are presented in two diagrams devised by the author :
1) The Utilization of Men, Machines and Metal, and
2) The “Consistency” of Extrusion Operations.
The use of these measures is illustrated in Figures 1, 2, 3 and 4.
1) The Utilization of Men, Machines and Metal—Figures 1 and 2
The recovery of aluminum, measured at the finish cut saw, is the measure of the utilization of the aluminum billet which has been delivered to the extrusion press. Contact utilization (or machine efficiency) is the ratio of contact time to total production time, and is therefore, a measure of productive utilization of the extrusion press and its press crew.
The increase in productivity resulting from improving the recovery and the contact utilization (or machine efficiency) is illustrated in Figure 2.
2) The “Consistency” of Extrusion Operations—Figures 3 and 4
The average extrusion speed at the press is a function of the quality of the extrusion dies and the billet and—above all—of the control of the extrusion “process” parameters. The extrusion process parameters—the temperature of billet, container and dies, must be controlled to maximize ram speed.
Dead production time is the sum of the mechanical dead cycle, the average die change time, and the “time wasted” due to minor delays at the extrusion press: waiting for billet, lubricating the tooling, etc.
The data compares the performance of extrusion plants in numerous operations world wide, showing how inputs (billet and dies), and press operating practices affect performance. Clearly, upstream operations: billet or log heating, sawing and shearing; and die heating affect the inputs and their impact on performance. Like-wise, downstream operations: handling, sawing, aging and packing—because they can delay the press, also affecting performance.
Fielding, Roger A. P., “Managing the Performance of Extrusion Plant,” Eighth International Extrusion Technology Seminar, 2004, Volume I, pp 565-570
Fielding, Roger A. P., V. I. Johannes and P. Howard Fielding, “Extrusion Productivity”, Light Metal Age, May/June 2005, Volume 63, No.3 pp 6-19