A Review of Papers Presented at the Ninth International Extrusion Technology Seminar, ET’08 – Part III

by Roger A.P. Fielding, Benchmarks

In Parts I & II in this series on the teaching presented at the Ninth International Extrusion Technology Seminar, ET’08, we questioned why the process of “continuous improvement” is deemed necessary to achieve benchmark performance in extrusion operations. An extrusion press designed to produce 6000 pounds (3000kg) per hour should extrude at that rate when commissioned.

Using previously published data, we went on to discuss benchmarks for productivity. The example of an 8", 2750 sht press producing at an annual rate of 36 million pounds in 6000 manned hours was reported in earlier Worldwide articles and elsewhere—as were the following observations on the key factors affecting the performance of an extrusion press (1)(2):

Consistency of Extrusion Operations. Assuming consistent billet quality, the extrusion speed is dependent on the quality of the extrusion die and the control of the extrusion process. Assuming that extrusion speed is at a maximum, the instantaneous productivity – in pounds (kg) per hour - is maximized when the dead production time (the combination of mechanical dead cycle and waste time,) is minimized. (Figure 1)
Utilization of Men, Machine and Metal. Press recovery, from billet or log to finish cut saw, defines the utilization of metal. The ratio of the Extrusion Cycle Time to the Operating Cycle Time defines the utilization of men and machines. (Figure 2)

To increase productivity, all these measures must be improved. And since productivity and ultimately profitability are dictated by these parameters, the operation of any extrusion press can be modeled to define the recovery, the utilization, the extrusion speed and the dead production time that must be achieved (and controlled) to meet the company’s financial objectives.

Having defined the above measurements and the magnitude of the improvements required to meet the objectives, an action plan – often requiring dramatic, step-changes - is required. By comparison, Continuous Improvement is by its very nature an incremental process, ill suited to achieving step-change.

In the past, step-changes in productivity –defined in the broadest sense - have often accompanied the introduction of new equipment. For example, the Hot Jet Furnace and the Double Puller, which were featured at the Third International Extrusion Technology Seminar in 1984 have had a significant impact on - respectively:

the control of billet heating, temperature and energy consumption, and
recovery, from billet or log heating to the finish cut saw. (3)(4)

The following ET’08 papers report significant contributions to improving the quality of billet and dies, the control of the extrusion process, improving recovery at the extrusion press, and improving press operations.

The Standardization in Metal Analysis, reported by Denis Choquette, and Improving Hydrogen Measurement in Molten Aluminum, by Corleen Chesonis and her colleagues, describe the results of years of work directed at improving the quality and consistency of extrusion billet. Although both papers report aspects of "continuous improvement," the current measurements represent the (only) acceptable standards for billet quality.

Modar Mohammed Al Mekdad and his colleagues report on improvements in the performance of extrusion dies. This, the result of a cooperative effort involving MTD – Switzerland and independent die makers. They report that die trials have been limited to one, that extrusion speed and hence productivity has increased, and perhaps as significant, there has been a reduction in the incidence of incomplete lots.

Three of the ET'08 papers describe the current status of extrusion process control. Eckenbach and, in another paper Kortmann, report on the development of container construction and heating systems, and the control of container temperature. All are essential elements in effecting control of the extrusion process and reliability of the press system. Barron reports that automatic closed-loop control of the extrusion process – "inconceivable only a few years ago," enables the development of best practices which are independent of press crew through "the consistent use of temperature feedback for the real-time optimization of the process." Together with the modern billet furnace and the single-cell die oven, the container heating establishes the thermal conditions under which extrusion proceeds.

For a more complete guide to managing the recovery and productivity of an extrusion press, refer to the Five-Part Worldwide series of articles: “Improving Plant Performance,” (1, 2, 3, 4, 5). Benchmark performance was discussed in the article "Dream Numbers" which appeared in Worldwide, Volume 12/Issue 4.

Fielding, Roger A. P., Improving Plant Performance, Worldwide Volume 12/Issue 3, and
Fielding, Roger A. P., V. I. Johannes and P. Howard Fielding, Extrusion Productivity, Light Metal Age, vol. 63, nos. 5, 6. June 2005, pp. 6-14. And,
Bugai, John C., Flame Impingement-Jet Convection Design for High Efficiency Billet/Log Preheating, Third International Extrusion Technology Seminar, ET’84
Smith, B., and C. G. Gentry, The Exciting Double Puller from Norway, ibid
Choquette, Denis, Standardization in Metal Analysis – No Longer an Option, Ninth International Extrusion Technology Seminar, ET’08
Chesonis, D. Corleen et al., Improved Hydrogen Measurement in Molten Aluminum and Aluminum Alloys, Ibid
Al Mekad, Modar Mohammed, et al., Implications and Influence of Complex Extrusions and Non-Standard Shapes on Extrusion Press Productivity, Ibid
Eckenbach, Wolfgang, Process Controlled Containers – Smart Containers, Ibid
Kortmann, Wilfried A., Extrusion Container Technology from Yesterday to Tomorrow. Ibid.
Barron, Bill, Automatic Closed-Loop Control Comes of Age for Aluminum Extrusions, Ibid.