Drexel University symposium focuses on quality & reliability.

Drexel University Symposium Focuses on Quality & Reliability

Solving casting defect problems using designed experiments and ultrasonic detection of aluminum casting defects were just two of the topics discussed in a wide-ranging symposium sponsored by Drexel University's Aluminum Casting Research Laboratory (ACRL). Professor Diran Apelian, Associate Dean of Drexel's College of Engineering, was host of the April 19th event in Philadelphia.

In explaining the ongoing research at the ACRL, Apelian said, "There are really two major things we are looking at in the field of propagation and clean metal refining. One is obviously inclusion removal by filters, particularly focusing on the effect of the external forces one puts on the melt, as well as optimizing inclusion removal. The second topic is online control of inclusions."

Managing Change

Following Apelian, Elwin Rooy, ALCOA, discussed ways in which "constructive change" can be effectively managed. Faced with challenges from ceramics and other new materials, and decreases in global market share, aluminum casting producers must learn to adopt new technology much more rapidly, he said.

Rooy emphasized that new technologies can be implemented most effectively if employees understand why change is important. In an era in which our knowledge base is doubling every five years, competitive advantage goes to those who are innovative, not to those who produce copies, he said. In this context, Rooy noted that education must be accepted as ongoing and continuous.

Tom Enright, Casting Div/Ford Motor Co, discussed the steps involved in a designed experiment and then described, in two case studies, the results of implementing this technique to reduce defects. Enright remarked that 90% of the success of a designed experiment lies in analyzing the possible causes of the casting defect during the initial brainstorming session.

But once successful, Enright said, "Design of experiment techniques tell you exactly which parameter is out of whack. And if, for example, you happen to trace the problem to an individual who is not recording the data or is recording it improperly, chances are they won't do it again, because they realize they'll be identified."

Shrink Porosity

A program analyzing inclusions in die castings is underway at Doehler-Jarvis Co, according to Robert Wolfe. The largest independent diecaster in the U.S., the company sells roughly $300 million in die castings annually, 85% to automotive manufacturers.

Wolfe is optimistic that diecasting is on the threshold of a new market area in engine blocks. "In the 1990s, I think there will be a general conversion to aluminum blocks. Lower production volumes--less than 30,000 pieces per year--will be perm molded and sand cast, but in high volume production, diecasting has to produce that part-probably with liners in the combustion chambers. That way you can put a different set of properties in the very critical area of the block, and the rest of the block is a relatively simple configuration compared to a transmission case."

On-Line Control

In a presentation on on-line control, Prof. Apelian noted that Drexel had just finished a National Materials Advisory Board committee report on controlling metals processing. "Previously, what we were really doing was modeling the process. You need to first understand what the important parameters are and then monitor and measure on a daily basis for control.

Thermal analysis is not new, but Apelian noted that such an on-line test permits detection while providing a parameter of the level of grain refinement. In terms of modification, the interaction effects of the species are not completely understood, he said. This includes determining the optimum level of additives, and the effect of grain refinement on modification.

Concerning inclusions, Apelian noted, "We don't know what is the best way to assess the inclusions in the molten metal, which is a very important aspect. Inclusion level assessment needs more development."

On another development in on-line controls, Prof. Alex Meystel of Drexel Univ revealed that Drexel's Computer Engineering Dept has received a request from the Dept of the Navy to develop a knowledge-based control for spray casting. Mystel discussed how an engineering database for on-line control would be developed.

Ultrasonic Testing 

John Ditri, a graduate student at Drexel, presented some of the latest developments in ultrasonic testing of aluminum castings. He believes that in the future NDT techniques will be expected to measure a wide range of thicknesses of a material; determine both grain structure/size and material cleanliness; and determine material qualities.

On the horizon, according to the speaker, are expert systems and on-line monitoring. In fact, Ditri believes that the final implementation of all these techniques will be accomplished by the implementation of an expert system. The knowledge built into the system will eventually permit on-line monitoring of temperature and degree of hardness (important to determine diecasting ejection time) through continuous feedback to the controller.

PHOTO : Tom Enright, Ford Motor Co, discussed the "Use of Designed Experiments to Solve Casting

PHOTO : Problems."