Empowering the programmer: A project aimed at making military aircraft parts faster shows just how much productivity gain can come from automating the programmer's repetitive tasks

Modern Machine Shop, April, 2002 by Peter C. Zelinski

On the shop floor, the value of automation is clear. By automating predictable, repetitive tasks, a manufacturer gets more benefit out of its investment in skilled labor. Employees are set free to apply their efforts to higher-value work.

This same rationale applies to programming. By automating mental tasks that are predictable and repetitive, programmers can be set free to focus on more sophisticated programming challenges. In other words, cost-saving automation can take the form of software as well as hardware.

Where software for computer-aided manufacturing is concerned, two capabilities hold out the promise of delivering far more programming automation than most shops enjoy today. These capabilities go by the names automatic feature recognition and knowledge-based machining. The two capabilities work together. When CAM software can automatically identify the CAD model's various geometric features, the software can then call upon stored machining knowledge to determine the best way for each of those features to be machined. Thus the software can--in theory--kick out the NC code on its own.

In practice, automated programming systems generally demand more human intervention than that. A programmer of some sort not only has to input the machining "knowledge" on which the programming algorithms are based, but also has to refine that knowledge as part designs, processes and manufacturing methods change. What's more, if the part geometry is at all complex, then a programmer probably has to help the system along with various steps in its analysis.

But the work that a programmer still does have to do is not the important point. Far more important is the fact that automated programming systems are now achieving significant time savings in real-world applications.

One application using automated programming for relatively complex parts involves the U.S. military. It also involves several companies concerned with military aircraft production. A joint project called the High Throughput Manufacturing Program--"HiThru" for short--seeks to speed the production of aircraft structural components by minimizing programming time.

The project was conceived to let aircraft service depots respond quickly in cases where a replacement part is needed and no NC program exists. The project begins at the point where a CAD solid model exists, and aims to develop an automated programming system to let the depot obtain an NC file from this model as quickly as possible. Potentially, the depot might scan the old part, create the model from the resulting data, and use this model to generate the program for a machine tool located on site. In a test of automated programming algorithms developed so far, HiThru team members generated five-axis tool paths from the CAD models for parts originally made on three- or four-axis machines. Five-axis machining saves on setup and cutting time, and through the use of automated programming, it saved on programming time also. Savings fell in the range of 30 to 90 programmer hours. Partly to realize these same savings for themselves, and partly to realize other benefits as well, the manufacturers of original aircraft parts are also interested in this technology.

In fact, even for manufacturers far removed from the aircraft industry, a close look at the HiThru project is valuable. As a real-world example of automatic feature recognition and knowledge-based machining, the project illustrates at least two important points for understanding these technologies. One is the value of constraints. HiThru's automated programming system generates NC code for aircraft structural members machined from rectangular billet, and the range of parts is no broader than that. The system works well because the application is so well defined.

The other point the project illustrates is just how difficult it may be at the outset to equip an automated programming system with the machining knowledge it needs. Part of the difficulty results from the fact that different portions of the knowledge may exist in different people's minds. If so, those people have to work together to pool what they know.

HiThru A? A Glance

The National Center for Manufacturing Sciences (Ann Arbor, Michigan) is the partner in the HiThru project that brought all of the other partners together and now coordinates their efforts. Other partners who have been with the project from the beginning include Cincinnati Machine, Sikorsky Aircraft, software company Technology Answers and the Warner Robins Air Logistics Center. Joining the project more recently were Boeing Military Aircraft and Missile Systems and the Cherry Point Naval Air Depot.

Most of these names will be familiar to anyone whose work touches on military aircraft production. The Warner Robins and Cherry Point facilities are military depots charged with repairing aircraft and returning them to service quickly. Sikorsky and Boeing are aircraft manufacturers, and Cincinnati Machine supplies companies such as these with five-axis machine tools designed for aircraft part production. The one name that may not he familiar is Technology Answers ofSan Diego, California--the only software supplier in the group.