The value of BCL to the CAD/CAM user

Modern Machine Shop, July, 1991 by Susan P. Zahner

A User's Story

Jim Shipp, Engineering Services Manager, at Textron's Aerospace Products Division in Columbus, Georgia, is an enthusiastic user of BCL. This 200-worker plant manufactures flat pattern airframe components for commercial aircraft--parts cut from sheets of aluminum and then shaped over steel dies in a hydroforming press. The number of CNC machines is small and none would be appropriate to handle another machine's jobs, so exchangeability of NC programs is not a high priority on the shop floor.

A Trumpf multihead router cuts nested patterns from stacks of aluminum sheet. A five-axis Rambaudi mill machines the steel die blocks that bend the flat patterns and form flanges on their periphery. Nevertheless, both machines are equipped with Vega controls designed for BCL, which were originally installed about ten years ago when defense contracts were expected to be a major part of this plant's workload. NC programs are prepared on a two-seat SABRE-5000 system that uses GST-BCL to output files in the BCL format.

According to Jim Shipp, BCL is mostly handy because it allows him to job out programming when his plant's CAD/CAM system is tied up. He sends out CAD files in IGES (Initial Graphics Exchange Standard); NC programs in BCL are returned. These files are "ready to run" on the shop floor with no additional processing beforehand. Although he has used a programming house in nearby Atlanta that also has a SABRE-5000 system, he has several other sources that could also provide BCL programming. "With BCL, we know exactly what we are getting and we know exactly how our machines will execute the programs. There are no surprises."

"BCL is also valuable to us, as a relatively small plant, because it makes it easier for us to train programmers," he points out. In addition, he believes that a BCL file will someday be routinely included with the documentation that accompanies a workpiece to serve as an exact record of the machining process that produced it.

Integration

An NC program is quite literally the link between design and manufacturing. The NC program is ultimately how designers and engineers convey their intent to the shop floor. The NC program represents a description of the production process whereby an abstract set of dimensional data and feature characteristics takes material form as a workpiece. Hence, the best way to look at an NC program is from two points of view at once--from where it originates and from where it is executed. To a CAD/CAM system user, the NC program is output. To the shop floor, it's input to the machine tool.

Most discussions of BCL have concentrated on its significance to the shop floor. BCL is a viable approach to creating neutral machine tool input. But it is also a viable approach to creating neutral CAD/CAM output. Because it works both ways at the same time, BCL brings CAD/CAM and the shop floor closer together by offering benefits mutually attractive to both. Integration, as in computer-integrated manufacturing, implies that designers, engineers, NC programmers, production supervisors and machine operators work together as a single, coherent, flexible, profit-making team. As a neutral interface language for NC, BCL can help make this happen.