Aerospace DNC moves onto a PC-based network.

A transition to "paperless" operation is taking place in many areas of the plant. Networks are moving information to and from order entry, inventory, billing, shipping, customer tracking, and almost every other department.

To a large extent, however, the shop floor has been the exception to this rule. Distributed numerical control (DNC) systems have alleviated some of the problems created by paper documentation by connecting CNC machines directly to the programming source. But they haven't addressed the full concept of information management and control. To make this happen, a new approach to handling manufacturing information is necessary.

One plant moving toward paperless manufacturing is Textron Aerostructures (TA), a Nashville, TN, manufacturer of large aero-space structural parts. The plant was using paper tape for NC programs when managers began to look for ways to eliminate problems in handling, storage, and tracking. Manufacturing staff engineer Mike Clemas is responsible for maximizing machining time on more than 40 machines. "We have one gantry mill that's over 100 ft long and cost more than $4 million, so we want it to be running every minute possible."

TA looked at several options for transferring part programs, ranging from a portable disk drive system to custom machine interface software that cost more than $1 million. The company rejected both approaches in favor of a PC-based system. "If you have a system that uses industry standard PCs, when one fails, you can quickly swap it out and avoid a delay," says Mr Clemas. "If the system has proprietary components that can be swapped out, you can still maintain your up-time by having a spare on hand. But software is a different matter. If you try a system that hasn't been used in actual manufacturing situations enough to have most of the bugs corrected, you can have problems. Debugging takes time. We looked for products that met our information handling needs, had the DNC features we needed for shop floor communication linkage, ran on PC networks, and had the bugs worked out of them."

After a thorough search, the company settled on the CIMNET DNC Plus system from JNL Industries. The CIMNET system connects more than 30 machines in three buildings and cost less than $200,000, according to Mr Clemas.

TA uses a Novell file server (host PC) linked to the company mainframe in one building. An Ethernet network connects separate servers in the other three manufacturing buildings that receive data files over a broadband cable from the host. When a part program is loaded at the host, it is specified for a particular building and automatically sent to a download directory there. Operators use network terminals at their machines to request their next assigned part program, which is held in an "approved" directory.

Operators can make changes to programs, but then the part and the revised program must be approved by Quality Control. The changed part programs are saved in a separate "try-out" directory until QA personnel, who are also on the network, approve them. From there they go to the upload directory for supervisor approval.

"The goal that led to the installation of the DNC system was the need to keep machines running 100% of the time, and that has been accomplished," Mr Clemas says. "Even with the summer heat in the plants causing some of the PCs to go down, we just swap them out with a new one, initialize the new PC, and it continues on from there just like nothing happened. We have the right part programs and other information available at the right time so that the operation stays up virtually without fail. With less than one percent downtime for the entire plant."

Mr Clemas also is interested in a CIMNET product called Folders, which could provide even more information to machine operators. The relational database package collects all files that pertain to a specific machining operation for a part in electronic "folders," including the part program, a viewable drawing file, setup and routing sheets, routing sheets, tooling specs, or any other type of ASCII, DXF, HPGL or TIFF file. ADOS version of Folders has been on the market for a year, and the software is now available for Windows as well.

The system functions as a true network, in that any network terminal (node) can communicate with any other terminal. Some DNC systems have a central library that can act as a node on a network, but the terminals at the machines communicate only indirectly with the network, thus preventing simultaneous communication with two or more nodes at a machine.

The CIMNET also has true multi-tasking capability. This means being able to send and receive data from any two or more machine controls or terminals at once--an important consideration for the exceptionally large program files common at TA. If a large part program is being "spoon-fed" to a machine in pieces small enough for the control to handle, a non-multi-tasking system would be effectively unusable for other operators and terminals.

Planned integration of TA's other networks will benefit other workers in the factory besides CNC operators. For example, the same information, except for the part program, is necessary for manual operations, so a network node can be located centrally to a group of machinists. Or, assembly supervisors can use a terminal to track part modifications, scheduling changes, or other important information.