GE pioneers in thermoforming.

Our first CIM award ever to a thermoforming processor goes to GE Applianced in Decatur, Ala., for pioneering in-house development of a real-time, remote monitoring system for porcess and production data. When we first reported on the GE Appliances' plant in April (see PT, April '91, p. 106), its CIM system was only a few months old. Industry CIM experts believe that it's one of only a dozen or so thermoforming processors in the country attempting to implement CIM. But last month's SPE Thermoforming Div. fall conference in Wisconsin Dells, Wis., showed that CIM is beginning to arouse widespread interest.

GE Appliances' captive forming operation functions within a highly automated refrigerator manufacturing plant. CIM is used to drive down the cost of a new high-volume refrigerator model with tight control of the process and materials usage. It ties in several giant inline formers from Asano Laboratories of Japan. The entire refrigerator plant is coordinated by a plantwide computer network GE calls "Smart."

A COMPUTER HIERARCHY

Smart is a central factory monitoring system, which runs on Digital Equipment Corp.'s Micro VAX computers. A dozen of them gather plant data, three to four process information, and two do nothing but handle traffic of users logging on and off the system. The Micro VAX units connect to DEC PDP 1183 "front-end" computers, which in turn communicate with over 200 GE Fanuc programmable logic controllers (PLCs), which directly control machine processes throughout the plant, including the handful of 80-ft-long Asano thermoformers. Each former has 516 separately controlled strip-metal heating elements and is equipped to change tooling automatically in as little as 75 sec for trim-and-pierce tooling and 4-5 min for the forming mold.

Each Asano came with three PLCs controlling preheat, final heat (allowing GE to use patterns in both), index speed and closing velocity of the 75-ton forming press. A fourth GE Fanuc Series 6 PLC oversees the three other PLCs and connects each thermoformer to the central Smart system. GE began exercising the first CIM control by adding Smart monitoring hardware to each thermoformer. GE installed small IBM-compatible DEC 3865 SX computers on each former as gateways to the Smart Ethernet local-area network.

As original equipment, each thermoformer also had an IBM 7532 industrial version of a personal computer. To sav space, GE made one video terminal, keyboard and small printer do for both the DEC/Smart gateway computer and the IBM on the machine. a switch toggles the display from one to the other. The IBM computer records and graphs data on heater-element performance and temperature readings from the infrared pyrometers in preheat and forming stations. The IBM also records setup data and moves it as needed from machine to machine.

The DEC/Smart computer takes time-and-position data from the thermoformer's GE Fanuc PLC and stores and displays, for example, the last 100 heat cycles, showing the time for sheet to reach a given temperature. DEC/Smart also gives operators about 40 X-Bar & R charts of process variables (of which three or four are commonly used; the others are for diagnostics). And DEC/Smart gathers real-time data from all the thermoformers onto a summary screen, accessible from any PC in the plant. The thermoformer's PLCs do a 50-millisec program scan, while the DEC/Smart data-management program takes 20 sec to scan, but that's fast enough to record every thermoforming cycle.

TIME IS OF THE ESSENCE 

The initial monitoring program written for the DEC/Smart computers on the Asano machines tracked only process time and machine position, though it did so with millisecond precision. Time is convenient to monitor because it relates to a lot of other machine variables. "Transfer-forward time, for instance, is a health-and-well-being check on the motor that runs the transfer, the gear box, the bearings it rides on, and all the switches," says a GE senior controls engineer, adding that gathering too much data creates "an avalanche of false alarms that just aggravates people." The machines have alarms that signal out-of-parameter time conditions. Controlmen also check summary screens from PCs anywhere in the plant.

Eventually, GE plans to monitor temperature and pressure as well, and will be able to count good and bad parts reliably and automatically, instead of doing manual countrs before a tooling change.