In a windowless office they call the "war room," General Electric Co. technicians are designing a new model in a line of robots and computerized manufacturing controls that they hope to install in automated factories of the future.

Surrounding the technicians, a $31 million addition to GE's plant on Route 29 is being built to manufacture new computer systems called numerical controllers, designed to provide microscopic direction over the cutting, drilling and shaping machines used throughout industry.

By next year, GE expects to have 2,000 employes at the Charlottesville plant, strengthening its position as the second-largest private-sector employer in Virginia, behind Newport News Shipbuilding Co. GE has some 15,000 Virginia employes in Lynchburg, Waynesboro and Salem, as well as in Charlottesville.

The Charlottesville venture represents an uncharacteristic gamble by GE: The plant is going up, several hundred additional scientists have been hired, but GE will not know until next spring whether its new numerical control device lives up to expectations, says GE Senior Vice President Donald K. Grierson, head of the company's industrial electronics group. But GE is obliged to gamble in the race to automate factories with a far-out family of robots, computer-aided design systems and machine controllers.

After dropping out of both the computer business and the manufacture of integrated circuits for computers a decade ago, GE fell behind top competitors in the United States, Japan and Europe in the fast-moving use of electronics to improve manufacturing quality and control.

"We got out of integrated circuits because we were conservative at the time and vast amounts of money would have been required to keep up with Texas Instruments and some other people," GE Executive Vice President James A. Baker says. "We got out of computers eventually, because we were chasing IBM, and that was quite a chase."

GE's task now is to "catch a moving train," says Grierson. The stakes are great--GE estimates that two-thirds of its sales by 1990 will be in products that employ microelectronics.

Its catch-up plans have included the purchase of two California technology companies:

Calma Co., a manufacturer of computer-aided design and drafting equipment, at a price that may reach $170 million, depending on Calma's sales over the next four years.

Intersil Inc., a manufacturer of advanced integrated circuits used to control automated factory processes, acquired for $235 million.

GE has also begun a $10 million joint venture with Structural Dynamics Research Corp., of Cincinnati, to produce and sell computer-aided engineering systems. SDRC successes include a safety analysis of the heat shield on the space shuttle Columbia, and the down-sizing of new U. S. and Japanese front-wheel-drive cars.

GE will use its General Electric Information Services Co., in Rockville, to provide central computer processing for companies that don't have the necessary capacity themselves, and its credit subsidiary will offer financing to new customers.

"We want to make it possible for companies to evolve gracefully into higher and higher degrees of automation without having to throw out what they've already bought, Grierson said.

Grierson's job is to make these elements of a "polygamous marriage" work together so that the breadth of GE's products and services overcome its late entry into the robot factory-automation field.

"My goal is to create a $5 billion business certainly before the end of the decade. We're well over $1 billion now," Grierson said. "I'd say we'll get there at about 1:30 p.m. on July 1, 1987," he added with a grin.

The new machines being developed for Charlottesville are an essential step in that direction, Grierson said, and GE hopes to have the 2,000 employes at Charlottesville producing 3,000 to 5,000 of the machines by 1983.

Automated numerical controls are programmed to guide machine tools that cut and shape metal parts for aircraft, autos and other products. Although GE has produced electronic controls for equipment and machinery since World War II, the new product line is designed to provide greater accuracy than current models, while making it easier for plant operators to reprogram the controls on the plant floor as machining requirements change.

The new GE products will have to compete against Japanese models in quality. GE technicians are trying to produce a controller that will run 20,000 hours without a breakdown and thus far believe they can reach 9,000 hours--about three years of plant operation.

Eventually, numerical controllers can be linked to the computer-aided design (CAD) systems that Calma manufactures, Grierson said, that permit designers to create three dimensional, color-coded images of complex industrial components on the television-like screens of the CAD terminals.

The designs can be subjected to computer-simulated heat, vibration or other stresses and free-hand corrections made on the terminal screens with an electronic pencil.

The final design will be transmitted to numerical controllers, Grierson said, which will instruct the machine tools how to shape the part. The computer system will also permit minute inspection of manufactured components.

GE predicts that improvements in quality and productivity that such systems permit will create a $25 billion market by 1990.