Cipher Data will close its Garden Grove plant.

Cipher Data Products said it will lay off at least 300 and as many as 450 employees between now and June, 1987, as it prepares to shut down its Garden Grove computer parts manufacturing facility and move much of its production to Singapore. “We must have cost savings to stay in the market,� Cipher spokesman Peter E. McGuirk said. The San Diego-based maker of computer tape and disk drives began the year with a 2,400 employee work force and has already laid off 300 employees--about 200 of those in Garden Grove.