Saying it wants to ensure stable supplies...

Saying it wants to ensure stable supplies for its copy machine customers, a Tustin-based unit of Toshiba America Inc. said it has agreed to buy a 3M Corp. factory in South Dakota that produces toner powders.

The Toshiba Corp.’s industrial electronics business division would not disclose the price of the Mitchell, S.D., plant. Toshiba America of New York is the U.S. arm of Toshiba Corp., the Tokyo-based electronics giant.

The company, which estimates it supplies 15% of the plain paper copiers sold in the United States, said it plans to more than double production of toner powders at the plant to 2,700 tons a year by 1989. Toshiba estimates production next year at 1,200 tons. The company said that it had planned to develop production of toners but decided to try to buy the Mitchell plant when it learned that 3M had decided to get out of the business.