Cognex Drops on Warning

Cognex

(CGNX) - Get Report

, a maker of machine vision technology, was down 40.3% in preopen

Island

trading. Late Monday, the company said it expects earnings of 36 cents a share for the fourth quarter, well below the

First Call/Thomson Financial

estimate of 46 cents. The company blamed an order slowdown from semiconductor and electronics customers.

Robertson Stephens

downgraded the stock to long-term attractive from a buy.