US robotics company iRobot Corp. has added a new vacuum cleaning robot to its stable of cleaning devices: the Roomba 600 Series. The new unit incorporates optimized airflow and an improved brush design for more thorough and effective cleaning. Pricing starts at $329, according to the company. In addition, iRobot has rolled out the Looj 330, a robot that uses a high-velocity, four-stage auger to blast away leaves, dirt and clogs while brushing gutters clean. “iRobot has sold more t...