The robot maker just lost its second co-founder in as many months. On Wednesday, Helen Greiner stepped down from her post as chairman of iRobot, leaving only CEO Colin Angle as the remaining co-founder of the company. Coming as it does just a month after the resignation of Rodney Brooks, iRobot’s co-founder and CTO, Greiner’s departure is a bit of a surprise. And the company, which just reported a better-than-expected profit in its third quarter, offered little explanation for it. “She’ll be a passionate advocate of the industry,” said iRobot spokesperson Nancy Dussault-Smith. “Helen’s in a good place. She’s always been someone who’s been entrepreneurial. She’s a robot person through and through, and she’s going to stay in the robot business.”