OXFORD, Mass.--(BUSINESS WIRE)--IPG Photonics Corporation (NASDAQ: IPGP) today reported financial results for the second quarter ended June 30, 2015.     Three Months EndedJune 30,     Six Months EndedJune 30,   (In millions, except per share data) 2015   2014 % Change 2015   2014 % Change Revenue $ 235.1 $ 192.2 22 % $ 434.1 $ 362.8 20 % Gross margin 54.7 % 54.2 % 54.5 % 53.3 % Operating income $ 87.4 $ 68.7 27 % $ 169.5 $ 126.5 34 % Operating margin 37.2 % 35.8 % 39.0 % 34.9 % Net income attr