MAPLE PLAIN, Minn.--(BUSINESS WIRE)--Proto Labs, Inc. (NYSE: PRLB), a leading online and technology-enabled, quick-turn, on-demand manufacturer, today announced financial results for the second quarter ended June 30, 2015. Highlights include: Revenue for the second quarter of 2015 increased to a record $64.0 million, 21 percent above revenue of $52.9 million in the second quarter of 2014. On a constant currency basis, revenue was up 25 percent versus the prior year. Revenue from additive servic