The 3D Printing OEM market was on fire in 2013 as evidenced by the stock appreciation of pure-play printer manufacturers: 3D Systems (NYSE:DDD) 93%, Stratasys (NASDAQ:SSYS) 48%, VoxelJet (NASDAQ:VJET) 90%, Exone Company (NASDAQ:XONE) 226%, Organovo (NASDAQ:ONVO) 399%. In the latter half of 2013 IPOs with just about anything to do with 3D Printing - such as Cimatron Ltd., Groupe Gorge, Arc Group Worldwide - received immediate attention from investors. Surprisingly Sigma Labs (OTC: SGLB), one of the most interesting stories in this market, is still widely unknown and often misunderstood. For most investors who do not consider micro-cap stocks for investing I would ask