Patents do explain some of this delay.... Fused Deposition Modeling or FDM (1989, expired in 2009), Liquid-Based Stereolithography or SLA (1986, expired in 200

Patents do explain some of this delay.... Fused Deposition Modeling or FDM (1989, expired in 2009), Liquid-Based Stereolithography or SLA (1986, expired in 2006), Selective Laser Sintering or SLS (1992, expired in 2012), metal processes like Selective Laser Melting (SLM) and Direct Metal Laser Sintering (DMLS) (1996, expired 2016).