Just as steel's physical properties change depending on how it's produced, so too do 3D printed materials. However, unlike steel, we don't yet fully understand how different these newfound techniques affect the resulting printed item. Sometimes a printed item -- even if it's made from something common like aluminum -- ends up having a very different microstructure had it been created with traditional, subtractive methods. You can see an example of that below. Heck, even using the same material on different printer models can result items with wildly divergent properties. But DARPA is looking to change that. The DoD's advanced research agency announced Friday that it is launching an Open Manufacturing program to create comprehensive reference documentation for 3D printing and usher in an era of productive predictability.