▁fabric ate ▁an ▁object ▁layer ▁by ▁layer . ▁The ▁de position ▁head ▁is ▁moved ▁up ▁vert ically ▁as ▁each ▁layer ▁is ▁completed . ▁Metal ▁pow der ▁is ▁delivered ▁and ▁distributed ▁around ▁the ▁circum ference ▁of ▁the ▁head ▁or ▁can ▁be ▁split ▁by ▁an ▁internal ▁manifold ▁and ▁delivered ▁through ▁no zz les ▁arranged ▁in ▁various ▁configurations ▁around ▁the ▁de position ▁head . ▁A ▁herm et ically ▁se aled ▁chamber ▁filled ▁with ▁in ert ▁gas ▁or ▁a ▁local ▁in ert ▁shr oud ▁gas ▁is ▁often ▁used ▁to ▁shield ▁the ▁m elt ▁pool ▁from ▁atmos pher ic ▁o xygen ▁for ▁better ▁control ▁of ▁material ▁properties . ▁The ▁pow der ▁fed ▁directed ▁energy ▁process ▁is ▁similar ▁to ▁Select ive ▁Las er ▁S inter ing , ▁but ▁the ▁metal ▁pow der ▁is ▁applied ▁only ▁where ▁material ▁is ▁being ▁added ▁to ▁the ▁part ▁at ▁that ▁moment . ▁The ▁process ▁supports ▁a ▁wide ▁range ▁of ▁materials ▁including ▁tit an ium , ▁st ain less ▁steel , ▁al umin um , ▁and ▁other ▁special ty ▁materials ▁as ▁well ▁as ▁compos ites ▁and ▁function ally ▁grad ed ▁material . ▁The ▁process ▁can ▁not ▁only ▁fully ▁build ▁new ▁metal ▁parts ▁but ▁can ▁also ▁add ▁material ▁to ▁existing ▁parts ▁for ▁example ▁for ▁coat ings , ▁repair , ▁and ▁hy brid ▁manufact uring ▁applications . ▁L EN S ▁( L aser ▁Engine ered ▁Net ▁Sh aping ), ▁which ▁was ▁developed ▁by ▁Sand ia ▁National ▁L abs , ▁is ▁one ▁example ▁of ▁the ▁Pow der ▁Fed ▁- ▁Direct ed ▁Energy ▁De position ▁process ▁for ▁ 3