A method of layer height control in direct laser fabrication of 304L stainless steel

Direct Laser Fabrication is a blown powder laser deposition process capable of producing fully dense metallic parts by a layered manufacturing method. The process has applications in the fields of rapid manufacture and the repair or modification of existing metallic parts. However, a common problem encountered with this technique is the unwanted variation of layer height during the deposition process. This variation can lead to non-uniformity of the build and a deviation from required tolerances. Investigation of methods of delivery of powder to the laser-generated melt pool has resulted in a means of ensuring the deposition of consistent and controllable layer heights under a variety of process conditions. This paper describes how this is achieved while using an in house four port powder delivery nozzle. The process is demonstrated for the manufacture of 304L stainless steel samples and shows control of cumulative height errors in multilayer builds. In addition, the ability of the powder delivery system to deliver a near-constant layer height for different layer deposition parameters and to allow the generation of a variety of consistent layer heights for a single set of process parameters is illustrated.