Design guidelines for laser metal deposition of lightweight structures

Abstract

The additive manufacturing technology laser metal deposition (LMD) serves a high degree of freedom. For an effective industrial application, it is necessary to identify all advantages and disadvantages. A lowering of the introduction barrier can be achieved with design guidelines helping the engineer early in the product development. With LMD as an additive manufacturing process like selective laser melting (SLM), existing manufacturing guidelines cannot be simply adopted. Due to the complex process constraints, a specific design guideline for LMD has been established. LMD is a layer-by-layer additive manufacturing process that builds parts based on a nozzle-fed powder which is solidified by a laser. The process can be used for surface cladding, repair, and build-up of parts. Different from powder-bed additive technologies, like SLM, the LMD process has different process restrictions. To use the advantages of LMD, the design engineer needs to have knowledge of the limitations of LMD. LMD offers a high degree of freedom in the design of parts and simultaneously offers great potential for weight savings and reduction of manufacturing time. This is especially relevant in lightweight applications, e.g., in the aerospace industry. Complex parts often share simple geometries as a basis. These shapes were identified and used to evaluate the applicability and effectiveness of LMD. Following established lightweight design guidelines, the presented guideline also focuses on fine structures. In addition to the manufacturability, the building accuracy and the surface roughness have been investigated, since both have a significant influence on the product quality and the necessity of post-processing towards the final shape of a part. The results were summarized in a design guideline according to the VDI 2222. This catalog supports the design using LMD as an additive technology.