To Örebro University

Additive Manufacturing (AM) using Powder Bed Fusion (PBF) allows part with abstract shapes, that otherwise would need costly tooling, to be manufactured with short lead time. In this study AM build time simulations are used to predict series part cost for eight parts that are possible to cut from rod blanks using High Speed Machining (HSM). Results indicate that when the part shape can be cut from rod blanks, AM is more expensive than HSM even for series of one. If post processing machining is added to the printed AM blank part, the cost difference increases further. Finally, the model is used to predict part-cost in series production if print speed increases, if machine cost is reduced or if part mass is reduced as a result of redesign for AM.

3D-printing has been used to create prototypes during the development phase for more than 20 years. Now, functional parts can be printed directly in specific metal powders using similar layer-by-layer techniques. The additive method is unlike traditional mass production manufacturing methods in many ways, creating new possibilities for designers to realise new and different design ideas previously impossible to manufacture. When products are mass produced, there is a desire to improve manufacturability. This is traditionally done by a designer with knowledge about certain manufacturing methods altering design choices to make it cheaper to manufacture.

This paper shows different design for AM (DfAM) methods where performance and part cost are both of interest. It adds to existing research by classifying design for additive manufacturing in two different classes; process-driven and designer-driven shaping of parts. A cost-prediction model for Selective Laser Melting (SLM) printed parts is suggested as an initial step to choose parts for redesign from an economical perspective. A case study of a missile launcher beam redesigned for additive manufacturing using three different approaches is presented. Differences and similarities in design methods are discussed and the redesigned parts are compared for mass and cost. It is shown that redesigning for AM can reduce mass but depending on part size and print speed, the part can become more expensive than the original design, creating a need to know the customer value of what the redesigned part provides, in this case, the value of reduced mass.

3D data exchange between different CAD systems and from design to manufacturing has largely moved to ISO STEP based formats. The Additive Manufacturing (AM) process today requires an approximate, planar triangle tessellated 3D model as an input. Improving accuracy in STL file exports is done differently in different CAD systems. Poor tessellation accuracy results in built parts with poor geometric accuracy because of errors in source data. In this study, results of tessellation from six different CAD systems are compared. Roundness accuracy for the different settings is calculated. Results show that tessellation effects may be visible even when roundness requirements are fulfilled. A method for 3D data exchange for AM using STEP and geometric requirements is proposed until better accuracy AM formats can be used.