Additive manufacturing (AM) has gained increased attention in the last decade as a versatile manufacturing process for customized products. AM processes can create complex free-form shapes, introducing features such as internal cavities and lattices. These complex geometries are either not feasible or very costly with traditional manufacturing processes. This creates new challenges in maintaining and communicating dimensional and geometric accuracy of parts produced. In order to manufacture a product that meets functional needs, the specification of those needs through geometry, material and tolerances is necessary. This paper surveys the current state and needs of geometry related accuracy specification mechanisms for AM, including a review of specification standards such as ASME Y14.5 and ISO 1101. Emerging AM-related tolerancing challenges are identified, and a potential plan of action is put forth for addressing those challenges.
Various issues highlighted in this paper are classified as (a) AM-driven specification issues and (b) specification issues highlighted by the versatility of AM processes. AM-driven specification issues include build direction, layer thickness, support structure related specification, and scan/track direction. Specification issues highlighted by the versatility of AM processes include, region-based tolerances for complex freeform surfaces, tolerancing internal functional features, tolerancing lattice and infills. Basic methods of solving these specification issues are also highlighted.