Manufacturability Constraint Formulation for Design Under Hybrid Additive-Subtractive Manufacturing

Abstract

This article addresses the generation and use of manufacturability constraints for design under hybrid additive/subtractive processes. A method for discovering the natural constraints inherent in both additive and subtractive processes is developed; once identified, these guidelines can be converted into mathematical manufacturability constraints to be used in the formulation of design problems. This ability may prove to be useful by enhancing the practicality of designs under realistic hybrid manufacturing conditions, and supporting better integration of classic design-for-manufacturability principles with design and solution methods. A trade-off between design manufacturability and elegance has been noted by many scholars. It is posited that using realistic manufacturing conditions to drive design generation may help manage this trade-off more effectively, focusing exploration efforts on designs that satisfy more comprehensive manufacturability considerations. While this study focuses on two-step AM-SM hybrid processes, the technique extends to other processes, including single-process fabrication. Two case studies are presented here to demonstrate the new constraint generation concept, including formulation of shape and topology optimization problems, comparison of results, and the physical fabrication of hybrid-manufactured products. Ongoing work is aimed at rigorous comparison between candidate constraint generation strategies and the properties of the constraint mapping.

Exploring an AM-Enabled Combination-of-Functions Approach for Modular Product Design

“…It differs from typical mathematical approaches as it focuses the bulk of design resources on the optimization of a single characteristic or a small set of them. Design-for-X approaches can also be used to generate design constraints to be used for a mathematical approach to designing the system [29].…”

“…The most important restrictions on the use of this design methodology are the physical size of parts, the available batch sizes, material requirements, and the designer's level of skill and experience with the technologies. In addition to these concerns, the designer must also ensure that the proper design-for-manufacturability constraints [29] are applied on the design to ensure that it is feasible for AM. Not all parts and systems will be best made using AM; this determination should be made early in the design process and the AMEMD only used if the complex parts can be feasibly made using AM.…”

“…The process families are defined according to the state of the raw material before processing, the method of material deposition, and method of layer fusion. Consideration of the distinction between processes is important because various processes have different strengths and weaknesses for different applications [17,28,29]. Reduced integration complexity within many systems or products can serve to increase their reliability, giving a longer useful life and higher customer satisfaction.…”

“…From the manufacturing perspective, AM processes tend to be at least as restrictive, if not more, in terms of manufacturability constraints than traditional processes. [29,[48][49][50] The layer-based nature of all AM processes produce anisotropic material properties in the final parts [17,[51][52][53] , the surface finish of final parts can be poor [17,[54][55][56] , and the inherent residual stresses from some processes can dramatically reduce the fatigue life of the parts [57][58][59] . Due to these and other considerations, AM-made parts can be prone to fracture and may have poor dimensional accuracy for some processes and materials.…”

Practical DOE-Based Approach for Predicting Impact of Stress and Deformation in SLM Overhanging Features During Product Design

“…When designing parts that will be manufactured using any AM process (and especially so in very sensitive processes such as SLM), it is important to incorporate DFM principles whenever possible. DFM provides tools both for mitigating potential manufacturing problems from the inherent weaknesses of a process and for providing insight into extra design benefits that may be available when using a particular process [5,9,10,11].…”