Design for additive manufacturing

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Design for additive manufacturing (DfAM or DFAM) is design for manufacturability as applied to additive manufacturing (AM). It is a general type of design methods or tools whereby functional performance and/or other key product life-cycle considerations such as manufacturability, reliability, and cost can be optimized subjected to the capabilities of additive manufacturing technologies.[1]

This concept emerges due to the enormous design freedom provided by AM technologies. To take full advantages of unique capabilities from AM processes, DFAM methods or tools are needed. Typical DFAM methods or tools includes topology optimization, design for multiscale structures (lattice or cellular structures), multi-material design, mass customization, part consolidation, and other design methods which can make use of AM-enabled features.

DFAM is not always separate from broader DFM, as the making of many objects can involve both additive and subtractive steps. Nonetheless, the name "DFAM" has value because it focuses attention on the way that commercializing AM in production roles is not just a matter of figuring out how to switch existing parts from subtractive to additive. Rather, it is about redesigning entire objects (assemblies, subsystems) in view of the newfound availability of advanced AM. That is, it involves redesigning them because their entire earlier design—including even how, why, and at which places they were originally divided into discrete parts—was conceived within the constraints of a world where advanced AM did not yet exist. Thus instead of just modifying an existing part design to allow it to be made additively, full-fledged DFAM involves things like reimagining the overall object such that it has fewer parts or a new set of parts with substantially different boundaries and connections. The object thus may no longer be an assembly at all, or it may be an assembly with many fewer parts. Many examples of such deep-rooted practical impact of DFAM have been emerging in the 2010s, as AM greatly broadens its commercialization. For example, in 2017, GE Aviation revealed that it had used DFAM to create a helicopter engine with 16 parts instead of 900, with great potential impact on reducing the complexity of supply chains.[2] It is this radical rethinking aspect that has led to themes such as that "DFAM requires 'enterprise-level disruption'."[3] In other words, the disruptive innovation that AM can allow can logically extend throughout the enterprise and its supply chain, not just change the layout on a machine shop floor.

DFAM involves both broad themes (which apply to many AM processes) and optimizations specific to a particular AM process. For example, DFM analysis for stereolithography maximizes DFAM for that modality.

Background[edit]

Additive manufacturing is defined as a material joining process, whereby a product can be directly fabricated from its 3D model, usually layer upon layer.[4] Comparing to traditional manufacturing technologies such as CNC machining or casting, AM processes have several unique capabilities. It enables the fabrication of parts with a complex shape as well as complex material distribution.[5] These unique capabilities significantly enlarge the design freedom for designers. However, they also bring a big challenge. Traditional Design for manufacturing (DFM) rules or guidelines deeply rooted in designers’ mind and severely restrict designers to further improve product functional performance by taking advantages of these unique capabilities brought by AM processes. Moreover, traditional feature-based CAD tools are also difficult to deal with irregular geometry for the improvement of functional performance. To solve these issues, design methods or tools are needed to help designers to take full advantages of design freedom provide by AM processes. These design methods or tools can be categorized as Design for Additive Manufacturing

Methods[edit]

Topology optimization[edit]

Topology optimization is a type of structural optimization technique which can optimize material layout within a given design space. Compared to other typical structural optimization techniques, such as size optimization or shape optimization, topology optimization can update both shape and topology of a part. However, the complex optimized shapes obtained from topology optimization are always a headache for traditional manufacturing processes such as CNC machining. To solve this issue, additive manufacturing processes can be applied to fabricate topology optimization result. However, it should be noticed, some manufacturing constraints such as minimal feature size also need to be considered during the topology optimization process.[6] Since the topology optimization can help designers to get an optimal complex geometry for additive manufacturing, this technique can be considered one of DFAM methods.

Multiscale structure design[edit]

Due to the unique capabilities of AM processes, parts with multiscale complexities can be realized. This provides a great design freedom for designers to use cellular structures or lattice structures on micro or mesoscales for the preferred properties. For example, in the aerospace field, lattice structures fabricated by AM process can be used for weight reduction.[7] In the bio-medical field, bio-implant made of lattice or cellular structures can enhance osseointegration.[8]

Multi-material design[edit]

Parts with multi-material or complex material distribution can be achieved by additive manufacturing processes. To help designers to take use of this advantage, several design and simulation methods [9][10][11] has been proposed to support design a part with multiple materials or Functionally Graded Materials . These design methods also bring a challenge to traditional CAD system. Most of them can only deal with homogeneous materials now.

Design for mass customization[edit]

Since additive manufacturing can directly fabricate parts from products’ digital model, it significantly reduces the cost and leading time of producing customized products. Thus, how to rapidly generate customized parts becomes a central issue for mass customization. Several design methods [12] have been proposed to help designers or users to obtain the customized product in an easy way. These methods or tools can also be considered as the DFAM methods.

Parts consolidation[edit]

Due to the constraints of traditional manufacturing methods, some complex components are usually separated into several parts for the ease of manufacturing as well as assembly. This situation has been changed by the using of additive manufacturing technologies. Some case studies have been done to shows some parts in the original design can be consolidated into one complex part and fabricated by additive manufacturing processes. This redesigning process can be called as parts consolidation. The research shows parts consolidation will not only reduce part count, it can also improve the product functional performance.[13] The design methods which can guide designers to do part consolidation can also be regarded as a type of DFAM methods.

References[edit]

  1. ^ Tang, Yunlong (2016). "A survey of the design methods for additive manufacturing to improve functional performance". Rapid Prototyping Journal. 22 (3). 
  2. ^ Zelinski, Peter (2017-03-31), "GE team secretly printed a helicopter engine, replacing 900 parts with 16", Modern Machine Shop, retrieved 2017-04-09. 
  3. ^ Hendrixson, Stephanie (2017-04-24), "How to think about design for additive manufacturing", Modern Machine Shop, retrieved 2017-05-05. 
  4. ^ "ASTM F2792 - 12a Standard Terminology for Additive Manufacturing Technologies, (Withdrawn 2015)". www.astm.org. Retrieved 2016-09-03. 
  5. ^ Gibson, Dr Ian; Rosen, Dr David W.; Stucker, Dr Brent (2010-01-01). Additive Manufacturing Technologies. Springer US. pp. 299–332. ISBN 9781441911193. 
  6. ^ Leary, Martin; Merli, Luigi; Torti, Federico; Mazur, Maciej; Brandt, Milan (2014-11-01). "Optimal topology for additive manufacture: A method for enabling additive manufacture of support-free optimal structures". Materials & Design. 63: 678–690. doi:10.1016/j.matdes.2014.06.015. 
  7. ^ Tang, Yunlong; Kurtz, Aidan; Zhao, Yaoyao Fiona (2015-12-01). "Bidirectional Evolutionary Structural Optimization (BESO) based design method for lattice structure to be fabricated by additive manufacturing". Computer-Aided Design. 69: 91–101. doi:10.1016/j.cad.2015.06.001. 
  8. ^ Schmidt, M.; Zaeh, M.; Graf, T.; Ostendorf, A.; Emmelmann, C.; Scheinemann, P.; Munsch, M.; Seyda, V. (2011-01-01). "Lasers in Manufacturing 2011 - Proceedings of the Sixth International WLT Conference on Lasers in ManufacturingLaser Additive Manufacturing of Modified Implant Surfaces with Osseointegrative Characteristics". Physics Procedia. 12: 375–384. doi:10.1016/j.phpro.2011.03.048. 
  9. ^ Zhang, Feng; Zhou, Chi; Das, Sonjoy (2015-08-02). "An Efficient Design Optimization Method for Functional Gradient Material Objects Based on Finite Element Analysis": V01AT02A031. doi:10.1115/DETC2015-47772. 
  10. ^ Zhou, Shiwei; Wang, Michael Yu (2006-07-18). "Multimaterial structural topology optimization with a generalized Cahn–Hilliard model of multiphase transition". Structural and Multidisciplinary Optimization. 33 (2): 89. doi:10.1007/s00158-006-0035-9. ISSN 1615-147X. 
  11. ^ Stanković, Tino; Mueller, Jochen; Egan, Paul; Shea, Kristina (2015-08-02). "Optimization of Additively Manufactured Multi-Material Lattice Structures Using Generalized Optimality Criteria". 
  12. ^ Reeves, Phil; Tuck, Chris; Hague, Richard (2011-01-01). Fogliatto, Flavio S.; Silveira, Giovani J. C. da, eds. Mass Customization. Springer Series in Advanced Manufacturing. Springer London. pp. 275–289. ISBN 9781849964883. 
  13. ^ Yang, Sheng; Tang, Yunlong; Zhao, Yaoyao Fiona (2015-10-01). "A new part consolidation method to embrace the design freedom of additive manufacturing". Journal of Manufacturing Processes. Additive Manufacturing. 20, Part 3: 444–449. doi:10.1016/j.jmapro.2015.06.024.