Additive manufacturing (AM) is poised to bring about a revolution in the way products are designed, manufactured, and distributed to end users. This technology has gained significant academic as well as industry interest due to its ability to create complex geometries with customizable material properties. AM has also inspired the development of the maker movement by democratizing design and manufacturing. Due to the rapid proliferation of a wide variety of technologies associated with AM, there is a lack of a comprehensive set of design principles, manufacturing guidelines, and standardization of best practices. These challenges are compounded by the fact that advancements in multiple technologies (for example materials processing, topology optimization) generate a "positive feedback loop" effect in advancing AM. In order to advance research interest and investment in AM technologies, some fundamental questions and trends about the dependencies existing in these avenues need highlighting. The goal of our review paper is to organize this body of knowledge surrounding AM, and present current barriers, findings, and future trends significantly to the researchers. We also discuss fundamental attributes of AM processes, evolution of the AM industry, and the affordances enabled by the emergence of AM in a variety of areas such as geometry processing, material design, and education. We conclude our paper by pointing out future directions such as the "print-it-all" paradigm, that have the potential to re-imagine current research and spawn completely new avenues for exploration. The fundamental attributes and challenges/barriers of Additive Manufacturing (AM).The evolution of research on AM with a focus on engineering capabilities.The affordances enabled by AM such as geometry, material and tools design.The developments in industry, intellectual property, and education-related aspects.The important future trends of AM technologies.

The status, challenges, and future of additive manufacturing in engineering

Purpose – The purpose of this paper is to investigate the mechanisms controlling the bond formation among extruded polymer filaments in the fused deposition modeling (FDM) process. The bonding phenomenon is thermally driven and ultimately determines the integrity and mechanical properties of the resultant prototypes.Design/methodology/approach – The bond quality was assessed through measuring and analyzing changes in the mesostructure and the degree of healing achieved at the interfaces between the adjoining polymer filaments. Experimental measurements of the temperature profiles were carried out for specimens produced under different processing conditions, and the effects on mesostructures and mechanical properties were observed. Parallel to the experimental work, predictions of the degree of bonding achieved during the filament deposition process were made based on the thermal analysis of extruded polymer filaments.Findings – Experimental results showed that the fabrication strategy, the envelope temper...

Effect of processing conditions on the bonding quality of FDM polymer filaments

Additive manufacturing: A framework for implementation

Purpose – The purpose of this paper is to critically review the literature related to dimensional accuracy and surface roughness for fused deposition modeling and similar extrusion-based additive manufacturing or rapid prototyping processes. Design/methodology/approach – A systematic review of the literature was carried out by focusing on the relationship between process and product design parameters and the dimensional and surface properties of finished parts. Methods for evaluating these performance parameters are also reviewed. Findings – Fused deposition modeling® and related processes are the most widely used polymer rapid prototyping processes. For many applications, resolution, dimensional accuracy and surface roughness are among the most important properties in final parts. The influence of feedstock properties and system design on dimensional accuracy and resolution is reviewed. Thermal warping and shrinkage are often major sources of dimensional error in finished parts. This phenomenon is explor...

A review of melt extrusion additive manufacturing processes: II. Materials, dimensional accuracy, and surface roughness

Surface finish and part deposition time are two important concerns in rapid prototyping (RP). These two concerns contradict with each other. Generally, a compromise is made between the two aspects pertaining to model building in RP. A compromise between these two contradicting issues can be achieved by using an adaptive slicing scheme; however, selection of a proper part deposition orientation will further provide an improved solution. Present work is an attempt towards obtaining an optimum part deposition orientation for fused deposition modeling process for enhancing part surface finish and reducing build time. Models for evaluation of average part surface roughness and build time are developed. A real coded genetic algorithm is used to obtain the optimum solution. Predictions of the present metzhodology are in good agreement with the result published earlier. Proposed methodology can be used to obtain the optimum deposition orientation for any type of component without selecting the preferred orientations.

Optimum part deposition orientation in fused deposition modeling

Layered manufacturing (LM) is emerging as a new manufacturing technology that can enhance the scope of manufacturing. One of the essential tasks in LM is process planning. This paper defines, conceptualizes and reviews the literature in this emerging area. The paper concludes with future projections on the possible directions of research in this area.

A review of process planning techniques in layered manufacturing

Improving the geometric accuracy of layer manufactured parts has assumed greater significance as these processes are being integrated into manufacturing, instead of just being used for look-and-feel prototyping. In this paper, we describe two factors associated with the slicing procedures used in layered manufacturing processes that introduce geometric inaccuracy, and suggest solutions for their redressal. Implemented examples are included to explain the procedure.

An accurate slicing procedure for layered manufacturing

In the Fused Deposition Modeling (FDM) process, the choice of deposition strategy plays an important role. In this paper, the effects of different deposition paths on this deposition based LM process are investigated. Some variations on the current deposition strategie are also proposed. The stiffness of parts manufactured by the different strategies is experimentally determined. It is then compared with an analytical model developed using laminate analysis. A good conformance of the laminate model to the experimental results suggests that the laminate model can be used as a design aide to help the designer tailor the deposition strategy to the stiffness requirements.

Deposition Strategies and Resulting Part Stiffnesses in Fused Deposition Modeling

In this paper, we describe a method for region-based adaptive slicing. Whereas in traditional adaptive slicing the user can impose a single surface finish (cusp height) requirement for the whole object, in region-based adaptive slicing, user has the flexibility to impose different surface finish requirements on different surfaces of the model. We describe the method and its implementation. Two example parts were built using the slicing technique and the results are included.

Region-based adaptive slicing

In this paper, we develop methodologies for the integration of layered manufacturing and traditional material removal processes into an integrated manufacturing setup, The scenarios under which this integration would be beneficial are identified and algorithms for the integration developed. As examples, we consider two current layered manufacturing technologies that use material removal operations as a part of their process. The benefits of our procedure are demonstrated by examples.

Prashant Kulkarni

Papers

A review of process planning techniques in layered manufacturing

An accurate slicing procedure for layered manufacturing

Deposition Strategies and Resulting Part Stiffnesses in Fused Deposition Modeling

Region-based adaptive slicing

On the Integration of Layered Manufacturing and Material Removal Processes