Search results

The purpose of this paper is to report a new direct metal manufacturing method which integrates freeform deposition process and micro rolling process, introduce the manufacturing principle and show the advantages of this method.

This paper introduces the hybrid manufacturing principle and devices first. Then, the key parameters of hybrid manufacturing process are studied by contrast experiments. The results of comparisons of manufacturing accuracy, microstructure and tensile test between freeform fabricated parts and hybrid manufactured parts show the advantages of this new direct manufacturing method.

The experiments results show that the accuracy of hybrid manufacturing method is improved obviously comparing with arc-based freeform deposition manufacturing method; the microstructure of the hybrid manufacturing part turns into cellular crystal instead of dendrite; the tensile strength of the part increases by 33 percent and the tensile deformation improved more than two times.

The paper presents a new hybrid direct metal manufacturing method for the first time. The hybrid manufacturing devices are developed. The experiments results show that the hybrid manufacturing method can be used on directly fabricating large metal components with outstanding quality, efficiency and low cost. The application prospect is great.

The third part of a comprehensive six‐part series on a promising and growing approach to mechanical attachment amenable to automation. Integral snap‐fit attachment design has traditionally focused almost exclusively on the individual features that actually accomplish locking between parts of an assembly (e.g. cantilever hooks, bayonet‐fingers, compressive hooks, traps, and others). The placement and orientation of features that facilitate or enhance engagement or eliminate unwanted translation, rotation or vibration, i.e. locating features and enhancements, are rarely considered. Here, describes integral features classified as locks, locators or enhancements. More importantly, presents a systematic six‐step approach or methodology to guide designers at the higher, attachment or conceptual design level (as opposed to lower, feature or detail design level).

In an effort to directly manufacture devices with embedded complex and three‐dimensional (3D) micro‐channels on the order of microns to millimeters, issues associated with micro‐fabrication using current commercially available line‐scan stereolithography (SL) technology were investigated.

Practical issues associated with the successful fabrication of embedded micro‐channels were divided into software part preparation, part manufacture, and post‐cleaning with emphasis on channel geometry, size, and orientation for successful micro‐fabrication. Accurate representation of intended geometries was investigated during conversion from CAD to STL and STL to machine build file, and fabricated vertical and horizontal micro‐channels were inspected. Additional build issues investigated included accurate spatial registration of the build platform, building without base support, and Z‐stage position accuracy during the build.

For successful fabrication of micro‐channels using current technology, it is imperative to inspect the conversion process from CAD to STL and STL to machine build file. Inaccuracies in micro‐channel representation can arise at different stages of part preparation, although newer software versions appear to improve representation of micro‐geometries. Square channel cross‐sections are most easily sliced and vertical channels are most easily stacked together for layered manufacturing. While building, a means should be developed for building without base and internal supports, providing feedback on Z‐stage position, and having the capability for cleaning the micro‐channels.

This research demonstrates that commercial SL technology is capable of accurately fabricating embedded vertical square cross‐section micro‐channels on the order of 100 μm (with reasonable advancements to smaller scales on the order of 10 μm achievable). Additional practical limitations exist on other channel geometries and orientations. The research used a single resin and additional material resins should be explored for improved micro‐fabrication characteristics.

Practical issues associated with micro‐fabrication of embedded channels with appropriate solutions using available SL technology were provided. It is expected that these solutions will enable unique applications of micro‐channel fabrication for micro‐fluidic and other devices.

This work represents an original investigation of the capabilities of current line‐scan SL technology for fabricating embedded micro‐channels, and the solutions provide the means for applying this technology in micro‐fabrication.

The purpose of this paper is to describe an original algorithm for point location of assembly features. Decomposing a model into several parts, for its manufacture using machine‐tools with limited dimensional capabilities, requires appropriate model reassembly. Generating and positioning assembly features are required for interlocked positioning of various parts.

An algorithm is presented for the automated generation of assembly features over the decomposition surface.

A skeleton‐based point location method is proposed and its results are discussed with respect to placements achieved on a grid.

The algorithm describes the placement of features on the planar decomposition surface. Future work will allow its generalization to a 3D surface.

A series of tests made with various parts is described, and an application of this algorithm is presented in a layered manufacturing process.

This paper describes an original algorithm for point location of assembly features which makes it straightforward to reassemble a decomposed part such as in layered manufacturing.

This paper aims to provide a multi-objective optimization problem in design for manufacturing (DFM) approach for fused deposition modeling (FDM). This method considers the manufacturing criteria and constraints during the design by selecting the best manufacturing parameters to guide the designer and manufacturer in fabrication with FDM.

Topological optimization and bi-objective optimization problems are suggested to complete the DFM approach for design for additive manufacturing (DFAM) to define a product. Topological optimization allows the shape improvement of the product through a material distribution for weight gain based on the desired mechanical behavior. The bi-objective optimization problem plays an important role to evaluate the manufacturability by quantification and optimization of the manufacturing criteria and constraint simultaneously. Actually, it optimizes the production time, required material regarding surface quality and mechanical properties of the product because of two significant parameters as layer thickness and part orientation.

A comprehensive analysis of the existing DFAM approaches illustrates that these approaches are not developed sufficiently in terms of manufacturability evaluation in quantification and optimization levels. There is no approach that investigates the AM criteria and constraints simultaneously. It is necessary to provide a decision-making tool for the designers and manufacturers to lead to better design and manufacturing regarding the different AM characteristics.

To assess the efficiency of this approach, a wheel spindle is considered as a case study which shows how this method is capable to find the best design and manufacturing solutions.

A multi-criteria decision-making approach as the main contribution is developed to analyze FDM technology and its attributes, criteria and drawbacks. It completes the DFAM approach for FDM through a bi-objective optimization problem which deals with finding the best manufacturing parameters by optimizing production time and material mass because of the product mechanical properties and surface roughness.

For extrusion based multi‐material layered manufacturing (LM) processes, a CAD system has been developed which generates high quality toolpath for part fabrication. This closed loop CAD system includes solid model design and slicing, single‐material toolpath generation, multi‐material toolpath generation and virtual simulation modules. The solid model is sliced equally. Intelligent features and adaptive roadwidth optimum toolpath generation algorithm computes void sizes and their location and generates void free toolpath. The virtual simulation visualizes and validates the toolpath generated for the part. When the computed toolpath quality is acceptable, it is sent to the in house hardware Fused Deposition of Multiple Ceramics (FDMC) machine for fabrication.

This paper aims to study strength properties and accuracy of a new type of composites, in which matrix is manufactured additively, whereas infill is a polyurethane resin. The process of manufacturing these composites is invented and patented by authors.

The authors developed a method of manufacturing composites, which was then used to build samples for tensile and bending tests (according to ISO 572 and ISO 178 standards), as well as measurements of accuracy.

It was found that the method of composite manufacturing designed by the authors allows obtaining both stronger and cheaper parts in comparison with the traditional acrylonitrile butadiene styrene FDM parts.

The research was limited to static tests only, and no dynamic tests were performed on the manufactured samples. The accuracy analysis is only a basic one.

Developed method allows to shorten the FDM process with simultaneous decrease of costs (in professional processes) and increase of strength of obtained products.

Application of composite materials presented in the paper will significantly expand possibilities of using FDM method to manufacture functional, strong parts able to carry higher loads. Application of different combinations of thermoplastic matrix materials with different resin infills will allow to control properties of obtained composites. The solution is currently subject of a patent.

The rapid development of three-dimensional (3D) printing makes it familiar in daily life, especially the fused deposition modeling 3D printers. The process planning of traditional flat layer printing includes slicing and path planning to obtain the boundaries and the filling paths for each layer along the vertical direction. There is a clear division line through the whole fabricated part, inherited in the flat-layer-based printed parts. This problem is brought about by the seam of the boundary in each layer. Hence, the purpose of this paper is to propose a novel helical filling path generation with the ideal surface-plane intersection for a rotary 3D printer.

The detailed algorithm and implementation steps are given with several worked examples to enable readers to understand it better. The adjacent points obtained from the planar slicing are combined to generate each layer's helical points. The contours of all layers are traversed to obtain the helical surface layer and helical path. Meanwhile, the novel rotary four-degree of freedom 3D printer is briefly introduced.

As a proof of concept, this paper presents several examples based on the rotary 3D printer designed in the authors’ previous research and the algorithms illustrated in this paper. The preliminary experiments successfully verify the feasibility and versatility of the proposed slicing method based on a rotary 3D printer.

This paper provides a novel and feasible slicing method for multi-axis rotary 3D printers, making manufacturing thin-wall and complex parts possible. To further broaden the proposed slicing method’s application in further research, adaptive tool path generation for flat and curved layer printing could be applied with a combination of flat and curved layers in the same layer, different layers or even different parts of structures.

Quantifying and controlling the quality characteristics of parts produced by additive manufacturing (AM) processes has attracted significant interest in the research community. However, to increase the sustainability of AM processes, such quality characteristics need to be assessed together with life cycle performance of AM processes such as energy and material consumption and manufacturing cost. Although a few studies have been performed for several quality characteristics, i.e. surface roughness and tensile strength, the relationship between dimensional performance and manufacturing cost is still not well known for AM processes.

In this paper, a comprehensive study of the dimensional performance and manufacturing cost of fused deposition modeling AM process is performed. Design of experiment technique is used, and the correlation of different cost components and the dimensional accuracy of parts are statistically studied.

The optimum process parameters for simultaneously optimizing the dimensional performance and manufacturing cost are identified. The analysis shows that as opposed to traditional manufacturing processes, obtaining a better dimensional performance is not necessarily associated with higher cost in the AM processes.

Almost no study and analysis for the combined dimensional performance and manufacturing cost has been performed for AM processes in the literature. It is known that within the context of traditional manufacturing processes, a natural trade-off governs the pursuit of higher dimensional performance and the manufacturing cost. However, as the AM process has a different nature compared with traditional manufacturing processes, the relationship between manufacturing cost and dimensional performance of parts has to be studied. Understanding this relationship will also help to establish a cost-optimal and sustainable tolerance allocation strategy in assemblies with AM components.

The purpose of this paper is to study the functionality of additively manufactured (AM) parts, mainly depending on their dimensional accuracy and surface finish. However, the products manufactured using AM usually suffer from defects like roughness or uneven surfaces. This paper discusses the various surface quality improvement techniques, including how to reduce surface defects, surface roughness and dimensional accuracy of AM parts.

There are many different types of popular AM methods. Unfortunately, these AM methods are susceptible to different kinds of surface defects in the product. As a result, pre- and postprocessing efforts and control of various AM process parameters are needed to improve the surface quality and reduce surface roughness.

In this paper, the various surface quality improvement methods are categorized based on the type of materials, working principles of AM and types of finishing processes. They have been divided into chemical, thermal, mechanical and hybrid-based categories.

The review has evaluated the possibility of various surface finishing methods for enhancing the surface quality of AM parts. It has also discussed the research perspective of these methods for surface finishing of AM parts at micro- to nanolevel surface roughness and better dimensional accuracy.

This paper represents a comprehensive review of surface quality improvement methods for both metals and polymer-based AM parts.