Zhang Hai-ou, Rui Wang, Liye Liang and Wang Gui-lan
The paper aims to introduce the fabrication of a medium steel aircraft part by hybrid deposition and micro-rolling technology (HDMR) and illustrate its advantages, microstructure…
Abstract
Purpose
The paper aims to introduce the fabrication of a medium steel aircraft part by hybrid deposition and micro-rolling technology (HDMR) and illustrate its advantages, microstructure features and mechanical properties of the part.
Design/methodology/approach
The HDMR technology contains two procedures happening almost at the same time: the welding deposition procedure and then the micro-rolling procedure. It takes the gas metal arc welding as the heat source to melt a metal wire and deposit metal in the welding deposition procedure. The metal just deposited is rolled synchronously by a micro roller following the welding torch in micro-rolling procedure almost at the same time layer by layer. The paper presents a contrast of the grain morphology of metal parts produced respectively by HDMR and freedom arc deposition (FAD) and the mechanical properties of metal parts of the same metal from HDMR casting, forging and FAD methods.
Findings
HDMR breaks the dendrite grain of welding beads into the fine crisscross grains. The mechanical properties of metal parts are improved distinctly by the micro-rolling procedure compared to casting, forging and FAD.
Practical implications
In addition, the application of HDMR technology has succeeded in the fabrication of an eligible aircraft metal part, which is quite difficult to achieve using other additive manufacturing (AM) or casting technologies.
Originality/value
HDMR has the advantage of equiponderance manufacturing by micro-rolling compared to other AM technologies. The metal part fabricated by HDMR technology obtains the fine crisscross grains and brings hope for AM metal components with excellent mechanical properties for aircraft applications.
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Rui Wang, Haiou Zhang, Wang Gui-Lan and Xushan Zhao
The wire and arc additive manufacturing (WAAM) is a promising technology, but the parts are mostly manufactured on the plane and along the vertical direction. The purpose of this…
Abstract
Purpose
The wire and arc additive manufacturing (WAAM) is a promising technology, but the parts are mostly manufactured on the plane and along the vertical direction. The purpose of this paper is to propose a cylindrical slicing and manufacturing method.
Design/methodology/approach
For revolved parts, e.g. blades of a propeller, instead of planes, a series of cylindrical surfaces intersect with the STL model of the part. The generated slicing layers lie on the cylindrical surface, and then these spatial contours are unfolded onto the plane by the use of the cylindrical coordinate system. A deposition system based on an NC machine is established to examine deposition paths. The temperature and stress of part of two deposition orders are analyzed using the finite element method.
Findings
The scan parallel path and contour offset path are not suitable to fabricate blades directly. The hybrid of two types of paths and the hybrid of skeleton and contour offset paths are capable of forming blades without gaps. Deposition symmetrically can decrease the deformation of the propeller.
Originality/value
The slicing algorithm is simply implemented and practicable for any parts. The recognition of gaps and supplementary skeleton path can guarantee the full deposition of contour offset paths.
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Liaoyuan Chen, Tianbiao Yu, Ying Chen and Wanshan Wang
The purpose of this paper is to improve the dimensional accuracy of inclined thin-walled parts fabricated by laser direct metal deposition (DMD) under an open-loop control system.
Abstract
Purpose
The purpose of this paper is to improve the dimensional accuracy of inclined thin-walled parts fabricated by laser direct metal deposition (DMD) under an open-loop control system.
Design/methodology/approach
In this study, a novel method of the adaptive slicing method and DMD process with feedback adjustment of deposition height has been developed to successively fabricate complex inclined thin-walled square tube elbow parts. The defocus amount was used as a variable to the matching between the deposition thickness and the adaptive slicing height.
Findings
The low relative error of dimensional accuracy between experimental and designed parts shows that the matching of the single-layer deposition thickness and the adaptive slicing height can be realized by optimizing the defocusing amount. The negative feedback of the thin-wall part height can be achieved when the defocus amount and the z-axis increment are less than deposition thickness. The improvement of dimensional accuracy of inclined thin-walled parts is also attributed to the optimized scanning strategy.
Practical implications
The slicing method and deposition process can provide technical guidance for other additive manufacturing (AM) systems to fabricate metal thin-walled parts with high dimensional accuracy because the feedback control of deposition height can be realized only by the optimized process.
Originality/value
This study provides a novel adaptive slice method and corresponding the deposition process, and expands the slicing method of AM metal parts.
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Tianqi Wang, Xu Zhou and Hongyu Zhang
The purpose of this paper is to study the wire and arc additive manufacturing (WAAM) method and path planning algorithm of truss structure parts, to realize the collision-free…
Abstract
Purpose
The purpose of this paper is to study the wire and arc additive manufacturing (WAAM) method and path planning algorithm of truss structure parts, to realize the collision-free rapid prototyping of truss structures with complex characteristics.
Design/methodology/approach
First, a point-by-point stacking strategy is proposed based on the spot-welding mode of cold metal transfer welding technology. A force analysis model of the droplet is established, which can be used to adjust the posture of the welding torch and solve the collapse problem in the WAAM process of the truss structure. The collision detection model is developed to calculate the interference size between the truss structure and the welding torch, which is used to control the offset of the welding torch. Finally, the ant colony algorithm has been used to optimize the moving path of welding torch between truss with considering the algorithm efficiency and collision avoiding and the efficiency of the algorithm is improved by discretizing the three-dimensional workspace.
Findings
A series of experiments were conducted to prove the validity of the proposed methods. The results show that the wire feeding speed, welding speed are the important parameters for controlling the WAAM process of truss parts. The inclination angle of the welding torch has an important influence on the forming quality of the truss.
Originality/value
The force analysis model of truss structure in the WAAM process is established to ensure the forming quality and a collision-free path planning algorithm is proposed to improve forming efficiency.
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Fusheng Dai, Shuaifeng Zhang, Runsheng Li and Haiou Zhang
This paper aims to present a series of approaches for three-related issues in multiaxis in wire and arc additive manufacturing (WAAM) as follows: how to achieve a stable and…
Abstract
Purpose
This paper aims to present a series of approaches for three-related issues in multiaxis in wire and arc additive manufacturing (WAAM) as follows: how to achieve a stable and robust deposition process and maintain uniform growth of the part; how to maintain consistent formation of a melt pool on the surface of the workpiece; and how to fabricate an overhanging structure without supports.
Design/methodology/approach
The principal component analysis-based path planning approach is proposed to compute the best scanning directions of slicing contours for the generation of filling paths, including zigzag paths and parallel skeleton paths. These printing paths have been experimented with in WAAM. To maintain consistent formation of a melt pool at overhanging regions, the authors introduce definitions for the overhanging point, overhanging distance and overhanging vector, with which the authors can compute and optimize the multiaxis motion. A novel fabricating strategy of depositing the overhanging segments as a support for the deposition of filling paths is presented.
Findings
The second principal component of a planar contour is a reasonable scanning direction to generate zigzag filling paths and parallel skeleton filling paths. The overhanging regions of a printing layer can be supported by pre-deposition of overhanging segments. Large overhangs can be successfully fabricated by the multiaxis WAAM process without supporting structures.
Originality/value
An intelligent approach of generating zigzag printing paths and parallel skeleton printing paths. Optimizations of depositing zigzag paths and parallel skeleton paths. Applications of overhanging point overhanging distance and overhanging vector for multiaxis motion planning. A novel fabricating strategy of depositing the overhanging segments as a support for the deposition of filling paths.
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Mingkang Zhang, Yongqiang Yang, Changhui Song, Yuchao Bai and Zefeng Xiao
This study aims to focus on the heat treatment influence on the corrosion resistance, adhesion of Streptococcus mutans and mechanical properties of CoCrMo alloys manufactured by…
Abstract
Purpose
This study aims to focus on the heat treatment influence on the corrosion resistance, adhesion of Streptococcus mutans and mechanical properties of CoCrMo alloys manufactured by the selective laser melting (SLM).
Design/methodology/approach
CoCrMo alloys were manufactured using the Dimetal-100 machine. X-ray diffraction (XRD), metallographic analysis, scanning electron microscopy (SEM), electrochemical corrosion, Vickers microhardness and tensile tests were used to characterize SLM-produced CoCrMo alloys and compare them with the ones manufactured by casting and with the ASTM F75 standard.
Findings
The electrochemical results showed that SLM900 samples had the best corrosion resistance in artificial saliva. The adhesion results showed least propagation and overall quantity of Streptococcus mutans on the SLM900 sample. The microhardness, tensile and yield strength of As-SLM, SLM900 and SLM1200D samples were measured according to the ASTM F75 standard. The elongation of SLM900 was less than 8 per cent, which does not meet the standard specifications. Analysis of the fracture morphology showed that the fracture mechanisms of As-SLM and SLM1200D belong to the quasi-cleavage fracture type, and the mechanical fracture mechanism of SLM900 can be characterized as brittle fracture.
Originality/value
This paper presents the adhesion properties of Streptococcus mutans on the surface of CoCrMo alloys manufactured by SLM and proposes how to regulate the effect of the heat treatment on the corrosion resistance and mechanical properties of CoCrMo alloys manufactured by SLM.