Jialuo Ding

Wire + Arc Additive Manufacturing

Depositing large components (>10 kg) in titanium, aluminium, steel and other metals is possible using Wire + Arc Additive Manufacturing. This technology adopts arc welding tools and wire as feedstock for additive manufacturing purposes. High deposition rates, low material and equipment costs, and good structural integrity make Wire+Arc Additive Manufacturing a suitable candidate for replacing the current method of manufacturing from solid billets or large forgings, especially with regards to low and medium complexity parts. A variety of components have been successfully manufactured with this process, including Ti–6Al–4V spars and landing gear assemblies, aluminium wing ribs, steel wind tunnel models and cones. Strategies on how to manage residual stress, improve mechanical properties and eliminate defects such as porosity are suggested. Finally, the benefits of non-destructive testing, online monitoring and in situ machining are discussed.

Design for Wire and Arc Additive Layer Manufacture

Additive Layer Manufacture (ALM) is a technique whereby freeform structures are produced by building up material in layers. RUAM (Ready-to-Use Additive Layer Manufacturing) is an innovative concept for building large scale metal ready-to-use parts. The design for RUAM has several process steps: the geometric design of the parts taking the complex process behaviour of the arc welding process into account; FEM to predict temperature and stress distributions to minimise part distortions; and efficient robot tool path design. This paper covers these essential design steps from a technical as well as practical point of view.

Design study for wire and arc additive manufacture

Additive Manufacture (AM) is a technique whereby freeform structures are produced by building up material in a layer by layer fashion. Among the different AM processes, Wire and Arc Additive Manufacture (WAAM) has the ability to manufacture large custom-made metal workpiece with high efficiency. A design study has been performed to explore the process capabilities of fabricating complicated geometries using WAAM. Features such as enclosed structures, crossing structures, and balanced building structures have been investigated in this study. Finite Element (FE) models are employed to take the thermo-mechanical performance into account. Robot tool path design has been performed to transfer the WAAM component designs into real components efficiently. This paper covers these essential design steps from a technical as well as practical point of view.

Influence of Cold Metal Transfer Process and Its Heat Input on Weld Bead Geometry and Porosity of Aluminum-Copper Alloy Welds

Abstract The weld bead geometry and the porosity of AA2219-T851 high strength aluminum alloy welds with ER2319 wire produced by different cold metal transfer (CMT) processes and heat inputs were investigated. The results show that a narrow finger-shaped geometry is observed using the conventional CMT process and a large number of gas pores exist in the lower and upper parts of welds. Compared to results of above mentioned CMT process, the weld melting area is increased using CMT-pulse (CMT-P) process, and it is beneficial to reduce the porosity effectively with an appropriate heat input. The finger-shaped geometry with lower melting depth using CMT-advanced (CMT-ADV) process and the spherical-shaped bead geometry with lower dilution using CMT-pulse advanced (CMT-PADV) process are achieved. The gas pore is reduced predominantly and even eliminated due to the lower heat input and the effective oxide cleanliness of wire ends for the two processes.

A Passive Imaging System for Geometry Measurement for the Plasma Arc Welding Process

Automatic and flexible geometry measurement of the weld pool surface can help better understand the complex welding processes and even provide feedback to better control this process. Most of existing imaging systems use an additional source of illumination to remove the light interference coming from the welding arc but it is usually costly. This paper introduces a novel low-cost optical-sensor-based monitoring system working under passive mode to monitor the wire + arc additive manufacture process, particularly for plasma arc welding. Initially, configurations and parameters of camera are investigated to achieve good visualization of weld pool. A novel camera calibration methodology using the nozzle of a computer numerical control (CNC) machine is then proposed for this imaging system, allowing estimation of the camera position with respect to the inspecting surface and its orientation in an easy-to-use approach. The verification tests show that the average error of the calibration is less than 1 pixel. As a case study, an image analysis routine is proposed to measure the width of the bead during the welding process. The results show that the proposed system is effective to measure the dimension of weld pool.

Preliminary Investigation of Building Strategies of Maraging Steel Bulk Material Using Wire + Arc Additive Manufacture

Wire + arc additive manufacture (WAAM) is a new process for fabricating large-scale metallic components. In this paper, the use of cold metal transfer-based WAAM process for the production of maraging steel bulk material is reported. Process parameters were studied, and the effect of building strategies including oscillation, parallel and weaving on bead shape was investigated. The structural integrity of the WAAM bulk material regarding the surface finish, lack-of-fusion issue and microstructure was characterized. Results proved the feasibility of applying WAAM to producing maraging steel bulk material, and weaving was identified to be most recommended building strategy.

Preliminary Investigation into the Suitability of 2xxx Alloys for Wire-Arc Additive Manufacturing

An investigation has been performed into the compatibility of aluminum alloys used in the aerospace industry with Wire-Arc Additive Manufacturing. Modelling and preliminary experimental trials have been performed to show that it is viable to use Al-Cu-Mg alloys, like 2024, without solidification cracking. A relatively fine and texture free grain structure was obtained in the as-deposited WAAM material and the addition of inter-pass deformation, by rolling each added layer, led to further grain size refinement. With adequate control of porosity and subsequent heat treatment, the WAAM material was found to have tensile properties comparable to that of standard wrought products.

Laser speckle velocimetry for robot manufacturing

A non-contact speckle correlation sensor for the measurement of robotic tool speed is presented for use in robotic manufacturing and is capable of measuring the in-plane relative velocities between a robot end-effector and the workpiece or other surface. The sensor performance was assessed in the laboratory with the sensor accuracies found to be better than 0:01 mm/s over a 70 mm/s velocity range. Finally an example of the sensors application to robotic manufacturing is presented where the sensor was applied to tool speed measurement for path planning in the wire and arc additive manufacturing process using a KUKA KR150 L110/2 industrial robot.

Design for Wire + Arc Additive Manufacture: design rules and build orientation selection

ABSTRACT Wire + Arc Additive Manufacture (WAAM) is an additive manufacturing technology that can produce near net-shape parts layer by layer in an automated manner using welding technology controlled by a robot or CNC machine. WAAM has been shown to produce parts with good structural integrity in a range of materials including titanium, steel and aluminium and has the potential to produce high value structural parts at lower cost with much less waste material and shorter lead times that conventional manufacturing processes. This paper provides an initial set of design rules for WAAM and presents a methodology for build orientation selection for WAAM parts. The paper begins with a comparison between the design requirements and capabilities of WAAM and other additive manufacturing technologies, design guidelines for WAAM are then presented based on experimental work. A methodology to select the most appropriate build orientation for WAAM parts is then presented using a multi attribute decision matrix approach to compare different design alternatives. Two aerospace case study parts are provided to illustrate the methodology.