Overlapping optimization of hybrid deposited and micro-rolling additive manufacturing

Purpose This paper aims to summarize the influence law of hybrid deposited and micro-rolling (HDMR) technology on the bead morphology and overlapping coefficient. A better bead topology positively supports the overlapping deposited in multi-beads between layers while actively assisting the subsequent layer's deposition in the wire and arc additive manufacturing (WAAM). Hybrid-deposited and micro-rolling (HDMR) additive manufacturing (AM) technology can smooth the weld bead for improved surface quality. However, the micro-rolling process will change the weld bead profile fitting curve to affect the overlapping coefficient. Design/methodology/approach Weld bead contours for WAAM and HDMR were extracted using line lasers. A comparison of bead profile curves was conducted to determine the influence law of micro-zone rolling on the welding bead contour and fitting curve. Aiming at the optimized overlapping coefficient of weld bead in HDMR AM, the optimal HDMR overlapping coefficient curve was proposed which varies with the reduction based on the best surface flatness. The mathematical model for overlapping in HDMR was checked by comparing the HDMR weld bead contours under different rolling reductions. Findings A fitting function of the bead forming by HDMR AM was proposed based on the law of conservation of mass. The change rule of the HDMR weld bead overlapping spacing with the degree of weld bead rolling reduction was generated using the flat-top transition calculation for this model. Considering the damming-up impact of the first bead, the overlapping coefficient was examined for its effect on layer surface flatness. Originality/value Using the predicted overlapping model, the optimal overlapping coefficients for different rolling reductions can be achieved without experiments. These conclusions can encourage the development of HDMR technology.

Effect of layer thickness on the overhanging surface quality manufactured by selective laser melting

With the increasing demand for the precision of lightweight part, overhanging surface quality has attracted more and more attentions in recent years. In this work, the relationship between overhanging surface quality and layer thickness was studied. The testing results revealed that with the increasing of the layer thickness, surface quality, especially the surface flatness, showed a significant decreasing trend due to the decreasing of the bending deformation. When layer thickness was ranged from 0.15 to 0.18, it reached a relative optimal condition while the sinking distance and flatness within 0.095 mm–0.1 mm and 0.076 mm–0.078 mm, respectively. With the further increasing of the layer thickness, both sinking distance and surface flatness had a quite significant decreasing due to the increasing gravity of the overhanging layer powder and bonded powder caused by the molten pool sinking. Combined to the experimental data and the analysis given above, the structure of the overhanging surface was optimized and the surface quality showed a further increase.

Research on Micro/Nano Surface Flatness Evaluation Method Based on Improved Particle Swarm Optimization Algorithm

Flatness error is an important factor for effective evaluation of surface quality. The existing flatness error evaluation methods mainly evaluate the flatness error of a small number of data points on the micro scale surface measured by CMM, which cannot complete the flatness error evaluation of three-dimensional point cloud data on the micro/nano surface. To meet the needs of nano scale micro/nano surface flatness error evaluation, a minimum zone method on the basis of improved particle swarm optimization (PSO) algorithm is proposed. This method combines the principle of minimum zone method and hierarchical clustering method, improves the standard PSO algorithm, and can evaluate the flatness error of nano scale micro/nano surface image data point cloud scanned by atomic force microscope. The influence of the area size of micro/nano surface topography data on the flatness error evaluation results is analyzed. The flatness evaluation results and measurement uncertainty of minimum region method, standard least squares method, and standard PSO algorithm on the basis of the improved PSO algorithm are compared. Experiments show that the algorithm can stably evaluate the flatness error of micro/nano surface topography point cloud data, and the evaluation result of flatness error is more reliable and accurate than standard least squares method and standard PSO algorithm.

Surface Flattening of Directed Energy Deposited Parts through Jet Electrochemical Machining

For additive manufacturing (AM) processes, post-processing is usually needed before application, and electrochemical machining is considered a promising candidate for this purpose. Here, the possibility of using jet electrochemical machining (Jet-ECM) as a semi-finishing post-processing for directed energy deposition (DED) was investigated. The main purpose is to flatten the wave-like surface and improve dimensional accuracy. First, polarization, EIS, and current efficiency measurements were conducted, and it was found that the electrochemical dissolution behaviors of the DED-produced Inconel 718 alloy in NaNO3 solution were isotropic and irrelevant to the DED parameters, which can be attributed to the effect of the passive film. Pa and Pz values from the primary profile were considered more suitable than surface roughness for the characterization of the surface flatness. In the Jet-ECM experiments, the small inter-electrode gaps and high applied voltages were found to be beneficial to surface flattening, while the influence of the scanning speed was not evident. Multiple reciprocating scans could further improve the surface flatness, but most of the improvements were obtained in the first scan. This demonstrates the great potential of Jet-ECM in the post-processing of AM parts, and provide several essential guidelines for further research.

Fuel Consumption of Wheeled Vehicle and Transportation Costs during Highway Construction/Reconstruction

A method is proposed for determining the fuel consumption of a wheeled vehicle depending on its speed, road surface flatness and road slope in the longitudinal direction. The purpose of the research is to derive mathematical relationships for calculating the fuel consumption of vehicles, which is one of the transport cost factors during the construction/reconstruction or overhaul of a highway. The proposed polynomial dependencies for calculating fuel in addition to vehicle speed, road surface flatness and its longitudinal slope take into account the mass-dimensional parameters of vehicles involved in road traffic. New mathematical relationships between the speed of wheeled vehicles, road surface flatness and longitudinal road slope allow to simulate the change in the value of fuel consumption of a wheeled vehicle when the speed of traffic flow or the slope of the road surface changes in the forward or reverse direction of the vehicle. In a graphic way, the influence of the pavement slope on the value of fuel consumption, both loaded and unloaded wheeled vehicle is presented. When determining transport costs associated with the highway construction, reconstruction or overhaul it is proposed to use empirical mathematical relationships, which make it possible to obtain fuel consumption with an accuracy of 5 % and save up to 15 % of budget (private) investments. The analysis of scientific publications of the existing approach determine the transport costs associated with highway construction, reconstruction or overhaul. The presented method for determining the fuel consumption of wheeled vehicles with small and large loading capacity increases the accuracy of determining transportation costs and reduces the level of financial costs for highway construction, reconstruction or overhaul.

Microstructure adjustment of an asymmetric ceramic membrane with high permeation performance

An asymmetric alumina ceramic membrane was prepared by secondary dip coating. The influence of different dispersants and dip coating parameters on the microstructure of the membrane separation layer was explored. Meanwhile, the pure water fluxes of the membranes with various microstructures were also studied. The results show that a separation layer with a defect-free thickness of 16.5 μm and high surface flatness can be obtained when using polycarboxylate as a dispersant and twice dip coating within 2 s + 1 s and the pure water flux of an asymmetric membrane up to 1153 L × m-2 × h-1 × bar-1. The present work provides a simple and effective method for controlling the morphology and permeation performance of an asymmetric alumina membrane.

Selecting Optimal Conditions for Flat Grinding Linear Bearings Guides of Low Rigidity

The article discusses the proposed algorithm and method for determining the optimal grinding conditions for linear bearing guides of low rigidity, which ensure meeting the specified requirements for the quality of the processed surface (surface roughness parameter Ra, no grinding burns and surface flatness tolerance) at maximum process productivity. Input factors (grinding wheel hardness, radial feed, table feed speed) are parameters for optimizing the grinding process. Mathematical models of the output factors are designed to limit the range of acceptable values of the optimization parameters. Processing performance was chosen as the target function. Optimization of parameters within the range of permissible values is carried out on the basis of ensuring the maximum productivity of the process. The required flatness tolerance is provided at the second stage of mode optimization by limiting the value of the maximum elastic deformation. The cutting forces, the magnetic field attraction of the machine table and the bending stiffness of the workpiece are the variable parameters. Mathematical models for determination of maximum elastic deformation of prismatic workpieces when fixing and machining are presented. The conditions for ensuring a given workpiece surface flatness tolerance are determined, taking into account the elastic deformation of a prismatic workpiece of low rigidity under the effects of the magnetic field of the machine tool and the radial component of the grinding force.

Landing Site Detection for UAVs Based on CNNs Classification and Optical Flow from Monocular Camera Images

The increased use of UAVs (Unmanned Aerial Vehicles) has heightened demands for an automated landing system intended for a variety of tasks and emergency landings. A key challenge of this system is finding a safe landing site in an unknown environment using on-board sensors. This paper proposes a method to generate a heat map for safety evaluation using images from a single on-board camera. The proposed method consists of the classification of ground surface by CNNs (Convolutional Neural Networks) and the estimation of surface flatness from optical flow. We present the results of applying this method to a video obtained from an on-board camera and discuss ways of improving the method.

Laser Scanning Based Surface Flatness Measurement Using Flat Mirrors for Enhancing Scan Coverage Range

Surface flatness is an important indicator for the quality assessment of concrete surfaces during and after slab construction in the construction industry. Thanks to its speed and accuracy, terrestrial laser scanning (TLS) has been popularly used for surface flatness inspection of concrete slabs. However, the current TLS based approach for surface flatness inspection has two primary limitations associated with scan range and occluded area. First, the areas far away from the TLS normally suffer from inaccurate measurement caused by low scan density and high incident angle of laser beams. Second, physical barriers such as interior walls cause occluded areas where the TLS is not able to scan for surface flatness inspection. To address these limitations, this study presents a new method that employs flat mirrors to increase the measurement range with acceptable measurement accuracy and make possible the scanning of occluded areas even when the TLS is out of sight. To validate the proposed method, experiments on two laboratory-scale specimens are conducted, and the results show that the proposed approach can enlarge the scan range from 5 m to 10 m. In addition, the proposed method is able to address the occlusion problem of the previous methods by changing the laser beam direction. Based on these results, it is expected that the proposed technique has the potential for accurate and efficient surface flatness inspection in the construction industry.