Additive manufacturing (AM) has had an enormous impact on the manufacturing sector. Its role has evolved from printing prototypes to manufacturing functional parts for a variety of applications in the automotive, aerospace, and medical industries. Recently, AM processes have also been applied in the infrastructure construction industry. Applications of AM processes could bring in significant improvements in infrastructure construction, specifically in the areas of productivity and safety. It is desirable to have a review on the current state of emerging AM processes for infrastructure construction and existing gaps in this field. This paper reviews the AM processes in infrastructure construction. It discusses the process principle, application examples, and gaps for each of the AM processes.

Circular economy has emerged as a response to increasing environmental problems. As opposed to linear economy, circular economy aims at the preservation of energy, material, and labor contents of used products. A critical process in circular economy is product recovery which involves the recovery of materials or components from returned products through various recovery options including recycling, refurbishing, and remanufacturing. All recovery options require some level of disassembly and disassembly operations that are generally carried out in a disassembly line. Like assembly lines, disassembly lines must be balanced in order to ensure the effective operation of the line. Mathematical programming techniques, metaheuristics, and various heuristic procedures were employed in order to solve different types of disassembly line balancing problem (DLBP). However, the use of multi-attribute decision making techniques is limited to few studies. In this study, we propose a DEMATEL-based disassembly line balancing approach which does not require extensive knowledge in operations research and computer programming. A solution can be obtained by carrying out basic matrix operations and following the steps of the approach. Two numerical examples are also provided in order to present the applicability of the proposed approach. The results indicate that the proposed approach presents a satisfactory performance compared to the previously proposed approaches.

This paper presents a new spiral smoothing method to generate smooth curved tool paths directly on mesh surfaces. Spiral tool paths are preferable for computer numerical control (CNC) milling, especially for high-speed machining. At present, most spiral tool path generation methods aim mainly for pocketing, and a few methods for machining complex surface also suffer from some inherent problems, such as selection of projecting direction, preprocessing of complex offset contours, easily affected by the mesh or mesh deformation. To address the limitations, a new spiral tool path method is proposed, in which the radial curves play a key role as the guiding curves for spiral tool path generation. The radial curve is defined as one on the mesh surface that connects smoothly one point on the mesh surface and its boundary. To reduce the complexity of constructing the radial curves directly on the mesh surface, the mesh surface is first mapped onto a circular region. In this region, the radial lines, starting from the center, are planned and then mapped inversely onto the mesh surface, thereby forming the desired radial curves. By traversing these radial curves using the proposed linear interpolation method, a polyline spiral is generated, and then, the unfavorable overcuts and undercuts are identified and eliminated by supplementing additional spiral points. Spline-based technique of rounding the corners is also discussed to smooth the polyline spiral, thereby obtaining a smooth continuous spiral tool path. This method is able to not only greatly simplify the construction of radial curves and spiral tool path but also to have the ability of processing and smoothing complex surfaces. Experimental results are presented to validate the proposed method.

In recent years, the usage of additive manufacturing (AM) provides new capabilities for component repair, which includes low heat input, small heat-affected zone, and freeform near-net-shape fabrication. Because the geometry of each worn component is unique, the automated repair process is a challenging and important task. The focus of this paper is to investigate and develop a general best-fit and shape-adaption algorithm for automating alignment and defect reconstruction for component repair. The basic principle of using features for rigid-body best-fitting is analyzed and a multifeature-fitting method is proposed to best fit the 3D mesh model of a worn component and its nominal component. The multifeature-fitting algorithm in this paper couples the least-squares method and a density-based outlier detection method. These two methods run alternately to approach the best-fit result gradually and eliminate the disturbance caused from the defect geometry. The shape-adaption algorithm is used to do cross section comparison and defect reconstruction based on the best-fitted 3D model. A “point-line-surface” fracture surface detection method is proposed to construct fracture surface and the fracture surface boundary is dilated to trim the nominal 3D model to obtain defect geometry. Illustrative examples with typical components and different kinds of defects are used to demonstrate the flexibility and capability of using multifeature-fitting and shape-adaption algorithm developed in this paper.

A PED (precision extrusion deposition)/replica molding process enables scaffold guided tissue engineering of a heterocellular microfluidic device. We investigate two types of cell-laden devices: the first with a 3D microfluidic manifold fully embedded in a PDMS (polydimethylsiloxane) substrate and the second a channel network on the surface of the PDMS substrate for cell printing directly into device channels. Fully embedded networks are leak-resistant with simplified construction methods. Channels exposed to the surface are used as mold to hold bioprinted cell-laden matrix for controlled cell placement throughout the network from inlet to outlet. The result is a 3D cell-laden microfluidic device with improved leak-resistance (up to 2.0 mL/min), pervasive diffusion and control of internal architecture.

Multi-axis slicing for solid freeform fabrication manufacturing processes can yield nonuniform thickness layers or three-dimensional (3D) layers. The traditional parallel layer construction approach to building such layers leads to the so-called staircase effect, which requires machining or other postprocessing to form the desired shape. This paper presents a direct 3D layer deposition approach that uses an empirical model to predict the layer thickness. The toolpath between layers is not parallel; instead, it follows the final shape of the designed geometry and the distance between the toolpath in the adjacent layers varies at different locations. Directly depositing 3D layers not only eliminates the staircase effect but also improves manufacturing efficiency by shortening the deposition and machining times. Simulation and experimental studies are conducted that demonstrate these advantages. Thus, the 3D deposition method is a beneficial addition to the traditional parallel deposition method.

The need for predicting material microstructure and hardness in hard turned surfaces becomes very urgent in that hard turning is adopted by industries as a finishing process, and the produced surface integrity, including microstructure and hardness, is well known to be a determining factor for part service performance. This study focuses on the prediction of material softening and is composed of two parts, namely, the construction of material softening model based on thermal history and the prediction of thermal history by finite element modeling of hard turning. In this part of the research, three material softening models based on thermal activation concept are proposed and compared. The most suitable model is selected for the work material, hardened AISI 52100 steel. The model prediction demonstrates excellent agreement with the hardness measurement on the specimens with isothermal or anisothermal treatments. For the isothermal treatments, the average prediction error, compared with the measured hardness, is 10.78 kg ∕ mm 2 . As for the anisothermal treatments, the average error is 13.79 kg ∕ mm 2 . The softening model provides a fundamental for the final prediction of material softening in hard turned surfaces.

Sheet metal forming dies constructed of laminations offer advantages over more conventional tooling fabrication methods (e.g. CNC-machining) in terms of tooling accessibility, reduced limitations on die geometry and faster fabrication with harder die materials. Furthermore, the recently introduced Profiled Edge Lamination (PEL) tooling method improves upon other lamination-based tooling methods. Adoption of this promising rapid tooling method by industry is being hindered by the lack of formal analysis, design principles, and manufacturing requirements needed to construct dies in such a manner. Therefore, the propensity for delamination of the die is discussed and preventive measures are suggested. The basic machining instructions, i.e., an array of points and directional vectors for each lamination, are outlined for both compound and planar profiled-edge bevels. Laser, AWJ and flute-edge endmilling are experimentally identified as the most promising methods for machining bevels. Development of a stand-alone PEL fabrication machine is suggested over retrofitting commercially-available 5-axis machines. Finally, the general procedure for creating PEL dies is implemented in the construction of a matched set of sheet metal forming tools. These tools are used to successfully stamp a sheet metal part out of draw-quality steel.

Energy is important for modern civilization and the electrical power from thermal stations is a major source of energy on which hinges the functioning and growth of mankind. In almost all major countries of the world thermal power stations are getting bigger and are generating huge quantities of flyash as a waste from their mammoth boilers. Despite extensive research on flyash, its utilization level is still low although it is considered as a novel and useful material in various fields such as building and road construction, agriculture, refractory works, water treatment, foundry, etc. In the present work flyash has been used as an additive to the silica sand in the V-process molds and its effects on the surface finish and total solidification time of the Al-11%Si alloy castings have been studied. Results indicate that the surface finish of the castings improves by the addition of flyash. Total solidification time of the castings reduces when the flyash has been added beyond 25 percent.

In Part 1 of this two-part paper, we review the development of open architecture controllers for machine tools. General design principles are described, followed by specific hardware and, software recommendations. These specific recommendations are then used for the construction of an open architecture device, MOSAIC-PM, (Machine tool Open System Advanced Intelligent Controller for Precision Machining). The machine has now been used in a wide variety of experiments to demonstrate open architecture control. These experiments include sensor based machining, rapid prototyping and manufacturing over the Internet. In Part 1, a specific application on feature based precision machining with on-machine acceptance is described. A more specific implementation of a quintic spline interpolation method is described in Part 2.

A formal approach for integrating Computer-Aided Design (CAD), Computer-Aided Process Planning (CAPP), and shop floor control for rotational components is presented in this paper. It is assumed that this approach will be implemented within the framework of a three level hierarchical CIM architecture that consists of the following levels in the hierarchy: shop floor, workstation and equipment (Joshi et al., 1991). Our approach to CAPP consists of machining feature identification, definition, classification, representation, and reasoning, provided through a CAD model of a product. Geometric entities are identified from a Drawing Exchange Format (DXF) file. The identified entities form the basis for the construction of primitive manufacturing features. The primitive features are assembled together based upon the precedence among features, into a graph, called a feature graph. However, the primitive features may or may not be manufacturable in terms of depth of cut, tool geometry, surface finish, and material handling required. Hence it is necessary to convert the feature graph into a manufacturing task graph, which consists of specifications of alternative functional tasks that are manufacturable. The task graph may be converted into a hierarchical set of process plans, based on the planning criteria at each level in the control hierachy, to reflect the processing requirements at each level. The shop planning function decomposes the task graph into a set of workstation level plans. Each workstation level plan is aggregated into a set of equipment level process plans by the workstation planning function. The equipment level plan is converted into a unique task sequence by the equipment planning function. This sequence is then executed according to specifications by the equipment level execution function. Provision of alternative routes in process plans provides for flexible means of on-line planning and control.

With increasing emphasis on the adaptive control for the purpose of quality and productivity improvement, it becomes necessary to develop models which can correlate the surface finish parameters with the machining conditions as well as work-piece material characteristics. This paper presents a study that leads to the development of a model for the dynamic generation of three-dimensional texture of machined surfaces. In Part 1, the mathematical formulation of the random excitation system which is responsible for the random portion of a surface profile is developed. It is assumed that the random excitation system originates from the nonhomogeneous distribution of microhardness of workpiece material. Machining tests are also performed to verify the validity of such a model development. In Part 2, a procedure for the construction of three-dimensional topography will be developed and the relationship between the machining conditions and the surface finish parameters will be established.

In Part 1 of these two-part papers, a normal distribution model has been formulated to describe the random excitation system present during machining. Part 2 presents a methodology to dynamically generate the surface topography under the random excitation environment through computer simulation. The proposed methodology uses the tool vibratory motion along with the tool geometrical motion to construct the topography of a machined surface. Both experimental and simulation results confirm that when a small feed is used, the influence of the spiral trajectory of tool geometrical motion on the surface generation decays dramatically and the random excitation system, on the opposite, is strengthened playing a significant role in surface texture generation.

In this research, a statically-balanced direct-drive manipulator is designed and constructed to achieve improved dynamic behavior for compliance control [10, 11, 12]. The manipulator mechanism, incorporating a four-bar linkage, is designed so that its functional parts are balanced in all positions without the addition of counterweights. The motors are never loaded by gravity. As a result, smaller motors with less torque can be used to achieve higher speed, accuracy, and repeatability in fine manipulation tasks. The robot is powered by high-torque AC synchronous motors. The mechanism is comprised of graphite-epoxy and AA7075T6 aluminum materials. The manipulator is controlled by a parallel processor computer.

Following Part 1 of this work, which discussed the theory behind the design of an Enhanced Quality Evaluation System (EQES), Part 2 addresses the construction of the rule base which classifies how the transfer function of the process has changed and also details the least squares algorithms used to estimate the magnitude and time of occurrence of the change. An example showing how EQES could be used to improve the quality of a turning process is given. Also shown are results of a physical experiment which used EQES to monitor changes in force signals from an end milling process.

This paper addresses the specific problems encountered when building an expert system for use in a manufacturing process. These problems include: general unfamiliarity of the experts with expert systems, the diffused nature of the expertise, the low availability of the experts, and the users fear of being replaced or constrained by the computer system. The paper addresses these problems by presenting specific strategies developed in the construction of an expert system for use in controlling a plating process for electronic components.

The present planning for the construction of a manned space station calls for modular construction in space over a period of several years with each module having different dynamic characteristics and attitude control requirements. Several of the modules will be best modeled as distributed (flexible) bodies. It is necessary that the attitude control system be capable of providing appropriate attitude control to a suitable accuracy for the individual modules at all times during the construction. This plus the extreme flexibility pose far more difficult problems to the attitude control designer than in previous spacecraft. In spite of this, the author believes that the design techniques for past spacecraft will be used as the starting point for the attitude control system of the space station. The new theories for flexible control systems will probably be used in computer simulations for preflight validation of the control system design. Substantial improvements in the attitude control will more than likely come from new mechanical designs for actuators, intersections between modules, and passive dampers.

Logic foundations expounded in Part 1 are applied to development of a mathematical model describing profile generation in face milling. A pattern recognition procedure is developed, capable of locking onto proper reference points on the profile in terms of tool mark characteristics and identifying model parameters. Construction of the reference locating algorithm is examined in detail, and some aspects of application covering also profile reconstruction are discussed in the light of test results.

The construction of an improved model of TMA for fibers is briefly described. Two special features are: use of an electronic balance for measuring force and use of a precision screw driven by a servo-step motor for measuring length. Besides the usual thermomechanical measurements, the use of the instrument as a research tool for a number of purposes like fiber texture, orientation, heat treatment, and so on has been amply illustrated.

A powerful new tool for the analysis and design of underwater breathing gas systems is being developed. A versatile computer simulator is described which makes possible the modular “construction” of any conceivable breathing gas system from computer memory-resident components. The analysis of a typical breathing gas system is demonstrated using this simulation technique, and the effects of system modifications on performance of the breathing system are shown. This modeling technique will ultimately serve as the foundation for a proposed breathing system simulator under development by the Navy. The marriage of this computer modeling technique with an interactive graphics system will provide the designer with an efficient, cost-effective tool for the development of new and improved diving systems.