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research-article  
Anna Neshta, Dmytro Kryvoruchko, Michal Hatala, Vitalii Ivanov, Frantisek Botko, Svetlana Radchenko and Dusan Mital
J. Manuf. Sci. Eng   doi: 10.1115/1.4039062
The analysis of various methods of machining of rope internal thread IS? 10208, DIN 20317 has been carried out and the criteria of high-efficiency machining have been formulated. The concept of the method has been developed, which supposes the designing of the construction of non-core tool and the calculation of the parameters of mechanical trajectory with the purpose of ensuring the machining per one pass on the CNC milling machine. The compensation procedure of dimensional wear of insert has been developed. While the machining of the production batch of the parts in an experimental way, the optimum cutting conditions has been determined which allow ensuring the maximum efficiency on reaching the required roughness and the dimensional accuracy of the profile of rope thread. The performed statistical analysis of the machined parts allowed to establish that dispersions of the actual values of profiles' roughness follow Gauss' Law. In an experimental way has been proved that the application of the proposed method increased the efficiency of machining of the internal rope thread by 2,5 times. On the basis of comparison of engineering-and-economical performance, the efficient fields of application of high-efficient method of machining of the rope threads have been determined.
TOPICS: Thread, Machining, Ropes, Machining centers, Surface roughness, Construction, Statistical analysis, Gauss's law, Trajectories (Physics), Design, Cutting, Disperse systems, Wear
research-article  
Zeng Hou, Jamal Sheikh-Ahmad, Firas Jarrar and Fahrettin Ozturk
J. Manuf. Sci. Eng   doi: 10.1115/1.4039074
Thermal history and residual stresses in dissimilar friction stir welding of AA2024 and AZ31 was studied under different tool offsets using a Coupled Eulerian-Lagrangian finite element model and a mechanical model. Welding experiments and residual stresses measurements were conducted to validate the models. Comparisons between the experimental and numerical results indicated good agreement. It was shown that the maximum temperature in the welded zone reached the eutectic reaction temperature for AZ31 and that its location shifted with tool offset from the advancing side to the retreating side. Longitudinal residual stresses changed from tensile under the tool shoulder to compressive beyond this region and it appeared to be the dominant stress component. The transverse stresses were tensile and of lower magnitude. Both the longitudinal and transverse residual stresses have their maximum values within the weld zone near the end of the weld length. For both peak temperatures and residual stresses, higher values were obtained at the advancing side with no tool offset and a 1mm offset to the advancing side, and they became higher at the retreating side with 1mm offset to the retreating side. Lower residual stresses and better weld quality were obtained with tool offset to the aluminum side.
TOPICS: Welding, Residual stresses, Friction, Temperature, Stress, Finite element model, Aluminum
research-article  
Lindsey Bass, Justin Milner, Thomas Gnaupel-Herold and Shawn Moylan
J. Manuf. Sci. Eng   doi: 10.1115/1.4039063
One of the key barriers to widespread adoption of additive manufacturing (AM) for metal parts is the build-up of residual stresses. In the laser-based powder bed fusion process, a laser selectively fuses metal powder layer by layer, generating significant temperature gradients that cause residual stress within the part. This can lead to parts exceeding tolerances and experiencing severe deformations. In order to develop strategies to reduce the adverse effects of these stresses, the stresses first need to be quantified. Cylindrical Nickel Alloy 625 samples were designed with varied outer diameters, inner diameters, and heights. Neutron diffraction was used to characterize the three-dimensional stress state throughout the parts. The stress state of the parts was generally comprised of tensile exteriors and compressive interiors. Regardless of part height, only the topmost scan height of each part experienced large reductions in axial and hoop stress. Improved understanding of the residual stress trends will aid in model development and validation leading to techniques to reduce negative effects of the residual stress.
TOPICS: Stress, Nickel alloys, Lasers, Metal powders, Deformation, Metals, Model development, Neutron diffraction, Additive manufacturing, Temperature gradient, Hoop stress, Residual stresses
research-article  
Kai Chen, Xun Liu and Jun Ni
J. Manuf. Sci. Eng   doi: 10.1115/1.4038993
A hybrid friction stir resistance spot welding process is applied for joining aluminum alloy 6061 to TRIP 780 steel. Compared with conventional resistance spot welding, the applied current density is lower and the welding process remains in the solid state. Compared with conventional friction stir spot welding (FSSW) process, the welding force is reduced and the dissimilar material joint strength is increased. The electrical current is applied in both a pulsed and direct form. With the equal amount of energy input, the approximately same force reduction indicates that the electro-plastic material softening effect is insignificant during FSSW process. The welding force is reduced mainly due to the resistance heating induced thermal softening of materials. With the application of electrical current, a wider aluminum flow pattern is observed in the thermo-mechanically affected zone of weld cross sections and a more uniform hook is formed at the Fe/Al interface. This implies that the aluminum material flow is enhanced. Moreover, the Al composition in the Al-Fe interfacial layer is higher, which means the atomic diffusion is accelerated
TOPICS: Welding, Aluminum alloys, High strength steel, Friction, Flow (Dynamics), Electric current, Aluminum, Joining, Steel, Cross section (Physics), Current density, Heating, Diffusion (Physics)
research-article  
Tizian Bucher, Adelaide Young, Min Zhang, Changjun Chen and Y. Lawrence Yao
J. Manuf. Sci. Eng   doi: 10.1115/1.4038995
To date, metal foam products have rarely made it past the prototype stage. The reason is that few methods exist to manufacture metal foam into the shapes required in engineering applications. Laser forming is currently the only method with a high geometrical flexibility that is able to shape arbitrarily sized parts. However, the process is still poorly understood when used on metal foam, and many issues regarding the foam's mechanical response have not yet been addressed. In this study, the mechanical behavior of metal foam during laser forming was characterized by measuring its strain response via digital image correlation. The resulting data was used to verify whether the temperature gradient mechanism (TGM), well established in solid sheet metal forming, is valid for metal foam, as has always been assumed without experimental proof. Additionally, the behavior of metal foam at large bending angles was studied, and the impact of laser-induced imperfections on its mechanical performance was investigated. The mechanical response was numerically simulated using models with different levels of geometrical approximation. It was shown that bending is primarily caused by compression-induced shortening, achieved via cell crushing near the laser irradiated surface. Since this mechanism differs from the traditional TGM, where bending is caused by plastic compressive strains near the laser irradiated surface, a modified temperature gradient mechanism (MTGM) was proposed. The densification occurring in MTGM locally alters the material properties of the metal foam, limiting the maximum achievable bending angle, without significantly impacting its mechanical performance.
TOPICS: Lasers, Metal foams, Shapes, Temperature gradient, Equipment performance, Materials properties, Engineering systems and industry applications, Mechanical behavior, Approximation, Compression, Sheet metal work, Engineering prototypes
research-article  
Tangbin Xia, Lifeng Xi, Shichang Du, Lei Xiao and Ershun Pan
J. Manuf. Sci. Eng   doi: 10.1115/1.4038996
In recent years, the industry's responsibility to join in sustainable manufacturing is huge, while innovating sustainability has become a new standard. Besides the classic object of cost reduction, industrial enterprises are pursuing energy reduction to meet future needs for sustainable globalization and government legislations for green manufacturing. To maintain manufacturing lines in an energy-effective manner, an energy-oriented maintenance methodology is developed. At the machine layer, the multi-attribute model (MAM) method is extended by modeling the energy attribute. Preventive maintenance (PM) intervals of different machines are dynamically scheduled according to machine deteriorations, maintenance effects and environmental conditions. At the system layer, a novel energy saving window (ESW) policy is proposed to save energy for the whole line. Energy consumption interactivities, batch production characteristics and system-layer maintenance opportunities are comprehensively considered. Real-time choice of PM adjustments is obtained by comparing the energy savings of Advanced PM and Delayed PM. This proposed methodology is demonstrated through the case study based on the collected reliability information from a production line of engine crankshaft. The results can effectively prove the energy effectiveness of the MAM-ESW methodology. The methodology efficiently utilizes standby power, saves energy consumption, avoids manufacturing breakdown and reduces scheduling complexity. Furthermore, this energy-oriented maintenance framework can be applied not only in the automotive industry, but also for a broader range of manufacturing domains such as aerospace, semiconductor and chemical industries.
TOPICS: Maintenance, Manufacturing, Sustainability, Decision making, Machinery, Energy consumption, Governments, Chemical industry, Emergency power, Semiconductors (Materials), Assembly lines, Engines, Reliability, Aerospace industry, Automotive industry, Modeling
research-article  
Christopher Katinas, Weixiao Shang, Yung Shin and Jun Chen
J. Manuf. Sci. Eng   doi: 10.1115/1.4038997
Powder capture efficiency is indicative of the amount of material that is added to the substrate during laser additive manufacturing processes, and thus, being able to predict capture efficiency provides capability of predictive modeling during such processes. The focus of the work presented in this paper is to create a numerical model to understand particle trajectories and velocities, which in turn allows for the prediction of capture efficiency. To validate the numerical model, particle tracking velocimetry experiments at two powder flow rates were conducted on free stream particle spray to track individual particles such that particle concentration and velocity fields could be obtained. Results from the free stream comparison showed good agreement to the trends observed in experimental data and were subsequently used in a direct laser deposition simulation to assess capture efficiency and temperature profile at steady-state. The simulation was validated against a single track deposition experiment and showed proper correlation of the free surface geometry, molten pool boundary, heat affected zone boundary and capture efficiency.
TOPICS: Lasers, Particulate matter, Modeling, Nozzles, Sprays, Computer simulation, Simulation, Geometry, Steady state, Temperature profiles, Additive manufacturing, Flow (Dynamics), Heat
research-article  
Dong Zhang, Xiao-Ming Zhang and Han Ding
J. Manuf. Sci. Eng   doi: 10.1115/1.4038998
Cutting process modelling is still a great challenge due to the severe plastic deformation of the workpiece and intense friction between the workpiece and tool. Nowadays, a novel experimental approach based on digital image correlation technique (DIC) has been utilized to study the severe deformation of the workpiece. However, the experimentally measured velocity field does not necessarily satisfy the equilibrium equation that is one of the most important governing equations in solid mechanics due to the measurement errors; hence, accurate stress fields could hardly be derived. In this paper, we propose a hybrid DIC-FEM approach to optimize the velocity field and generate a stress field that is in equilibrium state. The deviatoric stresses of the main deformation region are calculated by tracking the deformations of the material particles, and the hydrostatic pressures are acquired through solving over-constrained equations derived through finite element method (FEM). Then, the velocity fields are optimized to satisfy the equilibrium equation and the boundary conditions. To validate this approach, the deformations including the velocity and strain yield by the hybrid method are compared with the initial values. The stress fields are presented to demonstrate the satisfactions of the equilibrium equation and the boundary conditions. Moreover, cutting forces calculated through integration of the stress fields are compared against the FEM simulations and the experimentally measured ones.
TOPICS: Finite element methods, Modeling, Cutting, Stress, Deformation, Equilibrium (Physics), Boundary-value problems, Errors, Solid mechanics, Hydrostatic pressure, Engineering simulation, Friction, Particulate matter, Simulation
research-article  
Kadhim A Jabbar and Prabhakar R. Pagilla
J. Manuf. Sci. Eng   doi: 10.1115/1.4038888
A governing equation for web tension in a span considering thermal and viscoelastic effects is developed in this paper. The governing equation includes thermal strain induced by web temperature change and assumes viscoelastic material behavior. A closed-form expression for temperature distribution in the moving web is derivedwhich is utilized to obtain thermal strain. A model for web tension in a multi-span roll-to-roll system can be developed using this governing equation. To evaluate the governing equation, measured data from an industrial web process line are compared with data from model simulations. Since the viscoelastic behavior of web materials is affected by the web temperature change, elevated temperature creep and stress-relaxation experiments are conducted to determine the temperature-dependent viscoelastic parameters of the utilized viscoelastic model. Comparisons of the measured data with model simulation data are presented and discussed. An analysis of the web tension disturbance propagation behavior is also provided to compare transport behavior of elastic and viscoelastic materials.
TOPICS: Manufacturing, Dynamics (Mechanics), Modeling, Tension, Temperature, Simulation, Viscoelastic materials, Relaxation (Physics), Stress, Viscoelasticity, Temperature distribution, Creep
research-article  
Jie Ren, Chiwoo Park and Hui Wang
J. Manuf. Sci. Eng   doi: 10.1115/1.4038889
Assembly through mating a pair of machined surfaces plays a crucial role in many manufacturing processes such as automotive powertrain production, and the mating errors during the assembly (i.e., gaps between surfaces) can cause significant internal leakage and functional performance problems. The surface mating errors are difficult to diagnose because they are not measurable. Current in-plant quality control for surface mating focuses on controlling the surface flatness of each individual part before they are mated, and the mating errors are indirectly evaluated by a pressurized sealing test to check whether any pressure drop occurs. However, it does not provide any clue to engineers about the origins and the root cause of the internal leakage. To address these limitations, this paper presents a pressurized color-tracking method to directly measure internal leak areas. By using the measurements of leak areas and the profiles of surfaces mated as training data along with Hagen-Poiseuille law, this paper develops a novel diagnostic method to predict potential leak areas (leakage paths) given the measurements on the profiles of mating surfaces. The effectiveness and robustness of the proposed method are verified by a simulation study and an experiment. The approach provides practical guidance for the subsequent assembly process as well as troubleshooting in surface machining processes.
TOPICS: Manufacturing, Modeling, Leakage, Errors, Poiseuille flow, Pressure drop, Robustness, Simulation, Sealing (Process), Machining, Quality control, Engineers
research-article  
David Corbin, Abdalla R. Nassar, Edward (Ted) Reutzel, Allison M. Beese and Panagiotis (Pan) Michaleris
J. Manuf. Sci. Eng   doi: 10.1115/1.4038890
The effect of substrate surface preheating on part distortion in laser cladding is investigated through the experimental results of laser deposited Ti-6Al-4V. In situ temperature and distortion measurements were used to monitor the behavior of the substrates before, during, and after deposition. The resulting trends were analyzed, and it was determined that substrate preheating reduces the amount of distortion accumulated in thin substrates but increases the amount of distortion accumulated in thick substrates. Additionally, substrate preheating was found to cause additional distortion of thick substrates during cool-down after processing had finished. The in situ measurements suggest that the stress relaxation of Ti-6Al-4V at elevated temperatures increases the distortion observed in thick substrates, but has minimal effect on distortion in thin substrates.
TOPICS: Lasers, Temperature, Relaxation (Physics), Stress, Cladding systems (Building)
research-article  
Brian Davis, David Dabrow, Peter G. Ifju, Guoxian Xiao, Steven Y. Liang and Yong Huang
J. Manuf. Sci. Eng   doi: 10.1115/1.4038891
Machining is among the most versatile material removal processes in the manufacturing industry. To better optimize the machining process, the knowledge of shear strains and shear strain rates within the primary shear zone (PSZ) during chip formation has been of great interest. The objective of this study is to study the strain and strain rate progression within the PSZ both in the chip flow direction and along the thickness direction during machining equal channel angular extrusion (ECAE) processed titanium (Ti). ECAE-processed ultrafine-grained (UFG) Ti has been machined at cutting speeds of 0.1 and 0.5 m/s, and the shear strain and shear strain rate have been determined using high speed imaging and digital image correlation. It is found that the chip morphology is saw-tooth at 0.1 m/s while continuous at 0.5 m/s. The cumulative shear strain and incremental shear strain rate of the saw-tooth chip morphology can reach approximately 3.9 and 2.4×103 s-1, respectively, and those of the continuous chip morphology may be approximately 1.3 and 5.0×103 s-1, respectively. There is a distinct peak shift in the shear strain rate distribution during saw-tooth chip formation while there is a stable peak position of the strain rate distribution during continuous chip formation. The PSZ thickness during saw-tooth chip formation is more localized and smaller than that during continuous chip formation (28 versus 35 µm).
TOPICS: Machining, Shear (Mechanics), Titanium, Imaging, Flow (Dynamics), Cutting, Manufacturing industry, Extruding
research-article  
Devashish Kulkarni, Soham S. Mujumdar and Shiv G Kapoor
J. Manuf. Sci. Eng   doi: 10.1115/1.4038892
The purpose of this paper is to study the effect of cutting tool surface geometry and the ACF spray parameters on the characteristics of the thin film formed in an atomization-based cutting fluid (ACF) delivery system. A computational model is developed using three sub-models that are used to predict the carrier gas flow, droplet trajectories and the film formation, respectively. The model is validated through film thickness measurements using a laser displacement sensor. Turning inserts with chip-breaking grooves along with a conventional flat insert are used to study the effect of cutting tool surface geometry on the model-predicted film characteristics, including film thickness and velocity. Machining experiments are also conducted to investigate the effect of film characteristics on the machining performance in terms of tool wear, which show that the tool wear is minimum at a certain desired film thickness value and large film velocity value. Carrier gas pressure and cutting fluid flow rate are also varied to study the effect of ACF spray parameters on the film characteristics. Increase in the fluid flow results in increase in both film thickness and velocity, while an increase in the gas pressure results in the reduction of the film thickness but an increase in the film velocity.
TOPICS: Fluids, Machining, Cutting, Titanium, Film thickness, Geometry, Sprays, Cutting tools, Pressure, Fluid dynamics, Wear, Thin films, Sensors, Gas flow, Lasers, Drops, Turning, Displacement
research-article  
Chao Li, Z.Y. Liu, X.Y. Fang and Y.B. Guo
J. Manuf. Sci. Eng   doi: 10.1115/1.4038893
Rapid heating and cooling thermal cycle of metals in selective laser melting (SLM) generates high tensile residual stress which leads to part distortion. However, how to fast and accurately predict residual stress and the resulted part distortion remains a critical issue. It is not practical to simulate every single laser scan to build up a functional part due to the exceedingly high computational cost. Therefore, scaling-up the material deposition rate via increasing heat source dimension and layer thickness would dramatically reduce the computational cost. In this study, a multiscale scalable modeling approach has been developed to enable fast prediction of part distortion and residual stress. Case studies on residual stress and distortion of the L-shaped bar and the bridge structure were presented via the deposition scalability and validation with the experimental data. The influence of laser scanning strategy on residual stress distribution and distortion magnitude of the bridges was also investigated.
TOPICS: Lasers, Simulation, Stress, Melting, Bridges (Structures), Dimensions, Heat, Metals, Stress concentration, Heating and cooling, Modeling, Cycles
research-article  
Cengiz Baykasoglu, Oncu Akyildiz, Duygu Candemir, Qingcheng Yang and Albert C. To
J. Manuf. Sci. Eng   doi: 10.1115/1.4038894
Laser engineering net shaping (LENS) is one of the representative processes of directed energy deposition (DED) in which a moving heat source having high-intensity melts and fuses metal powders together to print parts. The complex and non-uniform thermal gradients during the laser heating and cooling cycles in the LENS process directly affects the microstructural characteristics, and thereby the ultimate mechanical properties of fabricated parts. Therefore, prediction of microstructure evolution during the LENS process is of paramount importance. The objective of this study is to present a thermo-microstructural model for predicting microstructure evolution during the LENS process of Ti-6Al-4V. Firstly, a detailed transient thermal finite element model is developed and validated for a sample LENS process. Then, a density type microstructural model, which enables calculation of the a-phase fractions, (i.e. Widmanstätten colony and basketweave a-phase fractions), ß-phase fraction and alpha lath widths during LENS process is developed and coupled to the thermal model. The microstructural algorithm is first verified by comparing the phase fraction results with the results presented in the literature for a given thermal history data. Secondly, the average lath width values calculated using the model are compared with the experimentally measured counterparts, where a reasonable agreement is achieved in both cases.
TOPICS: Density, Heat, Lasers, Lenses (Optics), Metal powders, Transients (Dynamics), Mechanical properties, Algorithms, Heating and cooling, Cycles, Finite element model, Additive manufacturing, Temperature gradient
Technical Brief  
Tsuyoshi Furushima, Hideki Sato, Ken-ichi Manabe and Sergei Alexandrov
J. Manuf. Sci. Eng   doi: 10.1115/1.4038822
This paper deals with the identification of an empirical equation for predicting free surface roughness evolution. The equation has been proposed elsewhere and, in contrast to widely used equations, assumes that the evolution of free surface roughness is controlled by two kinematic variables, the equivalent strain and the logarithmic strain normal to the free surface. Therefore, an experimental program is designed to account for the effect of the mode of deformation on free surface roughness evolution. Thin sheets of aluminum alloy A5052-O and pure copper C1220P-O alloys are used to conduct the experimental program. In addition, numerical simulation is performed to calculate the evolution of free surface roughness under the same conditions. Comparison of experimental and numerical results shows that the accuracy of the numerical results is good enough. Then, numerical simulation is extended to the domain in which no experimental results are available. In this way the entire domain of the function involved in the empirical equation for predicting free surface roughness evolution is covered. Discrete functions so found are fitted to polynomials. As a result, continuous functions that represent the empirical equation for predicting free surface roughness evolution for A5052-O and C1220P-O alloys are determined. These equations can be used in conjunction with solutions to boundary value problems in plasticity for predicting the evolution of free surface roughness in metal forming processes.
TOPICS: Copper, Aluminum alloys, Surface roughness, Alloys, Computer simulation, Boundary-value problems, Polynomials, Metalworking, Kinematics, Plasticity, Deformation
research-article  
Jianjian Wang, Jianfu Zhang, Pingfa Feng, Ping Guo and Qiaoli Zhang
J. Manuf. Sci. Eng   doi: 10.1115/1.4038728
In order to further improve the processing performance of rotary ultrasonic machining (RUM), a novel longitudinal-torsional coupled vibration was applied to the RUM. An experimental study on quartz glass was performed to access the longitudinal-torsional coupled rotary ultrasonic machining (LTC-RUM) feasibility of a brittle material. The LTC-RUM was executed through the helical flutes addition on the tool of conventional longitudinal rotary ultrasonic machining (Con-RUM). The experimental results demonstrated that the LTC-RUM could reduce the cutting force by 55% and the edge chipping size at the hole exit by 45% on average, compared to the Con-RUM. Also, the LTC-RUM could improve the hole wall quality through the surface roughness reduction, especially when the spindle speed was relatively low. The mechanism of superior processing performance of LTC-RUM was the corresponding specific moving trajectory of diamond abrasives, along with the higher lengths of lateral cracks that produced in the abrasives indentation on the workpiece material. The higher edge chipping size at the hole entrance of LTC-RUM indicated a higher length of lateral cracks in LTC-RUM, due to the maximum cutting speed increase. In addition, the effect of spindle speed on the cutting force and surface roughness variations verified the moving trajectory important role of the diamond abrasive in the superior processing performance mechanism of LTC-RUM.
TOPICS: Brittleness, Ultrasonic machining, Cutting, Diamonds, Abrasives, Surface roughness, Fracture (Materials), Trajectories (Physics), Vibration, Glass, Quartz
research-article  
Zhenguo Nie, Gang Wang, Dehao Liu and Yiming Rong
J. Manuf. Sci. Eng   doi: 10.1115/1.4038729
Accurate information about the evolution of the temperature field is a theoretical prerequisite for investigating grinding burn and optimizing the process parameters of grinding process. This paper proposed a new statistical model of equivalent grinding heat source with consideration of the random distribution of grains. Based on the definition of the Riemann integral, the summation limit of the discrete point heat sources was transformed into the integral of a continuous function. An FEM (finite element method) simulation was conducted to predict the grinding temperature field with the embedded net heat flux equation. The grinding temperature was measured with a specially designed in situ infrared system and was formulated by time-space processing. The reliability and correctness of the statistical heat source model were validated by both experimental temperature-time curves and the maximum grinding temperature, with a relative error of less than 20%. Finally, through the FEM-based inversed calculation, an empirical equation was proposed to describe the HTC (heat transfer coefficient) changes in the grinding contact zone for both conventional grinding and creep feed grinding.
TOPICS: Heat, Grinding, Temperature, Finite element methods, Errors, Heat flux, Heat transfer coefficients, Reliability, Simulation, Creep
Review Article  
Michael P. Sealy, Gurucharan Madireddy, Robert Williams, Prahalad Rao and Maziar Toursangsaraki
J. Manuf. Sci. Eng   doi: 10.1115/1.4038644
Hybrid additive manufacturing (hybrid-AM) has described hybrid processes and machines as well as multi-material, multi-structural, and multi-functional printing. The capabilities afforded by hybrid-AM are rewriting the design rules for materials and adding a new dimension in the design for additive manufacturing paradigm. This work primarily focuses on defining hybrid-AM in relation to hybrid manufacturing and classifying hybrid-AM processes. Hybrid-AM machines, materials, structures, and function are also discussed. Hybrid-AM processes are defined as the use of additive manufacturing (AM) with one or more secondary processes or energy sources that are fully coupled and synergistically affect part quality, functionality, and/or process performance. Historically, defining hybrid manufacturing processes centered on process improvement rather than improvements to part quality or performance; however, the primary goal for the majority of hybrid-AM processes is to improve part quality and performance. Hybrid-AM processes are distinguished from post-processing operations that do not meet the fully coupled criterion. Secondary processes and energy sources include subtractive and transformative manufacturing technologies, such as machining, re-melting, peening, rolling, and friction stir processing. As the demand for hybrid-AM increases, new economic and sustainability tools are needed as well as sensing technologies that can play a critical role in defect detection and part and processes characterization. Hybrid-AM has ushered in the next evolutionary step in additive manufacturing and has the potential to profoundly change the way goods are manufactured.
TOPICS: Additive manufacturing, Machinery, Manufacturing, Design, Energy resources, Manufacturing technology, Sustainability, Flaw detection, Printing, Shot peening, Melting, Machining, Dimensions, Friction
research-article  
Mohammad Hossain, Chandra Nath, Thomas M. Tucker, Richard Vuduc and Thomas Kurfess
J. Manuf. Sci. Eng   doi: 10.1115/1.4038599
Machining is one of the major manufacturing methods having very wide applications in industries. The lack of an easy and intuitive programmability in conventional toolpath planning approach in machining leads to significantly higher manufacturing cost for CNC-based prototyping. In standard computer aided manufacturing (CAM) packages, general use of B-rep or NURBS-based representations of the CAD interfaces challenge core computations of tool trajectories generation process, such as, surface offsetting to be completely automated. In this work, the problem of efficient generation of free-form surface offsets is addressed with a novel volumetric (voxel) representation. It presents an image filter-based offsetting algorithm, which leverages the parallel computing engines on modern graphics processor unit (GPU). Additionally, in order to further accelerate the offset computation the problem of offsetting with a large distance is decomposed into successive offsetting using smaller distances. The performance trade-offs between accuracy and computation time of the offset algorithms is thoroughly analyzed. The developed GPU implementation of the offsetting algorithm is found to be robust in computation, and has demonstrated a 50-fold speedup on single graphics card (NVIDIA GTX780Ti) relative to prior best-performing dual sockets quad-cores CPU implementation. The proposed offsetting approach has been validated for a variety of complex parts produced on different multi-axis CNC machine tools including turning, milling, and compound turning-milling.
TOPICS: Resolution (Optics), Machining, Additive manufacturing, Graphics processing units, Computation, Algorithms, Milling, Computer numerical control machine tools, Manufacturing, Tradeoffs, Computer-aided design, Computer-aided manufacturing, Filters, Engines

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