3D Workpiece Research Articles

Development and Creation of Ancient Sandstone Carvings Using 3D Software Tools and Mobile/Tablet Devices

In the area of Phayao Province that used to be part of the ancient Lanna Kingdom, there are unique works of art that can be found until today, which are sandstone carvings caused by religious beliefs resulting in works such as Buddha statues. These are art related to religion. Nowadays, these works of art have started to fade away and receive less and less attention from people. The creation of art objects in this research therefore uses the interpretation of the creative objects in line with people’s lifestyles by selecting the lotus, which is a plant related to rivers, and is important in religion. In the lotus, which is interconnected and aligned with Buddhism, and in harmony with a way of life that aligns with the river, creative works are found in various forms, connecting people in Buddhism, including sandstone carving. In this creation, digital technology tools and methods are used to collect data to create a 3D work piece. Photogrammetry is used to record detailed proportions and information and customization of 3D work pieces. In these steps, mobile phone-type tools are used to collect image data to create the 3D work or an application is used to customize 3D work pieces from a tablet device to create prototypes of sandstone sculptures from the artisans that remain today. This can be seen in creating, maintaining, and recording digital data, creation, and the integration of knowledge. This demonstrates that today’s tools and portable devices can help create more creative pieces of work and preserve art and culture.

Analysis of reaction forces in fixture locating points: An Analytical, numerical, and experimental study

Reaction forces are important parameters in fixture design. They are generated by the clamping forces and machining loads at the fixture locating points. These forces are used as input values in the determination of clamping forces, fixture stiffness, and workpiece deformation. In this paper, an analytical model based on the minimum norm principle was developed to calculate these forces. Numerical simulations and experimental tests were performed on a 3D polyhedral workpiece to validate the model. The simulations were conducted using Abaqus® software and the experimental tests used a fixture and a 3D polyhedral workpiece. The theoretical, numerical, and experimental results showed good agreement for the normal component of reaction forces. The maximum errors of 3.9% and 15% were observed between the theoretical predictions compared to the numerical and experimental results, respectively. The model was also used to study the effects of two influential parameters, the coefficient of friction and clamping force, on the reaction forces. The good agreement between the theoretical, numerical, and experimental results demonstrated the efficiency of the proposed model in the rapid calculation of reaction forces for fixturing 3D polyhedral workpieces.

Modelling and simulation of controlled depth abrasive water jet machining (AWJM) for roughing passes of free-form surfaces

Controlled depth abrasive waterjet machining (AWJM) is an unconventional and promising process for materials introducing challenges in conventional machining for high value manufacturing (HVM) industries such as aerospace and automotive. In such applications, waterjet acts as a flexible cutting tool compared to conventional milling. The kerf profile, i.e. the removed material volume, nonlinearly depends on the process parameters such as water pressure, jet traverse speed, abrasive rate, and stand-off-distance unlike the deterministic case in mechanical milling. Thus, prediction of kerf profile, i.e. width, depth, and shape, is of great importance for accurate and efficient process development and tool path generation in AWJM. In this paper, a novel analytical model is proposed for prediction of kerf profile, relying on conservation of energy and momentum, where the material removal is related to the machinability number of the workpiece material, so that the requirement of calibration tests is eliminated. Then, the proposed AWJM process model is used in a framework to predict 3D in-process workpiece (IPW) geometry, which is represented using signed distance field (SDF) approach. The process model is verified by experimental results with an average error of 15%, where the machine profiles are measured by confocal optical microscopy. In some of the experiments, undulated material removal was observed which is due to inconsistent abrasive supply of the system, which is considered to be the major source of the kerf depth prediction errors. The IPW simulation model is verified by variable jet traverse speed AWJM experiments, considering the significant effect of jet traverse speed on the kerf depth. The machined specimens are sectioned along the jet traverse direction and the cross section of the test pieces is visually compared with the simulations. The machined profiles introduced some amount of undulated profile, which may be attributed to the non-consistent abrasive supply in the system. It is shown that the proposed IPW simulation approach demonstrates a reasonable accuracy to plan controlled depth AWJM processes.

Parametric modeling method for integrated design and manufacturing of radial compressor impeller

Radial compressor impeller (RCI) manufacturing is moving toward to improve competitiveness through smart manufacturing. Although current CAD (computer-aided design) and CAM (computer-aided manufacturing) techniques provide multiple tools to construct and optimize complicated geometries of RCI, an adjustment of blade shape often leads to nonparametric geometric reconstruction. As the key geometric elements in RCI, set of streamlines (SSL) and meridional section (MS) play vital roles in modeling and aerodynamic optimization. This paper presents a novel approach for automatic extraction of SSL and MS from a RCI 3D model or workpiece. Furthermore, the presented method can interactively construct a parameterized RCI platform, which inputs and outputs the presented RCI parameters to existing CFD and CAM systems rapidly and effectively. An integrated acquisition is employed. The straight generatrix vectors (SGVs) are identified and their boundary points are defined. After the uniform partition of SGV segments, the sequent equant points along spanwise direction are packaged to fit SSL. To manipulate the smoothness and approximation, a double-fitting method is performed to generate SSL. A parameterized system for extracting SSL and modeling RCI is developed. The validities of the presented method in different systems are demonstrated. Furthermore, the presented method breaks conventional RCI development procedure and shortens RCI product cycles, which is desirable and significative for integrated RCI design and manufacturing.

Advanced screw thread metrology using an areal measuring strategy and a holistic evaluation method

With respect to current manufacturing tolerances, the inspection of screw threads in the field of precision engineering requires measurement uncertainties that cannot be achieved with the standardized measuring procedure in the current EURAMET cg-10 calibration guide. Because the conventional measuring strategy and evaluation method for calibrating screw threads refers only to specific lines along two axial sections, the complexity of the 3D workpiece is not taken into account. The manufacturing industry requires a paradigm shift from line-oriented to areal-oriented measuring strategies. This article presents a holistic approach that starts with the parameterization of complex screw thread geometry, continues with a concept for an areal measuring strategy and ends with the 3D evaluation of the gathered point cloud and the determination of the measurement uncertainty using numerical simulation.

Quality assurance and process control in virtual reality

In this study, quality assurance and automatic process control are combined with a Virtual Reality enabled man-in-the-loop system. Increasingly flexible manufacturing demands increasingly flexible process control. Autonomous smart manufacturing systems increase the amount of tolerable variation in manufacturing processes by reacting to minor changes in part positioning, preparation, and other issues by adaptive process parameters. Due to unforeseen circumstances or high variation, there may be workpieces requiring human interaction to continue manufacturing, repair, or be sent to recycling or even waste. Human-robot collaboration may be achieved by safety systems allowing the human operator within the working area of a robot, or then augmented or virtual reality may allow a human operator to assess the situation remotely. The AR and VR technologies may include information usually invisible to the operator. In this study, a 3D workpiece is measured, and defects are visualized in a VR environment, focusing on the geometrical distortion of the workpiece. Measurement had a standard deviation of +/- 0.067 mm for the root gap. Visualization facilitates rapid human feedback in case distortion is getting out of bounds. A man-in-the-loop system is used to provide adjustments to the robot parameters.

Virtual Reality Enabled Manufacturing of Challenging Workpieces

Increasing automation in the manufacturing workpieces demands increased flexibility of the manufacturing system when it comes to part handling and selecting suitable manufacturing parameters. In some cases, this can be fulfilled by intelligent manufacturing systems working autonomously, but with increasingly challenging workpieces human-robot collaboration may be required to bring the experience of a human expert into the loop. While human-robot collaboration may be achieved by improving robot safety systems to allow humans to work in close proximity with robots, an alternative approach is to implement Virtual Reality (VR) environment. In this paper, we demonstrate measuring a 3D workpiece, importing the workpiece model into a VR environment and manipulating the workpiece. The technology allows adding sensory information usually not available by adding thermal imaging or simulating audio cues. The research problem of the study is the positioning accuracy issue of sheet metal production while using industrial robots. The research question is how the workpieces and jigs can be scanned the way that the positioning and the angular misalignment can be measured and corrected on robot controller. The study indicates that a laser sensor can be used to measure object dimensions with sufficient accuracy for robot assembly.

3D involute gear evaluation – Part I: Workpiece coordinates

The definition of 3D workpiece coordinates for cylindrical involute gears, together with their formal relation to conventional cross sections, are prerequisites for an unambiguous and thus reliable evaluation of 3D measurement data. Both will be described in this article, as no corresponding information is currently available in national or international standards and guidelines. The definitions and calculation methods presented here are part of reference algorithms used by the Physikalisch-Technische Bundesanstalt (PTB), the national metrology institute of Germany, to certify gear evaluation software.

RETRACTED ARTICLE: A novel approach to simulate surface topography based on motion trajectories and feature theories of abrasive grains

The method of combining simulations with experiments is used in this paper. Both traditional grinding and point grinding are considered as the research objects. The motion paths of grains in the point grinding process will completely differ from those in the traditional grinding process because of the non-zero inclination angle α. Thus, a coordinate transformation between the grinding wheel and the workpiece is performed. Then, a brand-new formation mechanism for a 3D workpiece surface is established by combining selected trajectories to simulate the formation of the surface. The interference trajectories are effectively screened by iterating over the cutting paths of all grains on the grinding wheel surface to improve the prediction accuracy for the machined surface. Both the surface features of the grinding wheel and the elastic-plastic deformation of the workpiece material are investigated and analyzed for the first time in this paper; they are considered in the motion trajectories of the abrasive grains to make the simulated grinding surface topography closer to that formed in the actual grinding process. The trend of the influence of the variable angle α on the surface roughness is obtained and analyzed. The comparison and analysis of the simulation and experimental results prove that the simulated surface quality of the grinding workpiece is consistent with that measured in a 3D microtopography analysis, and the curve shapes in the cross-section and surface roughness evaluations are also consistent. The surface quality of a grinding workpiece can be effectively predicted using this simulation method.

Real-time 3D work-piece tracking with monocular camera based on static and dynamic model libraries

PurposeThis paper aims to propose a novel real-time three-dimensional (3D) model-based work-piece tracking method with monocular camera for high-precision assembly. Tracking of 3D work-pieces with real-time speed is becoming more and more important for some industrial tasks, such as work-pieces grasping and assembly, especially in complex environment.Design/methodology/approachA three-step process method was provided, i.e. the offline static global library generation process, the online dynamic local library updating and selection process and the 3D work-piece localization process. In the offline static global library generation process, the computer-aided design models of the work-piece are used to generate a set of discrete two-dimensional (2D) hierarchical views matching libraries. In the online dynamic library updating and selection process, the previous 3D location information of the work-piece is used to predict the following location range, and a discrete matching library with a small number of 2D hierarchical views is selected from dynamic local library for localization. Then, the work-piece is localized with high-precision and real-time speed in the 3D work-piece localization process.FindingsThe method is suitable for the texture-less work-pieces in industrial applications.Originality/valueThe small range of the library enables a real-time matching. Experimental results demonstrate the high accuracy and high efficiency of the proposed method.

Surface topomorphy and roughness prediction in micro-ball-end milling using a CAD-based simulation

Ball-end milling is a widely used finishing process in metal cutting. The small size and the complex of metal machining components are the main reasons for implementing milling in microscale. The surface profile and the dimensional accuracy are key factors on the quality of surface of a product. The selection of optimal cutting conditions can be accomplished by utilising simulation models which can involve the kinematics and the strategies of milling processes. Therefore, the analytical prediction of the produced surface quality (topomorphy and roughness) can be reached. The present study indicates a 3D simulation model of ball-end micro-milling process developed in commercial CAD software and its optical and computing results. Micro-milling experiments of Al7075-T6 were carried out in different conditions by the use of a high speed spindle. A computer application was developed to calculate the roughness out of the controlled points of a plane that intersects with the 3D workpiece. The calculated roughness was compared with the measured surface roughness and the surface topomorphy was captured through a stereo microscope.

Surface topomorphy and roughness prediction in micro-ball-end milling using a CAD-based simulation

Ball-end milling is a widely used finishing process in metal cutting. The small size and the complex of metal machining components are the main reasons for implementing milling in microscale. The surface profile and the dimensional accuracy are key factors on the quality of surface of a product. The selection of optimal cutting conditions can be accomplished by utilising simulation models which can involve the kinematics and the strategies of milling processes. Therefore, the analytical prediction of the produced surface quality (topomorphy and roughness) can be reached. The present study indicates a 3D simulation model of ball-end micro-milling process developed in commercial CAD software and its optical and computing results. Micro-milling experiments of Al7075-T6 were carried out in different conditions by the use of a high speed spindle. A computer application was developed to calculate the roughness out of the controlled points of a plane that intersects with the 3D workpiece. The calculated roughness was compared with the measured surface roughness and the surface topomorphy was captured through a stereo microscope.

Performance Analysis of Ball End Magnetorheological Finishing Process with MR Polishing Fluid

A ball end magnetorheological finishing (BEMRF) process was developed for finishing a flat as well as 3D workpiece surfaces. The BEMRF process has a wide scope in today's advanced manufacturing systems for finishing 3D complex surfaces. Magnetorheological (MR) polishing fluid is used as finishing medium in BEMRF process. The constituent of MR polishing (MRP) fluid includes ferromagnetic carbonyl iron powder, abrasives, and base fluid medium. The workpiece surface is mainly finished by abrasives contained in MRP fluid. Therefore, the different mesh size from 400 to 1200 and volume percent concentration from 5% to 25% of abrasives in MRP fluid were chosen as factors to study their effects on the developed process performance in terms of percent change in roughness values. Silicon carbide abrasives were chosen in the present experimental investigation. Experiments were performed on the ferromagnetic ground surfaces whose initial roughness values (Ra) were measured in the range of 0.428 to 0.767 µm. The experimental results revealed that the MRP fluid with 15 vol % abrasives of mesh number 400 demonstrated better improvements in surface texture of finished surface as compared to other MRP fluid compositions. The finished surface characteristics and textures were studied at microscopic level using scanning electron microscopy and atomic force microscopy.

A Selective Multiclass Support Vector Machine Ensemble Classifier for Engineering Surface Classification Using High Definition Metrology

The surface appearance is sensitive to change in the manufacturing process and is one of the most important product quality characteristics. The classification of workpiece surface patterns is critical for quality control, because it can provide feedback on the manufacturing process. In this study, a novel classification approach for engineering surfaces is proposed by combining dual-tree complex wavelet transform (DT-CWT) and selective ensemble classifiers called modified matching pursuit optimization with multiclass support vector machines ensemble (MPO-SVME), which adopts support vector machine (SVM) as basic classifiers. The dual-tree wavelet transform is used to decompose three-dimensional (3D) workpiece surfaces, and the features of workpiece surface are extracted from wavelet sub-bands of each level. Then MPO-SVME is developed to classify different workpiece surfaces based on the extracted features and the performance of the proposed approach is evaluated by computing its classification accuracy. The performance of MPO-SVME is validated in case study, and the results demonstrate that MPO-SVME can increase the classification accuracy with only a handful of selected classifiers.

Compensation of geometrical errors of CAM/CNC machined parts by means of 3D workpiece model adaptation

In modern industry conditions, it is very important to develop methodologies for reducing costs and achieving the maximum quality of machined parts, especially considering the dimensional accuracy of workpieces. Geometrical and dimensional inaccuracies are due to several factors, such as workpiece and tool deformation during machining, thermal distortions, tool wear, and machine tool inaccuracy. There are two main approaches used to improve the accuracy of workpieces: mapping the tool–workpiece displacement and altering the finishing tool path or the interpolated tool position to compensate the dimensional errors. The aim of this paper is to propose a new compensation approach, based on adaptation of the geometrical 3D CAD model used to generate trajectories by CAM software. The concept is to produce a first workpiece using a CAM-generated tool path. Then, the workpiece is measured using optical methods and the displacements between the ideal workpiece model and the measured point-cloud are calculated. Eventually, the displacement vectors are applied to calculate a compensated workpiece model. Such model is then used as a reference by CAM software to calculate the compensated tool path, which is applied for production of subsequent workpieces. The mathematical background and implementation details are given together with an example of application to a benchmark workpiece purposely machined with inaccurate tools. As the results show, the new approach was able to compensate the geometrical inaccuracies of the benchmark workpiece.

Influence of HSM cutting parameters on the surface integrity characteristics of hardened AISI H13 steel

The purpose of this study is to evaluate the influence of the cutting parameters of high-speed machining milling on the characteristics of the surface integrity of hardened AISI H13 steel. High-speed machining has been used intensively in the mold and dies industry. The cutting parameters used as input variables were cutting speed (v c), depth of cut (a p), working engagement (a e) and feed per tooth (f z ), while the output variables were three-dimensional (3D) workpiece roughness parameters, surface and cross section microhardness, residual stress and white layer thickness. The subsurface layers were examined by scanning electron and optical microscopy. Cross section hardness was measured with an instrumented microhardness tester. Residual stress was measured by the X-ray diffraction method. From a statistical standpoint (the main effects of the input parameters were evaluated by analysis of variance), working engagement (a e) was the cutting parameter that exerted the strongest effect on most of the 3D roughness parameters. Feed per tooth (f z ) was the most important cutting parameter in cavity formation. Cutting speed (v c) and depth of cut (a p) did not significantly affect the 3D roughness parameters. Cutting speed showed the strongest influence on residual stress, while depth of cut exerted the strongest effect on the formation of white layer and on the increase in surface hardness.

Mechanism of material removal in ball end magnetorheological finishing process

Ball end magnetorheological finishing (BEMRF) process was developed for finishing flat and 3D workpiece surfaces. A finishing tool is used to flow pressurized magnetorheological polishing fluid through the center of the rotating tool core and gets stiffened in the form of a magnetically controlled ball end shape at the tip surface of the tool. This forms a polishing spot of controlled size and shape which is used as a finishing medium by guiding it to follow the surface to be finished through computer controlled 3-axes motion. In the present study, an attempt has been made to understand the material removal and surface finishing mechanism in BEMRF process on a ferromagnetic workpiece. Based on experimental observations and force measurements, a mathematical model has been developed for modelling of magnetic field-induced normal force during finishing by BEMRF process. It is very difficult to understand the complex structure of rotating MR-polishing fluid during finishing operation, so a model of magnetic normal force is developed based on certain assumptions. Finished surfaces were also analyzed using scanning electron microscope (SEM) and atomic force microscope (AFM) to understand mechanism of material removal. In order to understand the material removal process and wear behavior during finishing, different modes of abrasive-workpiece interaction have been analyzed with respect to measured magnetic normal forces. The developed mathematical model has been used to predict magnetic normal finishing force and compared with the experimentally obtained results. Both were found in close agreement. The effect of variation in magnetic normal force was also observed experimentally in terms of percentage change in surface roughness during finishing.

Nanofinishing of a typical 3D ferromagnetic workpiece using ball end magnetorheological finishing process

A nanofinishing process using ball end magnetorheological (MR) finishing tool was developed for finishing 3D workpiece surfaces. In this process a ball end shape of MR polishing fluid is generated at the tip surface of the rotating tool which is used as a finishing spot. This paper is focused on surface finishing and performance evaluation of a typical three-dimensional ferromagnetic workpiece using a ball end magnetorheological finishing process. A typical 3D workpiece surfaces were made by milling process at different angles of projection such as flat, 30°, 45° and curve surfaces. The experiments were performed on these typical workpiece surfaces by ball end MR finishing setup to study the effect of number of finishing passes on final surface roughness. The experiments were also performed on a flat ground surface to study the process performance as compared with the milled workpiece surfaces. The finite element analysis has been done to study the distribution of magnetic flux density at tip surface of the tool with an inserted typical 3D workpiece surfaces. When these typical workpiece surfaces were finished by proposed MR finishing process, the surface roughness were reduced as low as 16.6nm, 30.4nm, 71nm and 123.7nm respectively on flat, 30°, 45° and curve surfaces for 60 passes of finishing. The roughness of flat ground surface was reduced as low as 19.7nm for 120min of finishing. The experimental results demonstrated that the newly developed ball end magnetorheological finishing process was effective in finishing typical 3D ferromagnetic workpiece surfaces.

Pose Estimation for 3D Workpiece Grasping in Industrial Environment Based on Evolutionary Algorithm

In industrial fields, precise pose of a 3D workpiece can guide operations like grasping and assembly tasks, thus precise estimation of pose of a 3D workpiece has received intensive attention over the last decades. When utilizing vision system as the source of pose estimation, it is difficult to get the pose of a 3D workpiece from the 2D image data provided by the vision system. Conventional methods face the complexity of model construction and time consumption on geometric matching. To overcome these difficulties, this paper proposes a search-based method to determine appropriate model and pose of a 3D workpiece that match the 2D image data. Concretely, we formulate the above problem as an optimization problem aiming at finding appropriate model parameters and pose parameters which minimizes the error between the notional 2D image (given by the model/pose parameters being optimized) and the real 2D image (provided by the vision system). Due to the coupling of model and pose parameters and discontinuity of the objective function, the above optimization problem cannot be tackled by conventional optimization techniques. Hence, we employ an evolutionary algorithm to cope with the optimization problem, where the evolutionary algorithm utilizes our problem-specific knowledge and adopts a hierarchical coarse-to-fine style to meet the requirement of online estimation. Experimental results demonstrate that our method is effective and efficient.

Pose Estimation for 3D Work Piece Using Differential Evolution Algorithm

In industrial fields, precise pose of a 3D object is the prerequisite of the subsequent tasks like grasping and assembly, thus many researches on accurate pose estimation of a 3D object are explored over the last decades. To get the pose of a 3D work piece from the 2D image data is a challenging task in industrial applications. This paper proposes a fully automated pose estimation system which is capable to estimate the accurate model and pose of a 3D work piece that can well match the 2D image data. This is achieved by representing the above problem as an optimization problem aiming at finding the accurate model parameters and pose parameters of work piece by minimize the difference between the real 2D image and the hypothetical 2D image that produced through the given parameters from 3D image. Due to the coupling of the unknown model and pose parameters and the discontinuity of the objective function, the above optimization problem cannot be solved through traditional optimization approaches. Hence, we utilize a heuristic optimization strategy - Differential Evolution to cope with the problem. The experimental results demonstrate the effectiveness of the proposed method.