Advanced products demand advanced CAD, CAM, and digital engineering systems. This is the main consideration in this special issue.
It is well understood by all manufacturers nowadays that CAD, CAM, and digital engineering systems behave as “hidden factories” of engineering information processing and are indispensable to the accomplishment of their daily tasks. No products can be planned, designed, machined, and assembled without these hidden factories. The history of CAD/CAM goes back nearly five decades, yet the technologies are still immature: a lot of technical issues remain to be solved because new materials and structures have been introduced in products, new manufacturing technologies have been utilized, and new social needs, such as the need for “eco-X” or “human-oriented” products, have grown along with the dramatic changes in society. New high-performance computing resources, such as Web-based computing or GPU-computing, have also become available for implementation in these systems.
Thirteen technical papers in this issue tackle these challenges, proposing solutions from utilizing technologies, including computer-aided geometric design (CAGD), CAD, CAE, CAPP, and CAM, as well as novel human interfaces for these systems. Some of the papers, revised and extended in response to the editors’ invitations, are versions of works presented at the Asian Conference on Design and Digital Engineering 2012 (Niseko, Japan) and 2013 (Seoul, Korea).
In addition, two well-organized review papers in this issue provide informative and comprehensive surveys of aesthetic curve and surface design in CAGD and knowledge structuring and logic reasoning in CAPP, respectively. They include rich lists of references which will help the readers to quickly gain an overview of the current status and future research directions of these fields.
Finally, the editors sincerely thank all the authors and anonymous reviewers for their devoted work, as they made this special issue possible. We expect that it will encourage further research on advanced CAD, CAM, CAE, CAPP, and digital engineering systems.
Aesthetic shapes are usually actualized as 3D objects represented by free-form surfaces. The main components used to achieve aesthetic surfaces are 2D and 3D curves, which are the elements most basic for determining the shapes and silhouettes of industrial products. Bézier, B-Spline and NURBS are types of flexible curves developed for various design intents. These curves, however produce complex curvature functions that may undermine the formulation of shape aesthetics. A viable solution to this problem is to formulate aesthetic curves and surfaces from well-defined curvatures to improve aesthetic design quality. This paper advocates formalizing aesthetic curve and surface theories to fill the gap mentioned above, which has existed since the 1970s. This paper begins by reviewing on fair curves and surfaces. It then extensively discusses on the technicalities of Log-Aesthetic (LA) curves and surfaces and touches on industrial design applications. These emerging LA curves have a high potential for being used as standards to generate, evaluate and reshape aesthetic curves and surfaces, thus revolutionizing efficiency in developing curve and shape aesthetics.
The need to integrate the design and machining stages has become an important issue since the introduction of the Computer-Integrated Manufacturing (CIM) concept. The development of the Computer-Aided Process Planning (CAPP) system has been recognized to have made a significant contribution toward fulfilling the requirement for an integrated planning system. This paper reviews the development of the CAPP system, particularly for the metal removal process. Previous reviews on CAPP are gathered and discussed to show the evolution stage of CAPP in general. Main research topics that contribute to the CAPP system development are shown. Six elements of the CAPP system are identified as the most important tasks in generating a process plan. These elements consist of: (1) model convention, (2) manufacturing operation selection, (3) manufacturing resource selection, (4) cutting condition selection, (5) tool path selection, and (6) setup selection. Six elements for the development of CAPP that contribute to process planning for metal removal process are discussed. The evolution stages of each element easily show the involvement of several tools in order to support the corresponding element. For further guidance, the methods of comprehending the involvement of manufacturing information in CAPP are discussed. Knowledge structuring and logic reasoning are the main organizational steps that can be used to describe the CAPP data architecture of manufacturing information. Further, the examples of full-scale CAPP in actualizing machining process planning are presented. Finally, key technologies for future development of CAPP are discussed.
Design that ensures robust performance for diverse users and environments has received much attention. Previous research proposed a Robust Design Method (RDM) that considered the adjustable control factors (ACFs) of mechanisms such as the servo mechanisms of machine tools or recliner mechanisms of public seats. This method derived the optimum adjustment ranges of the ACFs only after both these factors and their (dependent or independent) relationships had been identified in the design problem. This research improves on the previous RDM to enable designers to select ACFs and their relationships. This method contains two indices. One is the standard deviation of each control factor, used for finding ACFs that need not be adjusted. The other is the contribution ratio of the eigenvalues calculated from the variance-covariance matrix of the ACFs, used for finding dependent relationships. This method effectively derives the optimum adjustment ranges of the ACFs and their relationships based on these indices. Numerical and design examples are presented to demonstrate the practicality of the proposed method.
Model-based development is a potential approach to designing complicated mechatronic systems. This paper proposes a product design framework for mechatronic systems, which integrates model-based development with prototyping and focuses on its process of deployment with hypothesis and verification. SysML is adopted as the modeling language for representing the mechatronic system without depending on specific domains, and FMEA is adopted as the method for describing the results of validation by prototyping. The DRIFT framework is used to capture designer’s operations on the design tools of SysML and FMEA and to manage its process. This study defines design concepts and design operations that are extracted from the patterns embedded in design process with SysML and FMEA. A design example of a ball-sorting robot is created using LEGO Mindstorms to demonstrate the proposed framework.
Because performance testing using actual products is costly, manufacturers use lower-cost Computer-Aided Design (CAD) simulations. In this paper, we focus on hexahedral meshes, which are more accurate than tetrahedral meshes, for finite element analysis. Our final objective is automatic hexahedral mesh generation with sharp features to precisely represent the corresponding features of a target shape. Our hexahedral mesh is generated using a voxel-based algorithm. In our previous works, we fitted the surface of the voxels to the target surface using Laplacian energy minimization and used normal vectors in the fitting to preserve sharp features. However, we were unable to precisely represent sharp concave features using the method. In this proposal, we improve the previously used Laplacian energy minimization by adding a term that depends on facet normal matching for multi-normal vectors, instead of using normal vector matching.
Foam shock-absorbing structures such as cushioned packages are often utilized to protect various products from mechanical shock and vibration during transportation. The goal of packaging design engineers is to design a cushioned package structure that improves the shock-absorbing performance and minimizes the volume of the package. Some optimization techniques, combined with computational simulation, provide engineers with a way to design an optimal structure. In this paper, we propose a modified topology optimization method suitable for a polymeric foam shock-absorbing structure under dynamic drop loads in multiple directions. Our approach uses a heuristic topology optimization method, known as the Hybrid Cellular Automata (HCA). The HCA algorithm uniformly distributes internal energy density and controls the relative density of Cellular Automata (CAs) making up the design space. This allows the algorithm to maintain or increase the performance of shock absorption and to decrease the amount of material. In particular, this paper presents a modified Solid Isotropic Material with Penalization (SIMP) model for foam materials, which parameterizes the design region and interpolates the material properties. We attempt to optimize a simple bottom-cushioned package for a refrigerator by using the proposed foam SIMP model with commercial software: LS-DYNA for drop dynamic simulation and LS-OPT/Topology for the HCA algorithm. Drop simulation and topology optimization are performed considering multiple drop-directions. As a result, our method removes elements that are not related to the shock-absorption performance and provide an optimal cushioning structure using foam material.
In this paper, we propose a new method of reconstructing hand models for individuals including link structure models, homologous skin surface models and homologous tetrahedral mesh models in a reference posture. The skin surface model is defined as a three-dimensional triangular mesh, obtained by deforming a template mesh so as to fit the landmark vertices to the corresponding marker positions obtained by a motion capture system. In this process, anatomical dimensions for the subject, manually measured by a caliper, are also used as the deformation constraints. As for the link structure model, the local coordinate system related to each link consists of the joint rotation center and the axes of joint rotation, which can be estimated based on the deformation of the skin surface of the template model relative to the one of the individual. By using obtained individual hand model, hand postures in a motion sequence are also reconstructed based on the landmark points and the corresponding marker positions obtained from the motion capture system. Virtual spring-damper models located between the landmarks and the markers are used in physically-based simulation for the posture reconstruction.
Annotations on Geometric Dimensioning and Tolerancing (GD&T), surface roughness, etc. are needed for machining or measuring. However, these annotations are not used for the digital format in the product development process, nor is there any clear, explicit relationship between annotation, machining information, and measuring results. In this research, an integrated information model for design, machining, and measuring based on annotated features is proposed. A model for surface texture is also proposed because surface texture parameters are closely related to machining process parameters. A modeling system for the proposed integrated model is also implemented.
Process planning plays an important role as a bridge between product design and manufacturing. Computer-aided process planning (CAPP) has been a topic of discussion in this half century. The recent diversification in customers’ needs has been driving the development of agile manufacturing that can adapt to different manufacturing situations. CAPP should also be discussed from this point of view and, to this end, a set of flexible process planning methods have been proposed. Unlike conventional CAPP methods, these methods first generate all the feasible process plans. These are then evaluated, and then an optimal plan is selected. Therefore, it is possible to quickly provide an optimal new plan in the event of a change in the situation, by re-evaluating the plans against the new situation. However, these methods generally involve a large computational load, since the full search approach is taken to select an optimal plan. This study set out to reduce the computational load by formulating the selection process as a 0-1 integer programming problem that can now be solved thanks to recent developments in computer technology and solvers. Case studies have proven the efficacy of this method.
With the fast growth of the market for MEMS (Micro-Electro-Mechanical Systems) devices, Computer-Aided Design (CAD) and Computer-Aided Process Planning (CAPP) systems for MEMS are essential for the appropriate division of labor between MEMS design and fabrication. Although several CAD systems for MEMS devices are commercially available, CAPP systems for MEMS are still underdeveloped, and few systems have been investigated. The purpose of this study is to prototype a CAPP system for MEMS for non-expert MEMS designers. MEMS device geometry, a complex layered structure made of multiple materials, is represented as a solid model called a device model. The system has two main functions. In process-extraction function, all feasible fabrication processes of the device are exhaustively derived from the device model using 3D fabrication features as clues. In manufacturable-geometry-estimation function, the expected 3D geometry of the device that will actually be fabricated by the derived process, which might differ from the original device model, is estimated. Process emulation using a commercial emulator and examination by expert researchers confirm that the derived process plans and the expected 3D geometries of the device are feasible and plausible.
This study proposes a new method of estimating tool posture in 3+2-axis control machining process. The proposed method focuses on two different properties of the workpiece surface, the machinable area and then minimum shank length. The distribution of these properties on the workpiece surface is determined by the tool posture, workpiece shape, and the shape of the cutting tool. In the planning process of 3+2-axis control machining, CAM and CAPP operators often determine the combination of tool posture and tooling conditions through trial and error. Considering these processes, it would be extremely useful to have a fast method of visualizing these properties on the workpiece surface to realize CAM and CAPP systems with an interactive interface. Therefore, this study proposes a fast estimation method that visualizes both the machinable area and the distribution of the minimum shank length as a color image for each tool posture candidate. In order to reduce the calculation time of the proposed methods, a graphics device known as a Graphics Processing Unit (GPU) is introduced. In the proposed algorithm to adapt several features to GPU hardware, the offset shape of the workpiece surface is generated from depth information in rendering 3D-CG. Furthermore, the unmachinable area is estimated by the inverse-offset operation and shadow mapping function in 3D-CG techniques. In the visualization phase of the required shank length on the workpiece surface, a color image is generated from the depth information. Then, the color image is projected on the workpiece shape using the texture projection technique. Because most calculation processes can be executed inside the GPU hardware, the developed prototype system can visualize both the unmachinable area and the distribution of minimum shank length within several dozen milliseconds for each tool posture candidate.
Along with the increasing need for multi-axis and multi-tasking machining tools for the machining of complex free surfaces, the importance of CAM applications related to the accuracy of the free surfaces has increased dramatically. The machining accuracy and surface integrity of a product depends not only on the performance of the machining tool itself but also on the tool path generated by CAM. At present, there is a trade off between numerical calculation errors and cost in CAM. There is no calculation method that satisfies both sides. Of particular importance is the fact that the cost increases exponentially with the rank of the free surface. Therefore, this paper proposes a new method of generating tool paths efficiently; it generates tool paths directly from 2-dimensional parametric space by using the parametric surface defined as a polynomial. We confirm that this method can reduce the cost and that the tool path can be generated by means of a simple calculation process, without considering singular points. Moreover, since commercial CAM kernels cannot accommodate to our method, we design and implement a new CAM kernel that can access the parametric surface directly in order to develop this method.
In the field of machining processes, three-Dimensional (3D) models are commonly used to simulate the motions of cutting tools and workpieces. However, it is difficult for 3D models to represent spatio-temporal changes in their shapes continuously and to a high degree of accuracy. The objective of this study is to represent the 5-axis cutting process of workpiece transformation explicitly using a spatio-temporal model, the “four-Dimensional (4D) mesh model.” Every 4D mesh model is defined with bounding tetrahedral cells, and can continuously represent spatio-temporal changes of shape, position and orientation. In this study, the five-axis cutting process is described using accumulated volumes of 4D mesh models. Accumulated volumes are total volumes determined by spaces through which the object has passed. The use of accumulated volumes enables us to record tool-swept volumes and material removal shapes. First, this report introduces a 4D mesh model and the development of a 4D mesh modeling system. Next, a method of representing accumulated volumes as 4D mesh models is proposed. Generated 4D models are observed as 3D models by means of cross-section extraction.
This study aims to develop a turning system that uses a haptic device as a new operation interface to enable even beginners to operate a turning machine easily and safely. The haptic device is important because it can provide the user with sensations of physical force, such as shocks or vibrations, in the virtual space. These sensations of force function to guide the operator to suitable operation by limiting tool movement. In this study, a system is developed to teach, using the haptic device, the tool movements in machining shapes in a virtual space. The tool movement that is taught is output as the movement of turning machine, and the actual machining is performed. In the our system, we have implemented a function that avoids interference between the tool and workpiece and limits the depth of cut in order to avoid excessive cutting. The usefulness of developed system is confirmed through machining experiments.
This paper describes a remote controlled assembly using a haptic device. Most haptic devices have six Degrees Of Freedom (DOFs) for a higher sense of reality. However, for assembly operation, the simultaneous motion of parts with only one or two DOFs is required, and force feedback to operators is used only to maintain contact and detect collisions among parts. This leads to the possibility of assembly operations using a haptic device with a small number of DOFs. In this paper, we propose virtual planes to perform remote control of a 6DOF assembly by way of 1DOF user operations. Virtual planes separate the DOFs for user operation and for automatically generated motions that complement the user operation DOF in each assembly operation. A prototype system was developed with a 6DOF manipulator and camera. The system allows an operator to place virtual planes in any position and orientation using a camera image of the workspace. The experiment results showed the effectiveness of the method for remote controlled assembly without geometry information on the parts.
It is well kown that the wire electrode is flexible and will lead to a big lag in wire EDM machining, especially in the middle area of the work-piece. Methods to measure the wire deflection when it passes through the work-piece are studied in this paper. It is found that there is discharge spark first at the upper and lower parts of the wire when it cuts to the edge of the work-piece. The discharge spark appears at the middle of the work-piece a few seconds later. Based on this result, a method coined Camera Picture Analysis (CPA) is proposed to estimate the wire deflection. Another method of cross section measurement by the CCD is proposed to make a cross reference with the CPA method. By applying these two methods, the wire deflection models can be established, and used for the corner cut control of wire-cut EDM to improve accuracy of the machined parts.
This paper presents a novel pulse discriminating and control system for the identification of spark gap states, process monitoring and control of Wire Electrical Discharge Turning (WEDT). The relation between the proportion of open circuit, normal spark, arc discharge, short circuit to total sparks (defined as open circuit ratio, normal spark ratio, arc discharge ratio and short circuit ratio, respectively), ignition delay time and metal removal rate were experimentally studied and analyzed. A fuzzy logic controller was proposed to control both the arc discharge ratio and ignition delay time at optimal levels by on-line regulation of table feed-rate and pulse off-time for adaptive control optimization of WEDT. Experimental results show that the developed process monitoring and control system results in faster machining and better machining stability as compared with a conventional servo feed control scheme for the WEDT process.
Grinding is one of the machining processes used in the manufacture of high-accuracy parts. When materials which easily adhere to the grinding wheel are used, such as aluminum, stainless steel, and titanium, wheel loading must be considered, as this could have a limiting effect. In this research, the application of ultrasonic energy to the grinding fluid is carried out with a specially-designed effector inserted into the fluid supply flow with the expectation that loading will be removed from the wheel. The experiment is carried out on stainless steel and pure titanium. The grinding force and accession of temperature are investigated during grinding, and the reduction of both grinding force and thermal escalation is confirmed. Burn marks on the ground surface of titanium are also prevented.
In structured light 3D vision measurement system, calibration tasks are key steps. Aiming at a special application of line structured light measurement, namely computer hard-disk surface planeness measurement at a precision equipment manufacturing company in Singapore, and combining with the structured light measurement model, determined three calibration tasks of the system. The three calibrating tasks concluded: calibrating the camera parameters; calibrating the light plane pose and calibrating the movement pose. At the same time, according to the three calibration results, measured the computer hard disk, and reconstructed the 3D model of the computer hard disk. The experimental results show that, the whole system of three calibration process is simple and reliable, the method does not need any auxiliary adjustment and realize the measurement accuracy about 0.023 mm. The work laid the better foundation for hard disk planeness vision measurement.
In welfare facilities, although wheelchairs are commonly used for transferring patients, there are many cases in which patients are transferred while lying on beds because it is burdensome for caregivers to move a patient from a bed to a wheelchair. However, the task of moving a bed with a patient lying on it is still physically burdensome for caregivers. Hence in this study, we developed a power-assist omni-directional mobile bed to reduce the burden associated with this task. This paper reports a novel prototype of the omni- directional power-assist bed and describes the prototype’s design, mechanism and control-system configuration. In addition, we report on experiments that were conducted to verify the effectiveness and usefulness of the omni-directional mobile bed, as well as the adaptability of the omni-directional power-assist system.