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Guest Editorial

J. Manuf. Sci. Eng. 2017;139(10):100301-100301-1. doi:10.1115/1.4037737.
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GE described in a 2012 white paper how manufacturing companies have been collecting a massive amount of data about the production processes and operating conditions from a variety of manufacturing machines, devices, and applications. For example, a consumer packaged goods (CPG) company can collect over 13 billion data samples per day, and data volumes are trending higher. In addition to large data volumes, increasing variety, complexity, and uncertainty have also contributed to the increasing and ubiquitous challenge posed by data. Deeply embedded in the data is temporal and spatial information that underlies the physical mechanisms used to make a product. Therefore, effective extraction and use of information embedded in the data have become the next frontier to drive innovation, competitiveness, and growth in manufacturing, as highlighted by McKinsey in a series of studies.

Topics: Manufacturing
Commentary by Dr. Valentin Fuster

Research Papers

J. Manuf. Sci. Eng. 2017;139(10):101001-101001-13. doi:10.1115/1.4037319.

The goal of this work is to minimize geometric inaccuracies in parts printed using a fused filament fabrication (FFF) additive manufacturing (AM) process by optimizing the process parameters settings. This is a challenging proposition, because it is often difficult to satisfy the various specified geometric accuracy requirements by using the process parameters as the controlling factor. To overcome this challenge, the objective of this work is to develop and apply a multi-objective optimization approach to find the process parameters minimizing the overall geometric inaccuracies by balancing multiple requirements. The central hypothesis is that formulating such a multi-objective optimization problem as a series of simpler single-objective problems leads to optimal process conditions minimizing the overall geometric inaccuracy of AM parts with fewer trials compared to the traditional design of experiments (DOE) approaches. The proposed multi-objective accelerated process optimization (m-APO) method accelerates the optimization process by jointly solving the subproblems in a systematic manner. The m-APO maps and scales experimental data from previous subproblems to guide remaining subproblems that improve the solutions while reducing the number of experiments required. The presented hypothesis is tested with experimental data from the FFF AM process; the m-APO reduces the number of FFF trials by 20% for obtaining parts with the least geometric inaccuracies compared to full factorial DOE method. Furthermore, a series of studies conducted on synthetic responses affirmed the effectiveness of the proposed m-APO approach in more challenging scenarios evocative of large and nonconvex objective spaces. This outcome directly leads to minimization of expensive experimental trials in AM.

Commentary by Dr. Valentin Fuster
J. Manuf. Sci. Eng. 2017;139(10):101002-101002-11. doi:10.1115/1.4036347.

Fine-scale characterization and monitoring of spatiotemporal processes are crucial for high-performance quality control of manufacturing processes, such as ultrasonic metal welding and high-precision machining. However, it is generally expensive to acquire high-resolution spatiotemporal data in manufacturing due to the high cost of the three-dimensional (3D) measurement system or the time-consuming measurement process. In this paper, we develop a novel dynamic sampling design algorithm to cost-effectively characterize spatiotemporal processes in manufacturing. A spatiotemporal state-space model and Kalman filter are used to predictively determine the measurement locations using a criterion considering both the prediction performance and the measurement cost. The determination of measurement locations is formulated as a binary integer programming problem, and genetic algorithm (GA) is applied for searching the optimal design. In addition, a new test statistic is proposed to monitor and update the surface progression rate. Both simulated and real-world spatiotemporal data are used to demonstrate the effectiveness of the proposed method.

Commentary by Dr. Valentin Fuster
J. Manuf. Sci. Eng. 2017;139(10):101003-101003-11. doi:10.1115/1.4036787.

In resistance spot welding (RSW), data inconsistency is a well-known issue. Such inconsistent data are usually treated as noise and removed from the original dataset before conducting analyses or constructing prediction models. This may not be desirable for all design and manufacturing applications since data that are often considered noise can contain important information in determining weldment design, and proper welding conditions. In this paper, we present the Meta2 prediction framework to provide cost-effective opportunities for proper welding material and condition selection from the noisy RSW quality data. The Meta2 framework employs bootstrap aggregating with support vector regression (SVR) to improve the prediction accuracy on the noisy RSW data with computational efficiency. Hyper-parameters for SVR are selected by particle swarm optimization (PSO) with meta-modeling to reduce the computational cost. Experiments on three artificially generated noisy datasets and a real RSW dataset indicate that Meta2 is capable of providing satisfactory solutions with a noticeably reduced computational cost. The authors find Meta2 promising as a potential prediction model algorithm for this type of noisy data.

Commentary by Dr. Valentin Fuster
J. Manuf. Sci. Eng. 2017;139(10):101004-101004-10. doi:10.1115/1.4037106.

Fixture layout can affect deformation and dimensional variation of sheet metal assemblies. Conventionally, the assembly dimensions are simulated with a quantity of finite element (FE) analyses, and fixture layout optimization needs significant user intervention and unaffordable iterations of finite element analyses. This paper therefore proposes a fully automated and efficient method of fixture layout optimization based on the combination of 3dcs simulation (for dimensional analyses) and global optimization algorithms. In this paper, two global algorithms are proposed to optimize fixture locator points, which are social radiation algorithm (SRA) and GAOT, a genetic algorithm (GA) in optimization toolbox in matlab. The flowchart of fixture design includes the following steps: (1) The locating points, the key elements of a fixture layout, are selected from a much smaller candidate pool thanks to our proposed manufacturing constraints based filtering methods and thus the computational efficiency is greatly improved. (2) The two global optimization algorithms are edited to be used to optimize fixture schemes based on matlab. (3) Since matlab macrocommands of 3dcs have been developed to calculate assembly dimensions, the optimization process is fully automated. A case study of inner hood is applied to demonstrate the proposed method. The results show that the GAOT algorithm is more suitable than SRA for generating the optimal fixture layout with excellent efficiency for engineering applications.

Commentary by Dr. Valentin Fuster
J. Manuf. Sci. Eng. 2017;139(10):101005-101005-13. doi:10.1115/1.4036993.

Vibration signal analysis has been proved as an effective tool for condition monitoring and fault diagnosis for rotating machines in the manufacturing process. The presence of the rub-impact fault in rotor systems results in vibration signals with fast-oscillating periodic instantaneous frequency (IF). In this paper, a novel method for rotor rub-impact fault diagnosis based on nonlinear squeezing time-frequency (TF) transform (NSquTFT) is proposed. First, a dynamic model of rub-impact rotor system is investigated to quantitatively reveal the periodic oscillation behavior of the IF of vibration signals. Second, the theoretical analysis for the NSquTFT is conducted to prove that the NSquTFT is suitable for signals with fast-varying IF, and the method for rotor rub-impact fault diagnosis based on the NSquTFT is presented. Through a dynamic simulation signal, the effectiveness of the NSquTFT in extracting the fast-oscillating periodic IF is verified. The proposed method is then applied to analyze an experimental vibration signal collected from a test rig and a practical vibration signal collected from a dual-rotor turbofan engine for rotor rub-impact fault diagnosis. Comparisons are conducted throughout to evaluate the effectiveness of the proposed method by using Hilbert–Huang transform, wavelet-based synchrosqueezing transform (SST), and other methods. The application and comparison results show that the fast-oscillating periodic IF of the vibration signals caused by rotor rub-impact faults can be better extracted by the proposed method.

Commentary by Dr. Valentin Fuster
J. Manuf. Sci. Eng. 2017;139(10):101006-101006-12. doi:10.1115/1.4037419.

Machinery condition monitoring and fault diagnosis are essential for early detection of equipment malfunctions or failures, which insure productivity, quality, and safety in the manufacturing process. This paper aims at extracting fault features of rolling element bearings at the incipient fault stage. K-singular value decomposition (K-SVD), one technique for sparse representation of signals, is used for study. In K-SVD, its dictionary is trained from data by machine learning techniques, which allows more flexibility to adapt to variation of real signals than the predefined dictionaries. Analysis on simulated bearing signals and real signals shows that K-SVD can give better bearing fault features than the predefined dictionaries such as wavelet dictionaries. However, during our simulation study, K-SVD was found to have large representation error under heavy noise. To reduce the noise effect, minimum entropy deconvolution (MED) is used as a prefilter. The combination of MED and K-SVD is proposed for incipient bearing fault detection. The method is verified by simulation and experimental study. It is shown that the proposed method can effectively extract the impulsive fault feature of the tested bearing at its incipient fault stage.

Commentary by Dr. Valentin Fuster
J. Manuf. Sci. Eng. 2017;139(10):101007-101007-11. doi:10.1115/1.4037234.

Real-time algorithms are needed to compare and analyze digital videos of machines and processes. New video analysis techniques, for computationally efficient dimensionality-reduction, for determination of accurate motion-information, and for fast video comparison, will enable new approaches to system monitoring and control. We define the video alignment path (VAP) as the sequence of local time-and-space transformations required to optimally register two video clips. We develop an algorithm, dynamic time and space warping (DTSW), which calculates the VAP. Measures of video similarity, and therefore system similarity, are estimated based on properties of the VAP. These measures of similarity are then monitored over time and used for decision-making and process control. We describe the performance, structure, and computational complexity of a DTSW implementation, which is parallelizable and which can achieve the processing rates necessary for many video-based industrial monitoring applications. We describe two case studies of unsupervised monitoring for mechanical wear and for fault detection. Results suggest opportunities for boarder applications of video-based instrumentation for real-time feedback control, wear and defect detection, or statistical process control.

Commentary by Dr. Valentin Fuster
J. Manuf. Sci. Eng. 2017;139(10):101008-101008-8. doi:10.1115/1.4036907.

Multisensor data fusion can enable comprehensive representation of manufacturing processes, thereby contributing to improved part quality control. The effectiveness of data fusion depends on the nature of the input data. This paper investigates orthogonality as a measure for the effectiveness of data fusion, with the goal to maximize data correlation with part quality toward manufacturing process control. By decomposing sensor data into a lifted-dimensional space, contribution from each of the sensors for quantifying part quality is revealed by the corresponding projection vector. Performance evaluation using data measured from polymer injection molding confirmed the effectiveness of the developed technique.

Commentary by Dr. Valentin Fuster
J. Manuf. Sci. Eng. 2017;139(10):101009-101009-12. doi:10.1115/1.4036833.

Discussion of big data (BD) has been about data, software, and methods with an emphasis on retail and personalization of services and products. Big data also has impacted engineering and manufacturing and has resulted in better and more efficient manufacturing operations, improved quality, and more personalized products. A less apparent effect is that big data have changed problem solving: the problems we choose to solve, the strategy we seek, and the tools we employ. This paper illustrates this point by showing how the big data style of thinking enabled the development of a new quality assurance philosophy called process monitoring for quality (PMQ). PMQ is a blend of process monitoring and quality control (QC) that is founded on big data and big model (BDBM), which are catalysts for the next step in the evolution of the quality movement. Process monitoring (PM) for quality was used to evaluate the performance of the ultrasonically welded battery tabs in the new Chevrolet Volt, an extended range electric vehicle.

Commentary by Dr. Valentin Fuster
J. Manuf. Sci. Eng. 2017;139(10):101010-101010-13. doi:10.1115/1.4036660.

The goal of this research is online monitoring of functional electrical properties, e.g., resistance, of electronic devices made using aerosol jet printing (AJP) additive manufacturing (AM) process. In pursuit of this goal, the objective is to recover the cross-sectional profile of AJP-deposited electronic traces (called lines) through shape-from-shading (SfS) analysis of their online images. The aim is to use the SfS-derived cross-sectional profiles to predict the electrical resistance of the lines. An accurate characterization of the cross section is essential for monitoring the device resistance and other functional properties. For instance, as per Ohm’s law, the electrical resistance of a conductor is inversely proportional to its cross-sectional area (CSA). The central hypothesis is that the electrical resistance of an AJP-deposited line estimated online and in situ from its SfS-derived cross-sectional area is within 20% of its offline measurement. To test this hypothesis, silver nanoparticle lines were deposited using an Optomec AJ-300 printer at varying sheath gas flow rate (ShGFR) conditions. The four-point probes method, known as Kelvin sensing, was used to measure the resistance of the printed structures offline. Images of the lines were acquired online using a charge-coupled device (CCD) camera mounted coaxial to the deposition nozzle of the printer. To recover the cross-sectional profiles from the online images, three different SfS techniques were tested: Horn’s method, Pentland’s method, and Shah’s method. Optical profilometry was used to validate the SfS cross section estimates. Shah’s method was found to have the highest fidelity among the three SfS approaches tested. Line resistance was predicted as a function of ShGFR based on the SfS-estimates of line cross section using Shah’s method. The online SfS-derived line resistance was found to be within 20% of offline resistance measurements done using the Kelvin sensing technique.

Commentary by Dr. Valentin Fuster
J. Manuf. Sci. Eng. 2017;139(10):101011-101011-8. doi:10.1115/1.4037615.

This paper presents new techniques to analyze and understand the sensorimotor characteristics of manual operations such as grinding, and links their influence on process performance. A grinding task, though simple, requires the practitioner to combine elements from the large repertoire of his or her skillset. Based on the joint gaze, force, and velocity data collected from a series of manual grinding experiments, we have compared operators with different levels of experience and quantitatively described characteristics of human manual skill and their effects on manufacturing process parameters such as cutting energy, surface finish, and material removal rate (MRR). For instance, we find that an experienced subject performs the task in a precise manner by moving the tool in complex paths, with lower applied forces and velocities, and short fixations compared to a novice. A detailed understanding of gaze-motor behavior broadens our knowledge of how a manual task is executed. Our results help to provide this extra insight, and impact future efforts in workforce training as well as the digitalization of manual expertise, thereby facilitating the transformation of raw data into product-specific knowledge.

Commentary by Dr. Valentin Fuster

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