Abstract
An automatic tool-changing system (ATCS) is one of the key sub-systems for realizing automatic tool changing in machining centers. Each step in a tool-changing cycle tends to result in ...impacts, and thus generates transients in the vibration signal. The impact features often reflect important operational information related to the ATCS dynamics, and a crucial problem for impact-feature extraction is how to effectively represent the transients. A novel method for extracting impact features from an ATCS is proposed, based on sparse representation theory. A parametric multiple-impulse dictionary is constructed by the unit impulse-response function of a damped multiple-degree-of-freedom system, whose modal order, amplitudes, natural frequencies, relative damping ratios and initial phases are directly identified from the vibration signal by an improved state-space method. This leads to high similarity between atoms and impact-induced transients. To improve the calculation speed, a split augmented Lagrangian shrinkage method is used to obtain optimal sparse coefficients. With the proposed method, both the moments of impact occurrence and the time intervals between transients can be effectively identified, and thus the impact features can be extracted. The effectiveness of the proposed method is validated by simulated signals as well as practical ATCS vibration signals. A comparison study shows that the proposed method is superior to empirical-mode decomposition, ensemble-empirical-mode decomposition and variational-mode decomposition when used for impact-feature extraction.
Determining the optimum cutting tool positions in a tool magazine is a challenging task which involves a huge searching space. Reduction of manufacturing time even by nanoseconds will highly be ...beneficial for all process industries. The prime focus of this research work is to reduce the total turret or tool indexing time in Automatic Tool Changer (ATC) which in turn curtails the idle non-cutting time of the bi-directional turret or tool magazine in a CNC machine. This variant of optimization problem falls under the category of non-deterministic hard polynomial (NP-hard) problem. Chemical Reaction Optimization (CRO) algorithm is proposed to determine the near optimal/global optimal solution with lesser computational cost. Five benchmark case studies are considered in this work to assess the robustness of the proposed algorithm. From the results, it is evident that the proposed algorithm yields solutions which matches or exceeds with the solution quality.
Automatic tool changer system (ATCS) and drawbar mechanism (DM) are two of key basic parts for realizing the automatic tool-changing cycle in machining centers. The dynamic force in a tool-changing ...cycle plays an essential role in condition monitoring, fault diagnosis, and failure warning for the ATCS and DM. However, existing force detection systems have limitations in practical application. In this paper, a novel dynamic force measurement system (DFMS) is developed, which is based on a force sensing element installed on the BT40 tool holder and operating through a wireless network. The force sensing element is used to convert the dynamic force into the electrical signal. Digital measurements are collected from the 24-bit sigma-delta analog-to-digital converter with a programmable gain array, which then are transmitted to the upper computer software via a wireless transceiver. Besides, a Teager energy operator based dual-threshold two sentences endpoint detection method is proposed to recognize the temporal onset and offset of each force event in the dynamic force recording. Experimental results show that the DFMS is reliable and suitable to measure the dynamic force in automatic tool-changing cycles.
A significant shift from traditional lines to reconfigurable and reprogrammable robotic cells has occurred in Industry 4.0. Collaborative robots can be used for automating several tasks for improving ...Human-Machine Interface (HMI). The ability of a robot carrying out different tasks is proportional to the tools that it can use, thus it is crucial that robots are equipped with systems enabling efficient tool changing. Therefore, in this paper an automatic tool changer system is proposed. Based on Finite Element Analysis (FEA) of the design and the specifications, a 3D printed prototype was made and tested on a UR 10 Collaborative Robot.
•A condition monitoring system is constructed for the automatic tool changer.•The sparsity-enabled signal decomposition method is introduced for fault localization.•The abnormal components are ...selected to calculate fault feature for condition assessment.•The constructed condition monitoring system is verified by experimental application.
Automatic tool changer (ATC) is one of the key basic parts in CNC machining centers, and the globoidal indexing cam and the groove cam are the functional units for tool changing. Thus the condition monitoring is important for highly efficient and precision machining. In this paper, a condition monitoring system is constructed for the ATC, especially for the globoidal indexing cam, including vibration signal acquisition, fault feature extraction and localization, and condition assessment. In the constructed system, sparsity-enabled signal decomposition method is introduced to extract transient component and reduce noises in the complex vibration signals, and the transient component is always a key feature for fault localization. Simulation study shows that the sparsity-enabled signal decomposition method is effective in transient feature extraction. The experimental application in condition assessment for the ATC demonstrates that the constructed condition monitoring system has the potential to assess the working condition of the ATC in practical application.
The tool indexing problem (TIP) is the problem of allocating cutting tools to different slots in a tool magazine of Computer Numerically Controlled machine to reduce the processing time of jobs on ...the machine. This is one of the mostly encountered optimization problems in manufacturing systems. In TIP, the number of tools used by the machine is at most the number of slots available in the tool magazine. In this article, a customized harmony search (HS) algorithm, which utilizes a harmony refinement strategy for faster convergence, is presented to solve TIP. The harmony refinement method also helps to avoid getting stuck into local optima. The performance of the proposed method is tested on 27 instances taken from the literature and out of these it is found to improve the best known solutions for 16 instances. For the remaining instances, it gives the same results as found in the literature. Moreover, the performance of the proposed algorithm is tested on newly adapted 41 instances and for some of these instances the results obtained using the proposed algorithm are compared with that obtained using CPLEX.
A tool magazine and automatic tool changer is used to store and change tools in a machining center. Its failures would increase the maintenance time and repair cost. For decreasing failures, an early ...warning system of failures can be used to detect characteristic signals which can reflect potential failures. The tool-pulling force is increasing to peak value instantly when the tool changing arm draws a tool holder out of a tool pocket. To predict failures, the tool-pulling force signals are analyzed and the relationship between the maximum tool-pulling force and the severity of the lock spring failure is established, then, calculation method of the tool-pulling force threshold of the lock spring failure which can lead to tool falling failures is developed and demonstrated. The verification testing results show that the failure warning method based on the tool-pulling force threshold is feasible to predict the tool falling failures.
Purpose
This paper aims to propose an elementary approach towards the measurement of a globoidal cam profile used in an automatic tool changer (ATC) of computer numerical control (CNC) machines.
...Design/methodology/approach
A simple and unique online method has been designed for the profile metrology of the cam. This simple methodology will replace the traditional methodology of profile metrology of cam by coordinate measuring machine (CMM). A globoidal cam with an indexable turret and roller follower (rotating in an enclosed track) has been evaluated in our analysis. This analysis plays a significant role in the performance determination of the cam as well as the ATC of CNC machines.
Findings
A novel model has been designed and implemented to investigate the profile of a globoidal cam. The proposed methodology becomes an enhancement over the old methodology, i.e. measurement through CMM. Theoretical analysis and practical implementation prove the significance of the method.
Originality/value
An enhanced methodology to effectively measure the globoidal cam profile has been proposed. The practical implication of the proposed methodology remains for the CNC machine tool and ATC manufacturers. Finally, analytical explorations have been carried out to prove the validity of the proposal.
This research aims to propose an innovative smart system we developed for early failure detection of Automatic Tool Change (ATC) systems. Input data is the system's tool magazine door open/close ...signals. Then, 41 indicators from 26 machines are obtained from statistics-based feature extraction methods. Under the guidance of predefined risk levels, nine high-ranking top level indicators are selected using correlation and regression analysis. In addition, some lightweight supervised learning algorithms are used to build and train the model to solve the classification problem of the system states, such as Normal, Caution, and Danger. The experimental results confirm that the high-ranking indicators can achieve the most prominent and stable performance under a series of tests. Under 10-fold cross-validation, the average accuracy is 89.43 %, which is 19~38 % higher than those of other feature groups. Among them, the Naive Bayes algorithm obtains the best accuracy of 94.2 %. This proves that the proposed smart system can effectively grasp the health status of the ATC systems.
Aiming at the problems of the work profile of globoidal cam in automatic tool changer（ ATC） is difficult to design,manufacture and both side of cam groove meshing with the roller in indexing ...period,taking the globoidal cam of a certain machining center as example,the motion and position relationship between globoidal cam and indexing plate are analyzed,the mathematical equation of globoidal cam contour surface is derived and modified. By using the segment modeling method,the cam profile curve groups in both indexing period and dwell period are created in Pro/E software. By the physical modeling of line and surface,the accurate 3D solid model of the globoidal cam is established. After globoidal cam profile performance analysis and machining practice,the designed globoidal cam model is verified to meet the design and machining requirements,which provides technical support for improving its finish grinding accuracy.
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