International Journal of Advanced Manufacturing Technology, 2008
In this study, a Mahalanobis–Taguchi system (MTS)-based diagnostic and root cause analysis scheme... more In this study, a Mahalanobis–Taguchi system (MTS)-based diagnostic and root cause analysis scheme for monitoring grip length of pull-type fasteners in real-time is presented. The proposed approach is implemented on a fastening tool integrated with a strain gage, a linear variable differential transformer, a pressure sensor, and a mote for wireless communication. Experiments show that the process signature of strain-over-displacement ratio versus displacement has unique features that can be used to determine the grip length related deviations. The proposed approach takes as input various characteristics, such as peak strain, peak displacement, and depth and width of a bowl-shaped dip on the process signature in order to make real-time decisions. The experiments show that the proposed approach is effective in determining grip length deviations and in communicating the decision in real-time via a wireless network to a base station. Overall, the proposed architecture has merits to (1) detect quality problems in real-time during the fastening process and (2) reduce post-process inspection, thereby improving quality while reducing cost. In addition, the approach facilitates 100% data collection on each fastener as opposed to traditional statistical process control (SPC) techniques, which rely on sampling.
This paper presents a Mahalanobis-Taguchi System (MTS) based methodology that detects grip length... more This paper presents a Mahalanobis-Taguchi System (MTS) based methodology that detects grip length of bolted joints in real-time during fastening. Grip length is the length of the unthreaded portion of a bolt shaft. When the total thickness of joining members is greater than the grip length of the bolt, it is called under-grip, which compromises the structural integrity of a joint. In this study, a pneumatic, hand-held, rotary-type tool for bolted joints is integrated with a torque sensor and an optical encoder in order to obtain torque-angle signatures. Then, the signature is processed in real-time using the MTS-based approach in order to detect the grip-length, all of which occurs in real-time as the fastening process is completed. The proposed approach is also applied to detect the presence of re-used fasteners, which is another quality concern since some material properties and physical conditions of bolts and nuts can change if they are reused several times. The proposed approach reads in various characteristics from the torque-angle process signature, including mean and standard deviation of the torque-over-angle and angle-over-torque ratios, total angle turned, and work done during the different stages of the fastening process in order to infer about the quality of the bolted joint. The experimental results show that the proposed approach is successful with an accuracy of over 95% in detecting various grip lengths and presence of re-used fasteners.
International Journal of Advanced Manufacturing Technology, 2008
In this study, a Mahalanobis–Taguchi system (MTS)-based diagnostic and root cause analysis scheme... more In this study, a Mahalanobis–Taguchi system (MTS)-based diagnostic and root cause analysis scheme for monitoring grip length of pull-type fasteners in real-time is presented. The proposed approach is implemented on a fastening tool integrated with a strain gage, a linear variable differential transformer, a pressure sensor, and a mote for wireless communication. Experiments show that the process signature of strain-over-displacement ratio versus displacement has unique features that can be used to determine the grip length related deviations. The proposed approach takes as input various characteristics, such as peak strain, peak displacement, and depth and width of a bowl-shaped dip on the process signature in order to make real-time decisions. The experiments show that the proposed approach is effective in determining grip length deviations and in communicating the decision in real-time via a wireless network to a base station. Overall, the proposed architecture has merits to (1) detect quality problems in real-time during the fastening process and (2) reduce post-process inspection, thereby improving quality while reducing cost. In addition, the approach facilitates 100% data collection on each fastener as opposed to traditional statistical process control (SPC) techniques, which rely on sampling.
This paper presents a Mahalanobis-Taguchi System (MTS) based methodology that detects grip length... more This paper presents a Mahalanobis-Taguchi System (MTS) based methodology that detects grip length of bolted joints in real-time during fastening. Grip length is the length of the unthreaded portion of a bolt shaft. When the total thickness of joining members is greater than the grip length of the bolt, it is called under-grip, which compromises the structural integrity of a joint. In this study, a pneumatic, hand-held, rotary-type tool for bolted joints is integrated with a torque sensor and an optical encoder in order to obtain torque-angle signatures. Then, the signature is processed in real-time using the MTS-based approach in order to detect the grip-length, all of which occurs in real-time as the fastening process is completed. The proposed approach is also applied to detect the presence of re-used fasteners, which is another quality concern since some material properties and physical conditions of bolts and nuts can change if they are reused several times. The proposed approach reads in various characteristics from the torque-angle process signature, including mean and standard deviation of the torque-over-angle and angle-over-torque ratios, total angle turned, and work done during the different stages of the fastening process in order to infer about the quality of the bolted joint. The experimental results show that the proposed approach is successful with an accuracy of over 95% in detecting various grip lengths and presence of re-used fasteners.
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Papers by Deepak Mohan