Advances in Science and Technology Vol. 132

Abstract: This study presents a time domain simulation and workpiece surface generation framework for broaching operations, carried out with broaching tools of arbitrary geometry by machine tools of general dynamics. First, a three degree of freedom simulation model is formulated by considering an adequately discretized infinitely rigid tool, and a broaching machine, which is compliant in all translational spatial directions. Taking contact loss events into account, this leads to system a piecewise-smooth delay differential equations with state dependent delays, due to the allowed deviations in the speed of cutting. Through numeric integration of these equations, the dynamic displacement and cutting edge engagement of the broaching tool are evaluated, which serve as inputs for the developed surface generation routines. Then, a discretized workpiece surface is generated by finding the last active cutting edge, and its corresponding displacement for each point, allowing the numeric investigation of surface roughness and integrity through standardized techniques. Finally, to demonstrate the capabilities of the proposed framework, force and displacement signals as well as the generated surface and its virtual quality assessment are presented for a typical broaching operation.

Abstract: An analytical model of the cold wire drawing process is used to implement an optimization procedure. The optimization aims to minimize the number of passes required to achieve a given reduction while maintaining a safe value of the drawing stress in each step. The number of passes and the sequence of intermediate diameters are the output of the optimization model. The sequence of diameters is optimal in the sense that minimizes a mathematical objective function, and their values must be considered a first attempt to determine appropriate values for a specific wire drawing operation. With respect to prior contributions, the work hardening of the material is exploited to reduce the number of passes. The reduction of the number of passes yields lower values of the aspect ratio, defined as the mean diameter divided by the contact length, which is an important factor to prevent the onset of internal defects. The optimization is performed numerically with mathematical programming and metaheuristic algorithms.

Abstract: The aviation industry is changing significantly as market demands and customer expectations evolve. Aircraft must be designed and manufactured with a future-oriented production system that incorporates computational intelligence, connectivity, and decentralization to ensure the highest levels of quality and performance. By leveraging these technologies, real-time monitoring and continuous process improvement can be achieved through collecting and processing massive amounts of data, accompanied by more sophisticated communication protocols. Among the many operations involved in component assembly, drilling processes are particularly relevant in the aeronautical industry. When drilling airframe components, hybrid joints are generated by combining stacks of various materials, such as titanium and Carbon Fiber-Reinforced Plastic (CFRP). Due to the complexity of drilling these hybrid stacks and the need to adhere to strict quality and safety standards, the cost-per-hole can be pretty high. Consequently, scientific studies in this area are of great interest, as they offer the potential to increase productivity and reduce costs. This research aims to investigate using spindle power consumption signals obtained directly from an industrial drilling system to monitor tool wear evolution. Signal pre-processing, feature extraction, selection, and validation are used to analyze data from two sources: the spindle power consumption signals obtained from the internal instrumentation of the machine and the cutting tool. The study focuses on automatic drilling operations carried out in hybrid stacks at an aircraft manufacturing facility, and the results show a strong correlation between power consumption and tool wear. These findings suggest the potential to develop a non-intrusive tool condition monitoring system that could be applied to other machining processes in the industry.

Abstract: The aeronautical industry is at the forefront of the fourth industrial revolution, which implies an exponential deployment of monitorization, Data Analytics, and connectivity. In alignment with this new paradigm, this research work presents a Catastrophic Tool Failure (CTF) analysis based on spindle power consumption monitoring in an industrial aircraft fuselage drilling process. In the case under study, the airframe components are arranged in hybrid stacks of Carbon Fiber Reinforced Plastic (CFRP) and titanium (Ti6Al4V) during drilling, which adds to the highly variable industrial machining conditions. This inherent complexity can lead to CTF, a significant concern due to its associated cost and time, especially in automatic processes. Industrial CTF detection systems based on motor power consumption establish maximum and minimum power limits to detect tool breakage. However, these systems generate many false positives and false negatives due to process variability and unforeseen events. Therefore, an Exploratory Data Analysis (EDA) of the power spindle consumption signals and other machining-related features is proposed to gain insights into the breakage nature and develop more effective detection systems. This analysis is oriented to set the basis for real-time Catastrophic Tool Failure detection from power spindle consumption monitoring. As a result, advanced processing time-domain detection methods are proposed.

Abstract: The Automotive Industry is in constant evolution, thanks in part to its high level of production and customer demands for quality assurance. New processes, equipment and products are constantly emerging, leading to new vehicles launched to the public. These processes and equipment need adequate monitoring tools and forms of quality assurance, and it is the responsibility of the engineering department to look for economically viable and efficient ways of guaranteeing the quality of products in an industry where quality itself is considered one of its pillars. This work aims to develop and validate a solution for quality control in the automotive industry while taking full advantage of the technological factors provided by the equipment used. It deals with researching and applying a three-dimensions (3D) scanner in product quality monitoring tasks of a door panel manufacturing process. Pilot studies were carried out to assess the real capabilities of the equipment and determine problems that could arise when scaling the process for a real production of car door panels. The implementation and final results are also described in this work, showing that it is possible to develop a flexible equipment with multiple applications and apply it in the automotive industry.

Abstract: A low-cost method based on macro-photogrammetric reconstruction is presented to automatically detect wear and other defects in small gears created with additive manufacturing. This novel approach is oriented to preventive and predictive maintenance of gears in order to avoid faults in machines and devices. The experimentation has been conducted using three defective gears produced in Nylon PA-12. First, a robotic platform and a systematic macro-photogrammetric data acquisition procedure were used to accomplish the 3D reconstruction and generate the dense point clouds. Subsequently, a comparison between the dense point cloud and the ideal solid CAD model of the normalized gear has been carried out. For this aim, the models have been alignment in the same spatial system. The computation of the distances between solid models and point clouds allows the automatic visualization of different types of defects even for defects that are not visible to the naked eye. This conclusion has been checked from a statistical point of view considering the discrepancies obtained in the comparison and their distribution.

Abstract: Grinding is a widely used process in many industries due to the precise geometric tolerances and excellent surface finishes it can offer, which makes it very useful when high quality parts have to be manufactured. Due to the wear that the grinding wheel suffers, a process known as dressing is periodically carried out to recover the cutting ability of the wheel. Dressing is an extremely important part of the grinding process, as it can alter and improve the cutting conditions of the wheel.During the dressing of vitrified bonded CBN wheels, the real dressing depth of cut is significantly lower than the theoretical depth of cut, leading to dimensional errors in the dressed grinding wheel, which consequently translate into the ground part. However, while deformations during grinding have been widely studied, this phenomenon has not been yet analyzed during dressing. Therefore, the main objective of this work is to determine the influence of the dressing parameters on the real depth of cut. Also, the effect of dresser wear and the deformations has been determined separately.To this end, a new methodology has been developed to measure the real depth of cut using a laser displacement sensor. Moreover, experimental tests have been carried out to characterize the influence that the dressing speed ratio (q_d) and set depth of cut (a_{d_set}) have on the actual depth of cut (a_{d_real}). It has been seen that the use of negative q_d results in a more accurate real depth of cut, and therefore a more efficient dressing process. While the error using negative q_d is about 10 %, using positive q_d is about 25 %.

Abstract: The main goal of production quality paradigm is a joint improvement of production rate and conformity, while minimizing the waste of resources. This paradigm is aligned with the Zero-Defect Manufacturing (ZDM) approach, which aim is the defect removal in manufactured products. Simulation tools offer a high flexibility to analyse complex systems such as multi-stage manufacturing systems, allowing to optimize the required production rates and the quality of the products. To this end it is necessary to develop simulation models that integrate the discrete behaviour of products flow, and the spread of quality characteristics during the process. This work is focused on the modelling of the geometrical quality characteristics that depend on the deviations induced when the part is held by a processing fixture. For the modelling of this behaviour, Modelica language is selected because of its ability to integrate the modelling of multi-physical systems, including the discreet behaviour necessary to simulate the materials flow. For that purpose, this paper presents a Modelica library for the definition of simulation models able to analyse geometrical and dimensional deviations produced in process assemblies composed of a piece and a fixture. The use of Modelica language, which modelling is based on equations, requires the definition of a mathematical structure, based in this case on the TTRS (Technologically and Topologically Related Surfaces) model.

Abstract: On traditional manufacturing systems such as machine tools (MTs), the increase on their operational capacity goes hand in hand with the improvement of its efficiency and accuracy. To do that, there are two types of verification methods, direct and indirect methods. The main aim of this job is to develop a test part to machine that allows determine the influence of the geometric errors of a three linear axes MT using volumetric and geometric methods. When the test part is machined, all axes of the machine are moved simultaneously. So, the difference between machined and test part design are, among others, the results of MT geometric errors. These errors can be reduced using volumetric verification techniques and MT compensation. Moreover, a proper test part design provides a work piece than can be used as a reference artefact for MT calibration. Nominal data of the test part can be obtained using a coordinate measurement machine. So, if the MT measures the machined test part using a probe, the difference between real and nominal coordinates could be used to obtain MT geometric errors. Therefore, the test part has to be designed to allow an easy data capture of the MT; taking into consideration the different kinematic models used to improve its accuracy. The new test part developed consist of a rectangular block with grooves and battlements on its external faces and an internal pyramidal structure. In addition, a series of conical holes are strategically located along the surface to improve data capture and errors identification. Synthetic tests show that this test-part design provides good results using volumetric and geometric techniques.