Modelo integral de sistemas de sujeción basados en pinzas expansibles

El dispositivo de amarre de propósito general más versátil es el porta-pinzas, muy frecuentemente utilizado en fresado, torneado, taladrado e inspección. Los porta-pinzas deben alcanzar elevadas velocidades de rotación, manteniendo, simultáneamente, una alta precisión rotacional. El porta-pinzas, básicamente, es un mecanismo basado en el efecto cuña, donde la mayoría de ellos emplean anillos, con ranuras finas, hechos de acero templado y rectificado con altos grados de precisión, denominados pinzas. Esta Tesis Doctoral aborda el funcionamiento de los porta-pinzas, primero se presentan varios modelos analíticos, basados en la teoría del sólido rígido, la elasticidad y la mecánica del contacto, para determinar la fuerza de amarre suministrada por un plato porta-pinzas automático en su estado inicial estático, durante el proceso de transmisión y absorción de fuerza. Segundo, se presentan los modelos analíticos para determinar la fuerza de amarre dinámica, durante el proceso de rotación. Tercero, se presentan los modelos y análisis realizados por el método de los elementos finitos que fueron llevados a cabo para realizar una primera verificación de los modelos analíticos propuestos. En cuarto lugar, se describe el banco de ensayos construido para validar experimentalmente los modelos analíticos y numéricos de elementos finitos propuestos. Quinto, se propone un prototipo de dispositivo porta-pinzas automático que fue diseñado aplicando la metodología y los modelos analíticos propuestos, incorporando innovaciones en detección de presencia de pieza, control de posicionado de pieza, control de fuerza de accionamiento y en su sistema de transmisión. Los resultados del presente estudio proporcionan soporte técnico y teórico, de comprobada fiabilidad, para la optimización del diseño y aplicación de platos porta-pinzas automáticos en procesos de mecanizado de alto rendimiento. -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------The most versatile general purpose clamping device is collet chuck, which are quite often used in turning, milling, grinding and inspection. Collet chucks must achieve high rotational speeds while maintaining good rotational accuracy. Collet chucks are wedged-actuated mechanisms which use solid thin slotted clamping sleeves made of hardened steel and ground to a high degree of accuracy, called collets. This Ph. D. Thesis, first presents the analytical models, based on solid rigid theory, elasticity and contact mechanics, to determinate the clamping force provide by an automatic collet-chuck holder in its initial static state. Second, it presents the analytical model for determining the dynamic clamping force of collet-chuck holders during high-speed turning. Third, it describes the fi nite element method analyses that were conducted to check the proposed analytical models. Fourth, it describes an automatic (wedge-actuated) bench device, which was designed and built for verifying the proposed analytical and numerical models. Fifth, it develops an automatic collet-chuck holder prototype which was designed taking into account the proposed methodology and analytical models within novel systems in control of workpiece presence, control of workpiece position, control of clamping force and in its structure transmission. This study results provide reliable theoretical and technical supports for the optimization of the design and application of collet-chuck holder in high performance machining processes

Mathematical analysis of the process forces effect on collet chuck holders

Chuck holders are widely used for jobs with high precision. A chuck holder consists of a nut with a tapered surface and a thin-slotted clamping sleeve typically made of hardened steel and named a collet. Chuck holders are, essentially, wedge mechanisms. In this paper, we investigated the reactions and strains due to the forces during the chip removal process in the contact elements or jaws of the collet by means of mathematical analysis. Deflections in the jaws of the collet arise with a high influence from the precision of the workpieces. The cutting or process forces cause an axial force, a radial force, a torsional moment, and a bending moment on the chuck collet, and, consequently, displacements and inclinations of the clamping system are caused. Therefore, the proposed analytical models are based on elasticity and contact theories. The mathematical model for determining the deflections of the clamping system force was developed and implemented using MATLAB. The results showed that the variation in the clamping force during rotation in a collet chuck holder mainly depends on the stiffness of the collet chuck holder and the stiffness of the workpiece. The results indicated that the collet should be vulcanized to minimize the deformations that affect the final product. The deflections of a collet chuck holder due to process forces depend strongly on the clearances, wedge angle, and stiffness of the collet

Predictive Suspension Algorithm for Land Vehicles over Deterministic Topography

A good suspension system is mandatory for ensuring stability, comfort and safety in land vehicles; therefore, advanced semi and fully active suspension systems have been developed along with their associated management strategies to overcome the limitations of passive suspensions. This paper presents a suspension algorithm for land vehicles traveling through a deterministic topography. The kinematics of a half-vehicle model and the algorithm are implemented in Simulink. The algorithm’s inputs are the measurements provided by a position scanner located on the front wheel of the vehicle. Based on this input, the algorithm reconstructs the topography in real-time and sends the corresponding command to an actuator located on the rear wheel to compensate for the irregularities of the terrain. The actuation is governed by the parameter “D”, which represents the distance over which the algorithm averages the height of the terrain. Two ground profiles were tested and sensitivity analysis of the parameter “D” was performed. Results show that larger values of “D” usually yield less vibration on the actuated mass, but this value also depends on the irregularities of the terrain.The research work described in this paper is part of the R&D and Innovation projects MC4.0 PID2020-116984RB-C21 and MC4.0 PID2020-116984RB-C22 supported by the MCIN/AEI/10.13039/ 501100011033

Validación experimental de una pinza de dos dedos retráctiles

This paper presents analytical, numerical, and experimental testing models for designing and validating the feasibility of a gripper with two retractable fingers. The proposed gripper is specifically developed for grasping and manipulating objects that should be kept into restricted areas such as explosives, radioactive/ionized materials, and infected biological material specimens. The proposed gripper fingers can be retracted to pass through openings or slots and, once inside the restricted area, can be deployed in order to manipulate the objects without risk for the human operators. Analytical and numerical simulations are used to properly design and build a gripper prototype. Then, experimental tests are carried out to grasp objects of different sizes ranging from 5 to 10 mm. The obtained results are used to validate the gripper"s performance in terms of successful grasp and suitable accelerations and grasp forces

Methodology for the integration of a high-speed train in Maintenance 4.0

The fourth industrial revolution is changing the way industries face their problems, including maintenance. The railway industry is moving to adopt this new industry model. The new trains are designed, manufactured, and maintained following an Industry 4.0 methodology, but most of the current trains in operation were not designed with this technological philosophy, so they must be adapted to it. In this paper, a new methodology for adapting a high-speed train to Industry 4.0 is proposed. That way, a train manufactured before this new paradigm can seize the advantages of Maintenance 4.0. This methodology is based on four stages (physical system, digital twin, information and communication technology infrastructure, and diagnosis) that comprise the required processes to digitalize a railway vehicle and that share information between them. The characteristics that the data acquisition and communication systems must fulfil are described, as well as the original signal processing techniques developed for analysing vibration signals. These techniques allow processing experimental data both in real time and deferred, according to actual maintenance requirements. The methodology is applied to determine the operating condition of a high-speed bogie by combining the signal processing of actual vibration measurements taken during the normal train operation and the data obtained from simulations of the digital twin. The combination of both (experimental data and simulations) allows establishing characteristic indicators that correspond to the normal running of the train and indicators that would correspond to anomalies in the behaviour of the train.The research work described in this paper was supported by the Spanish Government through the MM-IA4.0 PID2020-116984RB-C21 and RMS4.0 PID2020-116984RB-C22 projects

Automatic Expanding Mandrel with Air Sensing Device: Design and Analysis

In precision machining, expanding mandrels are used for jobs with close tolerances. An expanding mandrel consists of a tapered arbor or shaft, with a thin-slotted clamping sleeve or collet made of hardened steel. The internal tapered and external cylindrical surfaces are ground to a high degree of accuracy, and the mandrel expands to fit the internal bore of the workpiece. Expanding mandrels are, essentially, wedge mechanisms. This paper proposes an automatic expanding mandrel with a novel force transmission system for high stiffness within a novel air sensing system, which allows detection of the correct part position before starting machining. A computational model for determining the dynamic clamping force of the proposed mechanism is developed and implemented using MATLAB. This model considers the influence of the sti ness behaviors of the collet, force transmission structure and workpiece. Additionally, this paper presents the finite element method analyses which were conducted to check the proposed computational model. The amount of clamping force transmitted by a collet chuck holder depends strongly on: clearances, wedge angle, stiffness of the collet chuck holder and workpiece stiffness

Design of an Orthopedic Product by Using Additive Manufacturing Technology: The Arm Splint

[EN]The traditional fabrication process of custom-made splints has hardly undergone any progress since the beginning of its use at the end of the eighteenth century. New manufacturing techniques and the new materials can help to modernize this treatment method of fractures. The use of Additive Manufacturing has been proposed in recent years as an alternative process for the manufacture of splints and there has been an increase in public awareness and exploration. For this reason, in this study a splint model printed in 3D, that replaces the deficiencies of the cast maintaining its virtues, has been proposed. The proposed methodology is based on three-dimensional digitalization techniques and 3D modeling with reverse engineering software. The work integrates different scientific disciplines to achieve its main goal: to improve life quality of the patient. In addition, the splint has been designed based on the principles of sustainable development. The design of splint is made of Polycarbonate by technique of Additive Manufacturing with fused deposition manufacturing, and conceived with organic shapes, customizing openings and closing buttons with rubber. In this preliminary study the final result is a prototype of the 3D printed arm splint in a reduced scale by using PLA as material

Filament Advance Detection Sensor for Fused Deposition Modelling 3D Printers

The main purpose of this paper is to present a system to detect extrusion failures in fused deposition modelling (FDM) 3D printers by sensing that the filament is moving forward properly. After several years using these kind of machines, authors detected that there is not any system to detect the main problem in FDM machines. Authors thought in different sensors and used the weighted objectives method, one of the most common evaluation methods, for comparing design concepts based on an overall value per design concept. Taking into account the obtained scores of each specification, the best choice for this work is the optical encoder. Once the sensor is chosen, it is necessary to design de part where it will be installed without interfering with the normal function of the machine. To do it, photogrammetry scanning methodology was employed. The developed device perfectly detects the advance of the filament without affecting the normal operation of the machine. Also, it is achieved the primary objective of the system, avoiding loss of material, energy, and mechanical wear, keeping the premise of making a low-cost product that does not significantly increase the cost of the machine. This development has made it possible to use the printer with remains of coil filaments, which were not spent because they were not sufficient to complete an impression. Also, printing models in two colours with only one extruder has been enabled by this development

Behavior under Load of A Human Shoulder: Finite Element Simulation and Analysis

[EN]Most musculoskeletal injuries occur during the work routines in different areas, due to repetitive and sustained movements, they are often located in the shoulder. For workers in the building sector, the repetitive movements and displacements occur under load and unnatural postures of the shoulder joint. For this reason, this study aims to model in 3D the biological components which form the shoulder joint for the later finite element analysis. Three cases with different loads have been considered for this study. Due to a linear and isotropic joint approach it has been possible to evaluate the tensions in the main components of the shoulders: muscles, tendons and ligaments

Real time analysis of the filament for FDM 3D printers

[EN]This project raises the need to develop a quality control system for manufacturing processes by melt deposition. The main problem with this technology is that, if the environmental parameters are not sufficiently controlled, inaccuracy is created between the mechanical and aesthetic properties of the product. This causes that the pieces do not meet the requirements for the market since they cannot guarantee a unified performance. For this purpose, a proof of concept that implements the necessary sensors in a testing machine will be carried out. The sensors will collect the measurements by means of an Arduino microcontroller. The obtained information will be processed in order to make the reports that indicate if the manufacturing process meets the expected requirements. With this system it is possible to improve the manufacturing results by melted deposition and to assure quality standards. In the future, the system could be improved according to the quality parameters required by the ISO standards for printing filaments and also used to certify them. Considering all the aforementioned, this is undoubtedly a field of research that still has much to develop and it is expected that this work will be a contribution for future research