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2022
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Universidad Nacional de Educación a Distancia (España). Universidad Politécnica de Madrid. Departamento de Ingeniería Mecánica
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Resumen
En las aplicaciones de mecanizado, los robots industriales son utilizados en células de mecanizado con exigencias de precisión no elevadas o en células flexibles de fabricación para carga y descarga de máquinas y manipulación de piezas y otros elementos. En estos últimos casos, los robots, al no alcanzar precisiones de posicionamiento elevadas, se relegan a la realización de tareas de pre-mecanizado y desbarbado, o para tareas de manipulación. En el trabajo que se presenta, se trata de mejorar la productividad de las células de fabricación mediante una reasignación de tareas entre las máquinas herramientas y el robot o entre fases previas de conformado y del robot. Esta reasignación se basa en establecer la verdadera capacidad de trabajo del robot considerando las fuerzas de proceso y teniendo en cuenta la precisión especificada del producto a fabricar mediante el modelado preciso de su comportamiento. Este modelado se ha realizado utilizando el método multicuerpo y considerando una rigidez variable en las articulaciones del robot. La reasignación de tareas se realiza en base a determinar el comportamiento del robot en los distintos puntos del área de trabajo y por lo tanto disponiendo de los mapas de precisión de trabajo y en determinar en la dirección de mecanizado donde se producen los mejores resultados. A partir de ello se obtiene la posible reasignación de tareas, el punto de posicionamiento y la orientación de la pieza en el área de trabajo. La información de entrada al modelo del robot es la fuerza de corte simulada o medida modificada de acuerdo con la influencia de las variaciones de los parámetros de mecanizado. Estas variaciones se producen debido a las desviaciones del robot durante la trayectoria de mecanizado. Para tener en cuenta las variaciones de los parámetros de mecanizado se define una función para cada uno de ellos donde se recoge la influencia en el valor de la fuerza. Está información de entrada podrá ser modificada a partir de la realimentación que se tenga del comportamiento estimado del robot. Los ensayos de fuerzas medidas se han realizado en un centro de mecanizado, al que se considera como rígido, que representa adecuadamente las fuerzas de base que entran en juego. Los resultados del modelado del robot y su interacción con las fuerzas de corte muestran la influencia del tipo de robot y la zona de trabajo en la cual éste está trabajando, permitiendo caracterizar el proceso. Como resultados del trabajo se espera determinar el incremento de productividad que se puede conseguir en aplicaciones de células de fabricación flexibles o en células de mecanizado robotizado.
Industrial robots are employed for machining tasks in manufacturing cells for low precision requirements or in flexible manufacturing cells for loading and unloading machines and handling parts and other components. In that latter case, robots are limited to pre-machining and deburring tasks, or for handling tasks, as they do not achieve high positioning accuracy. The aim of this work that it is shown is to improve the productivity of manufacturing cells by reallocating tasks between the machine tools and the robot or between previous forming and robot phases. This reallocation is performed by establishing the true working capacity of the robot considering the process forces and taking into account the specified precision of the product to be manufactured by accurately modelling its behaviour. This modelling has been carried out using the multi-body method and considering a variable stiffness in the robot joints. The reassignment of tasks is carried out on the basis of determining the behaviour of the robot in the different points of the working area and therefore having the work precision maps and determining the machining direction where the best results are produced. This results in the possible reallocation of tasks, the positioning point and the orientation of the workpiece in the work area. The input information to the robot model is the simulated or measured cutting force modified according to the influence of variations in the machining parameters. These variations occur due to deviations of the robot during the machining path. To take into account the variations of the machining parameters, a function is defined for each machining parameter where the influence on the force value is recorded. This input information can be modified on the basis of feedback from the estimated behaviour of the robot. The measured force tests have been carried out on a machining centre, which is considered to be rigid, which adequately represents the basic forces that come into play. The results of the modelling of the robot and its interaction with the cutting forces show the influence of the type of robot and the work area in which it is working, allowing the process to be characterised. The results of the work are expected to determine the increase in productivity that can be achieved in flexible manufacturing cell applications or in robotic machining cells.
Industrial robots are employed for machining tasks in manufacturing cells for low precision requirements or in flexible manufacturing cells for loading and unloading machines and handling parts and other components. In that latter case, robots are limited to pre-machining and deburring tasks, or for handling tasks, as they do not achieve high positioning accuracy. The aim of this work that it is shown is to improve the productivity of manufacturing cells by reallocating tasks between the machine tools and the robot or between previous forming and robot phases. This reallocation is performed by establishing the true working capacity of the robot considering the process forces and taking into account the specified precision of the product to be manufactured by accurately modelling its behaviour. This modelling has been carried out using the multi-body method and considering a variable stiffness in the robot joints. The reassignment of tasks is carried out on the basis of determining the behaviour of the robot in the different points of the working area and therefore having the work precision maps and determining the machining direction where the best results are produced. This results in the possible reallocation of tasks, the positioning point and the orientation of the workpiece in the work area. The input information to the robot model is the simulated or measured cutting force modified according to the influence of variations in the machining parameters. These variations occur due to deviations of the robot during the machining path. To take into account the variations of the machining parameters, a function is defined for each machining parameter where the influence on the force value is recorded. This input information can be modified on the basis of feedback from the estimated behaviour of the robot. The measured force tests have been carried out on a machining centre, which is considered to be rigid, which adequately represents the basic forces that come into play. The results of the modelling of the robot and its interaction with the cutting forces show the influence of the type of robot and the work area in which it is working, allowing the process to be characterised. The results of the work are expected to determine the increase in productivity that can be achieved in flexible manufacturing cell applications or in robotic machining cells.
Descripción
Categorías UNESCO
Palabras clave
posición, sistemas multicuerpo, robot, taladrado, fresado
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Centro
E.T.S. de Ingenieros Industriales
Departamento
Mecánica