WO2021058837A1 - Intelligent local protection system with temperature control for wire and arc additive manufacturing processes - Google Patents

Intelligent local protection system with temperature control for wire and arc additive manufacturing processes Download PDF

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Publication number
WO2021058837A1
WO2021058837A1 PCT/ES2019/070634 ES2019070634W WO2021058837A1 WO 2021058837 A1 WO2021058837 A1 WO 2021058837A1 ES 2019070634 W ES2019070634 W ES 2019070634W WO 2021058837 A1 WO2021058837 A1 WO 2021058837A1
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WIPO (PCT)
Prior art keywords
hood
solenoid valve
local protection
gas
robotic arm
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PCT/ES2019/070634
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Spanish (es)
French (fr)
Inventor
Pedro ÁLVAREZ MORO
Lexuri VAZQUEZ MARTÍNEZ
Iker RODRIGUEZ RUBIO
Original Assignee
Lortek S. Coop.
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Application filed by Lortek S. Coop. filed Critical Lortek S. Coop.
Priority to PCT/ES2019/070634 priority Critical patent/WO2021058837A1/en
Priority to ES202290029A priority patent/ES2907813B2/en
Publication of WO2021058837A1 publication Critical patent/WO2021058837A1/en

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K9/00—Arc welding or cutting
    • B23K9/32—Accessories
    • B23K9/325—Devices for supplying or evacuating shielding gas
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K9/00—Arc welding or cutting
    • B23K9/04—Welding for other purposes than joining, e.g. built-up welding
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K2103/00—Materials to be soldered, welded or cut
    • B23K2103/08—Non-ferrous metals or alloys
    • B23K2103/14—Titanium or alloys thereof

Definitions

  • the present invention falls within the technical field of additive manufacturing using electric arc and wire; which is technically called WAAM (Wire and Are Additive Manufacturing for its acronym in English). More particularly, the invention resides in an intelligent local protection system against the oxidation of reactive materials that integrates a temperature control and automatic regulation of the passage of the protection gas.
  • the local protection system can be integrated into both robotic welding installations and Cartesian kinematics machines, with path control for welding operations and additive manufacturing using electric arc and wire.
  • Additive manufacturing by electric arc and wire also known as WAAM is an additive manufacturing technology where a large amount of material provided is deposited in the form of wire that is melted by an electric arc. This process achieves high deposition rates, reducing the amount of starting material and the need for machining compared to exclusively subtractive manufacturing processes, which represents significant savings, especially in materials with high added value and difficult to machine, as is the case. of the T ⁇ -6AI-4V alloy.
  • This alloy is widely used in the aerospace sector mainly due to its high mechanical strength and excellent corrosion resistance.
  • the surface of the deposited material oxidizes, affecting its mechanical properties, thereby reducing the quality of the material it will form. part of the final piece.
  • the amount of oxygen in the final piece must not exceed 2000 ppm in any case.
  • the object of the invention is to provide an intelligent local protection system against oxidation for the manufacture by means of WAAM of components of large dimensions of reactive materials.
  • the system has a temperature control and automatic regulation of the gas flow that allows optimizing the time and the volume of shielding gas in such a way as to avoid oxygen gradients and therefore heterogeneities in the mechanical properties of the final part.
  • the intelligent system for local protection against the oxidation of reactive materials during additive manufacturing by electric arc and wire comprises:
  • a controller of the robotic arm to receive the data of the temperature measurements and give the order to close the solenoid valve and move the robotic arm to continue with the manufacturing.
  • the protection hood is provided with a lamella structure inside for generating a laminar gas flow.
  • a flow of gas Prior to the start of the weld deposition of each weld bead, a flow of gas must be applied for a time called the pre-gas time.
  • the gas flow continues during welding and once the deposition of the material in each section is completed, the protection must continue for a time called post-gas.
  • This time depends on the rate of cooling of the material to a temperature low enough to ensure slow oxidation kinetics. In the case of the T ⁇ -6AI-4V alloy, this temperature must be less than 300 - 400 ° C (D. Poquillon et al., Oxidation and Oxygen Diffusion in Ti - 6al - 4V Alloy: Improving Measurements During Sims Analysis by Rotating the Sample. Oxid. Met, 2013).
  • the method and system for measuring and controlling the temperature of the material deposited according to the invention is based on the measurement of the temperature of the material deposited in the hottest zone, that is, at the end of the weld bead deposited last, in the part closest to the piece.
  • the system has an electronic and non-contact high temperature sensor (micropyrometer or other type of pyrometer), integrated in the local protection hood.
  • the sensor measures the temperature and passes it to the controller of a robotic arm which decides when it can move to the next layer or bead after the required post gas time has been completed.
  • the robotic arm controller regulates the operation of the electronic valve that activates and deactivates the passage of shielding gas to the protective hood.
  • the temperature sensor is coupled to the external part of the local protection hood ensuring precisely the measurement just below the welding torch, that is, at the hottest point of each weld bead.
  • the space from the temperature sensor located on the outside of the hood, to the part just below the welding torch can be isolated by a cylindrical tube to avoid interaction with shielding gas or with the fumes from welding.
  • a constant pre-gas time is used, while the post time -gas after each welding is regulated through the controller of the robotic arm.
  • the robot arm controller constantly receives the temperature value measured by the sensor and once this value falls below the imposed limit, the robot arm controller gives the command to close the gas valve and immediately afterwards the command to move the robot arm.
  • the system works autonomously during the manufacturing process and at the end of the process the components are disconnected.
  • the temperature recording during the process not only serves to avoid the oxidation of the deposited material, but it is also useful to design manufacturing strategies that involve less heat accumulation, in order to optimize manufacturing times by reducing waiting times. or cooling and thus guaranteeing its mechanical quality.
  • the temperature control allows to avoid collapses, excessive grain growth and with elongated grain shapes due to the high temperature, as well as the appearance of martensite due to high temperature gradients. In this way it is possible to achieve better and homogeneous mechanical properties in the pieces.
  • the proposed intelligent local protection system for WAAM is a robust, economical and reliable solution to optimize waiting times, automatically adapting to the geometry of each part to be manufactured and avoiding trial and error operations.
  • the final oxygen content in T ⁇ -6AI-4V parts manufactured by this process is less than 2000 ppm (in compliance with ASTM E1409 and AMS 2249 standards).
  • FIGS 1a and 1b.- show a schematic view of the intelligent local protection system, in which its main components can be seen: temperature sensor (2), protective hood (1), welding torch (3), clamping mechanism ( 4), welding wire (5).
  • Figure 2. Shows a schematic view of the connections for the operation of the intelligent local protection system, in which its main components can be seen: manufactured part (6), protective hood (1), welding torch (3), mechanism of clamp (4), welding wire (5), arm (7), temperature sensor (2), robotic arm controller (8), solenoid valve (9), gas bottle (10).
  • Figure 3. Schematic of the robotic arm controller that regulates the operation of the solenoid valve and the passage of shielding gas and post-gas times.
  • the intelligent local protection system for WAAM with temperature control described is intended to optimize the post-gas times necessary to ensure correct protection of the material deposited in any specific part geometry. In this way, it is possible to avoid the oxidation of highly reactive alloys (for example, titanium or aluminum alloys), optimizing gas consumption and reducing manufacturing times.
  • highly reactive alloys for example, titanium or aluminum alloys
  • the WAAM equipment allows to deposit weld seams layer by layer, generating a part with a geometry very close to the final one.
  • robots or CNC equipment equipped with arc welding sources are used.
  • the protection device shown schematically in figure 1, comprises a temperature sensor (2), coupled to the local protection hood (1) through which the protection gas will flow, which is joined in a solid way to the torch welding (3) by means of a clamping mechanism (4) surrounding it.
  • the welding wire (5) comes out through the torch and melts forming weld seams that become part of the piece.
  • the device additionally comprises a solenoid valve that regulates the passage of gas (9) through the circuit and is connected to the gas supply system (10), to the hood ( 1), and to the robotic arm controller (8) that will send the order to the robotic arm to move the torch along with the bell and continue manufacturing.
  • the hood has a lamellar structure inside to generate a laminar gas flow.
  • the non-contact sensor for high temperature (2) is coupled to the local protection hood (1) installed in the WAAM equipment and measures the temperature of the material deposited at the end of each weld bead until the recorded temperature drops to a previously set temperature that prevents oxidation of the material. Once this condition is met, the robotic arm controller gives the order to close the gas and then to move the arm (7) or CNC axis system to continue with the deposition of layers.
  • the small size of the temperature measurement device allows a compact design of coupling to the protection device, without a significant increase in weight and integrable in conventional welding robots and WAAMs.
  • the procedure for optimizing local protection during additive manufacturing using WAAM comprises the following stages:

Abstract

The present invention relates to an intelligent gas protection system for wire and arc additive manufacturing, comprising: a welding wire (5); a welding torch (3); a local protection hood (1) surrounding the space containing the part to be manufactured; a protective gas feed system (10); a solenoid valve (9) for controlling the protective gas feed system; a robotic arm, to which the welding torch (3) and the local protection hood (1) are coupled; and a temperature sensor (2). A robotic arm controller (8), connected to the solenoid valve (9) and the temperature sensor (2), sends a signal to the solenoid valve to stop the gas flow when the temperature is below a predetermined value and to move the torch and the hood in order to continue with the manufacturing. Thus, the time for which the gas must protect the manufactured part in order to prevent the oxidation thereof is regulated automatically, optimising the manufacturing time and reducing the consumption of protective gas.

Description

SISTEMA INTELIGENTE DE PROTECCIÓN LOCAL CON CONTROL DE TEMPERATURA PARA PROCESOS DE FABRICACIÓN ADITIVA MEDIANTE INTELLIGENT LOCAL PROTECTION SYSTEM WITH TEMPERATURE CONTROL FOR ADDITIVE MANUFACTURING PROCESSES THROUGH
ARCO E HILO BOW AND THREAD
OBJETO DE LA INVENCIÓN OBJECT OF THE INVENTION
La presente invención se encuadra en el campo técnico de la fabricación aditiva mediante arco eléctrico e hilo; que técnicamente se denomina WAAM (Wire and Are Additive Manufacturing por sus siglas en inglés). Más en particular, la invención reside en un sistema inteligente de protección local frente a la oxidación de materiales reactivos que integra un control de temperatura y regulación automática del paso del gas de protección. El sistema de protección local puede integrarse tanto en instalaciones robotizadas de soldadura como en máquinas de cinemática cartesiana, con control de trayectoria para operaciones de soldadura y fabricación aditiva mediante arco eléctrico e hilo. The present invention falls within the technical field of additive manufacturing using electric arc and wire; which is technically called WAAM (Wire and Are Additive Manufacturing for its acronym in English). More particularly, the invention resides in an intelligent local protection system against the oxidation of reactive materials that integrates a temperature control and automatic regulation of the passage of the protection gas. The local protection system can be integrated into both robotic welding installations and Cartesian kinematics machines, with path control for welding operations and additive manufacturing using electric arc and wire.
ANTECEDENTES DE LA INVENCIÓN BACKGROUND OF THE INVENTION
La fabricación aditiva por arco eléctrico e hilo, también conocida como WAAM es una tecnología de fabricación aditiva donde se deposita una elevada cantidad de material provisto en forma de hilo que se funde mediante un arco eléctrico. Este proceso consigue altas tasas de deposición disminuyendo la cantidad de material de partida y la necesidad de mecanizado en comparación con procesos de fabricación exclusivamente sustractivos, lo que supone un ahorro significativo sobre todo en materiales de alto valor añadido y difíciles de mecanizar como es el caso de la aleación TÍ-6AI-4V. Additive manufacturing by electric arc and wire, also known as WAAM is an additive manufacturing technology where a large amount of material provided is deposited in the form of wire that is melted by an electric arc. This process achieves high deposition rates, reducing the amount of starting material and the need for machining compared to exclusively subtractive manufacturing processes, which represents significant savings, especially in materials with high added value and difficult to machine, as is the case. of the TÍ-6AI-4V alloy.
Esta aleación es ampliamente empleada en el sector aeroespacial debido principalmente a su elevada resistencia mecánica y excelente resistencia a corrosión. En contraposición, es habitual que, durante la fabricación aditiva con la aleación TÍ-6AI-4V, la superficie del material depositado se oxide afectando a sus propiedades mecánicas, con lo que se reduce la calidad del material que formará parte de la pieza final. Según las normativas del sector aeronáutico, la cantidad de oxígeno en pieza final no debe superar en ningún caso las 2000 ppm. This alloy is widely used in the aerospace sector mainly due to its high mechanical strength and excellent corrosion resistance. In contrast, it is common that, during additive manufacturing with the TÍ-6AI-4V alloy, the surface of the deposited material oxidizes, affecting its mechanical properties, thereby reducing the quality of the material it will form. part of the final piece. According to the regulations of the aeronautical sector, the amount of oxygen in the final piece must not exceed 2000 ppm in any case.
Actualmente, para evitar la oxidación de este material durante el proceso de WAAM se emplean cámaras o sistemas cerrados repletos de un gas protector, por ejemplo, argón. Muchos de estos sistemas requieren un flujo constante de ese gas. Su principal desventaja es que restringen el espacio o volumen de la pieza a fabricar. En otros casos se emplean sistemas de protección local que proporcionan un flujo constante de gas, lo que supone un consumo considerable, baja eficiencia y limitaciones para conseguir protección homogénea en la pieza. Currently, to prevent the oxidation of this material during the WAAM process, closed chambers or systems filled with a protective gas, for example argon, are used. Many of these systems require a constant flow of that gas. Their main disadvantage is that they restrict the space or volume of the part to be manufactured. In other cases, local protection systems are used that provide a constant flow of gas, which implies considerable consumption, low efficiency and limitations to achieve homogeneous protection in the part.
El empleo de gas durante un intervalo de tiempo constante tras la deposición de material (lo que se conoce en la técnica como tiempo de post-gas) genera un gasto de gas innecesario en algunos puntos y por el contrario un déficit de protección en otros, obteniendo piezas con gradientes en el contenido de oxígeno y por tanto con propiedades mecánicas heterogéneas. Así mismo, si el tiempo de post-gas es excesivamente corto se puede producir la oxidación del material, particularmente cuando se han depositado un elevado número de capas y la pieza está más caliente. The use of gas during a constant time interval after the deposition of material (what is known in the art as post-gas time) generates an unnecessary gas expenditure in some points and on the contrary a protection deficit in others, Obtaining pieces with gradients in the oxygen content and therefore with heterogeneous mechanical properties. Likewise, if the post-gassing time is excessively short, oxidation of the material can occur, particularly when a high number of layers have been deposited and the part is hotter.
Hay que considerar también las grandes dimensiones de las piezas objetivo de esta tecnología, que habitualmente oscilan entre 0,25 y varios metros. Durante la fabricación de éstas, la temperatura de la pieza o de partes concretas va aumentando considerablemente, lo que aumenta también el riesgo de oxidación. We must also consider the large dimensions of the target parts of this technology, which usually range between 0.25 and several meters. During the manufacture of these, the temperature of the piece or specific parts increases considerably, which also increases the risk of oxidation.
Se conocen en el actual estado de la técnica diferentes sistemas para la protección frente a la oxidación de materiales reactivos durante los procesos de soldadura, tales como cámaras cerradas (rígidas o flexibles) o sistemas de protección de arrastre (trailing). Por ejemplo, la publicación “Development of a laminar flow local shielding device for wire + are additive manufacture” (J. Ding et al., Cranfield University, 2015) describe un dispositivo de protección local para materiales reactivos durante el proceso de WAAM. Otros trabajos de los mismos autores aseguran aplicar un tiempo fijo cada vez que acaban la deposición de material (“Residual stress and texture control in TÍ-6AI-4V wire + are additive manufactured intersections by stress relief and rolling”, J. R. Hónnige et al., Cranfield University, 2018). En la patente EP3184226 se emplea una cámara cerrada que permite dimensiones de pieza máximas de 900 x 600 x 300 mm y donde se trabaja en una atmósfera de gas inerte para evitar la oxidación de la aleaciónTi-6AI-4V. Different systems are known in the current state of the art for protecting reactive materials against oxidation during welding processes, such as closed chambers (rigid or flexible) or trailing protection systems. For example, the publication “Development of a laminar flow local shielding device for wire + are additive manufacture” (J. Ding et al., Cranfield University, 2015) describes a local protection device for reactive materials during the WAAM process. Other works by the same authors claim to apply a fixed time each time they finish the deposition of material (“Residual stress and texture control in TÍ-6AI-4V wire + are additive manufactured intersections by stress relief and rolling ”, JR Hónnige et al., Cranfield University, 2018). Patent EP3184226 uses a closed chamber that allows maximum part dimensions of 900 x 600 x 300 mm and where it works in an atmosphere of inert gas to avoid oxidation of the Ti-6AI-4V alloy.
Existe sin embargo la necesidad de disponer de dispositivos que permitan optimizar la protección local de los materiales reactivos depositados mediante fabricación aditiva por arco e hilo de forma precisa y eficiente en el uso del gas de protección, para conseguir una pieza con un porcentaje mínimo de oxígeno (<0,2 % en peso para el grado 5) y evitando heterogeneidades. However, there is a need for devices that allow optimizing the local protection of the reactive materials deposited by means of additive manufacturing by arc and wire in a precise and efficient way in the use of shielding gas, to achieve a part with a minimum percentage of oxygen. (<0.2% by weight for grade 5) and avoiding heterogeneities.
DESCRIPCIÓN DE LA INVENCIÓN DESCRIPTION OF THE INVENTION
El objeto de la invención es proporcionar un sistema inteligente de protección local frente a la oxidación para la fabricación mediante WAAM de componentes de grandes dimensiones de materiales reactivos. El sistema dispone de un control de temperatura y regulación automática del flujo de gas que permite optimizar el tiempo y el volumen de gas de protección de forma que se eviten gradientes de oxígeno y por lo tanto, heterogeneidades en las propiedades mecánicas de la pieza final. The object of the invention is to provide an intelligent local protection system against oxidation for the manufacture by means of WAAM of components of large dimensions of reactive materials. The system has a temperature control and automatic regulation of the gas flow that allows optimizing the time and the volume of shielding gas in such a way as to avoid oxygen gradients and therefore heterogeneities in the mechanical properties of the final part.
El sistema inteligente para la protección local frente a la oxidación de materiales reactivos durante la fabricación aditiva mediante arco eléctrico e hilo, comprende: The intelligent system for local protection against the oxidation of reactive materials during additive manufacturing by electric arc and wire, comprises:
- una antorcha de soldadura; - a welding torch;
- un hilo de soldadura provisto en forma de bobina que sale a través de la antorcha de soldadura y se funde mediante el arco eléctrico formando cordones de soldadura. Éstos son lo que formarán la pieza mediante la deposición de unos sobre otros. - a welding wire provided in the form of a coil that exits through the welding torch and melts by means of the electric arc forming weld seams. These are what will form the piece by deposition of one on another.
- una campana de protección local para cubrir la antorcha de soldadura y la pieza que se va formando por WAAM; - a local protection hood to cover the welding torch and the piece that is being formed by WAAM;
- un circuito del gas protector para transportar el gas desde un sistema de alimentación hasta la campana de protección; - a protective gas circuit to transport the gas from a supply system to the protective hood;
- una válvula electrónica para el control del flujo de gas de protección; - an electronic valve for the control of the shielding gas flow;
- un mecanismo de sujeción de la campana a la antorcha de soldadura, - un brazo robótico para mover de forma solidaria la campana con la antorcha de soldadura y fabricar la pieza mediante WAAM; - a mechanism for fastening the hood to the welding torch, - a robotic arm to jointly move the hood with the welding torch and manufacture the part using WAAM;
- un sensor de temperatura sin contacto para la medida de temperatura en el punto de soldadura situado justo debajo de la antorcha, en la zona más próxima a la pieza;- a non-contact temperature sensor for temperature measurement at the welding point located just below the torch, in the area closest to the part;
- un controlador del brazo robótico para recibir los datos de las medidas de temperatura y dar la orden de cierre a la electroválvula y de movimiento al brazo robótico para continuar con la fabricación. - a controller of the robotic arm to receive the data of the temperature measurements and give the order to close the solenoid valve and move the robotic arm to continue with the manufacturing.
Preferentemente, la campana de protección está provista de una estructura de láminas en su interior para la generación de un flujo laminar del gas. Preferably, the protection hood is provided with a lamella structure inside for generating a laminar gas flow.
Previo al inicio de la deposición por soldadura de cada cordón de soldadura, se debe aplicar durante un tiempo un flujo de gas que se denomina tiempo de pre-gas. El flujo de gas continúa durante la soldadura y una vez terminada la deposición del material en cada tramo, la protección debe continuar durante un tiempo denominado post-gas. Ese tiempo depende de la velocidad de enfriamiento del material hasta una temperatura suficientemente baja como para asegurar una cinética de oxidación lenta. En el caso de la aleación TÍ-6AI-4V esta temperatura debe ser inferior 300 - 400 °C de temperatura (D. Poquillon et al., Oxidation and Oxygen Diffusion in Ti - 6al - 4V Alloy : Improving Measurements During Sims Analysis by Rotating the Sample. Oxid. Met, 2013). Prior to the start of the weld deposition of each weld bead, a flow of gas must be applied for a time called the pre-gas time. The gas flow continues during welding and once the deposition of the material in each section is completed, the protection must continue for a time called post-gas. This time depends on the rate of cooling of the material to a temperature low enough to ensure slow oxidation kinetics. In the case of the TÍ-6AI-4V alloy, this temperature must be less than 300 - 400 ° C (D. Poquillon et al., Oxidation and Oxygen Diffusion in Ti - 6al - 4V Alloy: Improving Measurements During Sims Analysis by Rotating the Sample. Oxid. Met, 2013).
El método y sistema de medida y control de la temperatura del material depositado según la invención se fundamenta en la medición de la temperatura del material depositado en la zona más caliente, esto es, en el final del cordón de soldadura depositado en último lugar, en la parte más próxima a la pieza. El sistema dispone de un sensor electrónico y sin contacto de alta temperatura (micropirómetro u otro tipo de pirómetro), integrado en la campana de protección local. El sensor mide la temperatura y la traslada al controlador de un brazo robótico que decide cuándo puede moverse a la siguiente capa o cordón una vez completado el tiempo de post gas requerido. Así mismo, el controlador del brazo robótico regula el funcionamiento de la válvula electrónica que activa y desactiva el paso de gas de protección hasta la campana protectora. De esta manera se regula automáticamente el tiempo que el gas debe incidir para evitar su oxidación, optimizando el tiempo de fabricación y reduciendo el consumo de gas de protección. El sensor de temperatura se acopla a la parte externa de la campana de protección local asegurando de manera precisa la medida justo debajo de la antorcha de soldadura, esto es, en el punto más caliente de cada cordón de soldadura. De manera opcional, el espacio que va desde el sensor de temperatura colocado en la parte externa de la campana, hasta la parte justamente debajo de la antorcha de soldadura, se puede aislar mediante un tubo cilindrico para evitar la interacción con el gas de protección o con los humos provenientes de la soldadura. The method and system for measuring and controlling the temperature of the material deposited according to the invention is based on the measurement of the temperature of the material deposited in the hottest zone, that is, at the end of the weld bead deposited last, in the part closest to the piece. The system has an electronic and non-contact high temperature sensor (micropyrometer or other type of pyrometer), integrated in the local protection hood. The sensor measures the temperature and passes it to the controller of a robotic arm which decides when it can move to the next layer or bead after the required post gas time has been completed. Likewise, the robotic arm controller regulates the operation of the electronic valve that activates and deactivates the passage of shielding gas to the protective hood. In this way, the time that the gas must affect to avoid its oxidation is automatically regulated, optimizing the manufacturing time and reducing the consumption of shielding gas. The temperature sensor is coupled to the external part of the local protection hood ensuring precisely the measurement just below the welding torch, that is, at the hottest point of each weld bead. Optionally, the space from the temperature sensor located on the outside of the hood, to the part just below the welding torch, can be isolated by a cylindrical tube to avoid interaction with shielding gas or with the fumes from welding.
Los pasos para trabajar con el sistema inteligente de protección local descrito comprenden: The steps to work with the intelligent local protection system described include:
- colocación de la campana de protección local en la antorcha de soldadura; - Placement of the local protection hood on the welding torch;
- conexión del sistema de alimentación del gas de protección a través de la electroválvula; - connection of the shielding gas supply system through the solenoid valve;
- regulación de la posición de enfoque del sensor de temperatura para asegurar su alineamiento con el punto de medida requerido; - regulation of the focus position of the temperature sensor to ensure its alignment with the required measurement point;
- encendido de componentes: brazo robótico, equipo soldadura, sensor, electroválvula; - Component ignition: robotic arm, welding equipment, sensor, solenoid valve;
- programación de trayectorias del brazo robótico y secuencia de operaciones para la fabricación de la pieza mediante la deposición de cordones de soldadura, bien de forma manual o con herramientas CAM, se emplea un tiempo de pre-gas constante, mientras que el tiempo de post-gas tras cada soldadura se regula a través del controlador del brazo robótico. El controlador del brazo robótico recibe constantemente el valor de temperatura medido por el sensor y una vez que este valor baja del límite impuesto, el controlador del brazo robótico da la orden del cierre de la válvula de gas e inmediatamente después la de movimiento al brazo robótico; - programming of trajectories of the robotic arm and sequence of operations for the manufacture of the part by deposition of weld seams, either manually or with CAM tools, a constant pre-gas time is used, while the post time -gas after each welding is regulated through the controller of the robotic arm. The robot arm controller constantly receives the temperature value measured by the sensor and once this value falls below the imposed limit, the robot arm controller gives the command to close the gas valve and immediately afterwards the command to move the robot arm. ;
- inicio de la fabricación mediante WAAM. - start of manufacturing by WAAM.
El sistema trabaja de forma autónoma durante el proceso de fabricación y al final del proceso se desconectan los componentes. The system works autonomously during the manufacturing process and at the end of the process the components are disconnected.
El registro de temperatura durante el proceso no sólo sirve para evitar la oxidación del material depositado, sino que también es útil para diseñar estrategias de fabricación que conlleven una menor acumulación de calor, con el fin de optimizar los tiempos de fabricación reduciendo los tiempos de espera o enfriamiento y garantizando de esta manera la calidad mecánica de la misma. Asimismo, el control de temperatura permite evitar colapsos, crecimiento de grano excesivos y con formas de grano alargadas debido a la elevada temperatura, así como la aparición de martensita debido a elevados gradientes de temperatura. De esta manera es posible alcanzar unas propiedades mecánicas mejores y homogéneas en las piezas. The temperature recording during the process not only serves to avoid the oxidation of the deposited material, but it is also useful to design manufacturing strategies that involve less heat accumulation, in order to optimize manufacturing times by reducing waiting times. or cooling and thus guaranteeing its mechanical quality. Likewise, the temperature control allows to avoid collapses, excessive grain growth and with elongated grain shapes due to the high temperature, as well as the appearance of martensite due to high temperature gradients. In this way it is possible to achieve better and homogeneous mechanical properties in the pieces.
El sistema inteligente de protección local para WAAM propuesto supone una solución robusta, económica y fiable para optimizar los tiempos de espera adaptándose automáticamente a la geometría de cada pieza a fabricar y evitando operaciones de prueba y error. The proposed intelligent local protection system for WAAM is a robust, economical and reliable solution to optimize waiting times, automatically adapting to the geometry of each part to be manufactured and avoiding trial and error operations.
El contenido en oxígeno final en las piezas de TÍ-6AI-4V fabricadas mediante este proceso es inferior a 2000 ppm (en cumplimiento con las normas ASTM E1409 y AMS 2249). The final oxygen content in TÍ-6AI-4V parts manufactured by this process is less than 2000 ppm (in compliance with ASTM E1409 and AMS 2249 standards).
DESCRIPCIÓN DE LAS FIGURAS DESCRIPTION OF THE FIGURES
Para complementar la descripción del sistema inteligente de protección para WAAM y con objeto de ayudar a una mejor comprensión de las características de la invención, de acuerdo con un ejemplo preferente de realización práctica de la misma, se acompaña como parte integrante de dicha descripción, unas figuras en donde con carácter ilustrativo y no limitativo, se ha representado lo siguiente: To complement the description of the intelligent protection system for WAAM and in order to help a better understanding of the characteristics of the invention, according to a preferred example of practical implementation of the same, it is attached as an integral part of said description, some Figures where, with an illustrative and non-limiting nature, the following has been represented:
Figuras 1a y 1b.- Muestran una vista esquemática del sistema inteligente de protección local, en la que se aprecian sus principales componentes: sensor de temperatura (2), campana protectora (1), antorcha de soldadura (3), mecanismo de sujeción (4), hilo de soldadura (5). Figures 1a and 1b.- They show a schematic view of the intelligent local protection system, in which its main components can be seen: temperature sensor (2), protective hood (1), welding torch (3), clamping mechanism ( 4), welding wire (5).
Figura 2.- Muestra una vista esquemática de las conexiones del funcionamiento del sistema inteligente de protección local, en la que se aprecian sus principales componentes: pieza fabricada (6), campana protectora (1), antorcha de soldadura (3), mecanismo de sujeción (4), hilo de soldadura (5), brazo (7), sensor de temperatura (2), controlador del brazo robótico (8), electroválvula (9), botella de gas (10). Figura 3.- Esquema del controlador del brazo robótico que regula el funcionamiento de la electroválvula y el paso de gas de protección y los tiempos de post-gas. Figure 2.- Shows a schematic view of the connections for the operation of the intelligent local protection system, in which its main components can be seen: manufactured part (6), protective hood (1), welding torch (3), mechanism of clamp (4), welding wire (5), arm (7), temperature sensor (2), robotic arm controller (8), solenoid valve (9), gas bottle (10). Figure 3.- Schematic of the robotic arm controller that regulates the operation of the solenoid valve and the passage of shielding gas and post-gas times.
REALIZACIÓN PREFERENTE DE LA INVENCIÓN PREFERRED EMBODIMENT OF THE INVENTION
Seguidamente se proporciona, con ayuda de las figuras anteriormente referidas, una explicación detallada de un ejemplo de realización preferente del objeto de la presente invención. A detailed explanation of a preferred embodiment of the object of the present invention is provided below, with the aid of the aforementioned figures.
El sistema inteligente de protección local para WAAM con control de temperatura que se describe está destinado a la optimización de los tiempos de post-gas necesarios para asegurar una correcta protección del material depositado en cualquier geometría de pieza concreta. De esta manera es posible evitar la oxidación de aleaciones muy reactivas (por ejemplo, aleaciones de titanio o aluminio) optimizando los consumos de gas y reduciendo los tiempos de fabricación. The intelligent local protection system for WAAM with temperature control described is intended to optimize the post-gas times necessary to ensure correct protection of the material deposited in any specific part geometry. In this way, it is possible to avoid the oxidation of highly reactive alloys (for example, titanium or aluminum alloys), optimizing gas consumption and reducing manufacturing times.
El equipo de WAAM permite depositar capa a capa cordones de soldadura generando una pieza con una geometría muy cercana a la final. Para ello se emplean robots o equipos CNC equipados con fuentes de soldadura al arco (MIG- MAG, TIG o plasma). The WAAM equipment allows to deposit weld seams layer by layer, generating a part with a geometry very close to the final one. For this, robots or CNC equipment equipped with arc welding sources (MIG-MAG, TIG or plasma) are used.
El dispositivo de protección, mostrado esquemáticamente en la figura 1, comprende un sensor de temperatura (2), acoplado a la campana de protección local (1) por la que fluirá el gas de protección, la cual se une de forma solidaria a la antorcha de soldadura (3) mediante un mecanismo de sujeción (4) rodeándola. A través de la antorcha sale el hilo de soldadura (5) que se funde formando cordones de soldadura que pasan a formar parte de la pieza. En la realización preferente aquí descrita y como muestra la figura 2, el dispositivo comprende adicionalmente una electroválvula que regula el paso de gas (9) a través del circuito y que está conectada al sistema de alimentación del gas (10), a la campana (1), y al controlador del brazo robótico (8) que enviará la orden al brazo robótico para desplazar la antorcha junto con la campana y continuar con la fabricación. La campana presenta una estructura de láminas en su interior para la generación de un flujo de gas laminar. Como se resume en la figura 3, el sensor sin contacto para alta temperatura (2) se acopla a la campana protección local (1) instalada en el equipo de WAAM y mide la temperatura del material depositado al final de cada cordón de soldadura hasta que la temperatura registrada desciende a una temperatura previamente fijada y que evita la oxidación del material. Una vez cumplida esta condición, el controlador del brazo robótico da la orden de cerrar el gas y seguidamente de movimiento al brazo (7) o sistema de ejes CNC para continuar con la deposición de capas. The protection device, shown schematically in figure 1, comprises a temperature sensor (2), coupled to the local protection hood (1) through which the protection gas will flow, which is joined in a solid way to the torch welding (3) by means of a clamping mechanism (4) surrounding it. The welding wire (5) comes out through the torch and melts forming weld seams that become part of the piece. In the preferred embodiment described here and as shown in figure 2, the device additionally comprises a solenoid valve that regulates the passage of gas (9) through the circuit and is connected to the gas supply system (10), to the hood ( 1), and to the robotic arm controller (8) that will send the order to the robotic arm to move the torch along with the bell and continue manufacturing. The hood has a lamellar structure inside to generate a laminar gas flow. As summarized in figure 3, the non-contact sensor for high temperature (2) is coupled to the local protection hood (1) installed in the WAAM equipment and measures the temperature of the material deposited at the end of each weld bead until the recorded temperature drops to a previously set temperature that prevents oxidation of the material. Once this condition is met, the robotic arm controller gives the order to close the gas and then to move the arm (7) or CNC axis system to continue with the deposition of layers.
El reducido tamaño del dispositivo de medición de temperatura permite un diseño de acople al dispositivo de protección compacto, sin un aumento de peso significativo e integrable en robots de soldadura y WAAM convencionales. The small size of the temperature measurement device allows a compact design of coupling to the protection device, without a significant increase in weight and integrable in conventional welding robots and WAAMs.
El procedimiento de optimización de la protección local durante la fabricación aditiva mediante WAAM, asociado al dispositivo anteriormente descrito, comprende las siguientes etapas: The procedure for optimizing local protection during additive manufacturing using WAAM, associated with the device described above, comprises the following stages:
- colocación de la campana de protección local (1) en la antorcha de soldadura (3);- Placement of the local protection hood (1) on the welding torch (3);
- regulación de la posición de enfoque del sensor de temperatura (2) para asegurar su alineamiento con el punto de medida requerido (6) - regulation of the focus position of the temperature sensor (2) to ensure its alignment with the required measurement point (6)
- conexión del sistema de alimentación del gas de protección (10) a través de la electroválvula (9); - connection of the shielding gas supply system (10) through the solenoid valve (9);
- conexión de la electroválvula (9) y sensor de temperatura (2) al controlador del brazo robótico (8); - connection of the solenoid valve (9) and temperature sensor (2) to the robotic arm controller (8);
- programación de trayectorias y secuencia de operaciones, bien de forma manual o con herramientas CAM, se emplea un tiempo de pre-gas constante, mientras que el tiempo de post-gas tras cada soldadura se regula a través del controlador del brazo robótico; - programming of trajectories and sequence of operations, either manually or with CAM tools, a constant pre-gas time is used, while the post-gas time after each weld is regulated through the robotic arm controller;
- inicio de las operaciones de soldadura y fabricación mediante WAAM. - start of welding and manufacturing operations through WAAM.

Claims

REIVINDICACIONES
1. Sistema inteligente de protección local con gas para procesos de fabricación aditiva mediante arco e hilo, que comprende los siguientes elementos: un hilo de soldadura (5) provisto en forma de bobina que se funde mediante el arco eléctrico formando cordones de soldadura; una antorcha de soldadura (3); una campana de protección local (1) rodeando el espacio donde se sitúa la pieza a fabricar; un sistema de alimentación de gas de protección (10); una electroválvula (9) para controlar el sistema de alimentación del gas de protección; un brazo robótico al que se acoplan la antorcha de soldadura (3) y la campana de protección local (1); caracterizado por que el sistema incluye además: un sensor de temperatura (2), acoplado a la campana de protección local (1); un controlador del brazo robótico (8) conectado a la electroválvula (9) y al sensor de temperatura (2) de manera que el controlador del brazo robótico está programado para mandar una señal a la electroválvula para parar el flujo de gas cuando la temperatura está por debajo de un valor predeterminado y mover la antorcha y la campana para proseguir con la fabricación. 1. Intelligent local gas protection system for additive manufacturing processes using arc and wire, comprising the following elements: a welding wire (5) provided in the form of a coil that melts by means of the electric arc forming weld seams; a welding torch (3); a local protection hood (1) surrounding the space where the part to be manufactured is located; a shielding gas feed system (10); a solenoid valve (9) to control the shielding gas supply system; a robotic arm to which the welding torch (3) and the local protection hood (1) are attached; characterized in that the system also includes: a temperature sensor (2), coupled to the local protection hood (1); a robotic arm controller (8) connected to the solenoid valve (9) and the temperature sensor (2) so that the robot arm controller is programmed to send a signal to the solenoid valve to stop gas flow when the temperature is below a predetermined value and move the torch and hood to continue manufacturing.
2. Sistema inteligente de protección local según la reivindicación 1 caracterizado porque la campana de protección local (1) está provista en su interior de lámelas para producir un flujo de gas laminar. 2. Intelligent local protection system according to claim 1, characterized in that the local protection hood (1) is provided inside with lamellas to produce a laminar gas flow.
3. Sistema inteligente de protección local según cualquiera de las reivindicaciones anteriores, caracterizado por que la campana está unida de forma solidaria a la antorcha de soldadura (3) mediante un mecanismo de sujeción (4). 3. Intelligent local protection system according to any of the preceding claims, characterized in that the hood is integrally attached to the welding torch (3) by means of a clamping mechanism (4).
4. Procedimiento de fabricación aditiva mediante arco e hilo con un sistema según cualquiera de las reivindicaciones anteriores caracterizado porque comprende los siguientes pasos: 4. Additive manufacturing method using bow and wire with a system according to any of the preceding claims, characterized in that it comprises the following steps:
- colocación de la campana de protección local en la antorcha de soldadura; -conexión del sistema de alimentación del gas de protección controlado a través de la electroválvula; - Placement of the local protection hood on the welding torch; -connection of the shielding gas supply system controlled through the solenoid valve;
-colocación del sensor de temperatura en la campana y comprobación de la ubicación del punto de medida -encendido del brazo robótico, controlador del brazo robótico, sensor de temperatura y electroválvula; -placing the temperature sensor in the hood and checking the location of the measurement point-turning on the robotic arm, robotic arm controller, temperature sensor and solenoid valve;
-programación de trayectorias del brazo robótico y secuencia de operaciones para la fabricación de la pieza mediante la deposición de cordones de soldadura; -programming of trajectories of the robotic arm and sequence of operations for the manufacture of the piece by means of the deposition of weld beads;
- apertura la electroválvula para la aplicación del gas; - deposición del cordón de soldadura según la secuencia de fabricación programada; - opening the solenoid valve for gas application; - deposition of the weld bead according to the programmed manufacturing sequence;
- donde el brazo robótico y la electroválvula reciben una señal del controlador del brazo robótico para parar el flujo de gas cuando la temperatura está por debajo de un valor predeterminado detectado por el sensor de temperatura y mover la antorcha y la campana para proseguir con la fabricación. - where the robot arm and solenoid valve receive a signal from the robot arm controller to stop the gas flow when the temperature is below a predetermined value detected by the temperature sensor and move the torch and hood to continue manufacturing .
PCT/ES2019/070634 2019-09-24 2019-09-24 Intelligent local protection system with temperature control for wire and arc additive manufacturing processes WO2021058837A1 (en)

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