Application method and station for a three-component adhesive system consisting of a resin, a fast-curing and a slow-curing component in a stoichiometric mixing ratio

Abstract

Application method for a three-component adhesive system consisting of a resin, a fast-curing and a slow-curing component in a stoichiometric mixing ratio, in which the individual adhesive components are mixed at the application site and then applied to the component bonding area, wherein the mixing ratio of the adhesive components is changed during the adhesive application, characterized in that the proportion of the slow-curing component is gradually or continuously reduced in the opposite direction to the proportion of the fast-curing component with increasing length of the adhesive application.

Description

[0001] The invention relates to an application method and an application station for a three-component adhesive mixture consisting of a resin, a fast-curing and a slow-curing component in a stoichiometric mixing ratio, comprising an adhesive mixing chamber including at least one mixing element and several metering elements regulating the quantity flow of each adhesive component to the mixing chamber, and comprising an application nozzle for applying the respective adhesive mixture from the mixing chamber to the component bonding point, according to the preamble of claim 1 or 5.

[0002] From EP 1 375 008 A2, an adhesive application system of this type for bonding automotive components is known, in which the multi-component mixing head is cleaned after each application cycle and then a new adhesive mixture with an arbitrary mixing ratio is prepared for the next adhesive application using a metering nozzle arrangement. However, with increasing application length, disproportionately longer cycle times must be observed, since the components only bond together flawlessly and firmly enough to be further processed after a waiting period corresponding to the application length following the adhesive application. This contradicts the requirement for high cycle rates, especially in series production.

[0003] Document DE 103 47 652 A1 concerns an adhesive bond between at least two joining partners comprising different materials. To improve such an adhesive bond, document DE 103 47 652 A1 proposes applying an adhesive layer with varying thickness and / or composition of adhesive components between the joining partners. The adhesive layer can be composed of two components. The layer thickness and composition of the adhesive layer can be adjusted by means of an adjustable nozzle geometry on the adhesive-applying robot.

[0004] Document DE 10 2012 021 658 A1 relates to a device, in particular for measuring the surfaces of joining points of at least two parts to be joined and preferably for joining them, with an application device for applying an application agent, in particular an adhesive and / or sealing material, to the joining points. In order to create an improved and / or alternative device, which can be used in particular in the manufacture of a rotor blade for a wind turbine, document DE 10 2012 021 658 A1 proposes to provide at least one measuring device for measuring the surfaces of the joining points, in particular the surface contours, and a movement device for moving the measuring device along the joining points, and to determine at least one application parameter depending on the measured surfaces, and preferably thus to implement a surface-dependent application process.At least one application parameter can include the quantity of the application agent to be applied. Document DE 10 2012 021 658 A1 also proposes providing a mixing device, particularly a dynamic one, for mixing multi-component adhesive material, and preferably arranging the mixing device directly before or within the application device.

[0005] In contrast, the object of the invention is to design an application method and an application station of the type mentioned above in such a way that the waiting times mentioned are significantly reduced and high-quality bonding on building components and, in particular, motor vehicle components can be produced in a series-ready manner and at a high cycle rate.

[0006] This problem is solved according to the invention by the features of claim 1 and claim 5. The dependent claims describe advantageous embodiments of the invention.

[0007] In the application method according to the invention for a three-component adhesive system consisting of a resin, a fast-curing, and a slow-curing component in a stoichiometric mixing ratio, the individual adhesive components are mixed at the application site and then applied to the component bonding area. The mixing ratio of the adhesive components is changed during the adhesive application. The proportion of the slow-curing component is reduced stepwise or continuously, in the opposite direction to the proportion of the fast-curing component, as the adhesive application length increases.

[0008] The mixing ratio of the adhesive components is progressively adjusted during the adhesive application process, taking the application length into account. This continuously or incrementally reduces the open time or pot life of the adhesive mixture from the beginning to the end of the application. As a result, the initial curing phase, during which the bond sufficiently hardens for further component handling, begins uniformly throughout the entire adhesive volume immediately after application. Consequently, the significantly longer waiting times otherwise required for defect-free bonding are eliminated. The result is a substantial increase in cycle frequency and thus a significant contribution to the standardized bonding of components in series production.

[0009] In an advantageous embodiment of the invention, a test mixture of the adhesive mixture intended for the next application cycle is prepared during the application breaks, and its reaction behavior is determined. In this way, the reaction process of the adhesive mixture can be checked before the actual adhesive application, and the next intended adhesive mixture can be readjusted if necessary.

[0010] Preferably, the adhesive mixture is produced using a motor-driven mixing element, which, in conjunction with the test mixture, has the advantage that its reaction behavior can be determined very easily, namely by means of a continuous measurement of the mixing element drive power.

[0011] According to the invention, a stoichiometric three-component mixture of a resin, a fast-curing agent and a slow-curing agent is used for bonding, especially of motor vehicle parts, and the proportion of the slow-curing agent in relation to the proportion of the fast-curing agent is reduced more and more during the adhesive application so that the end of the adhesive open time in the entire adhesive application follows the end of the application phase almost simultaneously, regardless of the application length.

[0012] In an application station for a multi-component adhesive, comprising a mixing chamber, several metering elements that regulate the flow of each adhesive component to the mixing chamber, and an application nozzle that applies the respective adhesive mixture from the mixing chamber to the component bonding point, an adhesive control system is provided. This system detects the current application length of the adhesive at the input and, as the application length increases, switches at least one of the metering elements more frequently. The metering of the adhesive components during the application process is therefore regulated automatically, without manual intervention.

[0013] In the application case according to the invention of a three-component adhesive system consisting of a resin, a fast-curing and a slow-curing component in a stoichiometric mixing ratio, at least two metering elements, namely the one for the slow-curing and the metering element for the fast-curing, are continuously or stepwise switched by the adhesive control towards a reduced open time of the adhesive mixture during the adhesive application.

[0014] The invention will now be explained in more detail using an exemplary embodiment shown in a highly schematic form in the single figure.

[0015] The application station shown in the figure contains a three-component storage unit, consisting of a resin container 1, a storage container 2 for a fast-curing agent and a storage container 3 for a slow-curing agent, as well as a mixing chamber 4, into which the individual adhesive components are fed in a stoichiometric mixing ratio via control valves 5, 6, 7 and thoroughly mixed by means of a motor-driven mixing element 8, whereupon the adhesive mixture thus produced - unlike what is shown in the figure - is conveyed via a short path to a robot-controlled application nozzle 9, through which the adhesive mixture is applied in the form of an adhesive bead 10 to the component to be bonded, e.g. a motor vehicle part made of fiber composite material 11.

[0016] After the adhesive is applied, component 11 is joined and, if the bond has solidified sufficiently for further component handling following the open adhesive time in the so-called kick-off phase, it is removed from the application station, whereupon the next work cycle can begin.

[0017] To prevent the adhesive at the beginning of the adhesive bead 10 from reacting so much further than at the end of the adhesive bead 10 during the application process that either local adhesive defects occur or long waiting times have to be accepted before component handling, the proportion of the slow-curing agent relative to the fast-curing agent is gradually or continuously reduced during the application phase in order to reduce the open time, so that the entire adhesive volume of the adhesive application has reacted to approximately the same extent at the end of the application phase, namely close to the end of the open time.

[0018] For this purpose, the application station includes an adhesive controller 12, which regulates the dosage of the adhesive components at the control valves 5, 6, 7 during adhesive application. The adhesive controller 12 receives the current position of the application nozzle 9 as an input signal from the guide robot 13 and uses previously stored control data to determine the required mixture composition.

[0019] During application breaks, a test mixture of the adhesive mixture intended for the subsequent adhesive application is prepared in mixing chamber 4 with the application nozzle 9 closed. Its reaction behavior is determined and compared with the corresponding control rate in the adhesive control unit 12, which is then adjusted if necessary. The viscosity profile over time, and thus the reaction behavior of the test mixture, can be easily determined by continuously measuring the motor power of the mixing element drive 14.

[0020] To prevent the components carrying the mixture from becoming clogged with adhesive residue, they are flushed with a solvent or slow-curing agent at certain maintenance intervals.

[0021] Numerous modifications are possible within the scope of the invention. For example, the mixing chamber 4, including the drive motor 14, and also the storage containers 1, 2, 3, together with the application nozzle 9, can be implemented in a single, compact unit and guided jointly by a robot.

Claims

[1] Application method for a three-component adhesive system consisting of a resin, a fast-curing and a slow-curing component in a stoichiometric mixing ratio, wherein the individual adhesive components are mixed at the application site and then applied to the component bonding area, wherein the mixing ratio of the adhesive components is changed during the adhesive application, characterized by , that the proportion of the slow-curing component is gradually or continuously reduced in the opposite direction to the proportion of the fast-curing component with increasing length of the adhesive application. [2] Application method according to claim 1, characterized by , that the mixing ratio is increasingly changed towards shorter pot lives of the adhesive system as the amount of adhesive applied increases. [3] Application method according to claim 1 or 2, characterized bythat the reaction behavior of the adhesive mixture is checked during the application breaks using a sample mixture. [4] Application method according to one of the preceding claims, wherein the adhesive components are mixed by means of a motor-driven mixing element, characterized by , that The mixing organ is also operated during application breaks to produce a sample mixture, and the drive power of the mixing organ drive is continuously measured to determine the reaction behavior of the sample mixture. [5] Application station for a three-component adhesive mixture consisting of a resin, a fast-curing and a slow-curing component in a stoichiometric mixing ratio, comprising an adhesive mixing chamber (4) including at least one mixing element (8) and several metering elements (5, 6, 7) regulating the quantity flow of each adhesive component to the mixing chamber, as well as an application head (9) applying the respective adhesive mixture from the mixing chamber to the component bonding point, and an adhesive control unit (12) which receives the instantaneous application length of the adhesive on the input side and which increasingly reverses at least one of the metering elements (6, 7) with increasing application length, characterized by, that at least the metering element (6) for the fast-curing component and the metering element (7) for the slow-curing component can be reversed during the application of the adhesive by gradually or continuously changing their mixture proportions in opposite directions.

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