Arrangement and procedure for providing molded parts

Abstract

Arrangement for the provision of molded parts, comprising a molding machine (10) for the production of the molded parts, a transport device (5) for the molded parts, and a common system control (1) for the molding machine (10) and the transport device (5), wherein: - a thermographic station (6) with a thermographic detector (11) for detecting electromagnetic radiation emitted by the molded parts and an energy source (14) for heating the molded parts, - a molded part holder (12) in which the molded parts can be positioned by means of the transport device (5), and - an interface (13) connected to the detector (11) by means of which measurement data from the detector (11) and / or quality reports generated therefrom can be output to the common system control (1), characterized in that the energy source (14) is configured toto vary the thermal energy deposited in the molded part over time and the thermographic station (6) and / or the joint system control (1) is designed to store the presence of a quality defect of the molded parts in conjunction with data for the identification of the molded parts in a memory in the event of a difference in the runtime of the reactions originating from different locations of the molded parts to the time-varying introduced thermal energy.

Description

The present invention relates to an arrangement for providing molded parts according to the preamble of claim 1 and to a method for providing molded parts according to the preamble of claim 11. Typical arrangements include a forming machine for producing the molded parts and a transport device for moving the molded parts from the forming machine to, for example, a storage area or similar location. The coordination of the movements of the forming machine and the transport device is handled by a shared system control unit. The term "molding machines" can include injection molding machines, injection presses, presses and the like. Various generic arrangements and processes are known. The following describes the state of the art using the production of fiber-reinforced plastics as an example. Processes for manufacturing fiber-reinforced plastics are crucial for the component properties that arise during production. The large number of necessary process steps inevitably leads to an increased potential for defects. While particular attention is paid to quality during process control, process-related quality parameters, such as semi-finished product weight or temperature control, only allow for indirect conclusions about actual defects present in the final component. Therefore, a definitive defect analysis can only be performed at the end of the process with the finished component to prevent the introduction of a defective part into series production. Proof that components were manufactured only with permissible defects and that only these components enter series production is essential. Currently used methods for testing fiber-reinforced plastics include visual, acoustic, thermographic, and electromagnetic methods. Ultrasonic testing is the preferred method in the aerospace industry. In the automotive industry, visual testing is often used for small production runs. Ultrasonic testing can be used on most materials with good surface quality and low complexity. The testing method provides high-resolution defect imaging with depth information. However, a coupling medium, such as water, is required for the test. High component complexity limits this method; for example, the testing of multiply curved structures is only possible to a limited extent. Visual inspection is a very cost-effective method for small production runs, regardless of component geometry. However, this method is limited to the detection of surface defects. Eddy current testing, as an electromagnetic testing method, can in principle be used on all electrically conductive materials and is characterized by short testing times and good automation potential. However, in the case of fiber-reinforced plastics, the method is only suitable for carbon fiber-reinforced plastics, which significantly limits its application in the plastics sector. Thermographic testing methods are divided into active and passive thermography. Passive thermography can be further subdivided into static and dynamic detection of thermal radiation. Heat flow thermography is a dynamic method that analyzes and displays the temporal behavior of the heat flow, thereby generating indirect depth information. The distinction between dynamic passive thermography and active thermography lies in the use of an external energy source. Active thermography is based on the application of external energy, with the simultaneous or subsequent thermal response of the component being evaluated. Examples of excitation sources include eddy current excitation, ultrasonic waves, convective heating, and optical excitation. The excitation itself can be continuous, pulsed, or periodic.When periodic excitation is performed, it is also referred to as lock-in thermography. The application of active thermography and heat flow thermography for plastics using laboratory testing machines is known. However, laboratory experience is limited to thermosetting plastics. Experience with thermoplastic plastics is unknown. Furthermore, reference is made to the revelations in US 2002 / 0153624A1, DE 102009001682A1, DE 60305993T2, DE 60315138T2, DE 102007047776A1, WO 2011 / 137264A1, DE 102007058566A1, DE 2108789A and DE 3307549A1. The object of the invention is to provide an arrangement and a method which allows improved quality control of molded parts manufactured according to the generic criteria. This problem is solved with regard to the arrangement by the features of claim 1 and with regard to the method by the features of claim 11. This is achieved through a thermography station with a thermographic detector for detecting electromagnetic radiation emitted by the molded parts, a molded part fixture in which the molded parts can be positioned using the transport device, and an interface connected to the detector, through which measurement data from the detector and / or quality reports generated from it can be output to the common system control. This enables automatic quality control of all manufactured molded parts shortly after production. Importantly, this occurs in accordance with the production cycle. Therefore, the quality control performed according to the invention does not require any additional time beyond that already necessary for the production of the molded parts. Advantageous embodiments of the invention are defined in the dependent claims. To allow an operator access to the quality information obtained during or after production, it may be possible to store the detector's measurement data and / or the resulting quality reports in a memory of the common plant control system and / or to display them visually. Preferably, the detector can be configured to capture at least one thermographic image per molded part. Particularly preferably, at least two thermographic images can be captured, thus enabling dynamic thermography. To increase the accuracy of thermographic measurements, the thermographic station can include an energy source for heating the molded parts. Increasing the temperature allows background signals to be relatively reduced. It is also possible to vary the amount of heat energy deposited in the molded part over time. Differences in transit time between reactions originating from different locations within the molded part, resulting from defects in the part, can be exploited to further improve accuracy (lock-in thermography). In summary, time-varying heat energy allows for the measurement of relative quantities (e.g., transit time difference) directly on the component. As mentioned, this can lead to increased accuracy. Furthermore, complex calibration processes can be avoided.In particular, this allows for automated error detection, since relative measured values ​​are not, or are much less, affected by the environmental conditions (e.g., outside temperature). For automated defect detection, a defect catalog can preferably be stored in a memory of the shared system control and / or in a memory of the thermographic station. The shared system control and / or the thermographic station are configured to assign quality classes to the molded parts based on the measurement data and to generate a quality report for the molded parts accordingly. In this way, a complete data set with defect information about the produced molded parts can be automatically generated without the need for human intervention. For the simple reuse of the components, at least two separate storage areas can be provided for different quality classes of the molded parts. The common system control is designed to instruct the transport device to move the components to the storage area corresponding to the quality class of the molded parts based on the detector's measurement data and / or the quality reports generated from it. Molded parts of the certain quality classes can then be used accordingly without further sorting or, in the worst case, treated as scrap. An improvement in measurement accuracy can also be achieved through a homogenization station, in which a substantially homogeneous temperature distribution can be produced in the molded parts. The transport device is designed to move the molded parts from the molding machine to the homogenization station and, after homogenization (the creation of a substantially homogeneous temperature distribution) in the homogenization station, to the thermography station. This makes it possible to deliver the molded parts to the thermography station in a precisely defined thermal state. This can be used either in conjunction with an additional heat input in the thermography station—which may vary over time—or as an alternative. In the case of an alternative application, this allows for a relatively simple metrological design, while still achieving very accurate measurement results. If very high accuracy requirements are placed on quality control, the additional use of a homogenization station may be preferable. Since the control systems of modern forming machines are often already designed to handle a variety of different tasks, it can be advantageous to integrate the common system control into the forming machine itself. This eliminates the need for a complex system component. Further advantages and details of the invention are evident from the figure and the accompanying figure description. Figure 1 shows a schematic representation of an arrangement according to the invention, Figure 2 a schematic representation of a thermography station, and Figure 3 a schematic representation of a homogenization station. Figure 1 shows the forming machine 10, which in this embodiment is an injection molding machine with a discharge unit 2 and (for example, a vertical) clamping unit 3. The precise design of the forming machine 10, in particular the clamping unit 3, is, of course, only conditionally essential to the invention. The common plant control unit 1 is shown separately. However, it is intended that this will be integrated into the forming machine 10. A transport device 5, designed as a handling robot, transports the molded parts produced in the molding machine 10 first to the homogenization station 4. Specifically, in this embodiment, the transport device 5 is provided to remove the molded parts directly from the injection molding machine tool. In homogenization station 4, a substantially homogeneous temperature distribution is produced in the molded parts. The homogenization station 4 can utilize convection, conduction, and / or radiation to achieve a homogeneous temperature in the molded parts. Alternatively or additionally to the homogenization station 4, the thermography station can also have a temperature-controlled molded part holder 12. Once this has occurred, the molded parts are transported – again using the transport device 5 – to the thermography station 6. In this case, the thermography station 6 is designed as a thermography cell. This means that the molded part holder 12 is essentially thermally independent of the environment due to an insulated housing, which increases the measurement accuracy of the thermographic detector 11. After inspection in the thermographic station 6, the molded parts are stored – depending on their quality class – in two different storage areas 7 and 8. This transport is also carried out by the transport device 5, which is designed as a handling robot. In this embodiment, the common plant control unit 1 is connected to the various elements of the forming machine 10, the homogenization station 4, and the transport device 5. Furthermore, the common plant control unit 1 is connected to the thermography station 6 via interface 13. It coordinates the various movements and actions of the aforementioned plant components. The embodiment shown in Fig. 1 makes it possible to integrate a final quality control check for fiber-reinforced plastic composites into series production processes. Furthermore, this embodiment allows the manufactured components to be inspected inline (during ongoing production) using dynamic thermography / active thermography in a dedicated system element, in particular a thermographic cell. For this purpose, the thermographic cell sends at least one test value to the machine control. This value can be displayed on the machine control and subsequently assigned to the production process parameters. This allows the component's (molded part's) defect statistics to be stored along with the corresponding process parameter set for each component. Furthermore, this enables the automated removal of excessively defective components from the production run, and ensures that the defect statistics and process parameter set for each component are known throughout its entire lifecycle. The thermographic cell (thermography station 6) of this embodiment operates dynamic thermography, i.e., heat flow thermography and / or active thermography, and is integrated into the production plant, in particular the molding system (molding machine 10), via the control system. This means that all components produced by the molding system are transported to the thermographic cell via the transport device 5 and measured there for a period of time, which is shorter than the time required to manufacture a molded part in the molding system. After the measurement, an image, for example, a phase image or defect image, is calculated from the time-dependent temperature image by a computational algorithm for the evaluation of defects.Subsequently, a second calculation step involves the automated evaluation of the error pattern, whereby an error statistic is calculated and, for example, an error distribution or an individual error value is specified. Alternatively or in addition to the error pattern, an error indicator value can be calculated. Both calculation steps can be performed in either the thermographic station 6 or the shared system control unit 1. In this embodiment, the former option is implemented. The comparison between the calculated error statistics and a predefined reference error statistics then allows the automated transfer of information regarding good versus defective parts. Through a hardware connection of the thermographic cell via interface 13, the error information can be transmitted to the system control 1 integrated into the forming machine 10. There, this error information can be displayed, combined with the component-specific process parameters, and stored. Based on the received information, the forming system can send a signal to the transport device 5 in the event of an error message, in order to remove a defective component from the production run. Furthermore, if multiple components exhibit the same error statistics, the forming system can send an alarm signal and / or stop production.Furthermore, if the same error statistics occur multiple times, the forming system can initiate pre-defined error correction programs, whereby the process parameters for further components to be manufactured are specifically changed so that the components are produced again with the permitted error statistics. In this embodiment, the thermographic cell operates in the form of heat flow thermography or in the form of active thermography, but in any case dynamically. A corresponding fault catalog, in which faults are classified according to their type and which is stored in a database (memory) accessible to the machine, allows faults recorded by dynamic thermography to be compared with reference faults and automatically classified if they match. The classified fault can then be assigned to the component and stored in the component data record. Information regarding the fault type is then available for the rejected defective components. The operating mode can be set as follows: • If the components have a homogeneous temperature that is above the ambient temperature, the cooling gradient can be utilized and the thermographic cell can be operated in the form of heat flow thermography. • If the components have a homogeneous temperature and no cooling occurs, the components are actively exposed to an energy input in the thermographic cell. This energy input performs the active thermography. • If the components have a homogeneous temperature that is above the ambient temperature and cooling would naturally occur, the components are placed in a temperature-controlled station where the active thermography takes place. • If the component has a heterogeneous temperature distribution after cooling, it may be necessary to bring the component to a homogeneous temperature so that active thermography can be performed without errors.Temperature homogenization is performed in homogenization station 4. In this station, the components can be either heated or cooled in a targeted manner. Furthermore, homogenization station 4 can also temporarily store the components for a certain period to allow the temperature to equalize throughout the entire component. The components can then be transported to the active thermography cell and examined using active thermography. If the component has a heterogeneous temperature distribution after cooling, and the component's temperature gradient is locally known, dynamic thermography can be performed as heat flow thermography without the intermediate homogenization station 4. However, this requires that the material's temperature gradient be experimentally determined for different temperature levels (component and environment).(Of course, in the specific case, the assignment to the predefined values ​​must then be possible.) Alternatively, the temperature gradient can be calculated based on the heterogeneous actual temperature of the component and the known ambient temperature. By comparing the reference gradient with the actual gradient that arises locally during temperature equalization, the deviation can be evaluated and conclusions drawn about errors. The energy input for operating active thermography can be achieved, among other things, through the following excitation sources: • IR emitters • Flash lamps • Halogen spotlights • Ultrasonic excitation • Contact heating • Warm air • Laser In heat flow thermography, the residual heat in the component is used. Fig. 2 shows a thermographic station 6 as used in an arrangement according to the invention. The transport device 5 positions the molded parts in the molded part holder 12. In this embodiment, the molded parts are positioned under a housing 15 such that a thermal shield is essentially formed by a support element 16 of the transport device 5 and the housing 15. Furthermore, in addition to the detector 11, two energy sources 14 are provided, enabling active thermography to be performed with this thermography station 6. In this embodiment, the energy sources 14 are designed as infrared emitters. Figure 3 shows a homogenization station 4 as used in an arrangement according to the invention. The molded parts are introduced between two heat sources 15 by means of the transport device 5. In this embodiment, these are designed as infrared radiators. If the molded parts remain in this homogenization station 4 for a certain period of time, a substantially constant temperature distribution is established. The invention is not limited to the embodiments shown here. For example, it is not essential that the heat sources 15 of the homogenization station 4 are designed as infrared emitters. Likewise, the number of system components, in particular the forming machines, transport devices, homogenization stations, and thermographic stations, can be adapted to the respective manufacturing process.

Claims

Arrangement for the provision of molded parts, comprising a molding machine (10) for the production of the molded parts, a transport device (5) for the molded parts, and a common system control (1) for the molding machine (10) and the transport device (5), wherein: - a thermographic station (6) with a thermographic detector (11) for detecting electromagnetic radiation emitted by the molded parts and an energy source (14) for heating the molded parts, - a molded part holder (12) in which the molded parts can be positioned by means of the transport device (5), and - an interface (13) connected to the detector (11) by means of which measurement data from the detector (11) and / or quality reports generated therefrom can be output to the common system control (1), characterized in that the energy source (14) is configured toto vary the thermal energy deposited in the molded part over time and the thermographic station (6) and / or the joint system control (1) is designed to store the presence of a quality defect of the molded parts in conjunction with data for the identification of the molded parts in a memory in the event of a difference in the runtime of the reactions originating from different locations of the molded parts to the time-varying introduced thermal energy. Arrangement according to claim 1, characterized in that the measurement data of the detector (11) and / or the quality reports generated therefrom can be stored in a memory of the common plant control (1) and / or be visually represented. Arrangement according to one of claims 1 to 2, characterized in that the detector (11) is configured to take at least one thermographic image, preferably at least two thermographic images, per molded part. Arrangement according to one of claims 1 to 3, characterized in that the energy source comprises at least one of the following devices: infrared emitter, flash lamp, halogen spotlight, ultrasound source, contact heater, hot air source, laser. Arrangement according to one of claims 1 to 4, characterized in that a fault catalog is stored in a memory of the common plant control (1) and / or in a memory of the thermography station (6), wherein the common plant control (1) and / or the thermography station (6) are configured to assign quality classes to the molded parts based on the measurement data and to issue a quality report for the molded parts on the basis of this. Arrangement according to one of claims 1 to 5, characterized in that at least two separate storage areas (7, 8) are provided for different quality classes of the molded parts, wherein the common system control (1) is configured to cause the transport device (5) to transport the components to the storage area (7, 8) corresponding to the quality classes of the molded parts based on the measurement data of the detector (11) and / or the quality reports generated therefrom. Arrangement according to one of claims 1 to 6, characterized in that a homogenization station (4) is provided in which a substantially homogeneous temperature distribution in the molded parts can be produced, and the transport device (5) is designed to transport the molded parts to the homogenization station (4) after production in the molding machine (10) and to the thermography station (6) after homogenization in the homogenization station (4). Arrangement according to one of claims 1 to 7, characterized in that the transport device (5) is designed as a handling robot. Arrangement according to one of claims 1 to 8, characterized in that the common system control (1) is configured to control or regulate the forming machine (10), the transport device (5) and functions of the thermography station (6). Arrangement according to one of claims 1 to 9, characterized in that the common plant control (1) is integrated into the forming machine (10). Method for providing molded parts, wherein: - the molded parts are produced in the molding machine (10), - the molded parts are positioned in a thermographic station (6) by means of a transport device (5), - the molded parts are heated by means of an energy source (14), - electromagnetic radiation emitted by the molded parts is detected by a thermographic detector, and - measurement data from the thermographic detector (11) and / or quality reports generated therefrom are supplied to a common system control (1) for the molding machine and the transport device (5), characterized in that the heat energy deposited in the molded part by means of the energy source (14) is varied over time, and if there is a difference in the runtime of the reactions from different locations of the molded parts to the time-varying heat energy introduced, a conclusion is drawn about the presence of a quality defect in the molded parts.

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