Method and device for producing a plate-shaped workpiece

Abstract

The invention relates to a method for producing a plate-shaped workpiece (W), in particular a wood-based panel, comprising at least the following method steps: A) introducing a raw material (R) provided with a binder into a pressing device (4); B) by means of the pressing device (4), pressing the raw material (R) provided with binder in order to produce the plate-shaped workpiece (W); C) discharging the plate-shaped workpiece (W) from the pressing device (4); D) testing the plate-shaped workpiece (W) by means of an ultrasonic testing device (8) and producing an ultrasonic test signal; and E) adjusting at least one process parameter of the pressing device (4) depending on the ultrasonic test signal.

Description

[0001] title

[0002] Method and apparatus for manufacturing a plate-shaped workpiece

[0003] Description

[0004] The industrial production of sheet-like workpieces often involves a multi-stage processing of raw materials. These raw materials can be loose synthetic or wood-based materials, which are mixed with a binder and pressed into a sheet workpiece using force and heat.

[0005] Depending on the origin and processing of the raw material, its properties can vary. This can lead to correspondingly fluctuating properties in the manufactured workpieces, which can negatively impact their quality. Furthermore, the production of these sheet-shaped workpieces utilizes equipment and devices whose operation involves a multitude of process parameters, which, depending on their settings, also influence the quality of the workpieces.

[0006] One challenge lies in the fact that the aforementioned influences on the quality of a sheet-shaped workpiece can interact with one another. This means that considerable effort is required to adjust the relevant process parameters in such a way that a high quality rate can be achieved even with fluctuating raw material properties.

[0007] It is an object of the invention to propose a method and a device with which a consistently high quality rate can be achieved for the production of plate-shaped workpieces despite fluctuating properties of the raw material used. This object is achieved by a method according to claim 1 and a device according to claim 10. Advantageous embodiments are the subject of dependent claims.

[0008] The method according to the invention serves to produce a plate-shaped workpiece and comprises the following process steps:

[0009] A) Introducing a raw material containing a binder into a pressing device;

[0010] B) Pressing the raw material containing the binder into the plate-shaped workpiece using the pressing device;

[0011] C) Ejecting the plate-shaped workpiece from the press;

[0012] D) Testing the plate-shaped workpiece using an ultrasonic testing device while generating an ultrasonic test signal;

[0013] E) Adjusting at least one process parameter of the pressing device depending on the ultrasonic test signal.

[0014] The invention is based on the finding that the use of an ultrasonic testing device makes it possible to reliably determine at least one quality-relevant workpiece property and, depending on this, to control the operation of the pressing device in order to positively influence the quality of subsequent workpieces.

[0015] The raw material can be a wood-based material produced in the form of wood fibers, wood chips, wood shavings, wood particles, or a combination thereof. The binder can be in powder or liquid form and may, for example, comprise a resin, in particular a urea-formaldehyde resin (UF resin), a phenol-formaldehyde resin (PF resin), a melamine-formaldehyde resin (MF resin), or an isocyanate resin. The workpiece to be produced may be a particleboard, a medium-density fiberboard (MDF), or an oriented strand board (OSB). It is also within the scope of the invention for the raw material to comprise a plastic, which may be in the form of plastic fibers or plastic particles, for example, based on carbon, glass, or aramid. The binder may be a resin, in particular an epoxy resin, polyester resin, vinyl ester resin, polyurethane resin, or a phenolic resin.The workpiece to be manufactured can therefore be a plastic fiber composite component.

[0016] The pressing device can be any type of press, including both continuous and discontinuous presses. Advantageously, the raw material containing the binder can be heated before or during pressing, which activates the binder, preferably melting it.

[0017] The workpiece removal process can include taking the manufactured workpiece out of the press. This can be done manually and / or automatically.

[0018] The workpiece is inspected, as described above, using an ultrasonic testing device. Such a device can comprise at least one ultrasonic transmitter and at least one ultrasonic receiver. The inspection is based on the principle that a sound signal, with a frequency between 20 kHz and 1 GHz, is emitted by the transmitter towards the workpiece and reflected or transmitted by the workpiece towards the receiver. By evaluating the reflected or transmitted ultrasonic signal with the receiver, a quality-relevant component property can be determined, and at least one process parameter of the press can be adjusted accordingly. The ultrasonic test signal can be, in a simple way, an electrical voltage output by the receiver.However, it is also conceivable that the ultrasound test signal depends on an electrical excitation signal, by means of which the ultrasound transmitter unit is controlled.

[0019] It is also within the scope of the invention that the ultrasonic testing device comprises a single oscillating element which serves both to generate a sound signal and to measure a reflection signal, and which essentially relies on the same operating principle described above. It is also within the scope of the invention that such an oscillating element is connected to an electrical resonant circuit, which serves to set the oscillating element into mechanical vibration and thereby generate the sound signal at a corresponding frequency. A reflection of this sound signal from the workpiece or a defect located therein can superimpose itself on the vibration of the oscillating element, which measurably affects the resonant frequency of the resonant circuit, so that excitation of the oscillating element and measurement of a vibration characteristic are possible with or without a time delay, and thus a defect can be identified.

[0020] In particular, the detected quality-relevant component property can be reflected in a surface and / or internal workpiece feature and / or property, which can be reliably detected using the ultrasonic testing device. Therefore, the use of the ultrasonic testing device makes it possible to control or regulate the pressing device directly based on the manufactured workpiece features. It is within the scope of the invention that the term "ultrasonic testing device" can encompass both a testing device and a measuring device.

[0021] It is within the scope of the invention that the ultrasonic transmitter and receiver units can be positioned relative to the workpiece in a reflection arrangement and / or in a transmission arrangement. Likewise, it is within the scope of an advantageous embodiment that the ultrasonic testing device can comprise a plurality of ultrasonic transmitters and / or receiver units, which can be arranged in a combination of reflection and transmission configurations.

[0022] Preferably, the ultrasonic test signal from the ultrasonic testing device is transmitted to a control module, which processes the ultrasonic test signal and outputs a control signal to automatically adjust the process parameter, particularly within a predefinable control range.

[0023] Advantageously, the ultrasonic testing device, or preferably its ultrasonic transmitter and / or receiver unit, is movably mounted and is moved relative to the workpiece, particularly during testing of the plate-shaped workpiece. Preferably, the movement of the ultrasonic testing device occurs at least partially along and / or transversely to a conveying direction of the workpiece during its conveying movement. Preferably, the movement of the ultrasonic testing device follows a path and preferably includes at least one reversal of direction, so that a periodic movement of the ultrasonic probe is generated along the path. In particular, the movement of the ultrasonic testing device and the conveying movement of the workpiece can be superimposed. It is also conceivable that the conveying movement of the workpiece is stopped for the ultrasonic testing.

[0024] In particular, the ultrasonic testing device is integrated inline with respect to the pressing device. With respect to the workpiece flow, the ultrasonic testing device is arranged downstream of the pressing device. This makes it possible, in principle, to examine all workpieces produced within a given time period with regard to one or more test characteristics and to adjust the process parameters of the pressing device accordingly. In an advantageous embodiment, the pressing device is designed as a continuous press, wherein, at least in process step B), the pressing of the raw material containing the binder takes place at a variable process speed, and in process step E), the process speed of the continuous press is adjusted depending on the ultrasonic test signal.

[0025] As part of an advantageous further development, a continuous press can comprise two endlessly circulating belts that enclose a pressing area in which the raw material containing binder is pressed into the plate-shaped workpiece.

[0026] The pressing area can thus be considered a spatial region enclosed between the two belts, which are compressed under force by means of them. A heat source can be arranged upstream and / or within the pressing area in relation to the conveying movement in order to thermally activate the binder, preferably to melt it.

[0027] Preferably, the two belts in those sections which limit the pressing area are set in a coherent relative movement in order to convey the pressed workpiece along a conveying direction and to discharge it as a result of the feed movement.

[0028] The process speed of a continuous press can refer to the speed at which the binder-coated raw material, or a portion thereof, is conveyed through the pressing area. In particular, the process speed depends on the belt speeds of both belts enclosing the pressing area.

[0029] The belts can each be driven by at least one drive roller, allowing the process speed to be adjusted based on the rotational speeds of the drive rollers. In particular, an advantageous embodiment allows the process speed to be adjusted by changing the belt speeds of both belts or by adjusting one of the belts. Specifically, the belt speeds can be identical or different. Preferably, the belts in the pressing area are not oriented parallel to each other, but rather form an acute angle that opens against the conveying direction of the raw material and / or workpiece. This allows for optimal feed of the raw material and, in particular, its distribution between the belts.

[0030] Studies have shown that the process speed of a continuous press is directly related to productivity in the production of sheet-like workpieces. Furthermore, the process speed also influences the quality rates of the workpieces produced. In particular, the process speed cannot be set arbitrarily high if a predetermined quality level is to be maintained. Likewise, the process speed cannot be set arbitrarily low in order to achieve the desired output rates for the productive manufacture of sheet-like workpieces.

[0031] While it is possible to determine an optimal process speed analytically or experimentally based on a desired ratio of output to quality rates, studies have also shown that fluctuating material parameters and influences from the manufacturing environment have a significant impact on these target variables. Consequently, the optimal process speed can vary between different workpieces or batches. Adjusting the process speed of a continuous press based on the ultrasonic test signal measured on a finished workpiece provides a simple and reliable way to define an optimal operating condition that takes these influences into account.

[0032] It is within the scope of advantageous further training that the adjustment of the process speed depending on the ultrasonic test signal takes place within the framework of a process control or process regulation.

[0033] In an advantageous further development, the ultrasound test signal in process step D) depends at least on a defect and / or a defect property.

[0034] The further training described above is based on the understanding that an unsuitably set process parameter of a pressing device, particularly the process speed of a continuous press, has a strong influence on the occurrence and severity of defects. A defect can be defined as any deviation of a tested workpiece characteristic or property from its required state. Such a deviation can be superficial, i.e., directly on a visible side of the manufactured workpiece, or internal, i.e., between two visible sides of the workpiece.

[0035] The use of an ultrasonic testing system offers the advantage of detecting both surface and internal defects. For example, the ultrasonic testing system can include an ultrasonic distance sensor, which can be positioned relative to the workpiece in such a way that a surface profile or workpiece dimension can be measured without contact. Additionally or alternatively, the ultrasonic testing system can include an ultrasonic test sensor that enables the detection of internal defects. In particular, the ultrasonic test sensor can be air-coupled to the workpiece. This eliminates the need for a liquid coupling medium to couple an ultrasonic signal into or out of the workpiece for testing.It is conceivable that the defect is at least partially caused by a depression and / or a raised area and / or a crack and / or a delamination and / or swelling. Investigations have shown that the aforementioned defects can be reliably detected using an ultrasonic testing device and may be caused, in particular, by a suboptimally set process speed of a continuous press. Swelling can occur, in particular, as a result of steam formation within the workpiece during pressing, especially when heat is applied.

[0036] In an advantageous further development, the process parameter, in particular the process speed of the continuous press, is set as a function of a signal transit time and / or a signal amplitude and / or a phase position and / or a signal frequency and / or an attenuation value of the ultrasonic test signal.

[0037] In one conceivable embodiment, the ultrasound signal can be in the form of an electrical voltage or a quantity dependent thereon, which can be used to determine the aforementioned measured quantities or to define the ultrasound test signal at least partially itself.

[0038] A signal propagation time can be determined, for example, by comparing the time profiles of a control signal from an ultrasonic transmitter and an ultrasonic test signal from an ultrasonic receiver. The signal propagation time indicates the minimum time an ultrasonic signal requires to penetrate a workpiece at one surface, pass through it, and be reflected or transmitted at an opposite surface. If the workpiece being tested has defects, the ultrasonic signal is affected in such a way that its propagation time changes. A delay or increase in propagation time compared to a defect-free workpiece thus allows conclusions to be drawn about an internal or external defect.

[0039] The signal amplitude can be determined from the ultrasonic test signal and can provide information about the size or type of a defect. A larger defect often leads to a reduction in the signal amplitude of an ultrasonic test signal compared to a defect-free workpiece. Investigations by the applicant have shown that a defect is typically associated with an air-material interface, which results in a reduced signal amplitude compared to a defect-free workpiece.

[0040] By comparing the phase of a detected ultrasonic test signal with the transmitted ultrasonic signal, information about the location of the defect in the material can be obtained. Analyzing the phase shift allows the precise determination of the defect's location within the workpiece.

[0041] The frequency of the ultrasonic test signal can be evaluated to classify different types of defects. For example, ultrasonic test signals with a comparatively low frequency have a greater penetration depth into the surface of a workpiece under test, making larger defects detectable, while comparatively high frequencies have a shallower penetration depth and may be suitable for detecting defects in smaller surface areas of the workpiece. It is conceivable that the ultrasonic test signal could be compared with a reference signal or information derived from it to determine information about a defect. The reference signal could exhibit a characteristic profile, particularly with regard to amplitude and / or frequency, depending on the defect and / or its characteristics.In particular, the reference signal can be determined experimentally using a reference workpiece with introduced defects whose properties are known, or by means of a virtual simulation model.

[0042] The attenuation of the ultrasonic signal during its passage through the workpiece can be determined as an attenuation value and may indicate the presence of internal defects, in particular swelling, cracks, delaminations or porosity.

[0043] In an advantageous further development, the ultrasonic test signal is pre-processed in a process step D1) and evaluated in a process step D2) before the process parameter of the press device is set.

[0044] Preprocessing of the ultrasound test signal can include filtering, signal amplification, envelope detection, threshold determination, temporal and / or spatial synchronization, equalization, noise reduction, or the detection, smoothing, and / or extraction of signal components.

[0045] Filtering can involve the application of a low-pass and / or high-pass filter to eliminate high-frequency or low-frequency noise, respectively. A band-pass filter can also be used to restrict the ultrasonic test signal to a specific frequency band. A notch filter can also be used to remove interference at certain frequencies that could impair the ultrasonic test signal.

[0046] Signal amplification can be advantageous to improve the signal-to-noise ratio of the ultrasonic test signal. This can be achieved through simple analog or digital amplification. Automatic gain control (AGC) allows the signal amplification to be dynamically adjusted to the signal strength to ensure consistent output power. Envelope detection can be performed to determine the envelope of the ultrasonic test signal. This allows only the signal amplitude to be determined, independent of any interfering carrier frequency. This enables more precise signal analysis, particularly when detecting reflected ultrasonic signals.

[0047] Threshold determination allows for the setting of threshold values ​​to distinguish an ultrasound test signal from background noise. Signals exceeding the threshold are considered relevant, while signals below it are regarded as noise or interference and can be ignored.

[0048] Synchronization can also be advantageous, especially for measurements based on transit time, such as ultrasonic distance measurement. Here, a transmitted and received signal are synchronized in time to enable an accurate determination of the transit time.

[0049] Equalizing the signal can be advantageous to correct signal distortions that may occur, for example, as a result of signal transmission. This can be achieved by applying correction algorithms.

[0050] Additionally or alternatively, noise reduction techniques can be used to reduce background noise and further improve signal quality. These include averaging techniques, adaptive filtering, and other methods for reducing interference.

[0051] Signal components can be identified to define a so-called region of interest for the ultrasonic test signal, which then serves as the basis for signal evaluation. This reduces the required evaluation time and capacity, particularly when using an electronic processing unit, by analyzing only a portion of the acquired ultrasonic test signal. Specifically, signal components outside the region of interest can be excluded from signal processing or processed using one of the methods described above to improve signal quality for subsequent analysis.

[0052] In an advantageous further development, the ultrasonic test signal for carrying out process steps D1) and D2) is transmitted from the ultrasonic test device to a control module, which preprocesses and evaluates the ultrasonic test signal and outputs a control signal for carrying out process step E) in order to automatically adjust the process parameter and in particular within a predefinable control range.

[0053] One advantage of the aforementioned advanced training is that the ultrasonic test signal can be automatically evaluated to ensure optimal operation of the press. In particular, at least process steps D) and E) can be performed as part of a control loop, with the control loop having a control cycle lasting less than 5 minutes.

[0054] Studies have shown that, particularly when using continuous presses, a control cycle duration should not exceed 5 minutes to achieve a good control result. Preferably, an artificial intelligence-based algorithm is used to adjust the process parameters of the press device depending on the ultrasonic test signal.

[0055] It is within the scope of the invention that the control module comprises a computing unit and a control unit, wherein the computing unit serves for the preprocessing and evaluation of the ultrasonic test signal and outputs an evaluation signal to the control unit, and wherein the control unit serves to control the pressing device. The computing unit and the control unit can be functionally independent of each other or combined into a functionally integrated control module, for example in the form of a microcontroller.

[0056] In an advantageous further training, the output of the ultrasound test signal from process step D) is monitored.

[0057] Monitoring the output of the ultrasonic test signal can improve the reliability of the control or regulation of the pressing device. This monitoring can check at least one signal output of the ultrasonic test device and / or a signal connection between the ultrasonic test device and a processing unit and / or a signal input of the processing unit for conformity and / or deviations of one or more ultrasonic test signals from a predefined standard. This ensures, for example, that the ultrasonic test signal is output by the ultrasonic test device with the required frequency and / or signal strength.If an undesirable deviation from the specified standard is detected, a safe operating mode for the press can be initiated, for example, by setting at least the process parameter to a predetermined target value. It can also be advantageous to switch the operation of the press from automated to manual control. In a simpler embodiment, a warning signal can also be issued, depending on which a suitable process control measure can be initiated.

[0058] Monitoring of the ultrasonic test signal output can be carried out using the aforementioned computing unit or by means of a separate monitoring system, which in particular includes a signal analyzer that is at least indirectly connected to the ultrasonic testing device. As described above, the problem is also solved by means of a device for producing a plate-shaped workpiece, in particular a wood-based panel. The device includes a pressing device, which is designed to press a raw material containing a binder into the plate-shaped workpiece and to dispense the plate-shaped workpiece.Furthermore, the device includes an ultrasonic testing device, which is arranged to test the plate-shaped workpiece produced by means of the pressing device and to output an ultrasonic test signal to a control module, which is configured to adjust at least one process parameter of the pressing device depending on the ultrasonic test signal.

[0059] Preferably, the device is configured to carry out the method according to the invention or an advantageous embodiment thereof. Preferably, the method according to the invention or an advantageous embodiment thereof can be carried out using the device according to the invention or one of its advantageous embodiments. With regard to the device, the descriptions of the embodiments of the method and the associated advantages apply accordingly.

[0060] In a further advantageous embodiment, the pressing device is at least partially designed as a continuous press with a variable process speed, wherein the control module is configured to adjust the process speed depending on the ultrasonic test signal. An advantage achievable through this is the automated control of the pressing device.

[0061] In an advantageous embodiment, the ultrasonic testing device is arranged in an output area of ​​the press and comprises at least one ultrasonic probe, preferably several ultrasonic probes arranged in an array. By arranging the ultrasonic probe in the output area, process control can be achieved based on already output workpieces, thus positively influencing the quality of subsequently produced workpieces.

[0062] Arranging ultrasonic transducers in an array offers the advantage of enabling the area-wide inspection of workpieces. Such an array can have various configurations. For example, several ultrasonic transducers can be arranged along a straight axis, forming a line array. This line array can preferably be positioned orthogonally to the conveying direction of the workpiece with respect to its axis of extension. It is also conceivable that the line array is arranged at an angle between 0° and 90° to the conveying direction. Area-wide inspection of the flat workpiece is possible due to the relative movement between the line array and the workpiece. Alternatively, the ultrasonic transducers can be configured as a matrix array, distributed along two axes of extension.A higher information density can be achieved compared to a line array.

[0063] In an advantageous further development, the control module comprises a computing unit and a control unit. The ultrasonic testing device is connected to the computing unit via a signal connection, and the computing unit is configured to preprocess and evaluate the ultrasonic testing signal and, depending on this, output a control signal to the control unit, which is configured to set the process parameters of the pressing device.

[0064] In an advantageous embodiment, the ultrasonic testing device is connected to the control module via a data link, and the control module is configured to monitor this data link. Preferably, an artificial intelligence-based algorithm is implemented on the control module to adjust the process parameters of the pressing device based on the ultrasonic testing signal.

[0065] The advantages of the invention are explained below with reference to exemplary embodiments and a figure.

[0066] They show

[0067] Figure 1 shows a first device for producing wood-based panels;

[0068] Figure 2 shows a second device for producing

[0069] Wood-based panels in two views a) and b).

[0070] In the industrial production of sheet-like workpieces, it is typically desirable to achieve both a high output rate and a high quality rate of the manufactured sheet components. However, a challenge lies in the fact that the output rate cannot be increased indefinitely without negatively impacting the achievable quality. Furthermore, if the manufactured workpieces are wood-based panels, another challenge can arise from the need to adjust a process parameter, initially determined to be optimal, due to fluctuations in the raw material properties, in order to avoid negative effects on the quality rate.

[0071] The devices shown in Figures 1 and 2 make it possible to forgo complex process optimization in the production of wood-based panels.

[0072] The device 1 shown in Figure 1 comprises a press 2 by means of which a raw material R containing a binder is processed into a workpiece W. The press 2 is designed as a continuous press and comprises two endlessly circulating belts 3 and 4.

[0073] To produce the wood-based panel W, the binder-coated raw material R is placed on belt 3 in an infeed section of the device 1. A feed motion along the conveying direction 5 carries the raw material R into a pressing section bounded by the two belts 3 and 4. Belts 3 and 4 are each set in relative motion by a driven deflection roller, with the surface velocities 6 and 7 of belts 3 and 4, respectively, oriented in the same direction. Due to the inclined position of the belt sections of belts 3 and 4, the raw material R is conveyed along the conveying direction 5 and simultaneously compacted, thus forming the wood-based panel W.

[0074] The wood-based panel W is brought into a discharge area by the movements of the belts 3 and 4, in which an ultrasonic testing device 8 is arranged. In the embodiments shown here, the ultrasonic testing device 8 has several ultrasonic probes, each comprising an ultrasonic transmitter and an ultrasonic receiver. The ultrasonic probes of the ultrasonic testing device 8 are arranged in a line array (not shown in detail here), the axis of which extends into the plane of the image and is orthogonal to the conveying direction 5.

[0075] In the embodiment shown here, the ultrasonic probes of the ultrasonic testing device 8 are positioned in a reflection arrangement such that the ultrasonic transmitter and receiver of one of the probes are located on the same side as the workpiece W. For testing the workpiece W, a sound signal with a frequency between 20 kHz and 1 GHz is emitted towards the workpiece W and reflected back towards the ultrasonic receiver. By evaluating this ultrasonic test signal, conclusions can be drawn about a quality-relevant component property and...

[0076] Depending on this, the process speed of device 1 can be adjusted.

[0077] To enable such control of the device 1, the device 1 has a control module 9 which is connected to the ultrasonic testing device 8 via signal technology and is configured to evaluate ultrasonic test signals and, depending on these, to adjust the rotational speeds of the deflection rollers that drive the belts 3 and 4. The process speed can specify the speed at which the raw material R passes through the pressing area.

[0078] The use of the ultrasonic testing device 8 makes it possible to detect both external defects on the manufactured workpiece and those that are internal, i.e., partially or completely enclosed between the workpiece surfaces.

[0079] External defects can be caused, for example, by a depression or protrusion on the surface of the workpiece. Such external defects can include, for example, cracks and can be detected using the reflection arrangement shown here, particularly on the side of the workpiece facing the ultrasonic testing device 8. Internal defects can be caused, for example, by a crack and / or delamination and / or swelling. Such internal defects can also be detected using the ultrasonic testing device 8 in a reflection arrangement shown in Figure 1. However, it has also proven advantageous to use an ultrasonic testing device 8 in a transmission arrangement for the detection of internal defects, as shown by way of example in Figure 2.

[0080] Control module 9 comprises, in a manner not shown here, a processing unit and a control unit. The processing unit is designed to preprocess and evaluate the ultrasonic test signal. The processing unit outputs a control signal to the control unit, which automatically adjusts the process speed within a predefined control range. Also in a manner not shown here, the processing unit and the control unit can be combined within the control module to form a functionally integrated unit, for example, a microcontroller.

[0081] The preprocessing of the ultrasonic test signal includes filtering to reduce unavoidable signal fluctuations over time, thus improving its interpretability. However, preprocessing can also encompass signal amplification, envelope detection, threshold determination, temporal and / or spatial synchronization, equalization, noise reduction, or the identification, smoothing, and / or extraction of signal components.

[0082] The ultrasonic testing device 8 is connected to the control module 9 via a data connection. In addition to preprocessing and evaluating the ultrasonic test signal, the control module's processing unit is also configured to monitor the data connection. This makes it possible to detect a failure in the data connection and to put the device 1 into a safe state in which no process parameter is changed or, alternatively, it is set according to a defined setpoint.

[0083] In addition, an algorithm based on artificial intelligence is set up on the control module 8 to adjust the process parameters of the press device, in particular the process speed, depending on the ultrasonic test signal.

[0084] According to the embodiment of the device 1 shown in Figure 2, the components of the ultrasonic testing device 8 are positioned relative to the workpiece W in a transmission arrangement. This is illustrated in view a) of Figure 2. The ultrasonic transmitter unit and the ultrasonic receiver unit of the ultrasonic testing device are arranged on opposite sides of the workpiece W. For this purpose, the belt 3 is designed such that, with respect to the conveying direction 5, it does not extend further than the press section. In the discharge section, a conveyor belt 10 is arranged, which is interrupted in a central area and receives the discharged workpiece W in two edge areas. This is shown in view b) of Figure 2.

[0085] The interrupted central section of the band 10 allows the workpiece to be tested using the ultrasonic testing device 8 in a transmission arrangement without the band 10 interfering with the ultrasonic test signal. Furthermore, the descriptions in Figure 1 apply accordingly.

Claims

Claims 1. Method for producing a plate-shaped workpiece (W), in particular a wood-based panel, comprising at least the following process steps: A) Introducing a raw material (R) containing a binder into a pressing device (4); B) Pressing the raw material (R) containing the binder using the press (4) to produce the plate-shaped workpiece (W); C) Ejecting the plate-shaped workpiece (W) from the press (4); D) Testing the plate-shaped workpiece (W) using an ultrasonic testing device (8) and generating an ultrasonic test signal; E) Adjusting at least one process parameter of the pressing device (4) depending on the ultrasonic test signal.

2. Method according to claim 1, wherein the pressing device (4) is designed as a continuous press, wherein at least in process step B) the pressing of the raw material (R) provided with binder is carried out with a variable process speed and in process step E) the process speed of the continuous press (4) is adjusted depending on the ultrasonic test signal.

3. Method according to claim 1 or 2, wherein the ultrasonic test signal in method step D) depends on at least one defect and / or a defect property.

4. Method according to claim 3, wherein the defect is formed at least partially by a depression and / or a protrusion and / or a burst and / or a crack and / or a delamination and / or a swelling.

5. Method according to one of the preceding claims, wherein the process parameter is set as a function of a signal transit time and / or a signal amplitude and / or a phase position and / or a signal frequency and / or an attenuation value of the ultrasonic test signal.

6. Method according to claim 5, wherein the ultrasonic test signal is pre-processed in a process step D1), in particular filtered, and evaluated in a process step D2) before the process parameter of the press device (4) is set.

7. Method according to claim 6, wherein the ultrasonic test signal is transmitted from the ultrasonic test device to a control module (9) for carrying out process steps D1) and D2), which preprocesses and evaluates the ultrasonic test signal and outputs a control signal for carrying out process step E) in order to automatically adjust the process parameter and in particular within a predefinable control range.

8. Method according to one of the preceding claims, wherein at least the method steps D) and E) are carried out as part of a control loop, the control loop preferably having a control cycle with a duration of less than 5 minutes.

9. Method according to claim 8, wherein an output of the ultrasonic test signal from method step D) is monitored.

10. Device (1) for producing a plate-shaped workpiece, in particular a wood-based panel (W), with a pressing device (4) which is designed to press a raw material (R) containing a binder into the plate-shaped workpiece (W) and to dispense the plate-shaped workpiece (W), and with an ultrasonic testing device (8) which is arranged to test the plate-shaped workpiece (W) produced by means of the pressing device (4) and to output an ultrasonic test signal to a control module (8) which is configured to adjust at least one process parameter of the pressing device depending on the ultrasonic test signal.

11. Device (1) according to one of claims 10, wherein the press device (4) is at least partially designed as a continuous press with a variable process speed and wherein the control module is configured to adjust the process speed depending on the ultrasonic test signal.

12. Device (1) according to claim 10 or 11, wherein the ultrasonic testing device (8) is arranged in a discharge area of ​​the press device (4) and comprises at least one ultrasonic probe, preferably several ultrasonic probes arranged in an array.

13. Device (1) according to one of claims 10 to 12, wherein the control module (9) comprises a computing unit and a control unit, wherein the ultrasonic testing device is connected to the computing unit via a signal connection and the computing unit is configured to preprocess and evaluate the ultrasonic testing signal and, depending on this, to output a control signal to the control unit, which is configured to adjust the process parameter of the pressing device (4).

14. Device according to one of claims 10 to 13, wherein the ultrasonic testing device (8) is connected to the control module (9) by means of a data connection and the control module (9) is configured to monitor the data connection.

15. Device according to one of claims 10 to 14, wherein an algorithm based on artificial intelligence is set up on the control module (9) to adjust the process parameter of the press device depending on the ultrasonic test signal.

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