Method and installation for drying workpieces

Abstract

To provide a method for drying workpieces (106), comprising: - placing at least one workpiece (106) to be dried into a drying chamber (102); - carrying out at least one hot air drying process, in which supply air is supplied to the drying chamber (102) and exhaust air is discharged from the drying chamber (102), wherein fresh air is supplied to the supply air before it enters the drying chamber (102);To create a process that makes it possible to shorten the drying process time and / or save energy required for the drying process by using information from the drying process, it is proposed that the supply of fresh air to the supply air is reduced or interrupted during at least one monitoring period, that at least one measured variable characterizing the drying process is measured by means of at least one sensor (142), and that a measurement signal from the at least one sensor (142) is transmitted to an evaluation unit (154) of a control device (152), and that an output variable is determined from the evaluation of the measurement signal from the at least one sensor (142) by means of the evaluation unit (154), which influences the further course of the process.

Description

[0001] The present invention relates to a method for drying workpieces, wherein the method comprises the following: Placing at least one workpiece to be dried into a drying chamber; and carrying out at least one hot air drying process, in which fresh air is supplied to the drying chamber and exhaust air is extracted from the drying chamber. where fresh air is supplied to the incoming air before it enters the drying chamber.

[0002] Such methods for drying workpieces, which include at least one hot air drying process, are known from industrial component cleaning, see e.g. DE 10 2021 112 211 B4, and represent a central process step in industrial component cleaning.

[0003] Key parameters of the hot air drying process are the temperature of the hot air, the process time of the hot air drying process, and, if necessary, movement of the at least one workpiece to be dried within the drying chamber.

[0004] The temperature or temperature range to be set for the hot air depends on the technical parameters of the drying system used and on the material properties of the workpiece to be dried.

[0005] The process time of the hot air drying process is usually determined by preliminary tests in such a way that the at least one workpiece to be dried is guaranteed to be sufficiently dry after the process time has elapsed.

[0006] It is also known to combine a hot air drying process with a vacuum drying process in a method for drying workpieces. In this case, the hot air drying process is carried out in such a way that the at least one workpiece to be dried is heated sufficiently at the end of the hot air drying process to allow the remaining liquid still present on the workpiece to evaporate during the subsequent vacuum drying process.

[0007] CN 109724398 B discloses a method for drying wood, wherein the condition of the wood and conditions in a drying chamber are detected by sensors and a drying strategy is selected using artificial intelligence.

[0008] US patent 2019 / 0146476 A1 discloses an industrial drying process in which an artificial intelligence receives and monitors data from the process flow.

[0009] The KR 102177970 B1 reveals a tumble dryer in which artificial intelligence evaluates data such as the weight of the laundry before and after the drying process, the water temperature and the load of the tumble dryer.

[0010] Hot air drying is a very energy-intensive process step. A typical heating output of an industrial drying system used for hot air drying is in the range of 20 kW to 30 kW.

[0011] Since the process times for the hot air drying process are always chosen for reasons of process reliability so that the at least one workpiece to be dried is always sufficiently dry and / or sufficiently warm at the end of the process time for a vacuum drying process following the hot air drying process, too much energy is often used for the hot air drying process, resulting in a promising potential for savings.

[0012] In known drying processes that include hot air drying, the drying process is not specifically monitored using measurement technology. The setting of the drying process parameters, particularly the hot air temperature and the drying time, is based solely on the results of preliminary tests and / or empirical data. Quality control of the drying process is either nonexistent or, at most, performed manually in the form of a visual inspection after completion.

[0013] The drying programs of known industrial drying systems are static and cannot react to changing conditions, such as a change in the number of workpieces to be dried, especially if these conditions change during the drying process itself.

[0014] The increasing use of additive manufacturing technologies, such as 3D printing, in the production of workpieces increases the complexity of the workpieces to be dried and, consequently, the demands placed on the drying process. A fixed set of parameters for the drying process often does not correspond to the optimal parameters for the various stages of a drying process with a non-linear drying profile.

[0015] The present invention is based on the objective of creating a method for drying workpieces of the type mentioned above, which makes it possible to shorten the process time for the drying process and / or to save energy required for the drying process by using information from the drying process.

[0016] This problem is solved according to the invention in a method for drying workpieces with the features of the preamble of claim 1 by, that the supply of fresh air to the supply air is reduced or interrupted during at least one monitoring period, at least one measured variable characterizing the drying process is measured by means of at least one sensor, and a measurement signal from the at least one sensor is transmitted to an evaluation unit of a control device, and an output variable is determined from the evaluation of the measurement signal from the at least one sensor by means of the evaluation unit, which influences the further course of the process.

[0017] The determined output variable can be a parameter of the drying process, which is changed as a result of the evaluation of the measurement signal from at least one sensor, or it can be the assessment of whether the at least one workpiece to be dried is sufficiently dry and the drying process can therefore be terminated.

[0018] In this description and in the attached claims, the term "drying chamber" also includes a cleaning chamber in which a cleaning process is first carried out on the at least one workpiece, followed by a drying process. The at least one workpiece to be dried can therefore be cleaned and then dried after being placed in the drying chamber.

[0019] The present invention is based on the concept that at least one sensor for monitoring the drying process transmits data to an evaluation unit and, based on the evaluation of this data by the evaluation unit, the drying process is dynamically controlled.

[0020] In addition, the evaluation unit can also be provided with status data from the drying system used to carry out the process, for example, the operating time of a heating device to heat the supply air, opening and / or closing times of a valve for supplying fresh air or for removing exhaust air, or similar information.

[0021] The evaluation unit preferably implements a process model which includes a rule model and / or an AI (Artificial Intelligence) model for evaluating a drying process.

[0022] The at least one sensor used could be, for example, a humidity sensor that monitors the drying progress.

[0023] Based on the evaluation of the drying progress by the evaluation unit, a parameter such as the fresh air supply, the process time of the hot air drying process and / or a switching cycle of a heating device for heating the supply air can be controlled.

[0024] If the evaluation unit contains an AI model, this AI model can be trained during simulations and / or preliminary tests to optimize target variables such as drying time, drying efficiency and / or energy consumption for drying.

[0025] Such a control model or AI model, for example one trained by the manufacturer of a drying system, can then be used in the evaluation unit of a drying system sold to a customer.

[0026] There is the possibility that the control model or the AI ​​model will be further optimized during the operation of the drying system at the customer's site by recording relevant production data.

[0027] Such optimization can be performed discontinuously, for example, if after collecting a sufficiently large dataset, a new and therefore potentially better AI model is calculated based on this larger dataset.

[0028] Alternatively or additionally, the AI ​​model can be designed to continuously optimize itself by intentionally varying at least one parameter of the drying process slightly and evaluating the impact of such a variation on the drying behavior. Variations that have a positive effect on the drying behavior are then adopted. This approach is also known as "reinforcement learning."

[0029] The method according to the invention enables monitoring of the drying process in order to guarantee consistent quality under changing boundary conditions (such as ambient humidity, workpiece type, workpiece mass, residual water quantity on the workpiece) of the drying process.

[0030] By optimizing the parameters of the drying process, shorter drying times can be achieved.

[0031] Energy savings can be achieved by shortening process times and optimizing parameters of the drying process.

[0032] Preferably, the process model implemented in the evaluation unit, for example a rule model or an AI model, is designed in such a way that it enables a prediction of the drying time still required at a given time until the at least one workpiece to be dried is sufficiently dry.

[0033] The duration of at least one monitoring period can be at least one second and / or at most 4 minutes, preferably at most one minute, particularly preferably at most 30 seconds.

[0034] If a control model is implemented in the evaluation unit, the control device can also regulate between two humidity values ​​and the control process can only be interrupted if an upper limit is exceeded.

[0035] Furthermore, it may be provided that the at least one measured variable characterizing the drying process is measured during a plurality of monitoring periods, whereby the monitoring periods may each be of the same length or may have different lengths from one another.

[0036] When evaluating the at least one measurement signal, for example a minimum and / or a maximum of the measurement signal can be determined and used in determining the output quantity.

[0037] Furthermore, it may be provided that a rate of change of at least one measured quantity is determined and used in the determination of the output quantity.

[0038] Alternatively or additionally, it may also be provided that a rate of change of a sum of at least two measured quantities and / or a rate of change of a difference of at least two measured quantities is determined and used in the determination of the output quantity.

[0039] The at least one sensor may include a humidity sensor, a temperature sensor, a thermal imaging camera for monitoring the temperature of the at least one workpiece to be dried, a pressure sensor and / or a weight sensor for measuring a change in mass of the at least one workpiece to be dried.

[0040] A pressure sensor can be used particularly when a vacuum drying process is carried out as part of the process for drying workpieces.

[0041] Furthermore, the system may include sensors to identify the type of workpiece to be dried. The type of workpiece allows conclusions to be drawn about the amount of residual moisture typically adhering to it. Additionally, the process time required to dry a workpiece is influenced by its geometry, particularly the presence of cavities, blind holes, and similar features.

[0042] In preferred embodiments of the invention, it is provided that at least one sensor measures a measured quantity in the drying chamber, in a supply line for supplying air to the drying chamber, in a discharge line for removing exhaust air from the drying chamber, in an exhaust air line for removing exhaust air from an air circuit, in an evacuation line for connecting the drying chamber to a vacuum source, in an outlet line of a vacuum pump and / or in the environment of the drying chamber.

[0043] A process model is preferably implemented in the evaluation unit.

[0044] The process model can include a rule model and / or an AI model for evaluating a drying process.

[0045] It is particularly advantageous if the process model is designed in such a way that it can change parameters of the drying process during the execution of a drying process or before the execution of a subsequent drying process in order to optimize the drying process.

[0046] The process model is preferably designed in such a way that, based on at least one input parameter transmitted to the evaluation unit, it can determine at least one optimal output parameter for the drying process, wherein the output parameter can be used to control the drying process by the control device.

[0047] In a particular embodiment of the invention, the process model includes an AI model which is designed in such a way that it can optimize itself by changing at least one parameter of the drying process and evaluating the progress of the drying process.

[0048] The process model can be trained and / or optimized in relation to recipes or programs.

[0049] The process model can be given hard limits, for example, a maximum temperature for the drying air. These hard limits can be defined in relation to recipes or programs.

[0050] The process model is preferably designed in such a way that data about the workpieces to be dried can be transmitted to the process model from outside a drying system used for carrying out the drying process, preferably from a pre-process carried out before the drying process or from a central control computer system.

[0051] The preliminary process can be, in particular, a manufacturing process of the workpiece to be dried, especially a 3D printing process, or a machining process on the workpiece to be dried, for example a machining process of the workpiece.

[0052] It is particularly advantageous if the process model is designed in such a way that data about the workpieces to be dried can be transmitted to the process model via sensors, for example a camera, via a barcode, via an RFID chip or by manual data input.

[0053] The sensors, which transmit data about the workpieces to be dried to the process model, especially the AI ​​model, can themselves contain an AI model that can derive workpiece data from the transmitted image information, such as the type of workpiece to be dried, the number of workpieces to be dried, the material from which the workpiece to be dried is made, or similar information.

[0054] Furthermore, it can be provided that the process model is designed in such a way that data about the amount of liquid to be dried from the workpieces to be dried can be transmitted to the process model via a sensor system, which is preferably arranged in the reservoir of a cleaning medium, and / or from a dosing device of a cleaning medium.

[0055] From this data, the process model can draw conclusions about the required process time and the energy required for drying.

[0056] In a preferred embodiment of the invention, it is provided that the process model evaluates the course of the drying process and / or at least one parameter of the drying process can be controlled by the control device based on at least one output of the process model.

[0057] In particular, the evaluation of the process model can be used to determine whether the process time required for sufficient drying of the at least one workpiece to be dried has elapsed.

[0058] The parameters of the drying process that can be changed by the control device based on the evaluation by the process model can, for example, The operation may include changes to the temperature of the drying medium, the heating power of an air conditioning device, the volume flow rate of a drying medium (especially drying air) circulating in an air circuit, the volume flow rate of fresh air mixed with a volume flow rate of the drying medium (especially drying air) circulating in an air circuit, the control of at least one movement device for moving the at least one workpiece to be dried in the drying chamber, the switching on or off of at least one device that supplies energy to the at least one workpiece to be dried in the drying chamber, for example an infrared radiator or a microwave generator, the duration of a drying process and / or a change in the drying method, for example a change from hot air drying to vacuum drying.

[0059] The evaluation of the drying process, which takes place in the evaluation unit, can include the calculation of a difference in moisture values ​​and / or the calculation of a difference in temperature values.

[0060] Where this description or the attached claims refer to a humidity value, this may be a value of relative humidity f, a value of absolute humidity ρ w or a value of specific humidity s.

[0061] The relative humidity f is the ratio of the instantaneous water vapor pressure to the saturation vapor pressure.

[0062] The absolute humidity ρw is the mass of water vapor per volume of air.

[0063] The specific humidity s is the ratio of the mass of gaseous water to the mass of dry air in which the gaseous water is absorbed.

[0064] The difference in humidity values ​​can be, in particular, the difference between the humidity of the exhaust air removed from the drying chamber and the humidity of the supply air introduced into the drying chamber. In this case, the difference in humidity values ​​represents the difference between the air's condition before and after passing through the drying chamber.

[0065] The drying status of at least one workpiece being dried can also be determined from the temperature difference between the exhaust air leaving the drying chamber and the supply air entering it. Since energy is required for the evaporation of moisture from the workpiece, the temperature decreases as the air passes through the drying chamber while moisture is still evaporating or evaporating from the workpiece. For such an assessment of the drying status based on a temperature difference, any heating device for the supply air must be switched off.

[0066] An assessment that the drying process is complete can be generated by an automated control process and / or by input from an operator at the control device.

[0067] The assessment that a workpiece has been sufficiently dried in the drying chamber can be transmitted to the evaluation unit from a process step downstream of the drying process.

[0068] The evaluation unit can be located adjacent to the drying chamber or remotely from the drying chamber, for example in a cloud application.

[0069] In particular, it may be provided that in a process step following the drying process, the quality of the dried workpiece processed further in the subsequent process step is declared as OK or not OK and this assessment is transmitted to the evaluation unit.

[0070] The at least one sensor can transmit its measurement signal to the control device, in particular to the evaluation unit of the control device, via a wired connection.

[0071] Alternatively or additionally, it may also be provided that at least one sensor transmits its measurement signal to the evaluation unit via a wireless connection, for example a WLAN connection, a Bluetooth connection or a radio connection.

[0072] In a particular embodiment of the invention, the supply of fresh air is reduced or interrupted at the beginning of a hot air drying process in order to achieve faster heating of the at least one workpiece to be dried in the drying chamber. In this case, the air is circulated through the drying chamber and through an air conditioning device to heat the air, without cooler fresh air being mixed into this circulating air.

[0073] The heating period, during which the fresh air supply is reduced or interrupted at the beginning of the hot air drying process, can be specified depending on the type and / or number of workpieces to be dried, or determined by the evaluation unit depending on the course of the at least one measurement signal from the at least one sensor.

[0074] Furthermore, in a particular embodiment of the invention, it may be provided that during a hot air drying process the specific humidity s, the absolute humidity ρ w and / or the relative humidity f is kept within a defined range of values ​​by regulating the fresh air supply and / or the heating power of the air conditioning device.

[0075] The optimal range of values ​​for the relevant humidity can be set manually and / or determined by a control model or an AI model implemented in the evaluation unit and preferably changed during the hot air drying process.

[0076] Furthermore, in a particular embodiment of the method according to the invention, it can be provided that after the insertion of the at least one workpiece to be dried into the drying chamber, a vacuum drying process is carried out, then a hot air drying process and afterwards a further vacuum drying process.

[0077] Performing a vacuum drying process before the first hot air drying process boils away moisture from the workpiece's cavities, allowing for more efficient subsequent hot air drying. Multiple cycles can be performed, each comprising one hot air drying and one vacuum drying cycle.

[0078] The present invention further relates to a system for drying workpieces, which comprises the following: a drying chamber; an air circuit comprising a supply line for introducing fresh air into the drying chamber and an exhaust line for removing exhaust air from the drying chamber; and an adjustable fresh air supply for adding fresh air to the supply air before it enters the drying chamber.

[0079] The present invention is based on the further objective of creating such a system for drying workpieces, by means of which a shorter process time and / or a lower energy consumption can be achieved for drying a workpiece.

[0080] To solve this problem according to the invention, the system for drying workpieces further comprises the following: a control device comprising an evaluation unit; and at least one sensor by means of which a measured quantity characterizing the drying process is measured and whose measurement signal can be transmitted to the evaluation unit; wherein the control device is designed in such a way that the supply of fresh air to the supply air is reduced or interrupted during at least one monitoring period and the evaluation unit is designed in such a way that it determines an output variable from the course of the at least one measurement signal of the at least one sensor during the at least one monitoring period, which influences the further course of the drying process carried out by means of the drying system.

[0081] The fresh air supplied to the supply air can be ambient air or another gas or gas mixture, for example, processed high-purity drying air or nitrogen.

[0082] Since the drying air is circulated in an air cycle, the exhaust air removed from the drying chamber becomes the supply air which is fed into the drying chamber, whereby fresh air may have been added to the supply air or part of the exhaust air may have been removed.

[0083] Special embodiments of the inventive system for drying workpieces have already been explained above in connection with special embodiments of the inventive method for drying workpieces.

[0084] The inventive system for drying workpieces is particularly suitable for carrying out the inventive method for drying workpieces.

[0085] The inventive method for drying workpieces is preferably carried out using the inventive system for drying workpieces.

[0086] Further features and advantages of the invention are the subject of the following description and the graphic representation of an exemplary embodiment.

[0087] The drawings show: Fig. 1 is a schematic representation of a drying system by means of which hot air drying and vacuum drying of at least one workpiece arranged in a drying chamber can be carried out; and Fig. 2 is a diagram illustrating a drying process using the system shown in Fig. 1 The drying system shown depicts a time course of a measured relative humidity.

[0088] Identical or functionally equivalent elements are designated with the same reference symbols in all figures.

[0089] A in Fig. 1 The drying system shown, designated as a whole by 100, comprises a drying chamber 102, which can be sealed airtight against an environment 104 of the drying chamber 102.

[0090] One or more workpieces 106 to be dried can be placed in an interior space 108 of the drying chamber 102.

[0091] To carry out a hot air drying process, the drying system 100 includes an air circuit 110, which includes a discharge line 112 for removing air from the interior 108 of the drying chamber 102.

[0092] The discharge line 112 is connected to a suction-side inlet 114 of a blower 116.

[0093] From a pressure-side outlet 118 of the blower 116, an intermediate line 120 leads to an inlet 122 of an air conditioning device 124.

[0094] The air conditioning device 124 includes in particular a heating device for heating the air passed through the air conditioning device 124.

[0095] From an outlet 126 of the air conditioning device 124, a supply line 128 leads back into the interior 108 of the drying chamber 102.

[0096] The exhaust air extracted from drying chamber 102 is therefore part of the supply air supplied to drying chamber 102.

[0097] In the supply line 128 a branch 130 is arranged, to which an exhaust air line 132 is connected.

[0098] The flow through the exhaust air duct 132 can be regulated by means of an exhaust air valve, for example in the form of an exhaust air damper 134, in the exhaust air duct 132.

[0099] The discharge line 112 includes an inlet 136, at which a fresh air line 138 enters the discharge line 112.

[0100] The flow through the fresh air duct 138 can be regulated by means of a fresh air valve arranged in the fresh air duct 138, for example in the form of a fresh air flap 140.

[0101] To monitor the condition of the air in the interior 108 of the drying chamber 102, in the discharge line 112 and in the supply line 128, the drying system 100 includes several sensors 142.

[0102] The sensors 142 may in particular include a drying chamber humidity sensor 144 for measuring the humidity in the interior 108 of the drying chamber 102, a discharge line humidity sensor 146 for measuring the humidity in the discharge line 112 and / or a supply line humidity sensor 148 for measuring the humidity in the supply line 128.

[0103] The discharge line moisture sensor 146 is preferably arranged upstream of the inlet 136 of the fresh air line 138 into the discharge line 112.

[0104] The supply line moisture sensor 148 is preferably arranged upstream of the branch 130 of the exhaust air line 132 from the supply line 128.

[0105] All sensors 142 are connected to a control device 152 of the drying system 100 via suitable data and control lines 150.

[0106] The control device 152 includes an evaluation unit 154.

[0107] Evaluation unit 154 includes a process model for the drying process.

[0108] In order to be able to carry out a vacuum drying process as an alternative to or in rotation with hot air drying using the drying system 100, the drying system 100 also includes a vacuum source 156, which is connected to the interior 108 of the drying chamber 102 via an evacuation line 158.

[0109] The vacuum source 156 can, for example, include a vacuum reservoir and / or a vacuum pump 160.

[0110] If the vacuum source 156 includes a vacuum pump 160, then an outlet line 162 is connected to an outlet of the vacuum pump 160.

[0111] To monitor the condition of the air discharged through the outlet pipe 162, the drying system 100 can include a further sensor 142.

[0112] This sensor 142 can in particular include an outlet line moisture sensor 164.

[0113] The outlet line moisture sensor 164 is also connected to the control device 152 of the drying system 100 via a suitable data and control line 150.

[0114] The sensors 142 can be sensors for measuring relative humidity f, absolute humidity ρ w or specific humidity s.

[0115] The relative humidity f is the ratio between the instantaneous water vapor pressure and the saturation vapor pressure.

[0116] The absolute humidity ρw is the mass of water vapor per volume of air.

[0117] The specific humidity s is the ratio of the mass of gaseous water to the mass of dry air in which the gaseous water is absorbed.

[0118] Furthermore, it may be provided that one, several or all of the sensors 142 are capable of measuring the temperature of the respective air volume in addition to measuring humidity.

[0119] Using the drying system 100 described above, a method for drying workpieces in the drying chamber 102 is carried out, for example, as follows: The at least one workpiece 106 to be dried is placed in the drying chamber 102, and the drying chamber 102 is closed off from the environment 104.

[0120] Subsequently, at least one hot air drying process is carried out on the at least one workpiece 106 in the drying chamber 102.

[0121] In the hot air drying process, fresh air is supplied to the drying chamber 102 via the supply line 128, which has been heated by means of the air conditioning device 124.

[0122] At the same time, exhaust air is discharged from the drying chamber 102 through the exhaust pipe 112.

[0123] The supply air to the drying chamber 102 is supplied with fresh air from the fresh air line 138 via the inlet 136 before entering the drying chamber 102.

[0124] To monitor the hot air drying process, the respective relative humidity f is measured by means of the sensors 142, in particular by means of the drying chamber humidity sensor 144, by means of the discharge line humidity sensor 146 and by means of the supply line humidity sensor 148, preferably substantially continuously, and evaluated in the evaluation unit 154 of the control device 152 of the drying system 100.

[0125] In this embodiment of the method for drying workpieces 106, the relative humidity f thus represents a measured quantity that characterizes the drying process.

[0126] The sensor 142, whose measurement signal is in Fig. 2 The drying chamber humidity sensor 144, for example, is shown, which measures the relative humidity f in the interior 108 of the drying chamber 102.

[0127] In the illustrated embodiment, the relative humidity in the interior 108 of the drying chamber 102 at the beginning of the drying process (t = t 0 ) is f 0 .

[0128] From time t 0 to time t 1, a hot air drying process is carried out by circulating air through the air circuit 110 of the drying system 100, with fresh air being supplied through the fresh air flap 140 and exhaust air being discharged from the air circuit 110 through the exhaust air flap 134.

[0129] Moisture adhering to the at least one workpiece 106 to be dried evaporates or vaporizes and is carried away with the exhaust air from the interior 108 of the drying chamber 102, whereby the relative humidity f measured by the sensor 142 decreases from the initial value f 0 to the value f 1.

[0130] At time t 1, the supply of fresh air is stopped by closing the fresh air flap 140.

[0131] During a subsequent monitoring period of length Δt 1, during which the fresh air flap 140 remains closed, the relative humidity measured by the sensor 142 increases sharply because there is still a lot of moisture in the interior 108 of the drying chamber 102.

[0132] The removal of air through the exhaust flap 134 is also prevented during the monitoring period by closing the exhaust flap 134.

[0133] The evaluation unit 154 determines the rate at which the characteristic measured quantity, in this case the relative humidity, changes, from the slope of the course of the measured humidity as a function of time, i.e. from the ratio of Δf 1 and Δt 1 .

[0134] If this rate of change of the characteristic measured variable exceeds a predetermined limit (or one determined by an AI model implemented in the evaluation unit 154), the evaluation indicates that the hot air drying process is not yet complete, and the drying process is continued by opening the fresh air flap 140 and the exhaust air flap 134.

[0135] As from Fig. 2 As can be seen, the relative humidity measured by the sensor 142 then drops until a time t 2, at which the supply of fresh air is again interrupted by the control device 152 by closing the fresh air flap 140 and the exhaust air flap 134, for a period of time Δt 2 .

[0136] It may be provided that the time period Δt 2 depends on the rate of change of the characteristic measured quantity f determined in the preceding monitoring period.

[0137] In particular, it may be provided that the duration of each subsequent monitoring period increases if the rate of change of the characteristic measured variable decreases, in order to obtain sufficient resolution of the increase of the characteristic measured variable until the end of the next monitoring period.

[0138] Once again, in evaluation unit 154, the rate of change of the characteristic measured quantity is determined from the ratio of Δf 2 and Δt 2.

[0139] In the illustrated embodiment, this rate of change is lower in the second monitoring period, since there is only a small amount of residual moisture in the interior 108 of the drying chamber 102.

[0140] If the rate of change of the characteristic measured variable exceeds the specified limit (or the limit determined by the AI ​​model implemented in the evaluation unit 154), the hot air drying process is continued by the control device 152 by opening the fresh air flap 140 and the exhaust air flap 134.

[0141] At a time t 3, which is either fixed or determined by an AI model implemented in the evaluation unit 154, the fresh air supply is again interrupted by the control device 152 by closing the fresh air flap 140 and the exhaust air flap 134 for a further monitoring period of length Δt 3.

[0142] The evaluation unit 154 again determines the rate of change of the characteristic measured quantity, namely the relative humidity f.

[0143] In the Fig. 2 In the case shown, the measured relative humidity remains constant (at the value f 3) after the fresh air supply is interrupted, which means that the rate of change of the characteristic measured quantity is zero.

[0144] This means that the rate of change of the characteristic measured variable is below the specified limit value or the limit value determined by the AI ​​model implemented in evaluation unit 154.

[0145] Therefore, evaluation unit 154 assesses the drying process as complete.

[0146] The hot air drying process is therefore terminated, and the at least one workpiece 106 to be dried can be removed from the interior 108 of the drying chamber 102.

[0147] In this embodiment of a drying process, the assessment of whether the drying process is complete is an output variable determined by the evaluation unit.

[0148] Alternatively, it can also be provided that, after the evaluation of the rate of change of the characteristic measured quantity by the evaluation unit 154, a vacuum drying process is carried out by the control device 152 instead of a hot air drying process, during which the interior 108 of the drying chamber 102 is evacuated via the evacuation line 158 by means of the vacuum source 156.

[0149] Several drying cycles, in which a hot air drying process and a vacuum drying process are alternately carried out, can follow one another during the drying of the at least one workpiece 106 in the drying chamber 102, until the evaluation carried out by the evaluation unit 154 shows that the drying target has been achieved and the at least one workpiece 106 to be dried can be considered sufficiently dry.

[0150] Instead of the measurement signal from the drying chamber moisture sensor 144, the signal from the discharge line moisture sensor 146 or the supply line moisture sensor 148 can also be used by the evaluation unit 154 to determine the output variable that influences the further course of the drying process.

[0151] Furthermore, it may also be provided that the evaluation of the measurement signal of the at least one sensor 142 by means of the evaluation unit 154 includes the formation of a difference from the measurement signals of at least two sensors 142, for example the formation of a difference between the measurement signal of the discharge line moisture sensor 146 and the measurement signal of the supply line moisture sensor 148.

Claims

1. Method for drying workpieces (106), comprising the following: - introducing at least one workpiece (106) to be dried into a drying chamber (102); - carrying out at least one hot air drying procedure wherein feed air is fed to the drying chamber (102) and exhaust air is conducted out of the drying chamber (102); wherein fresh air is fed to the feed air before its entry into the drying chamber; characterized in that the feeding of fresh air to the feed air is reduced or interrupted during at least one monitoring period, at least one measurement variable characterizing the drying procedure is measured by means of at least one sensor (142) and a measurement signal of the at least one sensor (142) is transferred to an evaluating unit (154) of a control apparatus (152), and from the evaluation of the measurement signal of the at least one sensor (142) by means of the evaluating unit (154) there is established an output variable which influences the further progression of the method.

2. Method according to claim 1, characterized in that a duration of the at least one monitoring period is at least one second and / or not more than 4 minutes.

3. Method according to either of the claims 1 or 2, characterized in that a minimum and / or a maximum of the measurement signal is established and is used during the establishing of the output variable and / or in that a rate of change of the measurement variable is established and is used during the establishing of the output variable.

4. Method according to any one of the claims 1 to 3, characterized in that the at least one sensor (142) comprises a moisture sensor (144, 146, 148, 164), a temperature sensor, a thermal imaging camera for temperature monitoring the at least one workpiece (106) to be dried, a pressure sensor and / or a weight sensor for measuring a mass change of the at least one workpiece (106) to be dried and / or in that a sensor system is present for identifying a type of the at least one workpiece (106) to be dried and / or in that at least one sensor (142) measures a measurement variable in the drying chamber (102), in a feed conduit (128) for conducting feed air to the drying chamber (102), in a discharge conduit (112) for discharging exhaust air from the drying chamber (102), in an exhaust air conduit (132) for discharging exhaust air from an air circuit (110), in an evacuating conduit (158) for connecting the drying chamber (102) to a vacuum source (156), in an outlet conduit (162) of a vacuum pump (160) and / or in a surrounding area (104) of the drying chamber (102).

5. Method according to any one of the claims 1 to 4, characterized in that in the evaluating unit (154), a process model is implemented which comprises a control model and / or an AI model for assessing a drying procedure.

6. Method according to claim 5, characterized in that the process model is configured such that it is able to amend parameters of the drying method during the performance of a drying procedure or before the performance of a subsequent drying procedure in order to optimize the drying procedure, and / or in that the process model is configured such that it is able to establish at least one optimum output parameter for the drying procedure on the basis of at least one input parameter transferred to the evaluating unit (154), wherein the output parameter is usable for controlling the drying procedure by means of the control apparatus (152).

7. Method according to either of the claims 5 or 6, characterized in that the process model comprises an AI model which is configured such that it is able to optimize itself by changing at least one parameter of the drying procedure and by an assessment of the progression of the drying procedure.

8. Method according to any one of the claims 5 to 7, characterized in that the process model is configured such that data regarding the workpieces (106) to be dried are transferrable to the process model from outside a drying plant (100) used for carrying out the drying procedure, preferably from a prior process carried out before the drying procedure or from a central master computer system, and / or in that the process model is configured such that data regarding the workpieces (106) to be dried are transferrable to the process model by means of a sensor system, for example an imaging camera, by means of a barcode, by means of an RFID chip or by manual data input, and / or in that the process model is configured such that data regarding the quantity of liquid to be dried from the workpieces (106) to be dried are transmissible to the process model by means of a sensor system, which is preferably arranged in the storage container for a cleaning medium, and / or from an additional-dosing apparatus for a cleaning medium.

9. Method according to any one of the claims 5 to 8, characterized in that the process model assesses the progression of the drying method and / or at least one parameter of the drying method is regulable by the control apparatus (152) on the basis of at least one output of the process model.

10. Method according to any one of the claims 5 to 9, characterized in that the parameters of the drying method that are amendable by the control apparatus (152) on the basis of the assessment by way of the process model comprises a temperature of the drying medium, a heating output of an air conditioning apparatus (124), a change in the volume flow of a drying medium circulating in an air circuit (110), a change in a volume flow of fresh air that is mixed into a volume flow of the drying medium circulating in an air circuit (110), a control of at least one movement device for moving the at least one workpiece (106) to be dried in the drying chamber (102), a switching on or switching off of at least one apparatus applying energy to the at least one workpiece (106) to be dried in the drying chamber (102), for example, an infrared radiator or a microwave generator, a duration of a drying procedure and / or a change to a drying manner, for example a change from a hot air drying to a vacuum drying.

11. Method according to any one of the claims 1 to 10, characterized in that an assessment of the progression of the drying procedure comprises the calculation of a difference between moisture values and / or the calculation of a difference between temperature values and / or in that an assessment that the drying procedure is completed is generated by way of an automated monitoring process and / or by way of input by an operating person on the control apparatus (152), and / or in that the assessment that a workpiece (106) in the drying chamber (102) has been sufficiently dried is transferred to the evaluating unit (154) by a process step downstream of the drying procedure.

12. Method according to any one of the claims 1 to 11, characterized in that the evaluating unit (154) is located adjacent to the drying chamber (102) or remotely from the drying chamber, for example, in a cloud application.

13. Method according to any one of the claims 1 to 12, characterized in that at least one sensor (142) transfers its measurement signal to the evaluating unit (154) by means of a wireless connection, for example, a WLAN connection, a Bluetooth connection or a radio connection.

14. Method according to any one of the claims 1 to 13, characterized in that at the start of a hot air drying procedure, the fresh air feed is reduced or interrupted in order thereby to achieve a faster heating of the at least one workpiece (106) to be dried in the drying chamber (102), and / or in that during a hot air drying procedure, the specific air humidity (s), the absolute air humidity (ρw) and / or the relative air humidity (f) is maintained in a defined value range by regulating the fresh air feed and / or the heating output of the air conditioning apparatus (124) and / or in that after the introduction of the at least one workpiece (106) to be dried into the drying chamber (102), a vacuum drying procedure, then a hot air drying procedure and thereafter a further vacuum drying procedure is carried out.

15. Plant for drying workpieces (106), in particular, for carrying out the method for drying workpieces according to one of the claims 1 to 14, comprising the following: - a drying chamber (102); - an air circuit (110) which comprises a feed conduit (128) for feeding feed air into the drying chamber (102) and a discharge conduit (112) for discharging exhaust air from the drying chamber (102); - a regulable fresh air feed for feeding fresh air into the feed air before its entry into the drying chamber (102); - a control apparatus (152), which comprises an evaluating unit (154); and - at least one sensor (142) by means of which a measurement variable characterizing the drying procedure is measurable and the measurement signal thereof is transferrable to the evaluating unit (154); characterized in that the control apparatus (152) is configured such that the feeding of fresh air to the feed air is reduced or interrupted during at least one monitoring period and the evaluating unit (154) is configured such that, from the progression of the at least one measurement signal of the at least one sensor (142) during the at least one monitoring period, it establishes an output variable which influences the further progression of the drying method carried out by means of the drying plant (100).

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