Clamping system and method for operating the clamping system

Abstract

The invention relates to a method for operating a clamping system comprising a tray for holding a workpiece or a tool having a tray contact surface and a locking mechanism and a chuck having a chuck contact surface and a locking mechanism. The chuck includes a detection air passage for supplying pressurized air into the chuck through a detection air inlet formed on an outer surface of the chuck, and a detection hole opened on a chuck contact surface and communicatively connected with the detection air passage. The clamping system also includes a valve and a pressure sensor. The method includes the steps of: opening the valve and supplying pressurized air having a defined pressure into the detection air passage of the chuck through the detection air inlet; performing a clamping procedure by approaching the tray contact surface to the chuck contact surface until the tray locking mechanism interacts with the chuck locking mechanism to clamp the tray with the chuck, wherein a gap is formed between the tray contact surface and the chuck contact surface in a clamped state; a clamping state detection program is performed after the clamping program.

Description

Technical Field

[0001] The present invention relates to a clamping system and a method for operating the clamping system. In particular, the present invention relates to a detection device for detecting the clamping state of a pallet and a chuck. Background Art

[0002] In the processing of workpieces, a clamping device with high precision is required for clamping the workpiece or processing tool. Such clamping systems are widely used in the field of processing such as milling, turning, electrical discharge machining or laser processing. Such processing is performed by machine tools. In order to firmly and accurately hold the workpiece or processing tool in the machine tool, a clamping system with high precision is crucial to ensure processing safety and processing accuracy.

[0003] US Pat. No. 9,108,286 discloses a clamping device for a tool or a workpiece, which clamping device comprises a chuck and a holder for holding the workpiece or the tool.

[0004] Since the machining accuracy directly depends on the reproducibility of the clamping process of different tools, it is crucial to ensure the clamping accuracy. In addition to improving the reference in X, Y, and Z of the clamping system, a sensor unit is introduced in the clamping system to further improve the clamping accuracy.

[0005] US 8 308169 discloses a chuck-type fixture for a tool or workpiece, which includes a chuck and a tool holder or workpiece holder matching the chuck. The chuck has a column with a support surface for orienting the tool or workpiece in the X direction and the Y direction and an end face for establishing a plane perpendicular to the Z direction. A device for measuring the distance between the chuck and the tool holder or workpiece holder is formed in the support surface and in the end face. Summary of the invention

[0006] The object is to provide a method for operating a clamping system such that the clamping accuracy can be monitored. In particular, it is an object of the invention to provide a clamping system with improved clamping state monitoring.

[0007] According to the invention, these objects are achieved by the features of the independent claims.In addition, further advantageous embodiments can be derived from the dependent claims and the description.

[0008] The present invention relates to a method for operating a clamping system, the clamping system comprising: a pallet for holding a workpiece or a tool, the pallet having a pallet contact surface and a pallet locking mechanism; and a chuck having a chuck contact surface and a chuck locking mechanism. The chuck comprises a detection air channel and a detection hole, the detection air channel being used to supply pressurized air into the chuck through a detection air inlet formed on the outer surface of the chuck, the detection hole opening on the chuck contact surface and being communicatively connected to the detection air channel. The clamping system also comprises a valve arranged in a feed line of the detection air inlet and a pressure sensor arranged between the valve and the detection air inlet.

[0009] The method comprises the following steps: opening a valve and supplying pressurized air with a defined pressure into a detection air channel of a chuck through a detection air inlet; performing a clamping procedure by bringing a pallet contact surface close to a chuck contact surface until a pallet locking mechanism interacts with a chuck locking mechanism to clamp the pallet with the chuck; and performing a clamping state detection procedure after the clamping procedure.

[0010] The clamping state detection procedure includes the following steps: closing the valve to stop supplying pressurized air into the detection air channel; measuring the pressure at the detection air inlet by a pressure sensor at at least two different times within a defined time interval when the valve is closed and the pallet and the chuck are in a clamping state; determining a pressure change by calculating a pressure difference of the measured pressures by a calculation module; and determining whether there is a gap between the pallet contact surface and the chuck contact surface based on the determined pressure change.

[0011] Chucks and pallets are usually manufactured very accurately. Ideally, in the clamped state, the pallet contact surface lies perfectly on the chuck contact surface and therefore there is no gap. However, due to damage to the contact surface of the chuck and other reasons, the contact surface of the pallet is not always in seamless contact with the contact surface of the chuck. For example, machining generates dirt and particles, which may remain on the contact surface of the chuck. Therefore, there may be a gap between the two contact surfaces. If there is no gap, there is no air leakage through the detection hole because the detection hole is sealed by the pallet contact surface. If there is a gap, a leakage path through the detection hole and the gap is formed. Detecting the presence of a gap helps to identify the poor clamping quality of the pallet and chuck in a timely manner. However, it is a challenging task to accurately measure the gap size in a reliable manner in a machine environment because, if there is a gap, the gap size is in the micrometer range. In addition, the measurement must be performed in the clamped state and in the machine tool in most applications, so there is only limited space for arranging the measuring device close to the area to be measured.

[0012] Another challenge is to provide a method that can be widely used in different types of clamping systems. There are many existing clamping devices of various types. Adding sensors in the clamping device to provide intelligent monitoring functions requires space and design changes of the clamping device. However, for any machine tool, air is almost always available. In addition, air channels are usually provided in the chuck for the chuck clamping mechanism and for other functions such as cleaning the contact surface. If these existing air channels can be used for detection, the method can be flexibly applied to different types of clamping devices without significant changes to the clamping device itself. The method of the present invention provides the possibility of accurately obtaining gap sizes (for example, in the range of 3μm-5μm or even smaller) using existing clamping devices.

[0013] Another advantage of the method of the invention is that the pressurized air does not have to be supplied continuously during the entire measuring period. It is an energy-saving method. The pressure measurement is carried out under the condition that no pressurized air is supplied into the detection air channel during the measuring phase. Before the measurement, pressurized air is only supplied into the detection channel for a short period of time.

[0014] Furthermore, the pressure sensor is arranged on one side of the inlet, ie at the same side where the pressurized air is supplied, and not at the outlet of the air channel.The valve and the pressure sensor are arranged at the outside of the chuck, so the method is not limited by the space inside the chuck.

[0015] In one variant, before the pallet is clamped with the chuck, the valve is opened for supplying pressurized air into the detection channel. This variant has the advantage that the contact surface can be cleaned by the air flowing out of the detection hole.

[0016] In another variant, after the pallet is clamped with the chuck, the valve is opened for supplying pressurized air into the detection channel. In this variant, the pallet is first clamped with the chuck, then the valve is opened, and air is supplied into the chuck. After a short period of time, the valve is closed to stop the supply of pressurized air, and a pressure measurement is performed.

[0017] The clamping state detection procedure is performed after the clamping procedure. This can be performed immediately after the clamping procedure or delayed for a defined time period. The procedure must be performed by maintaining the valve in a closed state and maintaining the tray and the chuck in a clamped state. When the valve is closed, the supplied pressurized air is blocked by the valve, and no air is further supplied to the detection air channel. Since the gap size is very small, i.e. in the micrometer range, a substantially closed volume is formed in the detection air channel. Since air is supplied to the detection air channel before the valve is closed, the volume is pressurized. However, due to air leakage through the detection hole and the gap, the pressure in the closed volume will decrease over time. By detecting the pressure change of the closed volume within a defined time period, the gap size can be estimated. To achieve this purpose, the pressure at the detection air inlet is measured. It is possible to arrange the pressure sensor in the detection air channel. However, arranging the pressure sensor at the outside of the chuck can make the design of the chuck easy without compromising the measurement accuracy. The first air pressure P1 is recorded at a defined time after the closed volume is generated to achieve the stability of the pressure reading. Then, after a defined time interval, a second air pressure P2 is measured. The calculation module is configured to receive the two measured pressures P1 and P2 and calculate the delta between P1 and P2 to determine the gap size. Of course, the number of pressure measurements is unlimited. The pressure can be measured during the entire clamping phase to observe pressure changes over a long period of time.

[0018] In one embodiment, the method comprises the following steps, in the order of steps a) to c): a. Open the valve and supply pressurized air having a defined pressure to the detection air channel of the chuck through the detection air inlet; b. Perform the clamping procedure; and c. Perform the clamping status detection procedure.

[0019] Preferably, the gap size is determined by comparing the determined pressure change with calibration data comprising a plurality of pressure changes and corresponding gap sizes.

[0020] The calibration data can be obtained by performing calibration test measurements using a calibration tool on a clamping device with a defined gap. Preferably, the calibration data is stored in a storage module, for example in the form of a lookup table. For example, a calibration kit can be manufactured including a tray and a chuck used to obtain the calibration data. The contact surfaces of the tray and / or chuck are specially manufactured to feature precisely defined gap dimensions. The pressure change of the calibration kit is measured, and the defined gap dimensions and the measured pressure change are stored.

[0021] In particular, the method comprises comparing the gap size with a gap threshold value to determine whether the gap is within an allowable range. If the gap size is within the allowable range, the clamping quality is ensured and therefore no action has to be taken. However, if the gap size is outside the allowable range, then action should be taken to avoid any damage. For example, if several pallets are clamped with the same chuck and all gap sizes are outside the allowable range, then a bad state of the chuck may be concluded and therefore the chuck should be replaced.

[0022] In an advantageous variant, an action is determined based on the determined gap size. In particular, the action is one or more of: generating an error signal, releasing the pallet and the chuck, changing the pallet or the chuck, and displaying the gap size.

[0023] In some embodiments, identification information of the tray and chuck is associated with the determined gap size.

[0024] Advantageously, each pallet is provided with an identification unit for identifying the pallet and generating pallet identification information. In particular, the identification unit is an RFID chip.

[0025] When different pallets are clamped with different chucks, the gap size varies. Even when the same pallet is clamped with the same chuck, the gap size may vary in different clamping procedures. For example, dirt adhering to the contact surface may vary in size and / or amount. Such changes may lead to changes in the gap size. When a pallet is clamped with a chuck, identification information of the pallet and the chuck is collected and stored in a storage unit. Furthermore, by storing the identification information and the determined gap size, the determined gap size can be associated with the corresponding pallet and chuck. This information can then be retrieved for different purposes. For example, if a machine component has poor quality, this information can help to identify problems that occur during production.

[0026] In one variant, the determined pressure change and / or gap size is analyzed to identify the clamping state of the pallet and the chuck currently in operation. For example, the determined gap size is compared with a threshold value to determine how well the pallet is clamped with the chuck.

[0027] In another variant, the pressure changes and / or gap dimensions determined over a period of time are analyzed. This aims to observe how the gap dimensions change over the course of time. For example, different pallets are clamped with the same chuck over a period of time. Each time a pallet is clamped with the chuck, the gap dimensions are determined. By collecting the gap dimensions over this period of time, a history of the clamping states of different pallets clamped with the same chuck can be generated. A damaged chuck or wear of the chuck can be detected based on this history. If the gap dimensions become worse, a maintenance requirement for the chuck can be identified.

[0028] In order to improve the clamping quality, a cleaning procedure may be performed. Typically, the chuck is mounted on a machine tool table or spindle, and during machining, the chuck contact surface is contaminated with debris. Therefore, a cleaning procedure before clamping a new pallet thereon may remove dirt on the contact surface to ensure clamping quality. Before the clamping procedure, the chuck contact surface is cleaned by performing a cleaning procedure. Pressurized air is supplied to a clean air channel connected to a clean hole opened on the contact surface. The clean air channel is formed inside the chuck and is connected to the clean hole. Pressurized air may flow through the clean channel and the clean hole to reach the contact surface.

[0029] Preferably, the detection air channel acts as a clean air channel, and the detection hole acts as a clean hole. This provides the advantage that the existing clean channel can be used for gap detection.

[0030] In one variant, the chuck locking mechanism is pneumatically activated, so that the air channel used for clamping can also be used as a test air channel.

[0031] In one variant, the clamping state detection procedure is controlled by a control module. The control module is configured to control the valve and the pressure sensor so that the pressure measurement can be performed after the valve is closed.

[0032] To activate the clamping state detection routine, the control unit receives the gap detection signal.

[0033] In one variant, the gap detection signal is input by activating an activation button connected to the control unit. Alternatively, the gap detection signal is received from a central control unit. In particular, the central control unit is configured to control a clamping procedure of the pallet and the chuck.

[0034] Furthermore, a storage module is provided to store various data, such as measured pressure, calibration data, determined gap dimensions, identification information of the tray and chuck.

[0035] According to the present invention, a clamping system for a workpiece or tool used in a machine tool includes a pallet for holding the workpiece or tool, a chuck, a valve, a pressure sensor, a control module and a computing module. The pallet has a pallet contact surface and a pallet locking mechanism. The chuck has a chuck contact surface and a chuck locking mechanism, wherein the chuck includes a detection air channel and a detection hole, the detection air channel is used to supply pressurized air to the chuck through a detection air inlet formed on the outer surface of the chuck, and the detection hole is open on the chuck contact surface and is connected to the air channel. The valve is arranged in the feed line of the detection air inlet. When the valve is opened, it allows pressurized air to flow into the detection air channel of the chuck through the detection air inlet. When the valve is closed, it blocks the pressurized air from flowing into the detection air channel. The pressure sensor is arranged between the valve and the air inlet, and is configured to measure the pressure at the detection air inlet. The control module is configured to control the valve and the pressure sensor, thereby performing the following steps: i. closing the valve to stop the supply of pressurized air to the detection air channel, especially after the pallet is clamped with the chuck; and ii. When the valve is closed and the tray and the chuck are in a clamped state, the pressure at the detection air inlet is measured by the pressure sensor at at least two different times within a defined time interval; The calculation module is configured to determine a pressure change by calculating a difference in the measured pressures, and determine whether a gap exists between the tray contact surface and the chuck contact surface based on the determined pressure change.

[0036] In a preferred variant, the control module is configured to control the valve and the pressure sensor so as to perform the following steps: i. Open the valve to supply pressurized air to the detection air channel of the chuck; ii. closing the valve to stop the supply of pressurized air to the test air channel, especially after clamping the pallet with the chuck; and iii. When the valve is closed and the tray and the chuck are in a clamped state, the pressure at the detection air inlet is measured by the pressure sensor at at least two different times within a defined time interval; In a variation, the control module is configured to control the valve, pressure sensor, tray, and chuck to perform the following steps: i. Open the valve to supply pressurized air to the detection air channel of the chuck; ii. Clamp the pallet with a chuck; iii. closing the valve to stop the supply of pressurized air to the test air channel, especially after clamping the pallet with the chuck; and iv. when the valve is closed and the tray and the chuck are in a clamped state, the pressure at the detection air inlet is measured by the pressure sensor at at least two different times within a defined time interval; The valve and the pressure sensor are arranged at the outside of the chuck. Such an arrangement provides a simple design of the clamping system. Another advantage of the clamping system is that the pressurized air does not have to be supplied continuously during the entire measuring period. It is an energy-saving system. The pressure measurement is carried out under the condition that no pressurized air is supplied into the detection air channel during the measuring phase.

[0037] In one embodiment, valve, pressure sensor, control module and computing unit are included in a housing to form a detection device. In addition, air input and air output are arranged on the housing. Air input is connected to the valve for supplying air into the valve. Air output is connected to the pressure sensor and can be further connected to the detection air inlet of the chuck. Air source can be connected to the air input so that when the valve is opened, pressurized air can flow to the detection air inlet through the air input, valve, pressure sensor and air output. The detection device can be applied flexibly. It can be arranged at any position outside the chuck. If the detection hole formed in the chuck for detecting air passage and connected to the detection air passage has an opening on the chuck contact surface, the detection device can be combined with various types of trays and chucks. Depending on the size of the contact surface, the detection hole can have different sizes. In particular, the diameter of the detection hole is in the millimeter range, such as 0.5mm-3mm.

[0038] The detection device may be arranged near the chuck, for example on a machine tool table. Each machine tool table is equipped with a detection device. When the chuck is mounted on the machine tool table, the detection device may be connected to the chuck by connecting the air output of the detection device to the detection air inlet of the chuck. Usually, an air source is available in the machine tool, so by connecting the air source to the air input of the detection device, air can be easily supplied to the detection device and then further to the chuck.

[0039] In a variant, an activation mechanism such as a button is provided on the housing to activate the clamping state detection procedure including closing the valve and starting the pressure measurement. In this way, a stand-alone system can be realized. When the pallet is clamped with the chuck, the operator can press the button and the clamping state procedure starts automatically. No higher level control is required.

[0040] In some embodiments, detection and clamping are controlled by a higher level control unit. The system includes a central control unit, which can be arranged remotely from the tray and the chuck. The central control unit is configured to control the clamping procedure. In addition, the central control unit is configured to send a gap detection signal to the control module for activating the clamping state detection process.

[0041] For example, the central control unit first controls the automatic pallet changer to clamp the pallet with the chuck. Thereafter, the central control unit sends a gap detection signal to the control module to activate the detection process. Upon receiving the signal, the control module controls the valve from an open state to a closed state, and controls the pressure sensor to record the pressure.

[0042] It is also possible for the control module and the computing module to be arranged in a central control unit.

[0043] In a preferred variant, each pallet of the clamping system is provided with an identification unit for identifying the pallet and generating pallet identification information, in particular, the identification unit is an RFID chip.

[0044] In the present invention, a detection device for detecting a clamping state of a pallet and a chuck for holding a workpiece or a tool is disclosed. The pallet has a pallet contact surface and a pallet locking mechanism, and the chuck has a chuck contact surface and a chuck locking mechanism. The chuck includes a detection air channel and a detection hole, the detection air channel is used to supply pressurized air into the chuck through a detection air inlet formed on the outer surface of the chuck, and the detection hole is open on the chuck contact surface and is connected to the detection air channel. The device includes a valve, a pressure sensor, a control module and a computing unit. The valve is arranged in a feed line of the detection air inlet. When the valve is opened, it allows pressurized air to flow into the detection air channel of the chuck through the detection air inlet. When the valve is closed, it blocks the pressurized air from flowing into the detection air channel. The pressure sensor is arranged between the valve and the detection air inlet, and is configured to measure the pressure at the detection air inlet. The control module is configured to control the valve and the pressure sensor, thereby performing the following steps: v. Close the valve to stop the supply of pressurized air to the detection air channel; vi. When the valve is closed and the tray and the chuck are in a clamped state, the pressure at the test air inlet is measured by the pressure sensor at at least two different times within a defined time interval; The calculation module is configured to determine a pressure change by calculating a difference in the measured pressures, and determine a gap size defined by a distance between the tray contact surface and the chuck contact surface based on the determined pressure change.

[0045] All variants of the invention may be combined.In order to avoid repetition of features, features of a method may be referred to as an apparatus, and vice versa. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] In the following, a more specific description of the present invention is further described. Embodiments are described and explained in detail with reference to the accompanying drawings, in which:

[0047] Figure 1 A schematic diagram illustrating a first variation of the clamping system;

[0048] Figure 2 Graphics Figure 1 A timing diagram of the clamping system shown in ;

[0049] Figure 3 Graphics Figure 1 A diagram of the pressure variation of the clamping system shown in;

[0050] Figure 4 A schematic diagram illustrating a second variation of the clamping system;

[0051] Figure 5 , Figure 6 , Figure 7 , Figure 8 showing a first type of tray and chuck; and

[0052] Fig. 9 A second type of tray and chuck is shown. DETAILED DESCRIPTION

[0053] Figure 1 A schematic diagram of a first variant of the clamping system 1 is shown. In order to improve the monitoring of the clamping state of the pallet 20 and the chuck 10, a detection device 30 is provided. It includes a valve 32 for opening and closing the pressurized air passage, a pressure sensor 31 and a processing unit 33. For example, the processing unit is a programmable logic controller. The detection device has two inputs and an output. The first input is an air input for connecting an air source 5 to one end of a valve for supplying pressurized air therein. The second input is a signal input for receiving a gap detection signal that triggers a clamping state detection program. The output is an air output, which is connected to the chuck, in particular to a detection air inlet formed on the outer surface of the chuck. The pressure sensor is positioned after the valve because it is used to measure the pressure change of the closed volume formed by the detection air channel in the chuck.

[0054] The processing unit 33 includes a computing module 34, a control module 37, a communication module 36 and a storage module 35. The control module is configured to control the valve and the pressure sensor. The storage module is configured to store data such as measurement data or processed data. The communication module is configured to communicate with the pressure sensor to collect the measurement data. In addition, the communication module is configured to communicate with an external device to transmit data received from the pressure sensor or data processed by the computing module or stored in the storage module. It is also possible to integrate additional communication modules to allow the detection device to communicate with other devices such as machine tools and automation systems. Additional communication modules include wired communication interfaces or wireless communication interfaces.

[0055] The processing unit, the valve and the pressure sensor are embedded in a housing with two input connections and one output connection. To operate the clamping system, an air source 5 is connected to the air input of the detection device to supply pressurized air. The air output is connected to the chuck. The gap detection signal is connected to an activation mechanism such as a button. The activation mechanism is preferably mounted on the outside of the housing of the detection device. However, it is possible to mount the activation mechanism separately from the housing of the detection device and connect the activation mechanism to the gap detection signal input via a cable. It is also possible to send the signal directly to the processing unit wirelessly via the communication module.

[0056] For example, the chuck is mounted on a machine tool table. The operator can clamp the pallet with the chuck and activate the activation mechanism to start the clamping state detection. When the operator presses the button, the valve is closed and the pressure at the detection inlet of the chuck is measured. For example, the first measurement is performed 2 seconds after the valve is closed. The second pressure is performed three seconds after the first measurement.

[0057] Figure 2 A timing diagram of a method for operating a clamping system is shown. Three phases are shown: an initial phase, a clamping phase, and a detection phase. In the initial phase from t0 to t1, the chuck is opened and the valve is also opened. This phase is intended to supply pressurized air into the chuck. In the clamping phase from t1 to t2, a clamping procedure is performed. During this phase, the pallet is clamped with the chuck by interacting the pallet locking mechanism and the chuck locking mechanism while the valve remains open. In the detection phase from t2 to t5, a clamping detection procedure is implemented. During the entire measurement period, the chuck is closed and the valve is closed to stop the supply of pressurized air. The gap measurement can be started at t2, but it is preferred to wait a defined time interval until the pressure inside the detection air channel stabilizes. At time t3, the gap measurement begins. The first pressure sensor measures a first pressure P1 at time t3 and measures a second pressure P2 at time t5. Figure 2 The timing diagram of is one of the possible variants. Other possible variants are not shown in the figure. For example, after the pallet and the chuck are clamped, the valve is opened for a defined period of time for supplying pressurized air into the closed volume and is closed again before the pressure measurement is performed.

[0058] Figure 3The corresponding pressure changes during different stages are shown. In the initial stage, pressurized air with pressure P0 is supplied to the detection air channel of the chuck, so the pressure in the air channel is P0. P0 may be lower than the pressure at the air source because the chuck is open. When the pallet is clamped with the chuck, the detection air channel is closed, and the pressure in the detection air channel increases to P3, but due to the pressure drop along the feed pipe, the pressure may still be lower than the pressure at the air source. Between time t2 and t5, the valve is closed and a substantially closed volume is created in the detection air channel. However, due to air leakage through the detection hole and the gap between the pallet contact surface and the chuck contact surface, the pressure slowly decreases. The pressure decreases from P1 to P2. The calculation module receives the two measured pressures and determines the pressure change and calculates the gap size based on the calculated pressure change.

[0059] Figure 4 Another variant of the clamping system is shown. The system additionally comprises a central control unit 8, which is configured to centrally control the entire system. The central control unit is arranged to communicate with the processing unit, in particular with the control module. The central control unit is configured to control the clamping program of the pallet and the chuck. The central control unit may be a server arranged in the production workshop. By using the central control unit, additional automation devices may be combined with the clamping system. For example, the chuck is mounted on a machine table of a machine tool. The central control unit controls an automation device, which is used to pick up a pallet from a pallet storage, transport the pallet to a position close to the machine table, and clamp the pallet with the chuck. In addition, the central control unit controls the control module to start a gap detection program by sending a gap detection signal to the control module. In addition, the central control unit may control the air source to change the pressure supplied to the chuck. A cleaning program may also be activated by the central control unit. The processing unit is configured to transmit the measured pressure to the central control unit for determining the gap size or to transmit the determined gap size to the central control unit. In addition, the processing unit may also transmit identification information of the pallet and the chuck to the central control unit.

[0060] Figure 5 , Figure 6 , Figure 7 and Figure 8 A first type of chuck and tray is shown. Figure 5 A three-dimensional view of the first chuck 110 is shown. Figure 6A three-dimensional view of the first chuck 110 and the first tray 150 in a clamped state is shown. The first chuck includes a plurality of first chuck reference elements 112 formed on the top surface of the chuck. Usually, reference elements for all three directions X, Y and Z are required to ensure accurate positioning. Of course, the first tray is also provided with reference elements in all three directions. The first chuck contact surface 116 is formed on the protrusion. In particular, in this example, four contact surfaces are provided on the top surface of the chuck. In addition, the detection hole 114 is open on the contact surface. In particular, four detection holes are formed in the chuck. However, the number of contact surfaces and detection holes is not limited to four, and may be less than or more than four.

[0061] The chuck has several air channels for different functions. Figure 6 A cross-sectional view of Figure 7 As shown in, in addition to the first detection air channel 121, the first chuck opening air channel 123 and the first chuck turbine air channel 124 are formed inside the chuck. They are not connected to each other. When pressurized air is supplied to the first chuck opening air channel, the chuck locking mechanism is deactivated and the chuck is opened for receiving the tray. By deactivating the pressurized air in the first chuck opening air channel, the chuck is closed due to the spring-loaded locking mechanism. If the tray is already positioned on the chuck, the chuck is clamped with the chuck. In some applications, an increased clamping force is required. For such applications, a so-called turbine function can be activated. When pressurized air is supplied to the first chuck turbine air channel, the clamping force generated by the locking mechanism can be increased. Only the first detection air channel is connected to the first detection hole because the channel is applied to gap measurement. If more than one detection hole is formed in the chuck, all the detection holes are connected to the first detection air channel, so that only one air inlet is required to supply pressurized air. For each air channel, an air inlet is provided on the outer surface of the chuck for connecting a pipe for supplying air. The first chuck opening air inlet 117 is connected to the first chuck opening air channel. The first chuck turbine air inlet 118 is connected to the first chuck turbine air channel. The first detection air inlet 111 is connected to the first detection air channel. In this example, all air inlets are arranged on the side wall of the chuck. However, the position of the inlet is not limited and can also be on the bottom surface of the chuck.

[0062] In order to clamp the pallet to the chuck, the first chuck locking mechanism interacts with the first pallet locking mechanism. In addition, in the clamped state, there may be a gap due to, for example, debris adhering to the contact surface of the chuck. If there is a gap, the first pallet contact surface 155 is not completely located on the contact surface of the chuck. Figure 8 Show Figure 7 Magnified view of section A. Since the gap size is in the micrometer range, it is difficult to depict.

[0063] Fig. 9 A cross-sectional view of a second type of tray and chuck is shown in a clamped state. The first chuck is an example demonstrating separate air channels for various functions. Fig. 9 The second chuck illustrated in FIG shows an example of sharing one air channel for different functions. The detection air channel is also used to increase the clamping force of the chuck locking mechanism and the cleaning of the contact surface. This is possible because the cleaning procedure, the turbine function and the gap detection procedure occur in a sequential manner.

[0064] The second chuck has a second chuck contact surface 216 and a second detection hole 214 on the second chuck contact surface. The second chuck is also characterized by a reference element and a locking mechanism. When the chuck is used to clamp the pallet, a second gap 215 may exist between the second pallet contact surface and the second chuck contact surface.

[0065] The second chuck open air channel 223 is formed inside the chuck and is connected to the second chuck open air inlet 217 arranged on the outer surface of the chuck. There is only one air channel and one air inlet for gap detection and turbine function. The second detection air channel 221 is connected to the second turbine air channel inside the chuck. The second detection air inlet 211 is formed on the outer surface of the second chuck. For different purposes, the air pressure of the supplied air can be varied. The second detection air channel is connected to the second detection hole 214 opened on the contact surface of the chuck.

[0066] Reference numerals list 1Clamping system 3. Second pressure sensor 4Central Control Unit 5. Air Source 6. Traffic Limitation 7. Second pressure sensor 8Central Control Unit 10 Chuck 20 pallets 30 Detection device 31 First pressure sensor 32 valves 33 processing units 34 Computing Modules 35 storage modules 36 Communication Module 37 Control Module 110 First Chuck 111 First detection air inlet 112 The first chuck benchmark 114 First detection hole 115 First Gap 116 first chuck contact surface 117 First chuck opens air inlet 118 First chuck turbine air inlet 121 First detection air channel 123 First chuck opens air channel 124 Second chuck turbine air passage 150 First Pallet 155 First tray contact surface 210 Second chuck 211 Second detection air inlet 214 Second detection hole 215 Second Gap 216 second chuck contact surface 217 Second chuck opens air inlet 221 Second detection air channel 223 Second chuck opens air channel 250 Second Pallet 255 Second tray contact surface.

Claims

1. A method for operating a clamping system (1), the clamping system (1) comprising: A pallet (20, 120, 220) for holding a workpiece or a tool, the pallet (20, 120, 220) having a pallet contact surface (155, 255) and a pallet locking mechanism; and a chuck having a chuck contact surface (115, 215) and a chuck locking mechanism, wherein the chuck comprises a detection air channel and a detection hole, the detection air channel being used to receive pressurized air supplied through a detection air inlet formed on an outer surface of the chuck, the detection hole opening on the chuck contact surface and being communicatively connected to the detection air channel, wherein the clamping system further comprises a valve arranged in a feed line of the detection air inlet and a pressure sensor arranged between the valve and the detection air inlet, the method comprising the following steps: a. In particular, when the tray and the chuck are in a loose state, the valve is opened and the pressurized air having a defined pressure is supplied to the detection air channel of the chuck through the detection air inlet; b. clamping the pallet by bringing the pallet contact surface close to the chuck contact surface until the pallet locking mechanism interacts with the chuck locking mechanism to clamp the pallet with the chuck; c. After the clamping procedure, a clamping state detection procedure is performed, and the clamping state detection procedure includes: i. closing the valve to stop the supply of pressurized air to the detection air channel; ii. when the valve is closed and the tray and the chuck are in the clamped state, the pressure at the detection air inlet is measured by the pressure sensor at at least two different times within a defined time interval; iii. determining the pressure change by calculating the pressure difference of the pressure measured by the calculation module; and iv. determining whether there is a gap between the tray contact surface and the chuck contact surface based on the determined pressure change.

2. The method according to claim 1, wherein: A gap size defined as the distance between the pallet contact surface and the chuck contact surface is determined, in particular, by comparing the determined pressure drop with calibration data comprising a plurality of pressure variations and corresponding gap sizes.

3. The method according to claim 2, wherein: The method includes comparing the gap size to a gap threshold to determine whether the gap is within an acceptable range.

4. The method according to claim 2 or 3, wherein: An action is determined based on the determined gap size, in particular, the action is one or more of: generating an error signal, releasing the tray and the chuck, and displaying the gap size.

5. The method according to any one of claims 2 to 4, wherein: Identification information of the tray and the chuck is associated with the determined gap size.

6. The method according to claim 5, wherein: Each pallet is provided with an identification unit for identifying the pallet and generating identification information of the pallet. In particular, the identification unit is an RFID chip.

7. The method according to any one of claims 1 to 6, wherein: Prior to the clamping procedure, the chuck contact surface is cleaned by performing a cleaning procedure, wherein the pressurized air is supplied to a clean air channel connected to a cleaning hole opened on the contact surface, in particular, the detection air channel serves as the clean air channel and the detection hole serves as the cleaning hole.

8. The method according to any one of claims 1 to 7, wherein: The clamping system includes a control module and a storage module, the control module is configured to control the valve and the pressure sensor for performing the clamping state detection program, and the storage module is configured to store the data. In particular, the control module, the storage module and the calculation module are included in a processing unit.

9. The method according to any one of claims 1 to 8, wherein: The control module is configured to receive a gap detection signal for activating the clamping state detection program, in particular, the gap detection signal is input by activating an activation mechanism connected to the control module or received from a central control unit configured to control the clamping program of the pallet and the chuck.

10. A clamping system for holding a workpiece or tool for use in a machine tool, comprising: a. a pallet for holding the workpiece or the tool, having a pallet contact surface and a pallet locking mechanism; b. a chuck having a chuck contact surface and a chuck locking mechanism, wherein the chuck includes a detection air channel and a detection hole, the detection air channel being used to supply pressurized air into the chuck through a detection air inlet formed on an outer surface of the chuck, and the detection hole opening on the chuck contact surface and being communicatively connected to the detection air channel; c. a valve arranged in the feed line of the detection air inlet, wherein when the valve is open, it allows the pressurized air to flow into the detection air channel of the chuck through the detection air inlet, wherein when the valve is closed, it blocks the pressurized air from flowing into the detection air channel; d. a pressure sensor disposed between the valve and the detection air inlet and configured to measure the pressure at the detection air inlet; e. A control module, the control module being configured to control the valve and the pressure sensor to perform the following steps: i. closing the valve to stop the supply of pressurized air to the detection air channel; ii. when the valve is closed and the tray and the chuck are in the clamped state, the pressure at the detection air inlet is measured by the pressure sensor at at least two different times within a defined time interval; f. A calculation module configured to determine a pressure change by calculating a difference in the measured pressures, and determine whether a gap exists between the tray contact surface and the chuck contact surface based on the determined pressure change.

11. The system according to claim 10, wherein: Each pallet is provided with an identification unit for identifying the pallet and generating identification information of the pallet. In particular, the identification unit is an RFID chip.

12. The system according to claim 11, wherein: The measured pressure and / or calibration data are associated with the identification unit.

13. The system according to any one of claims 10 to 13, wherein: The valve, the pressure sensor, the control module and the calculation module are embedded in one housing, in particular, an activation mechanism is arranged on the outside of the housing and connected to the control module, preferably, the activation mechanism is a button.

14. A system according to any one of claims 10 to 13, wherein: The system includes a central control unit configured to control the clamping procedure and send a gap detection signal to the control module to activate the clamping state detection procedure.

15. A detection device for detecting the clamping state of a pallet and a chuck for holding a workpiece or a tool, wherein: The tray has a tray contact surface and a tray locking mechanism, and the chuck has a chuck contact surface and a chuck locking mechanism, wherein the chuck includes a detection air channel and a detection hole, the detection air channel is used to supply pressurized air into the chuck through a detection air inlet formed on the outer surface of the chuck, and the detection hole is open on the chuck contact surface and is communicatively connected to the detection air channel, and the detection device includes: a. a valve arranged in the feed line of the detection air inlet, wherein when the valve is open, it allows the pressurized air to flow into the detection air channel of the chuck through the detection air inlet, wherein when the valve is closed, it blocks the pressurized air from flowing into the detection air channel; b. a pressure sensor disposed between the valve and the detection air inlet and configured to measure the pressure at the detection air inlet; c. A control unit configured to control the valve and the pressure sensor to perform the following steps: i. closing the valve to stop the supply of pressurized air to the detection air channel; ii. when the valve is closed and the tray and the chuck are in the clamped state, the pressure at the detection air inlet is measured by the pressure sensor at at least two different times within a defined time interval; d. A calculation module configured to determine a pressure change by calculating a difference in the measured pressures, and determine whether a gap exists between the tray contact surface and the chuck contact surface based on the determined pressure change.

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