Forming apparatus and method of operating forming apparatus

Abstract

To provide a forming apparatus which allows for improved position-dependent deactivation of radiation detectors, and a method of operating a forming apparatus.SOLUTION: A safety control part (10) makes comparison between a first status signal (a) generated by comparing a first actual position value obtained by adding a first position correction value and a first position value with a first deactivated position value for deactivating the first radiation detector (23) and a second status signal (b) generated by comparing a second actual position value obtained by adding a second position correction value and a second position value to a first deactivated position value, and performs deactivation when the first status signal (a) and the second status signal (b) match.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a molding apparatus comprising a machine bed, a tool carrier housed in the machine bed and movable relative to it, a mechanical control unit for controlling a drive unit, a safety control unit for shutting off the drive unit, and a position measuring system incorporated into the drive unit, wherein a first tool is positioned on the machine bed, a second tool and a drive unit for moving the tool carrier are incorporated into the tool carrier, the second tool together with the first tool to determine a variable-size work gap, the safety control unit is connected to at least one radiation source and a plurality of radiation detectors positioned opposite the radiation source, at least a portion of the beam emitted from the radiation source is aligned along the work edge of the first tool, and the position measuring system is formed to provide a position signal depending on the position of the tool carrier, wherein the mechanical control unit has a first path measuring system for periodically processing the position signal in a first high-speed work cycle into a first position value, and the safety control unit has a second path measuring system for periodically processing the position signal in a second low-speed work cycle into a second position value. Furthermore, the present invention relates to a method for operating the molding apparatus.

[0002] Patent Document 1 discloses a molding apparatus comprising a machine bed, a relative movable tool carrier housed in the machine bed and connected to a drive unit, a mechanical control unit for controlling the drive unit, a monitoring device formed for monitoring the movement of the tool carrier and for controlling a separation device upstream of the drive unit, and two path measuring systems, each formed for outputting a position signal for determining the position of the tool carrier opposite the machine bed. In this apparatus, the first path measuring system is formed to periodically provide a first position signal in a first high-speed work cycle, and the second path measuring system is formed to periodically provide a second position signal in a second low-speed work cycle, and deactivation occurs in at least one radiation detector when, during comparison, the difference between the first and second position signals falls below a predetermined value.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The problem of the present invention is to provide a molding apparatus and a method for operating the molding apparatus that enable improved position-dependent deactivation of a radiation detector.

Means for Solving the Problems

[0005] This problem is solved for a molding apparatus of the type described at the beginning, in which the safety control unit is configured to perform a comparison between a first status signal and a second status signal for deactivating a first radiation detector at a pre-set first deactivation position. At that time, the first status signal is calculated by comparing the first actual position value obtained, particularly from the machine control unit, by adding a first position correction value to a first position value, with a first inactive position value, and the second status signal is calculated by comparing the second actual position value obtained, particularly from the safety control unit, by adding a second position value to a second position correction value, with the first inactive position value, and the safety control unit is configured to perform deactivation when the first status signal matches the second status signal.

[0006] Preferably, the first status signal and the second status signal are logical states, such as a logical high signal or a logical low signal. Preferably, the first status signal is intended to be output as a logical high signal when there is identity or substantial agreement (within a predetermined value interval) between the first actual position value and the first deactivation position value, and as a logical low signal otherwise. Furthermore, the second status signal is intended to be output as a logical high signal when there is identity or substantial agreement (within a predetermined value interval) between the second actual position value and the first deactivation position value, and as a logical low signal otherwise. In any case, the safety control unit has the task of determining the second status signal and performing a comparison between the first status signal and the second status signal. The first status signal can be determined by either the machine control unit or the safety control unit, in which case the first position value or the first actual position value is generated by the machine control unit in the latter case.

[0007] This method takes into account that the machine control unit lacks special safety measures for safety-oriented operation, meaning that the first position value and first actual position value calculated using the first position measurement system are more likely to be incorrect than the second position value and second actual position value calculated by a safety control unit that is designed for safety. Typically, the machine control unit has a single processor capable of performing the calculations necessary to control the molding machine, in which case the determination of the first position value and first actual position value is performed by this calculation, and thus the processor, including peripherals, forms the first path measurement system. Furthermore, for example, the second position value and second actual position value are intended to be calculated in the safety control unit using at least two microprocessors that work independently of each other and together form the second path measurement system. The second actual position value is output by this second path measurement system only if the second position value and second actual position value calculated by the two microprocessors match.

[0008] This method ensures that the first actual position value, the second actual position value, and the deactivation position value must coincide, thus enabling more reliable deactivation of the first radiation detector at the desired deactivation position. In the case of error effects that may affect both the first and second actual position values, comparing the first actual position value with the second actual position value and the first deactivation position value eliminates false deactivations with a greater probability than considering the deviation interval between the first and second position signals.

[0009] Preferably, the first position correction value is a first constant value, and the second position value is a second constant value, and these values ​​are stored in the safety control device and are adapted to the conditions of each forming apparatus.

[0010] Further advantageous configurations of the present invention are subject to dependent claims.

[0011] It is functional that the safety control unit is adjusted to deactivate the second radiation detector at a preset second deactivation position, specifically based exclusively on a second position value, where the distance between the first radiation detector and the second tool is greater than the distance between the second radiation detector and the second tool. In this case, it is assumed that upon reaching the first deactivation position, the approach speed between the first and second tools is reduced by corresponding control of the drive unit, and that the safety control unit makes a sufficiently accurate determination of the position of the second tool relative to the first tool, even in the second low-speed operating cycle. Therefore, the evaluation of the first position value, which is calculated by the machine control unit in the first high-speed operating cycle and has a higher probability of error, can be omitted here.

[0012] Preferably, the machine control unit is configured to calculate a first position correction value based on a first, in particular, maximum approach speed for the second tool to approach the first tool, and based on a first cycle time for a first work cycle, and the safety control unit is configured to calculate a second position correction value based on a first, in particular, maximum approach speed, and based on a second cycle time for a second work cycle.

[0013] The first position correction value is smaller than the second position correction value, and therefore reflects that the machine control unit is operating in a high-speed work cycle, resulting in a shorter first cycle time for calculating the first position value.

[0014] The first position correction value corresponds to the path the second tool takes relative to the first tool within the first cycle time, where the movement between the first and second tools is uniform. Therefore, the first actual position value obtained by adding the first position correction value and the first position value corresponds to the actual position of the second tool relative to the first tool.

[0015] The second position correction value corresponds to the path the second tool takes relative to the first tool within the second cycle time, and in this case, the movement between the first and second tools is also uniform. Therefore, the second actual position value obtained by adding the second position correction value and the second position value also corresponds to the actual position of the second tool relative to the first tool.

[0016] In a further configuration of the present invention, the safety control unit is intended to be configured such that the first radiation detector is deactivated only if the second actual position value occurs over time before the first actual position value. This ensures that the deactivation of the safety-related radiation detector is not performed too early (at which point the first radiation detector may already be switched off, potentially endangering users).

[0017] The present invention also relates to a method for operating a molding apparatus, wherein the method comprises the following steps, namely: A step of calculating a position signal from a position measuring system to calculate a variable interval over time between a first tool positioned on the machine bed and a second tool housed in the machine bed, fixed to a relative movable tool carrier, and determining a variable-size working interval together with the first tool. A step of processing a position signal into a first position value in a first path measurement system of a machine control unit, which is operated in a first high-speed work cycle, and a step of processing a position signal into a second position value in a second path measurement system of a safety control unit, which is operated in a second low-speed work cycle. In the safety control unit, the steps are: to process a first detection signal from a first radiation detector and to process a second detection signal from a second radiation detector, wherein these detectors are located in a first lateral end region of a second tool and are illuminated by a radiation source located opposite to the second end region of a second rule, wherein the distance of the first radiation detector relative to the second tool is greater than the distance of the second radiation detector relative to the second tool. In order to reduce the working distance between the first and second tools at the first, especially maximum, approach speed, if the working distance is greater than a preset distance, the machine control unit and the safety control unit release the energy supply for the drive unit connected to the tool carrier. A step of performing a comparison between a first status signal and a second status signal, wherein the first status signal is calculated by adding a first position correction value and a first position value and comparing the first actual position value obtained from the machine control unit or safety control unit with a first inactive position value, and the second status signal is calculated by adding a second position correction value and a second position value and comparing the second actual position value obtained from the safety control unit with the first inactive position value, and The method comprises the step of deactivating a first radiation detector when a first status signal and a second status signal match.

[0018] In a further configuration of the present invention, it is contemplated that upon deactivation of the first radiation detector, a switching of the drive device from the first approach speed to a second, particularly average, approach speed is carried out.

[0019] In a further configuration of this method, it is contemplated that when the second position value coincides with the second deactivation position, deactivation of the second radiation detector at the second deactivation position is carried out by the safety control device.

[0020] In a further configuration of this method, it is contemplated that upon deactivation of the second radiation detector, a switching of the drive device from the second approach speed to a third, particularly low, approach speed is carried out.

[0021] In a further embodiment of this method, it is contemplated that the first position correction value is determined based on the first approach speed and the first cycle time for the first working cycle, and the second position correction value is determined based on the first approach speed and the second cycle time for the second working cycle.

[0022] Preferably, in this method, the first deactivation position value has a first interval with respect to the first deactivation position for deactivating the first radiation detector, where the first interval is calculated such that the comparison between the first actual position value and the second actual position value is completed in the second safety control unit within the second working cycle before the tool carrier reaches the first deactivation position.

[0023] Advantageous embodiments of the present invention are described in the drawings.

Brief Description of the Drawings

[0024] [Figure 1] It is a schematic front view of a molding device. [Figure 2] It is a schematic diagram of the basic functional components of the molding device according to FIG. 1. [Figure 3] It is a flowchart for determining fade - out items. [Modes for carrying out the invention]

[0025] As shown in Figure 1, as an example, a forming machine formed as a die bending machine 1 comprises a machine bed 2 to which two guide rods 3 are attached, the guide rods being formed to support a tool carrier 4 so as to be able to move linearly. The tool carrier 4 can move linearly along the guide rods 3 in the vertical direction to move a male die 5, which is used as a tool and is referred to as the first tool, relative to a female die 6, which is referred to as the second tool. During the movement of the male die 5 in the closing movement direction 33, the working gap 20 between the male die 5 and the female die 6 is reduced. As a result, deformation of a workpiece (not shown), such as a metal plate, which can be inserted into the working gap between the male die 5 and the female die 6 becomes possible.

[0026] The die bending machine 1 is equipped with, for example, a monitoring device 7 consisting of multiple components, which is designed to minimize the risk of injury from the die bending machine 1 and to ensure a fast and trouble-free processing sequence for the workpiece to be processed. As an example, the monitoring device 7 is mounted on a tool carrier 4 and includes a light grid 21 having a transmitter 8 and a receiver 9. The transmitter 8 provides multiple detection beams 14, which are, in a typical example, aligned parallel to the longest edge 22 of the female die 6 and can be received by radiation detectors 23, 24, and 25 of the receiver 9.

[0027] The radiation detectors 23, 24, and 25 of the receiving device 9 each provide an electrical signal to the safety control unit 10 when the detection beam 14 of the light grid strikes each of the (not shown in detail) photosensitive radiation detectors 23, 24, and 25. Thus, the safety control unit 10 can determine, for example, which detection beam 14 is being blocked by interfering with the user in the hazardous area, and can provide an appropriate response depending on the size of the work gap 20.

[0028] Furthermore, the die bending machine 1 includes a machine control unit 11 that is electrically connected to a scanning device 27 of a position measuring system 12, a foot switch 15, and a safety control unit 10. The machine control unit 11 may, for example, be configured as a numerical computer control unit (CNC control unit, computer numerical control device). The machine control unit 11 allows the user to input information regarding the male die 5, the female die 6, the geometry of the workpiece (not shown), and the desired deformation of the workpiece, and from this, determines the movement sequence of the male die 5 relative to the female die 6. The foot switch 15 allows the operator to activate the movement sequence.

[0029] The position measurement system 12 includes a scanning device 27 and a glass scale 26 attached to one of the guide rods 3, which can be used as a physical measuring instrument and can be scanned non-contact (particularly optically) by the scanning device. The scanning device 27 is adjusted to provide an electrical position signal that can calculate the position of the male mold 5 relative to the female mold 6.

[0030] To initiate movement toward the tool carrier 4 and the male die 5 housed within it, as shown in Figure 1, the die bending machine 1 is equipped with a drive unit 37 that can be controlled by a machine control unit 11. As an example, the drive unit 37 comprises an electric motor 50 connected to a hydraulic pump 16, which is capable of providing oil flow to a hydraulic cylinder (not shown) assigned to a guide rod 3. For this purpose, the electric motor 50 is electrically connected to the machine control unit 11 to supply the necessary electrical energy. For a safe operating mode of the drive unit 37, a separator 17 is loop-connected to the electrical connection between the machine control unit 11 and the electric motor 50, and this separator 17 can be controlled by a safety control unit 10 and similarly forms a component of a monitoring device 7. In a modified example of the separator (not shown), the separator has a shut-off valve for the oil flow to the hydraulic cylinder and is accordingly located between the oil pump and the hydraulic cylinder.

[0031] Adaptation of the position of the light grid 21 to male molds 5 of different heights is made possible by housing the transmitter 8 and receiver 9 so that they can move linearly using the guide means 18 of the tool carrier 4. Preferably, the guide means 18 for the transmitter 8 and receiver 9 are movable and coupled to one another so as to ensure synchronous adjustment of the two guide means 18.

[0032] For example, the position measurement system 12 and the machine control unit 11 are formed according to the first safety category of the safety standard, while the safety control unit 10 is formed according to the second, higher safety category of the safety standard, thus intended to meet increased safety requirements. For example, the safety control unit 10 comprises at least two processors formed to perform similar calculation operations, which operate independently of each other, and which each alternately perform control, for example, to reduce the probability of incorrect positioning for the male mold 5 relative to the female mold 6.

[0033] The machine control unit 11 is configured to process the position signal provided by the scanning device 27 at a clock frequency of, for example, 1 kHz (also called the first work cycle). As a result, it is possible to provide a first position value that has already been output by the machine control unit 11 after a very short period of time (this period includes 1 millisecond or several milliseconds).

[0034] In contrast, the safety control unit 10 is significantly slower because, based on the high safety category requirements that underlie the safety control unit 10, it requires more extensive calculation and inspection of the second position value calculated based on the position signal. As a result, the output of the second position value by the safety control unit 10 is performed at a low clock frequency, for example, 100 Hz.

[0035] As a result, the position signal provided by the scanning device 27 is provided by the machine control unit 11 as a first position value, for example, after 1 millisecond, but can only be used as a second position value by the safety control unit 10 after 10 milliseconds. Consequently, the first position value cannot be directly compared with the second position value.

[0036] In order to enable meaningful comparison between the first position value and the second position value, and in particular to enable deactivation of the radiation detectors 23, 24, and 25 depending on the position of the male 5, the machine controller 11 is intended to provide the safety control unit 10 with the most recent first position value, and the safety control unit 10 is intended to perform further processing on the first and second position values.

[0037] For this purpose, in order to maintain the first actual position value, the safety control unit 10 is intended to add a first position correction value to the current first position value provided by the machine control unit 11. Furthermore, in order to maintain the second actual position value, the safety control unit is intended to add a second position correction value to each current second position value. Subsequently, the safety control unit 10 can compare the first actual position value, the second actual position value, and the deactivation position value stored in the safety control unit 10. As an example, the deactivation of the first radiation detector 23 may be intended to occur immediately before the interruption of the assigned detection beam 14 due to the tool carrier 4 equipped with the light grid 21 approaching the female mold 6. This prevents the safety orientation of the drive unit 37 from being shut off by the safety control unit 10 and the isolation device connected thereto.

[0038] As an example, the first position correction value is intended to be calculated to correspond to the distance the tool carrier 4 travels at the first closing speed, particularly the maximum closing speed, during the period required for the machine control 11 to calculate the first position value. Furthermore, as a mere typical example, the second position correction value is intended to be calculated to correspond to the distance the tool carrier travels at the first closing speed during the period required for the safety control unit 10 to calculate the second position value.

[0039] The first deactivation position value corresponds to the position of the tool carrier 4, which has a male mold 5 attached to the tool carrier, relative to the female mold 6, where the female mold 6 is a distance of first interval from the position of the tool carrier 4, such that the detection beam 14 hitting the first radiation detector 23 must cause the first radiation detector 23 to fade out in order to prevent interruption of the female mold 6 during the reduction of the working interval 20. In this case, the first interval corresponds to the distance the tool carrier 4 moves at a first closing speed during the period required for the safety control unit 10 to make a comparison between the first actual position value, the second actual position value, and the first deactivation position value.

[0040] A schematic diagram of the procedure for deactivating the first radiation detector 23 can be seen in Figure 3. In this case, the position signal from the position measurement system 12 is intended to be provided to the safety control unit 10 and the machine control unit 11 via a signal line 51 connected to the scanning device 27.

[0041] In the machine control unit 11, the first position value x(t) is calculated from the position signal s(t), and it is assumed, as a mere typical example, that this calculation is performed within a certain period corresponding to the first work cycle of the machine control unit 11. In the safety control unit 10, the second position value y(t) is calculated, and it is assumed, as a mere typical example, that this calculation is performed within a certain period corresponding to the second work cycle of the safety control unit 10. In this case, the second work cycle of the safety control unit 10 is significantly longer than the first work cycle of the machine control unit 11, which leads to a situation where, for example, at the point when the second position value y(t10) calculated by the safety control unit 11 based on the position signal s(t10) can be output, the first position value x(t12) calculated by the machine control unit 11 based on the position signal s(t12) can already be output. Next, additional means are needed to check for the existence of conditions that are formulated to deactivate or fade out the first radiation detector, such that the position calculated by the safety control unit 10 and the mechanical control unit 11 coincides with the first deactivation position value.

[0042] For this purpose, the first position value x(t) output by the machine control unit 11 is transmitted to the safety control unit 10 and added to the first position correction value k1 as part of the first calculation operation 52 within the safety control unit 10, and then compared with the first deactivation position value z as part of the first calculation operation 52. Alternatively, the first calculation operation 52 and the comparison can be intended to be performed in the machine control unit 11. If the comparison is positive [t], the first calculation operation 52 outputs a logic high level a=1 to the first buffer 55, which is used as the first status signal. On the other hand, if this comparison is negative [f], the machine control unit 11 requests the updated first position value x(t+1) and outputs a logic low level a=0 to the first buffer 55.

[0043] Furthermore, the second position value y(t) calculated by the safety control unit 10 is added to the second position correction value k2 as part of the second calculation operation 53 in the safety control unit 10, and then compared with the first deactivation position value z as part of the second calculation operation 53. If this comparison is positive [t], the second calculation operation 53 outputs a logic high level b=1, which is used as the second status signal, to the second buffer 56. On the other hand, if this comparison is negative [f], the safety control unit 10 requests the updated first position value y(t+1), and outputs a logic low level b=0 to the second buffer 56.

[0044] Furthermore, the safety control unit 10 performs a third calculation operation 54, which involves comparing the logic level a (first status signal) stored in the first buffer 55 with the logic level b (second status signal) stored in the second buffer 56 and high-level 1. If the condition a=b=1 is met, the safety control unit 10 provides a fade-out signal 57. For example, the fade-out signal 57 can be used within the safety control unit 10 to interrupt processing from the sensor signal of the first radiation detector 23. As a result, changes in the signal level of the first radiation detector 23 are not transmitted to the separation device 17.

[0045] As an example, the die bending machine 1 can be operated as follows. First, a self-test of the light grid 21 is performed at the stationary position of the tool carrier 4 at the maximum distance from the machine bed 2 and the female die 6 attached to the machine bed. In this case, it is checked whether the detector beam 14 produces a corresponding signal when it hits the radiation detectors 23, 24, and 25. Furthermore, the positioning of the light grid 21's receiver 9 and transmitter 8 is performed using guide means 18, depending on the male die 5 housed in the tool carrier 4. In this case, the geometric shape of the male die 5 is taken into consideration as well as the stopping distance of the tool carrier 4, and this stopping distance can also be called the braking distance, and represents the distance the tool carrier 4 moves when an interruption of the light grid 21 is detected. In particular, this distance depends on the second operating cycle of the safety control device 10, the reaction time of the separation device 17, and their respective closing speeds, i.e., the approach speed of the male die 5 and female die 6. Preferably, the intention here is that the first radiation detector 23 is positioned away from the working edge 36 of the male mold 5 such that the distance between the first radiation detector 23 and the working edge 36 corresponds to at least the overtravel distance.

[0046] After the workpiece is placed on the female mold 6, the user can begin machining by activating the foot switch 15. For this purpose, a predetermined movement sequence relative to the male mold 5 is designed, which may include, for example, the following steps. In the first step after the activation of the foot switch 15, the tool carrier 4 is accelerated to a first closing speed, also referred to as "high speed" or "rapid." During this high-speed movement, monitoring of all radiation detectors 23, 24, and 25 is performed, for example. If, as the tool carrier 4 approaches the female mold 6, at least one interruption of the detection beam 14 is not detected by the radiation detectors 23, 24, and 25, the signal from the first radiation detector 23 is intended to fade out when a predetermined distance is reached between the male mold 5 and the female mold 6. This fade-out prevents the undesirable activation of the separation device 17, which would otherwise be caused by an interruption of the detection beam 14 hitting the radiation detector 23.

[0047] To implement this fade-out, the safety control device 10 and the machine control device 11 calculate their respective position values ​​using the position signal from the position measurement system 12. These position values ​​are then processed into actual position values ​​by the safety control device 10 using position correction values, and the actual position values ​​can be compared with the first deactivation position value to determine the first or second status signal. If the first status signal a and the second status signal b match, the first radiation detector 23 can be deactivated. Furthermore, to avoid the male mold 5 striking the workpiece, a switch from the first approach speed or closing speed to the second approach speed or closing speed can be performed at the time of the fade-out of the first radiation detector 23.

Claims

1. A molding apparatus (1) comprising a machine bed (2), a tool carrier (4) accommodated in the machine bed (2) and relatively movable, a machine control unit (11) for controlling a drive device (37), a safety control unit (10) for shutting off the drive device (37), and a position measurement system (12) incorporated in the drive device (37), wherein a first tool (6) is arranged on the machine bed (2), and the tool carrier (4) incorporates a second tool (5) and a drive device (37) for moving the tool carrier (4), and in this case, the second tool (5) together with the first tool (6) determines a working gap (20) of variable size the safety control unit (10) is connected to at least one radiation source (8) and a plurality of radiation detectors (23, 24, 25) arranged opposite to the radiation source (8), at least a part of the beam (14) emitted from the radiation source (8) is aligned along the working edge (36) of the first tool (6), the position measurement system (12) is formed to provide a position signal depending on the position of the tool carrier (4), and in this case, the machine control unit (11) has a first path measurement system for periodically processing the position signal in the first high-speed working cycle into a first position value, and the safety control unit (10) has a second path measurement system for periodically processing the position signal in the second low-speed working cycle into a second position value, in the molding apparatus, the safety control unit (10) is formed to perform a comparison between a first status signal (a) and a second status signal (b) for deactivating the first radiation detector (23) at a preset first deactivation position, the first status signal (a) is calculated by comparing a first actual position value obtained by adding a first position correction value to the first position value with the first inactive position value, the second status signal (b) is calculated by comparing a second actual position value obtained by adding a second position value to the first position correction value with the first inactive position value, the safety control unit (10) is formed to perform deactivation when the first status signal (a) coincides with the second status signal (b). The molding apparatus (1) is characterized by this.

2. The safety control unit (10) is adjusted such that the deactivation of the second radiation detector (24) is executed at a preset second deactivation position based on the second position value. At this time, the distance between the first radiation detector (23) and the second tool (5) is greater than the distance between the second radiation detector (24) and the second tool (5). The molding apparatus (1) according to claim 1 is characterized by this.

3. The machine control unit (11) is adjusted such that a first position correction value is calculated based on a first approach speed for the second tool (5) to approach the first tool (6) and based on a first cycle time for the first work cycle. The safety control unit (10) is adjusted such that a second position correction value is calculated based on the first approach speed and based on a second cycle time for the second work cycle. The molding apparatus (1) according to claim 1 or 2 is characterized by this.

4. The safety control unit (10) is adjusted such that the deactivation of the first radiation detector occurs only when the second actual position value occurs earlier in time than the first actual position value. The molding apparatus according to claim 1 or 2 is characterized by this.

5. A method for operating a molding apparatus (1), the method comprising the following steps, namely, Calculating a position signal of a position measurement system (12) to calculate a variable over time distance between a first tool (6) disposed on a machine bed (2) and a second tool (5) fixed to a tool carrier (4) accommodated in the machine bed (2) and relatively movable and determining a variable size working interval together with the first tool (6). Processing the position signal into a first position value in a first path measurement system of the machine control unit (11) operated in a first high-speed work cycle, and processing the position signal into a second position value in a second path measurement system of the safety control unit (10) operated in a second low-speed work cycle. In the safety control unit (10), processing a first detection signal of the first radiation detector (23) and processing a second detection signal of the second radiation detector (24). These detectors are disposed in a first side end region of the second tool (5) and are illuminated by a radiation source (8) disposed opposite to a second end region of the second rule (5). At that time, the step in which the distance between the first radiation detector (23) and the second tool (5) is larger than the distance between the second radiation detector (24) and the second tool (5). When the working interval (20) has a width larger than a preset width in order to reduce the width of the working interval (20) at the first approach speed between the first tool (6) and the second tool (5), the mechanical control unit (11) and the safety control unit (10) release the energy supply for the drive device (37) connected to the tool carrier (4). The step of performing a comparison between the first status signal (a) and the second status signal (b). At that time, the first status signal (a) is calculated by adding the first position correction value and the first position value and comparing the first actual position value obtained from the mechanical control unit (11) or the safety control unit (10) with the first inactive position value, and At that time, the second status signal (b) is calculated by adding the second position correction value and the second position value and comparing the second actual position value obtained from the safety control unit (10) with the first inactive position value, and The method characterized by comprising the step of deactivating the first radiation detector (23) when the first status signal (a) and the second status signal (b) match.

6. The method according to claim 5, characterized in that with the deactivation of the first radiation detector (23), the switching of the drive device (37) from the first approach speed to the second approach speed is executed.

7. The method according to claim 5 or 6, characterized in that when the second position value matches the second deactivation position, the deactivation of the second radiation detector (24) at the second deactivation position is executed by the safety control device (10).

8. The method according to claim 7, characterized in that with the deactivation of the second radiation detector (24), the switching of the drive device (37) from the second approach speed to the third approach speed is executed.

9. The method according to claim 5 or 6, characterized in that the first position correction value is determined based on the first approach speed and the first cycle time for the first working cycle, and the second position correction value is determined based on the first approach speed and the second cycle time for the second working cycle.

10. The first deactivation position value has a first interval with respect to a first deactivation position for deactivating the first radiation detector (23), wherein the first interval is calculated such that the comparison between the first actual position value and the second actual position value, which is performed by the second safety control unit (10) within the second work cycle, is completed before the tool carrier (4) reaches the first deactivation position. The method according to claim 5 or 6, characterized by this.

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