Cutting device and cutting control method

Abstract

To provide a cutting device and a cutting control method, which can reduce electrode wear due to arc cutting, and when arc cutting does not occur, can continue to perform plasma cutting while returning cutting parameters such as electric currents to a value set before an arc voltage increases even if the arc voltage increases.SOLUTION: A cutting device 100 according to the present invention comprises: a plasma torch 10 which has an electrode 11 and cuts a material W to be cut by jetting plasma arc P; a power supply part 30 that supplies the plasma torch 10 with electric power supplied from the outside; a voltage detecting part 40 that measures a voltage of the plasma arc P and outputs the measured value of the voltage; and a control part 50 that regularly monitors the measured value, and when the measured value exceeds a dropping determination threshold, reduces electric currents, which are supplied to the plasma torch 10 by the power supply part 30, from a steady-state value to an interrupted-state value, so as to transit the steady-state to an interrupted-state and maintains the state.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a cutting device and a cutting control method. [Background technology]

[0002] Conventionally, plasma cutting devices have been used to cut materials such as iron, stainless steel, and aluminum. In plasma cutting using a plasma cutting device, electrode materials and the like are consumed when the arc is extinguished. In order to reduce this electrode consumption, when an arc extinguishing command is received from an NC program, the plasma cutting device generally performs arc extinguishing sequence control (the control unit of the plasma cutting device or the plasma power source, etc., reduces the arc current and the pressure of the working gas to a specified value before extinguishing the arc).

[0003] In plasma cutting, when cutting a material into a hole shape, the end point of the cutting path of the plasma cutting device is set inside the hole. However, if the cutting path is not filled with material due to the fall-out of the remaining material inside the hole, the plasma arc is extended and the arc voltage rises sharply. When this voltage exceeds the allowable range of the plasma power source that holds the plasma arc, the plasma arc cannot be maintained and the arc is forcibly cut off. In this case, since the arc extinguishing sequence control is not performed, there is a problem that the electrode material is rapidly consumed. As a solution to this problem, for example, the plasma torch described in Patent Document 1 describes that by setting a protective voltage for the electrode in advance, when the arc voltage reaches the protective voltage during plasma cutting, the arc extinguishing sequence control is performed to cut off the plasma power source, thereby reducing electrode consumption. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 5-92272 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in plasma cutting, there are operations that accompany an increase in the arc voltage other than the above-mentioned case where the arc break occurs. For example, a plasma cutting operation (hereinafter referred to as a corner loop cutting operation) has been conventionally performed in which the cutting path of the plasma torch is looped to a corner so that the cutting path passes through the outside of the corner and does not pass through the inside of the corner. In this case, in the process of changing the torch angle of the plasma torch and correcting the tool, the arc voltage increases significantly compared to the steady voltage value, as in the corner loop cutting operation section shown in FIG. 11. Therefore, in the cutting method described in Patent Document 1, even in an operation that is not a situation in which the arc should be extinguished, such as the above-mentioned corner loop cutting operation, if the arc voltage reaches the protection voltage during plasma cutting, the plasma power supply may be shut off and the cutting operation may be stopped. In this case, the plasma arc must be reignited, which may cause a deterioration in work efficiency.

[0006] The present invention has been made in consideration of these circumstances, and aims to reduce electrode wear due to arc interruption, and, if arc interruption does not occur, even if an increase in arc voltage occurs, to restore cutting parameters such as current to values ​​before the arc voltage increased, thereby allowing plasma cutting to continue. [Means for solving the problem]

[0007] In order to solve the above problems, the present invention proposes the following means. A cutting device according to a first aspect of the present invention includes a plasma torch having an electrode and configured to cut a workpiece by spraying a plasma arc, a power supply unit configured to supply power supplied from an external source to the plasma torch, a voltage detection unit configured to measure a voltage of the plasma arc and output a measured value, and a control unit configured to constantly monitor the measured value, and when the measured value exceeds a drop determination threshold value, reduce a current supplied by the power supply unit to the plasma torch from a steady state value to an interrupt state value, thereby transitioning from the steady state to the interrupt state and maintaining the state. When the measured value falls below an increase determination threshold, the control unit increases the current from the interrupted state value to the steady state value, thereby returning to the steady state.

[0008] According to a second aspect of the present invention, in the cutting device according to the first aspect, the control unit includes a plurality of the descent determination thresholds.

[0009] According to a third aspect of the present invention, in the cutting device of the first or second aspect, the control unit increases the current from the interrupt state value to the steady state value when the measured value falls below the increase determination threshold, thereby returning to the steady state.

[0010] According to a fourth aspect of the present invention, in the cutting device according to the third aspect, the control unit is provided with a plurality of the rise determination thresholds.

[0011] According to a fifth aspect of the present invention, in the cutting device of the third or fourth aspect, the control unit compares the measurement value with the increase judgment threshold each time the measurement value falls below the increase judgment threshold and the current is increased, and determines whether to return to the steady state.

[0012] According to a sixth aspect of the present invention, in a cutting device relating to any one of the first to fifth aspects, the control unit compares the measurement value with the descent determination threshold each time the measurement value exceeds the descent determination threshold and the current is reduced, and determines whether to transition to the interrupt state.

[0013] According to a seventh aspect of the present invention, in the cutting device of any one of the first to sixth aspects, the control unit reduces the current and starts an arc extinction sequence for the plasma arc when the measured value exceeds an extinction judgment threshold that is higher than the drop judgment threshold.

[0014] A cutting control method according to an eighth aspect of the present invention includes the steps of: using a plasma torch having an electrode to spray a plasma arc to cut a workpiece; supplying power supplied from an external source to the plasma torch from a power supply unit; measuring the voltage of the plasma arc and outputting the measured value; constantly monitoring the measured value, and when the measured value exceeds a drop determination threshold, reducing the current supplied by the power supply unit to the plasma torch from a steady state value to an interrupt state value, thereby transitioning from the steady state to the interrupt state and maintaining the state; increasing the current from the interrupted state value to the steady state value when the measured value falls below an increase determination threshold, thereby returning to the steady state; Equipped with.

[0015] According to a ninth aspect of the present invention, in the disconnection control method according to the eighth aspect, a plurality of the descent determination thresholds are provided.

[0016] According to a tenth aspect of the present invention, the disconnection control method relating to the eighth or ninth aspect further includes a step of increasing the current from the interrupt state value to the steady state value and returning to the steady state when the measurement value falls below an increase determination threshold.

[0017] According to an eleventh aspect of the present invention, in the disconnection control method according to the tenth aspect, a plurality of the increase determination thresholds are provided.

[0018] According to a twelfth aspect of the present invention, the disconnection control method relating to the tenth or eleventh aspect further includes a step of comparing the measurement value with the increase judgment threshold each time the measurement value falls below the increase judgment threshold and the current is increased to determine whether to return to the steady state.

[0019] According to a thirteenth aspect of the present invention, the disconnection control method relating to any one of the eighth to twelfth aspects further includes a step of comparing the measurement value with the drop determination threshold each time the measurement value exceeds the drop determination threshold and the current is reduced to determine whether to transition to the interrupt state.

[0020] According to a fourteenth aspect of the present invention, the cutting control method relating to any one of the eighth to thirteenth aspects further includes a step of reducing the current and initiating an arc extinction sequence for the plasma arc when the measured value exceeds an extinction judgment threshold that is higher than the drop judgment threshold. Effect of the Invention

[0021] The cutting device and cutting control method of the present invention reduce electrode wear due to arc interruption, and if arc interruption does not occur, even if an increase in arc voltage occurs, cutting parameters such as current can be restored to the values ​​before the arc voltage increased, allowing plasma cutting to be continued. [Brief description of the drawings]

[0022] [Figure 1] 1 is a diagram showing an overall configuration of a plasma cutting device according to a first embodiment of the present invention; [Diagram 2] 13 is a table showing the relationship between the control parameter of the arc voltage and the current value, which is a controlled parameter, in each state of the plasma cutting device. FIG. [Diagram 3] 4 is a flow chart showing the control of the arc current by the control unit of the plasma cutting device. FIG. [Figure 4] 13 is a graph showing the relationship between arc current, arc voltage, and time when the plasma cutting device performs a corner loop cutting operation. FIG. [Diagram 5] 13 is a graph showing the relationship between arc current, arc voltage, and time when the plasma cutting device is performing an operation that causes an arc interruption. FIG. [Figure 6] FIG. 4 is a diagram showing the overall configuration of a plasma cutting device according to a second embodiment of the present invention. [Figure 7] 13 is a table showing the relationship between the control parameter of the arc voltage and the pressure value of the working gas pressure, which is a controlled parameter, in each state of the plasma cutting device. FIG. [Figure 8]13 is a graph showing the relationship between the pressure value of the working gas pressure, the arc voltage, and time when the plasma cutting device performs a corner loop cutting operation. FIG. [Figure 9] 13 is a graph showing the relationship between the pressure value of the working gas pressure, the arc voltage, and time when the plasma cutting device is performing an operation that causes an arc interruption. FIG. [Figure 10] 1A is a graph showing the relationship between the arc current, the arc voltage, and time when the plasma cutting device has completed a cutting operation, and FIG. 1B is a graph showing the relationship between the pressure value of the working gas pressure, the arc voltage, and time when the plasma cutting device has completed a cutting operation. [Figure 11] FIG. 1 is a graph showing the relationship between arc voltage and time when a conventional plasma cutting device cuts a corner loop. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] First embodiment A first embodiment of the present invention will be described with reference to FIGS.

[0024] FIG 1 is a diagram showing the overall configuration of a plasma cutting device (cutting device) 100 according to a first embodiment of the present invention. FIG 2 is a diagram showing the control parameter of the arc voltage V and the current value B which is a controlled parameter in each state of the plasma cutting device 100. x Fig. 3 is a flow diagram showing the control of the arc current A by the control unit 50 of the plasma cutting device 100. Fig. 4 is a graph showing the relationship between the arc current A, the arc voltage V, and time when the plasma cutting device 100 performs a corner loop cutting operation. Fig. 5 is a graph showing the relationship between the arc current A, the arc voltage V, and time when the plasma cutting device 100 performs an operation that causes an arc interruption.

[0025] The plasma cutting device (cutting device) 100 is a device that cuts a workpiece W placed on a substantially horizontal surface on a mounting table (not shown) by plasma cutting. The workpiece W is a member made of, for example, iron, stainless steel, aluminum, or the like.

[0026] As shown in FIG. 1, the plasma cutting device 100 includes a plasma torch 10, a working gas supply unit 20, a power supply unit 30, a voltage detection unit 40, and a control unit 50.

[0027] The plasma torch 10 can cut a workpiece W by spraying a plasma arc P. The plasma torch 10 includes an electrode 11 and a nozzle portion 12. A working gas passage 13 through which a working gas such as oxygen gas flows is formed between the electrode 11 and the nozzle portion 12. A base end portion 13b of the working gas passage 13 is connected to a working gas supply portion 20 via a hose or the like.

[0028] 1, the nozzle portion 12 has an outer diameter consisting of a tubular body with a conical tip end and a cylindrical base end provided on the lower side in a vertical direction perpendicular to a horizontal plane. The nozzle portion 12 has an internal space in which an electrode 11 is disposed. A nozzle hole 12a communicating with a tip end 13a of the working gas flow path 13 is formed at the tip of the nozzle portion 12.

[0029] As shown in Fig. 1, the electrode 11 has a cylindrical outer shape with a bottom at the tip side. The electrode 11 is detachably attached to the center position of the plasma torch 10. An electrode material 14 made of, for example, hafnium (or zirconium, or an alloy thereof), which is a high melting point material that can withstand the high heat of the plasma arc, is provided at the tip of the electrode 11. The electrode 11 can be cooled by circulating cooling water in the internal space of the electrode 11. The electrode 11 is made of a metal having a relatively high electrical conductivity, such as copper.

[0030] 1, the working gas supply unit 20 can supply a working gas (not shown) to the working gas flow passage 13. The working gas supplied from the working gas supply unit 20 to the base end 13b of the working gas flow passage 13 passes through the working gas flow passage 13 toward the tip end 13a and is ejected from the nozzle hole 12a of the nozzle portion 12.

[0031] As shown in FIG. 1, the power supply unit 30 supplies power supplied from an external source to the plasma torch 10. Specifically, the power supply unit 30 supplies an arc current (current) A between the electrode 11 of the plasma torch 10 and the workpiece W to generate a plasma arc P between the electrode 11 and the workpiece W. The power supply unit 30 is electrically connected to each of the electrode 11 and the workpiece W. The power supply unit 30 is also electrically connected to the nozzle unit 12 of the plasma torch 10. The power supply unit 30 supplies a predetermined current between the electrode 11 and the workpiece W using power supplied from a commercial power source or the like. Then, the plasma torch 10 can generate a plasma arc P. In this embodiment, the power supply unit 30 may supply a direct current or an alternating current.

[0032] 1, the voltage detection unit 40 is, for example, a voltage sensor that measures the arc voltage (voltage) V of the plasma arc P generated between the electrode 11 and the workpiece W and outputs the measured value. The voltage detection unit 40 is electrically connected to the power supply unit 30, the electrode 11, and the workpiece W, constantly measures the arc voltage V, and outputs the measured value.

[0033] 1, the control unit 50 is electrically connected to the power supply unit 30 and the voltage detection unit 40. As shown in FIG. 2, the control unit 50 calculates, as a control parameter, a drop determination threshold value C that can be arbitrarily set for the measured value of the arc voltage V that is constantly acquired from the voltage detection unit 40 during the plasma cutting operation of the plasma cutting device 100. x and the increase judgment threshold D x The control unit 50 controls the current value (interrupt state value) B of the arc current A when the arc voltage V falls below or exceeds a set threshold value based on the measured value of the arc voltage V. xThe arc current A can be maintained by controlling the parameters of the current B. x is set according to a plurality of states as shown in FIG. 2. The control unit 50 can transition to the steady state, the Xth interruption state, and the minimum interruption state according to the control parameters. In this embodiment, the Xth interruption state, the descent determination threshold C x , rise judgment threshold D x , current value B x , and the current amount F x Any integer can be set for N or n, which is assigned to X in the above formula.

[0034] Here, among the multiple states, a state in which the power supply unit 30 supplies power to the plasma torch 10, the plasma arc P is generated without any problems, and cutting work is performed is defined as a steady state. The arc voltage V of the plasma arc P at this time is a steady value C s The steady-state value C s is a voltage value lower than the drop determination threshold C0 at which the steady state transitions to the first interruption state. The steady value of the arc current A in the steady state is a current steady value (steady value) B0. When the measured value of the arc voltage V exceeds the drop determination threshold C0 in the steady state, the control unit 50 sets the current value (interruption state value) B x The parameters are changed to maintain the arc current A. This state is called the Xth interruption state. In this case, X is an integer equal to or greater than 1 and smaller than N or n. When the measured value of the arc voltage V is less than the drop determination threshold C n If the current exceeds the minimum current value B, the control unit 50 reduces the arc current A to the minimum current value B. min The arc current is maintained at A by displacing the arc to A. This state is called the minimum interruption state.

[0035] First, the control unit 50 determines a voltage drop determination threshold C based on the measured value of the arc voltage V. xand the measured value. When the measured value of the arc voltage V rises from the steady state and exceeds the drop determination threshold C0, the control unit 50 transitions to a first interruption state, performs internal processing for approximately Δt seconds, and then controls the arc current A by displacing the arc current A from the current steady value (steady value) B0 to a first current value B1 by the current amount F1. Next, when the measured value of the arc voltage V exceeds the drop determination threshold C1 and then exceeds the drop determination threshold C2, the control unit 50 transitions to a second interruption state, and controls the arc current A by displacing the arc current A from the first current value B1 to a second current value B2 by the current amount F2. Similarly, as shown in FIG. 2, the control unit 50 transitions to a second interruption state when the measured value of the arc voltage V rises from the steady state and exceeds the drop determination threshold C x-1 and the threshold C x When the current exceeds the X-1 current value B, the state transitions from the X-1 interrupt state to the X interrupt state. x-1 From the Xth current value B x Current amount F x The displacement is controlled by only one.

[0036] The control unit 50 further determines the descent determination threshold C n When the current exceeds the minimum current value B, the Nth interruption state is changed to the minimum interruption state. min Current amount F n Displace the current by the minimum value B min In this manner, the control unit 50 changes the arc current A from the steady-state current value B0 to the minimum current value B min and then transition to and maintain the suspended state.

[0037] Next, the control unit 50 detects that the measured value of the arc voltage V has dropped from the minimum interruption state and the rise determination threshold D min When the current falls below the minimum current value B, the system transitions to the Nth interruption state, and after performing internal processing for approximately △t seconds, the arc current A is reduced to the minimum interruption state minimum current value B. min From the Nth current value B n Current amount F n The control unit 50 controls the measured value of the arc voltage V by displacing the arc voltage V by a rise determination threshold D xEach time the measured value of the arc voltage V falls below the increase determination threshold D1, the control unit 50 transitions one by one through a number of stepwise set interruption states shown in FIG. 2, and displaces and controls the arc current A to match the interruption state. When the measured value of the arc voltage V falls below the increase determination threshold D1, the control unit 50 transitions from the first interruption state to a steady state, returns the arc current A to the current steady value B0, and maintains the steady state. In this way, the control unit 50 controls the arc current A to the minimum current value B min The current can be gradually increased from the steady state value B0 to the steady state value B1, and then the steady state can be restored and maintained.

[0038] In addition, the minimum current value B min is a value lower than the steady-state current value B0. min is set to a value that prevents the plasma arc P from being extinguished during plasma cutting while preventing the arc current A from taking too long to return to the steady-state current value B0. For example, the control unit 50 may set the minimum current value B min The minimum current value B is set to about 80A. min is set to approximately 80A so that the arc current A does not take too long to return to the steady-state current value B0, and so that the plasma arc P does not extinguish during plasma cutting. If the plasma arc P can be maintained at this value, the minimum current value B min may be 80A or less.

[0039] In addition, the amount of current F x is the Xth current value B x From the X-1 current value B x-1 The current amount F x is F1, F2, F3, ...F n current value B so that the current is the same x You can set the parameters of the current B to obtain different current amounts. x The parameters may be set as follows.

[0040] The descent determination threshold C of the control unit 50 x and the increase judgment threshold D x is always the descent judgment threshold C x > Rise judgment threshold Dx The following relationship holds. In addition, the descent judgment threshold C x is the descent judgment threshold C x In addition, the rise judgment threshold D x is not provided in the steady state.

[0041] In this embodiment, the time required for the internal processing is set to about Δt seconds, but the time required for the internal processing is not particularly limited. Also, the control unit 50 constantly obtains the measured value of the arc voltage V from the voltage detection unit 40. Therefore, the control unit 50 constantly monitors the arc voltage V against each set threshold value.

[0042] With the above configuration, the control unit 50 constantly compares the measured value of the arc voltage V with the control parameters to determine whether to transition to each state. x The control unit 50 can change the arc current A stepwise from the steady-state current value B0 to the minimum current value B min 2, when the minimum interruption state is reached, the control unit 50 reduces the arc current A to a minimum current value B so that the plasma arc P is not extinguished. min The control unit 50 controls the arc current A to a minimum current value B min The current can be gradually increased from the steady state value B0 to the steady state value B1, and then the steady state can be restored and maintained.

[0043] (action) Next, the operation of the plasma cutting device 100 according to this embodiment will be described with reference to Fig. 2, Fig. 3, Fig. 4, and Fig. 5. Fig. 2 shows the control parameter of the arc voltage V and the current value B xFig. 3 is a flow diagram showing the control of the arc current A by the control unit 50 of the plasma cutting device 100. Fig. 4 is a graph showing the relationship between the arc current A, the arc voltage V, and time when the plasma cutting device 100 performs a corner loop cutting operation. Fig. 5 is a graph showing the relationship between the arc current A, the arc voltage V, and time when the plasma cutting device 100 performs an operation that causes an arc interruption.

[0044] First, the plasma cutting device 100 injects working gas from the nozzle hole 12a, and applies a current between the electrode 11 of the plasma torch 10 and the workpiece W by the power supply unit 30 to form a plasma arc (main arc) P, thereby starting plasma cutting. Then, the voltage detection unit 40 measures the arc voltage V of the plasma arc P. In addition, the control unit 50 constantly acquires the measured value of the arc voltage V from the voltage detection unit 40, and starts controlling the arc current A of the power supply unit 30.

[0045] (Step S10) In step S10, the control unit 50 constantly monitors whether the measurement value of the arc voltage V acquired from the voltage detection unit 40 exceeds the drop determination threshold C0. If the acquired measurement value of the arc voltage V exceeds the drop determination threshold C0, as shown in Fig. 4 and Fig. 5, the control unit 50 proceeds to step S11. If the acquired measurement value of the arc voltage V does not exceed the drop determination threshold C0, the control unit 50 constantly monitors again whether the measurement value of the arc voltage V acquired from the voltage detection unit 40 exceeds the drop determination threshold C0.

[0046] (Step S11) Next, in step S11, the control unit 50 transitions from the steady state to the first interruption state. Specifically, the control unit 50 controls the current value of the arc current A by shifting it from the steady current value B0 to the first current value B1 by the current amount F1, as shown in Fig. 4 and Fig. 5. Next, the process proceeds to step S12.

[0047] (Step S12) In step S12, the control unit 50 determines whether the measured value of the arc voltage V obtained from the voltage detection unit 40 is equal to or lower than the drop determination threshold C x 4 and 5, the control unit 50 constantly monitors whether the measured value of the arc voltage V exceeds the drop determination threshold C x If the measured value of the arc voltage V exceeds the drop determination threshold C x If it does not exceed this, proceed to step S19.

[0048] (Step S13) Next, the control unit 50 transitions from the X-1th interruption state to the Xth interruption state. Specifically, the control unit 50 changes the current value of the arc current A to the X-1th current value B x-1 From the Xth current value B x Current amount F x Then, the process proceeds to step S14.

[0049] (Step S14) Next, in step S14, the control unit 50 determines whether the measured value of the arc voltage V obtained from the voltage detection unit 40 is equal to or lower than the drop determination threshold C n As shown in FIG. 4, the control unit 50 constantly monitors whether the acquired measurement value of the arc voltage V exceeds the drop determination threshold C n If the measured value of the arc voltage V exceeds the drop determination threshold C n If it does not exceed this, proceed to step S16.

[0050] (Step S15) Next, in step S15, the control unit 50 transitions from the Nth interruption state to the minimum interruption state. Specifically, as shown in FIG. 4, the control unit 50 changes the current value of the arc current A to the Nth current value B n to minimum current value B min Current amount F n Then, the process proceeds to step S16.

[0051] (Step S16) In step S16, the control unit 50 determines whether the measured value of the arc voltage V obtained from the voltage detection unit 40 exceeds the rise determination threshold D min As shown in FIG. 4, the control unit 50 constantly monitors whether the acquired measurement value of the arc voltage V falls below the rise determination threshold D min If the measured value of the arc voltage V is lower than the increase determination threshold D, the process proceeds to step S18. min If it is not less than this, proceed to step S17.

[0052] (Step S17) 5, when the plasma arc P is interrupted, the plasma arc P is not generated. The arc current A drops to 0 A when the plasma arc P is interrupted at the arc interruption point K. Then, the control unit 50 completes the control of the arc current A of the power supply unit 30.

[0053] (Step S18) In step S18, the control unit 50 transitions from the minimum interruption state to the Nth interruption state. Specifically, as shown in FIG. 4, the control unit 50 sets the current value of the arc current A to a minimum current value B min From the Nth current value B n Current amount F n Then, the process proceeds to step S19.

[0054] (Step S19) Next, in step S19, the control unit 50 determines whether the measured value of the arc voltage V obtained from the voltage detection unit 40 is greater than or equal to the rise determination threshold D x In this case, X is an integer greater than 1 and equal to or less than n. As shown in FIG. 4, the control unit 50 constantly monitors whether the acquired measurement value of the arc voltage V falls below the rise determination threshold D x If the measured value of the arc voltage V is lower than the increase determination threshold D x If it is not less than this, proceed to step S12.

[0055] (Step S20) Next, in step S20, the control unit 50 transitions from the Xth interruption state to the X-1th interruption state. Specifically, as shown in FIG. 4, the control unit 50 changes the current value of the arc current A to the Xth current value B. x From the X-1 current value B x-1 Current amount F x Then, the process proceeds to step S21.

[0056] (Step S21) Next, in step S21, the control unit 50 constantly monitors whether the measured value of the arc voltage V acquired from the voltage detection unit 40 falls below the increase determination threshold D1. As shown in Fig. 4, if the acquired measured value of the arc voltage V falls below the increase determination threshold D1, the control unit 50 proceeds to step S20. If the measured value of the arc voltage V does not fall below the increase determination threshold D1, the control unit 50 proceeds to step S12.

[0057] (Step S22) Next, in step S22, the control unit 50 returns from the first interruption state to the steady state. Specifically, the control unit 50 controls the current value of the arc current A by shifting it from the first current value B1 to the current steady value B0 by the current amount F1, as shown in Fig. 4. Next, the process proceeds to step S23.

[0058] (Step S23) In step S23, if the cutting operation by the plasma cutting device 100 is to be continued, the control unit 50 returns to the first step and continues to constantly monitor the measured value of the arc voltage V. If the cutting operation is completed, the control unit 50 completes the control of the arc current A of the power supply unit 30.

[0059] In the plasma cutting device 100 of this embodiment, with the above-mentioned configuration, the descent determination threshold C x and the rise judgment threshold D x The control unit 50 constantly monitors the arc voltage V against the set drop determination threshold C x When the arc current A exceeds the steady-state current value B0, the arc current A is changed to the current value Bx to transition from the Steady state to the Suspended state and maintain it there.

[0060] In this embodiment, the control unit 50 determines whether the measured value of the arc voltage V is greater than or equal to the set rise determination threshold D x When the arc current A falls below the current value B in each state, x to the current steady-state value B0, and return from the interrupted state to the steady-state state. Therefore, even if the arc voltage V becomes higher than the normal arc voltage V value in an operation that does not require arc extinguishing, such as a corner loop cutting operation, the control unit 50 can reduce the arc current A without suddenly extinguishing the arc. Also, the plasma cutting device 100 can continue to perform the plasma cutting operation, and the efficiency of the plasma cutting operation can be improved.

[0061] In this embodiment, the control unit 50 determines the descent determination threshold C x and the rise judgment threshold D x The control unit 50 detects whether the acquired measurement value of the arc voltage V is equal to or smaller than the set drop determination threshold C x Exceeding or rising threshold D x Each time the arc voltage V falls below 0.001 V, the control unit 50 compares the measured value of the arc voltage V with the control parameters to determine whether to transition to an interrupted state or to return to a steady state. Therefore, even if the arc voltage V suddenly rises, the control unit 50 can maintain the current value B of the arc current A. x can be changed stepwise, and even if an arc interruption occurs, the arc current A is changed to a sufficiently low value, so the control unit 50 can reduce wear on the electrode 11. Furthermore, the plasma cutting device 100 can extend the life of the electrode 11. Moreover, the plasma cutting device 100 can maintain a steady melting state without applying a sudden thermal change to the electrode 11.

[0062] Furthermore, in this embodiment, the plasma cutting device 100 does not perform unnecessary arc extinguishing, and therefore the time required to restore the plasma cutting operation caused by such extinguishing is not required.

[0063] It should be noted that the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the invention.

[0064] Second Embodiment Next, a second embodiment of the present invention will be described with reference to Figs. 6 to 9. In the following description, the same components as those already described will be denoted by the same reference numerals, and duplicated description will be omitted. Note that the following embodiments are all different from the first embodiment in the working gas supply unit 20A and the control unit 50A. Therefore, the following description will focus on the differences from the first embodiment.

[0065] 6 is a diagram showing the overall configuration of a plasma cutting device 100A according to a second embodiment of the present invention. FIG. 7 shows the control parameter of the arc voltage V in each state of the plasma cutting device 100A and the pressure value E of the working gas pressure S, which is a controlled parameter. x 8 is a table showing the relationship between the pressure value E of the working gas pressure S when the plasma cutting device 100A performs a corner loop cutting operation. x 9 is a graph showing the relationship between the pressure value E of the working gas pressure S when the plasma cutting apparatus 100A is performing an operation that causes an arc interruption, and the arc voltage V and time. x , arc voltage V, and time. A plasma cutting device 100A according to the second embodiment of the present invention includes a plasma torch 10, a working gas supply unit 20A, a power supply unit 30, a voltage detection unit 40, and a control unit 50A, as shown in Fig. 1. The plasma torch 10, the power supply unit 30, and the voltage detection unit 40 are all similar to those in the first embodiment, and therefore description thereof will be omitted.

[0066] The working gas supply unit 20A has a function of supplying the working gas (not shown) of the working gas supply unit 20 according to the first embodiment to the working gas flow path 13, and is equipped with a solenoid valve (not shown), and is electrically connected to the control unit 50A as shown in Fig. 6. The working gas supply unit 20A controls the pressure value E of the working gas pressure S by the control unit 50A.x is controlled by a solenoid valve (not shown).

[0067] 6, the control unit 50A is electrically connected to an electromagnetic valve (not shown) in addition to the first embodiment. The control unit 50A has a descent determination threshold C x and the increase judgment threshold D x When the arc voltage V is below or above a set threshold based on the measured value of the arc voltage V, the control unit 50A controls the current value (interrupt state value) B of the arc current A according to the first embodiment as shown in FIG. x In addition to controlling and maintaining the parameters of the working gas pressure S, the pressure value E x The parameters of the working gas pressure S and the pressure value E x is the current value B of the arc current A in Figure 2. x As shown in FIG. 7, the parameters are set according to multiple states. Here, the current value B of the arc current A is x The control of the parameters is the same as in the first embodiment, and therefore the description will be omitted. In this embodiment, as in the first embodiment, any integer can be set for N or n substituted for X. The steady value of the working gas pressure S in the steady state is the steady value E0.

[0068] In comparison with the first embodiment, the control unit 50A has a configuration in which the controlled parameter is the current value B of the arc current A shown in FIG. x and the pressure value E of the working gas pressure S shown in FIG. x In this case, the control is performed as follows. First, the control unit 50A sets the voltage drop determination threshold C x When the measured value of the arc voltage V rises from the steady state and exceeds the drop determination threshold C0, the control unit 50A transitions to the first interruption state, performs internal processing for about Δt seconds, and then compares the current value B of the arc current A with the measured value C of the arc current A. xNext, when the measured value of the arc voltage V exceeds the drop determination threshold C1 and then exceeds the drop determination threshold C2, the control unit 50A transitions to a second interruption state and controls the current value B of the arc current A to be changed by a pressure amount G1 from the steady-state value E0 to the first pressure value E1. x 7, the control unit 50A controls the working gas pressure S by changing the working gas pressure S from the first pressure value E1 to the second pressure value E2 by a pressure amount G2. x-1 and the threshold C x When the current value B of the arc current A exceeds the threshold, the state transitions from the X-1 interruption state to the X interruption state. x The working gas pressure S is controlled to the X-1 pressure value E x-1 From the Xth pressure value E x Pressure G x The displacement is controlled by only one.

[0069] The control unit 50A further determines the descent determination threshold C n When the current value B of the arc current A exceeds the threshold, the state transitions from the Nth interruption state to the minimum interruption state. x and at the same time, the working gas pressure S is controlled to the minimum pressure value E min Pressure G n Displace the pressure by the minimum pressure value E min In this manner, the control unit 50A changes the arc current A from the steady-state current value B0 to the minimum current value B min Then, the operating gas pressure S is gradually decreased from the steady state E0 to the minimum pressure value E1. min and then transition to and maintain the suspended state.

[0070] Next, the control unit 50A detects whether the measured value of the arc voltage V falls from the minimum interruption state and whether the rise determination threshold D min When the current value of arc current A falls below , it transitions to the Nth interrupt state, and after performing internal processing for about △t seconds, the current value of arc current A becomes B x and at the same time, the working gas pressure S is set to the minimum pressure value E in the minimum interruption state. min to the Nth pressure value E n Pressure Gn The control unit 50A controls the measured value of the arc voltage V by displacing the arc voltage V by a rise determination threshold D x Each time the arc current A falls below the current value B, the arc current A transitions one by one through the multiple interrupt states shown in Figure 7, which are set in stages. x When the measured value of the arc voltage V falls below the rise determination threshold D1, the control unit 50A transitions from the first interruption state to the steady state and increases the current value B of the arc current A. x In addition, the control unit 50A controls the working gas pressure S to return to the steady state value E0 and maintains the steady state. min The current is gradually increased from the steady state value B0 to the steady state value B1, and the working gas pressure S is increased to the minimum pressure value E2. min to a steady state value E0, and then the steady state can be restored and maintained.

[0071] The minimum pressure value E min is a value lower than the steady-state value E0. min is set to a value that does not take long for the working gas pressure S to return to the steady-state value E0.

[0072] In addition, the pressure G x is the Xth pressure value E x From the X-1 pressure value E x-1 The current amount G x are G1, G2, G3, . . . G n The pressure value E x You can set the parameters of the pressure values ​​E x The parameters may be set as follows.

[0073] With the above configuration, the control unit 50A constantly compares the measured value of the arc voltage V with the control parameters to determine whether to transition to each state, and determines the current value B of the arc current A. x and the pressure value E of the working gas pressure S xThe control unit 50A can change the arc current A stepwise from the steady-state current value B0 to the minimum current value B min Then, the operating gas pressure S is gradually reduced from the steady state E0 to the minimum pressure value E min 7, when the control unit 50A enters the minimum interruption state, it reduces the working gas pressure S to the minimum pressure value E min Further, the control unit 50A controls the arc current A to a minimum current value B min The current is gradually increased from the steady state value B0 to the steady state value B1, and the working gas pressure S is increased to the minimum pressure value E2. min to a steady state value E0, and then the steady state can be restored and maintained.

[0074] The operation of this embodiment is substantially the same as that described in the first embodiment using the flow shown in Fig. 3. Therefore, the operation of the plasma cutting device 100A according to this embodiment will not be described. Figs. 8 and 9 show the operation of the plasma cutting device 100A according to the present embodiment, in addition to the current value control shown in Figs. 4 and 5 of the first embodiment, the pressure value E of the working gas pressure S to be controlled. x FIG.

[0075] In the plasma cutting device 100A of this embodiment, the control unit 50A determines the descent determination threshold C x and the rise judgment threshold D x The control unit 50A detects whether the acquired measurement value of the arc voltage V is equal to or smaller than the set drop determination threshold C x Exceeding or rising threshold D x Each time the arc voltage V falls below the current value B of the arc current A in the first embodiment, the control unit 50A compares the measured value of the arc voltage V with the control parameters and determines whether to transition to the interrupted state or to return to the steady state. x In addition to controlling the working gas pressure S, the pressure value E xTherefore, the plasma cutting apparatus 100A can further reduce wear on the electrode 11.

[0076] Although the second embodiment of the present invention has been described above in detail with reference to the drawings, the specific configuration is not limited to this embodiment, and design modifications and the like within the scope of the present invention are also included. In addition, the components shown in the above-mentioned embodiment and the modified examples shown below can be appropriately combined to form a configuration.

[0077] (Modification) The plasma cutting device of the present invention may be provided with a storage unit or the like that has a plurality of variable tables, for example, the table shown in FIG. 2 or FIG. 7 as one variable table, in accordance with the material and thickness of the cutting material, the groove angle, etc. In this way, the control unit 50, 50A can set the variable table in accordance with the application, and can store the current value B set in accordance with the plurality of states. x or pressure value E of working gas pressure S x can be changed arbitrarily.

[0078] The control unit of the plasma cutting device of the present invention may also be provided with an arc-extinguishing sequence. The arc-extinguishing sequence refers to the process of lowering the arc current A to 0 A and extinguishing the plasma arc P when the arc voltage exceeds the arc-extinguishing determination threshold at an arc-extinguishing determination threshold higher than the drop determination threshold set by the control unit. At this time, it is preferable to set the arc-extinguishing determination threshold to be slightly lower than the voltage value at the arc interruption point K described in the above embodiment. This allows the control unit of the plasma cutting device of the present invention to control the current by lowering it to 0 A.

[0079] Furthermore, the control unit of the plasma cutting device of the present invention may be provided with a completion arc-extinguishing sequence for extinguishing the plasma arc when the plasma cutting device has completed a cutting operation, thereby completing the operation.

[0080] For example, as shown in Figures 10(a) and 10(b), the control unit 50, 50A according to the above-described embodiment controls the arc current A, or controls the working gas pressure S in addition to the arc current A. Figure 10(a) is a graph showing the relationship between the arc current A, the arc voltage V, and time when the plasma cutting device has completed a cutting operation. Figure 10(b) is a graph showing the relationship between the pressure value of the working gas pressure S, the arc voltage V, and time when the plasma cutting device has completed a cutting operation.

[0081] As shown in FIG. 10(a), the control unit 50, 50A compares the measured value of the constant arc voltage V with the control parameters and determines whether to transition to each state. Then, at the point L where the cutting operation is completed, the arc current A is lowered to 0 A to extinguish the plasma arc P, and the operation is completed. Also, as shown in FIG. 10(b), the control unit 50A compares the measured value of the constant arc voltage V with the control parameters and determines whether to transition to each state. Then, at the point L where the cutting operation is completed, the working gas pressure S is lowered to a sufficiently low value to extinguish the plasma arc P, and the operation is completed. As described above, when the plasma cutting device completes the cutting operation, the control unit 50, 50A can perform a completion extinguishing sequence and extinguish the plasma arc to complete the operation. Note that in the present invention, the control unit may perform the completion extinguishing sequence by controlling only the arc current A, or may control the working gas pressure S in addition to controlling the arc current A.

[0082] In this embodiment, the control unit 50, 50A determines the descent determination threshold C x and the increase judgment threshold D x Therefore, the number of the descent judgment thresholds C x and the increase judgment threshold D x The number of is not particularly limited.

[0083] In the above embodiment, the control unit 50, 50A determines the minimum current value (interrupt state value) B min The control unit of the present invention sets the minimum current value B to about 80A as long as the plasma arc P can be maintained.min may be set to 80A or less.

[0084] Furthermore, the plasma cutting device (cutting device) of the present invention is not limited to corner loop cutting operations as shown in Figures 4 and 8 or operations in which arc interruption occurs as shown in Figures 5 and 9, but can be used in all situations in which an abnormal increase in arc voltage V occurs.

[0085] In the above embodiment, the workpiece W is placed on a horizontal surface, but the surface does not have to be horizontal, and the workpiece W may be inclined with respect to the horizontal surface.

[0086] The control unit of the present invention may be provided as a separate unit from the plasma cutting device 100. For example, the control unit may be a device (computer) capable of executing an NC program and equipped with a processor, a storage unit such as a memory, a ROM, a RAM, or a HDD, etc., capable of storing the cutting method and the shape and size of the workpiece as a database.

[0087] Furthermore, in the above embodiment, the voltage detection unit 40 is a voltage sensor, but this is not particularly limited in the present invention, and the voltage detection unit may be a detection device other than a voltage sensor.

[0088] In addition, the control unit of the plasma cutting device of the present invention may further have the function of controlling the arc current A by acquiring commands from a conventionally known NC program or by acquiring signals, etc. from the cutting device and the power supply unit.

[0089] In addition, the plasma cutting device of the present invention may further include a drive unit that can move the plasma torch over the workpiece W placed on a horizontal surface during cutting, or move the plasma torch up and down in the vertical direction.

[0090] In any of the above embodiments, the cutting device and cutting control method of the present invention reduce electrode wear due to arc interruption, and if arc interruption does not occur, even if an increase in arc voltage occurs, cutting parameters such as current can be restored to the values ​​before the arc voltage increased, allowing plasma cutting to be continued. [Industrial Applicability]

[0091] The cutting device and cutting control method of the present invention reduce electrode wear due to arc interruption, and if arc interruption does not occur, even if an increase in arc voltage occurs, cutting parameters such as current can be restored to the values ​​before the arc voltage increased, allowing plasma cutting to be continued, and therefore are industrially applicable. [Explanation of symbols]

[0092] 100, 100A Plasma cutting device (cutting device) 10 Plasma Torch 11 electrodes 12 Nozzle section 20, 20A Working gas supply unit 30 Power supply section 40 Voltage detection section 50, 50A Control Unit A Arc current V Arc voltage S Working gas pressure P Plasma Arc K Arc break point L The point where the cutting operation is completed W Material to be cut C s Steady-state value (of arc voltage V) C x Descent threshold D x Increase judgment threshold B x Current value (interrupt state value) B0 (arc current A) steady-state current value (steady-state value) E x Pressure Value E0 (operating gas pressure S) steady state value

Claims

1. A plasma torch having an electrode and configured to cut a workpiece by ejecting a plasma arc; A power supply unit that supplies power supplied from an external source to the plasma torch; a voltage detection unit that measures the voltage of the plasma arc and outputs the measured value; a control unit that constantly monitors the measured value, and when the measured value exceeds a descent determination threshold, reduces the current supplied by the power supply unit to the plasma torch from a steady state value to an interrupt state value, thereby transitioning from the steady state to the interrupt state and maintaining it there; Equipped with The control unit increases the current from the interruption state value to the steady state value when the measured value falls below an increase determination threshold, thereby returning to the steady state. Cutting device.

2. The control unit has a plurality of the descent determination thresholds.

2. The cutting device of claim 1.

3. The control unit has a plurality of the increase determination thresholds.

3. A cutting device according to claim 1 or 2.

4. The control unit compares the measurement value with the increase determination threshold each time the measurement value falls below the increase determination threshold and the current is increased to determine whether to return to the steady state. A cutting device according to any one of claims 1 to 3.

5. The control unit compares the measurement value with the drop determination threshold each time the measurement value exceeds the drop determination threshold and the current is reduced to determine whether to transition to the interrupt state. A cutting device according to any one of claims 1 to 4.

6. When the measured value exceeds an arc extinction determination threshold that is higher than the drop determination threshold, the control unit reduces the current and starts an arc extinction sequence for the plasma arc. A cutting device according to any one of claims 1 to 5.

7. A step of cutting a workpiece by spraying a plasma arc using a plasma torch having an electrode; supplying power externally supplied from a power supply unit to the plasma torch; measuring a voltage of the plasma arc and outputting the measured value; a step of constantly monitoring the measured value, and when the measured value exceeds a drop determination threshold, reducing the current supplied by the power supply unit to the plasma torch from a steady state value to an interrupt state value, thereby transitioning from the steady state to the interrupt state and maintaining the state; increasing the current from the interrupted state value to the steady state value when the measured value falls below an increase determination threshold, thereby returning to the steady state; A cutting control method comprising:

8. The descent determination threshold is provided in a plurality of ways. The method of controlling disconnection according to claim 7.

9. The increase determination threshold is provided in plurality. The disconnection control method according to claim 7 or 8.

10. The method further includes a step of comparing the measured value with the increase determination threshold each time the measured value falls below the increase determination threshold and the current is increased to determine whether or not to return to the steady state. The disconnection control method according to any one of claims 7 to 9.

11. The method further includes a step of comparing the measurement value with the drop determination threshold each time the measurement value exceeds the drop determination threshold and the current is reduced to determine whether to transition to the suspend state. The disconnection control method according to any one of claims 7 to 10.

12. When the measured value exceeds an arc-extinguishing determination threshold that is higher than the drop determination threshold, the current is reduced to initiate an arc-extinguishing sequence for the plasma arc. A method for controlling disconnection according to any one of claims 7 to 11.

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