JP2011079033A - Plasma cutting method and plasma cutting apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To fix the height position of a plasma cutting torch when a change in a cutting speed exceeds a fixed reference without intervening in a cutting program. <P>SOLUTION: A plasma cutting method is provided in which a change in plasma arc voltage is measured and the height of a torch 1 from a material B to be cut is adjusted when the torch 1 is moved and the material B to be cut is cut while a plasma arc is jetted toward the material B from an electrode 2 provided in the torch 1, In the method, a change in the moving speed of the torch 1 is measured, and when it is recognized that the change in the measured moving speed of the torch 1 is higher than the preset change, the height position of the torch 1 is fixed, and regardless of the change in the arc voltage applied to the electrode 2, the fixed height position is held and cutting is performed. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a plasma cutting method for cutting by injecting a plasma arc toward a material to be cut, and in particular, the position of the plasma cutting torch in the height direction when the moving speed of the plasma cutting torch changes rapidly. The present invention relates to a plasma cutting method that can be fixed, and a plasma cutting apparatus that performs the plasma cutting method.

  When cutting a material to be cut typified by a steel plate, a gas cutting method, a plasma cutting method, or a laser cutting method is selectively performed. In these cutting methods, a cutting torch corresponding to each cutting method is arranged above the material to be cut and moved in a desired direction while injecting flame, cutting oxygen, plasma arc, laser light and assist gas, Cutting is performed on the workpiece. In these cutting methods, in order to ensure cutting quality, the distance (height) of the cutting torch from the material to be cut is kept at a substantially constant value during cutting.

  In the gas cutting method and the laser cutting method, the cutting torch is configured to be moved up and down by a lifting device, and a sensor such as a laser sensor or a capacitive sensor is disposed around the cutting torch. . When the distance measured by the sensor changes from a preset distance, the height is controlled by driving the lifting device so as to eliminate the change at this time.

  As described above, in the configuration in which sensors are arranged around the cutting torch, the height of the cutting torch is controlled by directly measuring the distance from the material to be cut by these sensors. For this reason, even if the cutting speed changes, the height of the cutting torch related to this change can be maintained in a substantially constant range.

  On the other hand, in the plasma cutting method, an electrode provided on a plasma cutting torch and a material to be cut are connected via a power source, and a plasma arc is formed by supplying a plasma gas around the electrode and energizing it. In particular, in the plasma cutting method, a constant current control is performed on the plasma power source when discharging between the electrode and the material to be cut, and the voltage (arc voltage) at the time of forming the plasma arc is between the electrode and the material to be cut. Changes in response to changes in distance.

  For this reason, the plasma cutting method is generally configured to measure an arc voltage during cutting and to drive an elevating device that raises and lowers the plasma torch in response to a change in the measured arc voltage. is there. However, the arc voltage can be measured in a stable state while the cutting speed is substantially constant, but there is a problem that stable measurement cannot be performed while the cutting speed is changing rapidly.

  In order to solve such a problem, the technique of Patent Document 1 has been proposed. In this technique, on the cutting program for a preset material to be cut, a copy prohibition section is set corresponding to the change start teaching point and the change end teaching point at which the cutting speed should be changed, and the plasma cutting torch is changed. The copying is prohibited when the start point is reached, and the copying is resumed when the change end point is reached. In this way, by setting the section where the cutting speed changes as the height-prohibiting prohibited section, cutting is performed while maintaining the height position of the plasma cutting torch even in a section where the arc voltage cannot be measured stably. Can proceed.

  Patent Document 1 describes an example of linearly cutting a material to be cut whose upper surface is substantially the same level and whose thickness changes clearly. For this reason, it is possible to clearly set the point at which the cutting speed should be changed and the cutting speed after the change, and it is easy to define the copying prohibited section.

  In the case of general plasma cutting, a figure constituted by a closed cutting line is cut from a single workpiece having the same thickness. In such cutting, when a figure other than a circle is cut, it is necessary to cut a corner portion having an angle, and a special shape such as a sharp projection portion may be cut.

  For example, in order to reduce the influence of inertia when cutting a corner portion, the cutting speed is reduced when entering the corner, and the cutting speed is increased when exiting from the corner. When cutting such a special shape including a corner portion or a protruding portion, as in the technique of Patent Document 1, specify the point at which the cutting speed should be changed and specify the cutting speed to be changed on the cutting program. Furthermore, a section for fixing the height position of the plasma cutting torch is designated.

JP 7-246473 A

  The arc voltage in the plasma cutting method is accompanied by an unstable change when the change in cutting speed is abrupt, and stable when the change is slow. That is, when the arc voltage is unstable, it is difficult to stably maintain the height of the plasma cutting torch from the workpiece, and when the arc voltage is stable, the height of the plasma cutting torch from the workpiece is high. It is possible to stably maintain the thickness. Therefore, it is necessary to fix the height position of the plasma cutting torch in the section where the arc voltage becomes unstable.

  Fixing the height position of the plasma cutting torch during cutting means that the possibility of the plasma cutting torch colliding with an obstacle cannot be avoided, and the torch is based on the measured value of the arc voltage as much as possible. It is preferable to perform cutting while adjusting the height. Therefore, it is not preferable to fix the height position of the plasma cutting torch over the entire section where the cutting speed is changed. And in order to reduce as much as possible the section in which the height position of the plasma cutting torch from the workpiece is fixed, it is necessary to sufficiently consider the shape of the figure to be cut.

  However, it is extremely difficult to find the section where the arc voltage will be unstable from the shape to be cut, so the work to set the section that fixes the height position of the plasma cutting torch is extremely experienced. There is a problem that it depends on the know-how of workers.

  For example, when the part to be cut is an acute corner, the cutting direction needs to be suddenly changed at the apex of the acute angle. In addition, at an acute corner portion, if the heat input to the portion increases, melting or the like may occur. For this reason, the cutting speed by the plasma cutting torch is rapidly reduced near the corner, the cutting direction is instantaneously changed at the apex, and the cutting is accelerated rapidly. In such a case, it is necessary to enter the corner and start deceleration, and at the same time, it is necessary to fix the height position of the plasma cutting torch from the workpiece. Can intervene.

  Also, if the part to be cut is an obtuse corner with a sufficiently large angle, there is little influence to change the cutting direction at the apex, and it is necessary to reduce or accelerate the cutting speed when cutting the corner. Although there is a change in the cutting speed, it is relatively gradual. In the case of such a corner, the arc voltage may remain stable while entering and leaving the corner, and the arc voltage is measured to adjust the height of the plasma cutting torch from the workpiece. It may be preferable to do so.

  Thus, it is extremely difficult for an inexperienced worker to determine whether or not to intervene in the cutting program so as to fix the height position of the plasma cutting torch corresponding to each shape to be cut. There is a problem that.

  An object of the present invention is to provide a plasma cutting method capable of fixing the height position of a plasma cutting torch when a change in cutting speed exceeds a certain reference without intervening in a cutting program, and this plasma An object of the present invention is to provide a plasma cutting apparatus for performing a cutting method.

  In order to solve the above problems, a plasma cutting method according to the present invention cuts a workpiece by moving the plasma cutting torch while injecting a plasma arc from the electrode provided on the plasma cutting torch toward the workpiece. In the plasma cutting method in which the height of the plasma cutting torch from the workpiece is adjusted by measuring the change in the arc voltage applied to the electrode, the change in the moving speed of the plasma cutting torch is measured. , When recognizing that the change in the measured moving speed of the plasma cutting torch is larger than a preset change, the height position of the plasma cutting torch is fixed, regardless of the change in the arc voltage applied to the electrode. It is characterized by cutting while holding a fixed height position.

  The plasma cutting device according to the present invention includes a plasma cutting torch for cutting a material to be cut, a lifting device for supporting the plasma cutting torch so as to be liftable, and the plasma cutting torch and the lifting device along a surface of the material to be cut. A moving carriage, a plasma power source connected to the plasma cutting torch and the material to be cut, and a plasma cutting torch attached in the vicinity of the plasma cutting torch and moving integrally with the movement of the plasma cutting torch. A speed change measuring member that measures a change in moving speed, and controls the movement of the moving carriage, measures an arc voltage applied from the plasma power source to control the lifting and lowering of the lifting device, and the speed change measuring member When the change of the moving speed of the plasma cutting torch measured in step 1 is recognized to be larger than the preset change, the lifting device is displayed. And it has a control device for controlling to hold in the state.

  In the plasma cutting method according to the present invention, when the change in the moving speed of the plasma cutting torch (hereinafter referred to as “torch”) is measured and it is recognized that the measured value is larger than a preset value, the height of the torch Because the position is fixed, no human intervention is required for the cutting program, and only the change in the torch's moving speed is noted, and the torch's height position is fixed, or the height is determined based on the measured arc voltage. Can be adjusted. For this reason, even an operator who has little experience with plasma cutting can easily and reliably perform plasma cutting.

  In the plasma cutting apparatus according to the present invention (hereinafter referred to as “cutting apparatus”), a speed change measuring member that moves integrally with the torch and measures a change in the moving speed is provided. When the cutting speed changes during the plasma cutting on the cutting material, the change in the cutting speed can be measured by the speed change measuring member.

  The change value (measured value) of the moving speed of the torch measured by the speed change measuring member is sent to the control device. Then, it is compared with a change value (set value) of the moving speed set in advance by the control device, and when the measured value becomes larger than the set value, the lifting device that lifts and lowers the torch is held in the current state. Therefore, the height position of the torch can be fixed by measuring the change in the moving speed of the torch without intervening in the cutting program.

It is a figure explaining the example of the figure which should be cut | disconnected. It is a figure explaining the example of the change of the shape and cutting speed which should be cut | disconnected. It is a figure which illustrates typically the whole structure of the cutting device concerning a present Example. It is a figure explaining the structure of the raising / lowering apparatus which supports a torch and raises / lowers. It is a figure which illustrates typically the relationship between the electrode provided in the torch, a to-be-cut material, and a power supply. It is a block diagram which shows typically the control system of a cutting device.

  Hereinafter, a preferable embodiment of the plasma cutting method according to the present invention will be described. The plasma cutting method of the present invention is a plasma cutting method in which an arc voltage applied to an electrode provided on a torch is measured so that the height of the torch from the workpiece can be adjusted. When cutting the target figure with a single stroke, when the cutting speed is changed corresponding to the shape of the figure, the change in the cutting speed is measured, and when the measured value is larger than the preset value, the torch The height position is fixed, and when the measured value is smaller than the set value, the arc voltage is measured so that the height of the torch from the workpiece can be adjusted.

  For this reason, conventionally, in order to artificially fix the height position of the torch by intervening in the cutting program at a portion where the change in cutting speed is expected to be large, in the plasma cutting method of the present invention, It is possible to fix the height position of the torch by measuring the change in the actual moving speed (cutting speed) of the torch without any human intervention for the cutting program.

  In the present invention, fixing the height position of the torch does not necessarily mean that the torch is forcibly fixed by braking means such as a brake, but driving the lifting device that supports and raises the torch. It also includes stopping and holding the torch in its current position. That is, to fix the height position of the torch means that the torch is held at the current position without performing a lifting operation.

  The moving speed of the torch means the moving speed of the torch in a plane parallel to the surface of the material to be cut, and has the same meaning as the cutting speed while cutting the material to be cut. Hereinafter, the moving speed or cutting speed of the torch means substantially the same speed.

  In the present invention, the magnitude of the change in the moving speed of the torch is not limited. That is, the moving speed of the torch changes according to the cutting conditions including the material of the material to be cut and the plate thickness. For this reason, it is not preferable to uniquely set a preset value that is preset in order to fix the height position of the torch, and it is necessary to set it appropriately in consideration of the above-mentioned conditions.

  However, if an example is given as an example, the set value is 2G. Then, using this set value as a reference, the arc voltage is measured to adjust the height of the torch when the measured value is smaller than 2G, and the height of the torch is adjusted when the measured value is smaller than 2G. If it is larger than that, it is possible to determine that the height position of the torch is fixed.

  The case where the plasma cutting method of the present invention is applied to cutting the figure C from the workpiece B made of the steel plate shown in FIG. 1 will be described. In the figure, it is assumed that the corners marked with symbols b and c in the figure C have the same angle and are cut at the same speed. Further, the material to be cut B has a constant thickness, and the cutting speeds of the straight portions other than the vicinity of the corners a to c are the same.

  As shown in FIG. 2 and FIG. 2A, the corner a has a protrusion-like shape with a vertex 52 at an acute angle. When cutting such a shape, it is necessary to change the cutting direction abruptly at the vertex 52, and it is necessary to reduce the cutting speed to approximately the same level as when the vertex 52 is stopped instantaneously. That is, when the torch reaches the point 51, it is decelerated from the normal cutting speed with respect to the material B to be stopped substantially at the vertex 52, and after passing through the vertex 52, is accelerated to the normal cutting speed until the point 53. Is done.

  In this case, the change accompanying the deceleration and acceleration of the cutting speed is abrupt, and the arc voltage is measured when, for example, the above-mentioned measurement value exceeding 2G is obtained due to the change of the cutting speed after the torch has passed the point 51. The height position of the torch is fixed regardless of the value. Then, after passing through the vertex 52 or before passing through the point 53, when the measurement value of the change in the cutting speed of the torch was smaller than 2G, the measurement was performed by releasing the fixing of the height position of the torch. The operation for adjusting the height of the torch based on the arc voltage is resumed.

  When the cutting of the workpiece B is continued with the height of the torch fixed as described above, the torch cuts the workpiece B at the same height regardless of the distance from the surface of the workpiece B. Will move on. For this reason, for example, the possibility that a part that has already been cut and deformed due to thermal strain or the like of the material to be cut cannot collide with the torch. Therefore, it is preferable to make the distance for cutting with the height position of the torch fixed as small as possible.

  As shown in FIG. 2B, the corner b has a shape in which the vertex 55 is obtuse. In such a corner b, the angle change in the cutting direction at the apex 55 of the corner b is not abrupt. For this reason, it is not necessary to reduce the cutting speed when the torch passes the apex 55, so that the change in the cutting speed during the period from the point 54 to the apex 55 is small. In this case, the measured value of the change in cutting speed while the torch passes through the point 54 and reaches the vertex 55 may be less than 2G, and similarly, the cutting is performed while the torch passes through the vertex 55 and reaches the point 56. The change in speed may be less than 2G. In such a case, while passing the point 54, the vertex 55, and the point 56 while cutting, the operation of adjusting the height of the torch based on the measured arc voltage is continued.

  As shown in FIG. 2C, the corner c has a shape in which the vertex 58 is substantially perpendicular. In such a corner c, the cutting speed changes more slowly than the corner a described above and changes more rapidly than the corner b. Therefore, after the torch has passed the point 57, if the change in the cutting speed during the period reaching the vertex 58 exceeds 2G, the cutting is continued with the height of the torch fixed, and after passing the vertex 58 When the change in cutting speed between acceleration and point 59 is less than 2G, the fixing of the height position of the torch is released and the operation for adjusting the height of the torch based on the measured arc voltage is resumed. To do.

  Next, the configuration of the cutting device according to the present invention will be described. The cutting device of the present invention is configured to be attached to a speed change measuring member that moves integrally with the torch in the vicinity of the torch and measures a change in the moving speed of the torch, and performs plasma cutting on the material to be cut. At this time, when it is recognized that the change in the moving speed of the torch measured by the speed change measuring member is larger than the preset change, the height position of the torch is fixed.

  The speed change measuring member for measuring the change in the moving speed of the torch may be any member that can measure at least a change in the moving speed in a plane parallel to the surface of the material to be cut of the torch, and the structure is limited. is not. As such a speed change measuring member, a generally used acceleration sensor can be used.

  In the cutting apparatus of the present invention, the height of the torch from the workpiece is adjusted by measuring the arc voltage and comparing the measured value with a preset voltage value. That is, when the measured value of the arc voltage is larger than the set voltage value, it is determined that the distance between the electrode and the material to be cut has increased (the height of the torch from the material to be cut has increased), and the measured value is The height of the torch from the material to be cut is adjusted by lowering the torch until it substantially matches the set voltage value.

  Then, when recognizing that the change in the moving speed of the torch measured by the speed change measuring member is larger than the preset installation value, the current position is held and fixed by fixing the height position of the torch. The cutting of the cutting material is continued.

  In the cutting apparatus configured as described above, the torch is covered with the progress of cutting in accordance with the change in the moving speed of the torch (cutting speed) without intervening in the cutting program corresponding to the figure to be cut. It is possible to determine whether to adjust the height from the cutting material, or to fix the torch height position (without adjusting the height from the material to be cut) and continue cutting. It is possible to proceed with cutting based on the determination.

  Hereinafter, the configuration of the cutting apparatus according to the present embodiment will be described with reference to FIGS.

  The cutting device A includes a torch 1 that cuts the workpiece B, a lifting device 10 that supports the torch 1 so that the torch 1 can be lifted, and a movable carriage 20 that moves the torch 1 and the lifting device 10 along the surface of the workpiece B. And a plasma power source 5 connected to the torch 1 and the material B to be cut, and a speed change that is attached in the vicinity of the torch 1 and moves together with the movement of the torch 1 to measure a change in the moving speed of the torch 1 The numerical control (NC) device 30 that controls the movement of the measuring member 8, the movable carriage 20 and the operation of the plasma power source 5, and the elevation voltage of the lifting device 10 is measured by measuring the arc voltage applied from the plasma power source 5. A torch height control that controls and controls the lifting device 10 to be held in the current state when recognizing that the change in the moving speed of the torch 1 measured by the speed change measuring member 8 is larger than a preset change. Is configured to include a device 31, the.

  As the torch 1, a commercially available structure is used. As schematically shown in FIG. 5, the torch 1 has an electrode 2 and a nozzle 3, the electrode 2 and the negative pole of the plasma power source 5 are connected by a cap tire 5b, and the nozzle 3 is connected via a changeover switch 5a. The positive electrode of the plasma power source 5 is connected to the cap tire 5c. Further, the material to be cut B is connected to the positive pole of the plasma power source 5 by the cap tire 5d through the changeover switch 5a.

  A plasma gas supply device (not shown) is connected to the torch 1, and a plasma gas (oxygen gas, nitrogen gas, mixed gas of oxygen gas and nitrogen gas, gas such as air) having a preset flow rate from the supply device. Is supplied. Further, a hose for supplying cooling water and a hose for discharging cooling water (not shown) are connected to the torch 1.

  Then, a plasma gas is supplied around the electrode 2 of the torch 1 and discharged between the electrode 2 and the nozzle 3, thereby forming a pilot arc and injecting it toward the material B to be cut. It is possible to cut the workpiece B by moving the torch 1 in this state by forming a main arc (plasma arc) by discharging with the cutting material B and stopping the discharge between the electrode 2 and the nozzle 3. It is.

  The plasma power source 5 is controlled at a constant current. The current value is not uniquely set, but is appropriately set according to conditions such as the specifications of the torch 1 and the material and thickness of the material B to be cut. Therefore, when the distance between the electrode 2 and the material to be cut B changes, the arc voltage changes according to this change. That is, the arc voltage changes according to the change in the height H from the workpiece B of the torch 1. Moreover, the value of the height H from the to-be-cut material B of the torch 1 is substantially constant (about 3 mm-about 5 mm), and does not change a lot.

  For this reason, the arc voltage value (setting voltage value, for example, 200V) when the torch 1 is set to the height H from the workpiece B is set in advance, and the arc voltage is measured during cutting to obtain the measured value. When a difference occurs between the set voltage value and the measured voltage, the torch 1 is moved up and down so that the measured value substantially matches the set voltage value, thereby adjusting the height of the torch 1 from the workpiece B. It is possible.

  In particular, the plasma power source 5 is provided with a voltage measuring unit 5e for measuring the arc voltage between the electrode 2 and the material to be cut B, and the arc voltage applied while cutting the material to be cut B is performed. The measured value can be transmitted to the torch height control device 31.

  The torch 1 is supported by the lifting device 10 and configured to be movable up and down, and is configured to be movable in a desired direction with respect to the workpiece B by the movable carriage 20.

  In this embodiment, the movable carriage 20 has a portal frame 22 that runs along a pair of rails 21. The frame 22 includes a saddle 22a that is placed on the rail 21 so as to be able to travel, and a cross garter 22b that is disposed in a direction orthogonal to the laying direction of the rail 21. A traverse carriage 23 traversing the cross garter 22b is mounted on the cross garter 22b, and the lifting device 10 is provided on the traverse carriage 23.

  A traveling motor 24 is disposed on the saddle 22a, and the traveling frame 22 can travel along the rail 21 at a desired speed by controlling the rotation of the traveling motor 24 according to a command from an NC device 30 described later. It is configured. A traverse motor 25 is disposed on the traverse carriage 23, and the traverse carriage 23 is configured to traverse at a desired speed by controlling the rotation of the traverse motor 25 according to a command from the NC device 30. . Therefore, by controlling the motors 24 and 25 in association with each other, the torch 1 can be moved two-dimensionally in a desired direction.

  The lifting device 10 is provided on the transverse carriage 23. That is, the traverse carriage 23 is provided with an elevating motor 11 and, for example, a ball screw (not shown) driven by the elevating motor 11, and is also driven by the elevating guide 12 in the vertical direction while being driven by the ball screw. A lifting bracket 13 is provided. The lift motor 11 has a built-in encoder, and a positive or negative pulse signal is generated with rotation, and the number of generated pulses is added to or subtracted from the current value so that the lift bracket 13 moves in the lift direction. It is configured to be able to grasp the current position. Further, a torch holder 14 is integrally provided on the lifting bracket 13, and the torch 1 is supported by the torch holder 14.

  An acceleration sensor 8 constituting a speed change measuring member and a torch height control device 31 are attached to a predetermined position (in this embodiment, the lifting guide 12) of the transverse carriage 23. Therefore, the acceleration sensor 8 is configured to move integrally with the torch 1.

  The acceleration sensor 8 is configured to be able to generate a signal corresponding to the measured G by measuring the G corresponding to the change in the moving speed in the plane. And while cutting with respect to the to-be-cut | disconnected material B, the change of the moving speed of the raising / lowering guide 12 which moves integrally with the torch 1 always in the plane parallel to the to-be-cut | disconnected material B (change of the moving speed of the torch 1) ) And the measured value can be transmitted to the torch height control device 31.

  In the present embodiment, an acceleration sensor that can measure the change in the moving speed of the torch 1 in a range of about ± 3G to ± 4G is used. Such an acceleration sensor is generally commercially available.

  An operation panel 26 is placed on a saddle 22 a constituting the traveling frame 22. The operation panel 26 controls the rotation of the motors 24 and 25 and the operation control of the torch 1 including the plasma power source 5 and moves the torch 1 to the ascending limit with respect to the lifting device 10 that moves the torch 1 up and down. An NC device 30 for giving commands is incorporated. Reference numeral 26a denotes an input unit such as a keyboard, and reference numeral 26b denotes a display.

  In addition, the power supply device 5 is installed in the vicinity of the traveling carriage 20, and as described above, the power supply device 5 and the torch 1, and the power supply device 5 and the material B to be cut are connected via a cap tire (not shown). Has been. Similarly, the power supply device 5, the NC device 30, and the torch height control device 31 are also connected via a communication line or an aerial line (not shown).

  Next, the control system of the cutting apparatus A according to the present embodiment will be described with reference to FIG.

  In the storage unit provided in the NC device 30, for example, a program for performing an operation for recognizing the posture of the material B to be cut, a program for performing a piercing operation, and a basic figure, which are operations necessary for performing plasma cutting. And a program such as a cutting program for instructing an operation sequence from the start to the end of cutting.

  Further, in the temporary storage unit provided in the NC device 30, information such as a dimension set for each figure to be cut from the material to be cut B input from the input device 26 a, a cutting speed, a change point for changing the cutting speed, and the like. Remembered.

  In addition, the calculation unit provided in the NC device 30 reads the program stored in the storage unit and the temporary storage unit during the period from the start to the end of the cutting operation on the workpiece B, and the plasma power source 5 The operations of the lifting device 10 and the movable carriage 20 are controlled.

  In the storage unit provided in the torch height control device 31, information on a set voltage value (for example, 200 V) serving as a reference for the arc voltage when adjusting the height H from the workpiece B of the torch 1, and the torch 1 The information of the set value (for example, 2G) used as the reference | standard of the change of the speed at the time of fixing the height position of is stored. Further, the temporary storage unit includes changes in the measured value of the arc voltage transmitted from the voltage measuring unit 5e provided in the plasma power source 5 and the movement speed of the torch 1 transmitted from the acceleration sensor 8 provided in the vicinity of the torch 1. Measurement values are temporarily stored.

  In the torch height control device 31, the arc voltage measurement value transmitted from the voltage measurement unit 5 e of the plasma power source 5 and the acceleration sensor 8 are transmitted while the torch 1 is cutting the workpiece B with the torch 1. The measured value of the change in the moving speed of the torch 1 is compared with the set voltage value and the set value stored in the storage unit in advance, and the drive of the lifting motor 11 of the lifting device 10 is controlled according to the comparison result.

  Next, a procedure for cutting the workpiece B by the cutting apparatus A configured as described above will be briefly described.

  First, information on a figure to be cut from the input device 26a of the operation panel 26 to the material to be cut B, information on a cutting speed corresponding to the material and thickness of the material to be cut B, and other necessary information are NC. Input to device 30 and store. Thereafter, when cutting is started, the posture of the material to be cut B is confirmed in accordance with a program stored in advance, and coordinate conversion is performed so that cutting work can be performed in accordance with this posture. Thereafter, a command to be raised to the ascending limit is given to the lifting motor 11 of the lifting device 10, and the torch 1 is set at a sufficiently high position from the surface of the workpiece B. Further, the motors 24 and 25 are driven so as to move the torch 1 to the piercing point P set in the figure C to be cut.

  After the torch 1 reaches the piercing point P, when a cutting operation start signal is input to the NC device 30 to start the operation, the plasma power source 5 starts to be driven according to a preset program and the torch 1 is lowered. Then, piercing is performed, and a series of cuts are performed on the figure C from the piercing point P as a starting point.

  While cutting the workpiece B with the torch 1, the voltage measuring unit 5 e of the plasma power source 5 measures the arc voltage and transmits the measured value to the torch height control device 31, and the acceleration sensor 8 detects the torch 1. The change in the moving speed is measured and the measured value is transmitted to the torch height control device 31. In the torch height control device 31, the measured value of the transmitted arc voltage is compared with a set voltage value (for example, 200 V) with respect to the arc voltage stored in the storage unit in advance, and the change in the movement speed of the transmitted torch 1 is changed. The measured value is compared with a set value (for example, 2G) of change in moving speed stored in advance in the storage unit.

  And when it determines with the measured value from the acceleration sensor 8 being smaller than the setting value of the change of the moving speed of the torch 1, and as a result of comparing with the measured value from the voltage measurement part 5e, and a setting voltage value, both are substantially one. If it is determined that it is done, the cutting is continued in a state where the height of the torch 1 from the workpiece B is maintained without driving the lifting motor 11 of the lifting device 10.

  Further, when it is determined that the measured value from the acceleration sensor 8 is smaller than the set value of the change in the moving speed of the torch 1, both the measured value from the voltage measuring unit 5 e and the set voltage value are compared. If it is determined that they do not match, the lifting motor 11 of the lifting device 10 is driven to raise or lower the torch 1 so as to eliminate the difference between the measured value and the set voltage value. At the point of time, the driving of the lifting motor 11 is stopped.

  As described above, when the change in the moving speed of the torch 1 is smaller than 2G, for example, the height H of the torch 1 from the workpiece B is made substantially constant based on the measured value of the arc voltage. It is possible to continue cutting.

  Further, when it is determined that the measured value from the acceleration sensor 8 is larger than the set value of the change in the moving speed of the torch 1, the torch height control device 31 does not issue a rotation drive signal to the lifting motor 11 of the lifting device 10. , Keep the current state. At this time, the measured value of the arc voltage is continuously transmitted to the torch height control device 31 from the voltage measuring unit 5e provided in the plasma power source 5. However, the lifting motor is controlled regardless of the transmitted measured value. No rotation drive signal for 11 is issued.

  Therefore, the torch 1 is fixed at the height position when the measured value of the change in the moving speed exceeds 2G by the acceleration sensor 8, and the cutting is continued while maintaining this height position. While cutting is continued as described above, the change in the moving speed of the torch 1 by the acceleration sensor 8 is continuously measured, and the measured value is transmitted to the torch height control device 31. When the torch height control device 31 determines that the change in the moving speed of the torch 1 is small and the measured value by the acceleration sensor 8 is smaller than 2G, the fixing of the height position of the torch 1 is released. As described above, the adjustment of the height of the torch 1 from the workpiece B based on the measurement value transmitted from the voltage measurement unit 5e provided in the plasma power source 5 is resumed.

  By measuring the arc voltage and measuring the change in the moving speed of the torch 1 as described above, the height of the torch 1 with respect to the workpiece B can be adjusted and adjusted without intervention of the cutting program. The target figure C can be cut while the position is fixed.

  The plasma cutting method according to the present invention can be used in a plasma cutting apparatus configured to adjust the height of the torch from the workpiece based on the arc voltage.

A cutting device B material to be cut C figure H height P piercing point a to c corner 1 torch 2 electrode 3 nozzle 5 plasma power source 5a changeover switch 5b to 5d cabtyre 5e voltage measuring unit 8 speed change measuring member, acceleration sensor 10 lifting device DESCRIPTION OF SYMBOLS 11 Lifting motor 12 Lifting guide 13 Lifting bracket 14 Torch holder 20 Moving carriage 21 Rail 22 Frame 22a Saddle 22b Cross garter 23 Traverse carriage 24 Traveling motor 25 Traverse motor 26 Operation panel 26a Input device 26b Display 30 NC device 31 Torch height control device 51-59 points

Claims (2)

  Plasma is measured by measuring changes in the arc voltage applied to the electrodes when cutting the workpiece by moving the plasma cutting torch while injecting a plasma arc from the electrode provided on the plasma cutting torch toward the workpiece. In the plasma cutting method in which the height of the cutting torch from the workpiece is adjusted, the change in the moving speed of the plasma cutting torch is measured, and the change in the moving speed of the measured plasma cutting torch is preset. When the height of the plasma cutting torch is recognized, the height position of the plasma cutting torch is fixed and the fixed height position is cut regardless of the change in the arc voltage applied to the electrode. Plasma cutting method.   A plasma cutting torch for cutting a material to be cut, a lifting device for supporting the plasma cutting torch so as to be lifted, a moving carriage for moving the plasma cutting torch and the lifting device along a surface of the material to be cut, and the plasma cutting A plasma power source connected to the torch and the material to be cut, and a speed change measurement which is attached in the vicinity of the plasma cutting torch and moves integrally with the movement of the plasma cutting torch to measure a change in the moving speed of the plasma cutting torch. And the movement of the moving carriage, the arc voltage applied from the plasma power source is measured to control the lifting and lowering of the lifting device, and the moving speed of the plasma cutting torch measured by the speed change measuring member is measured. Control for controlling the lifting device to be held in the current state when recognizing that the change is larger than a preset change Plasma cutting apparatus comprising: the location, the.

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