JP3850172B2 - Plasma processing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a plasma processing method for processing a small hole having a predetermined diameter in a workpiece by a plasma arc.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, a plasma torch including an electrode and a nozzle that covers a tip end side (processing workpiece side) of the electrode via a working gas passage is used in a plasma processing apparatus. A small-diameter nozzle hole is formed at the tip of the plasma torch, and a pilot arc formed between the nozzle and the electrode reaches the workpiece by working gas ejected from the nozzle hole through the working gas passage. Then, a strong main arc (hereinafter referred to as a plasma arc) is formed between the electrode and the workpiece by way of the nozzle hole.
[0003]
In such a cutting method that forms a hole in a workpiece using a plasma arc, the cutting width is larger than a hole cutting method that uses a laser, so that the diameter is about twice or more the thickness of a normal workpiece. The hole having a diameter smaller than that (hereinafter referred to as a small hole) is formed by a drill as a post-process after the end of the cutting process using the plasma arc. In this way, when drilling is performed using a drill in a separate process, a hole having a predetermined diameter cannot be processed by one drilling, and the process is performed in several times.
[0004]
When cutting a hole having a diameter of about twice or more the workpiece thickness using the plasma arc, piercing is first performed at the internal position of the cut shape, and the cut shape is drawn so as to draw a straight line or an arc. Proceeding to the arc path, machining is performed.
[0005]
[Problems to be solved by the invention]
However, as described above, in the cutting method in which the cutting process of a shape other than the small holes is performed using the plasma arc and the small holes are formed by drill drilling in another process, a separate process is required when processing a product having many small holes. Therefore, there is an increasing demand for cutting a small hole using a plasma arc. In addition, when the method for cutting a hole having a diameter of about twice or more the workpiece thickness as described above is applied to the cutting of a small hole, the small hole formed by the processing is not clear or chipped. There is a problem that the size is large and the shape is bad.
[0006]
The present invention has been made to solve such problems, and it is easy to cut a small hole having a predetermined diameter (for example, a diameter of about 2 times or less of the workpiece thickness) using a plasma arc. It is an object of the present invention to provide a plasma processing method that can be carried out.
[0007]
[Means for solving the problems and actions / effects]
In order to achieve the above-described object, the plasma processing method according to the first invention is a plasma processing method for processing a small hole having a predetermined diameter in a workpiece by a plasma arc,
(A) A plasma torch that forms a plasma arc between the workpiece and the workpiece can be moved relative to the center position of the small hole formed in the workpiece and the plasma torch can be ignited on the workpiece. A first step of relative positioning to a first set height,
(B) After the positioning of the plasma torch, a plasma arc is formed between the workpiece and the workpiece, and the height of the plasma torch is maintained while holding the plasma arc. A second step of relative movement to the same second set height;
And (c) a third step of holding the plasma arc in a state where the plasma torch is stopped at the second set height until it is detected that machining of a small hole having a predetermined diameter is detected. Is.
[0008]
In the first invention, the plasma torch is moved relative to the center of the small hole of the workpiece, and the plasma torch is moved relative to the workpiece so that the plasma arc can be ignited (first set height). . Next, a plasma arc is ignited between the plasma torch and the workpiece, and the height of the plasma torch is maintained while maintaining the plasma arc. Second setting is such that the plasma arc diameter near the workpiece is substantially the same as the small hole diameter. The plasma torch is stopped in a state where the plasma arc is held at the second set height by relative movement to the height. In this way, a small hole having a predetermined diameter is formed in the workpiece.
[0009]
According to the first aspect of the present invention, a plasma arc is used even when a small hole having a diameter (less than twice the plate thickness of a workpiece to be machined) that has been impossible with the conventional plasma cutting method is machined into a workpiece. Thus, there is an effect that it can be easily and reliably formed. In addition, the small holes formed in this way have a preset diameter, and are almost free of chipping or chipping and have a stable shape. Therefore, even when a product having small holes is processed, cutting processing using a plasma arc can be performed, and labor in another process can be reduced. Thus, the small hole formed using the plasma arc can be used as a product as it is or as a pilot hole of a drill.
[0010]
Next, a plasma processing method according to the second invention is a plasma processing method for processing a small hole having a predetermined diameter in a workpiece by a plasma arc,
(A) A plasma torch that forms a plasma arc between the workpiece and the workpiece can be moved relative to the center position of the small hole formed in the workpiece and the plasma torch can be ignited on the workpiece. A first step of relative positioning to a first set height,
(B) After the positioning of the plasma torch, a plasma arc is formed between the workpiece and the workpiece, and the height of the plasma torch is maintained while holding the plasma arc. A second step of relative movement to the same second set height;
(C) Thereafter, a third step of holding the plasma arc in a state where the plasma torch is stopped at the second set height until completion of machining of a small hole having a predetermined diameter is detected, and (d) the small hole And a fourth step of starting cutting by moving the plasma torch relative to a predetermined height at which the workpiece can be cut after the machining is finished.
[0011]
In the second invention, after forming a small hole of a predetermined diameter, which has been impossible in the conventional machining, in the same manner as in the first invention, the plasma torch is moved to the cutting height of the workpiece, The workpiece is cut by moving the plasma torch relative to the cutting shape. Thus, in addition to the effect of the first invention, there is an effect that it is possible to smoothly perform the processing of small holes and the cutting processing of the outer periphery and the like, which were impossible in the past, in the same process. In addition, after forming the small hole of the predetermined diameter, the plasma torch is moved to a cuttable height of the workpiece while the plasma arc is formed, and the plasma torch is moved relative to the cutting shape. You may make it cut | disconnect a workpiece | work continuously.
[0012]
In the first and second inventions, a time from when the plasma torch is stopped at the second set height to when a small hole is formed is set in advance, and the time when the set time elapses is set as the small time. It is preferable to detect the completion of hole processing. By doing so, there is an effect that the small hole can be cut by simple control.
[0013]
In the first and second inventions, the second set height is preferably set in advance by a small hole diameter formed in the workpiece and a nozzle hole diameter attached to the tip of the plasma torch. By doing so, there is an effect that the diameter of the small hole formed in the workpiece can be adjusted with simple control.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Next, specific embodiments of the plasma processing method according to the present invention will be described with reference to the drawings.
[0015]
FIG. 1 is a system configuration diagram of a plasma processing apparatus for performing a plasma processing method according to an embodiment of the present invention, and FIG. 2 is a schematic cross-sectional view illustrating a plasma torch of the present embodiment.
[0016]
In the plasma processing apparatus 1 of the present embodiment, a workpiece 3 to be cut is disposed at the tip of a multi-cylindrical plasma torch 2, and a substantially cylindrical electrode disposed at a substantially central position of the plasma torch 2. 4 (see FIG. 2) is connected to a negative terminal of a plasma arc power supply unit 5 for supplying a plasma current, and a positive terminal of the plasma arc power supply unit 5 is connected to the workpiece 3. A plus terminal of the plasma arc power supply unit 5 is connected to a nozzle 6 (see FIG. 2) of the plasma torch 2 described later via a switch 7.
[0017]
The plasma torch 2 is provided with a nozzle 6 having a substantially cylindrical shape covering the outer peripheral side of the electrode 4 and having a nozzle orifice 8 having a small diameter on the surface (tip surface) facing the workpiece 3. A working gas passage 9 is formed between the nozzle 6 and the nozzle 6. A cylindrical first nozzle cap 11 is disposed on the outer peripheral side of the nozzle 6 via a cooling water passage 10, and a second nozzle cap is provided on the outer peripheral side of the first nozzle cap 11 via a secondary gas passage 12. 13 is arranged.
[0018]
The tip of the first nozzle cap 11 is in close contact with the outer peripheral side of the substantially tip of the nozzle 6, and the tip of the nozzle 6 is in the tip opening of the second nozzle cap 13. And a shield cap 15 having a spout 14 for ejecting the secondary gas passing through the secondary gas passage 12 is mounted. Annular working gas swirler 16 and secondary gas swirler 17 are fitted in the working gas passage 9 and the secondary gas passage 12, respectively.
[0019]
Further, the working gas passage 9 and the secondary gas passage 12 are respectively supplied with working gas and secondary gas from a working gas supply system (not shown) from the base end side of the nozzle 6 and pass through the working gas passage 9. When the working gas passes through the working gas swirler 16, the working gas becomes a swirling flow, and is ejected to the workpiece 3 through the nozzle orifice 8, and the secondary gas passing through the secondary gas passage 22 is also the second swirler 17. When it passes through, it becomes a whirling flow and is ejected from the said jet nozzle 14.
[0020]
A heat-resistant insert 18 made of a high-melting-point material (for example, made of hafnium, zirconium, alloy, etc.) that can withstand the high heat of the plasma arc A is attached to the tip of the electrode 4 where the plasma arc occurs. A cooling water passage (not shown) for passing cooling water is provided inside the electrode 4.
[0021]
When the plasma arc A is ignited between the electrode 4 and the workpiece 3, first, the switch 7 is turned on, and a pilot arc is ignited between the electrode 4 and the nozzle 6. A conductive working gas supplied to the working gas passage 9 reaches the workpiece 3 through the nozzle orifice 8 and becomes a plasma arc A. In addition, the plasma arc A is surrounded by a secondary swirling air flow ejected through the secondary gas passage 12. The pilot arc is extinguished after the ignition of the plasma arc A by turning off the switch 7.
[0022]
The plasma arc A is a plasma arc having a high temperature and a high density energy due to the effective restraint by the nozzle orifice 8 and the thermal pinch action by the working gas stream. As shown in the side view of FIG. 3, the plasma arc A has a characteristic that its diameter increases as the distance from the nozzle orifice 8 increases.
[0023]
FIG. 4 shows a case where the workpiece thickness is 6 mm, the nozzle orifice hole diameter is 1.1 mm, and the plasma arc current value is 120 A (A), and the workpiece workpiece thickness is 3.2 mm, the nozzle orifice hole diameter is 0.8 mm, and the plasma arc current value is 120 A. A relationship diagram between the amount of rise from the plasma arc ignition position (first set height H ₁ ) of the plasma torch 2 in the case (b) and the diameter of the hole formed in the workpiece is shown. The first set height H ₁ is a position where the plasma arc can be stably ignited. In the case of (A), the first set height H ₁ is 6 mm, and in the case of (B), the first setting the height _{H 1} is 5mm are preferable.
[0024]
If the plasma torch 2 is raised from the position where the plasma arc A is ignited as shown in the drawing, the hole diameter formed in the workpiece 3 can be increased, and the workpiece 3 can be adjusted by adjusting the amount of the rise. It is clear that the diameter of the hole formed can be controlled. Therefore, a hole having an arbitrary diameter can be formed in the workpiece 3 using the hole diameter of the nozzle orifice 8 and the height position of the plasma torch 2 as parameters.
[0025]
The plasma torch 2 configured in this way is supported by the drive device 20 so as to be movable in a three-dimensional direction with respect to the workpiece 3, and the height position of the plasma torch 2 with respect to the workpiece 3 is adjusted by the drive device 20. Cutting is performed by adjusting and moving along the cutting shape.
[0026]
In the present embodiment, the drive device 20, the plasma arc power supply unit 5 and the working gas supply system are each connected to a processing control device 21 and their operations are controlled. The machining control device 21 is connected to a storage unit 22 having a cutting condition database corresponding to various workpieces and a hole machining database corresponding to the hole diameter of the nozzle orifice 8 attached to the plasma torch 2. The cutting shape for each workpiece 3 is input.
[0027]
As the cutting condition database, the cutting set height, cutting speed, first setting height H ₁ (the height at which plasma arc A can be ignited), and current value of the plasma torch 2 according to the thickness and material of the workpiece 3 , Correction amount and working gas pressure are set respectively.
[0028]
Examples hole processing database, and the amount of increase in the pore diameter of the nozzle orifice 8 that is mounted in the hole diameter and the plasma torch 2 cut shape from the first set the height H ₁ of the plasma torch 2 to a parameter, the plasma torch 2 and a rising speed increasing the rise amount from the first set height H _1, the plasma torch 2 in a position raised the increase amount from the first set height H ₁ (second set height H ₂₎ A stop time (a time until the drilling is completed) to be stopped is set.
[0029]
Next, a procedure for performing plasma cutting using the processing control device 21 will be described with reference to the flowchart shown in FIG.
[0030]
S1: When the machining control device 20 receives a machining start command, the cutting shape of the machining workpiece 3 is a hole (hereinafter referred to as a small hole) having a cutting shape of the machining workpiece 3 that is twice or less than the workpiece thickness. It is determined whether or not there is.
S2: When the cut shape is a small hole, the plasma torch 2 is moved to the center position of the small hole formed in the workpiece. On the other hand, if the cut shape is other than a small hole, the processes in and after step 9 described later are performed.
S3: Then, the cutting condition data and hole processing data corresponding to the workpiece 3 from the storage unit 22 is read, to move the plasma torch 2 to the first set height H _1.
S4: the at the center of the small hole, and to ignite the plasma arc A between the first set height H ₁ electrode 4 workpiece 3 is positioned plasma torch 2.
S5: While holding the plasma arc A, the plasma torch 2 is raised by the rising amount corresponding to the hole diameter of the nozzle orifice 8 and the small hole diameter formed at the rising speed set in the hole processing database, and the second set is disposed at a height H _2.
S6～S7: the plasma torch 2 is stopped second set to the height H _2, the hole small hole processing completed when the stop time has elapsed set by the processing data is detected, it terminates the small hole processing.
S8: Next, it is detected whether or not all the cutting operations of the cutting shape input to the processing control device 21 have been completed for the workpiece 3. If completed, the processing is terminated and other cutting shapes are processed. In this case, the operations after step S1 are repeated.
[0031]
S9～S10: If operated in the cutting shape of the aforementioned step S2 is not the small holes, is moved to a piercing position being entered with pre-cut shape of the plasma torch 2 is moved to the first set height H ₁ Position.
S11: Subsequently, a plasma arc A is ignited between the electrode 4 and the workpiece 3 of the plasma torch 2.
S12 to S13: After the completion of the piercing, the plasma torch 2 is moved to the set cutting height, and the workpiece is cut by moving the plasma torch 2 at the cutting speed along the cutting shape.
S14: Next, when the cutting of the cutting shape is completed, the process proceeds to step S8.
[0032]
According to this embodiment, it is easy to adjust the height of the plasma torch 2 with respect to the workpiece 3 by adjusting the height of the plasma torch 2 with respect to the workpiece 3 which has been impossible with the conventional plasma cutting method (less than twice the thickness of the workpiece). And can be processed reliably. It was confirmed that the small holes formed in this way had a preset diameter, were free from chipping or chipping, and had a stable shape. Thus, the small hole formed using the plasma arc can be used as a product as it is or as a pilot hole of a drill.
[0033]
In addition, according to the present embodiment, since the small hole can be cut smoothly in the same process as the plasma cutting process of a shape other than the small hole, the labor of drilling or the like in a separate process that has been conventionally required is eliminated. There is an effect that it can be reduced.
[0034]
In the present embodiment, the amount of increase in the plasma torch 2, the pore diameter of the pore size of the cut shape in the hole machining database and the nozzle orifice 8 parameters and the increase amount of the plasma torch 2 from the first set height H ₁ The rising speed to be raised and the stop time for stopping the plasma torch 2 at the second set height H ₂ are set, but not limited thereto, the rising amount, the rising speed and the stop time are not limited to the workpiece 3. It is also possible for the operator to arbitrarily set according to the plate thickness, material, cutting shape and the like.
[Brief description of the drawings]
FIG. 1 is a system configuration diagram of a plasma processing apparatus performed by a plasma processing method according to an embodiment of the present invention.
FIG. 2 is a schematic cross-sectional view illustrating a plasma torch according to the present embodiment.
FIG. 3 is a side view of a plasma arc.
FIG. 4 is a diagram showing the relationship between the amount of rise of the plasma torch from the first set height and the diameter of the hole formed in the workpiece, according to the present embodiment.
FIG. 5 is a flowchart for explaining a procedure for performing plasma cutting processing using the processing control apparatus of the present embodiment;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Plasma processing apparatus 2 Plasma torch 3 Workpiece | work 4 Electrode 5 Plasma arc power supply unit 6 Nozzle 7 Switch 8 Nozzle orifice 9 Working gas path 10 Cooling water path 11 1st nozzle cap 12 Secondary gas path 13 2nd nozzle cap 14 Jet outlet 15 Shield Cap 16 Working Gas Swirler 17 Secondary Gas Swirler 18 Heat Resistant Insert 20 Drive Device 21 Processing Control Device 22 Storage Unit

Claims (4)

A plasma processing method for processing a small hole having a predetermined diameter in a workpiece by plasma arc,
(A) A plasma torch that forms a plasma arc with the workpiece can be moved relative to the center position of a small hole formed in the workpiece, and the plasma arc can be ignited on the workpiece. A first step of relative positioning to a first set height,
(B) After positioning the plasma torch, a plasma arc is formed between the workpiece and the workpiece, and the height of the plasma torch is maintained while maintaining the plasma arc. A second step of relative movement to the same second set height;
(C) Thereafter, a third step of holding the plasma arc in a state where the plasma torch is stopped at the second set height until completion of machining of a small hole having a predetermined diameter is detected. Plasma processing method. A plasma processing method for processing a small hole having a predetermined diameter in a workpiece by plasma arc,
(A) A plasma torch that forms a plasma arc with the workpiece can be moved relative to the center position of a small hole formed in the workpiece, and the plasma arc can be ignited on the workpiece. A first step of relative positioning to a first set height,
(B) After positioning the plasma torch, a plasma arc is formed between the workpiece and the workpiece, and the height of the plasma torch is maintained while maintaining the plasma arc. A second step of relative movement to the same second set height;
(C) a third step of holding the plasma arc in a state in which the plasma torch is stopped at the second set height until it is detected that a small hole having a predetermined diameter has been processed;
(D) A plasma processing method comprising: a fourth step of starting cutting by moving the plasma torch relative to a predetermined height at which the workpiece can be cut after the small hole processing is completed. A time from when the plasma torch is stopped at the second set height to when a small hole is formed is set in advance, and the time when the set time has elapsed is detected as the completion of the processing of the small hole. 3. The plasma processing method according to 1 or 2. The plasma processing method according to any one of claims 1 to 3, wherein the second set height is preset based on a small hole diameter formed in a workpiece and a nozzle hole diameter attached to a tip of the plasma torch.

Images