JP6495955B2 - Laser cutting processing method, nozzle and laser processing apparatus - Google Patents

Description

  The present invention relates to a laser cutting method for a metal workpiece such as carbon steel, a nozzle used in the processing method, and a laser processing apparatus. More specifically, a laser cutting method and a nozzle capable of efficiently injecting (entering) the assist gas into the cutting groove during laser cutting and effectively discharging dross from the cutting groove. The present invention relates to a laser processing apparatus.

  Conventionally, when performing laser cutting of a metal workpiece, an assist gas is injected to the laser cutting position, and dross generated during the laser cutting is discharged from the cutting groove. By the way, when the workpiece is a thick plate such as mild steel, oxygen gas is used as an assist gas. In this case, the workpiece is cut using the heat of oxidation reaction of iron, and laser cutting of a thick workpiece can be efficiently performed.

  By the way, when the diameter of the nozzle opening of the nozzle provided in the laser processing head in the laser processing apparatus is large, a large amount of assist gas can enter the cutting groove formed by the laser cutting processing. And the dross produced in the cutting groove can be efficiently discharged by the intruding assist gas.

  However, the assist gas ejected from the portion corresponding to the outside in the width direction of the cutting groove at the nozzle opening spreads along the workpiece surface without entering the cutting groove. In addition, the assist gas spreads not only in the region immediately under the processing point in the cutting groove (processing region) but also in the region behind the processing point in the cutting groove (which has already been cut and preheated). Therefore, an oxidation reaction occurs at the edge of the cutting groove and the rear region in the cutting groove, and burning is likely to occur.

  When the nozzle opening has a small diameter, the amount of assist gas that spreads along the surface of the workpiece is small, and the occurrence of burning can be suppressed. However, the amount of assist gas entering the cutting groove is reduced, making it difficult to discharge dross. Therefore, dross easily adheres to the back surface of the workpiece.

  Incidentally, nitrogen gas may be used as the assist gas. In this case, although the occurrence of burning can be suppressed, if the nozzle opening is large, the consumption amount of the assist gas increases. And when a nozzle opening is small, discharge | emission of the dross from a cutting groove becomes difficult.

  Therefore, the present invention seeks to solve the problems as described above by adopting a double structure having an inner nozzle and an outer nozzle as the nozzle configuration. There is Patent Document 1 as a prior example similar to the configuration of the present invention.

JP-A-63-171290

  The configuration of the nozzle described in Patent Document 1 is configured in a double manner by including a conical sleeve surrounding the outer periphery of the conical inner nozzle. However, the outer peripheral surface of the inner nozzle and the inner peripheral surface of the sleeve are in close contact. The outer peripheral surface of the inner nozzle or the inner peripheral surface of the sleeve is provided with a plurality of vertical grooves. The inner nozzle and the longitudinal groove communicate with each other through a passage formed in the inner nozzle. Therefore, the same assist gas is ejected from the inner nozzle and the vertical groove.

  Incidentally, in the configuration described in Patent Document 1 as described above, the assist gas is ejected from the plurality of longitudinal groove portions, and therefore the flow path resistance increases. Further, since the negative pressure is not generated between the plurality of longitudinal grooves without ejecting the assist gas, the assist gas ejected from the inner nozzle tends to spread radially outward from a portion between the end portions of the longitudinal grooves. It is in. Therefore, it is difficult for the assist gas ejected from the nozzle to effectively enter the cutting groove. Therefore, when oxygen gas is used as the assist gas, it is difficult to suppress dross generation or burning.

The present invention was made in view of the conventional problems as described above, and is a laser cutting method for a metal workpiece, in which the tip surface of the inner nozzle is formed into a flat surface, and the tip surface of the inner nozzle is The same assist gas is ejected from the inner nozzle and the outer nozzle of the double structure provided on the same plane or the inner side of the tip surface of the outer nozzle, and a negative pressure is generated at a portion corresponding to the tip surface of the inner nozzle. The throttle portion formed by drawing the assist gas ejected in a conical shape from the outer nozzle toward the inside imparts a throttling action to the cylindrical assist gas ejected from the inner nozzle, and restricts it to a position away from the nozzle tip. A portion is formed, and this narrowed portion is matched with the surface of the workpiece to perform laser cutting.

  Further, in the laser cutting processing method, the periphery of the inner assist gas ejected from the inner nozzle is surrounded by the outer assist gas ejected from the outer nozzle, and the outer assist gas is cut at the end of the cut surface in the cutting surface by the laser cutting processing. The laser cutting process is performed by supplying to the part.

  In the laser cutting method, the assist gas is oxygen gas.

Further, an inner peripheral surface of the outer nozzle, which is a nozzle in the laser processing apparatus, includes an outer nozzle on the outer side of the tapered inner nozzle having a tapered hole whose tip side gradually becomes smaller in diameter, and surrounds the inner nozzle. The annular taper hole between the inner nozzle and the outer peripheral surface of the inner nozzle is formed as a continuous gap over the entire circumference, and the front end surface of the inner nozzle is negative at a position corresponding to the front end surface. A throttle portion that generates pressure and draws the assist gas ejected from the annular tapered hole inward is formed on a plane that is formed at a position away from the nozzle tip , and the tip surface of the outer nozzle Located on the same plane or inside.

  In the nozzle, the tapered hole of the inner nozzle and the tapered gap between the inner nozzle and the outer nozzle form the same assist gas passage.

  In the nozzle, a straight small-diameter hole is provided at the tip of the inner nozzle.

  The nozzle further includes a water nozzle that cools the vicinity of the laser processing position outside the outer nozzle.

  Moreover, the front-end | tip part of the said outer side nozzle is provided with the flange part protruded in the radial outward direction.

  In the nozzle, the assist gas ejected from the inner nozzle and the outer nozzle is oxygen gas.

Further, the laser processing apparatus includes a laser processing head that is movable in a direction that moves toward and away from the workpiece, and the laser processing head includes a nozzle that can be attached and detached, and the tip surface of the inner nozzle is formed flat. and the front end face of the inner nozzle, a nozzle having a double structure with a flush or inner position and a front end surface of the outer nozzle, the assist gas ejected from the outer nozzle cone shape, of the inner nozzle A control unit that controls the approaching operation of the laser processing head with respect to the workpiece is configured to form a throttle portion that is subjected to a throttle action by a negative pressure generated in a portion corresponding to the tip surface at a position away from the nozzle tip. A distance data table storing distance data from the tip portion to the aperture portion in each nozzle to be attached and detached is provided.

  According to the present invention, the throttle portion is formed in the assist gas ejected from the nozzle provided in the laser processing head, and laser cutting is performed by matching the throttle portion with the workpiece surface. Therefore, the assist gas can be effectively penetrated into the cutting groove by laser cutting and the processing region in the cutting groove. Therefore, it is possible to effectively discharge the dross in the cutting groove and suppress burning.

It is sectional explanatory drawing which shows the structure of the nozzle which concerns on the 1st Embodiment of this invention, and sectional explanatory drawing along the BB, CC line. It is sectional explanatory drawing which shows a laser cutting process state. It is a section explanatory view of a nozzle concerning a 2nd embodiment. It is the functional block diagram which showed notionally the structure of the control apparatus.

  Hereinafter, the laser processing apparatus according to the embodiment of the present invention will be described with reference to the drawings. The overall configuration of the laser processing apparatus is similar to a general laser processing apparatus, and is a well-known configuration. Only main components in the laser processing apparatus will be described.

  Referring to FIG. 1, a laser processing apparatus according to an embodiment of the present invention (whose overall configuration is not shown) approaches and separates from an appropriate workpiece W such as a long material such as a pipe material or a plate material. A laser processing head 1 is provided which can be moved and positioned in the direction of movement. The laser processing head 1 is provided with a nozzle 3 that is detachable and replaceable.

  The nozzle 3 has a double structure in which an inner nozzle 5 and an outer nozzle 7 are integrally provided. More specifically, the inner nozzle 5 has a configuration in which a tapered hole 9 having a gradually decreasing diameter on the tip side is provided on the inner side. A large-diameter base end portion 11 of the inner nozzle 5 is fitted into a large-diameter hole 13 on the base end portion side of the outer nozzle 7. Flat portions 15 that are D-cut are formed at a plurality of locations on the outer peripheral surface of the base end portion 11 of the inner nozzle 5. That is, the passage 17 through which the assist gas can pass is formed between the inner peripheral surface of the outer nozzle 7 and the outer peripheral surface of the inner nozzle 5 by performing D cut.

  The outer peripheral surface 19 on the front end side of the inner nozzle 5 is formed as a tapered surface having a gradually decreasing diameter on the front end side. The tip side of the inner nozzle 5 is disposed in the tapered hole 21 of the outer nozzle 7. The tapered hole 21 of the outer nozzle 7 communicates with the large-diameter hole 13 and surrounds the tip side of the inner nozzle 5. In addition, the outer peripheral surface 19 of the inner nozzle 5 and the inner peripheral surface of the tapered hole 21 are separated from each other while maintaining an appropriate interval.

  In other words, between the outer peripheral surface 19 of the inner nozzle 5 and the inner peripheral surface of the tapered hole 21 of the outer nozzle 7, a tapered annular passage 23 having a small diameter at the tip side is formed. That is, the annular passage 23 is formed in a circular shape continuous in the circumferential direction. Therefore, the cross-sectional shape of the assist gas ejected from the annular passage 23 is a ring shape continuous in the circumferential direction. The assist gas is converged on the axis of the nozzle 3 by gradually reducing the ring-shaped diameter.

  Therefore, in the nozzle 3, the assist gas is ejected from the straight small-diameter hole portion 25 formed at the tip of the inner nozzle 5 in a columnar shape (round bar shape) concentric with the laser beam LB irradiated to the workpiece W. The cylindrical assist gas from the inner nozzle 5 is throttled by the assist gas ejected in a conical shape from the annular passage 23. Therefore, a throttle portion (waist portion) GW (see FIG. 2) is formed in the assist gas ejected from the nozzle 3.

  In the above configuration, when assist gas is supplied from the central hole 1H provided in the laser processing head 1 to the nozzle 3, the assist gas is annularly formed between the small-diameter hole portion 25 of the inner nozzle 5 and between the inner nozzle 5 and the outer nozzle 7. It is ejected from the passage 23 toward the work W. Therefore, the laser cutting process is performed with the waist portion (squeezed portion) GW formed in the assist gas G ejected from the nozzle 3 aligned with the surface of the workpiece W.

  As described above, when the waist portion GW of the assist gas G is aligned with the surface of the workpiece W, the assist gas G can be effectively penetrated into the cutting groove WG of the workpiece W that has been laser cut. In other words, the flow rate of the assist gas G spreading around the surface WS of the workpiece W is reduced. Therefore, the molten metal (dross) generated during the laser cutting process can be effectively discharged from the cutting groove WG. In addition, the flow rate of the assist gas G spreading along the surface WS of the workpiece W is reduced. This means that when oxygen gas is used as the assist gas G, the oxidation reaction of the workpiece surface WS near the laser cutting position is suppressed. The Rukoto. Therefore, the occurrence of burning is suppressed.

  By the way, the front end surface 5E (see FIG. 2) of the inner nozzle 5 in the nozzle 3 is slightly on the same plane as the front end surface 7E of the outer nozzle 7 or slightly from the front end surface 7E of the outer nozzle 7, for example, about 0.5 mm. A flat surface is formed at the inner position. Therefore, a negative pressure is generated between the assist gas ejected from the inner nozzle 5 and the assist gas ejected from the annular passage 23 at the tip surface corresponding position 27 corresponding to the tip surface 5E of the inner nozzle 5. become. Therefore, the assist gas ejected from the annular passage 23 tends to be drawn inward, and the waist portion GW is more effectively formed.

  Moreover, the said annular channel | path 23 is a cross-sectional shape which forms circular shape over the perimeter as evident from FIG.1 (C). Therefore, the peripheral surface portion of the assist gas G having a circular cross section that is ejected to the workpiece W exhibits a ring-shaped peripheral surface having a uniform gas pressure. In other words, the peripheral surface portion of the assist gas ejected to the workpiece W has no partial difference in gas pressure. Therefore, it is possible to perform laser cutting while always holding a good laser cutting surface regardless of the laser cutting direction of the workpiece W.

  Further, the assist gas G ejected from the inner nozzle 5 concentrically with the laser beam LB is ejected to a portion where the workpiece W is irradiated with the laser beam LB. Therefore, when oxygen gas is used as the assist gas, it can be effectively used for burning the workpiece W. In the laser cutting processing of the workpiece W using the oxidation combustion reaction heat of the workpiece W, when oxygen ejected from the inner nozzle 5 is consumed in the vicinity of the surface of the workpiece, a deep portion (back surface) from the surface WS of the workpiece W is consumed. The oxidation reaction in the vicinity) tends to decrease.

  However, in the present embodiment, the annular oxygen gas ejected from the annular passage 23 surrounds the assist gas ejected from the inner nozzle 5 and is slightly separated from the irradiation position of the laser beam LB on the workpiece W. In the position. Therefore, the amount of oxygen ejected from the annular passage 23 is small in the initial oxidation reaction of the portion irradiated with the laser light, and enters deeply into the cutting groove WG of the workpiece W. That is, it is used for the oxidation reaction of the portion where the progress of the laser cutting process is delayed in the vicinity of the cut end portion on the cut surface by the laser cutting process. Therefore, it is possible to effectively perform laser cutting of the thick workpiece W. In other words, even when the workpiece W is thick, laser cutting can be performed using the oxidation combustion reaction heat evenly from the front surface to the back surface (cut end surface) of the workpiece W. Therefore, laser cutting is performed under the same conditions over the entire cut surface of the workpiece W, and a good cut surface can be obtained over the entire cut surface.

  That is, according to the present embodiment, the assist gas G can be effectively penetrated into the cutting groove WG, and the assist gas G can be supplied straight to the processing region in the cutting groove WG. Therefore, not only the supply of the assist gas to the processing region in the cutting groove is effective, but also the spread of the assist gas from the processing point in the cutting groove to the rear region can be effectively suppressed. Therefore, even when the workpiece W is thick, the oxidation combustion reaction heat by effectively supplying oxygen as an assist gas is used evenly from the front surface to the back surface (cut end surface) of the workpiece W. Laser cutting can be performed. In addition, it is possible to suppress the occurrence of burning when oxygen as the assist gas reaches the rear of the cutting premises.

  FIG. 3 shows the configuration of a nozzle 3A according to the second embodiment of the present invention. In this embodiment, components having the same functions as the components of the nozzle 3 described above are denoted by the same reference numerals, and redundant description is omitted.

  In the second embodiment, in the outer nozzle 7, a plurality of cooling water holes 29 through which cooling water passes are arranged at equal intervals on a conical surface having a small diameter on the lower side at a position outside the annular passage 23. This is a configuration provided. And in order to suppress that the cooling water sprayed from each said cooling water hole 29 is injected directly to a laser processing position, the front-end | tip part of the said outer nozzle 7 is equipped with the flange part 31 projected in the radial outward direction. It is a configuration.

  Therefore, when laser cutting of the workpiece W is performed using the nozzle 3A, the vicinity of the laser cutting processing position of the workpiece W can be cooled by ejecting cooling water from each cooling water hole 29. Therefore, when oxygen gas is used as the assist gas, it is possible to suppress an oxidation reaction caused by oxygen gas that spreads thinly around the surface WS of the workpiece W.

  By the way, when the workpiece 3 is laser-cut by a laser processing apparatus (not shown) using the nozzle 3 having the above-described configuration, the small-diameter hole 25 and the distal end portion of the annular passage 23 depend on the thickness of the workpiece W. Various nozzles having different diameters are attached to and detached from the laser processing head 1 and used.

  Therefore, each nozzle 3, 3 </ b> A is provided with a gap sensor (not shown) that detects a gap between the tip of the nozzle 3, 3 </ b> A and the surface WS of the workpiece W. And the control apparatus 33 (refer FIG. 4) which controls the operation | movement to the direction which approaches / separates the laser processing head 1 with respect to the workpiece | work W is from the front-end | tip part in each nozzle 3, 3A attached / detached to the said waist part GW. Distance data table 35 in which the distance data is experimentally obtained in advance and stored. Further, the control device 33 has a Z-axis control means 37 for controlling the gap between the tip of the nozzles 3 and 3A and the surface WS of the workpiece W based on the data stored in the distance data table 35. Is provided.

  Therefore, when the appropriate nozzle 3 is attached to the laser processing head 1 and laser cutting of the workpiece W is performed, the number of the corresponding nozzle 3 is input to the control device 33 from the input means 39. In the control device 33, when a nozzle 3 number or the like is input, the gap of the corresponding nozzle 3 is selected from the distance data table 35. The gap between the tip of the mounted nozzle 3 and the surface WS of the workpiece W is controlled based on distance data stored in advance in the distance data table 35. That is, the gap is held so that the waist GW in the assist gas ejected from the nozzle 3 is positioned on the surface of the workpiece W. Therefore, as described above, the laser cutting of the workpiece W can be performed satisfactorily.

DESCRIPTION OF SYMBOLS 1 Laser processing head 3 Nozzle 5 Inner nozzle 5E Tip part 7 Outer nozzle 7E End face 9 Tapered hole 17 Passage 23 Annular passage 25 Small diameter hole part 27 End face corresponding position 29 Cooling hole 31 Flange part GW Waist part (throttle part)

Claims (10)

A laser cutting method for a workpiece made of metal, in which the inner nozzle tip surface is formed into a flat surface, and the inner nozzle tip surface is provided on the same plane as the inner nozzle tip surface or at an inner position. The same assist gas is ejected from the inner nozzle and the outer nozzle of the inner nozzle , a negative pressure is generated at a portion corresponding to the tip surface of the inner nozzle, and the assist gas ejected in a conical shape from the outer nozzle is drawn inward. The throttle portion is provided with a throttle action on the cylindrical assist gas ejected from the inner nozzle to form a throttle portion at a position away from the tip of the nozzle, and this throttle portion is aligned with the surface of the workpiece for laser cutting. A laser cutting method characterized by performing processing.   The laser cutting processing method according to claim 1, wherein the periphery of the inner assist gas ejected from the inner nozzle is surrounded by the outer assist gas ejected from the outer nozzle, and the outer assist gas is formed on a cut surface by laser cutting processing. A laser cutting method characterized in that laser cutting is performed by supplying even the end of the cut surface.   3. The laser cutting method according to claim 1, wherein the assist gas is oxygen gas. 4. A nozzle in a laser processing apparatus, wherein an outer nozzle is provided outside a tapered inner nozzle having a tapered hole with a gradually decreasing diameter on the tip side, and an inner peripheral surface of the outer nozzle provided surrounding the inner nozzle, and the The gap between the annular taper hole and the outer peripheral surface of the inner nozzle is formed as a continuous gap over the entire circumference, and the tip surface of the inner nozzle applies a negative pressure to a position corresponding to the tip surface. The throttle portion that is generated and drawn to the inside of the assist gas ejected from the annular tapered hole is formed on a plane that is formed at a position away from the nozzle tip, and is flush with the tip surface of the outer nozzle. Or a nozzle located inside.   The nozzle according to claim 4, wherein the tapered hole of the inner nozzle and the tapered gap between the inner nozzle and the outer nozzle form a passage of the same assist gas.   The nozzle according to claim 4 or 5, wherein a straight small-diameter hole is provided at a tip of the inner nozzle.   The nozzle according to any one of claims 4 to 6, further comprising a water nozzle that cools the vicinity of a laser processing position outside the outer nozzle.   The nozzle according to claim 7, further comprising a flange portion projecting radially outward at a tip portion of the outer nozzle.   The nozzle according to any one of claims 4 to 8, wherein the assist gas ejected from the inner nozzle and the outer nozzle is an oxygen gas. A laser processing apparatus comprising a laser processing head movable in a direction approaching and moving away from a workpiece, the nozzle being attached to the laser processing head so that the nozzle can be attached and detached, and the tip surface of the inner nozzle is formed in a plane, and A nozzle having a double structure in which the tip surface of the inner nozzle is provided on the same plane or inside the tip surface of the outer nozzle, and the assist gas ejected in a conical shape from the outer nozzle is a tip surface of the inner nozzle. The control part that controls the approaching action of the laser processing head with respect to the workpiece is attached and detached. A laser processing apparatus, comprising: a distance data table storing distance data from a tip portion of each nozzle to be replaced to the aperture portion.

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