JP4966846B2 - Laser cutting nozzle cutting performance evaluation method and apparatus, and laser cutting nozzle cutting performance evaluation apparatus - Google Patents

Description

  The present invention relates to a laser processing nozzle cutting performance evaluation method and apparatus, and a laser cutting machine equipped with a laser processing nozzle cutting performance evaluation apparatus.

  There are two types of nozzles used for laser processing: a standard nozzle with a conical shape (conical cylindrical nozzle, abbreviated as CCN) whose nozzle shape converges downward, and the flow path area narrows once and then widens as shown in FIG. There is a supersonic nozzle (abbreviated as Super Sonic Nozzle, SSN) also called a Laval nozzle LN having such a shape.

  In the supersonic nozzle (SSN), as shown in FIG. 3A, when the pressure of the assist gas reaching the nozzle outlet is Pe and the atmospheric pressure (or back pressure) outside the nozzle is Pa, Pe = Pa. In the case of a supersonic nozzle (SSN) manufactured in such a way, gas flows in a state of proper expansion, so that it is possible to maintain a steady state in a wide range of gas flow velocity and density, and a high gap (workpiece and nozzle tip) (That is, the nozzle gap is increased), laser cutting can be performed. Therefore, there are advantages such as being less susceptible to damage due to spatter during processing or contact between the workpiece and the nozzle.

  On the other hand, the standard nozzle (CCN) has several nozzle diameters, and laser cutting is performed by determining the nozzle diameter and assist gas supply pressure according to the type of material to be processed and its plate thickness. Further, as shown in FIG. 3B, the state of the assist gas injected from the nozzle is such that the assist gas flows in a state of underexpansion (Pe> Pa) in terms of a supersonic nozzle (SSN). If the value is increased, the pressure of the assist gas gas decreases rapidly, and cutting cannot be performed. For this reason, it is necessary to set the nozzle gap to be small and perform the cutting process, so that spatter easily adheres to the nozzle tip, and there is a high possibility of damage due to contact between the workpiece and the nozzle.

The performance inspection of the standard nozzle (CCN) and the supersonic nozzle (SSN) is usually performed by an inspection method such as pressure-flow rate measurement or flow rate density measurement. In addition, for example, when a sound collection microphone is installed upstream of the supersonic nozzle (SSN), and the gas flow velocity in the supersonic nozzle (SSN) reaches the supersonic range, it is generated in the supersonic nozzle (SSN). Since the sound to be heard does not reach the sound collecting microphone, there is a technique that detects the change in boundary and detects the sound speed maintenance range of the supersonic nozzle (SSN) (for example, Patent Document 1).
JP 07-280629 A

  However, standard nozzles (CCN) are mass-produced at one time, so some performance inspections are not performed, and others cause cutting defects from the beginning of use. In the case of a supersonic nozzle (SSN), even if it is manufactured to satisfy the condition of Pe = Pa and the gas flows in a state of proper expansion, the state of the gas flow affects the machining shape of the nozzle inner surface. Due to the large amount, it was difficult to create an assist gas flow in a state of perfect expansion. For this reason, there is a region where cutting is unstable with respect to the nozzle gap at the time of laser cutting.

  In addition, the above-mentioned cutting unstable region also depends greatly on the processing accuracy of the nozzle. In the case of a nozzle gap depending on the nozzle, it is understood that the cutting unstable region exists without actually processing the nozzle. There wasn't. In any case, despite the fact that the nozzle processing accuracy affects the laser processing accuracy, it is impossible to know the quality of the nozzle processing accuracy quantitatively and prior to laser processing. It was.

  The present invention has been made to solve the above-described problems of the prior art, and the object of the present invention is to provide a laser capable of quantitatively determining the cutting performance of each laser processing nozzle before performing laser cutting processing. It is an object of the present invention to provide a laser cutting machine equipped with a cutting performance evaluation method and apparatus for a processing nozzle and a cutting performance evaluation apparatus for a laser processing nozzle.

  The laser processing nozzle cutting performance evaluation method according to claim 1 as means for solving the above-described problem is an assist having a diameter substantially equal to a cutting groove width into which an assist gas injected from the laser processing nozzle can flow. An impact pressure measuring device having a gas inlet is provided, and the nozzle gap, which is the distance between the assist gas inlet and the nozzle, is changed continuously or stepwise, and the change corresponding to the change in the nozzle gap is achieved. The gist is to measure the impact pressure of the assist gas and determine whether or not the impact pressure is a laser processing nozzle having a substantially constant impact pressure equal to or higher than the permissible cutting impact pressure.

  The laser processing nozzle cutting performance evaluation device according to claim 2, wherein the impact pressure is provided with an assist gas inlet having a diameter substantially equal to a cutting groove width into which the assist gas injected from the laser processing nozzle can flow. A measuring device is provided, and the laser processing nozzle is provided coaxially with the assist gas inlet of the impact pressure measuring device, and a gap with respect to the assist gas inlet is provided continuously or stepwise so that the laser processing nozzle can be used. While changing the nozzle gap continuously or stepwise, the impact pressure of the assist gas corresponding to the change in the nozzle gap is measured, and the impact pressure has a substantially constant impact pressure equal to or higher than the cutting allowable impact pressure. The gist is to determine whether the nozzle is a laser processing nozzle.

  The laser cutting machine according to claim 3, wherein an impact pressure measuring instrument having an assist gas inlet having a diameter substantially equal to a cutting groove width into which an assist gas injected from a laser processing nozzle can flow is laser-cut. Provided on a work table of a processing machine, the laser processing nozzle is provided so as to be movable and positioned at the axis of the assist gas inlet of the impact pressure measuring device, and a gap between the laser processing nozzle and the assist gas inlet is continuously provided. Alternatively, a laser processing nozzle having a substantially constant impact pressure that is equal to or higher than a cutting allowable impact pressure is measured by measuring an impact pressure of the assist gas corresponding to a change in the nozzle gap while changing in stages. The gist is that it is possible to determine whether or not there is.

  According to the present invention, the impact pressure of the assist gas injected from the laser processing nozzle to the workpiece is measured before the cutting process, and the impact pressure has a substantially constant impact pressure equal to or higher than the cutting allowable impact pressure. It can be determined whether the nozzle is a laser processing nozzle.

  In addition, it is possible to know quantitatively and prior to laser processing whether the nozzle gap is present in the unstable cutting region and whether the nozzle processing accuracy is good or bad. That is, it is possible to avoid the influence on the laser processing accuracy due to the difference in processing accuracy during the manufacturing processing of the laser processing nozzle.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is an explanatory view of a main part of a laser cutting machine 1 according to the present invention, and FIG. 2 is an explanatory view of an impact pressure measuring device 21 provided in the laser cutting machine 1. Since the laser cutting machine 1 is a known laser machine, its detailed description is omitted.

  As shown in FIG. 1, the work table 3 of the laser cutting machine 1 is provided with a portal-shaped X-axis carriage 5 that extends in the Y-axis direction (perpendicular to the X-axis direction) across the work table 3. The X-axis carriage 5 is provided so as to be movable to an appropriate position in the X-axis direction under the control of the numerical controller 7 via guide means (not shown).

  On the X-axis carriage 5 positioned above the work table 3, the laser processing head 9 is appropriately positioned in the Y-axis direction and the Z-axis direction (perpendicular to the X and Y-axis directions) under the control of the numerical control device 7. It can be moved and positioned freely.

  The laser processing head 7 is provided with an optical system (not shown) such as a condensing lens that condenses laser light guided from a laser oscillator (not shown) on the surface of the workpiece W.

  A laser processing nozzle 11 for injecting an assist gas such as oxygen or nitrogen gas to a processing portion on the workpiece surface together with the laser beam condensed by the condenser lens at the time of laser processing is provided below the laser processing head 9. Is provided.

  The laser processing nozzle 11 may be a conical standard nozzle (abbreviated as Conical Cylindrical Nozzle, CCN) in which the shape of the nozzle converges downward, or a shape in which the channel area is narrowed once and then widened as shown in FIG. A supersonic nozzle (abbreviated as Super Sonic Nozzle, SSN), which is also called a Laval nozzle LN, is provided in a detachable and replaceable manner.

  The work table 3 of the laser cutting machine 1 is provided with an impact pressure measuring device 21 for measuring the impact pressure of the assist gas sprayed from the laser processing nozzle 11 on the work surface.

  The mounting position of the impact pressure measuring device 21 on the work table 3 is provided at an appropriate position deviated from the region where normal laser processing is performed so as not to interfere with laser processing.

  The impact pressure measuring device 21 is provided with a measurement face plate 25 having a circular inlet 23 into which the assist gas injected from the laser processing nozzle 11 can flow, and the diameter of the inlet 23 is a collection point. Considering the characteristics of the emitted laser beam and the cutting groove width, the diameter is set to 0.1 to 0.5 mm.

  The measurement face plate 25 is provided with a pressure sensor 27 for detecting the impact pressure of the assist gas, and this pressure sensor 27 is connected to the numerical control device 7 through a signal line 29. The surface position of the measurement face plate 25 is provided so as to be adjustable to the same level as the surface position of the workpiece to be cut.

  The outline of the measurement circuit of the impact pressure measuring device 21 will be described with reference to FIG.

  The output of the pressure sensor 27 is connected so as to be collected and input to a data logger 33 through an amplifier 31 connected to a power source 35. Further, the data logger 33 and the numerical controller 7 are connected, and the data logger 33 is controlled by a measurement program of the numerical controller 7.

  When the impact pressure of the laser processing nozzle 11 is measured by the above-described impact pressure measuring device 21, first, the laser processing head is instructed by a command by the measurement program of the numerical control device 7 of the laser cutting machine 1. The laser processing head 9 is moved and positioned so that the center of the laser processing nozzle 11 attached to 9 and the center of the circular inlet 23 into which the assist gas of the impact pressure measuring device 21 can flow is aligned, The origin is set so that the Z-axis coordinate value of the lower end face of the laser processing nozzle 11 matches the surface position of the measurement face plate 25 (Z-axis coordinate value: Z = 0, nozzle gap: G = 0).

  From this origin setting position (Z-axis coordinate value: Z = 0, nozzle gap: G = 0), the Z-axis coordinate is set to 0 stepwise within the measurement range (0.5 mm to 10 mm) by a command from the measurement program. The assist gas impact pressure [MPa] at each nozzle gap position at this time is read into the numerical controller 7 via the data logger 33, and the nozzle gap [mm] and impact pressure [MPa] Record the relationship with. The impact pressure may be measured while continuously increasing the Z-axis coordinate.

  Fig. 4 shows two supersonic nozzles (SSN) Type.1 and Type.2 manufactured with the nozzle diameter of 2.0 [mm] and 0.8 [MPa]. 21 is a graph showing the measurement result of impact pressure in a nozzle gap range of 0.5 mm to 10 mm. The vertical axis represents impact pressure [MPa], and the horizontal axis represents nozzle gap [mm].

  The design dimensions of these two supersonic nozzles (SSN) Type.1 and Type.2 are the same, but there is a difference in shape accuracy at the time of manufacture. As can be seen from the graph in FIG. It can be seen that there is a solid difference in the fluctuation value of the impact pressure with respect to the nozzle gap in the nozzles of Type 1 and Type 2.

  FIG. 5 shows the relationship between the nozzle gap and the cutting speed when a stainless steel plate (SUS304) having a thickness of 1.0 mm is actually cut using Type.1 and Type.2 of the supersonic nozzle (SSN) described above. The relationship is shown by taking the cutting speed [m / min] on the vertical axis and the nozzle gap [mm] on the horizontal axis.

  From the graph of FIG. 4, in the case of Type.1 nozzles, it can be seen that the impact pressure is drastically reduced when the nozzle gap is in the range of 1.5 mm to 3.0 mm. On the other hand, from FIG. 5, cutting is impossible when the nozzle gap is in the range of 1.0 mm to 3.0 mm.

  On the other hand, as shown in FIG. 4, in the case of Type.2 nozzles, even when the nozzle gap is increased, the magnitude of the impact pressure hardly changes and it can be seen that the pressure is maintained at approximately 0.4 [MPa]. . Also, from FIG. 5, unlike the case of Type 1 nozzles, about 35 [m / min in the entire region of the nozzle gap measurement range of 0.5 mm to 10 mm (the experimental value is 0.5 mm to 9.0 mm). It can be seen that stable cutting is possible at the cutting speed of

  FIG. 6 shows that when the nozzle diameter is 2.0 [mm] and the assist gas supply pressure from the laser processing machine is 0.8 [MPa], the impact pressure in the standard nozzle (CCN) is 0. In the graph of the results measured in the range of 5 mm to 10 mm, the vertical axis represents the impact pressure [MPa], and the horizontal axis represents the nozzle gap [mm].

  Fig. 7 shows the relationship between the nozzle gap and cutting speed in the standard nozzle (CCN) when the nozzle diameter is 2.0 [mm] and the assist gas supply pressure from the laser processing machine is 0.8 [MPa]. Is plotted with the cutting speed [m / min] on the vertical axis and the nozzle gap [mm] on the horizontal axis, showing a range of 0.5 mm to 10 mm.

  From the graph of FIG. 6, it can be seen that the distribution of the impact pressure of the standard nozzle (CCN) is gradually decreased as the nozzle gap is increased, unlike the supersonic nozzle (SSN). That is, it can be seen that stable cutting can be expected only in a limited narrow nozzle gap range of about 0.5 mm to 2.0 mm.

  Also, from the graph plotting the relationship between the nozzle gap and the cutting speed in FIG. 7, when the impact pressure obtained by impact pressure measurement falls below a certain value (actually measured value is about 0.4 [MPa]), the cutting process is performed. It turns out that is no longer possible.

  From the above, it can be understood that the supersonic nozzle (SSN) has a wider and advantageous nozzle gap range that allows better cutting. However, even in the supersonic nozzle (SSN), it can be understood that individual differences in processing accuracy greatly affect the cutting performance.

  Hereinafter, the relationship between the impact pressure and the focus latitude will be described with reference to FIG. First, the meaning of the term focus latitude (Δf) will be described. The term focus latitude (Δf) is a term coined by the inventors of the present application, and is generally similar to what is called depth of focus.

Normally, the depth of focus is a physical characteristic caused only by an optical component such as a lens. However, the focus latitude defined here is also caused by a workpiece to be laser-cut, as shown in FIG. in, when focusing laser light LB by the condenser lens 41, the minimum focal position of the spot diameter d ₀ in the vicinity of the (Fp = 0), the optical axis region of the lens to be considered focus is almost matching When the upper limit of “Fp = + 1” and the lower limit of the focal point are “Fp = −1”, the larger upper and lower limit regions are generally referred to as the greater depth of focus. In some cases, effective cutting cannot be performed at the upper limit position “Fp = + 1” or the lower limit position “Fp = −1”.

  As described above, when effective cutting cannot be performed at the upper limit position “Fp = + 1” or the lower limit position “Fp = −1”, it is assumed that the focal depth (Δf) is small even if the depth of focus is large. Of course, the reverse is also true.

  On the other hand, when effective cutting can be performed at the upper limit position “Fp = + 1” or the lower limit position “Fp = −1”, the focus latitude (Δf) is Δf = 2. That is, the focus latitude (Δf) indicates a margin for cutting, and indicates that the greater the focus latitude (Δf) is, the more stable the cutting performance is.

  9 and 10 show the supersonic nozzle (SSN) of 0.8 [MPa] specification with a nozzle diameter of 2.0 [mm] manufactured separately from the supersonic nozzle (SSN) Type.1 and Type.2. FIG. 8 shows the impact pressure distribution with respect to the nozzle gap and the measurement data regarding the focus tolerance with respect to the nozzle gap.

  As shown in FIG. 9 and FIG. 10, when the impact pressure is in the vicinity of the lower limit (about 0.3 MPa) and the nozzle gap is (0.5 to 3.0 mm), there is almost no focus margin (Δf), and the impact pressure and the focus. It turns out that it is related to tolerance.

  From the above explanation, the laser processing cutting speed and the focal margin are greatly related to the impact pressure. By measuring this impact pressure and importing this impact pressure distribution data into the numerical controller, the individual laser processing nozzles can be measured. Performance can be evaluated and judged quantitatively. Further, this makes it possible to avoid the nozzle gap region as a defective cutting region for a nozzle gap having a large impact pressure variation and smaller than the allowable cutting pressure value, and perform processing without causing a defective cutting.

Explanatory drawing of the principal part of the laser cutting processing machine which concerns on this invention concerning this invention. Explanatory drawing of the outline | summary of the measuring circuit of the impact pressure measuring device which concerns on this invention. FIGS. 3A and 3B are explanatory diagrams of a supersonic nozzle according to the present invention, in which FIG. 3A shows the flow of gas in an appropriately expanded state, and FIG. 3B shows the flow of assist gas in an underexpanded state. Graph showing the measured values of the relationship between the impact pressure [MPa] and the nozzle gap [mm] of the supersonic nozzle (SSN) Type.1 and Type.2 with a nozzle diameter of 2.0 [mm] and 0.8 [MPa] specifications. Using the supersonic nozzle (SSN) Type.1 and Type.2, the actual measured value of the relationship between the nozzle gap and the cutting speed when a stainless steel plate (SUS304) with a thickness of 1.0 mm was actually cut. Graph. Relationship between impact pressure [MPa] and nozzle gap [mm] at standard nozzle (CCN) when the nozzle diameter is 2.0 [mm] and the assist gas supply pressure from the laser machine is 0.8 [MPa] The graph which showed the measured value of. When the nozzle diameter was 2.0 [mm] and the assist gas supply pressure from the laser processing machine was 0.8 [MPa], the measured value of the relationship between the nozzle gap and cutting speed in the standard nozzle (CCN) was shown. Graph. Explanatory drawing regarding the relationship between focus margins. Another supersonic nozzle (SSN) is a graph showing the measured value of the relationship between the impact pressure [MPa] and the nozzle gap [mm] at a supersonic speed of 0.8 [MPa] with a nozzle diameter of 2.0 [mm]. A graph of measurement data related to the focus tolerance with respect to the nozzle gap in a supersonic nozzle (SSN) with a nozzle diameter of 2.0 [mm] and 0.8 [MPa] different from Type.1 and Type.2.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Laser cutting machine 3 Work table 5 X-axis carriage 7 Numerical control device 9 Laser processing head 11 Laser processing nozzle 21 Impact pressure measuring device 23 Inlet 25 Measuring face plate 27 Pressure sensor 29 Signal line 31 Amplifier 33 Data logger 35 Power supply

Claims (3)

An impact pressure measuring device having an assist gas inlet having a diameter substantially equal to the width of a cutting groove into which the assist gas injected from the laser processing nozzle can flow is provided, and the gap between the assist gas inlet and the nozzle is provided. While changing the nozzle gap as a distance continuously or stepwise, the impact pressure of the assist gas corresponding to the change in the nozzle gap is measured, and the impact pressure is a substantially constant impact pressure equal to or greater than the cutting allowable impact pressure. It determines whether it is a laser processing nozzle provided with the cutting performance evaluation method of the nozzle for laser processing characterized by the above-mentioned. An impact pressure measuring device having an assist gas inlet having a diameter substantially equal to the width of the cutting groove into which the assist gas injected from the laser processing nozzle can flow is provided, and the laser processing nozzle is connected to the impact pressure measuring device. The nozzle gap is provided coaxially with the assist gas inlet, and the gap with respect to the assist gas inlet can be positioned continuously or stepwise, and the nozzle gap can be changed while changing the gap of the laser processing nozzle continuously or stepwise. Measuring the impact pressure of the assist gas corresponding to the change in the pressure, and determining whether or not the impact pressure is a laser processing nozzle having a substantially constant impact pressure equal to or higher than a cutting allowable impact pressure. Cutting performance evaluation device for laser processing nozzles. An impact pressure measuring device having an assist gas inlet having a diameter approximately equal to the width of a cutting groove into which the assist gas injected from the laser processing nozzle can flow is provided on the work table of the laser cutting processing machine. A nozzle is provided so as to be movable and positioned at the axis of the assist gas inlet of the impact pressure measuring device, and the gap of the laser processing nozzle with respect to the assist gas inlet is changed continuously or stepwise. The impact pressure of the assist gas corresponding to a change is measured, and it is possible to determine whether or not the impact pressure is a laser processing nozzle having a substantially constant impact pressure equal to or higher than a cutting allowable impact pressure. Laser cutting machine.

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