Apparatus and method for laser numerical control machine tool machining of non-tapered group holes

Abstract

The application discloses a device and method for machining group holes without taper by a laser numerical control machine tool, which is composed of a laser and a galvanometer system, a five-axis numerical control machine tool system and a computer control system; a processing technology adopted is inclined workpiece rotation drilling, a hole diameter is determined by a diameter of a circle filled by the galvanometer scanning, and a hole type is determined by a workpiece inclination angle; in the processing technology, a relative position between a laser optical axis and a rotating shaft of the five-axis numerical control machine tool is required to be kept unchanged, so that the five-axis numerical control machine tool can be controlled through interpolation linkage to machine the group holes without taper at different positions of the workpiece, so that the group holes without taper are machined. The application effectively combines the advantages of the laser processing and the five-axis numerical control machine tool, and realizes high-quality, high-precision and high-efficiency machining of the group holes without taper.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of laser precision machining, and particularly relates to a device and method for machining group holes without taper by a laser numerical control machine tool. BACKGROUND

[0002] Compared with other hole drilling methods, laser drilling has the advantages of large depth-diameter ratio, no contact, no tool wear, fast processing speed, small surface deformation, and the ability to process various materials, and can well meet the requirements of modern industrial product processing and is widely used in key parts of high-end products such as aerospace, electronic instruments and medical devices. Five-axis linkage computer numerical control machining technology has the advantages of process concentration, flexibility and high automation, and can realize high-precision machining of special-shaped surfaces in space through the combined movement of three linear motion mechanisms and two rotating shafts, and can be well applied to the group hole machining and manufacturing of high-curvature complex aero parts such as turbine blades of aero engines.

[0003] When laser processing a micro-hole with a large depth-diameter ratio, the material removal rate will be large in the middle and small at both ends due to the distribution characteristics of laser energy, resulting in a taper of large at the top and small at the bottom in the hole at the initial stage of hole forming. Once the taper is formed, a large amount of reflection will be generated due to the sharp increase of the incident angle when the subsequent laser is incident on the hole wall, which makes it difficult to further remove the tapered sidewall material, and thus the difficulty of deep micro-hole processing is further increased. Therefore, the taper control of the hole type has always been a difficulty in deep micro-hole processing.

[0004] In view of these problems, there are currently methods for changing the laser incident angle to reduce the taper of the hole type: inclined beam rotation machining and inclined workpiece rotation machining, but the former has high precision requirements for the equipment, a relatively complex structure and high price; the latter needs to keep the relative position of the laser optical axis and the workpiece rotation axis at all times, and cannot meet the requirements of large-scale and high-efficiency group hole machining process. SUMMARY

[0005] In order to solve the defects existing in the prior art, the present application provides a device and method for machining group holes without taper by a laser numerical control machine tool, which adopts a processing method combining femtosecond laser and five-axis numerical control machine tool, and through optical, mechanical and electrical control technology, a high-quality and high-efficiency process method for machining group holes without taper is expected to be realized.

[0006] To achieve this purpose, the present application adopts the following technical solutions:

[0007] A device for machining group holes without taper by a laser numerical control machine tool, comprising a laser and galvanometer system, a five-axis numerical control machine tool system and a computer control system.

[0008] The laser and galvanometer system comprises a femtosecond laser first mirror, an aperture diaphragm, a 1 / 4 wave plate, a second mirror and a scanning galvanometer, the five-axis numerical control machine tool system comprises a five-axis numerical control machine tool and a tool clamp, and the computer control system comprises a computer controller.

[0009] The femtosecond laser emits laser light which converges on a workpiece through the first mirror, the aperture diaphragm, the 1 / 4 wave plate, the second mirror and the scanning galvanometer, the workpiece is fixed on the five-axis numerical control machine tool through the tool clamp, and the computer controller is used for connecting to control the femtosecond laser, the scanning galvanometer and the five-axis numerical control machine tool.

[0010] The wavelength of the femtosecond laser is 1030 nm, the pulse width is 290 fs, the maximum average power is 20 W, the maximum repetition frequency is 200 kHz, and the polarization state is linear polarization.

[0011] The first mirror and the second mirror are both single-wavelength 1030 nm mirrors, and the incident angle of laser on the mirror is 45°.

[0012] The 1 / 4 wave plate is used for adjusting linearly polarized light emitted by the femtosecond laser into circularly polarized light, so as to improve the roundness of the aperture outlet.

[0013] The scanning galvanometer can perform opening and closing and filling scanning operations of laser.

[0014] The five-axis numerical control machine tool can realize horizontal straight line movement in X, Y and Z directions, the A shaft can realize tilting movement around the X shaft, and the C shaft can realize rotating movement around the Z shaft; the XYZ shaft positioning accuracy of the five-axis numerical control machine tool is 0.01 mm, the repeat positioning accuracy is 0.005 mm, the A shaft rotation angle is ±110°, the positioning accuracy is 10'', the repeat positioning accuracy is 5'', the C shaft rated speed is 200 rpm, and the maximum speed is 400 rpm.

[0015] The numerical control system of the five-axis numerical control machine tool is a Siemens numerical control system, the motion of the five-axis numerical control machine tool is controlled, point position motion and interpolation motion modes can be performed, NC data exchange is realized through PLC, and the motion of the machine tool is realized through the upper computer.

[0016] A method for machining a group of non-tapered holes by a laser numerical control machine tool, which is based on a device for machining a group of non-tapered holes by the laser numerical control machine tool, and comprises the following steps:

[0017] The method is a tilt workpiece rotation machining method, the laser optical axis and the machining plane form an angle of θ through the movement of the A-axis of the five-axis numerical control machine tool, forming a tilt machining, the size of the tilt angle determines the taper of the micro-hole, the femtosecond laser forms a circular filling machining path through the scanning galvanometer control, and the diameter of the filled circle determines the diameter of the micro-hole; in the machining process, the workpiece is continuously rotated by the C-axis of the five-axis numerical control machine tool, and the laser optical axis and the C-axis of the five-axis numerical control machine tool always intersect at the hole machining position;

[0018] By the method of converting the reference system, the XYZC linkage control of the five-axis numerical control machine tool is relied on, when the laser machining other points, the laser optical axis always intersects with the rotation axis of the machining point at the hole center position.

[0019] The further improvement of the present application is that the specific implementation method of the method is as follows:

[0020] When machining the first hole, the machining center O1 is coincided with the C-axis position of the five-axis numerical control machine tool, after the A-axis of the five-axis numerical control machine tool is deflected by θ, the workpiece is tilted by θ, the C-axis of the five-axis numerical control machine tool and the laser optical axis also form an angle of θ, the machining center O1 is coincided with the laser optical axis by adjusting the X-axis and Y-axis positions of the five-axis numerical control machine tool, at this time, the laser optical axis intersects with the C-axis of the five-axis numerical control machine tool at the machining center O1; when machining the next hole, the XY-axis of the five-axis numerical control machine tool is moved, so that the next machining point O2 is coincided with the laser optical axis, the hole normal direction is the C' axis, the laser optical axis intersects with the C' axis at O2, and the linear distance between the C-axis and the C' axis is Δr.

[0021] When the five-axis numerical control machine tool moves around the C-axis, relative to the ground reference system, the O1 point is stationary, and the O2 will make a spatial uniform circular motion with the O1 as the center and Δr as the radius, that is, relative to the ground reference system, the workpiece rotates with the C-axis of the five-axis numerical control machine tool; at this time, the XYZ-axis of the five-axis numerical control machine tool makes a circular interpolation motion through the numerical control system control, relative to the ground reference system, the center of the interpolation motion is coincided with the O1 point of the initial position, and the interpolation radius is Δr, the interpolation motion and the C-axis rotation motion are kept synchronous at all times, that is, the two motions start and stop at the same time, and the combined interpolation speed of the XYZ-axis and the linear speed of the C-axis rotation need to be the same at all times; in the machine tool reference system, the motion trajectory of O2 is the same as that of the five-axis numerical control machine tool in the ground reference system, so relative to the ground reference system, the O2 point is stationary, and because O1 and O2 are on the workpiece, the relative position and mutual motion relationship of the two points do not change, therefore O1 will make a spatial uniform circular motion with O2 as the center and Δr as the radius, that is, relative to the ground reference system, the workpiece rotates with the C' axis of the five-axis numerical control machine tool, so as to realize the tilt rotation machining of the O2 hole.

[0022] The above process is repeated, so as to realize the group hole machining of the workpiece.

[0023] Compared with the prior art, the present application has at least the following beneficial technical effects:

[0024] The device for processing non-tapered group holes by a laser numerical control machine tool provided by the present application can realize high-quality and high-precision non-tapered array micro group hole processing, fully utilizes the characteristics of the scanning galvanometer system and the five-axis numerical control machine tool system, such as process concentration, high precision, flexibility and high automation, facilitates the realization of different scanning modes, different inclination angles and different rotation speeds of the laser processing technology, is flexible to operate, has a large processing range and high positioning precision, and can be applied to micro hole processing of different shapes and different materials.

[0025] The linkage control of the laser, the galvanometer system and the five-axis numerical control machine tool system can be realized through the computer controller, so that the integrated processing of the non-tapered array micro group hole is better realized.

[0026] The method for processing non-tapered group holes by a laser numerical control machine tool provided by the present application adopts a femtosecond laser inclined rotation drilling process, can realize micro hole processing of any aperture through the scanning galvanometer, and can realize non-tapered deep hole processing through the five-axis numerical control machine tool, and has high processing quality and good precision, and the hole wall is free of processing defects such as recast layer and burr.

[0027] Through the five-axis numerical control machine tool interpolation linkage control based on the coordinate conversion relationship, the non-tapered group hole processing of different orientations and different processing positions on workpieces of different sizes can be realized under the same processing technology, the processing efficiency is high, the position precision of the hole is high, and the consistency is good. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 FIG. 1 is a structural schematic diagram of the device for processing non-tapered group holes by a laser numerical control machine tool according to the present application;

[0029] Figure 2 FIG. 3 is a process method schematic diagram of the laser inclined rotation micro hole processing according to the present application;

[0030] Figure 3 FIG. 5 is a schematic diagram of the change of the alignment position of the laser optical axis and the rotation center after the thickness of the workpiece is changed;

[0031] Figure 4 FIG. 7 is a principle schematic diagram of the group hole processing process according to the present application;

[0032] Figure 5 FIG. 9 is a light mirror diagram of the coincidence position of the laser optical axis and the machine tool rotation axis according to the present application, Figure 5 (a) is an example diagram after manual adjustment, Figure 5 (b) is an example diagram after adjustment through machine tool interpolation motion;

[0033] Figure 6 FIG. 11 is a 3*3 array group hole processing sequence schematic diagram according to the present application.

[0034] Figure 7 An entrance and exit electron micrograph of the 3*3 array group hole described in the present application, Figure 7 (a) is the entrance, Figure 7 (b) is the exit.

[0035] The reference signs are as follows:

[0036] 1-femtosecond laser, 2-first mirror, 3-aperture diaphragm, 4-1 / 4 wave plate, 5-second mirror, 6-scanning galvanometer, 7-workpiece, 8-tool clamp, 9-five-axis numerical control machine tool, 10-computer controller. DETAILED DESCRIPTION

[0037] In order to better illustrate the present application, the present application will be further described in detail below in combination with the drawings and specific embodiments.

[0038] As Figure 1 shown, the present application provides a laser numerical control machine tool processing non-tapered group hole processing device, which comprises a femtosecond laser 1, a first mirror 2, an aperture diaphragm 3, a 1 / 4 wave plate 4, a second mirror 5, a scanning galvanometer 6, a tool clamp 8, a five-axis numerical control machine tool 9 and a computer controller 10.

[0039] The femtosecond laser 1 is horizontally placed on an optical platform, and the generated laser light path sequentially passes through the first mirror 2, the aperture diaphragm 3, the 1 / 4 wave plate 4, the second mirror 5 and the scanning galvanometer 6 which are fixedly installed by screw connection. The scanning galvanometer 6 is fixedly installed on the Z-axis of the five-axis numerical control machine tool 9, and the height position of the scanning galvanometer 6 and the five-axis numerical control machine tool 9 directly below can be adjusted through the numerical control system. The tool clamp 8 is fixedly installed on the rotating platform of the five-axis numerical control machine tool 9 by screw connection, and the workpiece 7 can be fixed on the tool clamp 8, and the machining position is opposite to the laser light from the scanning galvanometer 6. The computer controller 10 is connected with the femtosecond laser 1, the scanning galvanometer 6 and the five-axis numerical control machine tool 9, so as to realize the control of parameters such as laser power, repetition frequency, single pulse energy, laser scanning times and scanning filling path, and the motion control and linkage control of the five-axis numerical control machine tool XYZAC.

[0040] Embodiment:

[0041] The present application provides a laser numerical control machine tool processing non-tapered group hole processing method, which processes a group of 3*3 non-tapered array group holes on a 2mm thick stainless steel flat plate, the hole diameter is 550μm, and the center distance between adjacent two holes is 800μm. Specifically, the following steps are included:

[0042] Step one: find the position of the laser optical axis and the rotation center. Turn on femtosecond laser 1, scanning galvanometer 6, five-axis numerical control machine tool 9 and computer controller 10, control the laser power to be 2w through computer controller 10, five-axis numerical control machine tool 9 A-axis deflection 4°, in order to facilitate observation and avoid damage to the workpiece material, 0.5mm thick silicon wafer is used for experiment. If the laser optical axis and the five-axis numerical control machine tool C-axis do not coincide on the workpiece surface, open the femtosecond laser 1, control the C-axis movement to make the workpiece rotate clockwise 180°, the laser rotates counterclockwise 180° relative to the workpiece, and leaves a semicircular machining track on its surface, the center of the track is the position of the rotation axis of the five-axis numerical control machine tool 9, turn off the femtosecond laser 1, remove the silicon wafer test piece to the same position on the fixture 8 and put it under the optical microscope to observe and measure the Δx and Δy distance from the end point of the semicircular track to the center position, according to the azimuth relationship between the laser and the position of the rotation axis of the five-axis numerical control machine tool 9, adjust the X-axis and Y-axis of the five-axis numerical control machine tool 9 to move Δx and Δy respectively, so that the rotation axis is close to the laser optical axis, turn on the femtosecond laser 1 again, control the C-axis of the five-axis numerical control machine tool 9 to rotate 180°, at this time the machining pattern on the silicon wafer test piece under the optical microscope is as shown in Figure 5 (a), the machining track becomes a circular pit instead of a circular arc, which indicates that the laser optical axis coincides with the rotation axis of the five-axis numerical control machine tool 9 on the surface of the silicon wafer, and the position x0 and y0 of the X-axis and Y-axis of the five-axis numerical control machine tool 9 at this time are recorded.

[0043] Step two: find the laser focal point by using the scribing method. Since the workpiece is in an inclined state at this time, the height of the laser to the workpiece surface is not consistent along the Y-axis direction, so only the X-axis and Z-axis can be moved to find the focal point position by scribing method, the height corresponding to the thinnest line is the focal position of the laser, turn off the laser, record the position z0 of the Z-axis of the five-axis numerical control machine tool 9 at this time, and the laser focal point is located on the upper surface of the silicon wafer.

[0044] Step three: five-axis numerical control machine tool interpolation linkage control verification. Control the XYZ-axis position of the five-axis numerical control machine tool 9 to return to x0, y0 and z0, establish the workpiece coordinate system on the surface of the silicon wafer through the coordinate transformation relationship, since the scanning galvanometer 6 is fixed on the Z-axis of the five-axis numerical control machine tool 9 and does not move with the XY-axis of the five-axis numerical control machine tool 9, after determining the next machining point in the workpiece coordinate system, the XY-axis of the five-axis numerical control machine tool 9 needs to be moved in the opposite direction to reach the next machining position. As Figure 4As shown, the five-axis NC machine tool 9 is controlled to make a circular interpolation motion with the initial machining point position Oi as the center and Δr as the radius on the workpiece coordinate system, while the five-axis NC machine tool 9 C-axis is rotated. Through the FGROUP(C) instruction of the numerical control system, the C-axis of the five-axis NC machine tool 9 can be set as the trajectory axis, and the XYZ axes can be set as the synchronous axes, that is, when the XYZC axes make linkage motion, the feed rate of the C-axis remains unchanged, and the feed rates of the XYZ axes are adjusted in real time along with the motion path and the C-axis speed, so that the speed and time of the circular interpolation motion and the C-axis rotation motion are equal, thereby ensuring the consistency of the two motions. The femtosecond laser 1 is turned on, the C-axis of the five-axis NC machine tool 9 is rotated clockwise by 180° at this position, and the five-axis NC machine tool 9 is controlled to make one cycle of interpolation motion clockwise, the femtosecond laser 1 is turned off, the five-axis NC machine tool 9 is controlled to move to the next machining position on the workpiece coordinate system, and the above operation is repeated. Figure 5 (b) is the observation result of the machining pattern under the optical microscope, in which the central point is the initial position, that is, the manual alignment position, and the other points are the machining patterns obtained after one cycle of interpolation motion of the XYZ axes of the five-axis NC machine tool 9 and one cycle of rotation of the C-axis. It can be seen that the machining patterns at the other positions are basically the same as the machining pattern at the initial point, which indicates that the same machining effect as the initial point can be achieved at different machining positions through the interpolation linkage control of the five-axis NC machine tool.

[0045] Step four: replace the workpiece to determine the machining position. The 0.5 mm silicon wafer is removed, and the 2 mm stainless steel workpiece is fixed on the tool clamp 8. Since the workpiece is in an inclined state, the alignment position of the laser optical axis and the rotation axis changes after the thickness of the workpiece changes, as shown in Figure 3 The thickness of the workpiece is h = 1.5 mm, the inclination angle is θ, Δy = h sin θ, and Δz = h cos θ. The Y-axis and the Z-axis of the five-axis NC machine tool 9 are adjusted to move Δy and Δz respectively, at this time, the positions of the XYZ axes are x1 = x0, y1 = y0- Δy, and z1 = z0+ Δz, the laser optical axis coincides with the rotation axis of the five-axis NC machine tool 9 on the surface of the workpiece, and the initial machining position can be determined by adjusting the workpiece clamping position according to the laser indicating spot.

[0046] Step five: group hole processing. Draw a circular fill scan trajectory and set scan parameters using the scan mirror control software on the computer controller 10. The scan radius is 200 pm, the circular fill spacing is 20 pm, the scan speed is 100 mm / s, and the scan mode is from outside to inside. Control the five-axis CNC machine tool 9 to move in the negative direction of the Z axis by Δz = 1 mm, which is the negative defocusing amount required for processing, adjust the laser power to 20 w, turn on the femtosecond laser 1 and the scan mirror 6, control the five-axis CNC machine tool 9 to make clockwise rotation movement of the C axis at a speed of 1800° / min, and process for 4 min. Turn off the femtosecond laser 1, control the five-axis CNC machine tool 9 to move in the negative direction of the X axis by Δx = 800 pm, which is the center-to-center spacing of adjacent two holes, turn on the femtosecond laser 1, and process the micro-holes through the five-axis CNC machine tool interpolation linkage control of step three, with a processing time of 4 min. Repeat the above steps according to the processing sequence shown in FIG. 8, with the middle hole as the starting position, and sequentially complete the processing of the remaining 7 holes. Figure 6 After the processing of the holes, the entrance and exit morphologies of the holes are as shown in FIGS. 9(a) and 9(b). Figure 7 Figure 7 (a) is the entrance, Figure 7 (b) is the exit.

[0047] Step six: processing is completed. After the array group hole processing is completed, remove the workpiece 7, and turn off all the equipment.

[0048] Although the present application has been described in detail in the foregoing description with general principles and specific embodiments, some modifications or improvements can be made to the present application on the basis of the present application, which is obvious to those skilled in the art. Therefore, these modifications or improvements made on the basis of not deviating from the spirit of the present application, all belong to the scope of protection claimed by the present application.​

Claims

1. A method for laser CNC machine tool machining of a group of holes without taper, characterized in that, The method is based on a device for processing group holes without taper by a laser numerical control machine tool, the device comprising a laser and a galvanometer system, a five-axis numerical control machine tool system and a computer control system; the laser and the galvanometer system comprises a femtosecond laser, a first mirror, an aperture diaphragm, a 1 / 4 wave plate, a second mirror and a scanning galvanometer, the five-axis numerical control machine tool system comprises a five-axis numerical control machine tool and a tool fixture, and the computer control system comprises a computer controller; the femtosecond laser emits laser light which converges on a workpiece through the first mirror, the aperture diaphragm, the 1 / 4 wave plate, the second mirror and the scanning galvanometer, the workpiece is fixed on the five-axis numerical control machine tool through the tool fixture, and the computer controller is used for connecting to control the femtosecond laser, the scanning galvanometer and the five-axis numerical control machine tool; The five-axis numerical control machine tool can realize horizontal linear motion in X, Y and Z directions, the A axis can realize tilting motion around the X axis, and the C axis can realize rotating motion around the Z axis; the positioning accuracy of the XYZ axis of the five-axis numerical control machine tool is 0.01 mm, the repeat positioning accuracy is 0.005 mm, the rotation angle of the A axis is ±110°, the positioning accuracy is 10'', the repeat positioning accuracy is 5'', the rated rotating speed of the C axis is 200 rpm, and the maximum rotating speed is 400 rpm; the numerical control system of the five-axis numerical control machine tool is a Siemens numerical control system, which controls the motion of the five-axis numerical control machine tool, can realize point motion and interpolation motion mode, and realizes the motion control of the machine tool by PLC and NC data exchange The method comprises: The method is a tilt workpiece rotation machining method, through the movement of the five-axis numerical control machine tool A axis, the laser optical axis and the machining plane form an angle of By converting the reference system, the XYZC linkage control of the five-axis numerical control machine tool is relied on to realize that the laser optical axis always intersects with the rotation axis of the processing point at the hole center position when other points are processed by laser; , forming a tilt machining, the tilt angle determines the taper of the micro-hole, through the scanning galvanometer control femtosecond laser forming a circular filling machining path, the diameter of the filled circle determines the diameter of the micro-hole; in the machining process, the five-axis numerical control machine tool C axis drives the workpiece to rotate constantly, and the laser optical axis and the five-axis numerical control machine tool C axis always intersect at the hole machining position; The specific implementation method of the method is as follows: The above process is repeated, and the group hole processing of the workpiece can be realized. When processing the first hole, the machining center O 1 coincides with the C-axis position of the five-axis NC machine tool, and the A-axis of the five-axis NC machine tool deflects The wavelength of the femtosecond laser is 1030 nm, the pulse width is 290 fs, the maximum average power is 20 W, the maximum repetition frequency is 200 kHz, and the polarization state is linear polarization. , then the workpiece is tilted The first mirror and the second mirror are single-wavelength 1030 nm mirrors, and the incident angle of laser on the mirror is 45°. , the C-axis of the five-axis NC machine tool also forms an angle with the laser optical axis The 1 / 4 wave plate is used to adjust the linearly polarized light emitted by the femtosecond laser into circularly polarized light to improve the roundness of the hole outlet. , and the machining center O 1 coincides with the laser optical axis by adjusting the X-axis and Y-axis positions of the five-axis NC machine tool, at this time the laser optical axis intersects with the C-axis of the five-axis NC machine tool at the machining center O 1; when processing the next hole, the XY-axis of the five-axis NC machine tool is moved so that the next machining point O 2 coincides with the laser optical axis, the normal direction of this hole is the C′-axis, the laser optical axis intersects with the C′-axis at O 2, and the straight-line distance between the C-axis and the C′-axis is Δ r ; When the five-axis NC machine tool moves around the C-axis, the relative ground reference system, O 1 is stationary, O 2 will be O 1 as the center, Δ r for the radius of the space uniform circular motion, that is, relative to the ground reference system, the workpiece with five-axis NC machine tool C-axis rotation; At this time, through the numerical control system control five-axis NC machine tool XYZ axis to do circular interpolation motion, relative to the ground reference system, the center of the interpolation motion and the initial position of O 1 coincides, interpolation radius is Δ r , interpolation motion and C-axis rotation motion at the same time, that is, the two motion starts and stops, the XYZ axis of the composite interpolation velocity and C-axis rotation line speed need to be the same at all times; In the machine tool reference system, O 2 trajectory and five-axis NC machine tool trajectory in the ground reference system is the same, so relative to the ground reference system, O 2 is stationary, and because O 1 and O 2 are on the workpiece, the relative position of the two points and the mutual motion relationship does not change, so O 1 will be O 2 as the center, Δ r for the radius of the space uniform circular motion, that is, relative to the ground reference system, the workpiece with five-axis NC machine tool C′ axis rotation, so as to realize O 2 hole tilt rotation processing; The scanning galvanometer can perform opening and closing and filling scanning operations on laser.

2. A method of machining a group of holes without taper by a laser CNC machine tool according to claim 1, characterized in that, ​ 3. A method of machining a group of holes without taper by a laser CNC machine tool according to claim 1, characterized in that, ​ 4. A method of machining a group of holes without taper by a laser CNC machine tool according to claim 1, characterized in that, ​ 5. A method of machining a group of holes without taper by a laser CNC machine tool according to claim 1, characterized in that, ​

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