JP2014519982A - Method, workpiece and laser apparatus for breaking and dividing a workpiece - Google Patents

Abstract

  Disclosed is a method for breaking and dividing a workpiece and a workpiece manufactured according to the method. According to the present invention, at the time of laser processing, the moving speed and / or the laser pulse are modulated according to the shape and / or period of the workpiece.

Description

  The present invention relates to a method for breaking and dividing a workpiece, a workpiece manufactured according to the method and a laser device according to the preamble of claim 1.

  Patent document 1 by the present applicant discloses a fracture dividing method in which a notch for determining a fracture surface by laser energy is formed at an upper end portion of a connecting rod to be fractured and divided. The notch is composed of a plurality of notches, and the distance of the notch is substantially determined by the pulse rate of the laser and the feed rate of the laser beam with respect to the upper end of the connecting rod. According to the above method, the stress concentration coefficient can be made very large with respect to the continuous notches by the notch portions, and the notches can be formed with a relatively small laser output. The small laser power and the accompanying low thermal energy introduced can prevent undesired deep structural changes in the notch region. Structural changes occur only in certain peripheral areas of the notch, which can improve the fracture splitting behavior.

  Applicant's US Pat. No. 6,057,077 discloses an improved method of forming a notch to have a sinusoidal shape with linearly extending ends rather than a linear shape. Unexpectedly, the fracture splitting behavior can be further improved by designing the notches in that way.

  A laser notch including such a notch portion is established as a state of the art, particularly in the breaking division of a connecting rod and a crankcase, because its breaking behavior is superior to that of a continuous notch. Although these break splitting properties are useful, attempts have been made to further improve the break splitting behavior.

European Patent No. 0 808 228 B2 German Patent Application 2005 031 335 A1

  An object of the present invention is to provide a method capable of easily forming a notch portion of a fracture split notch. Another object of the present invention is to provide a workpiece manufactured according to the method and a laser apparatus for carrying out the method.

  The object is achieved by a method comprising a combination of features as claimed in claim 1, a workpiece comprising the features as claimed in claim 10 and a laser device comprising the features as claimed in claim 12.

  In the method according to the present invention, a laser notch having a plurality of notches is formed using laser energy as in the conventional method. According to the present invention, during the formation of a notch using a laser, the modulation of the feed, i.e. the relative movement between the laser beam and the workpiece being effectively involved and / or the laser pulse, Used. By the modulation, the depth of the notch portion or the distance between the notches can be varied. The depth of the notch means the penetration depth of the laser beam in the direction of the laser beam. Further, the depth of the continuous region (hereinafter referred to as “notch base”) can be changed by changing the moving speed and / or the pulse parameter. Such notches have a higher stress concentration factor and improved fracture mechanics than conventional notches having a substantially constant shape. The method can be performed using virtually any laser used for break splitting.

  The laser beam is preferably irradiated obliquely with respect to the longitudinal notch axis.

  Unexpectedly, with proper selection of the above criteria, even with very high pulse rates and high moving speeds, with perforations that have a significantly larger notch distance than the calculated notch distance A notch can be formed. The above method has the advantage that a high-frequency laser having a very high moving speed can be used, and a laser notch can be formed at a higher speed while reducing the amount of heat introduced compared to conventional solutions. is there.

  According to the present invention, it is preferable to change the moving speed according to a periodic function, for example, a sine function, or to change the moving speed according to the shape of the part.

  The moving speed at the time of laser processing can be changed in the range of 100-1500 mm / min.

  The laser beam can be moved relative to a stationary workpiece, for example, by moving the laser head or, more simply, by using an inclined mirror (scanner). Alternatively, kinematic inversion can be used to move the workpiece relative to a stationary laser beam, or a combination thereof can be used. The laser beam can be irradiated in the radial direction, that is, perpendicularly to the fracture split notch, or obliquely with respect to the fracture split notch.

  When the laser beam is irradiated in the radial direction, the notch portion is formed in the normal direction with respect to the notch axis, and when the laser beam is irradiated obliquely, the notch portion is formed inclined with respect to the notch axis. Is done. The laser beam is preferably irradiated at an angle of 45 ° or less with respect to a plane perpendicular to the longitudinal notch axis (in the case of a connecting rod, the radial surface of the upper end portion of the connecting rod). If the connecting rod is held horizontally and the direction of movement is perpendicular to the connecting rod (notch axis), the angle should be 30 ° to the horizontal direction and 60 ° to the vertical direction. (See FIG. 11).

  Pulse modulation can be performed, for example, by changing the pulse width, pulse frequency, pulse amplitude, and / or pulse phase. These parameters change notch depth or inter-notch distance and optimize fracture behavior by pulse modulation alone or by combining recorded pulse output / pulse energy or pulse sequence at constant pulse output, for example Can also be changed. For example, in the case of a viscous material, a peripheral fracture split notch is formed. In those workpieces, the distance between notches or the depth of the notches can be varied depending on the breaking split notch, for example along the upper end of the connecting rod and the part extending outside the upper end of the actual connecting rod. Can be changed.

  By appropriately selecting these parameters, for example, the modulation can be performed by time-controlled pulse energy ramping at a substantially constant pulse frequency. The term “ramping” means a method of increasing and / or decreasing the pulse power towards a ramp during a pulse sequence.

  The modulation can also be performed by pulse sequence / pulse frequency modulation. In such a case, the pulse output can be kept substantially constant.

  As described above, other parameters can also be varied.

  It is also possible to modulate both the speed of movement and the pulses, and such modulation can be performed sequentially or overlapping or simultaneously.

  According to the invention, it is preferred to use a fiber laser as the laser. Fiber lasers are known, and detailed description of the fiber laser structure is omitted.

  In one embodiment of the present invention, a laser having a 50 W or 100 W average power and a pulse rate of greater than 1 kHz, preferably greater than 10 kHz, with a pulse duration of about 100-200 ns is used, with a moving speed exceeding 1000 mm / min. be able to. The pulse rate in the conventional method is approximately within the above range, and the pulse frequency is lower (for example, 50 to 140 Hz).

  In a preferred embodiment of the invention, the notch extends from the continuous notch base.

  The workpiece manufactured according to the method may be, for example, a connecting rod or crankcase, or any workpiece that divides an opening or other region by a fracture splitting method.

  Workpieces manufactured according to the method can have notches with different depths or different notch distances formed by changing the moving speed or pulse of the laser. It is particularly preferable that the change in the moving speed is repeated periodically along the notch portion.

  A laser apparatus for carrying out the method includes a laser module, a laser head for condensing a laser beam emitted from the laser module onto a workpiece to be processed, and a moving axis movable in a moving direction. Including. The moving axis can be controlled by a control device, and the moving distance can be adjusted during laser processing. Also, pulse modulation can be performed by the control device.

  The distance between notches is determined by the period of pulse modulation, for example, the period of pulse energy ramping or pulse frequency modulation. Applicant reserves the right to claim for the above features.

  A very dynamic movement axis is preferred that can change the movement speed with an acceleration of over 0.5 g, preferably 1-2 g. That is, the moving speed profile can be changed with high accuracy so as to have a sinusoidal shape (which may be rectangular).

FIG. 1 shows a schematic view of a laser device for forming a fracture split notch at the upper end of a large connecting rod. FIG. 2 shows an enlarged view of a fracture split notch formed in accordance with the method of the present invention. FIG. 3 shows an enlarged view of the split split notch when the laser power and / or pulse rate is changed. FIG. 4 shows a broken split notch depending on the moving speed. FIG. 5 shows a break split notch depending on the average laser power. FIG. 6 is a diagram for explaining the dependence of the depth of the notch on the moving speed of the laser beam. FIG. 7 is a diagram for explaining the movement speed modulation as a function of time. FIG. 8 is a diagram for explaining the dependence of the notch depth on the average moving speed when moving speed modulation is performed. FIG. 9 shows an image of a fractured split notch under the same conditions with and without moving speed modulation. FIG. 10 shows a schematic diagram of a laser apparatus that can be used in a laser method for performing movement speed modulation. FIG. 11 is a schematic view of the laser head of the laser apparatus shown in FIG. FIG. 12 is a diagram for explaining laser pulse amplitude modulation. FIG. 13 is a diagram for explaining pulse sequence modulation of a laser. FIG. 14 is a modification of the embodiment shown in FIGS. 12 and 13. FIG. 15 is a diagram for explaining the influence of the moving speed and pulse frequency modulation on the notch depth.

  Preferred embodiments of the present invention will be described below in detail with reference to the schematic drawings.

  FIG. 1 shows a cross-sectional view of the upper end portion 1 of a large connecting rod that is divided into a bearing seat and a connecting rod side portion by breaking division. The fracture split surface 2 is predetermined by left and right fracture split notch groups 4 (only one is shown in FIG. 1) extending in the diameter direction, and the fracture split notch group 4 preferably has a plurality of notch portions 6. Perforation. As described in the description of the background art, after the split split notch group 4 is formed on the left and right wall portions of the upper end portion 1 of the connecting rod in FIG. 1, an expansion mandrel is inserted into the upper end portion of the connecting rod, The bearing seat is divided from the rod-side portion of the connecting rod by supporting the upper end with an expansion mandrel, and the two members are accurately and easily combined using the shape of the fractured dividing surface as a result of the structural conditions. be able to.

  A fiber laser is used to form (design) the fracture split notch 4. FIG. 1 schematically shows a laser head 8 of a fiber laser. As such a fiber laser, a diode-pumped solid-state laser in which a glass fiber core constitutes an active medium can be basically used. The solid laser radiation is introduced into the fiber and the actual laser amplification is performed. The laser beam characteristics and beam quality can be adjusted by designing the shape and arrangement of the fiber (glass fiber) so that most of the laser is not subjected to external impact and has a very simple structure. .

  The laser beam emitted from the active fiber is introduced into the glass fiber, and the radiation is guided to the laser head 8 shown in FIG. 1 through the glass fiber, and is focused on the workpiece 1 to be processed by the focus optical system 10. In the embodiment shown in FIG. 1, the laser beam 12 is emitted in the radial direction (normal direction with respect to the notch axis direction (vertical direction in FIG. 1)). Such a configuration has a drawback that the focus optical system 10 may be contaminated by the molten material because the reflected beam and the residual melt return directly along the optical path by irradiating the laser beam at an angle of 90 °. is there. When the laser beam is irradiated in an oblique direction (for example, 30 ° or 45 °), the reflected beam and the residual melt travel at the reflection angle (12 ″ in FIG. 1) and no contamination occurs. Will be described with reference to FIGS.

  Another disadvantage of emitting the laser beam at a 90 ° angle is that no gentle or sharp beam control can be performed. If the laser beam is emitted in an oblique direction, the shape of the notch can be further influenced by gentle (upward in FIG. 11) or sharp (downward in FIG. 11) beam control. Also, the shape of the notch can be further influenced by the airflow acting on the melt through the nozzle. The two features are described in the dependent claims.

  These fiber lasers are superior in achieving excellent beam quality with excellent electro-optic efficiency and deep depth of focus in a very compact structure, and are more cost effective in a smaller structure space than conventional lasers A solution can be provided. Since fiber lasers have high peak power and excellent light collection capability, the energy density is relatively high and the material can be evaporated. However, since some of the energy is converted to heat, there is a thermal impact on the melt and the environment. Residual heat accumulates, resulting in a clear melting phenomenon, and the actual notch distance is clearly larger than the calculated notch distance, and other parameters vary, but the notch distance is relatively stable .

  In FIG. 1, after processing the wall portion of the connecting rod located on the left side, the laser head is rotated about 180 ° to process the wall portion of the connecting rod located on the right side. In principle, it is also possible to use a cross head that can simultaneously process the left and right wall portions.

  In the present embodiment, the workpiece (connecting rod) is fixed, the laser head 8 moves at a feed rate V in the axial direction or parallel to the axis, and the laser output is about 50 W, in the illustrated embodiment. The pulse frequency of the laser is about 20 kHz. The spot diameter is about 30 μm, and the moving speed V is about 1500 mm / min. When these parameters are used, the calculated distance between notches is about 0.00125 mm. The actual distance K between notches when the laser beam is irradiated obliquely at an angle of 45 ° is about 0.1 mm.

  FIG. 2 shows an enlarged view of the upper end of a connecting rod processed according to the method of the present invention using the parameters described above when the laser beam is irradiated obliquely at an angle of 45 °. The average laser power is about 50 W and the pulse power is about 8 kW. The distance between perforations (distance between notches) K is about 0.1 mm, and each notch portion 6 forming a perforation extends from the continuous notch base (G). In the embodiment shown in FIG. 2, the depth of the notch base G is about 0.51 mm, and the depth P (measured from the peripheral wall 14 of the upper end 1 of the connecting rod) of the notch 6 (in the radial direction) is about 0. .78 mm.

  FIG. 3 shows an embodiment similar to FIG. 2, with the laser power reduced (40 W) and the irradiation angle of the laser beam 12 made smaller (30 °). As shown in FIG. 3, there is no significant change, and the notch distance K, the notch base depth G, and the notch depth P are slightly increased. When the irradiation angle is slightly reduced, it is possible to form a notch that improves the fracture behavior with a smaller output than the above-described embodiment.

  FIG. 4 shows the dependence of the fracture split notch on the moving speed V (see FIG. 1) for moving the laser beam in the vertical direction (notch axis direction).

  As is apparent from FIG. 4, the distance between notches hardly changes even when the moving speed (500 mm / min, 1000 mm / min, 1500 mm / min) is changed. When the moving speed is low, the depth G of the notch base increases, and the axial length (PG) of the notch portion is inversely proportional to the moving speed. The difference between 500 mm / min and 1000 mm / min is relatively small.

  FIG. 5 shows the dependence of the break split notch on the laser power. The upper image in FIG. 5 shows the case where the average laser output is set to 50W. The lower image in FIG. 5 shows the case where the average laser output is set to 100 W, and other parameters are the same. As apparent from FIG. 5, when the laser output is decreased, a notch structure having a longer notch is formed, but as described above, the distance between the notches hardly changes. Further, according to the prediction, when the laser output is decreased, a continuous notch base having a slightly shallower depth G is formed as compared with the case where the laser output is high. Therefore, regarding the fracture mechanics, it is considered optimal to use a laser having a relatively small laser power (50 W or less) at an average moving speed in the range of 500 to 1500 mm / min.

  Beam quality can be improved by Q-switches. The Q-switch decreases the pulse duration so that when a pulse delay occurs in the case of a pulsed laser, the pulse duration increases so as to obtain a very sharp laser pulse that rapidly increases and then rapidly decreases again when a sharp maximum is reached, It is an optical component that increases the pulse height (peak performance). When the Q-switch is not used, the pulse has a clearly wider and flat shape.

  FIG. 6 shows the dependence of the notch depth on the moving speed in the range of 100 to 3000 mm / min. The measured value S2 corresponds to the depth G of the predetermined notch base, the measured value S1 corresponds to the total depth P of the notch (see FIGS. 2 and 3), and the length of the notch portion is the difference (GP) ). The upper curve shows the transition of the total notch depth S1, and the lower curve shows the transition of the notch base depth S2. As is apparent from FIG. 6, at a relatively low moving speed in the range up to about 800 mm / min, a relatively strong dependence of the notch depth (S1, S2) on the moving speed is observed. At higher travel speeds (about 800-3000 mm / min), the dependence on travel speed is not clear. These experiments were performed with a pulse frequency of 50 kHz and an average pulse output of 50 W. Therefore, the dependence of the notch shape on the moving speed was confirmed by the experimental results shown in FIG.

  As explained in detail below, at very low travel speeds (less than 200 mm / min), the notch quality was insufficient due to overheating in the region of the notch base. Carbonized (burned) areas were formed, and laser processed workpieces could not be used in practice. The carbonized region is shown, for example, in the upper image of FIG. 9 (details will be described later).

  Therefore, in laser processing, it is necessary to control the moving speed so as to avoid quality degradation when forming a fractured split notch.

  The above phenomenon can be avoided by changing the moving speed during laser processing, and a fracture split notch that has a sufficient depth and can be formed at a high moving speed (short time) is obtained. There is no degradation in quality that causes degradation.

  FIG. 7 shows an example of movement speed modulation performed according to a sine function. Note that the movement speed modulation can also be performed according to another function (preferably a periodic function). FIG. 7 shows the transition of the moving speed as a function of time in a specific range that does not correspond to the total length of the fractured split notch to be formed. Although the movement range of 67.5 to 69.5 mm (that is, 2 mm of the whole fracture split notch) is specifically shown, the movement speed modulation is also performed correspondingly to the area of the fracture split notch not shown. A slightly undulating curve from the upper left side to the lower right side (upper curve shown by dashed line / lower curve shown by solid line) shows the actual movement in the direction of the break split notch as a function of time t. . During such a slightly undulating movement, the moving speed is changed according to the plotted sine function, a sine function having a large amplitude is assigned to a laser path indicated by a broken line, and a sine function having a small amplitude is indicated by a solid line. Assigned to. The moving speed is changed at a relatively high frequency, and the laser head 8 is strongly accelerated and decelerated in a short time in order to adjust the motion profile along the broken split notch to be formed.

In FIG. 7, the actual moving speed after adjustment is shown on the right side. In the upper movement speed modulation, the movement speed was changed in a range of 117 to 1157 mm / min. When such a movement speed modulation is performed to form a fracture split notch, a fracture split notch shape as illustrated in FIGS. 8 and 9 is obtained. FIG. 8 shows a case where the depth of the notch is adjusted as a function of the average moving speed V _m (the average value of the moving speed modulation described above). As shown in FIG. 8, for example, when the average moving speed is 800 mm / min (the moving speed changes according to a sine function as shown in FIG. 7), the fracture split notch plotted in FIG. 8 is formed. As is apparent from FIG. 8, different notch portions are formed from the notch base portion having the measured value S2 (G) corresponding to the sine cycle. The notch portion indicated by S3 is formed in a region where the moving speed is relatively low. The notch portion indicated by S1 is formed in a region where the laser moves at a relatively high speed.

  FIG. 8 shows changes in characteristic parameters S1 (P), S2 (G), and S3 (P) with respect to the average moving speed. The upper curve shows the transition of the total depth (S3) of the notch at a low moving speed, the curve S1 shows the transition of the notch depth at a relatively high moving speed (moving speed modulation), and the curve S2 is the notch base. Shows the transition of the depth. As shown in FIG. 8, increasing the average moving speed decreases the depth of the notch. However, when moving speed modulation is performed, notch portions having different depths can be formed. Such notches have significantly improved fracture mechanics over prior art notches. That is, with the moving speed modulation, the initial fracture toughness and the final fracture toughness are clearly improved with respect to the fracture split notch formed without the movement speed modulation and including continuous drilling. A relatively deep and sharp notch can be formed.

  Therefore, a complicated portion can be broken and the moving speed can be modulated according to the partial shape. That is, for example, in a very complicated part including an opening in the area of the fracture split notch, the moving speed is adjusted according to the shape of the part, and in a non-complex area, the moving speed or the amplitude of the moving speed modulation is relatively high. In more complex areas, the movement speed modulation can be reduced appropriately and adjusted to a lower average movement speed or a constant movement speed.

  The advantages of the moving speed modulation described above will be described with reference to FIG. The upper image in FIG. 9 shows a fracture split notch when using a relatively low constant travel speed of 200 mm / min. The relatively large notch depth and the burning / burning that can be caused by the introduction of heat at low moving speeds are clearly observed. Such a break split notch is substantially useless.

  On the other hand, the lower image in FIG. 9 shows a notch formed while performing moving speed modulation according to the method of the present invention, and the moving speed was modulated in the range of 117 to 1157 mm / min. It is clear that burn speed can be reliably avoided in the region of the notch base by performing movement speed modulation. Also shown are notch portions having different depths formed by appropriate movement velocity modulation, the depth of the notch portion also depending on the tilt angle of the laser. In the illustrated embodiment, the inclination angle (irradiation angle) is about 30 ° with respect to the horizontal direction of FIG.

  With reference to FIG. 10 and FIG. 11, a laser apparatus particularly suitable for carrying out the above-described method of performing movement speed modulation will be described. As shown in FIG. 10, the laser device includes a laser module 16 including, for example, a fiber laser and a fiber laser control device. The control device of the laser module 16 is configured to be able to modulate the moving speed of the laser beam as described above.

The laser beam 12 generated by the laser module 16 is guided to the recollimator 20 via the light guide 18 (see FIG. 10). In the recollimator 20, the laser beam is converted into a parallel beam, and the beam diameter is about 6 mm. The parallel beam is guided to the laser head 8 via the light guide 18 and the laser beam is focused on the workpiece to be processed (in this case, the upper end 1 of the connecting rod). The focused laser beam is irradiated at an angle of 30 ° with respect to the horizontal direction of FIG. The laser head 8 is configured to have a Z movement axis 22, and the Z movement axis 22 causes movement in the longitudinal notch axis. The Z movement axis is a very dynamic axis, which can achieve very high acceleration with high closed loop gain and large jerk (rate of change of acceleration with time) and control modulation very accurately It is necessary. The acceleration can be in the range of 1-2 g, for example, the closed loop gain can be in the range of 10 n / min / mm (166.71 / s), and the jerk can be in excess of 400 m / s ³ . In order to process both sides of the upper end 1 of the connecting rod, the laser head 8 is configured to have a rotating shaft 24 and can be rotated about the Z moving shaft 22. Further, the laser device includes an X adjustment shaft 26 and can move the entire laser head 8 in the X direction (radial direction with respect to the upper end portion 1 of the connecting rod). By such means, a sinusoidal fracture split notch can be formed.

  FIG. 11 shows a basic structure for guiding a beam in the laser head 8. The light guide 18 is connected to a fiber laser (laser module 16). The laser beam is converted into a parallel beam having a beam diameter of about 6 mm in the recollimator 20 and is deflected by 90 ° in the direction of the axis of the upper end portion of the connecting rod by the deflection mirror 28. The deflected laser beam 12 is collected on the wall portion at the upper end of the connecting rod by an optical system having a focal length of 100 mm, for example, and in the illustrated embodiment, the deflecting mirror 32 is inclined at an angle of 60 ° with respect to the horizontal direction. The laser beam is directed to the peripheral wall of the connecting rod by 30 °, and the laser beam has an irradiation angle of 30 ° with respect to the horizontal direction or an inclination angle of 60 ° with respect to the vertical part of the laser beam 12 incident on the deflection mirror 32 (deflection: 60 °) The light enters the peripheral wall of the connecting rod. The laser beam is emitted from the nozzle 34 and is condensed so that the laser spot is located approximately 3 mm in front of the emission surface of the nozzle 34. In order to avoid contamination of the optical system 30 and the mirrors 28 and 32, a protective glass 36 is provided in the optical path between the nozzle 34 and the deflection mirror 32. FIG. 11 also shows a rotating shaft 24. The laser head 8 can be rotated about the Z moving shaft 22 via a rotating bearing 38 by a motor (not shown), and a laser beam can be applied to any peripheral wall region of the connecting rod. Can be irradiated.

  When using a fiber laser and properly selecting movement velocity modulation and a relatively high pulse rate (compared to conventional solutions), drilling with the optimal stress concentration factor is compared to conventional systems. Can be formed with a much lower energy input and a much faster moving speed.

  According to experiments, when a fiber laser having an output of 50 W and a pulse frequency of 20 kHz is used, the notch portion 6 is a split split notch formed with a distance of 1/10 mm, preferably 0.1 to 0.3 mm. 4 can be formed. Even when a laser having an output of 30 W is used, a very effective perforated fracture split notch 4 can be formed.

  In the embodiment described above, movement speed modulation is performed. Instead of the movement speed modulation or in combination with the movement speed modulation, for example, pulse modulation can be performed by the method described below.

  Such pulse modulation can modulate a pulsed carrier or basis function, for example, to change the pulse width, pulse duration or pulse phase. Preferably, the pulse energy (pulse ramping) or pulse frequency / pulse sequence is modulated. In pulse amplitude modulation, the rectangular carrier pulse sequence is changed by changing the pulse amplitude. In pulse duration modulation, the pulse width of the underlying carrier function is changed as appropriate. In pulse phase modulation, the pulse position is phase shifted with respect to the carrier function, and a fixed pulse width and pulse amplitude are used.

  Time-controlled pulse energy ramping by pulse sequence modulation with a constant pulse frequency and a substantially constant pulse output will be described below.

  Time controlled pulse energy ramping applies time control to the current (preferably constant) travel speed and the desired notch grid (perforation grid). In this case, the pulse energy lamp shape approximately represents the perforation shape.

FIG. 12 shows modulation by time controlled pulse energy ramping. FIG. 12 shows the transition of the pulse energy E _Kl with respect to time as a start or carrier function. For example, the pulse energy at a pulse width of 120 ns and a frequency of 50 kHz is 1 mJ. A ramp-like modulation (P _Ramp ) of pulse energy is superimposed on the carrier function (see FIG. 12). The pulse ramp shape has an approximately sinusoidal shape and there is no zero crossing in the illustrated embodiment. However, in principle, other ramps with increasing and decreasing flanks and constant power / energy leveling regions can also be used. In the illustrated embodiment, the modulation of the starting or carrier function is such that the predetermined maximum pulse energy (1 mJ) is periodically reduced so that the maximum pulse energy decrease and the maximum pulse energy increase (ramping) occur approximately sinusoidally. To be done.

By appropriately modulating the carrier function E _Kl , a change in pulse energy (E _Ramp ) having the ramp shape shown is obtained. As is apparent from FIG. 12, the time-series ramp (the ramp shape of the pulse energy) defines the notch distance K, and the ramp shape of the pulse energy indicates the shape of the perforation. In the illustrated embodiment, the moving speed is constant (about 200 mm / min) and the pulse frequency / period of the function P _Ramp is 11.1 Hz. The pulse energy (E _Ramp ) of the laser varies according to the ramp function at the same frequency, and the notch distance K is adjusted depending on the frequency and the selected moving speed. In the illustrated embodiment, the notch distance K is substantially dependent on the frequency / period (11.1 Hz) of the selected ramp function, so the actual pulse frequency (50 kHz (function E _Kl )) and the selected movement. The notch distance K is adjusted to be larger than that calculated from the speed.

FIG. 13 shows an embodiment for performing a pulse sequence or pulse frequency modulation. Similar to the embodiment described above, an output or carrier pulse sequence having a pulse energy of 1 mJ and a pulse width of 120 ns is used. At the time of pulse sequence modulation, the output function is modulated by changing the pulse frequency between the maximum value of 100 kHz and the minimum value of 20 kHz, and the pulse frequency is changed in a substantially sinusoidal shape shown in FIG. The notch distance K is determined by the period of the pulse sequence or frequency change. As is apparent from FIG. 13, a notch having the maximum depth is formed in a region having a pulse output of 1 mJ and a high frequency of 100 kHz. Therefore, the depth of the notch depends on the pulse frequency (when the pulse output is constant). In the illustrated embodiment, the pulse modulation period is 11.1 Hz. The moving speed is 200 mm / min. In such carrier function modulation, pulse sequence modulation E _{KlPf in} which the pulse sequence changes in a range of 10 to 50 μs at a modulation frequency (pulse train period) of _{11.1 Hz} .

  Similar to the embodiment shown in FIG. 12, the notch distance K in such pulse sequence modulation is obtained with a period of 11.1 Hz, and the frequency period (pulse sequence modulation) or the period of the ramp shape (pulse energy ramping) is appropriate. A perforated grid (inter-notch distance K) is obtained by selecting. In the said embodiment, the distance between notches is adjusted to 0.3 mm, for example. Such modulation can be referred to as “frequency wobbling”.

  FIG. 14 shows an embodiment in which the notch depth or inter-notch distance is varied by changing the pulse output P while dynamically controlling the output. The pulse width and pulse amplitude and, if appropriate, the pulse frequency are also varied.

  Basically, at the time of pulse modulation, it is possible to employ a burst mode in which a laser pulse is output from the energy storage device until a certain number of pulses are reached or the energy storage device is discharged. In this case, the fracture split notch is completely formed and the workpiece is fed to another station. The energy storage device is charged for subsequent laser processing when the workpiece is handled.

  The findings according to the present invention will be summarized with reference to FIG. FIG. 15 shows the notch depth as a function of travel speed and pulse frequency.

  As described in detail, when the moving speed is relatively low, the notch becomes deep, and when the pulse frequency is modulated, the depth of the notch increases as the frequency increases. Therefore, when the moving speed is constant, the depth of the notch when the frequency is high (100 kHz) is approximately twice the depth of the notch when the pulse frequency is 50 kHz. In this case, a laser with an average power of 100 W is used with a pulse energy of 1 mJ, a pulse width of 130 ns and an irradiation angle of 90 °.

  As described above, the moving speed and the laser pulse can be modulated. Although the moving speed is mainly changed at the maximum laser output, since the dependence of the notch depth on the modulation of the moving speed is almost linear, the maximum laser output can always be used. By using linear motor technology, the non-machining time can be significantly reduced and the movement speed modulation can be performed relatively easily. Modulation can be further facilitated if the laser is configured to include scanner technology that aligns the laser with tilting mirrors or optics so that the linear axis can be largely omitted. .

  The present invention relates to a method for breaking and dividing a workpiece and a workpiece manufactured according to the method. According to the present invention, at the time of laser processing, the moving speed and / or the laser pulse are modulated according to the shape of the workpiece and / or the laser output.

DESCRIPTION OF SYMBOLS 1 Upper end part of a connecting rod 2 Fracture surface 4 Breaking division notch 6 Notch part 8 Laser head 10 Focus optical system 12 Laser beam 14 Perimeter wall 16 Laser module 18 Light guide part 20 Recollimator 22 Moving shaft 24 Rotating shaft 26 Control shaft 28 Deflection mirror 30 Optical system 32 Deflection mirror 34 Nozzle 36 Protective glass 38 Rotating bearing

FIG. 7 shows an example of movement speed modulation performed according to a sine function. Note that the movement speed modulation can also be performed according to another function (preferably a periodic function). FIG. 7 shows the transition of the moving speed as a function of time in a specific range that does not correspond to the total length of the fractured split notch to be formed. Although the movement range of 67.5 to 69.5 mm (that is, 2 mm of the whole fracture split notch) is specifically shown, the movement speed modulation is also performed correspondingly to the area of the fracture split notch not shown. Slightly wavy curve from the top of the left side toward the bottom of the right (the lower curve shown by the upper curve / broken line shown by a dashed line) may indicate the actual movement in the direction of the fracture splitting notch as a function of time t Yes. During such slightly undulating movement, the moving speed is changed according to the plotted sine function, a sine function having a large amplitude is assigned to the laser path indicated by a solid line , and a sine function having a small amplitude is indicated by a two-dot chain line Assigned to the laser path. The moving speed is changed at a relatively high frequency, and the laser head 8 is strongly accelerated and decelerated in a short time in order to adjust the motion profile along the broken split notch to be formed.

FIG. 7 shows an example of movement speed modulation performed according to a sine function. Note that the movement speed modulation can also be performed according to another function (preferably a periodic function). FIG. 7 shows the transition of the moving speed as a function of time in a specific range that does not correspond to the total length of the fractured split notch to be formed. Although the movement range of 67.5 to 69.5 mm (that is, 2 mm of the whole fracture split notch) is specifically shown, the movement speed modulation is also performed correspondingly to the area of the fracture split notch not shown. A slightly undulating curve from the upper left side to the lower right side (upper curve shown with a dashed line / lower curve shown with a broken line) shows the actual movement in the direction of the breaking split notch as a function of time t. Yes. During such slightly undulating movement, the moving speed is changed according to the plotted sine function, a sine function having a large amplitude is assigned to a laser path indicated by a one-dot chain line , and a sine function having a small amplitude is indicated by a broken line. Assigned to the route. The moving speed is changed at a relatively high frequency, and the laser head 8 is strongly accelerated and decelerated in a short time in order to adjust the motion profile along the broken split notch to be formed.

Claims (15)

  A method for breaking and dividing a workpiece (1) using laser energy, wherein a fracture is determined by relatively moving a laser beam (12) and the workpiece (1). A method characterized in that the divided notches (4) are formed as perforations including a plurality of notches (6), and the laser moving speed (V) and / or pulse parameters are changed during processing.   2. The method according to claim 1, wherein the laser beam is irradiated obliquely with respect to the longitudinal notch axis.   4. The method according to claim 3, wherein the moving speed (V) is changed according to a periodic function, for example, a sine function.   The method according to any one of claims 1 to 3, wherein the moving speed is changed in a range of 100 to 1500 mm / min.   5. The method according to claim 1, wherein the pulse modulation is performed by changing the pulse width, the pulse frequency, the pulse amplitude, and / or the pulse phase, and the parameters are changed alone or in any combination.   6. The method of claim 5, wherein the modulation is performed by time controlled pulse energy ramping at a constant pulse frequency.   Method according to claim 5 or 6, wherein said modulation is performed by pulse sequence / pulse frequency modulation, preferably in the range of 20-100 kHz, at a constant pulse output.   The method according to claim 1, wherein the laser is a fiber laser.   9. The method of any one of claims 1 to 8, wherein the split split notch (4) has a continuous notch base and the plurality of notches (6) extend from the continuous notch base.   A workpiece, in particular a connecting rod or a crankcase, produced by the method according to claim 1.   11. The workpiece according to claim 10, wherein the workpiece has one or more shallow notches (6) and one or more deep notches (6) or notches having different depths (P), depending on the shape of the workpiece. 6) a workpiece having a substantially periodically repeated arrangement.   A laser device for carrying out the method according to any one of claims 1 to 9, comprising a fiber laser and a laser head (8) for condensing a laser beam (12) onto a workpiece to be processed. And at least one moving axis (22) that moves in the moving direction, and a controller (16) that changes the moving speed and / or pulse parameters of the laser while forming the fracture split notch. Laser device to do.   Laser according to claim 12, wherein said moving axis (22) is configured to change said moving speed with an acceleration of less than 0.5g, preferably up to 2g, while forming said fracture split notch. apparatus.   14. The laser device according to claim 12 or 13, wherein an average output of the fiber laser is 100 W or less at a maximum pulse rate of more than 20 kHz, preferably about 100 kHz.   The laser device according to any one of claims 12 to 14, wherein the modulation period is selected so as to be adjusted to a predetermined notch distance (K).