MX2012011690A - Method for fracture splitting workpieces, workpiece and laser unit. - Google Patents

Abstract

The invention relates to a method for fracture splitting workpieces (1) and to a workpiece produced in accordance with such a method. According to the invention, for example the laser type, the pulse rate, the pulse duration, the workpiece material and/or the laser power are selected such that the distance of the notch sections (6) is considerably larger than the notch distance (K) that would be computationally obtained from the feed rate (V) of the laser beam (12) and/or of the workpiece (1) and the pulse rate of the laser. The described feed modulation also enables the formation of oblique laser notches for rolling surfaces, as they occur, for example, in ball or roller guides. According to the invention, the feed rate is also modulated during laser machining depending on the workpiece geometry and/or periodically.

Description

METHOD FOR DIVIDING THROUGH FRACTURE WORK PIECES, WORKPIECE AND LASER UNIT DESCRIPTION OF THE INVENTION The invention relates to a method for breaking up workpieces according to the preamble of claim 1, to a workpiece produced according to a method of this type and to a laser unit.

In EP 0 808 228 B2 the applicant described a method for dividing by fracture of the type under consideration, in which in a connecting rod eye that must be divided by fracture by means of laser energy a notch is formed which preset the plane of fracture. This groove consists of a multitude of notch sections whose distance results essentially from the pulse repetition rate of the laser and the speed of advance of the laser beam relative to the connecting rod eye. It was found that by using these notch sections it is possible to increase the notch effective value considerably compared to the continuous notches, so that it is possible to form a notch with a relatively low laser power. By means of this low laser power and the lower concomitantly introduced thermal energy, a deep, undesired structure change is avoided in the region of the notch, with which only certain areas of the edge REF: 236279 of the notch undergo a transformation of structure and therefore improve the behavior of the division by fracture.

In DE 2005 031 335 A1 of the Applicant is described an improved method, in which the notch is not configured straight but in sinusoidal form with end sections extending straight. Surprisingly it was found that by a notch design of this type it is possible to improve once again the behavior of the division by fracture.

A certain disadvantage of the procedure described above is that - as explained - it is necessary to mutually adapt the speed of advance and the pulse repetition rate so that notch sections are formed that improve the behavior of the notch. It was also found that in particular with the formation of sinusoidal notches or of connecting rod eyes with large axial length it is necessary to refocus the laser beam, since the depth of field is not sufficient to make the notch sections (perforation). ) with the required precision.

The object of the invention is to create a method which, with little expense, allows a notch section to be prepared from a notch to be divided by fracture. Furthermore, it is an object of the invention to create a work piece produced according to this method and a laser unit to carry out the method.

This problem is solved by a method having the combination of features of claim 1, by means of a workpiece having the characteristics of subordinate claim 12 and a laser unit having the features of claim 14.

In the method according to the invention - in a similar manner as in conventional procedures - a laser notch is formed by laser energy, this notch having a multitude of notch sections. According to the invention, the type of laser, the pulse repetition rate, the material of the workpiece and the average laser power are mutually adapted so that the distance of the notch sections is substantially greater than that distance Notch that results by computation of the forward speed, relative motion and pulse repetition rate (frequency) of the laser.

A coupling of the laser beam preferably takes place obliquely to the longitudinal axis of the groove.

Surprisingly it was found that by choosing the above criteria appropriately it is possible to produce a notch provided with a bore even with a very high pulse repetition rate and fast forward, being that this notch distance is then substantially larger than the notch distance obtained by computation. This way of proceeding combines the advantage that it is possible to use a high frequency laser with a very high feed speed, so that the formation of the laser notch can be carried out substantially faster and with less introduction of heat than with conventional solutions. .

In a particularly preferred variant of the method, the speed of advance varies during laser machining, so that a notch is formed with notch sections of different depth. The "depth" of the notch section is the depth of penetration in the direction of the laser beam. Additionally, by varying the forward speed it is possible to vary the depth of a continuous zone, which is then called the base of the notch. Such a notch has an improved notch effective value once again and consequently an improved fracture mechanics.

In accordance with the invention, it is preferred that the variation of the forward speed be effected according to a periodic function, for example a sinusoidal function or as a function of the geometry of the component.

The speed of advance during laser machining can vary between 100 mm / min and 1500 mm / min.

In the valid claim 1 it is claimed that the machining parameters and the type of laser are selected so that a notch distance greater than the computed notch distance is set. The applicant reserves the right to further pursue an independent claim, for example within the aspect of a partial request, with which the variation of the forward speed during laser machining is claimed regardless of the choice of machining parameters and of the type of laser. That is, then an independent claim of this type would be directed to the laser machining of a notch to divide by fracture with variable feed rate (characteristics of claim 3 without reference to claim 1).

The laser beam can move in front of the stationary workpiece, but in kinematic reversal it is also possible to move the workpiece in front of the stationary laser, mixed forms are also favorable. The laser beam can be coupled radially, that is to say perpendicular to the notch to divide by fracture or inclined with respect to the notch to divide by fracture.

Accordingly, in a radial coupling the notch sections are perpendicular to the notch axis, while with an inclined coupling they are placed obliquely with respect to the notch axis. The coupling preferably takes place at an angle of < 45 ° (relative to the plane perpendicular to the longitudinal axis of the notch (in a connecting rod this is the radial plane of the connecting rod eye)). In a horizontally supported connecting rod and advancing direction (notch axis) that extends perpendicular to this the angle would therefore be for example 30 ° with respect to the horizontal and 60 ° with respect to the perpendicular (see figure 11).

In a variant of the invention, the actual notch distance that is adjusted by virtue of the choice of parameters is greater than 10 times the computed notch distance, which results from the pulse repetition rate and the forward speed.

With a suitable choice it is even possible to obtain a greater notch distance by 50 times.

In accordance with the invention it is preferred that a laser is used as a fiber laser. These fiber lasers are known from the state of the art, so detailed descriptions of the structure can be dispensed with.

In a variant of the invention, a laser with an average power lower than 50 Watts and a pulse repetition rate substantially higher than 1 KHz, preferably higher than 10 KHz, is used, being that the advance can be found in more than 1000 mm / min. In comparison with this, the pulse repetition rate in conventional processes is approximately in the same order of magnitude, with the pulse frequency being notably longer, for example 50 to 140 Hz.

In a preferred embodiment of the invention, the notch sections extend out of a continuous notch base.

The workpiece produced according to the method can be for example a connecting rod or a crankcase or other workpiece in which it is necessary to divide a bearing eye or any other area by means of a process for splitting by fracture.

The workpiece produced according to the method can have notch sections with different depth by varying the speed of the laser advance. In this aspect it is particularly preferred that these variations are repeated periodically along the notch section.

A laser unit for carrying out the method has a laser module, a laser head to focus the laser beam emitted by way of the laser module on a workpiece to be machined, and an axis of effective advance in the direction of advance. This is controlled by a control unit so that the feed is periodically varied during laser machining.

A highly dynamic feed axis is preferred with which it is possible to carry out variations of the feed rate with an acceleration greater than 0.5 g, preferably in the range of 1 to 2 g. That is to say, the profiles of advance speed can be carried out in sinusoidal form with high precision, in the case threshold even almost rectangular.

The preferred exemplary embodiments of the invention are explained below in more detail by means of schematic figures. They show: Figure 1 a representation of the principle of a laser unit to produce a notch to divide by fracture in a large connecting rod eye; 2 shows a highly enlarged representation of a notch for dividing by fracture produced according to the method according to the invention; Figure 3 an analogous representation with laser power and / or repetition rate of different pulses; Figure 4 representation of notches to divide by fracture as a function of the advance; Figure 5 representations of notches to divide by fracture as a function of the average laser power; Figure 6 a diagram to clarify how a notch depth depends on an advance of the laser beam; Figure 7 a diagram for clarifying a modulation of the forward speed as a function of time; Figure 8 a diagram and an illustration to clarify the notch depth that is presented as a function of the average speed of advance with a modulation of the forward speed; Figure 9 illustrations of notches to divide by fracture under comparable conditions with and without modulation of the forward speed; Figure 10 a schematic representation of a laser unit that can be used in a laser method with modulation of the forward speed, and Figure 11 a representation of the principle of a laser head of the laser unit according to figure 10.

Figure 1 shows a sectional representation of an eye 1 of a large connecting rod that must be divided by means of division by fracture in a bearing means and a part of the connecting rod. The development of this dividing plane 2 by fracture is preset by two notches 4 to divide by diametrical fracture (in figure 1 only one is shown) which is preferably configured in the form of a perforation with a multitude of notch sections 6. As explained in the state of the art described at the beginning, after forming on the left and right wall of the connecting rod eye 1 of FIG. 1, the notches 4 for 1Q split by fracture, in the connecting rod eye is inserted a spreader chuck, and then, by spreading the spindle chuck and supporting the connecting rod eye properly, the bearing half separates from the part of the connecting rod, so the geometry of the Division plane by fracture that occurs simplifies the well-adjusted assembly of both parts by virtue of the crystal structure.

To configure the notch 4 to divide by fractureIn accordance with the invention, a fiber laser is used whose laser head 8 is shown schematically in FIG. 1. This type of fiber laser can in principle be solid-body laser pumped by diode, wherein a core of a fiber of glass constitutes the active medium. The solid-body laser radiation is introduced by means of a coupling in the fiber, in which then the real intensification of the laser takes place. The properties of the beam and the quality of the laser beam can be adjusted by the geometry of the fiber (glass fiber), so that the laser remains largely unaffected by external influences and has a very simple structure.

After the exit of the mentioned active fiber, the laser beam is introduced into a fiberglass through which the radiation is then led to the laser head 8 illustrated in FIG. 1 and via its focusing optics 10 directs on the work piece 1 that must be machined. In the exemplary embodiment shown, a laser beam 12 impacts in the radial direction, ie, perpendicular to the notch axis (the vertical in Figure 1). This arrangement can have the advantage that the focusing optics 10 gets dirty by the material that is melted, because by virtue of the 90 ° coupling, the reflections and possibly residual casting return directly via the laser. If the coupling is made obliquely, for example with 30 ° or 45 °, the reflections and foundry residues that eventually occur are separated with the angle of reflection (see figure 1: 12""), so that it does not have place a soiling A laser unit with oblique coupling is described by figures 10 and 11.

A further disadvantage of the 90 ° coupling is that a delayed or penetrating beam guide is not possible. With a tilted position it is possible to further influence the geometry of the notch by a delayed beam guide (upwards in figure 11) or penetrating (downwards in figure 11). In the geometry of the notch, the flow of air that falls on the iron through the nozzle can flow additionally. Also on these two aspects mentioned above can be directed a subordinate claim.

These fiber lasers are characterized by very good electrical-optical effectiveness and excellent beam quality with a large depth of field with a very compact construction, so that with little construction space it is possible to create more economical solutions than with lasers conventional By virtue of the high peak power and the good focusing ability of the fiber lasers, the power density is relatively high, so that the portion of the evaporated material is predominant. But because a part of the energy is transformed into heat, there is still a melting and thermal influence of the environment. It is possible for the residual heat to accumulate, so that marked melting phenomena are obtained which can lead to the computed notch distance being noticeably less than the notch distance that actually occurs, and that this notch distance is also comparatively stable with the variation of the other parameters.

After machining the connecting rod wall on the left in FIG. 1, the laser head is rotated through 180 ° and the right connecting rod wall is processed. But in principle it is also possible to use cross heads with which both wall sections are machined simultaneously.

In the exemplary embodiment described, the workpiece, ie the connecting rod is firmly clamped and the laser head 8 moves in the axial direction or parallel to the axis with a forward speed V, in which the laser power is located at approximately 50 W and the pulse frequency of the laser at approximately 20 KHz in the exemplary embodiment shown. The point diameter is approximately 30 μp ?, the advance V is approximately 1500 mm / min. With these parameters, a notch distance of approximately 0.00125 mm would be computed. Actually the notch distance K is located (here with laser beam coupled with 45 ° inclination) by approximately 0.1 mm.

Figure 2 shows a highly amplified representation of a rod eye machined according to the method according to the invention with the parameters mentioned above, being that in this exemplary embodiment the laser beam is obliquely coupled (45 °). The average laser power is approximately 50 W and the pulse power is approximately 8 kW. The distance K of the perforation (notch distance) is approximately 0.1 mm, resulting in a continuous notch bottom (G) from which the individual notch sections 6 forming the perforation extend outwardly. The depth of the notch bottom G is approximately 0.51 mm in the exemplary embodiment according to Figure 2, while the depth P (viewed in the radial direction) of the notch sections 6 is approximately 0.78 mm (measured from the peripheral wall 14 of connecting rod eye 1).

Figure 3 shows a similar exemplary embodiment with reduced laser power (40), and less inclined coupling (30 °) of the laser beam 12 - it can be seen that there is no substantial change in the notch distance K, with the less inclined coupling and the lower laser power (40) the depth G of the notch bottom and the depth P of the notch sections are slightly larger. Consequently, with the coupling a little less inclined it is possible with even less power than in the exemplary embodiment described above to form a notch that improves the fracture behavior.

Figure 4 shows how the notch to divide by fracture depends on the forward speed V (see figure 1) adjusted with which the laser beam moves in the longitudinal direction of the notch.

It is clear that with different feed speeds (500 mm / min, 1000 mm / min, 1500 mm / min) the notch distance hardly changes. However, it is clear that with lower feed speeds on the one hand the depth G of the notch bottom is greater and also the axial length of the notch sections (PG) behaves inversely proportional to the feedrate, with the differences between 500 mm / min and 1000 mm / min are comparatively minimal.

Figure 5 shows how the notch to split by fracture depends on the power of the laser. In figure 5 in the upper part an average laser power of 50 W was adjusted. The notch to divide by fracture illustrated below results in an average laser power of 100, the other parameters remain unchanged. It is clearly seen that with less laser power a slightly thinner notch structure is formed with longer notch sections, although the notch distance, as already indicated above, hardly changes. With the lowest laser power, a continuous notch bottom with a depth G a little lower than with a higher laser power is also formed - as expected. Therefore, in relation to fracture mechanics, the use of a laser with comparatively low laser power (50 W and less) with an average speed of advance in the range between 500 and 1500 mm / min should be optimal.

The quality of the beam can be improved by what is called a switch Q. A switch Q of this type is an element of optical construction with which in a pulsed laser the impulse is delayed, the duration of the pulse is reduced and the impulse height (peak power), so that a very sharp laser pulse is obtained that rises quickly and after reaching an acute maximum, it decays again quickly. If a switch Q of this type the pulse is set notably wider and flatter.

Figure 6 shows how the notch depth that results depends on the feedrate that varies between 100 and 3000 mm / min. The measurement S2 corresponds to the measure G previously described (depth of the notch base) and the measurement SI to the total depth P (see figures 2 and 3) of the notch, so that the length of the notch sections corresponds to the difference (GP). The upper curve shows the development of the total depth SI of the notch, while the lower curve reproduces the depth development of the notch base S2. It is clearly seen that with comparatively low feed rates in the range of up to about 800 mm / min, the notch depth (SI, S2) depends comparatively on the feed rate. In the case of higher feed speeds (approximately 800-3000 mm / min) this dependence is notably less pronounced. These tests were carried out with a pulse frequency of 50 kHz and an average pulse power of 50 W. As the notch geometry of the forward speed that was explained by the figures described above depends, it is therefore confirmed by the tests that are reproduced in figure 6.

As will be explained in more detail below, with very low feed rates (less than 200 mm / min) it was found that the notch quality is insufficient due to thermal overheating in the notch bottom region. Carbonized areas were produced that rendered the laser-machined workpiece virtually useless. These carbonized zones are exemplified above in Figure 9, which will be discussed in detail below.

Therefore, in laser machining, care must be taken that the speed of advance is controlled so that these quality losses are avoided by forming the notch to divide by fracture.

It was found that this type of phenomena can be avoided by a variation of the speed of advancement during the laser machining, being then that a notch is produced to divide by fracture that on the one hand has a sufficient depth of notch and on the other hand it can form with high advance speeds and therefore in a short time, being that quality losses are not to be expected that result in a wofracture mechanics.

Figure 7 shows examples for a modulation of the speed of advance, being that this is carried out according to a sinusoidal function. Naturally, the speed modulation can also be carried out according to other functions, preferably periodic. It shows the development of the speeds of advance as a function of time within a certain advance zone that does not correspond to the total length of the notch to divide by fracture that must be configured. In particular, the advance zone between 67.5 and 69.5 mm is shown here, that is, only 2 mm of the whole notch are represented to divide by invoice, but nevertheless the speed modulation in the areas not represented of the notch to divide by fracture it is carried out analogously. The curves that are shown slightly wavy from top left to bottom right (top curve to dashes / bottom curve to continuous line) show the actual advance in the direction of the notch to divide by fracture as a function of time t. During this slightly wavy advance the speed of advance is varied according to the sine wave functions drawn, being that the sinusoidal function with a greater amplitude is associated to the striped laser curve, while the sinusoidal function with smaller amplitude is associated to the continuous laser motion curve. It can be recognized that the speed of advance is modified with relatively high frequency, so that it is necessary to accelerate and strongly brake the laser head 8 within a short time to adjust the profile of movement along the notch to divide by fracture that should be formed.

In the graph according to figure 7, the real values of the advance speed in each case are shown on the right. According to this, in the speed modulation that is above the speed was varied in the range between 117 and 1157 mm / min. In the formation of the notch to divide by fracture with a speed modulation, this results in a geometry of the notches to be divided by fracture, as shown in figures 8 and 9. Figure 8 shows a diagram in which the depth The notch that is presented is adjusted according to the average advance Vra, that is to say the average value of the velocity modulation described above. In figure 8 it can be seen that for example with an average advance speed of 800 mm / min (in fact the advance speed varies according to the sinusoidal function according to figure 7) a notch is presented to divide by fracture with the overprinted extension in figure 8. It is clearly seen that from a notch base with the measurement S2 (G) different notch sections are formed according to the sinusoidal period. Sections that are characterized by S3 are formed in areas where the forward speed is comparatively low. The notch sections characterized with SI are formed in the areas where the laser speed moves with a comparatively high speed.

The development of the SI (G), S2, S3 (P) magnitudes as a function of the average advance is represented in the diagram according to Figure 8. The curve above reproduces the development of the depth (S3) of Total notch with low forward speed, the SI curve the development of notch depth with comparatively high forward speed (always during speed modulation) and curve S2 the depth development of the notch base. It is appreciated that the notch depth decreases with the increase of the average advance speed. However, it is clearly visible that with the corresponding velocity modulation it is possible to form notch sections with variable groove depths. It was found that a notch of this type has a remarkably improved fracture mechanics compared to the notches mentioned at the beginning. In other words, by modulating the forward speed, it is possible to form comparatively deep and sharp initial notches that notably improve the initial tear toughness and the tear toughness of arrest compared to notches to divide by continuous drilling fracture without the modulation of the forward speed.

By means of this it is possible to fracture also complex components, being that the modulation of the advance speed can also be carried out depending on the geometry of the component. That is, in very complex components that have for example gaps in the area of the notch to divide by fracture it is possible to adapt the speed of advance to the geometry of the component so that in the non-problematic areas it is possible to work with a forward speed or amplitude of the modulation of the comparatively high forward speed, while in the most critical areas the modulation of the speed is correspondingly withdrawn so that a low average advance speed or also a constant forward speed is adjusted.

The advantage of the modulation of the forward speed described is clarified by FIG. 9. It illustrates above a notch to divide by fracture as would be presented with a comparatively low constant feed rate of 200 mm / min. The comparatively large depth of the notch and the burns / carbonisations that can be produced by virtue of the high introduction of heat with low forward speed are clearly seen. A notch to divide by fracture of this type is practically unusable.

On the other hand, in the figure 9 below a notch produced according to the method according to the invention is shown with modulation of the advance speed, being that the modulation of the advance speed was carried out in the range between 117 and 1157 mm / min. . It is clearly seen that by means of this modulation it is possible to reliably avoid burns in the area of the notch base. In addition, notch sections with greater or lesser depth configured by means of the respective speed modulation are identified, being that the depth also depends on the angle of laser placement. In the exemplary embodiments represented the placement angle, ie the coupling angle was approximately 30 ° relative to the horizontal in Figure 9.

By means of FIGS. 10 and 11 a laser unit is described which is particularly well suited for carrying out the method described above with modulation of the forward speed. According to FIG. 10, the laser unit has a laser module 16 containing, for example, a fiber laser and the control of this fiber laser. The control of the laser unit 16 is designed so that the forward speed of the laser beam can be modulated in the manner described above.

The laser beam 12 produced by the laser module 16 is guided via light conductors 18 to a recolimator 20 which in FIG. 10 is only sketched. In this the laser beam is transformed into a parallel beam, being that the diameter of ray is in the interval of approximately 6 mm. This parallel beam is then led by light conductors 18 to the laser head 8, by which a laser beam is then directed onto the workpiece to be machined, in the present case a connecting rod eye 1 of a connecting rod. The focused laser beam is coupled at an angle of 30 ° to the horizontal in FIG. 10. The laser head 8 is made with an axis Z of feed Z, via which the feed on the longitudinal axis of the feed takes place. notch. This axis of advance is realized as a highly dynamic axis with which extremely high accelerations can be carried out with a high circular increase and a great start, so that an extremely precise control of the modulation is required. Accelerations can be found, for example, in the range between 1 to 2 g, the circular increase in the range of 10 n / min / mm (166.71 / s) and a start higher than 400 m / s3. For bilateral machining of the connecting rod eye 1, the laser head 8 is furthermore provided with a turning shaft 24 through which the laser head 8 can pivot about the feed axis Z. The laser unit still has a regulation axis X, in which it is possible to move the entire laser head 8 in the X direction (radial relative to the connecting rod eye 1). With a device of this type it is also possible to form notches to be divided by sinusoidal fracture.

Figure 11 shows the structure in principle of the conduction of the beam in the laser head 8. The light conductor 18 coupled to the fiber laser (laser module 16) is represented. The laser beam is transformed into the recolimator 20 in a parallel beam with a diameter of about 6 mm, and then deflected via a reflector mirror 28 through 90 ° towards the axis of the connecting rod eye. The reflected laser beam 12 is then focused on the connecting rod wall by means of an optics with a focal length of, for example, 100 mm, the alignment to the peripheral wall of the connecting rod being effected by means of another reflector mirror 32, which in the exemplary embodiment represented is placed at an angle of 60 ° with respect to the horizontal, so that the resulting laser beam strikes the peripheral wall of the connecting rod with a coupling angle of 30 ° with respect to the horizontal or a angle of incidence of 60 ° with respect to the perpendicular part of the laser beam 12 incident on the reflector mirror 32 (deviation of 60 °). The laser beam emerges via a nozzle 34, and is focused so that the laser point is approximately 3 mm in front of the outlet plane of the nozzle 34. To avoid fouling of the optics 30 and the mirrors 28, 32 , in the course of the beam between the nozzle 34 and the reflecting mirror 32, a protective glass 34 is provided. In the illustration according to FIG. 11, the axis of rotation 24 is also identified, the laser head 8 is mounted rotatably on the bearing via a bearing 38 and can be swiveled about the axis Z of feed Z by means of a motor (not shown). so that it is practically possible to reach any peripheral wall area of the connecting rod.

With the use of a fiber laser and by the suitable choice of a modulation of the forward speed and a comparatively high pulse repetition rate (as compared to conventional solutions) it is therefore possible to form a perforation having a value of optimum notch effectiveness, but which nevertheless can be formed with substantially less energy input and with speeds of advance considerably faster than what is possible with conventional systems.

The tests carried out show that for example with a fiber laser having a power of 50 Watts with a pulse frequency of 20 kHz it is possible to form a notch 4 to divide by fracture in which the notch sections have a distance in the interval of 1/10 of a mm, preferably in the range of 0.1 to 0.3 mm. It was found that even using a laser having a power of only 30 Watts it is possible to form a perforated notch 4 to divide by highly effective fracture.

A method for dividing by fracture work pieces and a work piece produced according to this method is described. In accordance with the invention, for example, the type of laser, the pulse repetition rate, the duration of the pulses, the material of the workpiece and / or the laser power are chosen so that the distance of the sections of The notch is substantially larger than the notch distance that would result by computation of the forward speed of the laser beam and / or the workpiece and the pulse repetition rate of the laser. The described feed modulation also allows the formation of oblique laser notches for running surfaces, such as spherical or roller guides.

In accordance with the invention it is further described that the feed rate is modulated according to the geometry of the workpiece and / or periodically during laser machining.

List of reference symbols 1 Connecting eye 2 Fracture plane 4 Notch to divide by fracture 6 notch sections 8 Laser head 10 Focus optics 12 Laser beam 14 Peripheral wall 16 Laser module 18 Light conductor 20 Recolimator 22 Axis of advance 24 Spindle 26 Regulation axis 28 Reflector mirror 30 Optics 32 Reflector mirror 34 Mouthpiece 36 Protective glass 38 Bearing It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention.

Claims (15)

CLAIMS Having described the invention as above, the content of the following claims is claimed as property:

1. Method for splitting workpieces by means of laser energy, with the relative displacement between a laser beam and the workpiece forming a notch to be divided by fracture that determines the plane of division by fracture. It is configured in the form of a perforation with notch sections, characterized in that the machining parameters, for example the type of laser, the pulse repetition rate, the duration of the pulse, the material of the workpiece and the laser power are selected so that the distance of the notch sections is substantially greater than the notch distance results by computing the forward speed of the laser beam and / or the workpiece and the pulse repetition rate.

2. Method according to claim 1, characterized in that the laser beam is coupled obliquely to the longitudinal axis of the groove.

3. Method according to any of claims 1 or 2, characterized in that the feed rate is varied during machining.

4. Method according to claim 3, characterized in that the speed of advance varies according to a periodic function, for example a sinusoidal function.

5. Method according to any of claims 3 or 4, characterized in that the advance speed varies between 100 mm / min and 1500 mm / min.

6. Method according to any of the preceding claims, characterized in that the real notch distance is in each case 10 times greater than the computed notch distance.

7. Method according to claim 6, characterized in that the mixing distance is greater by more than 50 times than the notch distance computed.

8. Method according to any of the preceding claims, characterized in that a fiber laser is used as a laser.

9. Method according to any of the preceding claims, characterized in that the average power of the laser is 50 Watts and less with a pulse repetition rate higher than 1 KHz, preferably higher than 10 KHz.

10. Method according to any of the preceding claims, characterized in that the coupling angle is approximately 30 °.

11. Method according to any of the preceding claims, characterized in that the notch for dividing by fracture has a continuous mixing base out of which the notch sections extend.

12. Workpiece, in particular a connecting rod or a crankcase, characterized in that it is produced according to a method according to any of claims 1 to 11.

13. Workpiece according to claim 12, characterized in that it has sequences that are repeated periodically from one or several notch sections with a shallow depth and one or more indentation sections with greater depth or depending on the geometry of the workpiece. different depths of notch.

14. Laser unit for carrying out the method according to any of claims 1 to 11, characterized in that it comprises a laser, a laser head for focusing a laser beam on the workpiece to be machined, with at least one axis of advance acting in the direction of advance and with a control unit to vary the forward speed during laser machining.

15. Laser unit according to claim 14, characterized in that the advance axis is designed in such a way that variations in the forward speed are possible with an acceleration > 0.5g, preferably up to 2g.