WO2019001847A1 - LASER BEAM CUTTING - Google Patents

Abstract

Shown is a laser beam cutting system (10). The laser beam cutting system (10) comprises a first focusing optics (16), which is adapted to focus laser radiation on points on a first space curve 26a and a second focusing optics (16), which is adapted to laser radiation on points on a second space curve (26b ), wherein the laser beam cutting system (10) is arranged to perform a routine to ensure a desired overlap of the space curves (26a), (26b). The laser beam cutting system (10) is further configured to monitor, during the routine, focusing laser radiation at one or more of the points on the first space curve (26a) and focusing laser radiation at one or more points on the second space line (26b) the desired overlap of the space curves (26a), (26b) can not be confirmed to determine data regarding an offset between the space curves (26a), (26b).

Description

 LASER BEAM CUTTING

TERRITORY

The present invention relates to methods and systems for laser beam cutting. In particular, the present invention relates to methods and systems for separating fiber reinforced plastics, such as carbon fiber reinforced plastics.

BACKGROUND

Fiber reinforced plastics are composites in which fibers in a plastic matrix, eg. Epoxy resin, are embedded. The matrix material serves to connect the fibers and to fill the intermediate spaces.

For separating fiber reinforced plastics milling machines are typically used. However, due to the heterogeneity of the material, difficulties in the application of force and wear often occur in the mechanical processing of fiber-reinforced plastics.

SUMMARY

When separating workpieces from fiber-reinforced plastics by means of pulsed laser radiation (eg. With pulse lengths in the nano-, pico- or femtosecond) these difficulties can be avoided and (with correspondingly small spatial extent of the forming heat affected zone) high quality machining results can be achieved. However, the use of pulsed laser radiation for separating fiber-reinforced plastics, in particular in mass production, often fails because of the low effective cutting speeds of the available systems.

It is therefore the object of the present invention to provide laser beam cutting methods and systems that improve the economics of using pulsed laser radiation to separate fiber reinforced plastics, especially in series production, improve. This object is achieved by the coordinated, simultaneous processing of fiber-reinforced plastic with a variety of laser beams, with a (virtually) web-free transition between the cutting segments is made possible by a precise setting / calibrating the laser beam guidance in the overlapping areas.

An inventive method for separating a fiber-reinforced plastic by means of pulsed laser radiation comprises applying a laser radiation to a surface by focusing laser radiation on one or more points on a first space curve and by focusing laser radiation on one or more points on a second space curve Determining an overlap or relative positional relationship of the first space curve and the second space curve by detecting surface areas which are exposed to laser radiation, shifting and / or twisting the first space curve and / or the second space curve to reduce an offset when a desired overlap or Relative positional relationship of the space curves can not be confirmed, and separating the fiber reinforced plastic by focusing pulsed laser radiation on points on the first space curve and by focusing pulsed laser radiation on points on the z wide space curve.

In this context, the term "separating" as used in the specification and claims is to be understood as meaning, in particular, the melting / evaporating / burning / sublimation / decomposition of material along the space curves, whereby the fiber-reinforced plastic along the The severance can be carried out by single or multiple (repeated) ablation along the spatial curves Furthermore, the term "overlap", as used in the description and the claims, in particular a measure of the agreement between the space curves to understand. Furthermore, the term "offset" as used in the description and the claims, in particular a measure of the deviation between the To understand space curves. In addition, in the description and the claims under "capture" in particular a monitoring and deriving observation data from the observation to understand.

By the method according to the invention can thus be ensured that an offset of the focused laser radiation in the overlapping areas of the cutting segments is reduced or kept below a threshold / within a tolerance range.

Preferably, when applying the surface with laser radiation for determining the overlap, laser radiation is used with a lower intensity than laser beam cutting.

For example. For example, the surface can be exposed to laser radiation which does not produce any or only slight irreversible changes in the material, which can prevent the generation of rejects. Likewise, during a production process, for example, the method can be carried out for each workpiece to be machined or for a specified number of workpieces in order, for example, to detect and compensate for an increase in the offset in good time.

Preferably, the surface areas are detected by means of a camera.

In this context, the term "camera", as used in the description and claims, in particular to understand a device with an image sensor for receiving electromagnetic radiation wherein the image sensor, for example, be designed as a CCD or CMOS sensor For example, the camera can be designed as a thermal camera.

Preferably, the camera detects electromagnetic radiation in the visible or infrared spectrum and / or on the surface of reflected laser radiation. For example. can be derived from the electromagnetic radiation points or curves that describe the impact of the laser radiation on the surface. By comparing the points or curves with each other or with markers on the surface can then be concluded on an overlap of the space curves or the leadership of the laser radiation can be corrected.

Preferably, focusing pulsed laser radiation at points on the first space curve comprises deflecting a laser beam from a first laser beam source and focusing pulsed laser radiation at points on the second space curve deflecting a laser beam from a second laser beam source.

For example. For example, the laser radiation can be generated by a first stationary laser device and a second stationary laser device which can deflect laser radiation into different spatial directions by means of deflection optics. A deflection optics may, for example, comprise a rotatable or pivotable mirror or another rotatable or pivotable optical element, such as, for example, prisms or acousto-optic or electro-optical deflectors.

An inventive laser beam cutting system comprises a first focusing optics, which is adapted to focus laser radiation on points on a first space curve and a second focusing optics, which is adapted to focus laser radiation on points on a second space curve, wherein the laser beam cutting system is set up to perform a routine to ensure a desired overlap of the space curves, wherein the laser beam cutting system is configured to focus laser radiation onto one or more of the points on the first space curve and focus laser radiation to one or more points on the second space curve during the routine and if the desired overlap of the space curves can not be confirmed, to determine data regarding an offset between the space curves. In this context, the term "focusing optics", as used in the description and the claims, also means a device that allows to set the focus of the laser radiation along the beam path, such as. A focusing lens, the is slidably mounted along the beam path.

Preferably, the laser beam cutting system comprises a receptacle for a workpiece and a camera.

Preferably, the camera is adapted to detect electromagnetic radiation in the visible or infrared spectrum and / or reflected laser radiation.

Preferably, the laser beam cutting system comprises a first laser radiation source, adapted for generating pulsed laser radiation, which is associated with the first focusing optics and a second laser radiation source, adapted for generating pulsed laser radiation, which is associated with the second focusing optics.

Preferably, the laser beam cutting system comprises a first deflection optics, which is associated with the first laser radiation source, wherein the first deflection optics makes it possible to deflect laser radiation generated by the first laser radiation source in different spatial directions and a second deflection optics, which is associated with the second laser radiation source, the second Deflection optics makes it possible to deflect laser radiation generated by the second laser radiation source in different spatial directions.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is explained below in the detailed description with reference to exemplary embodiments, reference being made to drawings in which:

Fig. 1 is a schematic plan view of an exemplary laser beam cutting system, which comprises a plurality of parallel operable laser sources and scan heads, the scan heads (in pairs) having overlapping work areas;

FIG. 2 is a flow chart of a method for calibrating the alignment of the scan heads of the system shown in FIG. 1; FIG.

FIG. 3 is a schematic plan view of a variant of the laser beam cutting system shown in FIG. 1; FIG. and

4 shows a schematic plan view of a further variant of the laser beam cutting system shown in FIG.

In the drawings, the same or analogous elements are identified by the same reference numerals.

DETAILED DESCRIPTION

Fig. 1 shows a schematic plan view of an exemplary laser beam cutting system 10. The laser beam cutting system 10 includes a plurality of stationary laser devices 12, which are rigidly attached to, for example, a frame of the laser beam cutting system 10. The stationary laser devices 12 each comprise a laser radiation source 14 (eg a pulsed fiber laser with a power range up to 100 watts) and a scan head with a focusing optics 16 and a deflection optics 18. The deflection optics 18 allow a deflection of the beam path of the laser radiation in different spatial directions.

The focusing optics 16 or elements of the focusing optics 16 can be arranged rigidly along the beam path (for example, relative to the laser radiation source 14) or movably mounted. With movable storage, the distance between the laser radiation source 14 and the focal point of the laser radiation can be varied. The focus can then be placed three-dimensionally in space despite fixed laser radiation source 14 (within certain limits). In this way, the focus of the laser radiation can be guided along curved component surfaces, whereby at correspondingly strong curved areas of component surfaces unacceptable defocusing can be avoided.

The scanning heads of the stationary laser devices 12 are aligned or aligned so that the laser radiation of the laser radiation sources 14 each covers a work area 20, with working areas 20 overlap in pairs. Alternatively, the laser radiation sources 14 can be arranged in (for example by means of a plurality of robot arms) movable laser devices (not shown), which enable the laser radiation to be aligned in pairs overlapping working areas 20.

The laser beam cutting system 10 further includes a receptacle wherein, as shown in Fig. 1, during operation, a workpiece 22 of fiber reinforced plastic (eg, carbon fiber reinforced plastic) may be disposed to be severed along a desired cutting line 24. The laser devices 12 are arranged or movable relative to the cutting line 24 so that the cutting line 24 passes through the overlapping working areas 20.

Thereby, the laser devices 12 can cut the workpiece 22 in the context of a coordinated operation, which may include in particular a parallel operation of the laser devices 12, along the respective segments of the cutting line 24, which lie in the respective working areas 20 of the corresponding laser devices 12. The severing of the workpiece 22 can take place, for example, by layer-like removal of material of the workpiece 22 along the segments.

The operation of the laser devices 12 may be coordinated by control commands that cause the laser devices 12 to focus laser radiation along space curves 26a, 26b that are within their working areas 20. The space curves 26a, 26b result from the position and orientation of the respective laser device 12 and the calibration of the scan heads, which deflect the laser radiation in different spatial directions or focus the laser radiation. The control commands may be calculated from a measured or assumed position and orientation of the workpiece 22 and data relating to the cutting line 24, taking into account measured or assumed positions and orientations of the laser devices 12 and calibration data of the scan heads. The aim of the calculation may be that the space curves 26a, 26b resulting from the control commands coincide with the cutting line 24 and overlap each other.

However, as shown in the enlarged section in FIG. 1, due to measurement inaccuracies, tolerances, etc., it may happen that the space curves 26a, 26b resulting from the control commands do not overlap or overlap sufficiently deviate desired cutting line 24. If the laser devices 12 were controlled in this situation on the basis of the control commands, it could happen that the machining quality does not meet the requirements placed on them and the workpiece 22 has to be disposed of as scrap.

To prevent this, the laser beam cutting system 10 may be configured to determine data regarding the space curves 26a, 26b resulting from the control commands and, if necessary, to correct the position, orientation, or calibration of the scan heads, as shown in the flow chart of FIG 2. For this purpose, the laser beam cutting system 10, for example, as in step 28 of the method shown in Fig. 2, the surface of the workpiece 22 to apply laser radiation.

The laser radiation may have a reduced intensity (as compared to the intensity of laser radiation upon separation) that locally heats the surface of the workpiece 22 without severing the workpiece 22 (or creating an irreversible change in the material of the workpiece 22). The heating of the workpiece 22 may then be recorded by an infrared camera (not shown) which detects the surface of the workpiece 22.

For example. For example, the laser devices 12 can successively focus laser radiation onto one or more points of the respective space curve 26a, 26b. By recording the heat regions forming by the energy input, it is possible to check whether the space curves 26a, 26b lie on the cutting line 24 and overlap (sufficiently) or whether a deviation in this respect is within a tolerance range, as in step 30 of FIG. 2 shown method.

If this is not the case, the position, orientation, control commands or the reference orientation of one or more of the scan heads can be adjusted, as in step 32 of the method shown in FIG. For example. For example, the heat ranges may be characterized by a midpoint (or centerline) and an extent, and from the midpoint (or centerline) a surface tangential deviation of the respective space curve 26a, 26b from the cutting line 24, and from expansion a surface perpendicular deviation of the respective space curve 26a , 26b are determined by the cutting line 24.

Furthermore, it can be checked whether the adjusted control commands or the one or more corrected reference orientations of the scan heads lead to corrected space curves 26a ', 26b' (which correspond to a displacement and / or rotation of the space curves 26a, 26b). that lie on the cutting line 24 and (sufficiently) overlap, or whether a related deviation is within the tolerance range. If this is not the case, one or more new fixes can be performed until either the requirements are met or the procedure ends with an error message. This can occur, for example, when the control of one or more laser devices 12 is defective.

Further, the correction can be made on the basis of taking on the heat radiation on the basis of surface-reflected laser radiation instead of. The laser radiation may be laser radiation of the laser radiation sources 14 (with possibly reduced intensity in comparison to the intensity during separation) or further laser radiation sources (such as, for example, a pilot laser, not shown), which by the scan heads on the surface of the Workpiece 22 is deflected. In this case, instead of infrared radiation, electromagnetic radiation in the frequency range of the laser radiation and / or laser radiation in the visible range can be detected, wherein the reflection ranges can be characterized analogously to the thermal ranges by a center point (or a center line) and an extension.

Also, the described monitoring of the space curves 26a, 26b may also be performed continuously during the cutting of workpieces 22, wherein the control commands / one or more reference orientations of the scan heads are continuously corrected / adjusted to a deterioration of the cut quality during operation , for example, due to fluctuating temperature influences, to prevent / reduce.

Fig. 3 shows a schematic plan view of another exemplary laser beam cutting system 10 'which differs from the laser beam cutting system 10 shown in Fig. 1 in that the surface of the workpiece 22' has a mark detected by the laser beam cutting system 10 ' becomes. The marking makes it possible to more accurately determine a deviation of the space curves 26a, 26b from the cutting line 24. For example. For example, the laser beam cutting system 10 'may be provided with data indicating, in addition to characterizing the cutting line 24, how the cutting line 24 extends relative to the marks, whereby the space curves 26a, 26b may be corrected based on the marks.

Fig. 4 shows a schematic top view of another exemplary laser beam cutting system 10 ", which differs from the laser beam cutting system 10 shown in Fig. 1 in that the overlapping work areas 20 form a closed working area 4 may also be adapted to use a mark on the workpiece for correcting the space curves 26a, 26b, like the laser beam cutting system 10 'shown in FIG. Further, it will be understood that instead of the three or four laser devices 12 shown, a laser beam cutting system according to the invention may also be more than ten, more than twenty, more than thirty, more than forty, more than fifty, more than sixty, more than seventy , more than eighty, more than ninety, or more than one hundred laser devices 12 may include paired overlapping work areas 20 to increase a machining speed of the laser beam cutting system.

REFERENCE LIST, ιο ', 10 "laser cutting system

 laser device

 Laser radiation source

 focusing optics

 deflecting

 Workspace

 workpiece

 cutting line

a, 26b space curve

-32 process steps

Claims

A method of separating a fiber reinforced plastic by pulsed laser radiation comprising: Impinging (28) a surface with laser radiation, by focusing laser radiation onto one or more points on a first space curve (26a) and by focusing laser radiation onto one or more points on a second space curve (26b); Determining (30) an overlap or relative positional relationship of the first space curve and the second space curve by detecting surface areas which are exposed to laser radiation; Shifting (32) and / or twisting the first space curve and / or the second space curve to reduce an offset when a desired overlap or relative positional relationship of the space curves can not be confirmed; and Separating the fiber reinforced plastic by focusing pulsed laser radiation at points on the first space curve and focusing pulsed laser radiation at points on the second space curve. 2. The method of claim 1, wherein when the surface is exposed to laser radiation to determine the overlap or relative positional relationship, laser radiation is used with a lower intensity than when separating. 3. The method according to claim 1 or 2, wherein the surface areas are detected by means of a camera. 4. The method of claim 3, wherein the camera detects electromagnetic radiation in the visible or infrared spectrum and / or on the surface of reflected laser radiation. 5. The method of claim 1, wherein focusing pulsed laser radiation onto points on the first space curve comprises deflecting a laser beam of a first laser beam source and focusing pulsed laser radiation onto points on the second space curve to deflect a laser beam from a second laser beam source. A laser beam cutting system (10, 10 ', 10 ") comprising: first focusing optics (16) arranged to focus laser radiation onto dots on a first space curve (26a); and second focusing optics (16) therefor is arranged to focus laser radiation at points on a second space curve (26b), the laser beam cutting system (10, 10 ', 10 ") being arranged to perform a routine to ensure a desired overlap of the space curves (26a, 26b); wherein the laser beam cutting system (10, 10 ', 10 ") is arranged: during the routine, focusing laser radiation on one or more of the points on the first space curve (26a) and focusing laser radiation on one or more points on the second space curve ( 26b), and if the desired overlap of the space curves (26a, 26b) can not be confirmed to determine data concerning an offset between the space curves (26a, 26b). A laser beam cutting system (10, 10 ', 10 ") according to claim 6, comprising: a receptacle for a workpiece (22); and a camera. 8. laser beam cutting system (10, 10 ', 10 ") according to claim 7, wherein the camera is adapted to detect electromagnetic radiation in the visible or infrared spectrum and / or reflected laser radiation. A laser beam cutting system (10, 10 ', 10 ") according to any one of claims 6 to 8, comprising: a first laser radiation source (14) arranged to generate pulsed laser radiation associated with the first focusing optics (16) and a second laser radiation source (16); 14) arranged to generate pulsed laser radiation associated with the second focusing optics (16). 10. A laser beam cutting system (10, 10 ', 10'') according to any one of claims 6 to 9, comprising: a first deflection optics (18) associated with the first laser radiation source (14), the first deflection optics (18) enabling and deflecting a second deflecting optics (18) associated with the second laser radiation source (14), the second deflecting optics (18) making it possible for the second laser radiation source (14) to deflect from the second Laser radiation source (14) deflected laser radiation in different spatial directions.