DE4212390A1 - Laser engraving machine for print rollers - has beam guide for several laser beams to generate variable beam spot configuration on work surface - Google Patents

Abstract

The laser engraving equipment, having several laser beam sources (10-16) with individual light transmission (18, 22; 20, 24) and beam guide (26, 28) systems, to generate a variable beam spot configuration on the work surface. The beam spot configuration can be varied by the beam guide system to overlap fully (A), partially (C,D) and/or lie in one or more rows (B). The laser beam intensity is individually variable.

Description

The invention relates to a laser engraving device with a Laser beam source of a laser light transmission path and a beam guidance system with which at least one Laser beam on a machining point of a workpiece is focusable.

There are different areas of application for such laser gra devices. Examples of this are the labeling of metallic or plastic workpieces Labeling purposes, the labeling of footage, the Manufacture of gravure rollers and the like. The present The present invention is intended specifically in connection with the manufacturer development of printing rollers are described, although by this the application of the invention in other technical fields is not excluded.

In the manufacture of printing rollers, the z. B. Art fabric, rubber or ceramic existing pressure roller - similar to clamped on two sides of a lathe, with con constant speed rotated around its longitudinal axis and from a laser apparatus to finish the surface the printing roller a relief pattern according to a template to lend.

A known system contains a laser beam source for this purpose, a light containing, for example, an optical fiber transmission path and a beam containing optics guidance system with which the laser beam hits the surface surface of the workpiece. While the pressure roller rotates, the beam guidance system becomes translational moved along the longitudinal axis of the workpiece. Thereby be the processing station writes down a spiral path  the surface of the platen. The intensity of the laser beam is controlled in accordance with signals which by scanning a template or using a computer be fathered.

The processing speed depends on the depth of the the surface of the workpiece to be engraved, the Total surface of the printing roller, the intensity of the laser rays, the pattern resolution and other factors, e.g. B. Material properties of the surface.

Should be relative by laser engraving at the processing point A lot of material has to be removed, so a lot has to be removed Energy is brought into the processing point. Is given a certain beam intensity, this determines Energy - also depending on the size of the processing spot - the speed at which the point of impact of the laser beam moves over the surface of the workpiece. There for technical reasons, the pressure roller is constant Must rotate speed and also the feed movement of the Beam guidance system parallel to the axis of rotation of the pressure roller is constant, the highest possible machining speed depends speed, i.e. speed of the roller and feed movement of the Laser system, for a given beam intensity depends on how a lot of material at the deepest point to be engraved to be worn.

The present invention is also and specifically to the production of printing rollers for gravure printing, however the special features of the invention are also applicable to others technical areas applicable. Especially in the manufacture printing rollers for gravure printing have been used up to now mechanical engraving devices are devices that several electromechanically deflectable fingers with triangular shape possess diamond tips. By controlled deflection the single finger over one under the fingers away  rotating pressure roller are in their example from be standing surfaces produced small depressions. This ha ben - depending on the relative speed between the Fingers and the platen - the shape of an elongated or short, compressed diamond. The working speed such mechanical engraving devices is approximately 5000 Hz.

The processing speed of this mechanical engraving devices can practically not be increased. The diamond tips are considerable despite their considerable hardness Subject to wear.

The invention has for its object a laser engraving device of the type mentioned above, with the Materials requiring high power densities in relative can be edited in a short time.

This object is achieved in that at least two laser beam sources are provided, and that the beam guidance system individual beam guidance has directions for the individual laser beams, with which the relative location of the individual points of impact Laser beams at the processing point is adjustable.

Through the individual beam guidance devices for the different laser beams can have different patterns generated at the processing point. To increase the Processing / engraving speed can not only be two, but also, for example, three or four laser beam sources be provided, preferably each individual laser beam source a special beam guiding device is arranged.  

The invention offers the possibility within a During this period, a significantly larger number of works to edit pieces. Individual laser beam sources stand especially from separate laser devices, basically however, it is also possible to use a single laser in conjunction with beam splitters to create multiple laser beams to obtain.

According to the invention, the beam guidance is now used systems set the points of impact in such a way that the processing point

• a) completely overlap, or
• b) partially overlap, and / or
• c) in one or more rows or columns next to each other the lie.

The intensities of the individual laser beams are in individually controllable.

One can now use an abundance of combinations of laser beams or provide points of impact at the processing point. For example, you can use all available laser beams merge in a single point overlapping. There with maximum energy can work on a small point be concentrated surface.

A partial overlap can also be provided so that For example, the outline of a shamrock or similar results. You can also use the impact points in this way against each other that one or more rows or Splitting impact points over the workpiece surface be performed. If now the individual laser beams indi vidually adjustable in intensity, so you can for example - depending on the template to be engraved pattern - a beam with a relatively low constant Let intensity hit while another beam or  several more rays are modulated in intensity.

If the template pattern allows, you can use the individual Laser beams side by side parallel to the axis of rotation of the Let the workpiece hit. This allows the machining multiply the speed. The control of the individual Laser beam sources are made - in principle as in the prior art Technology - program-controlled according to signals from a Template pattern, the signals for example by a optical scanning device can be obtained, or purely are digitally generated data.

In the known laser engraving device, the scanning takes place basically spiraling across the surface of the Pressure roller. With the help of the device according to the invention instead of spiral scanning, they are also attached to each other the adjacent circular path on the cylindrical surface of the workpiece can be scanned. For this, the individual Laser beams that are continuously along the axis of rotation the pressure roller moving laser device so nachge that leads to the cylindrical surface of the work piece circular path connects to circular path. On a transition can then z. B. by a sudden reset of the Beam guidance system of the laser beam on the subsequent Circular path to be moved laterally.

Exemplary embodiments of the invention are described below of the drawings explained. Show it:

Fig. 1 is a schematic front view of a laser engraving system,

Fig. 2 is a schematic cross-sectional view of a beam guiding device, of which several copies are present in the laser engraving system according to Fig. 1, and

Fig. 3 different patterns of impingement points of individual laser beams.

Fig. 4 is a plan view of another embodiment of a laser engraving device, and

Fig. 5 is a schematic sectional view taken along line VV in Fig. 4.

Fig. 1 shows a laser engraving device 2 , with which a gravure roller 4 is provided with a surface pattern of a plurality of small holes.

For this purpose, the pressure roller 4 is rotatably clamped in two bearings 6 and 8 , one of which has a rotary drive (not shown).

A laser device contains a first laser beam source 10 and a second laser beam source 12 , which give a laser beam Lx or Ly via an associated coupling optics 18 or 20 to an entry surface of an optical fiber light guide 22 or 24 .

Laser beams emerging from the exit surfaces of the optical fibers 22 and 24 strike out coupling and focusing optics 26 and 28 and are focused by this onto a processing point 30 on the surface of the printing roller 4 .

As indicated in Fig. 1, further laser beam sources 14 and 16 can be provided, which also focus on the processing point 30 via optical fibers and optical devices, not shown, laser beams.

The coupling-out and focusing optics 26 and 28 respectively contain the components of the laser device can be of a not shown longitudinal guide in the direction of arrow P trans translationally parallel to the rotational axis of the workpiece 4 bewe gene. Thus, the entire surface of the workpiece 4 by the laser beams, according to Fig. 1, the laser beams Lx and Ly, scanned. In other words: the processing point 30 moves over the entire processing area of the printing roller 4 .

As is known per se, the speed of the printing roller 4 and the speed of the translational movement of the laser device parallel to the axis of rotation of the workpiece 4 are each constant. The control of the laser beam sources 10 , 12 (and 14 and 16 ) is carried out by a computer as a function of a template, which z. B. is scanned by an optical scanning device in synchronism with the movement of the laser engraving device.

The Auskop Pel- and focusing optics 26 and 28 , which are only indicated schematically in FIG. 1, are part of a beam guiding system which has a beam guiding device individually for each individual laser beam.

Fig. 2 shows an example of a beam control device. In the case of four laser beam sources according to FIG. 1, a total of four such beam guiding devices are available.

The beam guiding device shown in FIG. 2 serves to position and focus the laser beam Lx emerging from the optical fiber 22 . The end of the optical fiber 22 is fixed by a lens holder 34 which carries the lens 26 in its bottom. On the outer side walls of the lens holder 34 there are two webs 36 and 38 which are able to slide in corresponding guide grooves of slide guides 40 and 42 . With the help of a drive device not shown here, the lens holder 34 in the slide guides 40 and 42 can be adjusted up and down according to arrow P1 to focus the beam Lx at the processing point 30 .

The outer surfaces of the two sliding guides 40 are spherical and are held by a bearing ring 44 equipped with a spherical bearing surface. So that the lens holder with the end of the optical fiber 22 and the lens 26 tilt from a (not shown) Kippvorrich device, as indicated by the arrow P2. This allows the point of incidence of the laser beam Lx to be adjusted in the plane E perpendicular to the plane of the drawing.

From FIG. 3 it can be seen how the impingement points x, y, z and w originating from four different laser beams can be configured by means of individual beam guiding devices of the type represented in FIG. 2.

According to Fig. 3 (A) the impact points are x, y, z and w by four laser beams completely overlapped with each other. The processing point 30 thus receives the intensity of all laser beams.

Fig. 3 (B) shows a pattern of impact points in which the individual impact points are located one below the other in a column. The direction of the relative movement between the beam guidance system and the workpiece is shown in Fig. 3 (B) z. B. from top to bottom.

Alternatively, the three points of impact could also be next to each other lie in a row. You can also get a pattern from quadra Provide table-top impact points.  

Fig. 3 (C) shows a "cloverleaf pattern" in which the four impact points (more precisely: impact spots) overlap in pairs.

Fig. 3 (D) shows another example of partially overlapping impact points.

Any other pattern is conceivable.

The intensity of the laser beams brought together in a specific pattern at a processing point 30 according to FIG. 3 can be individually controlled. For example, according to FIG. 3 (B), the laser beam Lx associated with the point of incidence x may have a constant intensity, while the intensity of the other laser beams may be modulated together or individually.

Fig. 4 shows a preferred further embodiment of a laser engraving device according to the invention.

The laser engraving device 102 shown in FIGS . 4 and 5 is designed as a laser head and, like the exemplary embodiment described above, is capable of a specific pattern of impingement points at a processing point 130 , e.g. B. to produce on the surface of a gravure roll.

The laser engraving device 102 shown in FIGS. 4 and 5 has a granite carrier 101 , on which a total of four laser beam sources 110 , 112 , 114 and 116 are arranged in pairs centrally adjacent to the outer longitudinal sides, the two middle laser beam sources 112 and 114 being one between them Form gap 115 .

The laser beam sources 110-116 emit laser beams Lx, Ly, Lz and Lw via an associated intensity switch (modulator) 151 to the associated deflection mirrors 152 , 153 , 154 and 156 , respectively. From these deflecting mirrors, the lasers pass to a further deflecting mirror block 156 , from where the beams in the form of a bundle of parallel lasers radiate partly in the gap 115 between the two laser beam sources 112 and 114 and partly above this gap 115 to a block 150 of individually adjustable Deflecting mirrors 150 a - 150 d.

Fig. 5 shows schematically the beam path. The laser beam goes from the individual laser beam sources into the drawing plane, which is indicated by the symbol "x". Of the individual deflecting mirrors 152-155, the Laserstrah go len to the deflector block 156 and are deflected by the latter in the direction of the drawing plane, as indicated by the symbol "." is indicated.

The individual laser beams Lx. . . . thus reach the ever weils these rays associated deflecting mirror 150 a, 150 b, 150 c and 150 d of the Ablenkspiegelblocks 150, which is shown for reasons of clarity in Fig. 4 in perspective.

The mirror surfaces of the individual deflecting mirrors 150 . . . can be individually adjusted within certain limits around two axes, so that the associated laser beams Lx. . . can be distracted within appropriate limits.

All laser beams pass through a deflection mirror 127 , which is adjustable about an axis of rotation, to focusing optics 126 which are common to all laser beams and which direct the laser beams onto a processing point 130 .

With the laser engraving device shown in FIGS. 4 and 5, the pattern of impact points shown in FIG. 3 and a practically unlimited number of other patterns can be generated. The individual intensity switches 151 for the individual laser beams Lx, Ly, Lz and Lw allow the desired power densities to be achieved at the processing points.

As explained at the beginning, is in a laser engraving system Manufacture of printing rollers the spiral scanning of the Surface of the roller the normal case. If you look at presents the printing of graph paper, so it is evident that with a spiral engraving on the Lateral surface of the printing roller the milli finally printed meter paper does not exactly match the Cartesian coordinates speaks, but is slightly beveled and - strictly speaking - has the shape of a parallelogram.

The example of the graph paper mentioned above illustrates light that basically the engraving of a cylinder jacket area in the form of closely spaced circular paths of the spiral track on the cylinder surface prefer is.

The spiral track arises from the fact that the laser head or the laser engraving device continuously translational is moved parallel to the axis of rotation of the printing drum.

According to the invention, an engraving in the form of one another following circular orbits achieved by the laser beams against the translational movement of laser engraving direction are tracked so that the machining do not place as in the spiral processing of the upper area of the pressure roller continuously compared to the latter moves, but intermittently in the form of successive the circular orbits. Jumps after one full turn  the processing point from a circular path to the adj traveled circular path.

This jumping from a circular path to the adjacent circular path can be done with the laser engraving device shown in FIG . B. achieve that the deflecting mirror 137 is pivoted about a perpendicular to the plane of the de axis. This pivoting movement corresponds to a time-dependent sawtooth curve. During practically a full revolution, the mirror is pivoted continuously, so that the processing point 130 practically does not move with respect to the longitudinal extension of the printing roller. If a circular path is completed, the deflecting mirror 127 jumps back into its starting position.

If the laser engraving device 102 shown in FIG. 4 moves in the direction of the arrow from bottom to top, the deflection mirror 127 is slowly pivoted counterclockwise, so that the processing point 130 does not move in the longitudinal direction of the printing roller.

Claims (7)

1. Laser engraving device, with a laser beam source ( 10 , 12 , 14 , 16 ; 110 , 112 , 114 , 116 ), a light transmission path ( 18 , 20 , 22 , 24 ; 152-156 ) and a beam guidance system ( 32 , 28 , 26 , 150 , 126 , 127 ) with which at least one laser beam (Lx, Ly) can be focused on a processing point ( 30 ) of a workpiece ( 4 ), characterized in that at least two laser beam sources ( 10-110-116 ) are provided , and that the beam guidance system has individual beam guidance devices ( 32 , 152 - 155 , 150 a - 150 d) for the individual laser beams (Lx, Ly, Lw) with which the relative position of the individual points of incidence (x, y, z, w) the laser beams at the processing point ( 30 , 130 ) are adjustable. 2. Laser engraving device according to claim 1, characterized in that the impingement points are adjustable with the beam guidance system such that they are at the processing point

• a) completely overlap ( Fig. 3 (A); or
• b) partially overlap ( Fig. 3 (C; D)) and / or
• c) lying next to each other in one or more rows or columns ( Fig. 3 (B)).

3. Laser engraving system according to claim 1 or 2, characterized records that the intensities of the laser beams individually are controllable. 4. A method for operating a laser engraving device according to any one of claims 1-3, in particular for the production of printing rollers, in which the laser beams are translated translationally para llel to the longitudinal axis of a workpiece ( 4 ) rotating about the longitudinal axis, characterized in that Beam guidance system ( 32 , 150 , 126 , 127 ) the laser beams so that the processing point next to each other lying, complementary to a cylinder jacket describes circular paths on the workpiece surface. 5. Laser engraving device according to one of claims 1-4, characterized in that a plurality of laser beam sources ( 110-116 ) are arranged on a carrier ( 101 ) and that a bundle of parallel laser beams is formed from the laser beams (Lx, Ly, Lz, Lw) will hit a block ( 150 ) of deflecting mirrors that can be adjusted individually for each laser beam around two axes ( 150 a... 150 d). 6. Laser engraving device according to claim 5, characterized in that in the light transmission path of each laser beam source ( 110 - 116 ) an intensity switch ( 151 ) and a deflecting mirror ( 152 - 155 ) is arranged so that the bundle of parallel laser beams is formed. 7. Laser engraving device according to claim 5 or 6, characterized in that the gels coming from the block ( 150 ) of deflection mirrors ( 150 a- 150 d) laser beams coming from a deflecting mirror ( 127 ) which can be pivoted about an axis onto a focusing optics common to all laser beams ( 126 ) can be directed.