DE102015105246A1 - Method and device for cutting metallic workpieces from a plate-shaped material - Google Patents

Abstract

The invention relates to a method for cutting metallic workpieces (16) from a plate-shaped material (7) in a laser cutting process, in which a laser beam (6) with an oxygen process gas jet (22) through a cutting nozzle (20) on a machining head (20). 4) is directed and pierced onto a processing location (B) on the plate-shaped material (7), in which the laser beam (6) is moved with the process gas jet (22) over the plate-shaped material (7), so that a continuous cutting gap (9) formed and the workpiece (16) from the plate-shaped material (7) is separated out to form a residual grid (8), during the cutting process, at least temporarily from the process gas (10) deviating foreign gas (14) is supplied to the processing site (B), and during the period of supply of the foreign gas in the kerf (9) slag is formed, which remains in the kerf (9) and this partially closes, so that the geschesch nittene workpiece (16) in the skeleton grid (8) is held. The invention also relates to a laser cutting machine suitable for carrying out the method.

Description

The invention relates to a method for cutting metallic workpieces from a plate-shaped material in a laser cutting process, in which a laser beam with an oxygen process gas jet through a cutting nozzle on a processing head of a laser cutting machine and directed at a processing location on the workpiece and the laser beam with the process gas jet is moved over the workpiece, so that a continuous kerf formed and the workpiece is separated from the plate-shaped material to form a residual grid. The invention also relates to a laser cutting machine suitable for carrying out the method.

When laser cutting plate-shaped materials, which in the context of the application also three-dimensionally shaped materials are understood to be greater than thickness, free-cutting parts can tilt due to their geometry or insufficient support of the workpiece support. This leads to an increased risk of collision for the machining head and a reduced cutting quality at the cutting end and makes it difficult to automatically unload a cut plate-shaped material, ie the at least one workpiece and the residual grid formed.

In order to avoid the tilting of cut workpieces in the skeletal grid, it is known not to complete the cut of the contour completely, but to save a bridge (so-called microjoint), which connects the workpiece with the skeleton. Alternatively, the kerf can be subsequently rewelded using a short laser pulse (so-called microwelds). Usually, the microjoints or microwelds are separated in a separate process step after unloading the plate-shaped material from the laser cutting machine. This can be done by manual breaking, vibration or by a new laser cutting process. A disadvantage of this method is that visible traces remain on the cutting edge, at least during the mechanical separation of the micro joints or microwells.

In the WO2010097761A1 Therefore, it was proposed alternatively to fix cut-free workpieces by introducing an adhesive in the skeletal grid, since the adhesive can then be removed more easily and without residue. Moreover, for example, from the JPH03138027A Known to keep cut workpieces with the help of adhesive tape in the skeleton.

From the DE4131650C2 a method for wire EDM is known in which by selectively influencing the erosion parameters, the erosion processes are changed so that use physico-chemical processes, the result of deposits in the erosion gap. These deposits can be generated so that they keep the cut workpiece in the skeleton. The deposits originate from the wire material of the erosion wire.

The invention has for its object to provide for the laser flame cutting a simple method to prevent the tilting of cut workpieces in the skeleton (residual workpiece).

The object underlying the invention is achieved by a method in which targeted during the cutting process at least temporarily a deviating from the process gas oxygen foreign gas supplied to the processing site on the plate-shaped material and during the period of supply of foreign gas in the cutting gap slag is formed, which in the kerf at least partially remains and this closes, whereby the cut workpiece is held in the skeleton (remnant workpiece). The method according to the invention requires neither micro joints nor microwelds in order to fix the cut-free workpiece to the residual grid without tilting. This has the advantage that free-cut workpieces are easily releasably held in the skeleton and can be solved with little force from the skeleton. As a result, after the workpieces have been separated from the residual grid, no neck marks or residues remain on the cutting edge of the workpieces. According to the invention, it has been recognized that, contrary to the previous procedure, to use oxygen of as high purity as possible for laser flame cutting, the oxidation conditions at the processing location or processing location can be specifically influenced to form slag in the kerf through the addition of a foreign gas to the process gas, so that the slag formed in the Cutting gap remains and the cut workpiece holds in the skeleton. The remaining slag at least partially fills the cutting gap, and at least one web is formed, through which or which the workpiece is or will be kept tilt-free relative to the residual grid.

Preferably, the processing parameters (especially gas pressure, amount of foreign gas and laser power) are chosen or adjusted so that from an exit side of the laser beam from the preferably plate-shaped material in the kerf starting and only partially over the height of the kerf is ersteckend a slag existing web is formed. The selection of the processing parameters thus causes the slag is generated only in the lower part of the cutting edge. As a result, the later breaking-out of the workpiece is easier and no mark remains visible on the cut edge, since the process-typical oxide layer on the cut edge in the lower region of the cut edge is the thickest and easiest to loosen.

During a movement of the machining head to produce the cutting gap, the length of the webs formed in the cutting gap of slag is preferably determined by the duration of the supply of the foreign gas. Thereby, depending on the thickness of the plate material and / or the size of the workpiece, the length of the webs can be set to ensure a sufficient fixation of the cut workpiece in the skeleton, so that a simple unloading from a processing machine is made possible. Preferably, the supply of the foreign gas at predetermined time intervals or permanently supplied. As a result, the length of the webs of slag can be determined. When cutting thin workpieces while the mixing of the foreign gas takes place with a shorter duration than when cutting workpieces of higher thickness and only short and few slag webs are formed. For small workpieces of small thickness, a single slag web can be sufficient. For thicker workpieces more or longer slag webs are generated to apply a higher holding force.

In laser flame cutting, a process gas jet is emitted through the cutting nozzle on the machining head in parallel or coaxial with the laser beam. As a process gas, oxygen with a high degree of purity is used to form the process gas jet. The supply of foreign gas leads to the targeted contamination of the process gas jet, whereby the oxidation conditions are changed at the processing site and the slag formation is effected. Nitrogen, a nitrogen-oxygen mixture (for example compressed air), hydrogen or a noble gas is preferably used as the foreign gas. By choosing the foreign gas and the strength of the slag can be influenced, so that the workpiece is securely held on the skeleton and at the same time a residue-free removal of the slag is ensured after demolding of the workpiece from the skeleton.

Preferably, the proportion of the supplied foreign gas is less than three, preferably less than one percent of the supplied process gas. It is sufficient even the smallest amounts of foreign gas to promote slag formation. For as far as possible residue-free removal of the slag, the foreign gas content is chosen to be very low. With increasing proportion of the foreign gas, the strength of the slag and thus the holding force for the workpieces in the skeleton, so that on the dosage of the foreign gas, the holding force is controllable. With increasing thickness of the workpieces therefore the dosage of the foreign gas is increased.

Furthermore, the foreign gas is preferably supplied through the cutting nozzle at the machining head or through an external gas nozzle directed at the machining location. As a result, the oxidation conditions at the processor site can be changed without influencing the process parameters for the laser flame cutting and the supply of the laser beam with the process gas jet.

Furthermore, the at least one web formed by the slag is preferably released by a mechanical stress acting on the residual grid or the at least one free-cutting workpiece. The or the webs, which are formed from the brittle slag, burst under a mechanical stress slightly, so that no neck marks remain on the workpiece. The residual grid can thus be removed together with the at least one cut-free workpiece from the workpiece support of the laser cutting machine or an unloading station, and only then can be caused by vibration or manual breaking loosening of the webs.

The invention and further advantageous embodiments and developments thereof are described in more detail below with reference to the examples shown in the drawings and explained. The features to be taken from the description and the drawings can be applied individually according to the invention individually or in combination in any combination. Show it:

1 a schematic representation of a laser processing machine,

2 1 is a schematic view of a workpiece produced by the method according to the invention from a plate-shaped material which is held in the skeleton by slabs of slag;

3 a schematic sectional view taken along the line II-II in 2 .

4 a schematic view of a skeleton with a cut workpiece during demolding and

5 a schematic enlarged detail view of a machining location aligned machining head with a foreign gas.

The 1 shows as an example of a laser cutting machine 1 a CO ₂ laser cutting machine to the laser-flame cutting with a CO ₂ laser source, a processing head 4 and a workpiece support 5 , One from the laser source 2 or one in the laser source 2 existing resonator generated laser beam 6 is by means of a beam guide 3 from deflecting mirrors (not shown) to the machining head 4 guided and focused in this, as well as with the help of in 1 also not pictorially represented mirrors perpendicular to the surface 8a a plate-shaped material 7 aligned. The beam axis (optical axis) of the laser beam 6 runs perpendicular to the surface 8a of the plate-shaped material 7 , The laser beam acts at the processor B together with an oxygen process gas jet 22 on the plate-shaped material 7 one. Alternatively, the laser cutting machine 1 have a solid-state laser as a laser source whose radiation is guided by means of a light guide cable to the laser processing head.

For laser-cutting the plate-shaped material 7 becomes with the laser beam 6 while supplying oxygen as a process gas 10 first pierced, that is, the plate-shaped material 7 is melted punctiform at one point and oxidized by an exothermic reaction. The following is the laser beam 6 over the plate-shaped material 7 moves, leaving a continuous kerf 9 arises at which the laser beam 6 the plate-shaped material is severed, whereby at least one cut-free workpiece 16 in the skeleton 8th arises ( 2 ). Both the piercing and the laser flame cutting takes place under the action of oxygen as a process gas. The process gas jet 22 becomes parallel or coaxial to the laser beam 6 fed. For the laser flame cutting usually oxygen as high purity with a gas pressure of 0.4 bar to 5 bar is supplied as a process gas.

The particles and gases produced during piercing and laser cutting can be removed by means of a suction device 11 from a suction chamber 12 be sucked off.

The control of the laser cutting machine 1 via a machine control device 21 , wherein the machine control device 21 controls the piercing process and the other control tasks for the laser cutting machine 1 for the formation of the kerf 9 takes over. The machine control device 21 stands with a laser control device 2a in signaling connection, typically in the laser source 2 is integrated.

During the production of the kerf 9 At least temporarily, the process gas oxygen becomes a foreign gas 14 fed. For example, via a separate feed line 15 leading to the machining head 4 leads, the foreign gas 14 the cutting nozzle 20 of the machining head 4 be supplied. As a foreign gas, nitrogen, hydrogen, a nitrogen-oxygen mixture - eg compressed air - or noble gases, such as helium or argon can be supplied.

By the at least temporary supply of foreign gas 14 to the process gas 10 change the oxidation conditions at the processing site B, creating a targeted slag formation in the kerf 9 is reached. Small impurities in the process gas lead to impairment of the cutting quality, which results in slag formation in and below the kerf 9 manifests. This slag formation is now used to within the kerf 9 one or more bars 18 from accumulating slag in the kerf 9 train. The slag adheres in the kerf 9 both on the skeleton 8th as well as the cut workpiece, whereby the webs 18 be formed. Through the bars 18 becomes the workpiece 16 in the skeleton 8th held.

The length of itself along the kerf 9 extending webs 18 is determined over the duration of the supplied foreign gas to the process gas. This allows, for example, a plurality of webs 18 along the cutting gap 9 form whose length and / or distances can be determined by the supply duration of the foreign gas. Both the number and the length of the bars 18 is dependent on the width of the kerf 9 , the thickness of the plate-like material 7 and the size and geometry of the workpieces to be cut to the required holding force for positioning the cut workpieces 16 within the rest grid 8th sure. By the formation of the webs 18 from slag can the cut workpiece 16 secured to the skeleton 8th be picked up to tilt the workpiece 16 from the skeleton 8th during the cutting process or during unloading.

In 3 is a schematic sectional view taken along the line II-II in 2 shown. This is a preferred embodiment of the at least one web 18 in the kerf 9 out. The jetty 18 only partially extends over the height of the kerf 9 or the thickness of the particular plate-shaped material 7 , By selecting and setting machining parameters of the laser beam 6 and / or the oxygen process gas jet 22 and / or the foreign gas jet 14 . 23 For example, the slag may be starting from an exit side of the laser beam 6 from the material 7 in the kerf 9 grow. The jetty 18 So it grows from a lower cut edge 26 in the cut material 7 upwards towards an upper one cutting edge 27 of the material 7 , This can be the bridge 18 from slag prefers only partially over the height of the kerf 9 extend, causing a release of the web 18 during removal of the cut workpiece 16 from the skeleton 8th is relieved.

During the supply of the foreign gas to the processing site B, the remaining process parameters for the laser flame cutting, such as, for example, cutting speed, laser power or the like, can advantageously remain unchanged.

For demolding the cut workpiece 16 from the skeleton 8th it is sufficient, for example, with a mechanical stress on the skeleton 8th and / or workpiece 16 to act, causing the web or bars 18 flake off and get out of the kerf 9 remove as in 4 is shown. At least, however, the webs 18 destroyed, allowing a subsequent easy removal of the cut workpiece 16 from the skeleton 8th is possible.

In 5 is an alternative embodiment for supplying the foreign gas 14 to the process gas jet 22 shown. At the processing head 4 is an additional foreign gas nozzle 24 provided by which a foreign gas jet 23 is supplied to the processing site B to change the oxidation conditions at the processing site B. The foreign gas jet 23 is inclined at an angle α, which is not equal to 0 ° or 180 °, to the beam direction Z of the laser beam 6 fed. The machine control device 21 activates the foreign gas nozzle 24 and also controls the pressure with which the foreign gas jet 23 flows to the processing site B.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• WO 2010097761 A1 [0004]
• JP 03138027 A [0004]
• DE 4131650 C2 [0005]

Claims (10)

Method for cutting metallic workpieces ( 16 ) of a particular plate-shaped material ( 7 ) by a laser cutting process in a laser cutting machine ( 1 ), - in which a laser beam ( 6 ) with an oxygen process gas jet ( 22 ) through a cutting nozzle ( 20 ) on a processing head ( 4 ) to a processing location (B) on the plate-shaped material ( 7 ) and pierced, - in which the laser beam ( 6 ) with the oxygen process gas jet ( 22 ) over the plate-shaped material ( 7 ) is moved, so that a continuous kerf ( 9 ) and a workpiece ( 16 ) from the plate-shaped material ( 7 ) to form a residual lattice ( 8th ), characterized in that - during the cutting process, at least at times, one of the oxygen process gas ( 10 ) deviating foreign gas ( 14 ) is supplied to the processing site (B), and - that during the duration of the supply of the foreign gas ( 14 ) in the kerf ( 9 ) Slag is formed, which in the kerf ( 9 ) remains and this at least partially closes, so that the cut-free workpiece ( 16 ) in the skeleton ( 8th ) is held. A method according to claim 1, characterized in that the processing parameters for driving the laser beam ( 6 ), the oxygen process gas jet ( 22 ) and / or the foreign gas jet ( 14 ) to the material to be cut ( 7 ) are adapted so that from an exit side of the laser beam ( 6 ) from the material to be cut ( 7 ) in the kerf ( 9 ) and only partially over the height of the kerf ( 9 ) extending a slag consisting of slag ( 18 ) is formed. A method according to claim 1 or 2, characterized in that during a movement movement of the machining head ( 4 ) by the duration of the supply of foreign gas to the processing site (B) the length of a in the kerf ( 9 ) from slag forming web ( 18 ) for fixing the cut-free workpiece ( 16 ) in the skeleton ( 8th ) is determined. Method according to one of the preceding claims, characterized in that the foreign gas ( 14 ) is supplied at predetermined time intervals or permanently to the processing site (B). Method according to one of the preceding claims, characterized in that as foreign gas ( 14 ) Nitrogen, a nitrogen-oxygen mixture, hydrogen or a noble gas is supplied. Method according to one of the preceding claims, characterized in that the from the process gas ( 10 ) formed process gas jet ( 22 ) has a volume fraction of less than 3%, in particular less than 1% of foreign gas ( 14 ) is supplied. Method according to one of the preceding claims, characterized in that the foreign gas ( 14 ) through the cutting nozzle ( 20 ) on the machining head ( 4 ) or by a foreign gas jet directed to the processing location (B) ( 23 ) from a foreign gas nozzle ( 24 ) is supplied. Method according to one of the preceding claims, characterized in that after the cutting of the at least one workpiece ( 16 ) from the plate-shaped material ( 7 ) the skeleton ( 8th ) together with by the slag in the skeleton ( 8th ) held at least one workpiece ( 16 ) from the laser cutting machine ( 1 ) is taken. Method according to one of the preceding claims, characterized in that by a on the skeleton grid ( 8th ) or the at least one cut-free workpiece ( 16 ) acting mechanical stress at least one formed by the slag web ( 18 ) is solved. Laser cutting machine ( 1 ) for cutting metallic workpieces ( 16 ) of a particular plate-shaped material ( 7 ) with a method according to one of the preceding claims, wherein the laser cutting machine ( 1 ) is adapted to a laser beam ( 6 ) and an oxygen process gas jet ( 22 ) by a on a processing head ( 4 ) arranged cutting nozzle ( 20 ) to a processing location (B) on the plate-shaped material ( 7 ), characterized in that - the laser cutting machine ( 1 ) a device ( 15 . 24 ) for supplying one of the oxygen process gas ( 10 ) deviating foreign gas ( 14 ) to the processing site (B), and - a controller ( 21 ), the duration of the supply and the amount of foreign gas ( 14 ) controls so that in the kerf ( 9 ) Slag is formed, which in the kerf ( 9 ) remains and this at least partially closes, so that the cut-free workpiece ( 16 ) in the skeleton ( 8th ) is held.

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