Method for machining a workpiece in a machine tool

Abstract

The present invention relates to a method for machining a workpiece in a machine tool, in which a tool is moved relative to a workpiece 1. The tool or the workpiece 1 is moved at a preset travel speed in a preset travel direction defined by a travel path 3. The travel path 3 is divided into a machining section 4 and an acceleration section 5. Within the machining section 4, between a starting point 6 and an end point 7 of the machining section 4, the workpiece machining is carried out at a preset machining travel speed in the machining travel direction. Along the acceleration section 5 defined by the end point 7 of the first machining section 4 and the starting point 6 of the second machining section 4, the travel speed is adapted such that the preset machining travel speed is achieved at the starting point 6 of the machining section 4.

Description

Technical Field

[0001] The present invention relates to a method for machining a workpiece in a processing machine, in which method, a tool is moved relative to the workpiece, the tool or the workpiece is moved at a preset moving speed in a preset moving direction by a movement locus, the movement locus is divided into a machining section and an acceleration section, within the machining section, workpiece machining is carried out at a preset machining moving speed in the machining moving direction between the start point and the end point of the machining section.

Background Art

[0002] In the higher-level concept used here for processing machines, cutting machines, painting machines, milling machines, and laser cladding machines are understood. Generally, all processing machines are equipped with an axis system in order to realize the moving motions necessary for the processing process, and with this axis system, the tool or the workpiece is moved. In that case, for each machining part for workpiece machining, in addition to the moving speed, further method-specific machining parameters are preset. In laser cladding, for example, the laser output, the degree of defocusing of the laser beam, the distance to the workpiece, or the powder mass flow rate are preset.

[0003] In that case, in machine control, the provided machining parameters can be preset at the start point and the end point of each machining part, and thus, these machining parameters and / or the moving speed along the machining section can be resolved and adapted in terms of time or position.

[0004] Often, the kinematic situation of the processing machine is based on the mass to be moved and the inertial forces resulting therefrom, The maximum acceleration along a defined portion of the movement trajectory and the associated increase in speed are restricted by the maximum allowable instantaneous movement conditional on the machine, and are thus restricted in such a way that the preset machining parameters are not achieved at the starting point of the machining part. For example, the preset machining travel speed at the starting point of the machining section is made to fall short based on an excessively low acceleration, and the machining process is carried out with actual machining parameters different from the preset target machining parameters, which is the case in such a situation. This result is one machining process, and this machining process is carried out under deviating process conditions, which can directly induce deviating machining results.

[0005] Furthermore, during the machining process at a high machining travel speed, a trajectory deviation due to the inertial mass may occur. In that case, the preset movement trajectory of the tool or workpiece is not maintained. This directly induces a deviation from the target geometric shape or, moreover, from the machining process, and this machining process is carried out under deviating process conditions, which can directly induce deviating machining results.

[0006] Laser cladding is used, in a variant of a known embodiment, for coating or repairing workpieces or for additive manufacturing of structural members (additive Fertigung). In that case, a powdery additive material, for example a metal powder, is introduced into the interaction zone of the laser beam with the metal powder using a powder supply nozzle, and there it is melted by the laser beam, and thus a bond of the melted metal powder with the workpiece or the already deposited layer occurs.

[0007] In extreme-high-speed laser cladding (Extremen-Hochgeschwindigkeits-Laserauftragschweissen (abbreviated as EHLA)), which is a variant of laser cladding, the powdery additive material is melted by a focused laser beam before the powdery additive material reaches into the molten pool generated by the laser beam. Accordingly, a very high travel speed in the range from 10 m / min to 500 m / min can be achieved, and a layer having a layer thickness in the range from 10 μm to 250 μm can be manufactured for each layer.

[0008] In that case, the workpiece can be moved relative to the laser beam and the powder gas jet, so that a melting track is generated on the workpiece surface. By the superimposed arrangement of the individual layers, a three-dimensional structure is additionally constructed. The construction of such a structure is carried out on an existing structural member or on a workpiece support plate during the generation of the entire object, and this workpiece support plate is used as a base part in that case.

[0009] In order to achieve such a high processing travel speed, the high requirements for the process technology and the kinematic situation of the equipment used therefor should be met.

[0010] In particular, in most cases, the large workpiece weight and the large mass of tools such as the powder nozzle or the laser optics should be considered during the moving motion.

Summary of the Invention

Problems to be Solved by the Invention

[0011] Providing a method approach for the processing process is regarded as an object of the present invention, The method steps can perform the machining of the workpiece at the start point of the machining section with preset machining parameters and at a feed rate ranging from 10 m / min to 500 m / min.

Means for Solving the Problem

[0012] According to the present invention, this problem is solved by adapting the feed rate along an acceleration section defined by the end point of the first machining section and the start point of the second machining section such that the preset machining feed rate is achieved at the start point of the machining section.

Advantageous Effects of Invention

[0013] In the EHLA method between the tool and the workpiece, a relatively high speed occurs in the range from 10 m / min to 200 m / min, preferably greater than 500 m / min, and a relatively high acceleration greater than 50 m / s² 2 causes a high impulse due to the moving mass. These impulses can affect the surrounding environment of the device and induce unwanted disturbances during the laser cladding process. The high impulses and accelerations generated by the acceleration of the tool or the workpiece along the acceleration trajectory section and, accordingly, outside the machining section can be reduced. This is because an extended acceleration section is used to reach the preset machining feed rate. Accordingly, the acceleration of the tool and the tool holder or the acceleration of the workpiece can be adjusted below the maximum allowable acceleration.

[0014] In this case, according to the present invention, it is also intended that the feed rate is reduced along with the increase in the feed rate along the acceleration section. Similarly, it is intended that the feed rate along the acceleration section does not change at all and that the feed rate of the workpiece or the tool is carried out at a constant speed along the acceleration trajectory.

[0015] In an advantageous variant of the inventive concept, in order to make the increased machining feed rate between the tool and the workpiece adjustable, for the movement of the tool relative to the workpiece, the workpiece is also moved, like the tool, It is intended that the tool and the workpiece are moved in different movement directions relative to each other, or at different movement speeds. Accordingly, a doubling of the machining feed rate can be achieved.

[0016] In an advantageous configuration of the invention, it is intended that the movement of the tool and / or the workpiece takes place in three spatial directions (x, y, z). In that case, the relative movement between the workpiece and the machining tool of the processing machine is decisive. Depending on the configuration and type of each processing machine, the movement of the workpiece and / or the movement of the machining tool takes place. For this purpose, these movements are carried out in three spatial directions (x, y, z), preferably in a path movement.

[0017] In an advantageous configuration of the invention, the acceleration section is divided into a plurality of acceleration path sections, It is intended that these acceleration path sections can be preset respectively by the geometric shape and length of the acceleration path section. Accordingly, a particularly flexible configuration of the acceleration part is possible. The geometric shaping of the acceleration part is carried out, for example, as a straight line, as a circular segment with a predetermined radius, as a hyperbolic part, etc.

[0018] In an advantageous configuration of the method according to the invention, in order to achieve depending on the desired optimization of the workpiece machining, the geometric shape and the length of the acceleration path section are intended to depend on the machining feed rate preset at the start and end points of the machining section. Accordingly, it is possible to design an acceleration trajectory portion for the purpose of a certain moving speed, a certain acceleration, a reduced trajectory deviation in the process, a reduced instantaneous motion, or a shortened processing time.

[0019] In an advantageous configuration of the inventive concept, it is intended that the machining section extends in all three spatial directions (x, y, z), and thus there is no plane in which all the acceleration sections are aligned. Advantageously according to the present invention, at least one acceleration trajectory portion is formed in one acceleration trajectory plane, and this acceleration trajectory plane is intended to be different from the machining trajectory plane including the starting point or the end point of the machining portion. Due to the fact that the moving motion of the tool and / or the workpiece is possible in the three spatial directions (x, y, z), accordingly, it is possible to obtain a flexible configuration of the moving motion and the moving speed along the acceleration trajectory portion. Thereby, it is likewise possible that the moving speed along the acceleration portion is kept constant. This is because the geometric shape of the acceleration portion is selected, whereby the maximum allowable acceleration associated with the machine is not exceeded. Similarly, depending on the margin state restricted by the workpiece or the tool and available for use, the configuration of the acceleration trajectory portion can be optimally utilized in the three spatial directions (x, y, z).

[0020] In order to be able to compensate for the moving speed difference, in order to achieve a preset machining moving speed at the starting point, especially in the case of a large difference between the machining moving speed at the end point of the machining portion and the machining moving speed at the starting point of the next machining portion, a large acceleration of the tool or the workpiece is required. In that case, the acceleration trajectory portion is arranged in the machining portion and has a geometric shape such that the moving speed along the acceleration portion can be effected, for example, by a constant acceleration of the tool or the workpiece. This can be achieved, for example, by a geometric configuration as a circle having a certain radius, or by a hyperbolic portion, and thus the maximum allowable acceleration associated with the machine can be undershot.

[0021] However, an increase in the moving speed along the acceleration portion and a decrease in the moving speed can also be considered, and thus, overall, a reduced processing time is possible.

[0022] Accordingly, an increase in the moving speed to the processing moving speed at the starting point is not necessary, or is only necessary within a small range, and thus a shortened processing time is possible.

[0023] In an advantageous configuration of the method according to the invention, in order to enable a traversal without acceleration above the starting point, in the moving direction, an acceleration trajectory section preceding the starting point of the processing section is intended to be oriented such that, when viewed in the moving direction, the transition angle formed by the acceleration trajectory section and the processing moving direction at the starting point of the processing section has a value from 0 degrees to 1 degree. For example, it is possible that the preceding acceleration trajectory portion is arranged tangentially to the processing portion, where this processing portion is configured in a circular shape, an elliptical shape, or a shape different from a straight line. Particularly advantageously, the preceding acceleration trajectory portion is connected to the processing portion without displacement, and thus a traversal without acceleration and without a stepped movement motion above the starting point is possible.

[0024] In an advantageous configuration of the invention, in order to enable particularly rapid workpiece processing, it is intended that the workpiece processing within the processing section is carried out at a processing moving speed within the range from 10 m / min to 500 m / min.

[0025] In an advantageous variant of the inventive concept, it is intended that the processing machine is configured such that extreme-high-speed laser cladding (Extrem-Hochgeschwindigkeitsauftragschweissen (EHLA)) can be carried out with this processing machine.

[0026] For this purpose, the workpiece is moved relative to a welding head that is arranged parallel to the workpiece carrier in three spatial directions (x, y, z). During extreme-high-speed laser cladding, a powder nozzle is used as a tool, and prior to the molten powder reaching the melt pool generated on the workpiece surface, the powdery additive material is injected into the laser beam through this powder nozzle. Thereby, on the workpiece surface, extremely thin coatings with a layer thickness in the range from 10 μm to 250 μm are generated layer by layer.

[0027] A further advantageous configuration of the present invention will be explained based on the embodiment illustrated in the figures.

Brief Description of the Drawings

[0028]

Figure 1

Figure 2

Modes for Carrying Out the Invention

[0029] In FIG. 1, the workpiece 1 in a schematic illustration is shown in a plan view. In addition, a movement trajectory 3 schematically illustrated is shown on the workpiece surface 2 of this workpiece 1. Along the movement locus 3, a tool (not shown) is moved in the movement direction preset by this movement locus 3 at a presettable movement speed. The movement locus 3 is divided into a machining section 4 and an acceleration section 5. Each of the machining sections 4 is defined by a starting point 6 and an end point 7. At this time, within this machining section 4, workpiece machining is carried out by a tool (not shown) at a machining movement speed. Along the acceleration section 5 determined by the end point 7 of the first machining section 8 and the starting point 6 of the second machining section 9, the movement speed is adapted such that the preset machining movement speed is achieved at the starting point 6 of the machining section 4. At that time, the first acceleration section 11 is configured in a semi-circular shape. The second acceleration section 12 is divided into two acceleration locus sections 10. At that time, the first acceleration locus section 10 is configured as a circular segment, and the second acceleration locus section 10 is configured as a straight line. In the movement direction, the second acceleration locus section 10 preceding the starting point 6 of the third machining section 13 is arranged with no displacement and no interruption in the movement direction with respect to the third machining section 13. Therefore, the tool (not shown) is moved from the acceleration locus section 10 of the second acceleration section 12 into the third machining section 13 without a stepped movement motion.

[0030] In FIG. 2, the workpiece 1 is shown in a perspective view, where the workpiece 1 is shown in a schematic illustration. In addition, the movement locus 3 schematically shown on the workpiece surface 2 of this workpiece 1 is shown. Along the movement locus 3, a tool (not shown) is moved in the movement direction preset by this movement locus 3 at a presettable movement speed. The movement locus 3 shown in FIG. 2 is divided into a first machining section 8, a second machining section 9, and an acceleration section 5. In that case, the acceleration section 5 is divided into two acceleration locus sections 10. In that case, the second acceleration trajectory section 10 is arranged within the acceleration trajectory plane, which is different from the machining trajectory plane including the start point or the end point of the machining section.

[0031] In the illustrations of FIGS. 1 and 2, only some of the plurality of like elements are exemplarily labeled with one reference sign.

Claims

1. A method for machining a workpiece within a machining machine, wherein in this method, The tool is moved relative to the workpiece (1), The tool or workpiece (1) is moved in a predetermined direction of movement by the movement trajectory (3) at a predetermined speed. The movement trajectory (3) is divided into a processing section (4) and an acceleration section (5). Within the processing section (4), workpiece processing is performed between the start point (6) and end point (7) of the processing section (4) at a processing movement speed that can be set in advance in the processing movement direction, and the movement speed is adjusted along the acceleration section (5) determined by the end point (7) of the first processing section (4) and the start point (6) of the second processing section (4) so ​​that a preset processing movement speed is achieved at the start point (6) of the processing section (4). A method characterized by the following:

2. For the relative movement of the tool to the workpiece (1), the workpiece (1) is also moved along with the tool. The tool and the workpiece (1) are moved in different directions or at different speeds. The method according to feature 1.

3. The movement of the tool and / or workpiece (1) is performed in three spatial directions (x, y, z). The method according to feature 1.

4. The acceleration section (5) is divided into multiple acceleration trajectory sections (10). These acceleration trajectory sections (10) can each be predetermined by their geometric shape and length. The method according to feature 1.

5. The geometric shape and length of the acceleration trajectory section (10) are as follows: The processing speed depends on a preset processing speed at the start point (6) and end point (7) of the processing section (4). The method according to feature 4.

6. The processing section (4) extends in all three spatial directions (x, y, z), and therefore, there is no single plane in which all the acceleration sections are aligned. The method according to claim 1, characterized by the features described above.

7. In the direction of movement, the acceleration trajectory section (10) preceding the starting point (6) of the processing section (4) is, The method according to 4, characterized in that, when viewed in the direction of movement, at the starting point (6) of the processing section (4), the transition angle (17) formed by the acceleration trajectory section (10) and the processing movement direction is aligned to a value between 0 degrees and 1 degree.

8. Within the processing section (4), workpiece processing is carried out at a processing travel speed within the range of 10 m / min to 500 m / min. The method according to claim 1, characterized by the features described above.

9. The method according to 8, characterized in that the processing machine is configured to enable ultra-high-speed laser cladding (EHLA) to be performed by the processing machine.

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