DEVICE AND METHOD FOR EXTREMELY HIGH-SPEED FABRIC WELDING

Description

Technical area:

[0001] The present invention lies in the field of laser cladding and relates to a device and a method for laser cladding, in particular for carrying out an Extreme High Speed ​​Laser Cladding (EHLA) process. State of the art:

[0002] Conventional laser metal deposition (LMD) processes are used for surface treatment, repair, and additive manufacturing of components. In this process, a powdered filler material, such as metal powder, is introduced into the interaction zone of the laser beam with the base material using a powder feed nozzle and melted there by the laser beam, creating a bond.

[0003] In a variant of laser cladding, Extreme High-Speed ​​Laser Cladding (EHLA), the powdered filler material is melted by the laser beam before entering the melt pool created by the laser beam. This allows for very high traverse speeds of up to 500 m / min or more and the production of layer thicknesses in the range of 10–250 µm per layer. Such a process is, for example, part of DE 10 2011 100 456 B4. In this process, at least one filler material in completely molten form is added to a melt pool present on the surface to be processed. For this purpose, the filler material, which is initially in powder form, is melted by a laser beam at a distance greater than zero from the melt pool and then added to the melt pool in liquid form.In this process, the workpiece surface can be moved relative to the laser beam and the powder gas jet, causing the melt pool to move across the surface. This method allows for particularly high workpiece movement speeds of more than 50 m / min. Three-dimensional structures can be additively built by layering individual components. These structures can be built either on existing components or, when creating entire objects, on a workpiece carrier plate, which then serves as the base.

[0004] To achieve such high process speeds, stringent requirements are placed on the process technology and the kinematics of the equipment used. For example, the powder feed to the powder nozzle must be designed in such a way that the introduction of the powder into the laser beam is optimized and the powder efficiency is maximized. Such solutions are described, for example, in DE 10 2014 220 183 A1, which describes a laser beam arrangement capable of generating multiple individual laser beams to achieve high powder efficiency. A disadvantage, however, is that the individual laser beam sources must be coordinated to focus precisely on the powder, which is very complex. A nozzle for laser cladding is described, for example, in EP 2 774 714 A1. This nozzle ensures the defined feed of powder into the laser beam.

[0005] Also critical is the extremely rapid movement of the welding head and / or the workpiece carrier. Machine tools frequently employ storage devices for machining a material, which are referred to as tripods or hexapods. Such devices are, for example, part of DE 196 40 769 A1, US 5,401,128, and DE 199 03 613 C1. Solutions for a hexapod are also part of US 6,196,081 B1 and DE 10 2010 025 275 B4. However, these devices are only conditionally or not at all suitable for use in extreme high-speed laser cladding (EHLA) because they are not designed for the precision required at high accelerations or decelerations.

[0006] US patent 2017 / 0282297 A1 describes a device for moving a nozzle along the x, y, and z coordinates, consisting of a tripod and suspensions for a nozzle unit. Five actuators are required for the movement. The workpiece itself, however, is not moved and remains fixed.

[0007] DE 33 19 665 A1 describes a device for the linear movement of spray nozzles with a counterweight. This requires a spring-loaded deflection pulley, which, however, limits high dynamics. The use of springs for energy storage at defined reversal points and the limit switches located there only allow for a fixed, preset working stroke at low speed. Such a device would not be suitable for the EHLA process.

[0008] The same applies to the device described in CN 105 499 796 A, in which the working head is also guided while the product carrier plate is fixed. Vertical acceleration forces are also not compensated. The same applies to the variant of CN 105 773 984 A, which forms the basis for the preamble of claim 1, a tripod device for 3D printing. Description of the invention:

[0009] It is therefore an object of the present invention to provide a device and a method for extreme high-speed laser cladding, with which high traverse speeds of up to 500 m / min are possible with high path and repeatability accuracies.

[0010] This problem is solved by a device and a method according to the invention, as claimed in the following independent claims. Preferred embodiments are described in the dependent claims.

[0011] The device according to the invention enables a relative speed between the welding head and the workpiece carrier plate of greater than 50 m / min or more for layer thicknesses typically from 0.01 mm to 0.25 mm when using the EHLA process, and higher layer thicknesses when using other cladding welding heads. Depending on the dynamics, the type of contour to be built up, and the process parameters, path accuracies of better than 0.01 mm are achieved. The device must be designed so that, for example, accelerations of the welding head below the maximum permissible acceleration can be set. Such mechanics can be achieved through the design according to the invention and, in particular, the novel suspension of the workpiece carrier or the carrier for the welding head in the device.

[0012] The device according to the invention comprises at least three drive columns with – depending on the embodiment – ​​a workpiece carrier arranged centrally between the drive columns for receiving the product to be manufactured or processed, and / or a support plate for the welding head. The workpiece carrier has a receiving area for receiving a product to be manufactured or processed. Several tension-compression struts are arranged isosceles on the workpiece carrier and / or the support plate, with at least one tension-compression strut provided per drive column, preferably a pair of tension-compression struts per suspension point. The workpiece carrier and / or the support plate is movably connected via the tension-compression struts in the three spatial directions (x, y, z). For this purpose, pivot joints are provided at the ends of the tension-compression struts, which couple the strut to the workpiece carrier or support plate at one end and to the drive column at the other end.Each drive column comprises at least one inner guide rail facing the workpiece carrier and / or the support plate, with an inner slide guided therein for performing movements in the three spatial directions (x, y, z), preferably path movements of the workpiece carrier and / or the support plate. For this purpose, the inner slide is guided along the inner guide rail, preferably vertically upwards or downwards. Furthermore, the device also includes the welding head, for example, the laser head with a powder feed nozzle for introducing the filler material into the weld pool. Instead of a powder feed nozzle, a wire feed welding nozzle can also be used.

[0013] The term "top" used here refers to the top side of the respective component or the entire device when viewed from the front, while "bottom" refers to its bottom side. The terms "inside" and "outside" describe the component's position relative to the product being manufactured. Thus, the inner guide rail faces the product, while the outer guide rail is located on the side of the drive column facing away from the product. Preferably, the inner and outer guide rails are mounted opposite each other on the drive column.

[0014] The term "workpiece carrier" refers to the component that holds the product to be manufactured or processed. The term "carrier plate" refers to the component that holds the welding head, preferably the laser head. According to the invention, an outer slide is guided in the outer guide rail for the vertically opposite guidance of a counterweight relative to the inner slide. According to the invention, the counterweight ensures mass balance in the EHLA process, which occurs at speeds of > 200 m / min, preferably 500 m / min or more, and accelerations of 50 m / s² or more. At these high traverse speeds, the moving masses generate high impulses. These impulses can affect the surroundings of the device and lead to undesirable disturbances in the laser deposition process.The counterweights and the interaction of the individual drive columns allow horizontal mass movements to be at least partially absorbed. The solution according to the invention provides for a separation of the drive systems, thereby enabling almost complete compensation of vertical mass movements.

[0015] The welding head is preferably arranged parallel to the workpiece carrier, preferably above the workpiece carrier. This is preferably a laser welding head or a soldering head.

[0016] In one embodiment of the device, three drive columns are provided, in which the tension-compression struts are connected from above to the head of the workpiece carrier and / or support plate and to the drive columns via pivot joints. The axis endpoints, and thus the suspensions, are preferably arranged on the workpiece carrier or support plate according to an isosceles triangle, thereby holding the workpiece carrier or support plate without tilting and allowing the workpiece carrier or support plate to move in the horizontal plane (x, y) and in the vertical direction (z), or a combination of the three spatial directions. This embodiment is preferably a tripod.

[0017] The slides are preferably driven by highly dynamic linear direct drives. DE 203 06 233 U1 describes such a linear guide principle for powder spray guns. This drive variant enables very high accelerations to achieve speeds of over 5 m / s with virtually any stroke. Of course, other drive concepts are also possible for performing a path movement of the workpiece carrier and / or the carrier plate. The path movement of the workpiece carrier or carrier plate is preferably a movement along the x, y, z spatial axes, preferably implemented as a synchronous movement of three axes.

[0018] It is preferably intended that the tension-compression struts are not adjustable in length in order to ensure efficient energy chain guidance and to avoid uncontrolled vibrations of the workpiece carrier or carrier plate for the welding head.

[0019] The workpiece carrier and / or support plate is preferably suspended at six points. This means that a pair of tension-compression struts is provided at each suspension point, which in turn are connected to a slide of a drive column. Preferably, the workpiece carrier and / or the support plate is suspended at six points by two parallel tension-compression struts of equal length, with each pair of tension-compression struts being connected to a slide of a drive column. This prevents the workpiece carrier or the support plate from being rotated out of its horizontal position.

[0020] In a further developed embodiment, a six-axis geometry is provided, in which each individual tension-compression strut is connected to its own inner slide (hexapod). Accordingly, each drive column comprises a slide connected to a tension-compression strut with a corresponding guide rail for the vertical guidance of the slide and the tilting of the workpiece carrier or support plate. This allows tilt angles of preferably up to 80° for the workpiece carrier or support plate. Preferably, the vertical guidance of the slides—i.e., the inner, product-facing slide and the outer slide running along the rear of the drive column—is achieved via deflections mounted at the top and bottom of each drive column, respectively. The vertical guidance of the slides is provided by a drive belt, preferably a toothed belt. Preferably, a drive clamp for the drive belt is provided.Preferably, in this variant, each individual tension-compression strut is a drive column with its own independently vertically movable carriage within its own guide rail of a drive column, individually movable in the vertical direction.

[0021] According to the invention, the welding head is held by the carrier plate, which is arranged parallel to the workpiece carrier, preferably above or below it. In a further developed embodiment, a wobble plate is suspended between the carrier plate and the workpiece carrier, allowing for axial displacement of the welding head. This enables the production of different components and a high degree of adaptability of the device to individual production requirements. With the aid of this low-inertia wobble device, corrections can be made, in particular, to the relative or absolute inaccuracies of the laser head's trajectory that originate from the inertia between the control and drive elements. The wobble plate also enables the handling of small partial movements, such as tight curve radii, during traversal or the creation of compact weld structures.This can relieve the main musculoskeletal system and increase the speed of the overall system.

[0022] In a basic configuration, the welding head (i.e., the laser head) is fixed to a suspension above the workpiece carrier. However, the increasing size of the structures being manufactured can cause the center of gravity of the workpiece carrier to shift significantly, necessitating a reduction in the speed and / or acceleration of the workpiece carrier. To avoid this, a coupling system for the welding head on the workpiece carrier is preferably provided, and this coupling system is preferably automated. This is preferably a three-point coupling that allows the welding head to be transferred from the workpiece carrier.

[0023] The wobble plate also enables the creation of contours or curves that are normally generated by creating small segments in the three spatial directions (x, y, z) using the principal axes. However, dividing a curve into very small segments necessitates constant course corrections with continuously changing lateral accelerations. Due to mechanical inertia, the principal axes cannot complete a given set of movements before the control system transmits a new set. Therefore, in high-speed processes, radii are shifted towards the inside of the curve as the track speed increases. Circular paths then have a smaller diameter. This leads to overshooting and path deviation.

[0024] In this variant, the wobble plate according to the invention enables the compensation of over-grinding by allowing an axial offset of the welding head of approximately 1° - 5°, preferably 1° - 3°.

[0025] Preferably, the support plate is suspended from a cover plate via an upper coupling socket gripping from above and a lower coupling socket gripping from below, using corresponding supports. Preferably, the wobble plate is connected to the support plate via suspensions to achieve the required axis offset.

[0026] In another variant, a support plate for the welding head is positioned above the workpiece carrier, each suspended by its own tension-compression struts. Each plate has its own carriage, which is vertically movable within a common guide on a drive column. This variant allows for adjustment of both the workpiece carrier and the welding head via the support plate, as the tension-compression struts, with swivel joints at their ends, enable movement of the support plate or workpiece carrier in the three spatial directions (x, y, z). The tension-compression struts can be coupled to the workpiece carrier or the support plates either on their side, top, or underside.In a preferred embodiment, the tension-compression struts are coupled to the workpiece carrier for the product from the side, while the tension-compression struts of the carrier plate for the welding head are coupled from above. Depending on the production method, other embodiments are also conceivable.

[0027] In one variant, both the support plate and the workpiece carrier are individually movable in the three spatial directions x, y, z. In another, preferred variant, the support plate is fixed and the workpiece carrier is movable along its axis in the three spatial directions x, y, z.

[0028] Preferably, in a further embodiment, a swivel-rotation device is provided for the product to be manufactured in order to enable synchronous counter-rotating movements of independent axis systems at high speeds of movement of the non-laser-head-guiding axis system. The swivel device is arranged below the workpiece carrier and allows tilting and / or rotation of the product.

[0029] The invention also relates to a method for extreme high-speed cladding (EHLA) according to claim 14.

[0030] In this process, a powdered filler material is injected through a powder nozzle into the melt pool created by the laser beam on the component surface and melted. This creates a thin layer on the component. In the EHLA process, the powdered filler material is injected into the laser beam and melted there before the powder reaches the melt pool. The aim is to generate the densest possible, homogeneous powder gas jet with a high powder utilization rate. This allows thin layers to be applied to components with high accuracy at high process speeds, for example, for parts in the automotive or aerospace industries. The device according to the invention, in its basic version, requires only three actuators.

[0031] The method according to the invention is used to manufacture a product or workpiece.

[0032] The inventive method can utilize different nozzles. Examples include various powder cone nozzles, hybrid processing nozzles, or multi-jet nozzles.

[0033] The inventive method preferably uses welding nozzles, such as powder feed nozzles or wire feed nozzles.

[0034] After cutting with a laser cutting head, subsequent processing of the workpiece with a milling head is also possible. In a preferred embodiment, the device and method according to the invention therefore comprise an axially movable milling head. This can also be connected in series with the welding head.

[0035] In a further preferred variant, a subsequent optional coating of the workpiece is also provided after laser processing and / or milling.

[0036] In another embodiment, an oscillating operation is used to create curves and cavities in the workpiece; that is, the material is not applied continuously but rather in phases corresponding to the workpiece's structure. Preferably, the welding head is guided horizontally, vertically, or diagonally to form, for example, a curved or path-like structure. This allows, for instance, the production of highly structured housings for automatic and manual transmissions, nozzles for rocket engines, complex brackets or axle systems, or infill structures of solid bodies.

[0037] The inventive method can also utilize amorphous material compositions, such as crystalline solids, amorphous solids, or mixtures thereof. Amorphous materials generally consist of the same material as crystalline solids. The difference lies in the lattice orientation during cooling. Amorphous solids form when the material cools so rapidly that the atoms can no longer align. This allows the production of sandwich materials such as tool steel with a bronze coating for mold making, aluminum / stainless steel layers for the aerospace industry, or titanium-steel structures as tool armoring in the glass industry. Furthermore, mixed material compositions can be realized, such as a tungsten carbide matrix on gray cast iron for use in brake discs or for DLC tool coating. Brief descriptions of the drawings:

[0038] The invention is explained in more detail in the following drawings. They show: Fig. 1 a first embodiment of the device in the form of a tripod, Fig. 2 a further embodiment in the form of a hexapod, Fig. 3 a further developed variant with wobble plate, Fig. 4 a detailed view of the wobble plate with welding head suspension, Fig. 5 a combined axis system for a moving workpiece carrier and a moving support plate, Fig. 6 an alternative axis system for a moving workpiece carrier and a moving support plate, Fig. 7 a combined solution with an additional rotary-swivel unit. Ways to implement the invention :

[0039] In Fig. 1A possible embodiment of an EHLA device is shown, featuring a workpiece carrier 1 for the product to be manufactured or processed and a central receiving area 28 for processing or manufacturing the product using the laser cladding process. The workpiece carrier 1 is suspended by tension-compression struts 15 at six different points. Each tension-compression strut 15 is connected to a lower pivot joint 3, which is linked to the workpiece carrier 1, and to an upper pivot joint 4, which is coupled to a slide 6. The workpiece carrier 1 is centrally located between three drive columns (2.1, 2.2, 2.3) and can be moved along one or more of the spatial directions x, y, and / or z via the slides 6. A slide 6 is moved vertically along inner guide rails 5 aligned with the workpiece carrier 1, thus setting the workpiece carrier 1 (or, in another embodiment, the support plate 20) into a path movement.

[0040] The carriage 6 is connected to a drive belt clamp 7, which in turn couples the tension-compression struts 15 via the pivot joints 4. The vertical movement of the inner carriage 6 is effected by a drive belt 12, preferably a toothed belt. An outer guide rail 8 is located on the rear side of each drive column 2 (i.e., opposite the inner guide rail 5), in which an outer carriage 11 is guided. A counterweight 9 is also provided for mass balancing. The rear carriage 11 also includes a drive belt clamp 10. For guiding the drive belt 12, deflections 13, 14 are provided at the top and bottom of each drive column. The tension-compression struts 15 support the workpiece carrier 1 from above.

[0041] In Fig. 2A further developed version is provided in which each individual tension-compression strut 15.1, 15.2, etc. of a drive column 2.1, 2.2, etc. runs in its own guide rail 5.1, 5.2, etc., over a slide 6.1, 6.2, etc. Here, however, each individual tension-compression strut 15.1, 15.2, etc., is individually movable. Each axis includes its own counterweights 9.1, 9.2, etc., which are guided vertically opposite to the guidance of the inner slide 6 via its own slides 11.1, 11.2, etc. Here, too, the workpiece carrier 1 is suspended from above via the tension-compression struts 15.

[0042] In Fig. 3 The three drive columns 2.1, 2.2, 2.3 are held by a base plate 17 and a cover plate 16. The support plate 20 for the welding head 22 is held by brackets 30, which are connected to the cover plate 16. Additionally, a wobble plate 21 is provided, which allows for axial displacement of the welding head 22.

[0043] In Fig. 4 The construction of the wobble plate / assembly is shown in more detail. The support plate 20 for the welding head 22 is held on the bracket 30 by means of an upper coupling socket 24, an upper coupling mandrel 25, and a lower coupling socket 26. The workpiece carrier 1 for the product to be manufactured also includes lower coupling mandrels 23, which are arranged between two tension-compression struts 15 on the surface of the workpiece carrier 1. The wobble plate 21 is connected to the support plate 20 by means of a suspension 27. This allows for an axial offset of 1° to 3°.

[0044] In Fig. 5Another variant is shown, comprising both a support plate 20 with a welding head 22 and a workpiece carrier 1 for a product to be manufactured or processed. The tension-compression struts 15 are connected to both the workpiece carrier 1 and the support plate 20 from above at six defined suspension points. According to the invention, the upper support plate 20 is movable in three spatial directions via its own slides 6.2. The slide 6.1, the workpiece carrier 1, and the slide 6.2 of the support plate 20 run in the same guide rail 5 of a drive column 2.1, 2.2, and 2.3, respectively.

[0045] In Fig. 6 is a variation of the one in Fig. 5The variant shown illustrates this by coupling the tension-compression struts 15 to the workpiece carrier 1 from below. Here too, the individual tension-compression struts 15.1, 15.2, etc. for the workpiece carrier 1 and the support plate 20 are individually movable in three spatial directions.

[0046] In Fig. 7 An embodiment is shown in which a rotary-swivel unit is additionally provided. This comprises a swivel device 31 and a rotary joint 33 for tilting and rotating a product receiving area 32 for the product to be manufactured or processed.

[0047] With the devices and methods according to the invention, speeds of > 200 m / min, but preferably up to 1,000 m / min, and accelerations of up to 100 m / s² can be achieved for carrying out an EHLA deposition process. High accuracies are achieved with small layer thicknesses. List of reference symbols:

[0048] 1 = Workpiece carrier 2 = Drive column 3 = Lower swivel joint (product carrier plate) 4 = Upper swivel joint (drive column) 5 = Inner guide rail 6 = Inner carriage 7 = Drive belt clamp 8 = Outer guide rail 9 = Counterweight 10 = Drive belt clamp 11 = Outer carriage 12 = Drive belt 13 = Lower drive belt deflection 14 = Upper drive belt deflection 15 = Tension-compression struts 16 = Cover plate 17 = Base plate 18 = Upper drive column mount 19 = Lower drive column mount 20 = Support plate 21 = Wobble plate 22 = Welding head 23 = Lower coupling mandrel 24 = Upper coupling socket 25 = Upper coupling mandrel 26 = Lower coupling socket 27 = Suspension 28 = Product holder 29 = Welding head mount 30 = Bracket 31 = Swivel mechanism 32 = Product holding area 33 = Swivel joint

Claims

1. A device for extreme high-speed weld cladding, comprising: - at least three drive columns (2), - a workpiece support (1) for a product to be manufactured, which is arranged centrally between the drive columns (2.1, 2.2, 2.3), which - is movably connected to the drive columns (2.1, 2.2, 2.3) in three spatial directions (x, y, z) via multiple tension-compression struts (15) and rotary joints (3, 4) attached to the ends thereof, wherein - each drive column (2.1, 2.2, 2.3) has at least one inner guide rail (5) facing the workpiece support (1) with an inner carriage (6) guided therein for moving the workpiece support (1) in the three spatial directions (x, y, z), - wherein the device comprises a welding head (22) with a nozzle in the form of a powder nozzle or a wire nozzle, wherein the welding head (22) with the nozzle is held by a support plate (20) between the drive columns (2), characterized in that the device has an outer guide rail (8) with an outer carriage (11) guided therein for guiding a counterweight (9) in a vertically opposite direction to the inner carriage (6), wherein the counterweights (9) ensure mass balancing at speeds of > 200 m / min and accelerations of 50 m / s2 or more.

2. The device according to claim 1, characterized in that the workpiece support (1) is suspended at six points via two equally long parallel tension-compression-struts (15) each, wherein two tension-compression-struts (15) each are connected to an inner carriage (6) of a drive column (2).

3. The device according to claim 1 or 2, characterized in that the carriages (6, 11) are guided via idlers (13, 14) for drive belts (12) provided on the drive columns (2).

4. The device according to one of the preceding claims, characterized in that the carriages (6, 11) of the drive columns (2) comprise a drive belt clamping (7, 10) for a drive belt (12).

5. The device according to one of the preceding claims, characterized in that each individual tension-compression-strut (15.1, 15.2) of a drive column (2.1, 2.2, 2.3) can be individually moved in the vertical direction within its own guide rail (5.1, 5.2) with its own, independently vertically movable carriage (6.1, 6.2)6. The device according to one of the preceding claims, characterized in that the welding head (22) is held by a support plate (20), which is arranged parallel to the workpiece support (1) for the product to be manufactured, wherein a wobble plate (21) is additionally suspended between the support plate (20) and the workpiece support (1) enabling an axial displacement of the welding head (22).

7. The device according to claim 6, characterized in that the support plate (20) for the welding head (22) is suspended to a cover plate (16) via an upper coupling socket (24) engaging from above and to the holder (30) via a lower coupling mandrel (25) engaging from below.

8. The device according to claim 6 or 7, characterized in that the wobble plate (21) is connected to the support plate (20) via suspensions (27).

9. The device according to one of the preceding claims, characterized in that the tension-compression-struts (15), which can be vertically moved in the drive columns (2), are coupled to the workpiece support (1) either from the side or on its upper side or its lower side.

10. The device according to claim 1, characterized in that a rotary pivot device (31, 33) is provided for receiving the product to be manufactured in the product receiving area (32), which is arranged below the support plate (20) for the welding head (22).

11. The device according to one of the preceding claims, characterized in that the welding head is a laser welding head or a soldering head.

12. The device according to one of the preceding claims, characterized in that an axially movable milling head is additionally provided for subsequent processing of the workpiece.

13. The device according to one of the preceding claims, characterized in that the support plate (20) is designed to be immovable and the workpiece support (1) can be axially moved in the three spatial directions x, y, z.

14. A method for manufacturing a product by extreme high-speed weld cladding (EHLA), wherein a workpiece support for the product to be manufactured is moved via at least three drive columns in three spatial directions (x, y, z) along a welding head, which is arranged parallel to the workpiece support for a product to be manufactured, with a nozzle in the form of a powder nozzle or a wire nozzle, wherein each drive column allows a path movement of the workpiece support via tension-compression-struts connected thereto and a mass balancing by means of corresponding counterweights, wherein the counterweights (9) ensure mass balancing at speeds of > 200 m / min and accelerations of 50 m / s or more during operation.

15. The method according to claim 14, characterized in that an oscillating operation is used to form curves, paths and / or cavities.

16. The method according to claim 14 or 15, characterized in that a support plate for a welding head is arranged above the workpiece support.

17. The method according to claim 16, characterized in that the support plate is held immovably and the workpiece support is moved individually in the three spatial directions x, y, z.

18. The method according to one of the claims 14 to 17, characterized in that amorphous and / or crystalline material compositions are used for manufacturing the product.