WO2018166555A1

WO2018166555A1 - Method and apparatus for wired additive manufacturing

Info

Publication number: WO2018166555A1
Application number: PCT/DE2018/100144
Authority: WO
Inventors: Igor Haschke
Original assignee: Scansonic Holding Se
Priority date: 2017-03-14
Filing date: 2018-02-19
Publication date: 2018-09-20
Also published as: DE102017126354A1; DE102017112849A1

Abstract

The invention relates to a method and an apparatus for the wired additive manufacturing of shaped bodies (5) built up in layers. The additive construction of the shaped body (5) takes place by means of a plurality of individual wires (4) that are arranged alongside one another in a substantially parallel manner and form a wire pack, said individual wires (4) being conveyed into the region of a welding zone each with an individual wire infeed and being pressed against the surface (7) of the shaped body in an uninterrupted manner under mechanical preloading. Each particular shaped-body layer (6) is formed in the welding zone with the wire materials being melted and deposited. The method and the apparatus for carrying out the method ensure high process stability of the wired additive shaped-body production together with high efficiency.

Description

Method and apparatus for wired additive manufacturing

The invention relates to a method and a device for the additive production of a molded body made up of individual shaped body layers by melting and depositing wire-shaped materials by means of an energy beam, preferably a laser or electron beam.

For the additive production of moldings - often referred to as 3D printing - various methods have established, u. a. the known from the welding process, in which a consumable welding wire is continuously tracked via a wire feeder.

The additive production of moldings by means of such wired methods is carried out in a known manner in a plurality of molded body layers on a printing platform or on the already finished molded body layers. The wire-shaped material is conveyed by means of a wire feeding device known from welding technology into the region of the welding zone at the spot of the energy beam on the shaped body surface, the wire material changing into the molten state as a result of the energy input at the wire tip. After contact of the molten material with the body surface, the surface forms in the region of

Welding zone from the weld metal, which is part of the molding after its solidification. Due to the relative movement of the molded body relative to the device for additive manufacturing, the individual molded body layers are formed from the weld metal.

However, the known wired additive manufacturing methods have the disadvantage that the deposition rate and consequently the speed of the molding structure are limited by the wire diameter itself. In addition, it is disadvantageous that the height of a shaped body layer can not be arbitrarily increased with regard to the stability of the molten metal weld.

Increasing the application rate is possible by using bands instead of wires. Such a band welding method is known from

DE 10 2010 010 148 A1: A band-shaped bearing material is melted by means of a laser and applied to the surface of a component to be coated. This leads to a significant increase in order performance compared to single-wire welding.

Through the use of bands instead of wires, the order rate can indeed be significantly increased in the additive manufacturing, but in view of the required dimensional accuracy in near-net shape 3D printing tapes have proved disadvantageous because the shape of the band with its fixed geometry to the continuously changing geometry is not possible in the additive construction of moldings. In addition, it can lead to tilting of the supplied tape in the construction of juxtaposed molded body layers.

From DE 10 2016 003 468 A1, a device and a system for additive production using a high-energy source and a hot wire are also known, according to which moldings can be produced additively by melting several individual wires. A similar build-up welding process describes US 2013/0213942 A1. A disadvantage of this method is that high additional expenses are required to ensure the exact positioning of the wires in relation to the molded body or to the workpiece and to avoid process variations during melting of the individual wires.

The object of the invention is to provide a method and a device for wired additive production of moldings, which enable a process-stable, near-net shape molding production with high build-up rate.

This object is achieved by the method and apparatus having the characterizing features of claims 1 and 8, respectively; Advantageous developments of the invention will become apparent from the claims 2 to 7 and 9 to 10.

According to the invention, in the case of the wired additive production of a shaped body composed of individual shaped body layers, a wire bundle of a plurality of individual wires arranged parallel to one another preferably combing or brushing is conveyed by means of a wire feed device into the region of a welding zone, wherein the wire feed for Each individual wire in the wire package is individually controllable. In other words, the individual wires can be fed into the welding zone at different wire feed speeds. The Wire feed speed of the individual wires can be stopped completely if necessary; also a negative wire feed speed, ie the "retraction" of the individual wires, is feasible.Thus individually controllable wire feed is understood as the stopping and retraction of the individual wires.

The individual wires arranged substantially parallel next to one another in the wire bundle can have an angle deviation of the individual wires from one another of up to 10 °; Preferably, the individual wires are aligned completely parallel to each other.

The wire feed speed is set according to the invention so that each of the individual wires is pressed continuously under mechanical bias to the molding surface. The individual wires can have a circular or polygonal cross section depending on the application. In addition, it is possible to use different materials for the individual wires, wherein at least one of the wire materials consists of the material of the shaped body to be produced. The energy input for melting the individual wires and the shape body surface is carried out according to the invention by means of an energy beam, preferably a laser or electron beam, in the welding zone at the spot, d. H. at the impact surface, the energy beam on the body surface. In the region of the weld zone, after the molten wire materials have been deposited, the molten weld metal is formed by mixing with the molten molding material on the molding surface, which then solidifies to form a new molding body layer.

The device for wired additive manufacturing has a beam generator for generating the energy beam and the wire feeder with a plurality of individual wire conveyors. According to the invention, each individual wire in the wire package is assigned a single-wire conveyor for individual control of the wire feed of the respective individual wire and for mechanical pretensioning of the individual wires on the shaped-body surface. The production of the moldings takes place in a known manner on a printing platform on which the molded body is constructed, wherein it can be provided that the printing platform is moved after completion of each of a shaped body layer to the height of this shaped body layer in the vertical direction downwards. It can also be provided that the wire feeding device is tracked in height according to the layerwise growth of the shaped body while the printing platform is stationary.

The mold body is moved relative to the wire feed device in the plane of the molding surface during the additive manufacturing, for example, by the printing platform with the body mounted thereon translational or rotationally displaced at a constant height with respect to the wire feeder. Alternatively, the wire feed device can be moved together with the jet generator relative to the fixed molded body.

The realization of all movement possibilities can be achieved by implementing generally known multi-axis motion systems for processing machines.

By the method and the device, the wire-shaped additive molding production is made possible with high build-up rate: The shaped body layers of walls of the molding can be made in a transition with a corresponding width of the wire package - in contrast to the production with a single wire, which often requires material in multiple lanes To deposit material to fill the same area. The structure of moldings is therefore significantly faster and more economically feasible than comparable single wire method and

Flashbulbs.

Likewise, the individual control of the individual wires in the wire package ensures a stable manufacturing process. Tilting - as with strip welding processes - is avoided due to the flexibility of the wire package. The single-wire control also allows quick change in changing contours of the geometry of the molding. The width of the built-up shaped body layer can be adjusted by the disconnection and connection of the individual wires of the nominal contour of the shaped body; with curved component geometry, for example with bent moldings Perwänden, the individual wires in the outer radius range are promoted with higher wire feed speed in the weld zone than in the inner radius range.

As a result of pressing against the shape of the surface of the body, each individual wire bends slightly elastically over the free length of individual wire between the wire feed device and the shaped body surface, and in each case forms a spring element in this area. Due to the individually adjustable wire feed of the individual wires, the pressure force of each spring element or its preload can be controlled wire-specifically.

The particular advantage here is that the prestressed individual wires always rest against the shape of the body surface; Complex height measurements of the current shape body geometry, for example, to position the individual wire exactly in relation to the molding surface are avoided.

It can be provided that each individual wire has a free length of between 5 mm and 30 mm from the exit from the wire feed device to the shape body surface. By adjusting this free wire length ensures that each biased single wire has a sufficiently large elastic deflection to act as a spring element, while his

Deflection is sufficiently small to prevent lateral deflection of the individual wires in the wire package.

Advantageously, the individual wires are conveyed in the direction of the shaped body such that each of the individual wires touches the shape of the body surface at an angle of less than 70 °. A jamming of the individual wires by a steep hiring is prevented.

Furthermore, the individual wires arranged in a line substantially parallel in the wire pack can be aligned continuously perpendicular to the variable relative direction of movement of the shaped body, ie, the wire pack is preferably always oriented transversely to the relative movement of the shaped body during additive molding. This allows the deposition of the melted wire material in full width of the wire package. A mutual overlap of the individual wires is avoided. According to the invention, the device is rotatably mounted about an axis parallel to the individual wires. In normal, intended use this axis of rotation corresponds to the height axis of the device, ie the device is rotatable about the normal to the plane of the molding surface. The rotatory bearing is part of a multi-axis motion system, for example.

Furthermore, the wire feeder with comparable means - decoupled from the steel generator - be rotatably mounted about an axis parallel to the individual wires arranged axis.

This embodiment of the device makes it possible to align the individual wires, which are arranged in the wire package within a line substantially parallel to each other, obliquely to the relative direction of movement of the shaped body, wherein the orientation of the single wire line to the relative direction of movement is preferably changed in an angular range of 45 ° to 135 °. By varying the orientation of the wire bundle during molding production, the wire bundle width effective transversely to the direction of relative movement, i. H. the projection width of the wire bundle in the direction of relative movement, are changed, so that stepless changes in wall thickness in the production of moldings can be realized.

It may further be provided that the device comprises a scanner optics, which makes it possible to deflect the energy beam in a predetermined manner and to selectively position the spot of the energy beam on the molding surface. Known embodiments of such scanner optics are, for example, laser scanners with movable mirrors.

By means of such a scanner optics, the spot of the energy beam can, for example by sweeping back and forth sweep the wire package transverse to the relative movement and melt the individual wires punctually; there are spatially limited welding zones. By reducing the local melt pool volume, the accuracy of molding production is improved without sacrificing the application rate. An alternative - with less technical equipment - represents the application of a beam generator, which generates an energy beam with linear, over the entire width of the wire package reaching spot. In this embodiment, by varying the spot line width, the energy input or the size of the weld zone can be changed.

Furthermore, the beam generator can also be designed such that a plurality of energy beams can be generated, which impinge on the wire package in separate individual spots. This in turn allows the individual wires to melt at certain points.

The melting rate of the individual wires is also - in a known manner - controlled by position- and time-dependent change in the energy beam power.

The method with a pendulum energy beam can be performed so that the position-specific varying speed of the spot of the energy beam is compensated during the pendulum motion on the form body surface by adjusting the energy beam power. As a result, the optimal amount of energy in the welding zone is affected, depending on the position, so that uneven speeds of the spotlight due to pendulum or construction strategy are compensated. In particular, the power of the energy beam at the positions at which the wire bundle conveyed through the welding zone is melted can be controlled so that the path energy remains constant when sweeping the energy beam. In one embodiment of the invention, each individual wire is pre-bent by means of the wire feed device. For this purpose, the wire feed device has one or more wire bending units by means of which the individual wires are curved in the direction of the shaped body surface. By Vorrümmen means of wire bending units, the contact pressure or bias of the spring element formed by each wire element between the wire feeder and form body surface can be adjusted precisely.

The position of the wire tip can be detected as well as the wire bending radius by means of an optical sensor device; the wire feed speed is adjustable on the basis of these monitoring parameters. An optical sensor may, for example, be arranged coaxially around the energy beam.

By optical sensor devices is also the shaped body geometry, d. H. the height and shape of the individually constructed shaped body layers, measurable in situ during the molding process - for example in the light-section method. The geometric data of the thus determined actual geometry of the shaped body can be compared with default data and enable on this basis an adaptive process control.

Furthermore, the optical sensor device can be designed for detecting the heat radiation from the region of the weld zone, with the aid of which wire temperatures as well as surface temperatures of the molded article in the melt zone or adjacent to the melt zone are determined for the purpose of process monitoring or control. The time-dependent temperature changes, for example cooling rates, are also suitable for process control and regulation.

In one embodiment of the invention, only specific individual wires are melted by the energy beam. It is possible to convey the individual wires arranged at the edge of the wire bundle unmelted through the welding zone and to use them as supports for the molten weld metal. For example, the wire feed speed is chosen so high that the individual wires remain in the solid state when passing through the weld zone. The unmelted individual wires can furthermore be led away from the component again after contact of the shaped body in the region of the welding zone, for example in a cooling device or in an oscillating device. By targeted cooling or vibration excitation of the individual wires can be prevented that the individual wires enter into a cohesive connection with the weld metal or adhere to the existing molding. Alternatively, individual wires of non-fusible materials, such as ceramic wires, can be used.

The measures described for the edge wires of the wire package for supporting the molten metal in the welding zone can also be used for individual wires are used within the wire package. Thus, it is possible to add mold body walls with internal channels additively.

The printing platform can be heated to reduce distortion, to save on laser power or to clamp welding elements. The heating is preferably carried out adjustable; Wire temperature, weld temperature, cooling rate, mold surface temperature are suitable process parameters for controlling the heating of the printing platform. The use of the heated printing platform is conducive to the prevention of cracking and distortion and to the formation of a homogenous material structure.

The method and the device for wired additive manufacturing are described in more detail with reference to the following embodiments in conjunction with the schematic drawings. Show this

1: the device for additive manufacturing in perspective view, and Fig. 2: the device with a scanner optics in longitudinal section.

The individual wires 4 of the wire packet, which are arranged parallel next to one another in a line, are - according to FIG. 1 - conveyed by means of the wire feed device 3 to the shaped body surface 7 of the shaped body 5. The energy beam 2 generated by means of the beam generator 1 oscillates transversely to the relative movement 19 of the shaped body 5 back and forth (see double arrow). At the spot of the energy beam 2, the welding zone forms, in which the individual wires 4 are melted off. The molten one

Welded material solidifies to the shaped body layer 6.

The beam generator 1 according to FIG. 2 is a laser beam generator whose energy beam 2, ie the laser beam, is directed to the molding surface 7 via the scanner optics 10 with the collimation unit 14, the passive deflection unit 12, the focusing unit 13 and the active deflection unit 11. The wire feed device 3 has the wire bending units 9 (only one of the wire bending units 9 is shown in FIG. 2), wherein a separate wire bending unit 9 is provided for each individual wire 4, by means of which each individual wire 4 is individually conveyed and bent simultaneously. The wire feed device 3 is resiliently fastened to the suspension 8. After the melting of the individual wires 4 in the welding zone and the deposition of the molten metal to be welded, the shaped body layer 6 of the shaped body 5 is again formed.

The measuring radiation 17, ie light or thermal radiation, is detected by means of the sensor device 18 next to the scanner optics 10 and / or by the camera 16 within the scanner optics 10.

List of reference numbers used

1 jet generator

2 energy beam

3 wire feeder

4 single wire

5 moldings

6 shaped body layer

7 shape body surface

8 Suspension for wire feeder

9 wire bending unit

10 scanner optics

1 1 active deflection unit

12 passive deflection unit

13 focusing unit

14 collimation unit

15 camera focusing unit

16 camera

17 measuring radiation

18 sensor device

19 Relative movement of the molding

Claims

claims

1 . Method for the additive production of a shaped body (5) constructed from individual shaped body layers (6), wherein wire-shaped materials in the region of a welding zone are produced by means of a device comprising a wire feed device (3) and a beam generator (1) for generating an energy beam (2) at the spot of the energy beam (2) are melted and deposited on the mold body surface (7) to form a molded body layer (6), wherein the shaped body (5) at the same time relative to the wire feed device (3) in the plane of the molding surface (7) is moved, characterized in that by means of the wire feed device (3) a plurality of substantially parallel juxtaposed, forming a wire bundle individual wires (4) are conveyed individually for each individual wire (4) controlled wire feed in the region of the weld zone, wherein each of the individual wires ( 4) under mechanical pre-stress uninterrupted to the mold surface (7) is pressed.

2. A method for additive manufacturing according to claim 1, characterized in that each of the individual wires (4) from the exit from the wire feed device (3) to the shape Körperoberf surface (7) has a free length between 5 mm and 30 mm.

3. A method for additive manufacturing according to claim 1 or 2, characterized in that each of the individual wires (4) touches the shaped body surface (7) at an angle of less than 70 °.

4. A method for additive manufacturing according to one of claims 1 to 3, characterized in that the individual wires (4) by means of one or more wire bending units (9) are precambered.

5. A method for additive manufacturing according to any one of claims 1 to 4, character- ized in that the wire feed speed of predetermined individual wires (4) of the wire package is selected so high that these individual wires (4) pass through the weld zone unmelted.

6. A method for additive manufacturing according to one of claims 1 to 5, character- ized in that the spot of the energy beam (2) by means of a scanner optics (9). transversely to the wire package is moved oscillating and the power of the energy beam (2) is controlled so that the conveyed through the welding zone wire package is melted position-dependent or remains unmelted.

7. A method for additive manufacturing according to claim 6, characterized in that the power of the energy beam (2) at the positions at which the wire bundle conveyed by the welding zone is melted, is controlled so that the position-specific varying speed of the spot of the energy beam ( 2) is compensated by changing the power of the energy beam (2).

8. An apparatus for the additive production of a shaped body (5) made up of individual shaped body layers (6) by melting and depositing wire-shaped materials in the region of a welding zone at the spot of an energy beam (2) on the shaped body surface (7), the apparatus comprising a wire feed device (3). and a jet generator (1) for generating the energy beam (2), characterized in that the wire feed device (3) comprises a plurality of individual wire conveyors, by means of which a plurality of individual wires (4) arranged next to one another and forming a wire bundle can be conveyed into the region of the welding zone in which the wire feed of each individual wire (4) is individually controllable by means of the single wire conveyor associated with the respective individual wire (4) for mechanically biasing the individual wires (4) on the shaped body surface (7).

9. A device for additive manufacturing according to claim 8, characterized in that the wire feed device (3) has one or more wire bending units (9) for curving the individual wires (4) before their promotion in the region of the weld zone.

10. A device for additive manufacturing according to claim 8 or 9, characterized in that the device comprises one or more cooling devices for cooling the individual wires (4) or one or more oscillation devices for vibrational excitation of the individual wires (4).

- For this two sheet drawing -