DE102016224060A1 - Method for the additive production of a component with a supporting structure and a reduced energy density - Google Patents

Abstract

The invention relates to a method for the additive production of a component (10), comprising coating a production area (HF) comprising a component area (BB) and an overhang area (BB) with a layer (4) of a base material (2) for the component (10), selectively irradiating the device region (BB) of the layer (4) with an energy beam (3) at a first energy density, and irradiating the overhang region (UB) with a second energy density different from the first energy density, wherein the device region (BB) for the component (10) is irradiated in front of the overhang area (BB), and wherein the irradiation of the overhang area (BB) is carried out in such a way that the corresponding base material (2) becomes a support structure (20) for supporting an overhang ( 5) of the component (10) is solidified.

Description

The present invention relates to a method for the additive production of a component, in particular a component with an overhang, which must be supported during the additive production with a support structure.

Generative or additive manufacturing processes include, for example, as powder bed processes, selective laser melting (SLM) or laser sintering (SLS), or electron beam melting (EBM). Laser deposition welding (LMD) is also one of the additive processes.

A method for selective laser melting is known, for example EP 2 601 006 B1 ,

Additive manufacturing processes (English: "additive manufacturing") have proven to be particularly advantageous for complex or complicated or filigree designed components, such as labyrinthine structures, cooling structures and / or lightweight structures. In particular, the additive manufacturing by a particularly short chain of process steps is advantageous because a manufacturing or manufacturing step of a component can be done directly on the basis of a corresponding CAD file.

Furthermore, the additive manufacturing is particularly advantageous for the development or production of prototypes, which can not or can not be efficiently produced, for example, for cost reasons by means of conventional subtractive or cutting methods or casting technology.

A well-known problem in the additive manufacturing of complex components is caused by support structures for supporting overhangs or undercuts. These support structures often require expensive base material and machine time, which significantly reduces the cost-effectiveness, in particular powder-bed-based additive processes. In these methods, in particular selective laser melting, however, these support structures are unavoidable from a critical angle or overhang area.

It is therefore an object of the present invention to provide means by which the structure of the support structures during the manufacture of the component can not be prevented, however, these support structures can be made much easier and more economical.

This object is solved by the subject matter of the independent claim. Advantageous embodiments are the subject of the dependent claims.

One aspect of the present invention relates to a method for additive production of a component layer-by-layer along a construction direction, comprising coating a manufacturing area comprising a component area and an overhang area with a layer of, in particular powdered, base material for the component, selectively irradiating a component area of the layer with an energy beam at a first energy density and irradiating the overhang region with a second energy density different from the first energy density, wherein the component region for the device is irradiated in front of the overhang region, and wherein the irradiation of the overhang region is performed such that the corresponding base material is solidified to a support structure for supporting a built-over overhang of the component.

Said regions preferably designate (lateral) regions of the powder bed of the base material for the component.

The "component region" is preferably a lateral region, for example viewed in a plan view of a production surface of the component. The component region is preferably predetermined by the individual geometry of the component, or already known in the form of design data, in particular CAD or CAM data, before the actual structure for each individual layer of the component.

In the present case, the "overhang area" preferably also describes a lateral area, for example viewed in a plan view of a production area of the component, which, however, is not (yet) to be irradiated with the energy beam in the layer currently to be irradiated or exposed, but corresponding to the geometry of the component - only in a later construction or manufacturing step.

In one embodiment, the overhang area, viewed in projection on a plan view of the production area, represents a partial area of the production area.

For example, the additive construction of a single solid-state layer, comprising a corresponding coating and subsequent irradiation, may be designated by the said construction step.

The "production area" may be a surface of the construction platform and / or a surface of an already irradiated and constructed part of the component, or else a surface of the powder bed.

In one embodiment, the second energy density is selected and the irradiation of the overhang region is carried out such that the overhang region per unit area can be irradiated at least twice as fast as the component region.

In one embodiment, the device area is layered, i. irradiated in each layer in front of the overhang area.

In one embodiment, the overhang region is irradiated for the first time after the component region has already been built up to a predetermined assembly height and / or up to an overhang.

The "predetermined construction height" is preferably a multiple of a single layer thickness of pulverulent base material. In the case of selective laser melting and / or electron beam melting, the layer thickness is preferably between 20 μm and 50 μm.

In one embodiment, the predetermined construction height is between 120 μm and 150 μm, in particular 120 μm.

In one embodiment, the layer thickness of each layer of the base material is between 30 .mu.m and 50 .mu.m, in particular 40 .mu.m.

The energy density can be one energy per area and / or one energy per time.

In particular, by the differently selected energy density of the irradiation of the component area (selective irradiation) and the overhang area (irradiation with low energy density), in particular a support structure can be constructed more process-economical, that is substantially shorter time, for example, to the structure of the corresponding structures up to the predetermined construction height at least the overhang area only needs to be exposed or irradiated once.

The predetermined assembly height is preferably selected such that the correspondingly dimensioned and reduced energy density when irradiating the overhang region causes the base material, which has hitherto been located in the overhang region or has been layered in it, to be solidified accordingly.

In one embodiment, the layers of the base material solidify in the overhang area by the single irradiation with the energy beam to a porous support structure. This structure is preferably sufficiently strong to suitably support the later to be built overhang of the component.

Due to the fact that, according to the method presented, the base material in the overhang area is expediently solidified to form the support structure but may not be completely remelted, this may possibly be recycled after a subsequent removal of the support structure, in particular by mechanical breaking or knocking off.

In one embodiment, a geometry of the component to be built at least up to the predetermined construction height is free of overhangs.

In one embodiment, the energy beam is a laser beam.

In one embodiment, the energy beam is an electron beam.

In one embodiment, the support structure has structural defects, such as pores.

In one embodiment, the second energy density is chosen smaller than the first energy density.

In one embodiment, the second energy density is set by defocusing the energy beam or by offsetting the build platform along a buildup direction for the additive manufacturing. According to this embodiment, the energy density preferably corresponds to a spatial energy density. The said defocusing accordingly results in a greater focus on the powder bed and accordingly a decreased energy density.

In one embodiment, the second energy density is greater than the first energy density. This embodiment can be set, for example, by an increased irradiation power of the energy beam, in particular laser power, compared to the first energy density.

In one embodiment, the irradiation of the overhang region, relative to the selective irradiation of the component region, is set or carried out by an increased scanning speed and / or an increased track spacing when the individual irradiation vectors are irradiated. According to this embodiment, the energy density preferably corresponds to a temporal energy density.

In one embodiment, the overhang area is not irradiated after each coating operation of the manufacturing surface or manufacturing surface. In other words, the overhang area, for example, only after every second or irradiated third and correspondingly more coating operations.

In one embodiment, the overhang area is irradiated only every other fifth layer, in particular every third layer.

In one embodiment, both the focus is increased, for example by defocusing, and the scan speed and / or the track pitch are increased. According to this embodiment, the laser power can then also be increased, without having to reckon with a remelting of the powder in the overhang area.

In one embodiment, after reaching an overhang or overhanging region along a mounting direction of the component, the component is constructed by alternately coating the production surface with the base material and selectively coating both the component region and the overhang region. This embodiment corresponds to the usual mode of additive production, wherein the overhanging structure of the component layer by layer, a solidification of the powder in the overhang area is required. However, the energy density according to this embodiment is in the overhang area, i. H. for powder, which is to be built up to the support structure, still as described against the irradiation of the powder provided for the component lowered or lowered.

In one embodiment, during the additive construction, in particular the support structure and the component between the support structure and a component structure of the previously constructed or manufactured component, a safety area is additively constructed or provided, in which the corresponding base material layer has, for example, an energy density according to the irradiation of the component area, as described, is irradiated. Preferably, the security area is irradiated in front of the component area.

In one embodiment, the support structure is interlocked with the described security area during the additive construction. The toothing is used for simplified separation of the finished component from the platform or a corresponding "support" by force, such as breaking. Canceling can be a practical solution, even if the break points usually need to be reworked.

Furthermore, such a toothing after construction allows better visibility of the contours of the component relative to the support. This is particularly advantageous in post-processing steps, which are almost always required in additive manufacturing.

• 1 zeigt ein Schema, welches die Bestrahlung einer oder mehrerer Pulverschichten andeutet.
• 2 zeigt ein Schema entsprechend 1, wobei ein Fokus eines Energiestrahls relativ zur 1 verändert wurde.
• 3 zeigt eine schematische Schnitt- oder Seitenansicht eines auf einer Bauplattform aufgebauten Bauteils mit einem Überhang.
• 4 zeigt ein schematisches Flussdiagramm mit erfindungsgemäßen Verfahrensschritten.

Further details of the invention are described below with reference to the figures.

• 1 shows a scheme that indicates the irradiation of one or more powder layers.
• 2 shows a scheme accordingly 1 , wherein a focus of an energy beam relative to 1 was changed.
• 3 shows a schematic sectional or side view of a built on a construction platform component with an overhang.
• 4 shows a schematic flow diagram with method steps according to the invention.

In the exemplary embodiments and figures, identical or identically acting elements can each be provided with the same reference numerals. The elements shown and their proportions with each other are basically not to be regarded as true to scale, but individual elements, for better presentation and / or better understanding exaggerated be shown thick or large.

The 1 to 3 each indicate process steps of the present method.

The 1 and 2 suggest means to reduce the energy density of an energy beam, with which a powder bed for the additive structure is irradiated, for example, is applied in a selective laser melting with a laser. 3 On the other hand, indicates process steps of the additive production of a component.

1 shows a construction platform 1 , On the building platform 1 is a powdery base material 2 arranged. Accordingly, the method described is preferably a powder bed-based process, for example selective laser melting, electron beam melting or selective laser sintering. The base material is preferably selected for a component made of a high-temperature-resistant material.

A corresponding component 10 is at least partially in 3 (see below).

The dashed line in 1 indicates a production area (not explicitly marked). The said production area is covered with an energy beam 3 irradiated. The energy beam may be an electron beam, but preferably a laser beam.

If the energy or the energy density of the laser beam is sufficient, the powder on the substrate plate or build platform 1 to melt, a solid state layer for a component by melting the powder and subsequent solidification is produced in the known manner.

The stated energy density can be a first energy density.

A diameter of the focusing energy beam 3 D1 corresponds to the production area.

2 shows a similar situation of in 1 irradiation process described, but in contrast to 1 , the construction platform 1 was increased, and accordingly the energy density of the energy beam 3 which hits the production area, has been reduced or decreased. Accordingly, the diameter of the energy beam becomes 3 in the working plane in 2 effectively magnified or the energy beam 3 almost defocused.

The energy density mentioned in the previous paragraph can be a second energy density.

Accordingly, the diameter D2 of the focus of the energy beam 3 directly on the powder bed of the 2 illustrated situation greater than D1 (see. 1 ). The dashed horizontal line in 2 merely indicates the position of the manufacturing surface before "defocusing".

A similar effect as the described defocusing can be caused by a dislocation of the build platform 1 along a construction direction (see upwardly directed arrow Z in 2 ) are effected.

Instead of increasing the powder focus or "spot diameter" via the means described, or in this way changing the energy density for solidifying base material, the parameters of the laser power, the track spacing and the scanning speed can also be changed, for example.

Increasing the track pitch and increasing the scan speed also effectively reduce energy plotted into a bed of powder per area or per time. It may also be an irradiation power, for example a laser power of the energy beam 3 may be increased or decreased, for example, to solidify powder or base material of a lying deeper in the powder bed area, but preferably not necessarily melt. A deviation of the laser power from an optimized operating point can be used in the same way according to the present invention in order to cover the base material in an overhang area (cf. 3 below) in such a way that it sufficiently supports an overhang.

In other words, the aim of the present invention is to increase productivity, wherein the material is further preferably remelted or at least solidified. By increasing the scan speed and the track pitch, the process or setup times are preferably shortened.

The described melting or welding process is less stable and produces significantly more pores and defects. In a supporting structure, however, this can be accepted to a certain extent.

By changing the energy density, as described, it is preferably made possible to screen or irradiate an area in the shortest possible time with the energy beam.

3 shows a schematic side or cross-sectional view of a component 10 which at least partially on the building board 1 was built.

The component is preferably intended for use in a turbomachine, preferably in the hot gas path of a gas turbine. The component is preferably made of a nickel-base and / or superalloy, in particular a nickel- or cobalt-based superalloy. The alloy may be precipitation hardened or precipitation hardenable.

According to the invention, the component 10 layer by layer by means of selective laser melting or selective laser sintering or electron beam melts. For this purpose, in a first step, a powder layer 4 with a layer thickness SD on the component plate 1 , for example by conventional methods applied. The layer thickness SD is, for example, between 20 .mu.m and 50 .mu.m, particularly preferably 40 .mu.m (see method step a) in FIG 4 ).

Subsequently, the base material 2 in a component area BB selectively irradiated according to the component geometry by appropriate parameters, melted and solidified to the structure of the component 10 whereas the base material or powder is not irradiated in the overhang area UB.

The presentation of the 3 in particular already shows a situation in the base material according to the geometry of the component 10 already melted and solidified accordingly. In a component area BB (compare right lateral side in 3 ), the base material was completely melted or remelted by means of the described energy beam to the structure of the component 10 to build. The entire component 10 is melted with the parameters that provide a structure that meets the quality requirements of the component. As a rule, a high density is required here.

The component 10 According to the invention is constructed in particular by alternately coating with base material and solidifying the same up to a predetermined height AH along the direction Z. In each layer up to the predetermined construction height AH are both base material 2 for the support structure 20 as well as for the component 10 exposed. The base material 2 for the component 10 However, according to the invention before that base material 2 for the porous support structure 20 exposed. The porous support structure is exposed or irradiated only after every second, third or fourth coating. The exposure (scanning) of the component surface in front of the surface for the porous support structure makes sense, since a "fresh" powder bed is available for the component in each layer. The spatters produced during the exposure of the support structure do not contaminate the powder surfaces that have to be melted for the component.

The predetermined assembly height AH preferably corresponds to that height, according to which the base material 2 in the overhang area can be solidified by an exposure process (and in the component area, preferably with multiple exposures).

The predetermined assembly height AH is preferably between 100 .mu.m and 150 .mu.m, in particular 120 .mu.m (a two- or multiple times the layer thickness of component 10 ). Accordingly, the predetermined construction height, for example, about three times the described selected layer thickness SD of the layer 4 , This has the consequence that the base material in the overhang area UB, which for the support structure 20 is intended to be irradiated or exposed only after every third layer application. This can build-up or machine time in the additive production of the component 10 be saved.

According to the invention, however, it is possible to deviate from these values. For example, the predetermined assembly height AH can also be ten times the layer thickness SD.

The modified or second energy density is preferably selected in such a way and the irradiation of the overhang area UB is carried out such that the overhang area UB per unit area is irradiated at least twice as fast as the component area BB. This irradiation mode preferably allows solidification of the base material 2 in the overhang area such that a supporting, possibly porous support structure 20 arises. The support structure 20 may accordingly have structural defects, in particular pores.

From reaching an overhang 5 along the construction direction Z of the component 10 , from which this case simultaneously extends into the overhang area UB, the powder layers in the component area BB as well as in the overhang area ÜB are irradiated in layers (jointly).

In 3 the construction height is characterized only by chance where the overhang is 5 of the component 10 begins to extend along the body direction Z. Of course, it can also be provided that the overhang 5 considered a component in the direction of construction Z until much later than the described predetermined construction height forms.

In 3 is further shown that in the overhang area ÜB between the structure of the component 10 and that of the support structure 20 a security area 15 is provided. The security area 15 exists, as well as the component 10 , preferably from completely molten and solidified base material. The security area 15 is preferably still provided as a security or processing area.

The security area 15 preferably extends along a lower edge of the overhang 5 of the component 10 , The security area 15 establishes contact with all overhang areas that need to be supported. The thickness of the security area is specified in x layers below the component boundary (eg 10 layers before a component overhang is to be exposed in a certain area) must be provided by porous support 20 on security area 15 change). The security area 15 is no longer manufactured with maximum productivity, but has comparable parameters to the component 10 (in each case the same layer thickness SD). The exposure order is adjusted here, so the security area 15 in front of the component 10 is exposed and thus can fulfill the supporting function.

Alternatively to the representation of 3 can the security area 15 with the support structure 20 be interleaved during additive construction (see dashed steps in FIG 3 ).

4 shows a schematic flow diagram, which indicates the described method steps according to the invention. As above described, the process step a), the coating of a manufacturing surface RF, comprising the component region (BB) and the overhang region ÜB, with a layer 4 a base material 2 for the component 10 ,

Process step b) describes the selective irradiation of the component region BB of the layer 4 with the energy beam 3 at the first energy density.

Process step c) describes the irradiation of the overhang region UB with the second energy density, wherein the component region BB for the component 10 is irradiated before the overhang area UB, and wherein the irradiation of the overhang area UB is performed such that the corresponding base material 2 to a support structure 20 for supporting an overhang to be built up 5 of the component 10 is solidified.

The invention is not limited by the description based on the embodiments of these, but includes each new feature and any combination of features. This includes in particular any combination of features in the patent claims, even if this feature or combination itself is not explicitly stated in the patent claims or exemplary embodiments.

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

• EP 2601006 B1 [0003]

Claims (14)

Method for the additive production of a component (10) in layers along a construction direction (Z), comprising the following steps: a) coating a production area (HF) comprising a component area (BB) and an overhang area (UB) with a layer (4) of a base material (2) for the component (10), b) selectively irradiating the component region (BB) of the layer (4) with an energy beam (3) at a first energy density, c) irradiating the overhang area (UB) with a second energy density different from the first energy density, wherein the component area (BB) for the component (10) is irradiated in front of the overhang area (UB), and wherein the irradiation of the overhang area (BB) is performed such that the corresponding base material (2) is solidified into a support structure (20) for supporting an overhang (5) to be built up of the component (10). Method according to Claim 1 , wherein the second energy density is selected and the irradiation of the overhang region (UB) is performed such that the overhang region (UB) per surface unit is irradiated at least twice as fast as the component region (BB). According to the method, Claim 1 or 2 , wherein the component area (BB) is irradiated in each layer in front of the overhang area (BB). Method according to one of the preceding claims, wherein the overhang area (BB) is irradiated for the first time after the component area (BB) has already been built up to a predetermined construction height (AH). Method according to one of the preceding claims, wherein the support structure has structural defects, for example pores. Method according to one of the preceding claims, wherein the second energy density is smaller than the first energy density. Method according to Claim 6 , wherein the second energy density is adjusted by a defocusing of the energy beam (3) or by a displacement of the construction platform (1) along a construction direction (Z) for the additive production. Method according to one of the preceding claims, wherein the second energy density is greater than the first energy density. Method according to one of the preceding claims, wherein the irradiation of the overhang region (BB), relative to the selective irradiation of the component region (BB), is carried out by an increased scanning speed and / or an increased track spacing during the irradiation. Method according to one of the preceding claims, wherein the overhang region (UB) is not irradiated after each coating process of the production surface (HF). Method according to one of the preceding claims, wherein the overhang area (BB) is irradiated only every second to fifth layer, in particular every third layer. Method according to one of the preceding claims, wherein the component (10) in layers along the mounting direction (Z) from reaching the overhang (5) by alternately coating the manufacturing surface (HF) with the base material (2) and selectively irradiating both the component region (BB) as well as the overhang area (UB) is constructed with the same energy density. Method according to one of the preceding claims, wherein during the additive construction between the support structure (20) and a component structure (10) a safety area (15) is constructed, wherein the safety area (15) is irradiated in front of the component area (BB). Method according to Claim 13 wherein the support structure (20) is interlocked with the security area (15) during the additive construction.

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