DE19903436A1 - Precision laser welding or sintering producing three-dimensional objects, first forms an envelope, then fills it e.g. with foamed metal, for rapid manufacture of extremely diverse complex shapes including clad turbine blades in ceramic - Google Patents

Abstract

An envelope is constructed from a material in layers, using the cited techniques. It is filled by the same, or one or more different materials. An Independent claim is included for equipment carrying out the method, consisting essentially of a power laser moved freely, relative to a construction platform. Preferred features: During or after filling, a solid core is formed inside. The filling is a melt introduced under pressure, setting afterwards. The core is a foam. Filling is melted-on by induction or resistance heating. It is alternatively sintered or polymerized. The intervening space of a double-walled envelope is filled. With the material in the cavity, the molding is formed by polymerization, sintering or melt setting. The double walled body is made in at least two parts. On the inner wall, laser beam precision weld-coating produces bridging sections. The envelope is made from a powder or powder mixture by laser beam precision weld coating. The powder or powder mixture is selected for its influence on mechanical, thermal, electrical, magnetic or physiological characteristics. Its composition is varied to permits local modification of these characteristics. An organic compound causing degassification on heating is included in the core. The envelope surrounds a higher-melting supportive material. The laser is similarly used to construct a supportive structure inside. Filling and/or deaeration openings of the envelope are closed using the same welding technique. During layered construction, local mechanical operations are carried out. The envelope is a metal or alloy optionally containing hard material, or a ceramic. The envelope minimum thickness is 0.1 mm. The laser beam passes through a head with integral gas and powder supply, the latter having a powder layer thickness dosing unit. A mobile cutting and/or erosive unit is employed.

Description

The invention relates to a method for manufacturing three-dimensional molded body from at least partially fusible material in which the laser beam precision sion deposition welding process or selective laser is applied internally. With the invention gün prototypes of moldings or Small series of such molded articles are produced with molded bodies with filigree contours relative can be easily and precisely manufactured.

With the laser beam precision cladding process various components have been full constantly or with worn or partially zer disturbed components, this by complete materi Al order made in whole or the wear NEN or missing parts replaced accordingly. Here the laser beam and / or the workpiece was under Use of 3D CAD data sets in at least three Controlled axes and a layered structure Melt powders made like this too others fall under the term rapid prototyping lent procedure is carried out. The various materials can be used however melted under the influence of the laser beam must be so that in the finished workpiece or Component tight structures, high strength and high Precision can be achieved.  

However, the use of this method is specific suitable materials limited so that the Properties of such components only in certain Limits can be influenced accordingly.

Another major disadvantage of this method is that relatively low coating rates can be achieved and therefore the time for Production of a component using this process is relatively high. Only layers can be used a limited layer thickness and with the laser beam only traces in the mm range are generated in one layer be so that the laser beam at larger dimensions component in one layer of single tracks.

The laser beam precision cladding process is z. B. by E. Beyer, K. Wissenbach in "Surfaces treatment with laser radiation ", Springer-Verlag Ber lin, Heidelberg, New York, 1998.

For certain components and here in particular highly stressed components are different Materials or materials used to get the to achieve desired properties and on the other the material costs are kept low accordingly So it is common in many cases, a relative inexpensive material or such a material provided with a coating to the desired achieve th surface properties. So be for example hard materials such as various carbides, containing powder mixtures used and by means known cladding process or by metal spray on a basic body from an essential cheaper and possibly also with others  Properties afflicted base body applied. However, liability problems often arise here, chipping when used as intended can lead and therefore a correspondingly short re lifespan or corresponding usage restrictions are recorded.

The order of such is particularly problematic Coatings on various metals, such as Alumi nium and magnesium working under atmospheric conditions are extremely reactive, so that out on the surface formed oxide layers the adhesion of additional Affect coatings particularly badly.

Such high-performance coatings cannot either can be applied to any base body, because As a rule, certain surface structures for this required are. Coatings can also not be applied to all materials and also Composite materials or composite materials where one made from at least two different materials existing base body should be coated, can in many cases have so far not been available be put.

Furthermore, this is under the term "Rapid Proto typing "falling selective laser sintering known. This is a metal or ceramic powder in one relatively thin layer applied evenly and then selectively applied the powder layer sintered. That is, a laser beam of a certain one predetermined contour following the applied pulse layered and the powder through the energy influence of the laser beam in these areas is sintered, whereas the areas that are not  are influenced by the laser beam unsintered stay. So a corresponding three-dimensional Be built up layer by layer. A sol cher body can be made from various powders or Powder mixtures are produced, the ver different metals, metal alloys or Ke Find ceramic powder.

For the desired deflection of the laser beam, who usually used 3D CAD data.

It is therefore an object of the invention, by means of known Laser beam precision surfacing or selective laser sintering technology three-dimensional shape body inexpensive, in a short time and given if under specific influence of certain own to be able to manufacture.

According to the invention, this object is achieved with the features of claim 1 solved. Advantageous design shapes and developments of the Lö according to the invention solution, can with the in the subordinate claims Chen contained features can be achieved. Advantage the process according to the invention for the manufacture development of prototypes and for small series production be used. The manufactured according to the invention Shaped bodies can advantageously be cast, sprayed, or die casting molds as well as molds for the manufacturers development of foam bodies can be used.

Another favorable area of application is for Shaped body, in which an enveloping body made of titanium a core of magnesium, e.g. B. for turbine blades is produced and here the particularly cheap Properties of these metals exploited and the ver  work problems can be avoided.

According to the invention, the procedure is such that the well-known laser beam precision cladding using 3D CAD data that at least the Specify the outer and inner contour of an envelope, such a layer is built up. For this will taking into account the desired surfaces properties for the molded body, a material in Powder form used, at least partially is fusible. In such a powder components may also be included, such as wise certain hard materials, with those with the laser temperatures not reachable in the beam get molten phase and not opened be solved and by other powder components in the Solidification of the molten phase included can be.

By laser beam precision cladding can envelopes with thin walls, the mini times 0.1 mm, built up layer by layer with filigree inner and outer contours or overhangs and undercuts on the envelope be formed.

To reduce the manufacturing requirements Chen expenditure of time for such three-dimensional shape body is subsequently filled, whereby on the one hand the envelope material or at least one additional material can be used for the filling can.

Conveniently, at or after the A solid core is filled with the filled material  be formed inside the envelope, the fills all cavities or parts thereof.

So the enveloping body with a molten The material is filled and the core solidifies Melt are formed. In addition to the various other known casting methods, can be here Pressurization also indicated the die casting process be used to make particularly homogeneous and void-free To get cores.

The core can also be formed from a metal foam are used, here also known methods can be. Through a metal core The mass can foam for a so produced Moldings are reduced accordingly.

Another way to create one Metal foam that differs from the conventional The procedure is to fill before the melt in the shell an organic mate rial, for example a granulate or a powder fill a polymer, which by z. B. warming, the heat of the melt degasses, evaporates or reacts tiv gas is formed and thereby the released Cavities corresponding to gas in the solidifying material trains.

But it can also be done so that the front prepared envelope with a solid, for example filled powdered material and then by heating and melting or sintering the Core can be obtained. The corresponding Erwär mung can be used in conventional ovens, but also inductively or using an electrical resistance  be carried out. It can be enough that only the envelope from a ent speaking appropriate material and that filled material only by heat conduction and / or in connection with convection in the required Temperature ranges is brought.

With the method according to the invention, dop fur-walled envelopes are formed, which then for example, as a mold for production appropriate components can be used. Here the high variability has a particularly favorable effect, the possibility of training particularly delicate Contours and the possible thin walls of such Envelope advantageously. The one between the doubles Cavities formed in the walls can then be used filled materials and corresponding molded parts through polymerization, sintering or solidification Melt are produced. With different shapes such molded parts may be required To manufacture envelopes from at least two parts, so that a split form is provided that can.

A double-walled envelope can also be used be detected if the cavity between the two Walls filled with an insulating material is so that, for example, thermal insulation in Direction of the inside of the envelope is accessible.

Especially in the case of moldings which consist of more than one Material should exist, it can be cheap Manufacture envelope so that on its inner wall webs are formed in certain areas, that protrude into the interior, for example  to increase the strength or in certain areas to maintain an appropriate voltage regime or the hold of a ker formed in the envelope nes, due to a web contour-related clamp effect improve. Such bridges can be moved along the most axes or also spiral his.

As already mentioned at the beginning, for the manufacturer the envelope with the laser beam precision Deposition welding process a powder or a powder mix can be used, the selection of which is targeted influencing mechanical, thermal, electri shear, magnetic or physiological properties th of the finished molded article can be directed.

It is possible to use what is used Powder or a powder mixture during construction to vary the envelope so that they correspond the properties of the finished molded article locally targets can be influenced. Certain areas could then, e.g. B. a higher elasticity, a bes sere thermal conductivity or other equivalent Have properties than in other areas chen of the finished molded body is the case.

To increase the strength of the finished molded article can be a suitable support body, for example be used in skeleton construction, around which the Envelope body using laser beam precision application welding is built up in layers and the after subsequently completely enclosed by the envelope material is. Such a support body should be advantageous made of a higher melting material than this Envelope material is exist. Should the support  body material, however, can be melted a corresponding alloying of the envelope material than be achieved. According to the respective geometry and dimensioning of such Support body locally targeted influence on the material and consequently also the properties of the finished one Shaped body are taken.

Another example of a possible manufacture a molded body is inside the Envelope, simultaneously with the construction of the envelope with the laser beam precision cladding process ren to produce a form and / or support structure. So with the production of a mold structure in A cavity is formed inside the enveloping body the one that followed during training in the envelope remains hollow, so that this shape structure Take over core function in casting or sintering can.

Such a support structure can be similar, for example be trained like a truss and thereby the finished molded body, which has a core inside for example light and possibly also a material with relatively low strength has a high stability and at the same time mass reduction can be achieved.

As for the formation of the core inside the shell body at least one filling opening and given if additionally at least one ventilation opening is required, this should be done after training of the core again with the laser beam precision opening Tragschweißverfahren be closed, so that a maintain dense and homogeneous surface on the molded body  can be.

The method according to the invention can advantageously be used mechanical processing steps combined by be performed, which are different machining processes, such as B. milling, but can also be eroding processes. The Kombina tion of these different procedures is special useful when certain areas of the molded body must be machined on the finished molded body and here also on the envelope only with difficulty or not at all are more accessible.

For the manufacture of the envelope, the ver various metals and alloys (e.g. cobalt or hard nickel alloys) are used, wherein known hard materials can also be contained in these can.

For the formation of the core inside a sol Chen envelope can also be the most diverse Metals and alloys as well as the various Ke ramiken, cellulosic materials or Plastics are used. Here, for the Formation of the core next to the envelope material also such materials are used, the Melting or sintering temperature below the melting point temperature of the envelope material.

In the event that the core is made of the envelope material or a higher melting material than this Envelope material is intended to exist, the envelope can body when filling the corresponding melt or cooled from the outside when melting.  

As already mentioned, the enveloping body can be produced with a minimum wall thickness of 0.1 mm and a roughness depth R _z of 20 to 200 μm can be achieved, so that a corresponding reworking of the surface of the enveloping body can be dispensed with for many applications. Relatively inexpensive CO ₂ - or Nd: YAG lasers with a relatively low power below 1 kW can be used for laser beam precision build-up welding, so that the technical outlay remains limited, particularly with regard to costs.

Stand once for the production of a corresponding 3D mold data required for the corresponding molded body Available, more such moldings without further reproduced identically, which in particular in the manufacture of appropriate molding testify that need to be replaced at larger intervals is important.

However, the method according to the invention is also then particularly advantageous if the construction of a Shaped body is partially changed so that this Changes are taken into account relatively easily and are demented speaking changed new moldings very quickly can be asked, such as for certain prototypes that are used in test series finding is often required.

The solution according to the invention can also under Use of selective laser technology known knowledge is carried out internally, which is particularly advantageous if at least one envelope made of a ceramic material to be manufactured.  

Using the selective laser sintering process envelopes can also be produced that are not sealed Have structure, but the walls of such Envelope are also porous within certain limits, such porosity with both ceramics, such as can also be achieved with metals. Such a porous envelope can now correspond with a core material. Become such Core materials used, for example, for various fluid-absorbing properties have such finished moldings as Storage elements for such a fluid use Find.

But other materials, such as. B. zel materials containing lulose in such an envelope can be filled and such a shaped body then, e.g. B. can be used as a filter, with for example, a rough filtering with the porous envelope body and a fine filter with the filled core material can be achieved.

The moldings according to the invention can be compact Shape, d. H. as an almost full body through selective Laser sintering can be produced if that is too much not powder from the finished envelope remotely, but ver inside the envelope remaining powder melted by heating or is sintered, so that a whole from the same material of existing full molded body can be put.

Is with higher energies than with selective Laser sintered, so the envelope can, like known from selective laser sintering, through complete  layers of powder are produced, the layer-by-layer stabilization does not go through Sintering, but by welding the powder batches together kel can be achieved.

A molded body can also consist of an enveloping body is filled with a suitable powder in which the powder forming the core in the shell body sintered by hot isostatic pressing becomes. In this case, however, the envelope should have sufficient strength and pores or Openings for the necessary pressurization exhibit.

The method according to the invention can be carried out with devices be carried out with a relative movement a laser beam in relation to a construction platform, on which the envelope is built up in layers should, at least in two orthogonal to each other aligned axes is possible. It should also be a Movement of the building platform orthogonal to the plane of the Construction platform or by means of a beam shaping unit the position of the focus point can be changed, here on known drives and beam guidance elements such as scanner mirrors can be gripped.

Especially when it comes to precision laser beam application should use the laser beam to weld of a laser processing head at least partially be performed. It can in the laser processing head both the powder feed and a gas leadership must be integrated. The gas supplied can be a times to promote the powder and to whose also act as a protective gas.  

But it can also, as has been the case with conventional systems selective laser sintering process, the powder from a Storage container by means of a squeegee, which is also the Layer thickness metering of a single powder layer can be applied in layers. This alternately turns into a powder layer applied and selectively certain areas this applied layer by laser radiation heat sintered or welded.

Such a device can also be supplemented by this be that in addition at least one cutting or an eroding unit is / are that also in at least two orthogonal to each other aligned axes can be manipulated so that ent talking edits at least partially fer term envelope can be made without a corresponding machine change with additional Time is required.

A machining unit or one Eroding unit can also be part of a Industrial robot or connected to one be, so that a high flexibility in the mechani machining on an envelope can be achieved can.

The invention is intended to be based on examples be written.

example 1

Parameters should be mentioned as to how a vane cell wheel can be manufactured with the invention. The envelope is manufactured using the laser beam precision cladding process. A powder consisting of 60 mass% WC / Co and 40 mass% NiBSi is used for the enveloping body and the enveloping body is produced according to the desired outer contour of the vane wheel with a CO ₂ laser that achieves a power of 3.5 kW. The relative speed of the enveloping body to the laser beam movement is approx. 250 mm / min and it is worked with a laser intensity in the beam spot of 1.5 × 10 ⁴ W / cm ² .

Argon is used as the conveying and protective gas.

The core of such a vane wheel is made from a NiBSi powder that is in the finished envelope has been filled. Mostly nickel Powder containing has an additional 1.5 mass% B, 2.3 Mass% Si and 0.25 mass% C. The formation of the Kernes can now by melting the powder at temperatures in the range of 1050 to 1150 ° C gene.

Example 2

For the production of a pump housing as aluminum Formed part, which as a single piece for experimental purposes in an engine should be used will be an envelope AlSi10Mg powder body using a Nd: YAG laser by laser beam precision order welding with an average wall thickness of made about 1.2 mm.

The envelope thus obtained is the same AlSi10Mg powder filled, here a melt  is used. The filling can be done in several Steps are carried out in stages. The The melting temperature of this material is 590 ° C.

The finished pump housing has a design locally different wall thicknesses, with large parts however, achieve wall thicknesses of around 10 mm. Out of it follows that with the inventive method Manufacturing time of such a pump housing compared the conventional laser beam precision order welding can be greatly shortened.

Claims (30)

1. A method for producing three-dimensional moldings from at least partially meltable material, welding by laser beam precision application or selective laser sintering, characterized in that an envelope is built up layer by layer by means of laser beam precision application welding or selective laser and then a cavity formed in the envelope is at least partially filled with the envelope material or at least a second material. 2. The method according to claim 1, characterized in that at or after Fill a solid core in at least one Cavity of the enveloping body is formed. 3. The method according to claim 1 or 2, characterized in that the core by Ein filling of molten material, according to the sen solidification is trained. 4. The method according to any one of claims 1 to 3, characterized in that molten Material pressurized into the envelope is filled. 5. The method according to any one of claims 1 to 4, characterized in that the core of ge foamed material is formed. 6. The method according to any one of claims 1 to 5, characterized in that in the envelope  by inducted material or by means of electrical resistance heating melted becomes. 7. The method according to claim 1 or 2, characterized in that the core from the filled material by sintering or polymeri station is trained. 8. The method according to any one of claims 1 to 7, characterized in that the envelope dop pelwandig formed between the envelopes cavity arranged in the walls and filled with the material in the cavity a molded part by Po lymerization, sintering or solidification of one Melt is formed. 9. The method according to claim 8, characterized in that the double-walled Envelope made of at least two parts is posed. 10. The method according to any one of claims 1 to 9, characterized in that on the envelope inner wall by laser beam precision opening support welded webs are formed. 11. The method according to any one of claims 1 to 10, characterized in that the envelope with a powder or a powder mixture Laser beam precision cladding applied is built. 12. The method according to claim 11, characterized in that a powder or  Powder mixture to influence me chanic, thermal, electrical, magneti shear or physiological properties det. 13. The method according to claim 11 or 12, characterized in that the composition of the powder or powder mixture during the Structure of the envelope for targeted local Influencing the mechanical, electrical, magnetic, thermal or physiological Properties is varied. 14. The method according to claim 1 or 2, characterized in that the core material that degasses when heated or a gas-forming organic compound is given. 15. The method according to any one of claims 1 to 14, characterized in that the enveloping body around a support body made of a higher melting Material is built. 16. The method according to any one of claims 1 to 15, characterized in that inside the envelope body through a form and / or support structure Laser beam precision cladding herge is posed. 17. The method according to any one of claims 1 to 16, characterized in that filling and / or Vents of the envelope after the Filled by laser beam precision application welding can be closed.   18. The method according to any one of claims 1 to 17, characterized in that during the shift point structure of the envelope locally targeted mechanical processing in some areas is carried out. 19. Method according to one of sections 1 to 18, characterized in that the envelope body a metal, an alloy or a hard metal or an alloy containing substances or a ceramic is made. 20. The method according to any one of claims 1 to 19, characterized in that for training the A metal, an alloy, a ceramic, cellulosic material or a plastic is used. 21. The method according to any one of claims 1 to 20, characterized in that with an envelope made of an iron, cobalt or nickel hard alloy tion with iron, aluminum, copper or egg another lower melting metal is filled, a molded body is produced. 22. The method according to any one of claims 1 to 21, characterized in that a molded body an envelope made of titanium, with egg a core is made of magnesium. 23. The method according to any one of claims 1 to 22, characterized in that an envelope with a minimum wall thickness of 0.1 mm is posed.   24. Device for performing the method according to one of claims 1 to 23, characterized, that a laser beam that is orthogonal in two axes aligned with respect to one another ner construction platform is deflectable and / or Construction platform in at least these two axes is movable; and the build platform be vertical movable and / or the focus position of the laser beam by means of a beam shaping unit can change, from above on the construction platform is aimed. 25. The device according to claim 24, characterized in that the laser beam over a laser processing head with integrated Powder and gas supply is performed. 26. The device according to claim 24, characterized in that a powder feed available with a powder layer thickness metering is. 27. The device according to one of claims 23 to 26, characterized in that at least one in at least two orthogonal to each other machined machining machining axes and / or eroding unit is / are available. 28. The device according to claim 27, characterized in that a laser beam guide processing unit, a machining and / or Eroding unit part of an industrial robot ters or connected to an industrial robot is / are.   29. Use of a shaped body produced with a method according to claim 1, 8 or 9 as Cast, die-cast, injection molded or foam mold. 30. Use of a shaped body produced with a method according to claim 1, 2 or 22 as Turbine blade.