DE102009024182B3 - Forming and removing mold or core during casting, e.g. of filigree structures, by forming mold or core containing hollow particles, to be collapsed under pressure after casting - Google Patents

Abstract

The present invention relates to a method for forming and removing a mold and / or a core during molding. The mold and / or the core are made from a mass containing hollow body. After casting and solidifying the potting compound for the production of the casting, the mold and / or the core is subjected to a pressure which leads to the destruction of at least a portion of the hollow body in the mold and / or the core. As a result of this destruction, the shape and / or the core collapse, so that their or their remainders can be removed from the casting in a simple manner. The proposed method allows the production and application of very dimensionally stable and filigree core structures that can be easily demolded.

Description

Technical application

The present invention relates to a method of forming and demoulding a mold and / or a core in the manufacture of a casting by means of molding, in which the mold and / or the core are made from a mass containing hollow bodies.

The molding is usually divided into casting into lost molds, which usually consist of a mineral, granular base material and a binder and other property-improving additives and are destroyed after each casting, and casting in permanent molds, which are reusable after a casting and with which up to many thousands of castings can be made. Both casting in lost molds and casting in permanent molds often uses lost cores to represent undercuts in the casting. Examples of casting processes with lost molds are sand casting and precision casting, for permanent molding gravity die casting and die casting.

The solidified mold material has a decisive influence on the cast quality of the lost molds as well as the lost cores. The main requirements of the molding material are good processability, sufficient strength and dimensional stability after molding of the mold, casting and solidification of the casting, good decay properties after casting, high imaging accuracy, sufficient gas permeability, negligible adverse interaction between Molding material and melt and problem-free reusability.

In particular, the mold or cores introduced therein must be stable until the molten potting material has solidified enough to be inherently stable. On the other hand, the binding of the grains in the molding or core material must then weaken so much that a complete removal of the material from the solidified casting is easily possible. The weakening of the bond is partly due to the thermal effect of the melt - as in the case of water-glass bonded cores - partly supported by external mechanical effects (eg vibrations), but partly also by chemical effects (eg dissolution of salt cores in water).

If the material of the mold or core remains solid even after casting, considerable effort is required to remove these solid residues. This generates additional manufacturing costs. However, an incomplete removal of mold and core materials can also lead to disruptions in the subsequent use of the casting and damage. So z. B. remains of water jacket sand cores of engine housings to disrupt the cooling circuit in later engine operation.

In technical practice, therefore, a compromise must always be found between the strength of the mold or of the core and their releasability. This leads in particular, but not exclusively in the case of cores, to restrictions in the presentation of very filigree geometries. Such thin-walled core and shape geometries on the one hand depend on a particularly high structural strength in order to withstand the mechanical loads during casting (buoyancy, kinetic effect of the flowing potting material melt, eg molten metal). On the other hand, especially with very thin-walled filigree core structures, which lie deep in the component, the demolding and the control of demolding can be very difficult. For example, thin-walled cooling channels, which have been represented by cores in castings, often have to be checked very expensively after demoulding by endoscopic methods or other tests (eg bodies pushed through the channels), which is very large and not always automatable effort is connected. For components with more complex, large-scale core structures made by cores, the difficulties in the removal of the mold and core material after casting even lead to such castings can not be manufactured process reliable. An example of this are heat exchanger components with internal sponge-like structures.

Another area of application in which there are problems with the disintegration of the cores, are very thick-walled cores, in which the heat of the cooling potting material is not sufficient to heat through the core and thus weaken the binder strength in the entire core volume.

The problems of tuning of form or core material strength and shaping behavior are particularly great for castings of light metal alloys (aluminum, magnesium), since the thermal energy of the melt is lower and thus the thermally induced weakening of bond bridges between the particles of the molding material not is so pronounced. In addition, castings of light metal alloys are more susceptible to shock loads due to the lower strengths and hardnesses of these alloys, and therefore the processes for removing molding material residues adhered to the casting can only be performed with lower forces and energies.

Furthermore, the above-mentioned difficulties with insufficient nuclear decay lead to the use of binders (eg based on resin) which, although exhibiting a good decomposition behavior, lead to significant emissions, which are caused, for example, by B. leads to odor nuisance of the employees of the foundries or the surrounding development of foundries. In contrast, binders which have no or significantly less emissions (eg waterglass-based binders), because of their excessive residual strength after cooling and the associated difficulties in demolding often can not be used.

State of the art

In order to ensure the requirements on the molding or core material with regard to strength and decay properties for the respective casting methods, various approaches for modifying or optimizing the core behavior are pursued according to the prior art.

One focus of the developments is the modification of the chemical composition of the basic materials, the binders and the special property-improving additives.

There is a wide range of molded and core materials with very different compositions. Quartz sand is predominantly used as refractory base material; chromite, zirconium and olivine sands are used for special applications. In addition, moldings on chamotte and magnesite, siliamite, corundum or in investment casting, in particular ceramic masses, etc. are used. The binders for the molding materials are organic (phenolic, urea, furan resins, ethyl silicate) or inorganic (eg water glass, cement, gypsum) nature and are produced synthetically or occur naturally (bentonite, molasses). Various binding principles are applied, for. As polycondensation reactions, hydrations, precipitation principles or sol-gel transformations. In addition, certain additives are often mixed in (eg sugar), which u. a. to influence the demolding behavior.

For the simultaneous optimization of the dimensional stability and the demolding behavior, for example, the composition of the binders and the type and composition of added auxiliaries are suitably selected, as described in US Pat DE 3139484 , of the DE 2923131 , of the DE 68922996T2 or the US1751482 is described.

The dissolution of the binder bridges between the particles does not necessarily have to be thermal or mechanical, chemical process variants are also known. So describes z. B. the WO92 / 06808 water-soluble cores based on polyphosphates, the US 1005136 calcined tricalcium silicate and binder in which the extraction by leaching in 50% of nitric acid, and the UK 1013938 Cores based on 30-70% by weight of titanium oxide, which dissolve in sodium hydroxide.

Other approaches to improve the demolding behavior of the cores are in special core coatings, as in JP 05212495A in the use of non-homogeneous core structures, e.g. B. of hollow cores, as in the JP 07178509 and the DE 2904415 described, or in layered cores, as in the DE 3826413 described.

Despite the various advances in the optimization of the molding or core material, the prior art technologies can accommodate various core geometries, such as those of the prior art. B. cooling ducts in cylinder heads or pistons for internal combustion engines are made consuming only in accordance with the technological requirements. Therefore, salt cores are often used here, in which the removal takes place with water flushing, such. B. in the DE 10305612 is described. However, problems arise here with regard to the complete salt removal, the necessary process times and possible corrosion phenomena. Especially in fine, deep and winding cores, the dissolution of the salt core takes a lot of time.

All of these mold or core materials and associated methods is based on the principle that compact particles of the refractory base material are connected to each other with the aid of the binder, often additional measures to increase the dimensional stability take place, in particular a mechanical compression. The removal of the core or the mold is then carried out by the thermal, chemical, mechanical or combined disruption of the bonds between the particles or by the chemical dissolution of the molding or core base material.

The cores used are not necessarily completely compact. Depending on the method or specifically, different porosities in the core or molding material can be set. For example, fired ceramic cores usually show porosity for precision casting. Furthermore, various aggregates may contain certain porosities. So z. B. the use of porous recycling aggregates (fly ash) known. The objective here is, inter alia, the reduction of heat dissipation and the production of lighter forms. The density of the fly ash is quite high at 2.2 g / cm ³ , the occurring internal porosity rather low.

An adjustment of specific porosities to improve the shaping behavior of cores is z. B. from the DE 2123632 in which a core material based on porous carbon is used. The DE 19939062 A1 describes highly porous airgel cores with easy demoldability, which, however, have to cure for a very long time with approx. 24 h. However, these approaches have in common that the cores have a compressive strength significantly reduced compared to the compact core material and are comparatively expensive to manufacture, especially requiring long production times. A further disadvantage of these methods is that, due to the porosities to be set, the procedure (eg foaming of the material) deviates significantly from the procedure which is usual in the foundry industry, in which the base or filling material is usually only binder mixed, placed in a mold and cured.

The DE 29 04 415 A1 discloses a method for casting long, hollow iron bodies. For this purpose, a hollow cylindrical core of carbon is used, which is removed from the interior of the casting after solidification by means of a vibration impact method or by a rotating grinding device.

From the DE 767 075 C For example, a method for producing hollow cores for metal casting is known. In this process, a core is made from a slurry which sinters at temperatures of higher melting metals and shatters as the metal fades.

The DE 1 758 532 A deals with ceramic hollow cores, which have a certain compressive strength and surface porosity. The cores are not removed after casting. Rather, the embodiment of the cores disclosed therein serves to produce a metal-ceramic composite hollow body. The surface porosity of the ceramic core serves to facilitate the formation of mechanical bonds between the ceramic core and the cast metal during the pouring of the metal and cooling.

The object of the present invention is to provide a method for the formation and removal of a mold and / or a core in the production of a casting by means of molding, which avoids the disadvantages of the prior art and the production and application both very dimensionally stable and filigree than Also allows large-volume form and core structures that are easily demoulded.

Presentation of the invention

The object is achieved by the method according to claim 1. Advantageous embodiments of the method are the subject of the dependent claims or can be found in the following description and the embodiments.

In the proposed method, the mold and / or the core are made from a mass containing hollow body particles. These hollow-body particles, hereinafter referred to only as hollow bodies, are preferably hollow spheres with diameters of <1 mm. Thus, the mass may, for example, be formed of a high-strength syntactic foam in which the hollow bodies constitute the hollow placeholders. The hollow bodies should have a sufficiently high compressive strength of preferably> 20 MPa, particularly preferably> 40 MPa. The mold and / or the core, after casting and solidifying a potting material to form the casting, is subjected to pressure which results in the destruction of at least a portion of the hollow bodies in the mold and / or the core, causing the mold and / or the core to collapse , d. H. undergoes a significant volume reduction. Thereafter, the remainders of the mold and / or the core are removed from the casting.

The demolding of the core or molding material is therefore essentially not by a disruption or by breaking up of binder bridges, but by a deliberately set collapse of the mold or core material containing the hollow body. Preferably, a proportion of ≥ 20% of the hollow bodies in the mold or core material should be destroyed.

This approach has several advantages over the prior art methods. Thus, the hollow body can be very well suspended in liquids and give the suspensions in forms in which they can harden. The production of complex shape or core geometries is thus easily possible. It can be based on core or molding processes that are common in foundries. The small dimensions of the hollow body of preferably <1 mm further allow a good accuracy of molding and high surface quality of the cores or molds. In addition, a high inherent strength of the hollow body leads to a significantly increased overall strength of the molding or core material in comparison to other porous core materials. Since isostatic compressive strength is known for many of the commercially available hollow bodies, it can be estimated at which mechanical loads the core or the mold collapses.

The collapse of the core or the shape is associated with a significant volume reduction. The removal of the mold or core remains is thus much easier possible, even by very small Openings to the casting surface, as in conventional mold or core materials with compact particulate fillers. For example, the remainders of the molding or core material can be removed from the casting by means of a simple water rinse.

In an advantageous embodiment of the method are used as a hollow body ceramic hollow microspheres or hollow glass microspheres. Such hollow spheres are available in different known compressive strengths and allow targeted destruction under the action of a suitably high pressure.

The compressive strengths of the hollow body used are of course chosen in the present process so that they withstand the pressure occurring during the casting of the casting. Furthermore, it is advantageous if the compressive strength of the hollow body and the binder used are coordinated so that in the later destruction of the hollow body and a force, in particular local bending and / or tensile forces are exerted on the binder structure, so that at the same time still damage to the binder bridges occurs. This collapses the whole structure and the core can be easily removed from the casting.

The mass for producing the mold or the core may, of course, in addition to the hollow bodies also contain massive particles or other materials. Preferably, the proportion of the hollow body in the mass in the range between 50 and 95% by volume, more preferably between 60 and 85% by volume.

In the proposed method, therefore, the shape or the core is significantly not formed from solid particles but from particles that are hollow body. The shape or nuclear decay results essentially not by a solubility of the particles to certain chemical reagents or by the reaction of the bonding bridges on thermal, mechanical or chemical external agents. The loss of stability of the core is thus not achieved by the loss of stability of the bond between the particles or by the dissolution of massive particles, but by the targeted, caused irreversible collapse of the particles due to their internal porosity after the casting process, d. H. by the destruction of at least part of the hollow body.

The porosity of the mold or of the core is selected such that the individual hollow bodies still have sufficient resistance to the mechanical and thermal stresses during the casting process. On the other hand, the compressive strength of the hollow body must be adjusted so that they collapse by a targeted pressure load, which can also be done by purely mechanical action, and occupy less volume than before collapse. Since it is thus possible to intentionally collapse the particles themselves, the bond between the particles no longer has to be adjusted so that it loses stability through the effects during casting or other measures after the casting process. It is therefore possible to choose a bonding form for the particles which ensures maximum stability of the mold or of the core and high abrasion resistance.

The composition of the composition for producing the mold or the core from a base material comprising the hollow bodies and a binder does not exclude that other porosities may also occur in the molding / core material, for example porosities between the particles of the base material. Such porosities may be conditioned by the production process of the mold or the core, but can also be adjusted specifically by further measures or substances, for example. To ensure optimal gas permeability.

The destruction of at least a portion of the hollow body after the solidification of the casting can be carried out by different measures in which a sufficient pressure is exerted on the hollow body in the form or core material. In one embodiment of the method, the collapse of the mold or of the core takes place deliberately by means of an isostatic liquid pressure, which is generated, for example, in a cold isostatic press. Even with a suitable liquid rinse, for example a water rinse, a collapse of the core or molding material can already be achieved with adequate pressure forces exerted by the rinse. A dynamic pressurization is possible to demould the mold or the core, for example. By a shock wave technology.

In one embodiment of the proposed method, a reinforcing element is anchored during manufacture in the mold or in the core, which on the one hand - especially in the case of molding areas or cores with a thin cross section - should serve stability and, on the other hand, is shaped in such a way that it is later Removal of the core or the mold can support. This reinforcing element is integrated into the mold or the core or anchored in that it is accessible from the outside after solidification of the casting and can be pulled out of the mold or the core. Due to the resulting local mechanical stress on the mold or the core, a part of the hollow body is destroyed by the mechanical pressure, so that the mold or the core already sufficiently collapsed by this measure and the casting, for example. By flushing, be removed can.

The rinsing to remove remnants of the mold or the core is preferably carried out by means which additionally contain abrasive additives (suspensions), or by rinsing with increased liquid pressure and / or increased flow rate. With these measures, the effectiveness of the demolding can be increased.

The essential aspect of the decay of the mold or of the core in the proposed method consists in the deliberately set collapse of the molding or core material. Nevertheless, additional thermal or chemical action on the base material itself or on the binder bridges may be provided after the collapse. Here, there is the advantage that an open porosity of the material is achieved by the previously caused collapse of the hollow body, which extends through all areas of the mold or the core. Thus, for example, water can penetrate immediately into all areas of the mold or of the core and ensure good mold or core dissolution behavior in the case of water-soluble mold or core materials, even in hard-to-reach mold areas or core areas.

Brief description of the drawings

The proposed method will be explained in more detail using exemplary embodiments in conjunction with the drawings. Hereby show:

1 a schematic representation of the composition of the molding or core material according to the proposed method; and

2 a schematic representation of an example of a trained according to the proposed method core with internal wiring element.

Ways to carry out the invention

In the proposed method, a collapsible shape or a collapsible core is first produced. For this purpose, the porous base material containing the hollow body and possibly other materials, mixed with binder. Due to the later applied removal or Entformverfahrens very stable binders can be used here. It has proven to be advantageous to tune the compressive strengths of binder and selected hollow bodies in such a way that forces are also generated on the residual structure of the mold or of the core during the targeted collapse of the hollow bodies. Favorable in this case are somewhat firmer hollow bodies which exert pressure, tensile and / or bending forces on the binder structure before or during the course of their destruction, so that they are also damaged during the destruction of the hollow bodies.

After the preparation of the mass for the mold or the core, the shaping of the mold or of the core takes place. This can be done manually, by Kernschießverfahren or by other methods known in the foundry industry. Subsequently, the mold or the core is cured. The mold or the core may possibly also be coated with sizing in order to avoid infiltration of the surface layers. Drying of the mold or core may also be required.

1 Figure 2 shows a schematic representation of two figures showing the structure of the syntactic foam core or molding material in the present process. In the left picture here are the ones through the binder 2 connected hollow spheres 1 to recognize in a larger scale. The right figure shows a reduced view in which a larger number of such hollow spheres 1 it can be recognized by the binder 2 are connected. In this way, a porous material of high intrinsic strength is obtained.

After the formation of the mold or the core, the potting of the potting material for the production of the desired casting is done. After solidification of the casting, the pressure aftertreatment characteristic of the proposed process takes place. In this case, the porous base material, in which the hollow bodies have a matched compressive strength, is deliberately collapsed. The structural strength of the core or of the mold is thereby significantly reduced. A significant advantage is that this collapse is accompanied by a significant volume reduction of the molding or core material. This volume reduction can be about 50% and depends on the type of hollow body used. The pressure treatment can be static, for example. With the help of a cold isostatic press, or done dynamically, for example. By impulse shock waves.

Following the collapse of the molding or core material, the remaining residues can be removed very simply by flushing the casting and the cavities formed therein. This may also be a residual structure of the core or the mold possibly remaining by additional mechanical action, for example. Vibrations, etc., by additional thermal action, for example. A subsequent repeated heating, or possibly by additional chemical action, for example. Rinsing with water to be dissolved. Due to the significant reduction in volume of the molding or core material due to collapse, active media such as water can better attack a residual structure. Core remnants can not easily jam due to the reduced volume, for example, in small channels of the casting. Overall, the collapse of the core or Mold material a simplified demolding or molding. The proposed method thus allows a simple shaping of the mold or of the core combined with a very high stability and a very easy releasability.

In the following exemplary embodiments, different compositions of the molding or core material are cited, which, however, are of course only to be regarded as examples and do not limit the scope of protection of the patent claims. The embodiments relate to the production of cores for molding, but can of course be transferred to the production of molds. For the production of the cores hollow glass spheres of the company 3M with different density and pressure resistance were used as hollow bodies and manufactured with different binder systems (phosphate binding and Wasserglasbindung). The glass hollow ball types S22 (density 0.22 g / cm ³ , isostatic compressive strength 28 × 10 ⁵ Pa (28 bar)) and S60 HS (density 0.60 g / cm ³ , isostatic compressive strength 1240 × 10 ⁵ Pa ( 1240 bar)).

After core fabrication and core cure, they were dried at 100 ° C for at least 1 hour in an oven to prevent outgassing during the run. The cores were then poured into the casting chamber of a cold chamber die casting machine with a piston pressure of 200 · 10 ⁵ Pa (200 bar). An aluminum alloy (AlSi9) was used. In addition, the castings were X-rayed to control core stability. Through two small holes (diameter 5 mm) in the casting, the core mass was destroyed by overpressure in a cold isostatic press and removed by the mechanical action of a water jet from the casting. Finally, the castings were separated to analyze the demolding behavior.

In the first two examples, to bind the base material, i. H. the glass bubbles, phosphate, magnesium oxide and other additives (adjusting agent) used. Magnesium oxide and phosphate react with water release in an exogenous reaction to ammonium dihydrogen phosphate. For mixing the core mass, water or an aqueous silica sol was used. The silica serves as a solvent and reactant.

The components glass hollow spheres, ammonium phosphate, magnesium oxide and adjuster were mixed in a special mixer and then stirred in different mixing with the silica solution to a liquid to viscous flowing mass. The mass was poured into a core mold and cured in the atmosphere. Below are two examples of mixtures. The percentages in each case represent the mass fraction of the total mass.

Mixture 1:

• • Glass hollow spheres S22 52.1%
• • Ammonium phosphate 26.0%
• • Magnesium oxide 20.0%
• • Adjustment agent 1.8%
• • 25 g of powder / 40 ml of silica solution (concentration 100%)

Mix 2:

• • Glass hollow spheres S22 92,8%
• Ammonium phosphate 3.9%
• • Magnesium oxide 2.5%
• • adjusting agent 0.7%
• • 25 g of powder / 40 ml of silica solution (concentration 100%)

The cores produced were subjected to an isostatic press under the influence of an isostatic pressure of 3000 × 10 ⁵ Pa (3000 bar) for about 20 seconds. The core was completely destroyed. In order to verify that the core destruction is not a dissolution of the binder system but a collapse of the glass bubbles, the buoyancy behavior of core residues in water after and before the load with isostatic pressure was considered. The core remnant after the isostatic load drops while the fragment of a core without such load floats on the water. Also, SEM images of the core material before and after the isostatic pressure load clearly show that the pressure load leads to the destruction of part of the hollow glass spheres in the core material.

Furthermore, nuclear destruction up to complete liquefaction of the core material could be achieved by the action of water pressure. As a comparison, a core of glass beads was tested under the same conditions. The hollow glass bullet core was completely destroyed as expected. By contrast, the glass bead core was able to withstand the same load and was not impaired in terms of dimensional stability.

In another example, the cores were coated with a ceramic slurry to increase the dimensional stability during the casting and to reduce or avoid infiltration of the surface layers. This stable cores could be created, which could withstand the mechanical stress during casting with pressure support well. The Kernentformung could also be done here by means of cold isostatic press. The action on the water pressure on the core was made only by two small holes (diameter 2.5 mm) on the casting. Subsequently, the core material could be rinsed with the aid of a simple jet of water.

Furthermore, cores were made with a water glass based binder. The proportion of water glass varies greatly depending on the mixing ratio. The core mass was cured in atmosphere for several days and dried in an oven at 100 ° C for at least one hour prior to being poured. The mixing ratio for the mass of the core was in this example (mixture 3):

Mixture 3:

• • Water 15 g
• • S60HS 45g
• • water glass 5 g

The following further exemplary compositions were used:

Mix 4:

• • Gips 65 g
• • S60HS 51,3 g
• • H₂O 76,6 g

Plaster binder, high binder content approx. 30-40 Vol%

• • gypsum 65 g
• • S60HS 51.3 g
• • H ₂ O 76.6 g

Mix 5:

• • Gips 35,2 g
• • S60HS 54,9 g
• • H₂O 72,4 g

Gypsum cores, low binder content approx. 15-20 Vol%

• • gypsum 35.2 g
• • S60HS 54.9 g
• • H ₂ O 72.4 g

Mixture 6:

• • Wirofine 101,9 g
• • S60HS 80,1 g
• • Kieselsäurelösung 107,6 g

Dental investment binder Wirofine, high binder content approx. 30-40 Vol%

• • Wirofine 101.9g
• • S60HS 80.1 g
• • Silica solution 107.6 g

Mixture 7:

• • Wirofine 54,0 g
• • S60HS 82,9 g
• • Kieselsäurelösung 1 04,5 g

Dental investment binder Wirofine, low binder content approx. 15-20 Vol%

• • Wirofine 54.0 g
• • S60HS 82.9 g
• • Silica solution 1 04.5 g

Mixture 8:

• • Wirovest 61,7 g
• • S60HS 69,4 g
• • Kieselsäurelösung 91,01 g

Dental investment binder Wirovest, high binder content approx. 30-40 Vol%

• • Wirovest 61.7 g
• • S60HS 69.4 g
• • Silica solution 91.01 g

Mixture 9:

• • Wirovest 38,2 g
• • S60HS 81,8 g
• • Kieselsäurelösung 104,9 g

Dental investment binder Wirovest, low binder content approx. 15-20 Vol%

• • Wirovest 38.2 g
• • S60HS 81.8 g
• • Silica solution 104.9 g

2 Finally, there is an example in which the core material is combined with an internal reinforcing element. This reinforcing element is used in cores with a thin cross-section of the core stability and is shaped or anchored so that it can have a supporting effect in the subsequent demoulding of the core. The thin core 3 with the glass bubbles has in the example of the 2 the inside wire-like reinforcing element 4 , Due to its sawtooth-like shape this acts on tensile stress on the surrounding hollow spheres and leads to their collapse. Due to the associated decrease in volume of the core material in the vicinity of the wire reinforcement, it can simply be pulled out of the core. The remaining core remnant is already damaged in its structural stability and can then be easily removed with further measures, for example by flushing. 2 shows the pulling direction in which the reinforcing element 4 from the core 3 is drawn, with the appropriate arrows. reference numeral 5 shows the adjacent section of the manufactured casting.

LIST OF REFERENCE NUMBERS

1

hollow spheres

2

binder

3

core

4

reinforcing element

5

casting

Claims (11)

Method for forming and demoulding a mold and / or a core in the production of a casting by means of molding, in which - the mold and / or the core ( 3 ) is produced from a mass, the hollow particles ( 1 ), - the shape and / or the core ( 3 ) after casting and solidifying a potting material for the production of the casting ( 5 ) is subjected to a pressure which is responsible for destroying at least part of the hollow body particles ( 1 ) in the mold and / or the core ( 3 ), whereby the shape and / or the core ( 3 ) collapses, and - residues of the mold and / or the core ( 3 ) then from the casting ( 5 ) are removed. Process according to Claim 1, in which the hollow body particles ( 1 ) have a compressive strength of> 20 MPa. Process according to Claim 1 or 2, in which as hollow body particles ( 1 ) ceramic hollow microspheres or hollow glass microspheres are used. Method according to one of claims 1 to 3, wherein in the preparation of the mass, a proportion of the hollow body particles ( 1 ) is selected at the mass of 50-95% by volume. Method according to one of claims 1 to 4, wherein the mold and / or the core ( 3 ) after casting and solidifying the potting material is subjected to an isostatic pressure, the destruction of the at least a portion of the hollow body particles ( 1 ) leads. The method of claim 5, wherein the isostatic pressure is generated with a cold isostatic press. Method according to one of claims 1 to 4, wherein the mold and / or the core ( 3 ) is exposed to a dynamic pressure after the casting and solidification of the potting material, the destruction of at least a portion of the hollow body particles ( 1 ) leads. Method according to one of claims 1 to 7, wherein the removal of the residues by a liquid rinse, in particular a water rinse takes place. A method according to claim 8, wherein a liquid with abrasive additives is used for rinsing. Method according to one of claims 1 to 9, wherein in the production of the mold and / or the core ( 3 ) at least one reinforcing element ( 4 ) in the mold and / or the core ( 3 ), which after casting and solidifying the potting material from the mold and / or the core ( 4 ) and thereby destroying the at least part of the hollow body particles ( 1 ) leads. Method according to one of claims 1 to 10, wherein after the destruction of at least a portion of the hollow body particles ( 1 ) an after-treatment of the remainders of the mold and / or the core ( 3 ) takes place on or in the casting by thermal, mechanical or chemical action.

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