CH711152B1 - Process for the production of parts for watchmaking. - Google Patents

Abstract

Method for producing a timepiece, comprising the steps of: providing a mold (1) with a precise mold shape (10) on an interior surface (11) of the mold, the precise shape (10) of the mold corresponding to the negative contours of the timepiece to be produced and the mold (1) being made of a mold material (12); spraying a workpiece material into the mold (1); and separate the mold (1) from the timepiece. According to the invention, the mold material (12) comprising or consists of a salt. The mold temperature (12) is lower than the salt melting temperature during the spraying step.

Description

Description Technical Field [0001] The present invention relates to a process for the production of parts for watchmaking. The present invention also relates to an apparatus for implementing the method.

State of the art Document EP 0 468 467 discloses a process for producing a precision piece of iron or iron alloy, the piece being formed from a sintered body obtained by powder molding, said process comprising steps of forming a homogeneous mixture consisting essentially of iron powder or iron alloy and an organic binder, forming the mixture into a molded body of prescribed shape, removing the organic binder from the molded body under an inert atmosphere , reducing said iron or iron alloy powder contained in the molded body to remove oxygen therefrom, forming a reduced molded body and sintering the reduced molded body. In the process described, the molding is carried out by injection molding and only pieces of iron are produced.

Document EP 1 172 453 discloses a method of manufacturing a molding tool of final shape provided with a structured mold surface having a uniform surface structure, said method comprising the following steps: a) manufacturing a mold made of glass or plastic with a mold surface for forming the structured surface of the molding tool, b) coating the surface of the mold in glass or plastic with at least one material so as to form a body plated in the glass or plastic mold, c) removing the plating body having the structured surface of the glass or plastic mold and d) bonding the plating body to a base body to form the tool final form molding with structured molding surface. The coating of the mold is carried out for example by thermal spraying. The materials used for the plating body are for example metallic or ceramic materials with a high melting point, alloys of nickel and chromium, alloys based on cobalt and carbides being included in these materials.

Several processes are known for producing polymer films, for example those disclosed in document US 2008 0 176 034, in which several polymer layers are produced in the form of a film which thus reproduces the surface of a mold provided with of microstructures. Each layer is made of epoxy powder sprayed on the mold and melted and hardened by an infrared or UV source.

Document US 5,301,415 discloses a method of molding an object by applying segments of complementary material and deposition material so as to form layers of material. The layers of material form a block which contains the object made of a deposited material surrounded by a complementary material which serves as a support structure during molding. Then the additional material is removed. The complementary material is removed by heating the block, whereby the complementary material melts, the deposited material not melting under the heating conditions. The deposited material and the complementary material are preferably applied by thermal spraying, but they can be applied by deposition by welding, from a liquid suspension, by gravity or by any manual means, for example using a manual sieve.

The prior art knows several methods and methods for forming a mold made of a particular material. In addition, methods and methods are also known for coating the surface of a part. These coating methods are used under certain conditions of temperature, pressure, etc. The processing conditions depend, for example, on the coating material used.

Post-processing and mechanical finishing of small parts which must have a precise structure can pose difficulties. These difficulties increase in the event that the part or the surface of the part must meet advanced requirements in terms of hardness, resistance to abrasion and wear, and tribological characteristics as in watchmaking technology. Consequently, there is a need for a method of manufacturing timepieces made of different materials as well as for a corresponding mold and for a method for its manufacture.

Document JPS 50 120 438 describes a method of manufacturing a timepiece in which a mold has the precise shape of the part to be manufactured. A material is sprayed into the mold and then the manufactured part is separated from the mold.

Document EP 1 974 838 describes a process for producing a salt mold which has the advantage of facilitating demolding.

Document EP 2 400 353 relates to a method for manufacturing a needle comprising the steps of: providing a negative of the needle to be produced; be provided with a material comprising at least one metallic element of the precious type and being able to solidify at least partially in the amorphous phase; shaping said material in the negative so as to obtain said needle; and separating said needle from said negative.

Documents GB 295 844 and JP 2 956 493 describe a mold for the production of a watch component.

CH 711 152 B1

Claims (24)

Summary In the present text, the term spraying or the term spraying is used interchangeably to designate a dry surface treatment technique as defined below. Likewise, the terms sprayed and sprayed, as well as the expressions “spray layer” and “spray layer” are equivalent. The object of the invention is to provide a process for the production of parts for horology and an apparatus. A mold for producing these timepieces, as well as a method for manufacturing a mold which makes it possible to manufacture timepieces made from one or different materials are also described. These objects are achieved with a process for the production of timepieces and an apparatus according to the respective independent claims. The process for producing a timepiece includes the steps of: providing a mold with a mold shape on an interior surface of the mold, the shape of the mold corresponding to the negative contours of the timepiece to be produced and the mold being made of a mold material, spraying a material piece in the mold; and separate the mold from the timepiece; wherein the mold material comprises or consists of a salt; wherein the mold material (12) is a solid material at a first pressure which becomes liquid at a second pressure, the first pressure being less than the second pressure, and in which, during the spraying step, the temperature of the mold is kept below the salt melting temperature. According to the invention, the mold material comprises or consists of a material which has a transition between the solid state at a first pressure (mold material in a first state) to a fluid state at a second pressure (mold material in a second state), the first pressure being less than the second pressure. This allows the mold material to adopt a second state at the second pressure or at a pressure higher than this and to flow around a master form present in a mold. Following the release of the pressure until the first pressure, the material of the mold is re-solidified by adopting a first state. Negative contours of the master mold are retained on the inner surface of the mold after removal of the master mold. In one embodiment, the salt is in particular an alkali metal halide and in particular potassium bromide, potassium iodide, cesium iodide or a mixture of these salts. Alternatively, the temperature of the mold (12) is kept below about 600 ° C. In one embodiment, the method further comprises the steps of: providing a device for removing heat; and bringing the mold into contact with said device so as to keep the temperature of the mold below the melting temperature of the salt during the spraying step. In one embodiment, the projection operation and / or the material of the part are modified in a spraying step so that the part for the watch industry comprises a plurality of deposited layers having identical properties or distinct. At least one of the projection layers can be deposited with variable porosity. The porosity of said one of the spray layers may decrease or increase with the increase in the thickness of the layer. According to one embodiment, the decrease in porosity can be alternated with the increase in porosity. The porosity of said one of the projection layers can reach up to 30% to 40%. Variable porosity of said one of the spray layers can be obtained by varying the pressure during the spraying operation. In one embodiment, the method also includes the step of providing a projection device comprising a spray gun by which the material is projected; and in which a variable porosity of said one of the projection layers is obtained by varying the position of the barrel relative to the mold. A variable porosity of said one of the projection layers is obtained by varying the energy of the projection process. In one embodiment, the part material in the mold is a ceramic, a pure carbon material, a metal oxide, a metal, in particular gold, a polymer, a fluoropolymer, a hard metallic material, or a metallic glass. The invention also relates to an apparatus for implementing the method, comprising: a mold having a precise mold shape on an interior surface of the mold, the precise shape of the mold corresponding to the negative contours of the timepiece to be produced and the mold being made of a mold material, the material a mold comprising a salt; a projection device for projecting a workpiece material into the mold; a heat dissipation device configured to be in thermal contact with the mold so that the mold temperature remains below the salt melting temperature when the workpiece material is sprayed into the mold. In one embodiment, the heat removal device comprises a device for circulating a cooling fluid. The heat dissipation device may also include means for controlling the temperature of the mold during the projection of the workpiece material into the mold. CH 711 152 B1 In one embodiment, the apparatus comprises means for storing the mold. The mold storage means can be configured so as to minimize the water content in the mold material, in particular due to the humidity of the environment. The mold storage means can comprise a hermetic enclosure under vacuum, or containing a moisture absorber or a protective gas, in particular dry nitrogen. The invention also relates to a mold for producing a timepiece part, in which an interior surface of the mold comprises a precise structure which corresponds to a precise shape of the mold and intended to be coated by a spraying operation. and being separated from a coating projected onto the interior surface of the mold; wherein the thermal conductivity of the mold material is greater than about 5 Wm ^_1 K ^-1 and preferably 10 Wm ^_1 K ^-1 . In one embodiment, the mold material comprises or consists of a salt and comprises a thermally conductive powder dispersed in the salt. The salt may in particular be an alkali metal halide and in particular potassium bromide, potassium iodide, cesium iodide or a mixture of these salts. In one embodiment, the thermally conductive powder comprises a metallic powder, in particular copper or aluminum, or a conductive carbon powder. The conductive powder can be dispersed in the salt so that it is not near the inner surface of the mold. According to one embodiment, the mold comprises an insert made of thermally conductive material. In one embodiment, the mold material further comprises a reinforcing fiber. The result is the manufacture of precision structured parts whose outline is defined by the precise form of molding of the interior surface of the mold. The precision of the operation is linked to the fact that the precise form of molding is reproduced with accuracy by the material which fills the mold. Therefore, moderate adhesion is desired between the mold material and the material of the timepiece. Likewise, the exterior of the timepiece is in close contact with the interior surface of the mold. The precise shape of the molding must be kept during the filling of the mold by using a spraying operation. Thus, a characteristic of the mold material is firstly its thermal resistance to the conditions which prevail during the spraying of the material of the part. On the other hand, the mold material must be able to be separated from the timepiece without damaging the precise structure of the timepiece. The process is not limited to the production of parts for the watch industry and can also be applied to the production of small parts for any use. Any description in the current patent application mentioning parts for watchmaking is therefore also applicable to different parts. Typically, these pieces are small and are precisely structured. For example, they have a combination of properties which is achieved by forming the part from the outside in the direction of the inside. The maximum dimensions of the pieces are in the range of 1 mm to 5 cm. The maximum dimensions of the parts are, for example, a thickness of 0.2 mm to 1 mm to 2 mm and a diameter of 2 mm to 10 mm to 20 mm. In a variant, the spraying step is carried out by a thermal spraying operation, the operation being in particular a plasma spraying operation, a chemical vapor deposition operation (CVD, "chemical vapor deposition") or a plasma enhanced chemical vapor deposition (PECVD) operation. This makes it possible to produce a part made of solid material of high purity and high performance. The CVD operation is capable of producing thin layers by a chemical reaction and / or a decomposition of a volatile precursor on the mold. Different CVD operations are distinguished by the chemical reaction and the processing conditions used. In addition, more uniform layers can be produced by changing the processing conditions to lower pressure (LPCVD, or lower pressure chemical vapor deposition) or lower temperature (PECVD). In a variant, the spraying step is carried out by a physical vapor deposition (PVD, "physical vapor deposition") operation, for example by sputtering or by evaporation. In one embodiment, the projection operation includes the use of a cold projection process. The spraying operations used make it possible to produce the first part and the second part of the timepiece. A spraying device is used, certain parameters of which are adjustable. After spraying the first part on the interior surface of the mold, a defined set of parameters is modified and the second part is sprayed. The modified set of parameters can for example include the temperature or the nature of the sprayed material (in gaseous, liquid or solid state). This modification of the parameters can be carried out gradually or abruptly. Whatever the method, the modification of the parameters gives rise to a modification of the properties of the material. In this specification, the material of which the timepiece is made is called the part material. In the absence of other indications, the expression material of the part designates the pulverized material as well as the material deposited, in particular the first pulverized layer and the second pulverized layer, as well as the material of a so-called “raw” part, a sintered material or a material which does not yet have the desired final properties for the timepiece 2. In one embodiment, at least part of the material of the part comprises or consists of a ceramic type material, a pure carbon material, a metal oxide, a metal, a polymer, a fluorinated polymer CH 711 152 B1 or a hard metallic material, in particular a carbide or a nitride, or other materials which can be applied by a spraying operation. In the case of a timepiece, it is advantageous to have an outer layer (which corresponds for example to the first sprayed layer) which is stable and resistant to wear and abrasion. A hard material has, for example, these properties. Because of these properties, these materials are difficult to process, especially if you need to machine a precise shape. Consequently, it is advantageous to use the first sprayed layer to on the one hand ensure the desired properties of the material of the surface layer of the timepiece. On the other hand, the desired shape can be reproduced from the precise shape of the interior surface of the mold. In a variant, the step of separating the mold and the timepiece part is based on a chemical process and in particular, it comprises the dissolution of material from the mold by a solvent, a chemical reaction which breaks down the mold material, the melting or combustion of the mold materials and / or an electrochemical operation, in particular a galvanic operation. This makes it possible to remove the mold in a particularly brutal manner, in particular when the precise shape of the mold comprises a structural element undercut. In addition, this requires the timepiece to withstand the conditions of chemical separation. Alternatively, the separation of the mold and the timepiece is based on a mechanical process, and it includes in particular percussion or rupture of the mold. This allows the mold to be removed relatively quickly, especially if the timepiece is hard and not fragile. Alternatively, the mold includes an undercut structure. This makes it possible to produce parts for watchmaking which have a wide variety of structures of complex shape. In a variant, the mold comprising a precise shape is formed entirely before the spraying step. This allows a uniform, continuous spray coat to be applied to the interior surface of the mold. The timepiece production mold includes an interior surface of a mold with a precise structure. This structure corresponds to the precise shape of the mold and can be coated by a spraying operation. The mold can be separated from the spray coating on the interior surface of the mold. This makes it possible to produce a timepiece which has a precise structure, since the precise shape of the mold corresponds to the desired structure for the timepiece. Alternatively, the interior surface of the mold withstands the conditions prevailing during the spraying operation, the operation being in particular a plasma spraying process, a chemical vapor deposition process or a chemical deposition process of vapor reinforced by plasma. This allows a wide range of materials suitable for spraying to be used in a spraying operation. In one embodiment, the material used for spraying on the internal surface of the mold comprises or consists of a ceramic type material, a metal oxide, a pure carbon material, a pure metal, a hard metal material, in particular a carbide or a nitride, or a fluorinated polymer. This makes it possible to form the timepiece by selecting and / or combining materials with different properties. Alternatively, the timepiece is made of a single material which has uniform properties. In general, the conditions prevailing during the spraying of the part material are granted to the properties desired for the part for the watch industry in use. In addition, the mold has good resistance to spraying conditions, the mold being able to be separated from the timepiece without damaging the timepiece. Brief description of the figures The object of the invention will be explained in more detail in the remainder of this document with reference to preferred embodiments which are illustrated in the accompanying drawings which schematically represent: in fig. 1: a master mold, the mold material being formed in a matrix and the mold material maintaining a master form, in fig. 2: a known (intrinsically) spray device for coating the mold; in fig. 3: a series of stages in the production process of a part for timepieces with a precise structure; fig. 4a and 4b illustrate the heat dissipation device, according to one embodiment; fig. 5 shows a sectional view of a mold holder, according to one embodiment; and fig. 6 shows an enclosure configured to receive one or more mold carriers, according to one embodiment. CH 711 152 B1 Example (s) of embodiment [0049] FIG. 1 schematically represents a master mold 3 which comprises at least one matrix 31 and / or a compression plunger 32. The matrix 31 and / or the compression plunger 32 comprise a master form 30. The master form 30 defines the structure precise of a timepiece 2 to be manufactured, and in particular at least part of the shape of the timepiece 2. The master mold is filled with a mold material 12, the mold material 12 can be a metallic material, in particular copper, or a polymer material, in particular polyoxymethylene (POM) or polyimide (Kapton), or a solid material at a first pressure and becoming fluid at a second pressure, the first pressure being less than the second pressure. This fluid material at the second pressure can in particular be a mineral salt, in particular an alkali metal halide and in particular potassium bromide, potassium iodide, cesium iodide or a mixture of these salts. The mold material 12 is compressed in the master mold 3 by a compressive force 33 (arrows) and flows around the master form 30 of the master mold 3. The fluid mold material 12 therefore marries the negative contours of the master mold 3 and of the future timepiece 2. In the fluid state, the mold material is in a second state 14. During or after the release of the compressive force 33, the state of the mold material 12 goes into a first state 13. The first state 13 of the mold material is a solid state. During the resolidification and after this resolidification of the mold material in the second state 14 into the mold material in the first state 13, the mold material 12 retains the negative contours of the master mold 3. In a final step, the mold 1 is removed from the master mold 3, for example by applying mechanical pressure possibly in combination with thermal effects to exploit the expansion of the material, the master form 30 corresponding to the form precise 20 of a part being reproduced in a precise molded form 10. The molded shape 10 precise is obtained on the inner surface 11 of the mold. At least part of the interior surface 11 of the mold is defined by the mold material 12 and withstands the conditions which prevail during the further formation of the timepiece part 2. It will be understood that the mold 1 can be made of so understand more than one molded form 10. For example, the mold can comprise a plurality of molded shapes 10 so that a plurality of parts for watchmaking 2 can be produced with a single mold 1. According to the invention, the mold material 12 is a solid material at a first pressure which becomes fluid at a second pressure, the first pressure being less than the second pressure. When the compressive force 33 which compresses the mold material 12 in the master mold 3 is high enough to reach at least the second pressure, the liquefied mold material 12 flows around the master form 30. Then, the compression force 33 is lowered, the mold material 12 becomes solid again and retains the negative contours of the master form 30. Alternatively, the mold material 12 comprises a metallic material or a polymeric material. The mold 1 can be produced using a ceramic injection molding (CIM), a metal injection molding (MIM) or a plastic injection molding (PIM), the fluid mold material 12 (mold material in its second state 14) is compressed in a master mold 3 and the part called "raw" is cooled and demolded. Conventionally, such a “green part” obtained by a CIM, MIM or PIM operation is fragile and receives its resistance in an additional sintering step. For the application as a mold 1, which has a precise shape 10 at the level of the interior surface 11 of the mold, it suffices that the "green part" can withstand the conditions which prevail during the formation of the part for watchmaking 2. Consequently, in many cases, the sintering step can be omitted, with the consequence that the mold can be easily destroyed after the formation of the timepiece 2. Alternatively, the mold 1 has undercuts. An undercut structure of the interior surface 11 of the mold can be produced using at least two compression plungers 32 which include a master form 30. The compression plungers 2 can come into close contact with each other and the molding material 12 is pushed back to the sides. The undercut structure of the interior surface 11 of the mold can also be obtained with a mold 1 which comprises at least two mold parts. These mold parts can be combined after re-solidification so as to constitute the uniform mold 1. The undercut structure of the interior surface 11 of the mold can be produced in various known ways, for example by using a divisible master mold 3 and / or additional movable molding parts which can be removed after re-solidification of the mold material 12 without destroying the precise shape 10 of the mold. Lafig. 2 schematically represents a spraying device 4, the device comprising a spraying barrel 41. The material sprayed by the spraying barrel 41 and also called sprayed material 42 corresponds to the material of which the timepiece 2 is made (material of the room). The sprayed material 42 is sprayed into the mold 1 which has the precise shape 10 of the mold. The spraying device 4 is used in particular for a thermal spraying operation, the thermal spraying operation possibly in particular being a plasma spraying process, a chemical vapor deposition (CVD) process or a process for plasma enhanced chemical vapor deposition (PECVD). The plasma spraying operation is carried out at low pressure and is in particular a vacuum plasma spraying (VPS) or CH 711 152 B1 low pressure plasma spraying (LPPS). It is advantageous to use CVD methods because the layer applied to a surface is very homogeneous and a wide range of materials can be deposited as sprayed material 42. The timepiece 2 may have to have a certain combination of properties, for example a high mechanical resistance (hardness), a high abrasion resistance, a high wear resistance, a low electrical conductivity in as well as high thermal conductivity. Some of these properties, for example mechanical resistance, can cause enormous problems when the part is produced in a conventional manner, in particular when the structures are small and precise. These problems can be overcome with the method presented here using a sprayed material 42 which has the desired properties. This pulverized material 42 may be a metal oxide, in particular a ceramic-type material, a pure metal, a pure carbon material, a hard metallic material, in particular a carbide or a nitride, or a fluorinated polymer, in particular Teflon. ®. To form a timepiece 2, the mold 1 comprising the inner surface 11 of a precisely shaped mold must withstand the conditions prevailing during the spraying operation. The temperature can reach, for example from 200 ° C to more than 500 ° C during spraying. This implies that the mold 1 and in particular the inner surface 11 of the mold must have a high resistance to heat where the sprayed material 42 must reproduce the precise shape 10 of the mold. It may be advantageous that the sprayed material 42 has a strong adhesion with respect to the mold material 12, so as to allow an exact reproduction of the precise shape 10 of the mold. The properties that are expected from a piece for watchmaking 2 and given above mainly concern the properties of the surface of the piece for watchmaking 2, and it is therefore possible to form a piece of watchmaking 2 which comprises at least two parts. A first part will correspond for example to a surface layer or to the coating of the part for watchmaking 2 and a second part will correspond to the material which fills the interior of the part for watchmaking 2. Consequently, the part for watchmaking 2 will be formed in reverse order, the surface layer being first sprayed into the precise shape of the mold and the interior material will then be deposited on the surface layer, for example by filling the rest of the mold. One can control or manipulate different properties of the first coating layer 21 and the second coating layer 22 by modifying the type, consistency, flow rate, deposition rate, etc. of the sprayed material 42 and / or the thickness of the deposited layer. One possibility of controlling the thickness and the quality of the deposited layer consists in using a single spraying device 4 in different operating modes. One can for example use the spraying device 4 by supplying it with a gaseous material so as to form a thin layer, but subsequently using a solid material (for example a powder) introduced into the same spraying device 4 to form a thick layer which will fill the precise shape of the mold. The materials delivered in the gaseous state and in the solid state can be identical or different. The deposition rate can be regulated and affect the properties and quality of the deposited layer using a single spray device 4. Alternatively, the mold 1 may have undercuts. In this case, it is advantageous for the spraying device 4 and the mold 1 to be able to move relative to one another, for example in a reversal movement. The inversion of the spraying device 4 and / or of the mold 1 guarantees that the undercut parts of the mold can be coated with the sprayed material 42 and that the precise shape 10 of the mold can be reproduced. [0065] FIG. 3 represents a series of steps in the operation of manufacturing a piece for watchmaking 2. Firstly (FIG. 3a), a mold is provided which includes an interior surface 11 of mold of a precise shape 10 of mold. The precise shape 10 of the mold corresponds to the negative contours of the timepiece 2. In a next step (Fig. 3b), is deposited on the inner surface 11 of the mold a first spray layer 21 which corresponds to a coating. The mold material 12 must withstand the conditions prevailing during spraying, because the precise shape of the mold must be retained. The first spraying step comprises a spraying operation, in particular a thermal spraying operation and in particular a plasma spraying operation, a chemical vapor deposition operation (CVD) or a chemical plasma enhanced vapor deposition operation (PSCVD ). Low pressure plasma spraying methods can also be used to form the first spray layer 21. The first spray layer 21 or the coating correspond to the surface of the future timepiece 2 and must therefore have a high quality and high performance in terms of hardness and resistance to wear and abrasion. In a subsequent step (Fig. 3c), a second spray layer 22 or, in this case, a filler, is deposited on the first spray layer 21. The requirements imposed on the second spray layer 22 may be different from those imposed on the first spray layer 21. This makes it possible to give the material of the timepiece 2 complementary properties, for example a more elastic filling load and a harder coating. Likewise, depending on the requirements, a less expensive material may be used for the filling charge than for the coating. The present example presents two spray layers, but it is obviously possible to apply a single spray layer or more than two spray layers which have different properties. CH 711 152 B1 A modification of the properties of the spray layers can be obtained by adapting the coating conditions, for example the temperature, the deposition rate, the material deposited and / or the sprayed material 42 introduced into the device. spraying 4 by passing it from a gaseous material to a solid material (powder). The composition of successive spray layers can vary gradually or suddenly. The second spray layer 22 can be formed by filling the mold 1 at least until a filling level is reached. In a later step (fig. 3e), the excess material which could be present on the external surface of the mold or exceed the filling level is ground or abraded. The excess material may include a portion of the second spray layer 22 but may also include a portion of the first spray layer 21. The grinding or abrasion used to remove excess material can be carried out at a stage at which the timepiece 2 is still present in the mold 1 and is therefore mechanically maintained and stabilized by the mold 1. In a subsequent step (not shown), an additional layer is sprayed onto the ground or abraded surface. The sprayed material may be the material of the first spray layer 21, the material of the second spray layer 22 or a different material. In another step (fig. 3e), the mold 1 and the timepiece part 2 are separated from one another. The separation step comprises a chemical process or a mechanical removal process of the mold 1. The chemical process comprises in particular the dissolution of the material 12 of the mold by a solvent, a chemical reaction which decomposes the material 12 of the mold, the melting or the combustion of the material 12 of the mold and / or an electrochemical operation, especially a galvanic operation. The mechanical process includes in particular percussion or rupture of the mold 1. The timepiece 2 or at least the outer surface of the timepiece 2 must withstand the conditions prevailing during the separation step. In one embodiment, the method of producing the part for watchmaking 2 comprising the steps of: providing the mold 1 in which the mold material 12 comprises or consists of a salt; spraying a workpiece material into the mold 1; and separate the mold 1 from the timepiece 2, in which the temperature of the mold 12 is lower than the melting temperature of the salt during the spraying step. The mold material 12 can comprise or consist of a salt in the solid state at a first pressure and in a fluid state at a second pressure, greater than the first pressure. In this case, the first pressure is greater than the pressure prevailing during the spraying step. The mold material 12 can comprise an alkali metal halide and in particular potassium bromide, potassium iodide, cesium iodide or a mixture of these salts. The production process can be carried out with production equipment comprising: the mold 1 produced in the mold material 12 comprising a salt; the projection device 4 for projecting a workpiece material into the mold 1; and a heat dissipation device 101 configured to be in thermal contact with the mold so that the temperature of the mold 1 remains below the melting temperature of the salt when a part material is sprayed into the mold. Figs. 4a and 4b illustrate the heat removal device 101 comprising means 102 for circulating a cooling fluid, taking the form of a coil, and for supplying 103 of this fluid to the heat removal device 101. The means of circulation 102 of fluid and supply 103 can be integrated into this device 101. In FIG. 4b, molds 1 are mounted in storage means 104. In the example illustrated, the storage means takes the form of a mold holder 104 in which several molds 1 are arranged, the mold holder 104 coming into contact with the heat removal device 101 (Fig. 4b). FIG. 5 shows a sectional view of the mold holder 104 comprising a first disc 105 intended to come into contact with the heat removal device 101. The first disc 105 comprises through cavities 107 arranged to receive the molds 1. The latter are fixed in the cavities 107, between a thermally conductive stud 109 and a second disc 106. Once fixed, the underside 110 of the mold 1 comes to bear against a stud 109 intended to come into contact with the heat removal device 101. The heat stored in the mold 1 during the spraying operation can therefore be dissipated towards the heat removal device 101. It goes without saying that other configurations for the heat removal device 101 are possible. The second disc 106 has openings 108 so that the molded form 10 of the mold is accessible to projection. The production equipment may include means for controlling (not shown) the temperature of the mold during the projection of the part material into the mold 1. Still in an embodiment illustrated in FIG. 6, the storage means 104 comprise an enclosure 111 preferably hermetic and configured to receive one or more mold carriers 104. The enclosure 111 makes it possible to transport the molds 1, for example between stages of production of the molded parts 2, under conditions where the CH 711 152 B1 water content in the mold material 12 is minimized. To this end, a vacuum can be created in enclosure 111, or the latter can contain a moisture absorber (not shown) or a protective gas, in particular dry nitrogen. The thermal conductivity of a mold 1 made with an alkali metal halide such as potassium bromide, potassium iodide or cesium iodide may be insufficient to sufficiently dissipate the heat produced during a projection operation. For example, the thermal conductivity of potassium bromide is approximately equal to 5 Wm ^_1 K ^-1 , or more particularly approximately 4.68 Wm ^_1 K ^-1 , and the formation of part 2 with a thermal spraying process could lead to a local or global melting of the mold 1 during the thermal spraying phase. It therefore appears advantageous to carry out the manufacture of the part 2 in a mold 1 having a higher thermal conductivity allowing a greater heat exchange per unit of time. For example, a value of thermal conductivity of the mold 1 can be greater than approximately 5 Wm ^_1 K ^-1 , or even greater than approximately 10 Wm ^_1 K ^-1 . In one embodiment, the mold material 12 contains a thermally conductive powder mixed with the salt. In particular, the thermally conductive powder can comprise a metallic powder, in particular copper or aluminum, a conductive carbon powder or any other powder of a conductive material or a combination of these powders. The mold 1 obtained from this mixture should have a thermal conductivity which is greater than about 5 Wm “1 K ^-1 or else 10 Wnn ^_ 1 K ^-1 . The mold material 12 can also include one or more reinforcing fibers. Preferably, the conductive powder or the mixture of conductive powders is dispersed in the salt so that it is not located near the inner surface 11 of the mold. Indeed, the absence of conductive powder on the inner surface 11 of the mold makes it possible to avoid possible contamination of the part 2 by this powder. According to one embodiment, the mold 1 comprises an insert made of thermally conductive material. The insert may take the form of a metal plate or film affixed to the underside 110 of the mold 1 so as to facilitate the conduction of heat from the mold 1 to the heat dissipation device 101. During the spraying operation, the mold 1 is brought into contact with the heat removal device 101 so that the temperature of the mold 12 is lower than the melting temperature of the salt during the step of projection. In another embodiment, the modification of the properties of the projection layers comprises the deposition of a plurality of layers having identical or distinct properties. It is possible that at least one of the projection layers 22 is sprayed with variable porosity. For example, the porosity of at least one of the projection layers 22 can decrease or increase with the increase in the thickness of the layer 22. The decrease in porosity can be alternated with the increase in porosity . It is also conceivable to ensure that the porosity of said at least one of the projection layers 22 can reach up to 30% to 40%. A variable porosity of said at least one of the projection layers 22 can be obtained, for example, by varying the pressure during the spraying operation. A variable porosity of said at least one of the projection layers 22 can also be obtained by varying the position of the barrel 41 relative to the mold 1, or even by varying the energy of the projection process. In yet another embodiment, the part material in the mold 1 is a ceramic, a pure carbon material, a metal oxide, a metal, in particular gold, a polymer, a fluorinated polymer, a material hard metal or metallic glass. In yet another embodiment, the part material in the mold 1 is porous gold. In another embodiment, the projection operation is a cold spray method. The cold spraying process is a cold metallization process, in the sense that the metal powders are sprayed at very high speed by a gas under pressure (up to 50 bar and heated to a maximum temperature of 1100 ° C), the impact force ensuring the quality of the deposit. A convergent-divergent nozzle allows the gas to expand to ambient pressure, causing it to accelerate to supersonic speed and cool down to a temperature below 100 ° C. The powders, injected into the converging part of the nozzle, are accelerated at a speed of up to 1200 m / s, allowing strong adhesion to the point of impact and therefore a very high quality coating, very weakly oxidized. The cold spraying process has many advantages compared to more traditional metallization processes, in particular, a density of the deposit very close to the theoretical density of the material; a deposit having low porosity and roughness while allowing to deposit large thicknesses (several mm). However, the most interesting advantage of the cold spraying process here is the fact that the material is sprayed at low temperature, making it possible to avoid the problem of heat dissipation during the spraying operation in the salt mold. claims 1. Method for producing a timepiece part (2), comprising the steps of: CH 711 152 B1 provide a mold (1) with a mold shape (10) on an interior surface (11) of the mold, the mold shape (10) corresponding to the negative contours of the timepiece (2 ) which is to be produced and the mold (1) being made of a mold material (12), projecting a workpiece material into the mold (1); and separate the mold (1) from the timepiece part (2); wherein the mold material (12) comprises or consists of a salt; characterized in that the mold material (12) is a solid material at a first pressure which becomes liquid at a second pressure, the first pressure being less than the second pressure, and in that during the spraying step, the temperature of the mold (12) is kept below the melting temperature of the salt (12). 2. Method according to claim 1, wherein the salt is an alkali metal halide and in particular potassium bromide, potassium iodide, cesium iodide or a mixture of these salts. 3. Method according to one of claims 1 and 2, further comprising the steps of: provide a device (101) for heat dissipation; and bringing the mold (1) into contact with said device (101) so as to keep the temperature of the mold (12) below the salt melting temperature during the spraying step. 4. Method according to one of claims 1 to 3, wherein the spraying operation comprises the use of a cold spraying method. 5. Method according to one of claims 1 to 4, wherein the projection step and / or the piece material are modified in a spraying step so that the timepiece (2) comprises a plurality of deposited layers, called projection layers (22), having identical or distinct properties. 6. The method of claim 5, wherein at least one of the projection layers (22) is deposited with variable porosity. 7. The method of claim 6, wherein the porosity of said one of the projection layers (22) decreases or increases with the increase in the thickness of the layer (22). 8. The method of claim 7, wherein the decrease in porosity is alternated with the increase in porosity. 9. Method according to one of claims 7 and 8, wherein the porosity of said one of the projection layers (22) can reach up to 40%. 10. Method according to one of claims 7 to 9, wherein a variable porosity of said one of the projection layers (22) is obtained by varying the pressure during the spraying operation. 11. Method according to one of claims 7 to 10, comprising the step of providing a projection device (4) comprising a projection gun (41) by which the material is projected; and in which a variable porosity of said one of the projection layers (22) is obtained by varying the position of the barrel (41) relative to the mold (1). 12. Method according to one of claims 7 to 11, wherein a variable porosity of said one of the projection layers (22) is obtained by varying the projection energy. 13. Method according to one of claims 1 to 12, in which the part material in the mold (1) is a ceramic, a pure carbon material, a metal oxide, a metal, in particular gold, a polymer, a fluoropolymer, a hard metallic material, or a metallic glass. 14. Apparatus for implementing the method according to one of claims 1 to 13, comprising: a mold (1) having a mold shape (10) on an interior surface (11) of the mold, the mold shape (10) corresponding to the negative contours of the timepiece (2) to be produced and the mold (1) being made of a mold material (12), the mold material comprising a salt; a projection device (4) for projecting a workpiece material into the mold (1); a heat dissipation device (101) configured to be in thermal contact with the mold so that the temperature of the mold (1) remains below 600 ° C when the workpiece material is sprayed into the mold. 15. Apparatus according to claim 14, wherein the heat removal device (101) comprises a circulation device (102) of a cooling fluid. 16. Apparatus according to claim 14 or 15, further comprising means for controlling the temperature of the mold during the projection of the workpiece material into the mold (1). 17. Apparatus according to one of claims 14 to 16, further comprising storage means (104) of the mold (1). 18. Apparatus according to claim 17, wherein the storage means (104) of the mold comprise an airtight enclosure (111) under vacuum, or containing a moisture absorber or a protective gas, in particular dry nitrogen. CH 711 152 B1 19. Apparatus according to one of claims 14 to 18, wherein the thermal conductivity of the mold material (12), determined at 25 ° C, is greater than about 5 W m ^_1 K ^-1 and preferably 10 W m ^_1 K ^-1 . 20. Apparatus according to claim 19, wherein the mold material (12) comprises a thermally conductive powder dispersed in the salt; the thermally conductive powder comprising a metallic powder, in particular copper or aluminum, or a conductive carbon powder. 21. Apparatus according to claim 20 wherein the salt is an alkali metal halide and in particular potassium bromide, potassium iodide, cesium iodide or a mixture of these salts. 22. Apparatus according to claim 20 or 21, wherein the thermally conductive powder in the salt is not located near the inner surface (11) of the mold (1). 23. Apparatus according to one of claims 20 to 22, wherein the mold (1) comprises an insert taking the form of a plate or a metal film so as to facilitate the conduction of heat from the mold (1) to a heat removal device (101). 24. Apparatus according to one of claims 20 to 23, wherein the mold material (12) further comprises a reinforcing fiber. CH 711 152 B1 CH 711 152 B1