Manufacturing process for a semi-matte decorative part and semi-matte decorative part

Abstract

The present invention relates to a method for manufacturing a semi-matte decorative part, the method comprising the steps of: - providing a decorative part, this decorative part having a hardness equal to or greater than 800 HV, - placing the decorative part in a drum, the drum comprising an abrasive powder of a material selected from at least one of the following materials: diamond, boron nitride, silicon carbide, alumina and / or boron carbide, - operating the drum for at least 3 hours so that the decorative part is set in motion at an average speed of between 0.5 m / min and 1.5 m / min. The semi-matte decorative part (1) has a silky or velvety appearance with light colors, for example, they can be white. It gets less dirty compared to known matte parts and can be easily cleaned. Figure to be published with the abstract: Figure 2

Description

Title of the invention: Method for manufacturing a semi-matte decorative part and semi-matte decorative part technical field

[0001] The present invention relates to a method for manufacturing a semi-matte decorative part and a semi-matte decorative part. The semi-matte decorative part according to the invention is not limited to the fields of watchmaking, jewelry and / or fine jewelry, but also finds application in the general field of microtechnology, in the field of mobile or portable devices, in the field of vehicles, or in any other field in which the semi-matte part serves to decorate an object and is visible during the use of that object. State of the art

[0002] Matte decorative parts, that is to say parts which have no luster, which do not shine and / or which do not reflect light, are widely known and used in various objects, particularly in the fields of watchmaking, jewelry and fine jewelry.

[0003] Non-limiting examples of these matte decorative parts include caps and bracelet links for wristwatches.

[0004] The matte finish is achieved by means of scratches with a depth on the order of a few micrometers. Such scratches can, however, trap dirt, making them difficult to clean. Moreover, this dirt is particularly visible if the decorative piece is light-colored, for example, white.

[0005] There is therefore a need for a decorative piece that receives less dirt compared to known decorative pieces.

[0006] There is also a need for a decorative piece that can be cleaned more easily compared to known decorative pieces.

[0007] There is also a need for a decorative piece that has a different appearance from known decorative pieces. Brief summary of the invention

[0008] One object of the present invention is to provide a decorative piece free from the limitations of known decorative pieces.

[0009] Another object of the invention is to provide a decorative piece that receives less dirt compared to known decorative pieces.

[0010] Another object of the invention is to provide a decorative piece that can be cleaned more easily than known decorative pieces.

[0011] Another object of the invention is to provide a decorative piece that has an appearance different from known decorative pieces.

[0012] According to the invention, these goals are achieved in particular by means of the process of manufacturing a semi-matte decorative part as well as by means of a decorative part.

[0013] The method for manufacturing a semi-matte decorative part according to the invention comprises the steps of: - provide a decorative part, this decorative part having a hardness equal to or greater than 800 HV, - place the decorative piece in a barrel, the barrel containing an abrasive powder of a material chosen from at least one of the following materials: diamond, boron nitride, silicon carbide, alumina and / or boron carbide, - operate the barrel for at least 3 hours so that the decorative piece is set in motion at an average speed of between 0.5 m / min and 1.5 m / min, and preferably between 0.7 m / min and 0.9 m / min, for example at 0.8 m / min, which makes it possible to obtain a surface profile with an asymmetry in the range of -1 qm to -0.3 qm, a profile height in the range of 0.1 qm to 1.5 qm and a roughness in the range of 0.1 qm to 0.2 qm, so as to make the surface semi-matte.

[0014] In one embodiment, the movement of the part is a movement that has several directions in time, for example a vibration movement.

[0015] In this context, the expression "semi-matte part" indicates a part whose surfaces only partially reflect light specularly (reflection at an angle equal to the angle of incidence with respect to the normal and in the same plane, like a mirror), which mainly reflect light diffusely (that is, the light is reflected at a large number of angles), which has a partial sheen and which shines partially. Its visual appearance is silky, velvety or velvety.

[0016] In one embodiment, the specular reflection of the part according to the invention with respect to a polished part (i.e. comprising smooth surfaces) made of the same material decreases by up to 69% and the diffuse reflection of the part according to the invention with respect to a polished part made of the same material increases by more than 100%, for example up to 113%.

[0017] In this context, the parameter "asymmetry" (Rsk) refers to the asymmetry of the distribution of surface features (particularly peaks and troughs), defined over an evaluation or baseline length (for example, 250 sq m). This parameter provides information on the morphology of the surface state. A positive value of Rsk corresponds to a surface with peaks protruding above the surface, and therefore a distribution shifted towards the lowest points, whereas a negative value corresponds to a plateau surface with deep valleys (or troughs), and a distribution shifted towards the highest points.

[0018] In this context, the parameter "profile height" (Rt) refers to the height between the deepest valley and the highest peak over an evaluation length (for example, 250 pm). This parameter allows for a local evaluation of the profile.

[0019] In this context, the parameter "roughness" (Ra) refers to the arithmetic mean roughness of the profile of a surface of the decorative part. It is defined over a base length. This parameter allows for an overall evaluation of the profile roughness amplitude.

[0020] This solution therefore provides for a tumbling step with a specific type of abrasive, namely with an abrasive powder of a material chosen from at least one of the following materials: diamond, boron nitride, silicon carbide, alumina and / or boron carbide.

[0021] This abrasive powder has the particularity that its particles do not break (or break very little) during the tumbling process: this prevents the tumbling step from becoming a polishing step. Indeed, the parts produced are not polished parts, but semi-matte parts.

[0022] In a preferred embodiment, an abrasive diamond powder is used.

[0023] The use of abrasive powder according to the invention, and in particular diamond abrasive powder, is not obvious, firstly because of the cost of this powder. Moreover, this powder, and in particular diamond powder, can damage the barrel. In addition, this powder is often suspended in a liquid, for example oil, which makes cleaning the barrel complicated.

[0024] Contrary to expectations, tests carried out by the applicant demonstrated that the use of this abrasive powder according to the invention is not only feasible, but also makes it possible to obtain a semi-matte part that gets less dirty than known decorative parts and that can be cleaned more easily than known matte decorative parts: indeed, the semi-matte parts according to the invention, due to their structure as defined by the parameters Rsk, Rt, and Ra, get less dirty compared to known matte parts, and—even if they do get dirty—they can be cleaned easily. Consequently, the semi-matte decorative parts according to the invention can also be made in light colors; for example, they can be white.

[0025] This solution has the particular advantage over the prior art of offering a decorative piece which has a silky or velvety appearance, which is different from the appearance (matte or lucid) of known decorative pieces.

[0026] In one embodiment, the process includes a step of unloading the barrel of semi-matte decorative pieces.

[0027] In one embodiment, the process includes a cleaning step of the barrel, which generally follows the barrel unloading stage.

[0028] In one embodiment, the process includes a step of washing the semi-matte decorative parts, which generally follows the step of unloading the barrel.

[0029] In one embodiment, the process includes a step of checking the semi-matte decorative part which as a rule follows (generally not immediately) the unloading step of the barrel, for example an inspection step.

[0030] In one embodiment, the process includes a step of polishing the decorative parts, which generally precedes the barrel loading step. In other words, in this embodiment, the process according to the invention makes it possible to "de-polish" previously polished parts, rendering them semi-matte.

[0031] In one embodiment, the particle size of the abrasive powder (namely, their largest dimension) is in the range of 5 µm to 50 µm, preferably in the range of 10 µm to 30 µm, for example in the range of 15 µm to 25 µm.

[0032] In one embodiment, the particles of the abrasive powder do not all necessarily have the same shape.

[0033] In one embodiment, the particles of the abrasive powder do not all necessarily have the same size.

[0034] In one embodiment, the abrasive powder used in the barrel is suspended in a liquid.

[0035] In one embodiment, the liquid includes a surfactant, for example an oil and / or a soap, in order to improve the suspension of the abrasive powder in the liquid.

[0036] In one embodiment, the process includes the step of putting several decorative pieces into the barrel, for example dozens, hundreds or thousands of decorative pieces.

[0037] In one embodiment, the process also includes the step of placing in the barrel with the decorative piece also media or "chips" whose largest dimension belongs to the range 0.3 mm to 15 mm. These media can be cylindrical or any other suitable shape. In one embodiment, the volume of the media in the barrel is approximately at least 4 times the total volume of the decorative pieces in the barrel.

[0038] In one embodiment, the decorative piece is made of ceramic, metallic ceramic (“cermet”), sapphire and / or sintered glass.

[0039] In one embodiment, once the barrel has been used for the process according to the invention, it can no longer be used for other different processes (such as polishing, for example) but remains dedicated exclusively to the process according to the invention: indeed, the claimed abrasive powder degrades the walls of the barrel, which impacts the condition of the surfaces of the parts that one would attempt to polish with this barrel. By on the other hand, it can be reused for another process according to the invention.

[0040] In one embodiment, the barrel is operated for a number of hours greater than 3 hours, for example for 5 hours or for 10 hours.

[0041] The present invention also relates to a decorative part having a hardness equal to or greater than 800 HV and comprising a surface including scratches, a surface profile having an asymmetry in the range of -1 pm to -0.3 pm, a profile height in the range of 0.1 pm to 1.5 pm and a roughness in the range of 0.1 pm to 0.2 pm, so as to make the surface semi-matte.

[0042] In one embodiment, the decorative piece is made of ceramic, metallic ceramic (“cermet”), sapphire and / or sintered glass.

[0043] In one embodiment, the distribution of the directions of the scratches on the surface is irregular, namely the scratches do not all have the same direction: on the contrary, each scratch has a direction which does not necessarily correspond to the direction of another scratch, these scratches being produced by scratching, impact or erosion.

[0044] In one embodiment, the density of scratches per unit area is uniform over the surface. In one embodiment, this density is in the range of 100 to 400 scratches for a square surface of 100 pm on each side, and preferably it is in the range of 180 to 220 scratches for a square surface of 100 pm on each side.

[0045] In one embodiment, the stripes define valleys and peaks.

[0046] In this context, the term "peak" indicates a protrusion, namely a pro A tubercle defined between two ends, in which one end (the base) is larger than the other end (the free end or point). A peak can be shaped like a pyramid, a cone, a truncated pyramid, or a truncated cone, etc.

[0047] The peaks may be separated by valleys, namely hollows or openings, defined by surfaces, in particular by at least two surfaces. In one variant, these surfaces are lateral surfaces of two contiguous peaks.

[0048] The peaks are not necessarily periodic, i.e. regularly spaced, and may have different cross-sections, for example, but not limited to, inverted V-shaped, inverted U-shaped, etc. The semi-matte decorative piece according to the invention may include peaks of different shapes.

[0049] In one embodiment, the bottom of the valleys is located at a substantially constant depth of the semi-matte decorative piece according to the invention. Valleys of varying depths can, however, also be envisaged.

[0050] In one embodiment, the average height between the valley depth and the peak height is within the range of 0.1 pm to 1 pm. This average height of the profile elements is defined over the evaluation length. This parameter is close to the R parameter of ISO 12085 and can be considered a pattern parameter (see ISO 25178).

[0051] In one embodiment, the height of the peaks and / or the depth of the valleys is irregular(s).

[0052] In a preferred embodiment, the stripes are all substantially straight or rectilinear. In another embodiment, at least some of the stripes are not straight, for example they are curved.

[0053] In one embodiment, the length of scratches on the surface is within the range of 1 pm to 70 pm.

[0054] In one embodiment, the width of the stripes on the surface is within the range of 1 pm to 5 pm.

[0055] In one embodiment, the specular reflection of the part according to the invention with respect to a polished part made of the same material decreases by up to 70% and the diffuse reflection of the part according to the invention with respect to a polished part made of the same material increases by more than 100%.

[0056] In one embodiment, the semi-matte decorative piece is monobloc, that is to say made of a single block.

[0057] In one embodiment, the semi-matte decorative piece is a link of a bracelet (for example, of a wristwatch) or a bezel of a watch (for example, of a wristwatch).

[0058] The present invention also relates to a timepiece (for example a watch or a wristwatch), jewelry and / or fine jewelry, comprising the semi-matte decorative piece according to the invention. Brief description of the figures

[0059] Examples of implementation of the invention are given in the description illustrated by the accompanying figures in which:

[0060] [Fig-1] illustrates a perspective view of one embodiment of a part semi-matte decorative finish according to the invention.

[0061] [Fig.2] illustrates a portion of a cross-sectional diagram of the semi-matte decorative piece of [Fig. 1].

[0062] [Fig.3] illustrates a profile of a surface having a roughness asymmetry parameter Rsk of zero (FIG. 3A), a profile of a surface having a roughness asymmetry parameter Rsk positive (FIG. 3B) and a profile of a surface having a roughness asymmetry parameter Rsk negative (FIG. 3C).

[0063] [Fig.4A] illustrates a perspective view of a surface of the semi-matte decorative piece according to one embodiment.

[0064] [Fig.4B] illustrates a perspective view of a surface of a sandblasted decorative part.

[0065] [Fig.5] illustrates a top view of a surface of the semi-matte decorative piece according to one embodiment.

[0066] [Fig.6] illustrates another top view of a semi-matte decorative part surface according to one embodiment (FIG. 6A) and a top view of a sandblasted decorative part surface (FIG. 6B).

[0067] [Fig.7] illustrates at the top a system for measuring specular (FIG. 7A) or diffuse (FIG. 7B) reflection for a part according to the invention and for a polished part, and at the bottom a top view of the two parts as seen by the camera of the system.

[0068] [Fig.8] illustrates a diagram with the steps of the manufacturing process of a semi-matte decorative piece according to an embodiment of the invention.

[0069] Example(s) of embodiment(s) of the invention

[0070] Figure 1 illustrates a perspective view of an embodiment of a semi-matte decorative piece 1 according to the invention. In the illustrated example, the piece 1 is a link of a bracelet. The piece 1 of Figure 1 comprises a first surface 10 and a second surface 12, opposite the first surface 10. In the illustrated embodiment, the second surface 12 is parallel to the first surface 10. In the embodiment of Figure 1, the semi-matte decorative piece 1 is a single piece.

[0071] Although the semi-matte decorative piece of [Fig.1] is a link in a geometry and shape, the invention is not limited to such a geometry or shape, but applies to any other geometry, shape, proportions and / or dimensions.

[0072] The invention is also not limited to a link of a bracelet.

[0073] According to the invention, the decorative part 1 has a hardness equal to or greater than 800 HV and comprises a surface including scratches, a surface profile having an asymmetry in the range of -1 pm to -0.3 pm, a profile height in the range of 0.1 pm to 1.5 pm and a roughness in the range of 0.1 pm to 0.2 pm, so as to make the surface semi-matte.

[0074] In one embodiment, the decorative piece 1 is made of ceramic, metallic ceramic, sapphire and / or sintered glass.

[0075] Fig. 2 illustrates a portion of a cross-sectional diagram along line AA of Fig. 1 of the semi-matte decorative piece 1 of Fig. 1.

[0076] The surface 10 of the decorative piece 1 comprises valleys 13 and peaks 11. The peaks 11 are not necessarily periodic, i.e., regularly spaced, and may have different cross-sections, for example, but not limited to, inverted V-shaped, inverted U-shaped, etc. The semi-matte decorative piece 1 according to the invention may comprise peaks of different shapes.

[0077] In the embodiment of [Fig. 2], the peaks 11 are irregularly distributed over the surface. In other words, the peaks 11 are not arranged to form a matrix comprising rows and columns perpendicular to each other.

[0078] In the embodiment of [Fig.2], the bottom 130 of the valleys is located at a substantially constant depth of the semi-matte decorative piece according to the invention. Valleys of varying depths can also be considered.

[0079] In one embodiment, the average height between the valley depth and the peak height is within the range of 0.1 pm to 1 pm. This average height of the profile elements is defined over the evaluation length. This parameter is close to the R parameter of ISO 12085 and can be considered a pattern parameter (see ISO 25178).

[0080] In one embodiment, the height of the peaks and / or the depth of the valleys is irregular(s).

[0081] FIG. 3A illustrates a profile of a surface having a zero arithmetic mean roughness Rsk. FIG. 3B illustrates a profile of a surface having a positive arithmetic mean roughness Rsk. FIG. 3C illustrates a profile of a surface having a negative arithmetic mean roughness Rsk.

[0082] The asymmetry of the semi-matte decorative piece 1 according to the invention is negative (as in FIG. 3C).

[0083] Furthermore, tests carried out by the applicant have demonstrated that the asymmetry of the semi-matte decorative piece 1 according to the invention is more pronounced compared to that of a sandblasted surface, which belongs to the range -0.3 pm to -0.15 pm, which translates into deeper valleys and lower peaks.

[0084] Tests carried out by the applicant have demonstrated that the total height of the profile of the semi-matte decorative piece 1 according to the invention is smaller compared to that of a sandblasted surface, which belongs to the range 2 pm to 3 pm.

[0085] Tests carried out by the applicant have demonstrated that the average arithmetic roughness of the profile of the semi-matte decorative piece 1 according to the invention is smaller compared to that of a sandblasted surface, which belongs to the range 0.3 pm to 0.5 pm.

[0086] In one embodiment, the average height between the depth of the valleys and the height of the peaks of a semi-matte decorative piece 1 according to the invention is within the range of 0.1 pm to 1 pm.

[0087] Tests carried out by the applicant have demonstrated that the average height between the depth of the valleys and the height of the peaks of the semi-matte decorative piece 1 according to the invention is smaller compared to that of a sandblasted surface, which belongs to the range 1.3 pm to 2 pm.

[0088] Figure 4A illustrates a perspective view of a semi-matte surface of the decorative part according to one embodiment. Figure 4B illustrates a perspective view of a sandblasted surface of the decorative part. Figures 4A and 4B show the difference in roughness between the surfaces, in accordance with the measured values.

[0089] The sandblasted surface considered during the tests mentioned in relation to Figures 4B and 6B is a surface of a part having a hardness equal to or greater than 800 HV (specifically, a part made of the same material as the semi-matte part shown in Figures 4A and 6A) and obtained by sandblasting (with corundum powder), the sandblasting step being followed by a microblasting step using glass beads. This sandblasted part has a matte appearance.

[0090] Figure 5 illustrates a top view of a surface of the semi-matte decorative piece 1 according to one embodiment. The scratches that characterize the decorative piece according to the invention, resulting from the friction of the abrasive powder on the surface of the decorative piece 1, can be seen.

[0091] As seen in [Fig.5], in one embodiment, the distribution of the directions of the scratches on the surface is irregular, namely the scratches do not all have the same direction: on the contrary, each scratch has a direction which does not necessarily correspond to the direction of another scratch, these scratches being produced by scratching, impact or erosion.

[0092] As shown in [Fig. 5], in one embodiment, the density of scratches per unit area is uniform over the surface. As shown in [Fig. 5], in one embodiment this density is in the range of 100 to 400 scratches for a square surface of 100 sq m on each side, and preferably it is in the range of 180 to 220 scratches for a square surface of 100 sq m on each side.

[0093] In a preferred embodiment, the stripes are all substantially straight or rectilinear. As can be seen in [Fig. 5], in one embodiment, at least some of the stripes are not straight, for example they are curved.

[0094] As seen in [Fig.5], in one embodiment the length of scratches on the surface is in the range of 1 sqm to 70 sqm.

[0095] In one embodiment, the width of the stripes on the surface is in the range of 1 sqm to 5 sqm.

[0096] FIG. 6A illustrates another top view of a surface of the semi-matte decorative part 1 according to one embodiment. In this embodiment, the semi-matte decorative part 1 includes characteristic scratches of the process, resulting from the friction of the abrasive powder on the surface of the decorative part 1. These scratches are, for example, absent in a sandblasted surface, which has a granular and uniform appearance, as seen in FIG. 6B. FIG. 7A illustrates, at the top, a system 201 for measuring the specular reflection for a part 1 according to the invention and for a polished part 1' made of the same material, and at the bottom, a top view of the two parts 1, 1' as seen by the camera 22 of the system 201.

[0097] The system 201 includes a light source 20 and a camera 22. The camera 22 is placed at an angle α equal to the angle of incidence α of the light from the light source 20 on a surface of the part 1 or 1', with respect to the normal α to this surface of the part 1 or 1'.

[0098] FIG. 7B illustrates at the top a system 202 for measuring diffuse reflection for a part 1 according to the invention and for a polished part, 1' and at the bottom a top view of the two parts 1,1' as seen by the camera 22 of the system 202.

[0099] The system 201 also includes a light source 20 and a camera 22, but the camera 22 is placed at a different angle [3 (in the illustrated case, smaller) with respect to the angle of incidence a of the light from the light source 20 on a surface of the part 1 or 1', with respect to the normal n to this surface of the part 1 or 1'.

[0100] The measurement of the grey level on the image acquired by the cameras 22 of the two systems allows a quantitative comparison of the surfaces.

[0101] Tests carried out by the applicant with a part 1 according to the invention (white or black in color respectively) compared to a polished part 1' in the same material (white or black in color respectively) show that the specular reflection of the part according to the invention compared to the polished part decreases by up to 69% and the diffuse reflection of the part according to the invention compared to the polished part increases by more than 100%, for example up to 113%. In one embodiment, the semi-matte decorative part 1 is a link of a bracelet (for example of a wristwatch) or a watch bezel (for example of a wristwatch).

[0102] The present invention also relates to a watch, jewelry and / or jewelry item, comprising the semi-matte decorative piece 1 according to the invention.

[0103] Figure 8 illustrates a diagram with the steps of the manufacturing process of a semi-matte decorative piece according to an embodiment of the invention.

[0104] The method for manufacturing a semi-matte decorative part according to the invention comprises the steps of: - provide a decorative part, this decorative part having a hardness equal to or greater than 800 HV (step 100), - place the decorative piece in a barrel, the barrel containing an abrasive powder of a material chosen from at least one of the following materials: diamond, boron nitride, silicon carbide, alumina and / or boron carbide (step 200), - operate the barrel for at least 3 hours so that the decorative piece is set in motion at an average speed of between 0.5 m / min and 1.5 m / min, which makes it possible to obtain a surface profile with an asymmetry in the range of -1 pm to -0.3 pm, a profile height in the range of 0.1 pm to 1.5 pm and a roughness in the range of 0.1 pm to 0.2 pm, so as to make the surface semi-matte (step 300).

[0105] This solution therefore provides for a tumbling step with a specific type of abrasive, namely with an abrasive powder of a material chosen from at least one of the following materials: diamond, boron nitride, silicon carbide, alumina and / or boron carbide.

[0106] This abrasive powder has the particularity that its particles do not break (or break very little) during the tumbling process: this prevents the tumbling step from becoming a polishing step. Indeed, the parts produced are not polished parts, but semi-matte parts.

[0107] In one embodiment, the process includes a step (not illustrated) of unloading the barrel of semi-matte decorative pieces.

[0108] In one embodiment, the process includes a step (not shown) of cleaning the barrel, which generally follows the step of unloading the barrel.

[0109] In one embodiment, the process includes a step (not illustrated) of washing the semi-matte decorative parts, which generally follows the step of unloading the barrel.

[0110] In one embodiment, the process includes a step (not shown) of checking the semi-matte decorative part 1 which generally follows the unloading step of the barrel, for example an inspection step.

[0111] In one embodiment, the process includes a step (not shown) of polishing the decorative parts, which generally precedes step 200 of loading the barrel. In other words, in this embodiment, the process according to the invention makes it possible to "de-polish" previously polished parts, rendering them semi-matte.

[0112] In one embodiment, the particle size of the abrasive powder (namely, their largest dimension) is in the range of 5 µm to 50 µm, preferably in the range of 10 µm to 30 µm, for example in the range of 15 µm to 25 µm.

[0113] In one embodiment, the abrasive powder particles do not all necessarily have the same shape.

[0114] In one embodiment, the abrasive powder particles do not all necessarily have the same size.

[0115] In one embodiment, the abrasive powder used in the barrel is suspended in a liquid.

[0116] In one embodiment, the liquid includes a surfactant, for example an oil and / or a soap, in order to improve the suspension of the abrasive powder in the liquid.

[0117] In one embodiment, the process includes the step of putting several decorative pieces into the barrel, for example dozens, hundreds or thousands of decorative pieces.

[0118] In one embodiment, the process also includes the step of placing in the barrel with the decorative piece also media or "chips" which have their largest dimension belonging to the range 0.3 mm to 15 mm. These media can be cylindrical or any other shape. adapted shape. In one embodiment, the volume of media in the barrel is approximately at least 4 times the total volume of decorative pieces in the barrel.

[0119] In one embodiment, the decorative piece is made of ceramic, metallic ceramic (“cermet”), sapphire and / or sintered glass.

Claims

Demands

1. A method for manufacturing a semi-matte decorative part, the method comprising the steps of: - providing (100) a decorative part, this decorative part having a hardness equal to or greater than 800 HV, - placing (200) the decorative part in a drum, the drum comprising an abrasive powder of a material selected from at least one of the following materials: diamond, boron nitride, silicon carbide, alumina and / or boron carbide, - operating (300) the drum for at least 3 hours so that the decorative part is set in motion at an average speed of between 0.5 m / min and 1.5 m / min, which makes it possible to obtain a surface profile having an asymmetry (Rsk) in the range of -1 pm to -0.3 pm, a profile height (Rt) in the range of 0.1 pm to 1.5 pm and a roughness (Ra) in the range of 0.1 pm to 0.2 pm, so as to make the surface semi-matte.

2. A manufacturing method according to claim 1, the particle size of the abrasive powder being in the range of 5 pm to 50 pm, preferably in the range of 10 pm to 30 pm, for example in the range of 15 pm to 25 pm.

3. A manufacturing method according to any one of claims 1 or 2, the abrasive powder being suspended in a liquid.

4. A manufacturing process according to claim 3, the liquid comprising a surfactant.

5. A manufacturing method according to any one of claims 1 to 4, comprising a step of polishing the decorative parts prior to the step of loading (200) the barrel.

6. A manufacturing method according to any one of claims 1 to 5, comprising the step of putting into the barrel with the decorative piece also media which have their largest dimension belonging to the range 0.3 mm to 15 mm.

7. A manufacturing method according to any one of claims 1 to 6, the decorative piece being made of ceramic, metallic ceramic, sapphire and / or sintered glass.

8. Decorative part (1) having a hardness equal to or greater than 800 HV and comprising a surface including scratches, a surface profile having an asymmetry (Rsk) within the range of -1 µm to -0.3 µm, a profile height (Rt) within the range of 0.1 pm to 1.5 pm and roughness (Ra) within the range of 0.1 pm to 0.2 pm, so as to make the surface semi-matte.

9. Decorative piece (1) according to claim 8, being made of ceramic, metallic ceramic, sapphire and / or sintered glass.

10. Decorative piece (1) according to any one of claims 8 or 9, the distribution of the directions of the stripes on the surface being irregular.

11. Decorative piece (1) according to any one of claims 8 to 10, the density of scratches per unit area being homogeneous.

12. Decorative piece (1) according to any one of claims 8 to 11, the stripes defining valleys and peaks, the average height between the depth of the valleys and the height of the peaks being in the range 0.1 pm to 1 pm.

13. Decorative piece (1) according to any one of claims 8 to 12, the height of the peaks and / or the depth of the valleys being irregular(s).

14. Decorative piece (1) according to any one of claims 8 to 13, the length of scratches on the surface is in the range 1 pm to 70 pm and / or the width of scratches on the surface is in the range 1 pm to 5 pm.

15. A piece of watchmaking, jewelry and / or fine jewelry, comprising the decorative piece according to any one of claims 8 to 14.