Method for manufacturing a diamond mechanical part for a watch movement, and part manufactured according to said method

Abstract

Method for manufacturing a functional mechanical part (3) in single-crystal diamond, comprising the following steps: Laser cutting of the part in a single-crystal diamond plate; Polishing of a surface of the part by selective oxidation of carbon in non-diamond form on the surface.

Description

technical field

[0001] The present invention relates to a method for manufacturing a mechanical part for a watch movement, for example a wheel, pinion, pallet fork, escapement lever, balance spring, bridge, mainplate, rocker arm, leaf spring, or other micro-mechanical functional component in the regulating organ, gear train, or complication of the movement. The present invention also relates to a diamond part manufactured according to this method. State of the art

[0002] The mechanical parts of mechanical watch movements are most often made of metal. Moving parts, such as axles, wheels, pinions, the escapement lever, escape wheel, balance wheel, springs, and balance spring, are frequently made of steel, or Elinvar steel for the balance spring. The mainplate and bridges are generally made of brass or steel. Other materials are used less frequently, such as rubies for bearings or pallets, or ceramic for certain bearings.

[0003] Intensive research has been conducted to replace these conventional materials and avoid some of their drawbacks. For example, silicon is now used industrially for manufacturing components such as escapements and balance springs. EP732635A1 (CSEM) describes a micromechanical part, such as a watch movement anchor, cut from a silicon wafer by etching with a plasma gas around a pre-formed mask on the wafer's surface.

[0004] Silicon has the advantage of being easy to machine, reproducibly, using well-established technologies for manufacturing integrated circuits or MEMS, among other things. However, it has some drawbacks, notably an insufficient tribological surface finish and a relatively high coefficient of friction.

[0005] CH669109A1 (The Swatch Group R&D Ltd) suggests improving this surface finish by depositing a DLC (Diamond-Like Carbon) layer onto the silicon. Similarly, US2002 / 114225 (Damasko) describes, among other things, a steel escapement anchor coated with a DLC layer. US2012 / 0263909 (Diamaze Microtechnology SA et al.) describes another example of a mechanical part coated with diamond or a DLC layer.

[0006] DLC coatings possess some of the properties of natural diamond, although their crystalline structure is very different. Generally, these coatings are produced using a carbon deposition process such as plasma, filtered arc, ion beam, or sputtering. These rapid, high-energy processes do not allow the carbon atoms to arrange themselves in the typical sp3 cubic arrangement of diamond; the overall arrangement of atoms is amorphous, with a tangle of crystalline microstructures oriented differently from one another.

[0007] Furthermore, known DLC coating deposition processes generate a material containing significant proportions, greater than 10%, of hydrogen, graphitic carbon or other components.

[0008] A steel or silicon part coated with a DLC layer therefore exhibits improved tribological surface finishes, but these are still far from perfect. Furthermore, the adhesion of the DLC coating to the substrate is a weak point. In any case, the additional step required for the DLC layer deposition complicates manufacturing. Moreover, it is difficult to precisely control the shape of the part after coating deposition.

[0009] The anchors in the escapement of mechanical movements are subjected to particularly severe stresses. It is essential to minimize their mass and moment of inertia to limit the energy required for the high-frequency oscillation of these moving parts, and thus increase the watch's power reserve. The anchor, especially the pallet fork, is subjected to repeated shocks with each oscillation, or when the watch is subjected to impacts, and must therefore be sufficiently robust. Furthermore, a rigid anchor that does not deform with each oscillation is generally desired, which also limits the minimum thickness of the component.

[0010] We also know of micromechanical parts made of diamond. For example, WO2004 / 029733A2 (Fore Eagle Co Ltd) describes watch components made at least partially from this material. This document lists various advantages of diamond, including its hardness, low coefficient of friction, good shock resistance, high mechanical strength, high modulus of elasticity, low coefficient of thermal expansion, transparency, and scratch resistance.

[0011] DE102008029429A1 suggests manufacturing micromechanical watch parts from diamond or silicon coated with a DLC layer.

[0012] EP2407831A1 (Rolex SA) describes a balance spring for a watch oscillator that can be made from a low-density material such as silicon, diamond, or quartz. The balance spring can be produced by a chemical etching process using plasma ("DRIE, Deep Reactive Ion Etching").

[0013] CH701155B1 (Complitime SA) describes a balance wheel for a watch part comprising a board which can be made of diamond, quartz, silicon or corundum.

[0014] WO2005 / 017631 (Fore Eagle Co Ltd) describes another balance wheel made of diamond and obtained by chemical etching using a plasma.

[0015] EP2107434A1 describes a mechanical part, specifically an anchor wheel for watchmaking, made of silicon or diamond.

[0016] EP2233989 (Ulysse Nardin Le Locle SA) describes a diamond spiral spring obtained by deep engraving.

[0017] CH701369 describes a diamond barrel spring.

[0018] The type of diamond used for the above pieces is not usually specified in these documents. In practice, it is always polycrystalline synthetic diamond, which costs 10 to 50% less than natural diamond and can be produced in shapes suitable for the intended use.

[0019] Several methods for manufacturing synthetic diamonds are known. US8088221B2 (Z. Shapiro) describes a low-temperature, relatively low-pressure process for manufacturing synthetic diamonds. EP2189555A2 (Appollo Diamond Inc.) describes another synthetic diamond production process. CVD growth and explosive detonation processes have also been suggested, notably in US2003 / 205190.

[0020] DE102008029429 concerns watch parts, for example, oscillating organ components, made of single-crystal or polycrystalline diamond, which can be obtained by laser cutting. A coating is recommended to improve tribological properties and hardness.

[0021] WO99 / 22049 describes various methods for polishing a diamond surface obtained by CVD, as does US2003 / 205190. Methods for polishing a diamond surface are also described in EP2511229 and WO01 / 75197.

[0022] JP2006 / 273704A describes a process for manufacturing a nanodiamond polishing powder. This process is not intended for the manufacture of functional mechanical parts for watch movements and does not include a polishing step. Brief summary of the invention

[0023] There is a need, particularly in mid-range and high-end watchmaking, for micro-mechanical components made from materials offering a better compromise between the desired properties of hardness, mechanical resistance, lightness, low thermal expansion, stability of the modulus of elasticity, and ease of high-precision machining.

[0024] One aim of the present invention is therefore to propose a method for manufacturing a mechanical part for watchmaking application which offers such a compromise between these different properties.

[0025] According to the invention, these goals are achieved in particular by means of a process for manufacturing a functional mechanical part made of single-crystal diamond, comprising the following steps: Laser cutting of the part from a single-crystal diamond plate; polishing of one surface of the part by selective oxidation of carbon in a non-diamond form. For the purposes of this application, a functional mechanical part is defined as a part that performs a mechanical function, such that it cannot be removed without affecting at least one function of the watch movement. A purely decorative part, or a watch case element, is therefore not considered a functional mechanical part.

[0026] Polycrystalline diamonds, known in the prior art for manufacturing mechanical parts, are extremely hard, harder than common natural single-crystal diamonds. However, contrary to popular belief, such high hardness is not always necessary or even advantageous for a watch component. This hardness results in high polishing costs and faster wear of the softer parts in contact with it.

[0027] Polycrystalline diamonds are also most often transparent or grey; due to the multiple interfaces between the different crystal grains with different orientations, they produce little or no reflections, and practically no iridescence effects.

[0028] The invention is based in particular on the observation that monocrystalline diamond has many advantages over the more widespread polycrystalline diamond, and even more so over DLC coatings.

[0029] In particular, single-crystal diamonds have the advantage over polycrystalline diamonds of being extremely strong; no crack initiation occurs between the individual grains. This strength allows for the production of thinner, and therefore lighter, parts with the same strength. For example, it is possible to manufacture parts such as, without limitation, anchor wheels or anchors with a thickness of less than 120 microns, preferably less than 100 microns, for example, between 20 and 60 microns, using single-crystal diamonds. In the case of a pallet, the thickness is advantageously between 100 and 400 microns, for example, 320 microns, or between 100 and 160 microns, preferably between 100 and 120 microns. Such thicknesses would be practically impossible to achieve with parts made of steel, silicon or polycrystalline diamond, as these parts would be too fragile and very difficult to assemble without breaking them.

[0030] Thanks to this extreme thinness, it is possible to reduce the thickness of the movement and, more importantly, to reduce the inertia of the moving parts. This increases the watch's power reserve and the oscillation frequency of the regulating organ.

[0031] Single-crystal diamonds can be made in a wide variety of colors, including transparent, black, blue, yellow, red, etc. Furthermore, the interplay of light reflecting off different faces oriented in various ways produces highly prized iridescent effects.

[0032] On the other hand, single-crystal diamonds generally have a smoother surface state than polycrystalline diamonds or DLC coatings, whose grain structure does not allow for an optimal tribological surface.

[0033] Synthetic single-crystal diamonds can, for example, be obtained by growing carbon via CVD around a single-crystal diamond seed. It is important that the seed be made of single-crystal diamond so that the deposited structure is itself single-crystal. The carbon can be obtained from methane in a CVD reactor.

[0034] Single-crystal synthetic diamond can also be obtained by compressing carbon at high pressure and high temperature.

[0035] The invention also stems from the observation that single-crystal diamond can be precisely cut using a laser beam. However, this cutting process has the drawback of releasing carbon atoms onto the surface, which are deposited on the surface of the crystalline diamond as graphite or in another non-diamond form (i.e., in a non-crystalline structure, or as a crystal other than diamond). This results in a black, unsightly surface and a surface friction coefficient that is lower than that of polished diamond.

[0036] According to one aspect of the invention, these non-diamond carbon residues (for example graphite) are eliminated by oxidation, without attacking the carbon with a diamond structure.

[0037] Oxidation is achieved by heat treatment at a temperature between 600°C and 750°C, preferably between 650°C and 680°C.

[0038] Oxidation can also be achieved through surface treatment with oxygen or fluorine plasma.

[0039] The oxidation process allows the part to be polished by burning off impurities, sharp points, cutting waste, and carbon in the form of graphite on the surface.

[0040] The process may include an additional step of polishing a surface using ion beams.

[0041] The mechanical part may also have lateral surfaces. At least a portion of these mechanical surfaces may be polished or corrected, for example, with a laser beam or an ion beam. Advantageously, at least a portion of these surfaces is corrected to achieve a tribological state better than before the correction. At least a portion may be corrected so that it is substantially perpendicular to the lower and upper faces of the part.

[0042] The invention also relates to a method for manufacturing a functional mechanical part made of single-crystal synthetic diamond, comprising the following steps: Provision of a single-crystal diamond seed; Carbon deposition by CVD process on said diamond seed; Simultaneously, introduction of doping impurities during diamond growth.

[0043] The invention thus starts from the observation that doping makes it possible to control various mechanical and / or optical properties of the part, for example its hardness, its modulus of elasticity, the variation of the modulus of elasticity as a function of temperature, its color etc.

[0044] The diamond preferably contains a maximum of 3% doping impurities, without affecting its single-crystal structure. This threshold allows for modification of the desired mechanical properties of the diamond without altering its single-crystal structure.

[0045] Doped single-crystal diamond is obtained by intentionally introducing a doping element into the diamond, either during the growth of a synthetic diamond, or into a synthetic or natural diamond that has already been formed.

[0046] The doping process makes it possible to produce a diamond that differs from naturally occurring diamonds and from undoped synthetic single-crystal diamonds. The difference stems from the type of impurities, their distribution, and / or their concentration. The doping is chosen to modify the mechanical and tribological properties of the diamond piece.

[0047] At least one doping is advantageously carried out in the mass of the part, in a homogeneous manner, so as to affect the mechanical properties of the whole of the part, in depth.

[0048] This doping can be carried out with virtually no additional cost during the growth of a single-crystal synthetic diamond.

[0049] Doping can also be performed on the surface. The doping method may differ between the surface and the depths. The doping density may differ between the depths and the surface. The doping agent may differ between the surface and the depths. Impurities may be introduced differently between the surface and the depths.

[0050] The diamond may be a boron-doped black diamond.

[0051] Impurities can be introduced into the diamond during the organic growth of the diamond.

[0052] In one embodiment, the mechanical part made of doped single-crystal diamond can be a flat part, for example a part used in the regulating organ of a mechanical watch, for example an anchor or an anchor wheel.

[0053] The mechanical part can be a flat piece made by cutting from a flat plate. The cutting is done by laser.

[0054] The mechanical part can be a multi-level flat part obtained by thermochemical attack from a single-level flat part.

[0055] The flat mechanical part can be a balance spring for the regulating organ of a mechanical watch. The high rigidity of single-crystal diamond allows for high oscillation frequencies with small-diameter balance springs.

[0056] The mechanical part can be a spring, for example a rocker spring, a flat spring, etc.

[0057] The mechanical part can also be a pallet intended to equip an escapement anchor made of another material, for example a steel anchor.

[0058] The mechanical part can also be a bridge, a plate, etc.

[0059] The mechanical part made of single-crystal diamond can be rigid, for example in the case of a bridge, a plate, a rocker, a pallet, an anchor, a wheel, etc.

[0060] The mechanical part made of single-crystal diamond can be flexible, for example in the case of a spiral, a spring, a flexible blade, etc.

[0061] The flat part can be made by cutting a wafer of doped single-crystal diamond.

[0062] The invention also relates to a watch movement comprising at least one part made of doped single-crystal diamond, for example an anchor, an anchor pallet, an anchor wheel or a balance spring made of doped single-crystal diamond.

[0063] Different mechanical parts of the same movement can be made from different varieties of single-crystal diamond. For example, different mechanical parts of the same movement can be made from different colors of single-crystal diamond. It has been noted in the context of this invention that the color of the single-crystal diamond, which is due to impurities, influences its hardness. For example, transparent single-crystal diamond is less hard than black single-crystal diamond doped with boron ions. The type or color of single-crystal diamond chosen for different parts of the same movement is therefore determined according to the desired hardness, or according to other mechanical properties dependent on that color.

[0064] To reduce wear, it is advantageous for the pallets of the escapement lever, or the entire lever assembly if the pallets are integrated, to be harder than the escape wheel with which they interact; an escape wheel that is less hard than the pallets helps to absorb shocks. In one embodiment, the watch movement includes, for example, an anchor or pallet fork made of a hard single-crystal diamond, and an escape wheel made of a less hard single-crystal diamond. The anchor or pallets could, for example, be made of a boron-doped black single-crystal diamond, while the escape wheel could be made of a transparent or yellow single-crystal diamond.

[0065] In general, the movement may include several single-crystal diamond parts with different doping levels.

[0066] The process may include an additional step of surface doping by injecting dopant ions onto the surface using an ion beam.

[0067] Impurities may contain boron, which increases hardness without affecting the crystalline structure of diamond. Brief description of the figures

[0068] Examples of implementation of the invention are given in the description illustrated by the accompanying figures, in which: THE figures 1A to 1E illustrate different successive stages of a manufacturing process for a mechanical part according to the invention. figure 2 illustrates an example of a mechanical part according to the invention. The Figures 3A to 3B schematically illustrate a polishing or grinding operation on at least a portion of the lateral sides of a part according to the invention. figures 4A to 4C schematically illustrate a diamond slicing process. figure 5 schematically illustrates the cutting of a pallet according to the invention. Example(s) of an embodiment of the invention

[0069] THE figures 1 to 3schematically illustrate a manufacturing process for a functional mechanical part according to the invention.

[0070] There Figure 1A illustrates an uncut single-crystal diamond 1 used to manufacture one or more pieces according to the invention. The single-crystal diamond may be a natural diamond or a synthetic diamond, advantageously weighing more than 1 carat, preferably more than 3 carats.

[0071] In the case of a natural diamond, it may be a diamond with a shape or other properties that make it unsuitable for use in jewelry.

[0072] A synthetic single-crystal diamond can be produced, for example, using a filtered arc to deposit carbon onto a single-crystal diamond seed crystal, without the addition of hydrogen or other materials. Another possibility is to perform CVD deposition of carbon produced from a hydrocarbon such as methane onto a single-crystal diamond seed crystal. The seed crystal can be reused after cutting plates from the mass deposited above it.

[0073] A third, less advantageous possibility is to produce a synthetic single-crystal diamond by subjecting a carbon source to simultaneous high temperature and high pressure. Other processes could also be used.

[0074] The single-crystal diamond thus formed can be doped. In one embodiment, the doping agent can be introduced during the formation of the synthetic diamond, for example, by adding traces of the doping agent to the filtered arc or within the CVD reactor. In another embodiment, the doping agent is added after the formation of the synthetic diamond, for example, by means of a high-energy ion beam. Doping can be carried out homogeneously throughout the entire mass of the diamond, and / or only on the surface. An initial doping can be performed throughout the mass, and a different doping, for example, with a different doping agent and / or at a different concentration, can be carried out on the surface.

[0075] Doping can be selected to modify the hardness of parts produced from this diamond; depending on the doping agent, it is possible to increase or decrease this hardness. For example, the inclusion of nitrogen as a doping agent reduces the hardness of a part, while the inclusion of boron ions increases it.

[0076] In one embodiment, the hardness of a single-crystal diamond pallet is increased by doping, for example, by including boron ions, while a single-crystal diamond escape wheel intended to work with this pallet in the escapement is either undoped or doped to reduce its hardness, for example, with nitrogen, to obtain a hardness lower than that of the pallet. It is advantageous to have very hard pallets to reduce their wear and the coefficient of friction on the impulse plane, and a less hard escape wheel to absorb the shock of the pallet with each oscillation. In another embodiment, the escape wheel is doped with a relatively high concentration of nitrogen, while the pallet is doped with a lower concentration of nitrogen.The inclusion of nitrogen during the manufacture of synthetic single-crystal diamond by CVD growth makes it possible to increase the speed of manufacture, and therefore reduce the cost, while obtaining paddles that remain harder than conventional ruby ​​paddles.

[0077] Doping can also be selected to control the diamond's color. Doping can be chosen to control the diamond's Young's modulus. Doping can be chosen to reduce the Young's modulus's sensitivity to temperature, in order to produce parts whose stiffness is as independent of temperature as possible. Doping can be chosen to reduce the diamond's coefficient of thermal expansion, in order to produce parts whose dimensions are as independent of temperature as possible.

[0078] The doping agent and its concentration are also chosen so as not to interfere with the single-crystal structure of the diamond, or to minimize this interference. In one embodiment, the diamond is doped with boron ions. Different diamonds used for the production of different components in the same watch can be doped differently depending on the desired properties.

[0079] Boron doping during the organic growth of synthetic diamond has the advantage of producing a non-radioactive black diamond, unlike doping processes by introducing high-energy ions.

[0080] The single-crystal diamond 1 is then cut as illustrated in the figure 1B, for example by means of a diamond saw, or split using a hammer and blade, an electric arc, an ion beam, or preferably cut using a laser so as to obtain a flat surface 10. The laser is advantageously a pulsed laser, for example a pulsed laser at a frequency of 5 to 40 GHz.

[0081] In the embodiment illustrated on the figures 4A to 4C The diamond is sliced ​​from one side by means of a first laser beam 20. The laser beam is pivoted by means of a movable mirror, so as to emit in a cone with an opening angle of less than 5°. The diamond is then attacked from the other side by means of another laser beam 21 pivoted in a cone ( figure 4BIt is also possible to use the same laser beam to process both sides of the workpiece, flipping it between the two cuts. This cone-shaped machining widens the ablation zone and avoids poor surface finishes and destruction of the crystalline structure that can occur if ablation were performed in a narrow channel, causing excessive temperature rise. The process is comparable, in some ways, to that of a lumberjack cutting a log with two angled cuts from either side.

[0082] The convex surface thus produced by this cutting is then rectified or flattened, as illustrated on the figure 4CThis is achieved by means of a laser beam oriented parallel to the surface of the plate to be produced. The pulse frequency of this laser can be, for example, between 10 and 100 kHz, in order to obtain a precise cut without the problems of alterations to the crystalline structure caused by the high energy of more rapidly pulsed lasers.

[0083] It is possible to scan the rough diamond beforehand using a 3D scanner in order to determine the optimal cutting plane to obtain the maximum number of pieces and / or to facilitate cleaving; for example, a cut along a tetrahedral plane of the crystal will be preferred because it is faster and allows for a cleaner surface.

[0084] In a first embodiment, the cutting plane is determined to obtain an active surface of the workpiece oriented along the crystal plane {111}, which is generally the hardest. In the case of a plate intended for manufacturing a watch balance spring, the cutting plane is preferably parallel to the {111} plane of the diamond. In the case of a plate intended for manufacturing pallets for a watch escapement, the cutting plane is preferably distinct from the {111} plane and chosen so as to allow the cutting of pallets whose impulse surface, obtained in the edge of the cut plates, is parallel to the crystal orientation plane {111}.

[0085] However, it has been observed within the scope of the invention that even though the crystalline plane {111} is the hardest, this hardness decreases very sharply in the event of a slight deviation from this ideal plane. For example, a part cut or polished along a plane that deviates by even a few degrees from the plane {111} exhibits significantly reduced hardness and surface finish. It is, however, difficult, particularly in industrial manufacturing, to produce parts with surfaces oriented precisely along the plane {111}, without any deviation. Furthermore, it is sometimes desirable to produce paddles with a non-planar impulse surface.

[0086] Therefore, in a preferred embodiment, the cutting plane is determined to obtain an active surface of the workpiece oriented substantially along the crystal plane {001} or, preferably, along the plane {011}. Although less hard than the ideal plane {111}, these planes are less sensitive to deviations from the ideal surface. In the case of a plate intended for manufacturing a watch balance spring, the cutting plane is preferably substantially parallel to the plane {001} or {011} of the diamond. In the case of a plate intended for manufacturing pallets for a watch escapement, the cutting plane is preferably chosen to allow the cutting of pallets whose impulse surface, obtained in the edge of the cut plates, is substantially parallel to the crystal orientation plane {001} or to the plane {011}. "Substantially parallel" here means that the deviation after polishing is at most ±5°.

[0087] It is possible to hold diamond 1 during cutting, for example by cementing it or gluing it to a temporary support.

[0088] The rough face 10 obtained at the end of this cutting process is then rectified and / or polished to obtain a flat polished face 11 as illustrated in the figure 1C .

[0089] The rectification of face 11 can be carried out, as indicated, by means of a laser, for example a pulsed laser between 10 and 100KHz.

[0090] The polishing of face 11 can be carried out on a rotary grinding wheel covered with synthetic diamond powder, for example polycrystalline diamond powder.

[0091] The roughness of face 11 can also be reduced by means of a high-energy ion beam parallel to the surface.

[0092] The diamond is then cut along a new cut parallel to the first cut, in order to obtain a thin plate 2 as illustrated in the figure 1D This delicate cut is advantageously performed by laser to avoid impacts that could break the plate. Like the cut on the top surface, this cut can be made using the method illustrated in the diagram. figures 4a to 4c that is, by means of one or two laser beams deflected by a mirror to produce a conical ablation zone.

[0093] Depending on the type of part desired, this process allows for the cutting of extremely thin plates in a single-crystal diamond, for example plates with a thickness of less than 400 microns, for example plates with a thickness between 100 and 400 microns, for example 320 microns, or between 100 and 160 microns, ideally between 100 and 120 microns, in the case of plates intended for machining pallets, and plates with a thickness between 20 and 120 microns, for example between 40 and 80 microns, for example 60 microns, in the case of manufacturing anchor wheels, anchors, wheels, spirals, springs or rockers for example.

[0094] This characteristic makes it possible to manufacture extremely lightweight parts and therefore reduce the energy required to move them.

[0095] The underside 12 of plate 2 is relatively rough. For many applications, particularly in watchmaking, this less-than-perfectly polished appearance is entirely satisfactory since this side is not visible. However, by producing a slightly thicker part, it is possible to also polish this side 12, for example, by mechanical polishing on a grinding wheel and / or laser. In one embodiment, the part is held without adhesive during polishing, preferably using a vacuum. This allows for very precise control of the part's thickness after polishing, without this thickness depending on the thickness of the adhesive.

[0096] The produced plate 2 can be visually inspected to eliminate plates with excessive impurities or a non-single-crystal structure. In one embodiment, this inspection is performed by illuminating the plate with polarized light, highlighting imperfections. The inspection can be carried out manually or using a camera and image analysis software.

[0097] During the step illustrated on the figure 1E Part 3 is cut from the surface of plate 2. This cut is obtained, for example, by means of a laser beam perpendicular to one of the surfaces 11, 12, or to the median plane of plate 2. In the example of figures 1E And 2Part 3, cut in this way, is an escapement lever for a watch movement. It is also possible to produce other micromechanical parts using the process described above, for example, an escape wheel, a balance spring, or another type of wheel. Several different parts can be cut from a single sheet.

[0098] There figure 5Figure 6 illustrates an example of a possible laser beam path during the machining of a pallet in a plate 11. The laser beam can have a relatively large dimension, for example, a maximum diameter on the order of 20 microns. The shape of this beam 6 is generally non-circular, for example, elliptical. The cutting path is therefore advantageously determined by software designed to determine a beam path that takes into account the size, shape, and orientation of this beam relative to the workpiece, so as to obtain a workpiece after release whose dimensions correspond to the desired dimensions.

[0099] The trajectory is preferably initiated at a distance from the part to be produced, on a portion 32 that does not belong to the part being produced. This avoids deformations due to the initial drilling. Furthermore, the trajectory is preferably optimized, taking into account the crystalline orientation of the diamond, so that any cracks propagating from the ablation point have the greatest possible chance of following the edge of the part, or of moving away from it. For example, on the figure 5 The maximum risk of cracking occurs from the initial drilling point 32; therefore, the position of this point is preferably chosen so that the most probable crack direction follows exactly the line followed by the beam.

[0100] As mentioned above, the workpiece to be cut is oriented on the diamond plate 11 so that the active surface of the workpiece lies in the crystal plane {111}. In the illustrated case of a pallet, the active surface 31 is the impulse surface (planar or non-planar) intended to be brought into contact with the anchor wheel. The pallet is therefore cut from the plate 11 so that this surface 31 lies precisely in the plane {111}.

[0101] Item 33 on the figure 5 These are cutting guides used during the subsequent polishing stage to define the ideal polishing depth. Polishing will therefore be carried out precisely until these marks disappear completely.

[0102] Other plates similar to plate 2 can then be cut from the same diamond 1, in order to make other pieces identical to, or different from, piece 3.

[0103] In one embodiment, facets are obtained by cutting and / or polishing one of the upper and / or lower faces 11 or 12, so as to control the direction in which light passes through the part 3 and the reflections or iridescence produced on the different faces. The part remains essentially flat, however; in a preferred embodiment, the ratio between the thickness and the shortest length is greater than 10, advantageously greater than 50, for example greater than 100.

[0104] It is also possible to cut a logo, inscription, or design into part 3 using a laser. This cut can be through or blind; for example, it provides protection against counterfeiting by making copying extremely difficult.

[0105] The laser cutting process in a plate 2 of part 3 has the disadvantage of producing lateral flanks 13 that are not perpendicular to the faces 11, 12, as shown in an exaggerated manner on the figure 3ASince diamond is more or less transparent, the cut is actually achieved by the plasma produced by the interaction between laser light and air. This results in non-perpendicular and slightly uneven edges. This surface quality is generally not problematic for parts 3 or portions of parts 3 that are not intended to come into contact with other parts. In some cases, however, these irregular surfaces are undesirable, either for aesthetic reasons or because it is necessary to precisely control the shape of the part and the amount of material, for example, in the case of a balance spring. Therefore, in the case of a part or portion of a part intended to come into contact with other movement components, it is advisable to control the profile and surface finish of the edges 13.These requirements are particularly important if part 3 is an anchor pallet, a portion of an anchor forming a pallet, or a tooth of an anchor wheel or other wheel.

[0106] In such a case, an optional operation to grind the flanks 13, or at least a portion of these flanks, can be carried out using a laser or a grinding wheel in order to obtain smoother flanks 14 that are perpendicular to the surfaces 11, 12, as illustrated in the figure 3BIn the case of a pallet, at least the active surface 31 can be ground to the depth of the mark 33 using a grinding wheel coated with polycrystalline diamond powder. In the case of an anchor wheel, the portion of each tooth intended to contact the pallet can be polished or ground using a laser beam. In the case of a rotating part, for example a wheel or a pallet, this grinding is preferably carried out by orienting the grinding wheel relative to the part so as to grind in a direction substantially parallel to the tangent of the part, thus creating micro-grooves parallel to the direction of friction of the part during its use.

[0107] The surfaces of the resulting part 3 are preferably uncoated; single-crystal diamond has a virtually ideal surface finish, both aesthetically and in terms of coefficient of friction and impact resistance, for example. However, surfaces 11, 12, 13, or 14 may sometimes be covered with traces of graphite-enhanced carbon resulting from the destruction of the diamond structure during cutting or polishing operations. To eliminate these traces, the invention allows the part 3 to be subjected to heat treatment, for example, by leaving it for a few seconds or minutes in an oven between 600° and 750°C, preferably between 650° and 680°C, preferably at ambient temperature. This operation burns off the residual graphite on the surface without affecting the carbon in its diamond form, thus improving the surface finish of the part.It is also possible to use a lower temperature with a higher oxygen level, or to oxidize non-crystalline carbon without attacking diamond by using, for example, an oxygenated or fluorinated plasma.

[0108] This operation also allows the palette to be polished by burning the points on the surface.

[0109] The produced part can also be polished using an ion beam ("ion etching"), for example, an ion beam parallel to the surface to be polished. In one embodiment, this ion etching is performed after heat treatment polishing.

[0110] The finished piece can also be polished using ultrasound. It can be cleaned with gasoline to improve the diamond's appearance.

[0111] A mechanical watch movement within the scope of the invention may comprise one or more components 3 made of single-crystal diamond. The hardness of each component 3 can be chosen by selecting the type and color of diamond. For example, a component requiring maximum hardness could be made of synthetic diamond, such as boron-doped black synthetic diamond. A component for which such high hardness is not desired could be made of transparent synthetic diamond, natural diamond, etc. Different diamond components of different colors and types can be combined in a single movement. For example, it is advantageous to make a pallet fork or pallet fork from very hard single-crystal diamond and an escape wheel from slightly less hard single-crystal diamond to absorb shocks. Reference numbers used in the figures

[0112] 1. Single crystal diamond 10. Unpolished cut face 11. Polished cut face 12. Unpolished opposite face 13. Unground side face 14. Ground side face 2. Cut diamond plate 3. Functional mechanical part

Claims

1. Method for manufacturing a functional mechanical component (3) for a watch movement, comprising the following step: laser cutting the component (3) in a monocrystalline diamond plate, wherein the method further comprises the step of polishing a surface of the component by selective oxidation of carbon in non-diamond form on the surface by heat treatment at a temperature between 600°C and 750°C.

2. Method according to claim 1, wherein said oxidation is achieved by heat treatment at a temperature between 650°C and 680°C.

3. Method according to any of claims 1 to 2, wherein said plate is a synthetic diamond plate obtained by the following method: Providing a monocrystalline diamond seed; Carbon deposition by CVD process on said diamond seed; Simultaneous introduction of doping impurities during diamond growth.

4. Method according to one of claims 1 to 3, comprising a step of surface doping by injecting doping ions into the surface by means of an ion beam.

5. Method according to one of claims 3 to 4, wherein the doping comprises boron.

6. Method according to one of claims 3 to 5, wherein the doping comprises nitrogen.

7. Method according to one of claims 1 to 6, comprising a step of polishing a surface by ion beams.

8. Method for manufacturing a mechanical component according to one of claims 1 to 7, wherein the diamond is homogeneously doped into the mass of the part.

9. Method for producing a mechanical component according to one of claims 1 to 8, wherein the diamond is doped differently at the surface than in the depth of the component.

10. Method for manufacturing a component according to one of claims 1 to 7, wherein the thickness of the component (2) is between 20 and 400 microns.

11. Method for manufacturing a component according to one of claims 1 to 7, wherein the said component consists of a spring or a rocker.

12. Method for manufacturing a clockwork with at least one functional mechanical component (3) which has been manufactured in accordance with the method according to one of claims 1 to 11.

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