GRINDING PROCESS

Description

technical field

[0001] The present invention relates to an abrasion process, in particular sanding of parts, for example metallic and / or composite materials, in particular parts intended for the aeronautical, automotive, naval, wind turbine or other industries. Previous technique

[0002] Abrasion processes include sanding, polishing and grinding, sandblasting and water jet blasting.

[0003] During the manufacture of an industrial part, it comprises several layers of base, preparation and finishing materials, all of which may themselves consist of several sub-layers.

[0004] The purpose of preparation layers is to mitigate defects at different scales: micro- and macro-geometric. For micro-geometric defects, primer materials known as "pore fillers" are typically used, while for macro-geometric defects, putties are preferred, both being applied in layers. These two types of layers are deposited one on top of the other, particularly to fill visible defects on the part.

[0005] Before applying a finishing coat, such as paint, a surface preparation phase, particularly sanding, is generally carried out to create a smooth surface with as little material as possible. Indeed, especially in the aerospace industry, the total mass of a part must be as low as possible to conserve energy during operation. The goal is therefore to sand off excess material while preserving the structural and functional performance of the part. For example, "structural" can refer to the mechanical strength of the part, and "functional" to its aerodynamic performance. The objective of sanding is thus threefold: to prepare the surface and to remove material without removing too much.

[0006] It should be noted that some parts have underlayers that must not be touched. In aeronautics, for example, there is the lightning wire mesh layer which provides the part with resistance to lightning strikes.

[0007] There is currently no automated way to precisely control material removal by abrasion, particularly by sanding, without risk of damaging the finished part.

[0008] Sanding is generally done manually. This allows for some control over material removal, but not enough to automate the process. Achieving a smooth surface is also very difficult with manual operations. Finally, there is no real repeatability, despite the operators' experience, and each piece exhibits different defects.

[0009] It is therefore difficult to automate this process at present. However, this automation is absolutely necessary given the low added value of this operation. To achieve this transformation, it is essential to have better control over the amount of material removed and remaining on the part.

[0010] US 2002 / 072297 A1 describes an automated surface finishing device and method, particularly for aircraft panels, for correcting surface defects. The device comprises a controller, multiple scanning means, and surface finishing tools, which enable the detection and treatment of surface defects.

[0011] Document DE 10 2015 119 240 B3 presents an automated method for detecting defects on the surface of a part. The method locates and categorizes surface defects based on their topography. The document also describes a method for processing the detected defects using a robot.

[0012] There is currently no solution that allows for safe, fast and relatively inexpensive control of the surface preparation of a multi-layer or single-layer part, particularly metallic, by removing material using abrasive processes such as, for example, grinding, sanding, polishing, sandblasting and water jet.

[0013] The invention therefore aims to meet this need. Description of the invention

[0014] The present invention thus relates to an abrasion process according to claim 1.

[0015] The process may include at least one repetition of steps (a) to (c) and possibly at least one repetition of step (d).

[0016] The process may in particular include several repetitions of steps (a) to (d), preferably at least two repetitions, for example five repetitions, the last repetition not including step (d).

[0017] Thanks to the invention, information can be obtained about the surface of the workpiece, allowing for adjustment of the abrasion process, including the abrasion parameter(s) and the trajectory followed. Specifically, this method allows, rather than tracking the material removed from the workpiece by abrasion, tracking, analyzing, and studying the material remaining on the workpiece.

[0018] The term "workpiece surface" refers to the portion of the workpiece surface to be abraded. This portion may correspond to the entire workpiece surface or only a part of it. In the latter case, a portion of the entire surface is to be abraded.

[0019] In one embodiment, the abrasion machine moves relative to the workpiece during the abrasion step (d), the workpiece preferably being stationary. In another embodiment, the workpiece is moved relative to the abrasion machine during the abrasion step (d), the abrasion machine preferably being stationary. In yet another embodiment, the workpiece and the abrasion machine are mobile relative to each other during the abrasion step (d).

[0020] The abrasion machine can be programmed with predetermined initial abrasion parameters and an initial abrasion path. During step (c) of the abrasion process, one or more of these parameters and / or the abrasion path are determined, for example, by maintaining their initial characteristics or adjusting them. The abrasion path can thus be predetermined, particularly the initial abrasion path, with step (c) then consisting of adjusting it if necessary.

[0021] The process includes, for example, after step (c) setting up the abrasion machine with said at least one abrasion parameter and / or the abrasion trajectory.

[0022] Said at least one abrasion parameter may be variable or not during the abrasion trajectory carried out in step (d), in particular depending on the values ​​assigned for the elementary zones or sets of elementary zones.

[0023] Said at least one characteristic of the part is preferably chosen from the group consisting of a colour, a dimension, in particular a thickness, a surface condition such as a gloss or roughness, a radiation, preferably the colour.

[0024] When the characteristic consists of color, one can, for example, detect changes in the color of the surface.

[0025] At least one feature of the part may be a feature of the part's surface. When the process includes the step of acquiring data relating to at least two features of the part, at least one of these features may be a feature relating to the part's surface, for example, color or surface finish.

[0026] This at least one sensor is specifically chosen from the group consisting of contact or non-contact sensors based on optical, mechanical, magnetic, capacitive, acoustic, radiation, and piezoelectric technologies. This at least one sensor may be chosen from the group consisting of, among others, cameras, color sensors, and thermocouples.

[0027] The sensor allows the acquisition of data relating to the characteristic.

[0028] Said at least one abrasion parameter may be chosen from the following: feed rate, rotational speed or feed rate of the abrasive tool, force applied by the abrasive tool to the workpiece surface, nature, shape and / or size of the abrasive tool, angular orientation of the abrasive tool relative to the local normal of the workpiece surface

[0029] By carrying out the data processing step, we can deduce the adjustment of one or more parameters, for example from those indicated above, and also that of the abrasion trajectory of the machine and / or the part, relatively.

[0030] Step (c) of determination may include a comparison, for each elementary zone, of said assigned value with a predetermined threshold value.

[0031] When, by implementing the comparison, the threshold value for said at least one characteristic of the part is reached in at least one elementary zone of a set of elementary zones, the abrasion trajectory is advantageously determined so that there is no further abrasion in the set of elementary zones concerned.

[0032] When, through the implementation of the comparison, the threshold value for at least one characteristic of the part is reached for at least a predefined percentage of the surface, elementary zones, or set(s) of elementary zones, in particular at least 80% of the surface, or even greater than 80%, with this percentage potentially reaching 100%, the abrasion process is stopped. It should be noted that to reach the threshold value for more than 80% of the part's surface, it may be necessary to change all or part of the abrasive tool, in particular changing the abrasive paper, the abrasive pad, and / or the abrasive tool itself.

[0033] Abrasion advantageously consists of sanding. It may also consist, either partially or in part, of polishing or grinding, or even any other abrasive process. The abrasion machine comprises an effector with an abrasive tool that includes an abrasive pad, which may support abrasive paper. The abrasive tool, effector, pad, and / or paper can be adapted as needed.

[0034] The surface of the part may include a peripheral portion near at least one edge of the part at a predetermined distance from it, said peripheral portion may not be treated by the abrasion machine or may be treated at least partially with the abrasion machine of which a part has been changed, in particular of which an abrasive plate of the abrasion machine has a smaller diameter, automatically or manually.

[0035] The workpiece is advantageously a workpiece with a flat or curved surface, for example with a radius of curvature between 3 and 5 m. The workpiece treated by the process according to the invention is, for example, relatively larger than the size of the abrasive tool.

[0036] The method may employ two sensors, either of the same or different types, for the acquisition step (a). If the two sensors are different, this allows for the acquisition of data relating to two different characteristics, for example, color and thickness. If the sensors are of the same type, each can detect one data point of the characteristic, for example, a single color. The combined data from all the sensors allows for the assignment of a value to the characteristic, for example, the color of the relevant elementary area. It is then the processing of all the acquired data that allows for the assignment of a value to the characteristic for a particular elementary area.

[0037] In one particular embodiment, the sensor(s) may include a color detection sensor, and the value assigned to each elementary zone consists of a color. In this case, the threshold value may then consist of a predetermined color change. It should be noted that there may be one or more color changes before reaching the color change that constitutes the threshold value.

[0038] It is possible to create a map of the surface comprising a plurality of these elementary zones.

[0039] The elementary zones may be identical in shape and / or area. Alternatively, two elementary zones may differ from each other in shape and / or area.

[0040] A set of elementary zones is defined as comprising a plurality of elementary zones located within a predetermined radius around a given point on the surface of the workpiece. This predetermined radius corresponds to that of an abrasive pad on the abrasion machine. Thus, for each given point on an initial abrasion path, a set of elementary zones is defined around that point, the surface area of ​​which corresponds, for example, to that of the abrasive pad.

[0041] Thus, we can process the data acquired on each of the elementary zones and / or for each set of elementary zones, in order to determine and / or adjust the parameter(s) of the abrasion machine and / or the abrasion trajectory during the implementation of the abrasion. The acquisition stage

[0042] The acquisition in step (a), which may correspond to a measurement phase, can be performed by scanning at least part of the workpiece surface, for example, along a predefined path. The scanning path is, for example, composed of regularly spaced points, for example, 50 mm apart. Advantageously, the scanning is performed continuously along the entire path, for example, at a speed of approximately 500 mm / s, maximized according to the acquisition frequency and the blurring effect. The sensor(s) can trigger a measurement during the scan at each point encountered or independently of the points encountered, preferably at regular intervals. The spacing between two measurements naturally depends on the required resolution. This spacing can be less than twice the diameter of the abrasive tool.Alternatively or additionally, a measurement can be triggered by the sensor(s) at regular or irregular time and / or distance intervals over the entire area to be scanned.

[0043] Each measurement may or may not correspond to an elementary zone. When several measurements correspond to an elementary zone, at least one criterion, such as average or hierarchy, can be defined to assign a value to the elementary zone. When a measurement is taken for an elementary zone, the value assigned to that zone can directly correspond to the data recorded within the elementary zone. Alternatively, a measurement can be taken for several elementary zones simultaneously, for example, four elementary zones, as the sensor's field of view covers several elementary zones at the same time. A value can then be assigned to each elementary zone and / or to all the elementary zones for which the measurement was taken.

[0044] The acquisition can be performed in a dark environment, except perhaps for a lamp illuminating, at a given moment, the portion of the surface being acquired by the sensor(s). Such a lamp can be integrated into the sensor or the tool supporting the sensor. This ensures a homogeneous and constant brightness image across the entire surface of the room.

[0045] Alternatively, the acquisition is carried out in an environment with light.

[0046] In one particular embodiment, a color detection sensor coupled with a thickness sensor is used.

[0047] In one particular embodiment, no measurement of the coating thickness, especially of paint, is carried out. The processing stage

[0048] The processing in step (b), which may correspond to a calculation phase, can assign a value to each set of elementary zones. Each set of elementary zones has an area corresponding to an area of ​​the abrasive pad of the abrasion machine, particularly the sander, which will subsequently perform the abrasion, specifically the sanding, around a given point in the abrasion path. Indeed, the instantaneous abrasion area corresponds to the area of ​​the pad, and this area can encompass one or more elementary zones, corresponding to a set of elementary zones. Thus, the processing phase can assign a value to each set of elementary zones, preferably a value to each individual elementary zone, and then a value to each set of elementary zones determined from the values ​​of the individual elementary zones within the set of elementary zones.

[0049] Specifically, based on the data acquired by the sensor(s), a value can first be assigned to each elementary zone, and then a value can be assigned to each set of elementary zones for a given point on the abrasion path. This set value is a function of the value of each individual elementary zone within the set. The set value can, for example, correspond to a weighted average of the elementary zone values, and / or to a predominant value of an individual elementary zone within the set, and / or to another criterion. For example, if a value of an individual elementary zone within the set has reached the threshold value, then the threshold value can be assigned to that entire set. The step of determining and / or adjusting the abrasion parameter(s) and the abrasion trajectory

[0050] This step involves determining the parameters and abrasion path of the abrasive machine based on the values ​​assigned in the previous step. Specifically, the path to be followed by the abrasive pad during abrasion can be defined to avoid abrasion in the elementary zone(s) or set(s) of elementary zones that have reached a predetermined threshold value. A parameter such as the feed rate can be adjusted; this rate can be increased locally to reduce abrasion in a set of zones, for example, or along the entire path.

[0051] Initial abrasion parameters can be predefined.

[0052] The abrasion path may consist of several discrete segments or a single continuous path. Between any segments, the abrasion machine may cease abrasion and / or move away from the surface until the next segment, particularly in key areas to be excluded from abrasion.

[0053] The initial trajectory, for example predetermined, is advantageously continuous. The adjusted trajectory, particularly after a first, second, or third abrasion, can be discontinuous to exclude certain areas, yet still allows for the treatment of the entire surface of the part to be abrasived. A trajectory can be defined to treat only the areas to be treated. The initial trajectory can be designed to achieve the most uniform abrasion possible. The initial abrasion parameters may include a minimum feed rate.

[0054] All or part of the abrasion parameters can be adjusted for the entire trajectory, thus remaining constant along that trajectory. Alternatively, all or part of the abrasion parameters can be variable along the trajectory, particularly depending on the values ​​assigned to the elementary zones and / or sets of elementary zones encountered along the trajectory.

[0055] Parameters other than those mentioned above can be modified, such as changing the disc to a new one and / or to a different abrasion grain, in particular moving towards less abrasion as abrasions are made to reduce material removal.

[0056] Another parameter to adjust could be the abrasion force or the rotation speed.

[0057] When the abrasion machine has compliance, the compliance control force can be adjusted.

[0058] Another parameter can be modified: the diameter of the abrasive pad. For example, a pad with a different diameter surface can be used, becoming smaller as abrasions are performed to reduce the material removal area at any given time. Data processing will then be advantageously adapted to this new diameter, particularly for elementary zones forming a cluster around a given point. Acquisition tool and abrasion machine

[0059] The acquisition tool used to implement step (a) of acquisition may be separate from, or not from, the abrasion machine used to perform the abrasion step.

[0060] In particular, a single robot can carry both the data acquisition tool and the abrasion machine. The robot can include the processing and calculation tools for implementing steps (b) and (c). The robot can be capable of performing all the steps of the process.

[0061] The acquisition tool may include a sensor carried by a robotic arm, in particular a multi-axis one.

[0062] The abrasive machine may include an effector carrying an abrasive tool which in turn carries the abrasive pad, in particular a sanding tool, and optionally a compliance device. The abrasive pad is advantageously rotatable, with or without an eccentric mechanism, its rotation being driven by the abrasive tool or, preferably, freely rotating. The pad may be rigid or flexible, for example, with the addition of a foam layer. Brief description of the drawings

[0063] The invention will be better understood upon reading the following description of non-limiting embodiments thereof, and upon examination of the attached drawing, on which: [ Fig 1 ] represents, in block diagram form, the different stages of a process according to the invention, [ Fig 2] schematically represents, in perspective, an example of the implementation of the acquisition step of the process according to the invention, [ Fig 3 ] schematically represents an example of the result of the processing step of the process according to the invention for certain elementary areas, [ Fig 4 ] schematically represents an example of mapping that can be established during data processing for the parameterization step of the process according to the invention, [ Fig 5 ] schematically represents, in perspective, an example of the implementation of the abrasion step of the process according to the invention, [ Fig 6 ] represents an example of surface mapping of the part after implementation of the processing step, [ Fig 7 ] represents the mapping of the figure 6 in which certain areas have been excluded from further abrasion, [ Fig 8 ] represents the mapping of the figure 7in which at least part of the path of the abrasion machine has been traced, [ Fig 9 ] represents, schematically in perspective, the surface of a part to be abraded using the method according to the invention, [ Fig 10 ] represents a map of the surface area of ​​the room figure 9 before abrasion, [ Fig 11 ] represents the surface map of the room figure 9 after three repetitions of the steps of the process according to the invention, [ Fig 12 [ ] represents, schematically in perspective, the surface of the room of the figure 9 after three repetitions of the steps of the process according to the invention, and [ Fig 13 ] represents the surface map after data processing for the purpose of parameterizing the abrasion trajectory. Detailed description

[0064] There figure 1represents an example of a part abrasion process according to the invention comprising different steps. In a step (a), data relating to at least one characteristic of the part is acquired, with at least one sensor, on at least a part of the surface of the part, in at least two elementary zones defined on said acquisition surface.

[0065] In a second step (b), data relating to at least one characteristic of each elementary zone are processed in order to assign a value for that characteristic to at least one set of elementary zones. A subsequent step (c) consists of determining and / or adjusting at least one abrasion parameter of the abrasion machine and / or an abrasion trajectory based on the values ​​assigned to the set(s) of elementary zones.

[0066] Finally, in step (d), at least part of the surface is abraded using the abrasion machine with at least one abrasion parameter and abrasion path. An initial path and one or more abrasion parameters can be predetermined to obtain the most uniform abrasion possible. These can be implemented for the first abrasion pass. Preferably, these steps are repeated at least once or twice, as indicated by the upward arrow from step (d) to step (a), except possibly for step (d) if, after steps (b) and / or (c), further abrasion is deemed unnecessary because the part is sufficiently abraded.

[0067] Each of these steps of the process according to the invention will now be detailed.

[0068] We illustrated at the figure 2The acquisition step (a) of the method according to the invention. In this step, a robot R comprising a controller and equipped with a sensor C incorporating a lamp L, performs a zigzag scan of the surface S of a part 1, in order to acquire data relating to a characteristic of the surface S of the part. The beam F schematically represents the field of vision of the sensor C.

[0069] In the illustrated example, sensor C is a color detection sensor. The part consists of a final, bronze-colored metallic layer, a white intermediate layer, and a yellow initial layer, which is the only one visible before abrasion. The objective of the abrasion process is to obtain a smooth surface with the least amount of material possible without damaging the metallic layer.

[0070] The characteristic on which data is acquired and processed is the color of the surface of the part, in this example, in order to detect color changes that allow information to be deduced about the level of abrasion required.

[0071] Part 1 is roughly rectangular, being curved, as can be seen on the figure 2 In this example, it can be of any shape and size without going outside the scope of the invention, advantageously being devoid of relief on the surface to be treated.

[0072] During the acquisition phase, the entire surface S is scanned by the robot to enable data acquisition. The acquisition path is virtually formed by regularly spaced points to position the measurement triggers, including color, so that the entire part is captured.

[0073] The measurement taking by sensor C can be triggered at predetermined distance and / or time intervals, in this example every 50mm and / or every 10ms.

[0074] The scanning speed can be 500 mm.s -1 for example.

[0075] The result of some of these measures is illustrated on the figure 3 In the example considered, the sensor's measurement window is divided into two elementary zones. The sensor detects the final color, bronze, and the intermediate color, white, using filters called "OUT" applied to each elementary zone. The initial color, yellow, corresponds to the absence of the other two.

[0076] For each elementary zone, a process is performed during step (b), and a single color, corresponding to a value of the elementary zone, is determined and recorded by the controller according to a predefined hierarchy, for example, bronze above white above yellow. As visible on the figure 3 In the elementary zone ZE1, the presence of the color white B1 and the absence of the color bronze are detected. This allows the value white to be assigned to the elementary zone ZE1. Regarding the elementary zone ZE2, the color bronze Br and the color white Bl are detected, so the value bronze is assigned hierarchically to the elementary zone ZE2.

[0077] It is also possible, during the processing step (b), for assigning a value to a treatment area, to adjust detection thresholds in order to ignore a color for an elementary area when it is present but in too small a quantity to require adapting the abrasion, in particular sanding.

[0078] The processing can be at least partially carried out as the data is acquired.

[0079] Data including a position, in the reference frame used by the abrasion machine at the time of measurement, and a color are assigned to different elementary zones to form a map made up of 2 elementary zones, rectangular in this example, colored, as visible on the figure 4 . In this example, as seen on the map resulting from the acquisition processing, each elementary zone 2 is represented by a colored rectangle.

[0080] During the processing stage, for each point X, for example each point X of the initial abrasion path, a surface S1 is defined around this point X, corresponding to the surface covered by the abrasive plate of the abrasion machine. This surface S1 is visible on the figure 4 and corresponds to that which is covered by a set 3 of elementary zones 2. The set 3 of elementary zones 2 forming the surface S 1 has a circular surface in this example, and the elementary zones 2 forming it are rectangular, so that a process is carried out to determine the elementary zones 2 which are taken into account for the calculation or determination of the value to be assigned to the set 5.

[0081] In the example considered, the value of each set 3 of elementary zones is determined from at least one value of one of the elementary zones of that set.

[0082] For example, we can begin by comparing the values ​​of the elementary zones of set 3 with a threshold value, which could be the final bronze color. If one of the elementary zones has the threshold value, then we can assign this threshold value to set 3, so that the abrasion path will avoid the surface S1 of this set. If none of the values ​​of the elementary zones of set 3 reach the threshold value, then we can average the values ​​of the elementary zones of set 3 to find the value of set 3. The average can be weighted. Another criterion can be defined to determine the value of the set.

[0083] The values ​​of the elementary zones 2 and / or the sets 3 thus allow for the definition of an abrasion path in step (c), or its adjustment, for example, based on an initial or previous abrasion path, to avoid certain elementary zones or sets of zones. The values ​​of the elementary zones 2 and / or the sets 3 also allow for the definition or adjustment, again in step (c) of the process, of one or more parameters of the abrasion machine, such as the feed rate of the abrasive disc, its rotational speed, the force applied by the machine during surface abrasion, the abrasive disc change, the abrasive grit size of the abrasive disc, the diameter of the abrasive disc, or other abrasion parameters.

[0084] Once the parameter(s) and / or abrasion trajectory have been determined and / or adjusted, they can be applied to the abrasion machine to perform the abrasion, as illustrated in the figure 5. In this example, the machine enabling data acquisition and the abrasion machine performing the abrasion are combined into a single robot or robotic arm carrying on one side the acquisition tool, in particular the sensor, and on the other side the abrasive plate.

[0085] We illustrated on the figure 6 , an image of the mapped surface S, represented with the values ​​of elementary zones or sets of elementary zones assigned corresponding to colors, white, grey or dark.

[0086] On the figure 7 , the image of the surface S includes crossed-out areas or sets, corresponding to the areas or sets to be avoided during abrasion.

[0087] There figure 8This illustrates the abrasion path that is adjusted and plotted for the next abrasion, in order to avoid the aforementioned zones or areas, whose values, consisting of assigned colors, are visualized. Between each segment of the path, the abrasion machine must move away, relocate to an approach point, and then begin sanding the next area.

[0088] We have represented on the figure 9 A rectangular piece of uniform color, to be sanded, curved around at least one axis, visible in perspective. The associated mapping of the surface S with two square elementary zones (in this example), of uniform color before sanding, is shown on the Figure 10 .

[0089] After implementing all the steps of the process according to the invention, at least once, or even two or three times or more, with minimum feed rate parameters, for example, except in the half-turns where it is faster, it is observed that the color of the surface S of the part 1 is no longer uniform, as visible on the figure 12 The associated map is visible on the figure 11 shows areas 21 that are darker than others, areas 22 of intermediate color, and areas 23 of the original color. Dark spots on areas 23 are detected by the sensor, so there are areas to avoid during the next abrasion. It is on the basis of this surface condition illustrated on the figure 12 and mapped on the figure 11 that the images of figures 6 , 7 and 8corresponding, successively, to the implementation of step (c) of determining and / or adjusting the parameters and abrasion trajectory. In the intermediate color zones 22, the parameters can be modified to, for example, increase the feed rate in order to reduce sanding in these areas.

[0090] The parameters and trajectory for the next abrasion are determined and illustrated on the figure 13 After optimizing the trajectory reconstruction algorithm, several of these regions can be merged to reduce the number of sander inputs / outputs, thereby saving time and / or avoiding the quality degradation that can be caused by these inputs / outputs. Regions R1, R2, R3, R4, and R5 on this figure 13 correspond to distinct abrasion path segments.

[0091] The process is stopped, for example, when at least 80% of the surface S no longer needs to be sanded, having reached the threshold value, when, for example, 80% of the surface on the figure 13 is occupied by white areas or when areas to be abraded can no longer be reached, too small in relation to the tool or when the abrasion power of the abrasion machine can no longer be reduced.

[0092] It should be noted that in the example considered, the surface S of the part has a peripheral portion near at least one edge of the part at a predetermined distance from it, said peripheral portion not being treated by the abrasion machine.

Claims

1. Method for abrading a surface (S) of a workpiece (1) by means of an abrasion machine, comprising the following steps: (a) acquisition, with at least one sensor, on at least a part of the surface of the workpiece, of data relating to at least one characteristic of the workpiece in at least two basic zones (2) defined on said surface, (b) processing, for each basic zone (2), of the data relating to said at least one characteristic in order to assign, to at least one set (3) of basic zones (2), a value for this characteristic, a set of basic zones being defined as comprising a plurality of basic zones present within a predetermined radius around a given point of the surface of the workpiece, the predetermined radius corresponding to that of an abrasive table of the abrasion machine, wherein, for each given point of an initial abrasion trajectory, a set of basic zones is defined around this point, (c) determination and / or adjustment of at least one abrasion parameter of the abrasion machine and / or of an abrasion trajectory as a function of the values assigned for the set or sets (3) of basic zones (2), (d) abrasion of at least a part of the surface (S) with the abrasion machine with said at least one abrasion parameter and said abrasion trajectory.

2. Method according to Claim 1, comprising at least one repetition of the steps (a) to (c) and, preferably, at least one repetition of the step (d).

3. Method according to either one of the preceding claims, comprising several repetitions of the steps (a) to (d), preferably at least two repetitions, the last repetition not including the step (d).

4. Method according to any one of the preceding claims, wherein the abrasion machine moves relative to the workpiece during the abrasion step (d), the workpiece then being stationary.

5. Method according to any one of Claims 1 to 3, wherein the workpiece and the abrasion machine are mobile with respect to one another, during the abrasion step (d).

6. Method according to any one of Claims 1 to 3, wherein the workpiece is displaced relative to the abrasion machine during the abrasion step (d), the abrasion machine then being stationary.

7. Method according to any one of the preceding claims, wherein said at least one characteristic of the workpiece (1) is chosen from the group composed of a colour, a dimension, notably a thickness, a surface condition such as a brightness or a roughness, a radiation.

8. Method according to any one of the preceding claims, wherein said at least one sensor is chosen from the group composed of a sensor with or without contact based on optical, mechanical, magnetic, capacitive, acoustic, radiative and piezoelectric technologies, notably the group composed of cameras, colour sensors, thermocouples.

9. Method according to any one of the preceding claims, wherein said at least one abrasion parameter is chosen from among the following: speed of advance, speed of rotation or progress of the abrasive tool, effort applied by the abrasive tool on the surface of the workpiece, nature, form and / or size of the abrasive tool, angular orientation of the abrasive tool with respect to the local normal to the surface of the workpiece.

10. Method according to any one of the preceding claims, wherein the determination step (c) comprises a comparison, for each basic zone (2), of said value with a predetermined threshold value, in which method, when, by implementation of the comparison, the threshold value for said at least one characteristic of the workpiece (1) is reached in at least one basic zone (2) of a set (3) of basic zones, the abrasion trajectory is, preferably, determined so that there is no longer abrasion in the set (3) of basic zones concerned.

11. Method according to Claim 10, wherein, when, by implementation of the comparison, the threshold value for said at least one characteristic of the workpiece (1) is reached for at least a predefined percentage of the surface (S) or set or sets (3) of basic zones, notably at least 80% of the surface, the abrasion method is stopped.

12. Method according to any one of the preceding claims, the abrasion consisting of a buffing.

13. Method according to any one of the preceding claims, implementing two different sensors for the performance of the acquisition step (a).

14. Method according to any one of the preceding claims, wherein the sensor or sensors comprise a colour detection sensor, and the value assigned to each basic zone consists of a colour.