ABRASION METHOD

Abstract

A method for abrading a surface of a workpiece by means of an abrasion machine, including the following steps: (a) acquiring, with at least one sensor, on at least one portion of the surface of the workpiece, data in relation to at least one characteristic of the workpiece in at least two basic zones defined on the surface, processing, for each basic zone, the data in relation to the at least one characteristic in order to assign, to each basic zone and/or at least one group of basic zones, a value for this characteristic, determining and/or adjusting at least one abrasion parameter for the abrasion machine and/or an abrasion trajectory in accordance with the values attributed for the basic zones or group of basic zones, abrading at least a portion of the surface with the abrasion machine with the at least one abrasion parameter and the abrasion trajectory.

Claims

1. A method for abrading a surface of a workpiece by means of an abrasion machine, comprising the following steps: Step 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 defined on said surface, Step b: processing, for each basic zone, of the data relating to said at least one characteristic in order to assign, to each basic zone and/or to at least one set of basic zones a value for this characteristic, Step 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 basic zones or set or sets of basic zones, Step d: abrasion of at least a part of the surface with the abrasion machine with said at least one abrasion parameter and said abrasion trajectory.

2. The method as claimed in claim 1, further comprising at least one repetition of the steps to (a) to (c).

3. The method as claimed in claim 2, further comprising at least one repetition of the step (d).

4. The method as claimed in claim 1, further comprising several repetitions of the steps (a) to (d), the last repetition not including the step (d).

5. The method as claimed in claim 1, wherein the abrasion machine moves relative to the workpiece during the abrasion step (d), the workpiece then being stationary.

6. The method as claimed in claim 1, wherein the workpiece and the abrasion machine are mobile with respect to one another, during the abrasion step (d).

7. The method as claimed in claim 1, wherein the workpiece is displaced relative to the abrasion machine during the abrasion step the abrasion machine then being stationary.

8. The method as claimed in claim 1, wherein said at least one characteristic of the workpiece is chosen from the group composed of a color, a dimension, notably a thickness, a surface condition such as a brightness or a roughness, a radiation.

9. The method as claimed in claim 1, 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.

10. The method as claimed in claim 1, 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.

11. The method as claimed in claim 1, wherein the determination step c comprises a comparison, for each basic zone , of said value with a predetermined threshold value.

12. The method as claimed in claim 11, wherein, when, by implementation of the comparison, the threshold value for said at least one characteristic of the workpiece --14 is reached in at least one basic zone of a set of basic zones, the abrasion trajectory is determined so that there is no longer abrasion in the set of basic zones concerned.

13. The method as claimed in claim 11, wherein, when, by implementation of the comparison, the threshold value for said at least one characteristic of the workpiece is reached for at least a predefined percentage of the surface, of basic zones or set or sets of basic zones, the abrasion method is stopped.

14. The method as claimed in claim 1, wherein the abrasion consisting of a buffing.

15. The method as claimed in claim 1, implementing two different sensors for the performance of the acquisition step (a).

16. The method as claimed in claim 1, wherein the sensor or sensors comprise a color detection sensor, and the value assigned to each basic zone consists of a color.

17. The method as claimed in claim 1, wherein a set of basic zones comprises 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.

18. The method as claimed in claim 13, wherein the predefined percentage of the surface is 80%.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0067] The invention will be better understood on reading the following description of nonlimiting embodiments thereof, and on studying the attached drawing, in which:

[0068] FIG. 1 represents, in a block diagram, the different steps of a method according to the invention,

[0069] FIG. 2 schematically represents, in perspective, an example of implementation of the acquisition step of the method according to the invention,

[0070] FIG. 3 schematically represents an example of result of the processing step of the method according to the invention for certain basic zones,

[0071] FIG. 4 schematically represents an example of mapping that can be established in the processing of the data with a view to the parameterizing step of the method according to the invention,

[0072] FIG. 5 schematically represents, in perspective, an example of implementation of the abrasion step of the method according to the invention,

[0073] FIG. 6 represents an example of mapping of the surface of the workpiece after implementation of the processing step,

[0074] FIG. 7 represents the mapping of FIG. 6 in which certain zones have been excluded from a subsequent abrasion,

[0075] FIG. 8 represents the mapping of FIG. 7 in which at least a part of the trajectory of the abrasion machine has been plotted,

[0076] FIG. 9 represents, in perspective and schematically, the surface of a workpiece to be abraded using the method according to the invention,

[0077] FIG. 10 represents a mapping of the surface of the workpiece of FIG. 9 before abrasion,

[0078] FIG. 11 represents the mapping of the surface of the workpiece of FIG. 9 after three repetitions of the steps of the method according to the invention,

[0079] FIG. 12 represents, in perspective and schematically, the surface of the workpiece of FIG. 9 after three repetitions of the steps of the method according to the invention, and

[0080] FIG. 13 represents the mapping of the surface after processing of the data for the purposes of parameterizing the abrasion trajectory.

DETAILED DESCRIPTION

[0081] FIG. 1 represents an example of method for abrading a workpiece according to the invention comprising different steps. In a step (a), an acquisition is performed, with at least one sensor, over at least a part of the surface of the workpiece, to acquire data relating to at least one characteristic of the workpiece, in at least two basic zones defined on said acquisition surface.

[0082] In a second step (b), for each basic zone, data relating to said at least one characteristic are processed in order to assign, to each basic zone and/or to at least one set of basic zones, a value for that characteristic. A next step (c) consists in determining and/or adjusting at least one abrasion parameter of the abrasion machine and/or an abrasion trajectory as a function of the values assigned for the basic zones or set or sets of basic zones.

[0083] Finally, in the step (d), the abrasion of at least a part of the surface is performed with the abrasion machine with said at least one abrasion parameter and said abrasion trajectory. An initial trajectory and one or more abrasion parameters can be predetermined to obtain the most uniform possible abrasion. They can be implemented for the first abrasion pass. Preferably these steps are repeated at least one or two times, as indicated by the arrow going back up from the step (d) to the step (a), possibly excluding the step (d) if it is considered, after the step (b) and/or (c), that there is to be no more abrasion because the workpiece is sufficiently abraded.

[0084] Each of these steps of the method according to the invention will now be detailed.

[0085] FIG. 2 illustrates the acquisition step (a) of the method according to the invention. In this step, a robot R comprising a controller and provided with a sensor C incorporating a lamp L, performs a zigzag scanning of the surface S of a workpiece 1, in order to acquire data relating to a characteristic of the surface S of the workpiece. The beam F schematically represents the field of view of the sensor C.

[0086] In the example illustrated, the sensor C is a color detection sensor. The workpiece is composed of a final metal layer, bronze colored, a white intermediate layer and a yellow initial layer, which is the only one visible before the abrasion. The objective of the abrasion method is to obtain an even surface with the least possible material but without touching on the metal layer.

[0087] The characteristic on which data are acquired and processed is the color of the surface of the workpiece, in this example, in order to detect changes of color which make it possible to deduce information on the required abrasion level.

[0088] The workpiece 1 is substantially rectangular, being dished, as can be seen in FIG. 2, in this example. It can be of any form and dimensions without departing from the scope of the invention, advantageously having no relief on the surface to be treated.

[0089] During the acquisition step, all of the surface S is scanned by the robot to allow the acquisition of data. The acquisition trajectory is formed virtually by points evenly spaced apart in order to position the triggerings of the measurements, notably of color, in such a way that all of the workpiece is captured.

[0090] The taking of measurements by the sensor C can be triggered at predetermined distance and/or time intervals, in this example every 50 mm and/or every 10 ms.

[0091] The scanning speed can be 500 mm.s.sup.−1 for example.

[0092] The result of some of these measurements is illustrated in FIG. 3. In the example considered, the measurement window of the sensor is divided into two basic zones. The sensor makes it possible to detect the final bronze color and the intermediate white color with filters called “OUT” and applied to each basic zone. The initial color, yellow, corresponds to the absence of the other two.

[0093] For each basic zone in the step (b), a processing is performed and a single color, corresponding to a value of the basic zone, is determined, and stored, by the controller according to a predefined hierarchy, for example bronze higher than white higher than yellow. As can be seen in FIG. 3, the presence of the white color B1 and the absence of bronze color is detected on the basic zone ZE1. That makes it possible to assign the white value to the basic zone ZE1. With respect to the basic zone ZE2, the bronze color Br and the white color B1 are detected, such that, by hierarchy, the bronze value is assigned to the basic zone ZE2.

[0094] It is also possible, in the processing step (b), for the assignment of a value to a processing zone, to adjust detection thresholds in order to disregard a color for a basic zone when it is present but in too small a quantity for that to require adapting the abrasion, notably the buffing.

[0095] The processing can be at least partially performed as the acquisition of the data progresses.

[0096] Data comprising a position, in the reference frame used by the abrasion machine at the moment of the measurement, and a color are assigned to different basic zones so as to form a mapping composed of basic zones 2, rectangular in this example, and colored, as can be seen in FIG. 4. In this example, as can be seen in the mapping derived from the acquisition processing, each basic zone 2 is represented by a colored rectangle.

[0097] In the processing step, for each point X, for example each point X of the initial abrasion trajectory, a surface Si is determined around this point X corresponding to the surface covered by the abrasive table of the abrasion machine. This surface Si can be seen in FIG. 4 and corresponds to that which is covered by a set 3 of basic zones 2. The set 3 of basic zones 2 forming the surface Si has a circular surface in this example, and the basic zones 2 that form it are rectangular, such that a processing is performed to determine the basic zones 2 that are taken into account for the computation or the determination of the value to be assigned to the set 5.

[0098] In the example considered, the value of each set 3 of basic zones is determined from at least one value of one of the basic zones of that set.

[0099] For example, it is possible to begin by comparing the values of the basic zones of the set 3 with a threshold value which can be the bronze final color. If one of the basic zones comprises the threshold value, then, this threshold value can be assigned to the set 3, such that the abrasion trajectory will avoid the surface Si of that set. If none of the values of the basic zones of the set 3 has reached the threshold value, then an average can be taken of the values of the basic zones of the set 3 to find the value of the set 3. The average could be weighted. Another criterion can be defined to determine the value of the set.

[0100] The value of the basic zones 2 and/or of the sets 3 therefore makes it possible to define an abrasion trajectory in the step (c), or to adjust it, for example from an initial or preceding abrasion trajectory, for example to avoid certain basic zones or sets of zones. The value of the basic zones 2 and/or of the sets 3 also makes it possible to define or adjust, still in the step (c) of the method, one or more parameters of the abrasion machine such as the speed of advance of the abrasive table, its speed of rotation, the effort applied by the machine during the abrasion of the surface, the changing of abrasive disk of the abrasive table, the abrasion grain size of the abrasive disk, the diameter of the abrasive table or other abrasion parameter.

[0101] Once the parameter or parameters and/or the abrasion trajectory have been determined and/or adjusted, they can be applied to the abrasion machine, to perform the abrasion, as illustrated in FIG. 5. In this example, the machine allowing the acquisition of data and the abrasion machine performing the abrasion are combined in one and the same rotor or robotized arm bearing, on the one hand, the acquisition tool, notably the sensor, and, on the other hand, the abrasive table.

[0102] FIG. 6 illustrates an image of the mapped surface S, represented with the values of basic zones or of sets of basic zones that have been assigned corresponding to colors, whites, shaded or dark.

[0103] In FIG. 7, the image of the surface S comprises barred zones or sets, corresponding to the zones or sets to be avoided in the abrasion.

[0104] FIG. 8 illustrates the abrasion trajectory which is adjusted and plotted for the next abrasion, in order to avoid said zones or sets, for which the values assigned, consisting of colors, can be seen. Between each section of trajectory, the abrasion machine will have to disengage, move to a point of approach then begin buffing the next zone.

[0105] FIG. 9 shows a workpiece of uniform color, to be treated by buffing, of rectangular form, dished around at least one axis, and visible in perspective. The associated mapping of the surface S with basic zones 2, square in this example, of uniform color before buffing, is represented in FIG. 10.

[0106] After implementation of all of the steps of the method according to the invention, at least once, even twice or three times or more, with minimum speed of advance parameters, for example, except in the U-turns where it is faster, it can be seen that the color of the surface S of the workpiece 1 is no longer uniform, as visible in FIG. 12. The associated mapping visible in FIG. 11 shows zones 21 of a darker color than the others, zones 22 of intermediate color and zones 23 of initial color. Dark spots on the zones 23 are detected by the sensor, so there are therefore zones to be avoided in the next abrasion. It is on the basis of this surface condition illustrated in FIG. 12 and mapped in FIG. 11 that the images of FIGS. 6, 7 and 8 have been printed, corresponding, successively, to the implementation of the step (c) of determination and/or of adjustment of the abrasion parameters and trajectory. In the zones 22 of intermediate color, it will be possible to modify the parameters to accelerate, for example, the speed of advance in order to less buff these zones.

[0107] The parameters and the trajectory for the next abrasion are determined and illustrated in FIG. 13. After an optimization of the trajectory reconstruction algorithm, several of these regions can be merged to reduce the number of buffer inputs/outputs, in order to save time and/or avoid degrading the quality that can be brought about by the inputs/outputs. The regions R1, R2, R3, R4 and R5 in this FIG. 13 correspond to distinct abrasion trajectory sections.

[0108] The method is stopped, for example, when at least 80% of the surface S is no longer to be buffed, having reached the threshold value, when, for example, 80% of the surface in FIG. 13 is occupied by white zones or when it is no longer possible to reach zones to be abraded, that are too small with respect to the tool or when it is no longer possible to reduce the abrasion power of the abrasion machine.

[0109] It should be noted that, in the example considered, the surface S of the workpiece comprises a peripheral portion in proximity to at least one edge of the workpiece over a predetermined distance from the latter, said peripheral portion not being treated by the abrasion machine.