Prepolishing device and method for preparing ductile metal workpiece for polishing

Abstract

The invention relates primarily to a device for pre-polishing a workpiece, which comprises a working surface onto which the workpiece is placed. This working surface is made of a plurality of hollow sections (1) independent of each other and delimited by partitions (2). The flat upper walls (3) of these partitions form the active pre-polishing zone, which is intended to be in direct contact with the workpiece during the pre-polishing operation. The partitions (2) have a substantially constant height before use of the device. The device of the invention is essentially characterized in that the surface area of ​​the active pre-polishing zone represents between 45% and 55% of the working surface, and in that it is made of resin mixed with an abrasive diamond powder.

Description

TECHNICAL FIELD

[0001] The invention relates to a device for pre-polishing a ductile metallic material that has previously been cut. The invention also relates to a method for preparing a ductile metallic material for polishing, in which the pre-polishing operation is carried out with such a device. PRIOR ART AND DISADVANTAGES OF PRIOR ART

[0002] After cutting, a metallic material, especially a ductile metallic material, exhibits significant surface deformations of material that must be corrected before polishing operations take place.

[0003] Pre-polishing primarily involves removing surface material sufficiently to correct defects caused by cutting. However, it also aims to achieve optimal surface roughness to prepare the material for the polishing operation.

[0004] The pre-polishing of ductile metal materials is commonly carried out using a series of abrasive papers, progressing from the coarsest to the finest grit. These operations are time-consuming and require significant quantities of abrasive paper.

[0005] Publication WO0030806 describes a polishing device comprising alternating recessed sections delimited by partitions of constant height across the device's surface. This device requires the use of an abrasive suspension, with the recessed sections acting as reservoirs for the suspension. However, the device described in this publication is intended for polishing hard materials and not for pre-polishing ductile metallic materials. Using such a device on ductile materials would result in excessive degradation of the surface finish. OBJECTIVE OF THE INVENTION

[0006] The invention therefore relates to a pre-polishing device for ductile metallic materials that eliminates the need for abrasive paper and ensures both a sufficient material removal rate and a surface roughness suitable for the subsequent polishing operation. The aim is to reduce deformation caused by cutting while simultaneously removing sufficient material. DESCRIPTION OF THE INVENTION

[0007] To this end, the invention relates to a pre-polishing device for a ductile metal part to be prepared for polishing, which device comprises a working surface on which the part to be prepared is intended to be applied, and which is made of a plurality of hollow parts independent of each other and delimited by partitions whose flat upper walls form the active pre-polishing zone intended to be in direct contact with the part to be prepared during the pre-polishing operation, the partitions having a substantially constant height before use of the device, characterized in that the surface of the active pre-polishing zone represents between 45 and 55% of said working surface, in that it is based on resin mixed with an abrasive diamond powder.

[0008] The device may also include the following optional features, considered individually or in all possible technical combinations: The average size of the diamond particles in the abrasive powder is between 25 and 50 micrometers. The entire working surface is made of resin mixed with diamond abrasive powder, with an average particle size of 25 to 50 micrometers. The active pre-polishing zone represents 50% of the device's working surface. The average size of the diamond particles in the abrasive powder is between 30 and 40 micrometers. The mass percentage of diamond particles in the thickness of the active pre-polishing zone is between 4 and 11%. The mass percentage of diamond particles in the thickness of the active pre-polishing zone is between 8 and 10%.The ductile metal part has a yield strength between 250 and 800 MPa and an elongation at break between 8 and 50%. The hollow parts (1) and the partitions (2) are evenly distributed over the entire working surface. The resin is a polyester resin.

[0009] The invention also relates to a method of preparing a part for polishing which is essentially characterized in that after the cutting operation, a pre-polishing operation is carried out with the device as previously defined.

[0010] Advantageously, no pre-polishing operation with abrasive paper is carried out.

[0011] Preferably, the part to be polished is made of aluminum alloy. Preferably, it is a copper-aluminum alloy. The part to be polished can also be made of copper alloys such as brass (CuZn36), bronze (CuSn8), and cupronickel (CuNi14Al2).

[0012] Advantageously, the ductile metal part has a yield strength between 250 and 800 MPa and an elongation at break between 8 and 50%. PRESENTATION OF THE FIGURES

[0013] Other features and advantages of the invention will become clear from the description given below, which is by way of example and not limitation, with reference to the attached figures, among which:

[0014] [ Fig. 1 ] There figure 1 schematically represents a plan view of an example embodiment of the pre-polishing device of the invention in the form of a disc;

[0015] [ Fig. 2a ] There figure 2a schematically represents a detail of the figure 1 according to arrow A of the Figure 1; [Fig. 2b ] There Figure 2b is a micrograph of a detail of the figure 1 according to arrow A of the figure 1 .

[0016] [ Fig. 3 ] There figure 3schematically represents a cross-sectional view along arrow III-III of the figure 2 ;

[0017] [ Fig. 4 ] There figure 4 is a graph illustrating the rate of material removal as a function of pre-polishing conditions for prior art pre-polishings carried out with abrasive paper of different grain finenesses, for pre-polishings forming counter-examples carried out with pre-polishing discs of different kinds, and for pre-polishings according to the device of the invention;

[0018] [ Fig. 5 ] There figure 5 is a graph illustrating the surface roughness Ra for each pre-polishing condition shown on the figure 4 ;

[0019] [ Fig. 6 ] There figure 6 is a graph illustrating the surface roughness Rz for each pre-polishing condition shown on the figure 4 ;

[0020] [ Fig. 7 ] There figure 7is a graph illustrating the material removal rate at each cycle of the protocol as a function of the load-bearing rate of the pre-polishing device comprising diamond abrasive powder, of which the device of the invention;

[0021] [ Fig. 8] [Fig. 9 ] THE figures 8 and 9 are graphs illustrating the surface roughness Ra and Rz of the part respectively as a function of the bearing capacity of the pre-polishing device comprising diamond abrasive powder, of which the device of the invention;

[0022] [ Fig. 10 ] There Figure 10 is a graph illustrating the evolution of the pressure applied to the part as a function of the bearing capacity of the pre-polishing device comprising diamond abrasive powder, of which the device of the invention;

[0023] [ Fig. 11 ] There figure 11is a graph illustrating the material removal rate at each cycle of the protocol as a function of the size of the diamond particles in the diamond powder mixed with the resin of the device of the invention;

[0024] [ Fig. 12 ] ] Fig. 13 ] THE Figures 12 And 13 are graphs illustrating the surface roughness Ra and Rz of the part respectively as a function of the size of the diamond particles in the diamond powder mixed with the resin of the device of the invention;

[0025] [ Fig. 14 ] There figure 14 is a graph illustrating the material removal rate at each cycle of the protocol as a function of the concentration of diamond particles in the thickness of the working surface of the device of the invention;

[0026] [ Fig. 15] [Fig. 16 ] THE Figures 15 and 16are graphs illustrating the surface roughness Ra and Rz of the part respectively as a function of the concentration of diamond particles in the thickness of the working surface of the device of the invention. DETAILED DESCRIPTION OF THE INVENTION

[0027] It is first clarified that in the figures, the same references designate the same elements regardless of the figure in which they appear and regardless of the form in which those elements are represented. Similarly, if elements are not specifically referenced in one of the figures, their references can easily be found by referring to another figure.

[0028] It is also specified that the figures essentially represent one embodiment of the object of the invention, but that there may be other embodiments which meet the definition of the invention.

[0029] The pre-polishing device of the invention is described structurally with reference to the Figures 1 to 3 .

[0030] There figure 1 shows an example of an embodiment of the pre-polishing device according to the invention which is in the form of a disc whose substantially flat surface, called the working surface, intended to be applied against the ductile metal part to be pre-polished, comprises a plurality of hollow parts 1 which are delimited from each other by partitions 2.

[0031] As shown more precisely by figure 2 , the hollow parts 1 here have substantially the shape of a square, the hollow parts, as well as the partitions, being preferably regularly distributed over the surface of the disc according to the invention.

[0032] To perform pre-polishing, the disc is rotated and the parts to be polished are also rotated at a lower speed, and applied to the surface of the disc with a certain pressure.

[0033] Furthermore, the partitions 2 are defined by a flat upper wall 3 and two side walls 4 and 5.

[0034] It is the upper walls 3 of the partitions 2 which, in cooperation with water distributed in a continuous stream or water sprayed on the disc allowing the removal of metallic debris produced by the pre-polishing operation, form the active zone of the disc for pre-polishing.

[0035] These partitions 2 have a height h which is preferably uniform across the entire surface of the disc, in order to ensure even pre-polishing of the parts to be polished. This depth h also defines the depth of each recessed section 1.

[0036] This height h is advantageously between approximately 0.05 and 15 millimeters and, preferably, between 0.05 and 10 millimeters.

[0037] Furthermore, it is advantageous for the thickness of the partitions 2, or the dimension z of the upper face 3 of the partitions, to be between 0.5 and 15 millimeters, preferably between 1 and 2 millimeters, to contribute to the efficiency of material removal when using the disc. The recessed areas, for their part, have a generally rectangular shape with a length x between 1 and 5 millimeters, preferably between 2 and 4 millimeters, and a width y less than the length x and also between 1 and 5 millimeters, preferably between 2 and 4 millimeters.

[0038] Furthermore, it is preferable that the draft angle α, between the upper wall 3 of the partition 2 and a lateral wall 4 or 5, be less than 90. This is due to the fact that the disk is advantageously obtained by molding.

[0039] Furthermore, it is preferable that this angle not be less than 75, so that the active area of ​​the disk, consisting of all the upper walls of the partitions 2, is not significantly altered when the disk undergoes wear, after prolonged use.

[0040] The invention is of course not limited to the shape of the hollow parts 1 and the partitions 2 which is illustrated in the figures.

[0041] The recessed parts 1 can have any geometric shape, including polygonal and for example rectangular or hexagonal, or a rounded shape, such as a round or oval shape.

[0042] The surface of the pre-polishing device according to the invention can also correspond to the negative or positive relief of a fabric, in particular of the satin or taffeta type.

[0043] The ranges of values ​​previously given for wall thickness, tank depth and partition draft angle are applicable to all forms of hollow parts and partitions, based on the average tank depth, the smallest partition thickness and the largest dimension of the hollow parts.

[0044] The invention is also not limited to a pre-polishing device in the form of a disc with a flat surface.

[0045] Thus, the disc can have a concave or convex surface. Furthermore, the device can also be cylindrical, with the pre-polishing working surface being either the external or internal surface of the cylinder.

[0046] In general, the device according to the invention is a surface of revolution whose axis of revolution is the axis of rotation of the device on the pre-polishing machine on which it is used.

[0047] For pre-polishing, it is advantageous that the recessed parts and partitions be distributed regularly on any curve defining a plane perpendicular to the axis of revolution of the device and whose points are all equidistant from the axis of revolution.

[0048] The pre-polishing disc is advantageously obtained by molding a synthetic resin mixed with a diamond abrasive powder, the specific characteristics of which will be described later. In addition to the diamond particles, one or more additional metallic powders may be incorporated.

[0049] The mold has the shape of the desired counterpart, in order to obtain the required recesses and partitions. Thus, practically speaking, a mold will have domes. The mold may consist of a negative reproduction of a grid whose voids represent the partitions, and to which a plate is attached to block them.

[0050] According to the invention, the pre-polishing device has specific characteristics attached to the active pre-polishing zone.

[0051] First, this active pre-polishing zone, formed by the flat upper walls 3 of the partitions 2, represents between 45 and 55%, preferably 50%, of the working surface, which is defined as comprising the recessed parts 1 and the partitions 2. Furthermore, this active pre-polishing zone is made of resin mixed with a single abrasive diamond powder. Advantageously, the average size of the diamond particles in the abrasive powder is between 25 and 50 micrometers. For manufacturing convenience, a pre-polishing device in which the entire working surface (recessed parts 1 and upper walls 2 of the partitions) exhibits these properties is preferred. However, within the scope of the invention, what is essential is that the active pre-polishing zone in direct contact with the material to be pre-polished exhibits these properties.

[0052] The pre-polishing device is advantageously applied to ductile metallic materials which deform easily under the pressure exerted by conventional discs during the pre-polishing operation, such as aluminum alloys or copper alloys.

[0053] The ductile character of metallic materials suitable for use with the device of the invention is defined by an elastic limit between 250 and 800 MPa and an elongation at break between 8 and 50%.

[0054] The results presented below demonstrate the unexpected effects on material removal rate and surface roughness obtained with the pre-polishing device of the invention.

[0055] All tests were carried out under the following same operating conditions.

[0056] The polishing machine used is marketed under the name Masterlam 3.0 by the company LAMPLAN.

[0057] Six samples are positioned on a central pressure sample holder with six sample receiving cavities.

[0058] The six samples have on their underside a surface made of EN AW-2017A copper aluminum alloy with the formula AlCu4MgSi commonly used in the automotive and aerospace industries and which has been previously cut.

[0059] The EN AW-2017A alloy is heat-treated under T3 conditions to achieve a minimum yield strength of 250 MPa and an elongation at break of at least 10% as specified by EN 754-2. The EN AW-2017A alloy thus treated exhibits a yield strength between 416 and 449 MPa and an elongation at break between 10 and 11.5%.

[0060] The chemical composition of the EN AW-2017A alloy comprises, by weight: 0.2% ≤ Si ≤ 0.8%, Fe ≤ 0.7%, 3.5% ≤ Cu ≤ 4.5%, 0.4% ≤ Mn ≤ 1%, 0.4% ≤ Mg ≤ 1%, Cr ≤ 0.1%, Zn ≤ 0.25%, Ti+Zr ≤ 0.25%, other ≤ 0.05%, the remainder being aluminium.

[0061] In parallel, the pre-polishing disc to be tested is installed on a rotating platform after being dressed for about 30 seconds using an abrasive dressing stone to remove the layer of resin that covers the diamond particles.

[0062] The sample holder and the pre-polishing disc are brought close together, and the following operating parameters are applied: Sample holder rotation speed: 125 rpm clockwise. Tray rotation speed: 300 rpm clockwise. Central force / Central pressure applied to the sample holder against the tray: 120 Newtons. Lubricant: water.

[0063] The lubricant used is water, the functions of which are to remove abrasion debris, to cool and to lubricate the treated surface.

[0064] For each pre-polishing disc tested, the samples are subjected to a preparatory cycle as well as the following four cycles: Preparatory cycle: P80 abrasive paper is mounted on the pre-polishing machine's platter, and the previously mentioned operating conditions are applied for two minutes. This step is not a step of the invention but rather a preparation of the sample similar to that obtained after cutting. Cycle 1: The pre-polishing disc forming the counterexample or example according to the invention is mounted on the pre-polishing machine's platter, and the previously mentioned operating conditions are applied for two minutes. Cycle 2: The pre-polishing disc forming the counterexample or example according to the invention is left on the pre-polishing machine's platter, and the previously mentioned operating conditions are applied for two minutes.Cycle 3: The pre-polishing disc forming a counter-example or example according to the invention is left on the pre-polishing machine's platter, and the previously mentioned operating conditions are applied for six minutes. Cycle 4: The pre-polishing disc forming a counter-example or example according to the invention is left on the pre-polishing machine's platter, and the previously mentioned operating conditions are applied for twenty minutes.

[0065] For tests involving abrasive papers, the same cycles are applied, except that each cycle is performed with a new abrasive paper and each cycle lasts 2 minutes.

[0066] Between each cycle, the material removal rate measurements in grams per minute taken by the machine are recorded, and the surface roughness Ra and Rz are measured.

[0067] Roughness Ra, expressed in micrometers (µm), measures the average of the peaks and troughs of the metallic surface, including the deviation from the mean line. The greater the deviations, the rougher the surface; conversely, a low Ra value indicates a smoother surface. Roughness Rz, also expressed in micrometers (µm), measures the difference between the highest peak and the lowest trough along a five-line sampling length. It indicates the maximum profile height. A lower Rz value also indicates a smoother surface.

[0068] THE figures 4 to 6The results obtained in terms of material removal rate and Ra and Rz roughness for five prior art abrasive papers, eleven pre-polishing discs of varying characteristics serving as counterexamples, and two pre-polishing discs according to the invention are presented. The characteristics of the tested abrasive paper or pre-polishing discs are shown in Table 1 below. All tests were performed on the EN AW-2017A alloy defined above. Table 1 Characterization of the tested abrasive paper or pre-polishing disc Prior art 1 P120 abrasive paper Previous art 2 P400 abrasive paper Previous art 3 P600 abrasive paper Previous art 4 P800 abrasive paper Previous art 5 P1200 abrasive paper Counter-example 1 F120 silicon carbide-mixed polyester resin disc (average particle size of 106 µm) Counter-example 2 F240 polyester resin disc mixed with silicon carbide Counter-example 3 F600 polyester resin disc mixed with silicon carbide Counter-example 4 F1200 polyester resin disc mixed with silicon carbide Counter-example 5 F120 Aluminum Oxide Mixed Polyester Resin Disc Counter-example 6 Polyester resin disc mixed with aluminum oxide F240 Counter-example 7 F600 Aluminum Oxide Mixed Polyester Resin Disc Counter-example 8 Polyester resin disc mixed with diamond powder - load-bearing capacity of 15% - average particle size: 151 µm Counter-example 9 Polyester resin disc mixed with diamond powder - 50% load-bearing capacity - particle sizes: 10-20 µm Counter-example 10 Polyester resin disc mixed with diamond powder - load-bearing capacity of 6% - particle sizes: 10-20 µm Counter-example 11 Polyester resin disc mixed with diamond powder - 50% load-bearing capacity - particle sizes: 125-149 µm Example 1 according to the invention Polyester resin disc mixed with diamond powder - 50% load-bearing capacity - particle size: 35-37 µm - diamond mass concentration: 6% Example 2 according to the invention Polyester resin disc mixed with diamond powder - 50% load-bearing capacity - particle size: 35-37 µm - diamond mass concentration: 9%

[0069] The goal in polishing, and more specifically pre-polishing, is to achieve both a sufficient material removal rate to simplify the subsequent polishing operation and the lowest possible surface roughness. The aim is to substantially reduce deformations resulting from cutting while removing sufficient material. It is defined that the material removal rate should preferably be greater than 0.9 g / min and that the surface roughness Ra should be less than 0.4 µm, preferably less than 0.3 µm, so that the metal surface is adequately prepared for polishing.

[0070] In this sense, we observe that the polyester resin discs mixed with silicon carbide (counter-examples 1 to 4) give material removal rates that are too low, equal to or less than 0.7 g / min.

[0071] It is also noted that although the disc of resin mixed with F120 aluminum oxide (counter-example 5) gives good results in terms of material removal, the surface roughness is too high (Ra of 0.55 µm).

[0072] Conversely, F240 and F600 aluminum oxide mixed resin discs (counter-examples 6 and 7) are insufficient in terms of material removal rate.

[0073] Regarding the counterexamples relating to a disc of resin mixed with diamond powder, it is observed that a bearing capacity of 15% (counterexample 8) results in an excessively high surface roughness (Ra of 0.813 µm). The same is true for a diamond particle size of 125-149 µm and a bearing capacity of 50% (counterexample 11).

[0074] Conversely, for a lift rate of 50% or 6% and a diamond particle size of 10-20 µm (counter-examples 10 and 11), the material removal rate is too low (0.3575 and 0.378 g / min respectively).

[0075] It is thus observed that only discs of resin mixed with diamond powder with a bearing capacity of 50% and a diamond particle size of 35-37 µm (examples 1 and 2) make it possible to obtain both a good material removal rate (1.166 and 1.046 g / min) and a low surface roughness with an Ra less than 0.4 µm (0.273 µm and 0.237 µm respectively).

[0076] This result is all the more surprising given that it could have been expected that discs containing silicon carbide or aluminum oxide would yield better results. It is also surprising to observe the disparities in results for a disc loaded with diamond powder depending on the size of the diamond particles. Other results related to diamond particle size are presented later with reference to figures 11 to 13 .

[0077] The unexpected effect of the efficiency of a lift-to-drag ratio between 45 and 55%, and more particularly 50%, is also demonstrated by the results presented on the figures 7 to 9 .

[0078] In these figures, four different bearing capacities were tested for discs made of unsaturated polyester resin containing only diamond particles as abrasives, with diamond particle sizes ranging from 35 to 37 micrometers. The tested bearing capacities were 6.1% (reference 9), 15% (reference 10), 25% (reference 11), and 50% (reference 12), respectively. The results are shown after pre-polishing cycles 1, 2, and 3, as previously defined.

[0079] It is observed that while the material removal rate is naturally lowest at a load factor of 50%, it is still above 0.9 g / min, which is sufficient to prepare the surface for polishing. However, the surface roughness obtained at a load factor of 50% is surprising, as it does not follow the trend in roughness at load factors of 6.1%, 15%, and 25%. In addition to the fact that roughness predictably decreases, at least for the first and second cycles, with increasing load factor, the surface roughness values ​​Ra and Rz for load factors of 15% and 25% are similar after each cycle, whereas the surface roughness values ​​Ra and Rz for a load factor of 50% are significantly lower.

[0080] A load-bearing capacity of 50% thus allows us to benefit from the best ratio of material removal rate to surface roughness, even though this advantageous surface roughness could not be deduced from the surface roughnesses obtained for load-bearing capacities of 15% and 25%.

[0081] The load-bearing rate between 45 and 55%, and more particularly 50%, has also been highlighted as enabling optimal surface pressure during pre-polishing by the pre-polishing machine.

[0082] With reference to the Figure 10 , the pressure was evaluated according to the bearing rate of the disc for three central forces applied on the sample holder against the plate during pre-polishing of 120 Newton (reference 6), 180 Newton (reference 7) and 240 Newton (reference 8) respectively.

[0083] The pressure responds to the following formula: the load-bearing capacity of the support corresponding to the surface of the active pre-polishing zone, i.e. the surface constituted by the upper face 3 of the partitions.

[0084] The material removal rate is directly related to the applied pressure. It has been observed that beyond a 55% bearing capacity, the pressure difference between two different central pressures decreases. Therefore, there is no particular advantage to exceeding a 55% bearing capacity, given that the material removal rate will be reduced and the size of the hollow sections will become too small to adequately evacuate the water that removes the produced metal debris.

[0085] All these results show that a bearing capacity between 45 and 55% is the best possible compromise between the material removal rate and roughness, even though it could not be assumed that the roughness obtained would be so good.

[0086] The unexpected effect of the efficiency of a diamond particle size between 25 and 50 micrometers, and more particularly between 35 and 37 micrometers, is demonstrated in light of the results presented on the figures 11 to 13In these figures, three diamond particle sizes are tested on polyester resin pre-polishing discs containing only diamond particles as abrasives with a 50% bearing capacity. The diamond particle sizes tested are 125–149 µm (reference 13), 35–37 µm (reference 14), and 14–20 µm (reference 15), respectively. The results are shown after pre-polishing cycles 1, 2, and 3, as previously defined.

[0087] It is observed that while the material removal rate and roughness decrease with decreasing diamond particle size, the disc containing diamond particles with a size between 35-37µm presents unpredictable results.

[0088] Indeed, the results relating to roughness show a certain proportionality with respect to the sizes of the diamonds tested. This is not the case for the material removal rate, since the results obtained are higher for a diamond particle size of 35-37µm than could be predicted by considering only the ratio between the sizes of the particles tested.

[0089] In other words, it is for a diamond size of 35-37µm that the best combined results in material removal rate and surface roughness are obtained.

[0090] We evaluate in reference to figures 14 to 16The influence of diamond mass concentration in a polyester resin pre-polishing disc containing only diamond particles as abrasives, with a bearing capacity of 50% and a diamond particle size between 35 and 37 µm, was investigated. The diamond particle mass concentrations tested were 3% (reference 16), 6% (reference 17), 9% (reference 18), and 12% (reference 19), respectively. The results are presented after pre-polishing cycles 1, 2, and 3, as previously defined.

[0091] The results show that as the diamond particle concentration increases, the material removal rate decreases and the surface finish (roughness) improves. However, it is also observed that beyond a mass concentration of 12%, the roughness results, particularly after cycles 1 and 2, are equivalent to those obtained with mass concentrations of 6% and 9%, and especially 9%.

[0092] From an economic point of view, combined with the effectiveness of pre-polishing, it is advantageous to choose a mass concentration between 4 and 11%, and more particularly a mass concentration between 8 and 10% as illustrated by the referenced results 18.

[0093] The invention further relates to a method for preparing a ductile metal part for pre-polishing without the use of abrasive paper. The method comprises, after cutting, a single pre-polishing step using a device as previously described. The part is then ready for polishing using conventional methods.

Claims

1. A device for pre-polishing a ductile metal part to be prepared for polishing, which device comprises a working surface on which the part to be prepared is intended to be applied, and which is made of a plurality of hollow parts (1) independent of each other and delimited by partitions (2) whose flat upper walls (3) form the active pre-polishing zone intended to be in direct contact with the part to be prepared during the pre-polishing operation, the partitions (2) having a substantially constant height before use of the device, characterized in that The surface area of ​​the active pre-polishing zone represents between 45 and 55% of said working surface, and in that It is made from resin mixed with an abrasive diamond powder.

2. Device according to claim 1, characterized in that The average size of the diamond particles in the abrasive powder is between 25 and 50 micrometers.

3. Device according to any one of claims 1 and 2, characterized in that The entire working surface is made of resin mixed with an abrasive diamond powder with an average size of diamond particles in the abrasive powder which is between 25 and 50 micrometers.

4. Device according to any one of the preceding claims, characterized in that The surface area of ​​the active pre-polishing zone represents 50% of the working surface of the device.

5. Device according to any one of the preceding claims, characterized in that The average size of the diamond particles in the abrasive powder is between 30 and 40 micrometers.

6. Device according to the preceding claim, characterized in that The mass percentage of diamond particles in the thickness of the active pre-polishing zone is between 4 and 11%.

7. Device according to the preceding claim, characterized in thatThe mass percentage of diamond particles in the thickness of the active pre-polishing zone is between 8 and 10%.

8. Device according to any one of the preceding claims, characterized in that The ductile metal part has a yield strength between 250 and 800 MPa and an elongation at break between 8 and 50%.

9. Device according to any one of the preceding claims, characterized in that The recessed parts (1) and the partitions (2) are distributed evenly over the entire work surface.

10. Device according to any one of the preceding claims, characterized in that The resin is a polyester resin.

11. Method for preparing a workpiece for polishing, characterized in that after the cutting operation, a pre-polishing operation is carried out with the device according to any one of claims 1 to 10.

12. Method according to claim 11, characterized in that No pre-polishing operation with abrasive paper is carried out.

13. A method according to any one of claims 11 and 12, characterized in that The part to be polished is made of aluminum alloy.

14. A method according to any one of claims 11 to 13, characterized in that The ductile metal part has a yield strength between 250 and 800 MPa and an elongation at break between 8 and 50%.

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