METHOD FOR MANUFACTURING A CUTTING TOOL WITH COMPLEXLY SHAPED LUBRICATION HOLES AND CUTTING TOOL WITH COMPLEXLY SHAPED LUBRICATION HOLES

Description

Technical field of the invention

[0001] The invention relates to the field of mechanical machining, and in particular to the field of machining tools and accessories. More specifically, the invention relates to a method for manufacturing a cutting tool with complex-shaped lubrication holes and a cutting tool with complex-shaped lubrication holes.

[0002] The cutting tool according to the invention is particularly intended for machining a part, in particular, a watch component. Technological background

[0003] In the field of machining, lubrication serves two purposes: firstly, to lubricate the interface between the cutting tool and the workpiece to reduce friction, and secondly, to cool this interface. Another objective of lubrication is to evacuate chips as the cutting operation progresses, i.e., during machining. Overall, lubrication enables efficient machining.

[0004] Some cutting tools have internal lubrication ports to increase the effects of lubrication during machining.

[0005] The state of the art is known of cutting tools comprising a body in which lubrication ports are machined, such as a through axial bore and channels extending radially between the bore and the active surface of the cutting tool.

[0006] The body is generally made of high-strength steels and a galvanic deposit of abrasive grains is made on the active surface.

[0007] These tools have the particular disadvantage of being complex and very expensive to produce. Indeed, the material from which they are made is hard, making their machining complex.

[0008] Furthermore, the hardness of high-strength steels limits the machining of these cutting tools, and in particular their lubrication holes, to the creation of relatively simple shapes.

[0009] For these reasons, the use of these cutting tools with lubrication holes is quite limited. For example, they are restricted to grinding applications, and only for parts made of materials with a hardness below a certain threshold.

[0010] US2018 / 304381 ​​and US4704055 documents describe cutting tools including lubrication ports. Summary of the invention

[0011] The invention solves the aforementioned drawbacks by proposing a solution enabling the production of a cutting tool whose body has lubrication holes of complex shapes.

[0012] To this end, the present invention relates to a method for manufacturing a cutting tool with complex-shaped lubrication holes, characterized in that it comprises the following steps: fabrication 320 of a polymer insert selected from plasticized polyvinyl butyral (PVB), plasticized cellulose acetate butyrate (CAB), and polybutyl methacrylate acrylic resin (PBMA), overmolding 310 of a cutting tool body with the polymer insert by injection molding, removal 320 of the polymer insert to form lubrication holes in the cutting tool body whose shape is complementary to that of a portion of the insert, sintering 330 of the cutting tool body 10, machining 340 of the cutting tool body on at least one part called the "active part", deposition of an abrasive coating 350 on a surface of the active part of the body of the cutting tool, said surface being called the "active surface".

[0013] Thanks to these characteristics, lubrication ports can have complex containing shapes.

[0014] Thus, new hard materials whose machining proved too complex, expensive, or even impossible with existing cutting tools can be machined with a cutting tool according to the present invention. Such hard materials include, for example, ceramics such as silicon nitride or zirconium oxide, or sapphire, alumina, or any hard metal.

[0015] Furthermore, the cutting tools according to the present invention can be used to perform milling operations on hard materials unlike the cutting tools of the prior art, since the lubrication holes can be made so as to optimize said lubrication.

[0016] In particular implementation modes, the insert removal step 320 is carried out by introducing the insert into a bath.

[0017] In specific implementation methods, the insert is produced using an additive manufacturing method.

[0018] According to another subject, this publication also relates to a cutting tool comprising a body with lubrication ports and a gripping portion for attachment to a tool holder chuck, and a cutting portion with a cutting surface. Helical grooves extend along the cutting surface, these grooves being connected to a central recess extending axially within the tool body by radial channels. This central recess extends between a lubricant inlet and a lubricant outlet.

[0019] In particular embodiments, the peripheral grooves extend helically between a first end opening onto a free end of the cutting tool and a second end opening near the gripping part of the cutting tool, that is to say closer to the gripping part than to the free end of the cutting tool.

[0020] In particular embodiments, the exhaust opening is configured to generate a venturi effect.

[0021] In particular embodiments, the active surface is substantially cylindrical in shape, comprising a peripheral surface and an end surface, the end surface defining the free end of the cutting tool body. The evacuation opening leads to a countersink, the cutting tool comprising end grooves extending radially on the end surface, from the countersink to the peripheral surface.

[0022] In particular embodiments, each radial channel extends lengthwise in a direction forming an acute angle with a longitudinal axis of the cutting tool body, the angle being oriented towards the free end of said cutting tool body.

[0023] Preferably, the radial channel extends in a direction forming an angle of 45 degrees, plus or minus 10 degrees, with the longitudinal axis of the cutting tool body.

[0024] This feature is advantageous because it allows for better distribution of lubricant around the body of the cutting tool.

[0025] In particular embodiments, each radial channel extending lengthwise has a helical shape.

[0026] This feature further improves the distribution of lubricant around the body of the cutting tool. Brief description of the figures

[0027] Other features and advantages of the invention will become apparent from the following detailed description, given by way of non-limiting example, with reference to the accompanying drawings in which: there figure 1 represents a flowchart of an example of implementing the manufacturing process for a cutting tool with complex-shaped lubrication holes according to the invention; the figure 2represents a perspective view of an example of the realization of an insert for the implementation of the process of the figure 1 ; there figure 3 represents a perspective view of an example of a cutting tool produced by implementing the process of the figure 1 ; there figure 4 represents a cross-sectional view of the cutting tool of the figure 3 to which the insert of the figure 2 . Detailed description of the invention

[0028] The present invention relates to a method of manufacturing a cutting tool 10 with complex-shaped lubrication orifices and a cutting tool 10 with complex-shaped lubrication orifices.

[0029] In the present description, a preferred application of the invention is described in which the cutting tool 10 is a machining tool, for example for grinding, drilling or milling, intended to be driven in rotation to machine a workpiece.

[0030] As shown in the flowchart of the figure 1 , the process according to the present invention includes a preliminary step of making 320 an insert 20 of polymer material.

[0031] Insert 20 is illustrated in a preferred example of implementation on the figure 2 , and is produced, for example by molding or by additive manufacturing, so as to present a negative shape of that of all or part of a body of the cutting tool 10.

[0032] In other words, the insert 20 has a shape that is complementary to that of the body of the cutting tool 10 which is intended to be manufactured by the process according to the invention.

[0033] In other words, the shape of the insert 20 is defined according to the desired shape of the cutting tool 10, given that said desired shape of the cutting tool 10 is obtained by subtracting the shape of the insert 20, as described in more detail below.

[0034] Insert 20 is made of polymer material, in particular plasticized polyvinyl butyral (known by the acronym "PVB"), plasticized cellulose acetate butyrate (known by the acronym "CAB"), or polybutyl methacrylate type acrylic resin (known by the acronym "PBMA").

[0035] Once the insert 20 is made, the body of the cutting tool 10 is overmolded with said insert 20 during an overmolding step 310 shown in the cross-sectional view of the figure 4 . More specifically, during this overmolding step 310, a mixture of powder, for example of Tungsten or other metals, and binder, for example polymer or metallic, previously prepared is injected into a mold in which the insert 20 is placed.

[0036] The powder and binder are advantageously chosen so as to form a tool body of hard metallic material, once the overmolding step 310 is completed.

[0037] Next, an elimination step 320 of the insert 20 is carried out, so as to form within the body of the cutting tool 10 lubrication orifices whose shape is complementary to that of a part of the insert 20.

[0038] During this removal step 320 of the insert 20, the assembly resulting from the overmolding step 310, i.e. the insert 20 and the cutting tool 10 cooperating with each other, is introduced into a bath, preferably of alcohol heated to 80°C.

[0039] The alcohol bath has the effect of dissolving the insert 20 so as to obtain only the cutting tool 10.

[0040] It should be noted that any method which can remove the material constituting the insert 20 without degrading that which constitutes the body of the cutting tool 10 can be implemented in the removal step 320 of the insert 20.

[0041] The manufacturing process according to the invention then includes a sintering step 330 of the body of the cutting tool 10, consisting of heating said body of the cutting tool 10 so as to form the cohesion of the material which constitutes it and to harden it.

[0042] The body of the cutting tool 10 is substantially cylindrical in shape and extends along a longitudinal axis. It comprises a first part 11 intended to be fixed to a tool holder chuck, connected to a second part 12 intended to be in contact with the workpiece. The first part 11 is herein referred to as the "gripping part" 11 and the second part 12 is referred to as the "active part" 12, said active part 12 having an external surface called the "active surface".

[0043] As shown by figure 3at least the active part 12 of the body of the cutting tool 10 advantageously includes lubrication orifices at the end of the removal step 320 of the insert 20, said orifices being of complementary shapes to those of portions of the insert 20 described in detail below, insofar as they are generated by the subtraction of said portions within the body of the cutting tool 10.

[0044] Thus, the lubrication orifices can have complex shapes, depending on the shapes taken by said portions of the insert 20.

[0045] It should be noted that the shape of insert 20, and in particular of said portions of insert 20, can be very complex when the latter is produced by additive manufacturing.

[0046] The active part 12 of the cutting tool body 10 is then machined during a machining step 340 of the cutting tool body 10.

[0047] During this step, the active part 12 is rectified so as to obtain a suitable surface condition for carrying out an abrasive coating deposition step 350, in which the active surface of the body of the cutting tool 10 is covered with a layer of abrasive for example by galvanic deposition.

[0048] The gripping part 11 can be machined during the machining step so as to be adapted to cooperate in fixing with a tool holder chuck.

[0049] Alternatively, the mold can be of a shape such that the gripping part 11 is molded during the overmolding step 310.

[0050] Preferably, the active surface has substantially a cylindrical shape of revolution comprising a peripheral surface 120 and an end surface 121, said end surface 121 defining the free end of the body of the cutting tool 10, as shown in the perspective view of the figure 3 .

[0051] Also, in the preferred embodiment shown in the figures, the insert 20 is shaped so that the cutting tool 10 has at least in its active part, a central recess 13 of circular cross-section extending axially inside the body of the tool, between a first opening (not shown in the figures) intended to receive lubricant, called the "inlet opening", located towards or in the gripping part 11 of the tool, and a second opening, called the "discharge opening" 130, intended to discharge the lubricant, opening onto the free end.

[0052] The discharge opening 130 is advantageously configured to generate a venturi effect. To this end, the central recess 13 has, at the level of the discharge opening 130, a radial lip 131 arranged to progressively reduce the cross-section of said central recess 13, as shown in the cross-sectional view of the figure 4 .

[0053] Advantageously, the discharge opening 130 opens onto the free end via a countersink 123, so that the cross-section of the central recess 13 increases progressively from the lip 131 to said free end. The technical effects of these features are described below.

[0054] Advantageously, the active portion has end grooves 122 extending radially over the end surface 121, from the countersink 123 to the peripheral surface 120. These end grooves 122 are regularly spaced angularly around the longitudinal axis of the cutting tool body 10, as shown in the figure 3 .

[0055] The end grooves 122 allow the lubricant flow expelled through the evacuation opening 130 to be distributed radially and homogeneously during the operation of the cutting tool 10.

[0056] Even more advantageously, as also shown by the figure 3The active part has peripheral grooves 124 extending helically over the peripheral surface 120, between a first end opening onto the free end of the cutting tool 10, i.e. on the end surface 121, and a second end opening near the gripping part 11 of the cutting tool 10. In other words, the second end of the peripheral grooves 124 is closer to the gripping part 11 than to the free end of the cutting tool 10.

[0057] These peripheral grooves 124 are regularly distributed angularly around the longitudinal axis of the cutting tool body 10.

[0058] As illustrated on the figures 3 and 4, the cutting tool 10 includes radial channels 132 connecting the central recess 13 to the peripheral grooves 124. More precisely, the cutting tool 10 has as many radial channels 132 as peripheral grooves 124, each radial channel 132 opening at the second end of a peripheral groove 124.

[0059] The term canal is defined in this text as a conduit that is radially closed and opens axially.

[0060] Thus, during the rotation of the cutting tool 10, during the operation of the cutting tool 10, part of the lubricant circulating in the central recess 13 is expelled through the radial channels 132, generating a flow of lubricant within each of the peripheral grooves 124.

[0061] These characteristics help to optimize the lubrication and cooling of the cutting tool 10 and the machined part, and therefore allow the machining of parts made of very hard materials, such as ceramics, silicon nitride, zirconium oxide, etc., or sapphire or other stones, alumina, or any hard metal.

[0062] The fact that the second end of the peripheral grooves 124 is closer to the gripping part 11 than to the free end of the cutting tool 10 ensures that the majority or all of the active surface is lubricated during the operation of the cutting tool 10.

[0063] Preferably, each radial channel 132 extends lengthwise in a direction forming an acute angle, for example of 45 degrees, with the longitudinal axis of the cutting tool body 10, said acute angle being oriented towards the free end of said cutting tool body 10.

[0064] In another example, the angle can be of a value between 35 and 55 degrees.

[0065] This feature is advantageous because it allows for better distribution of the lubricant around the body of the cutting tool 10.

[0066] Preferably, the direction in which each radial channel 132 extends lengthwise has a helical shape. In other words, each channel has a curved shape.

[0067] This feature further improves the distribution of lubricant around the body of the cutting tool 10, and thus further limits the temperature increase at the interface between the cutting tool 10 and the workpiece during machining, which leads to avoiding premature wear of the galvanic coating.

[0068] The lip 131 has the effect of increasing the expulsion pressure of the lubricant at the level of the discharge opening 130 and thus reducing or eliminating the loss of lubricant pressure within the central recess 13 generated by the radial channels 132. The countersink 123 has the effect of ensuring a homogeneous radial distribution of the expelled lubricant flow.

[0069] In the present example of an embodiment of the invention, and as illustrated in particular by the figure 2 , the insert 20 has a body of the insert 20 in the form of a blind hollow tube 21 of circular section intended to contain and form the body of the cutting tool 10.

[0070] The hollow tube 21 is connected to a central rod 22 intended to form the central recess 13, by radial rods 23 intended to form the radial channels 132.

[0071] The insert 20 also includes a projection 24 extending helically on an internal peripheral face of the hollow tube 21, from each radial rod 23 to an internal face of a bottom wall of said hollow tube 21. The projections 24 are intended to form the peripheral grooves 124.

[0072] The central rod 22 has, at the end by which it is linked to the bottom wall, a reduction in cross-section defining a radial groove 25 intended to form the lip 131.

[0073] The radial groove 25 is connected to the inner face of the bottom wall by a fillet 26 intended to form the countersink 123.

[0074] Finally, projections 27 extend radially on the inner face of the bottom wall, from the fillet 26 to the inner peripheral face 120 of the hollow tube 21. These projections 27 are intended to form the end grooves 122 during the implementation of the manufacturing process according to the invention.

[0075] It should be noted that the present invention can be applied to a cutting tool intended for drilling, milling or any other mechanical machining operations and to the method of this cutting tool.

Claims

1. A method for manufacturing a cutting tool (10) with lubrication orifices with complex shapes, comprising the following steps: - producing (300) an insert (20) made of plasticised polyvinyl butyral, of plasticised cellulose acetate butyrate, or of poly(butyl methacrylate) acrylic resin, - overmoulding (310) a body of the cutting tool (10) with the insert (20) by injection into a mould, - removing (320) the insert (20), so as to form, within the body of the cutting tool (10), lubrication orifices with a complementary shape to that of part of the insert (20), - sintering (330) the body of the cutting tool (10), - machining (340) the body of the cutting tool (10) on at least one part referred to as the "active part," - depositing an abrasive coating (350) on a surface of the active part of the body of the cutting tool (10). The method is characterised in that during the manufacture (300) of the insert, the insert (20) is made of plasticised polyvinyl butyral, of plasticised cellulose acetate butyrate, or of poly(butyl methacrylate) acrylic resin.

2. The manufacturing method according to claim 1, in which the step of removing (320) the insert (20) is carried out by putting the insert (20) in a bath.

3. The manufacturing method according to any of claims 1 to 2, in which the insert (20) is produced by an additive manufacturing method.