Method for manufacturing a tool module and tool module

Abstract

Method for producing a tool module having a clamping section (82) from a blank, wherein the clamping section (82) is designed as a hollow shaft cone (HSK) (10), characterized in that at least a partial surface section (AF) of the blank is hardened at least on the clamping section (10) by means of a melting laser beam hardening process.

Description

[0001] The invention relates to a method for manufacturing a tool module comprising a clamping section from a blank, wherein the clamping section is designed as a hollow shank taper (HSK), in particular according to the standard DIN 69893 (May 2003). The invention further relates to a corresponding tool module. STATE OF THE ART

[0002] In this text, a tool module is understood to be, in particular, a tool in which a machining section or tool head, the clamping section, and, if applicable, a shank section form an integral or at least permanently connected unit. Furthermore, a workpiece module can also be designed as a tool carrier or tool holder to which an actual tool can be detachably or permanently attached.

[0003] In recent years, the so-called hollow taper shank interface (HSK interface) has become increasingly prevalent in tool clamping. This interface is standardized in DIN 69893 (May 2003) and is characterized by the fact that the tool module connected to a tool holder via the interface is positioned with exceptional radial precision, and that particularly high torques can be transmitted between the holder and the connected tool module. The design of the standardized hollow taper shank, in conjunction with the clamping elements engaging within the HSK shank across the entire conical surface, and the additional flat contact surface provided on a collar of the hollow taper shank, creates an extremely high frictional engagement.In most cases - with the exception of design type E according to DIN 69893-5 - two T-nuts at the shank end of a tool holder engage in drive grooves of the hollow shank cone and thus ensure a positive locking and defined radial positioning.

[0004] Compared to the conventional "steep taper" interface, the HSK interface offers particular advantages in terms of accuracy, rigidity, and suitability for very high speeds. A further advantage is the ability to perform rapid tool changes. However, due to the specific design features of the HSK interface, meticulous attention must be paid during manufacturing to ensure that the load-bearing capacity is not exceeded across the entire operating range of the interface. This is further complicated by the fact that, for example, when the hollow taper shank is formed directly on a tool (such as a tool with an eroded or ground insert seat, or a tool with brazed cutting edges (PCD, CBN, carbide (HM))), only special materials, such as heat-treated or case-hardened steels, can be used, which can significantly increase the manufacturing effort.

[0005] Of particular importance is the fact that the stress on the hollow shank cone, especially in the transition area to the tool shank, varies from tool to tool due to the different shank lengths. Depending on the tool used, the bending moment caused by the cutting force varies, so that the shear force resistance of the hollow shank cone varies considerably depending on the overhang of the cutting edges. The torsional fatigue strength of the interface design is also a crucial criterion for the success of the interface.

[0006] In the actual machining process, the interface is subjected to dynamic excitation, which reduces the transmissible and tolerable torsional moment over a long period. Therefore, when manufacturing components for the HSK interface, it is crucial to produce the functionally engaged surfaces with high dimensional accuracy, ensuring that no unacceptable deviations in shape occur over the component's service life. For this reason, DIN 69893 specifies, among other things, where surface hardening must be applied.

[0007] In the conventional manufacturing process, a cylindrical blank made of tool steel is first machined to form the hollow shaft taper with a predetermined interference fit. This semi-finished product is then removed from the machining process and sent – ​​often externally – for hardening. The workpieces, hardened in the HSK area, are then reintroduced into the machining process and machined to their final dimensions.

[0008] Aside from the fact that this process is time-consuming and costly, the following has been shown: It occasionally happens that hollow shank cones break during tool use, and in many cases the cause of the material failure cannot be determined. One problem is that a wide variety of materials must be used for the tools and thus also for the hollow shank cones, and that the distribution of the microstructure across the cross-section of the component, which is reintroduced into the machining process after hardening, cannot be "visually" determined. Consequently, subsequent finishing processes, such as grinding the functional surfaces of the hollow shank cone, can subject the material to thermal stress, which can be detrimental in terms of fatigue strength and crack susceptibility.

[0009] Furthermore, a variety of turning tools are known from the prior art, comprising a base body with a clamping section and a machining section or tool head. The clamping section is designed for insertion into a special clamping device, such as an HSK clamping device, and is generally located on the tool shank at an end region of the turning tool axially opposite the tool head. In many turning tools, the metallic material of the tool head is hardened to meet the high mechanical demands of machining. Such turning tools can be drilling, reaming, milling, or polishing tools. Typically, such turning tools have at least one chipping or cutting edge in the tool head, through which material is removed from a workpiece in a machining operation.Especially in high-performance turning tools, such as HPC (High Performance Cutting) or HSC (High Speed ​​Cutting) turning tools, one or more coolant channels are provided in the turning tool to introduce a cooling or lubricating fluid into the area of ​​the tool head in order to cool the tool head and the encircled chip edge and to remove material debris from the chip area. More recently, minimum quantity lubrication (MQL) has been used for this purpose.

[0010] To increase the service life and functional properties of a turning tool, the tool head is typically hardened to enhance its mechanical resistance. This is achieved by modifying or transforming the metal structure of the tool head through a heat treatment followed by rapid cooling. Usually, the entire tool head is hardened to achieve the desired resistance.

[0011] Furthermore, DE 10 2008 062 920 A1 and DE 10 2014 103 906 A1 are known from the prior art.

[0012] The invention is based on the objective of providing a method for manufacturing a tool module with improved quality and service life and such a tool module. REVELATION OF THE INVENTION

[0013] This problem is solved by a manufacturing process and a tooling module according to the independent claims. Advantageous embodiments of the invention are the subject of the dependent claims.

[0014] The invention relates to a method for manufacturing a tool module comprising a clamping section from a blank, wherein the clamping section is designed as a hollow shank cone (HSK), in particular according to DIN 69893. According to the invention, at least a partial surface section of the blank is hardened at least on the clamping section by means of a melting laser beam hardening process.

[0015] A melting laser beam hardening process allows for the selective hardening of wear-prone surface areas of the tool module with precise contour control and precise control of the extent of the hardened areas relative to the surrounding surface.

[0016] Tool material is hardened or post-hardened, particularly to increase the durability of the tool module. The rapid heat input via laser, combined with virtually simultaneous self-quenching, enables short hardening times and thus high production speeds in the manufacture of tool modules, at least in the clamping section. By applying melting laser hardening processes, properties can be imparted to the surface sections to be hardened that are not achievable, or at least not with the same quality and / or precision, using other, purely heating-based hardening processes such as laser or induction hardening, which do not involve melting.

[0017] According to an advantageous embodiment of the method, at least one partial surface section of at least one machining section of the tool module, in particular a cutting section and / or a cooling channel boundary section and / or a cooling channel outlet section, is hardened by means of a melting laser beam hardening process. The advantage here is that a laser already present in the production line for hardening the clamping section can also be used for surface hardening a machining section of the tool module. Other sections or areas of the tool module, e.g., a shank section or outlet areas of coolant channels provided inside the tool module, can also be hardened accordingly by means of a melting laser beam hardening process. The various surface sections can, but do not have to, be processed with the same melting laser beam hardening process.This allows cooling channels to be designed with a larger cross-section due to reduced wall thickness, in order to increase cooling performance and extend service life.

[0018] Advantageously, the melting laser beam hardening process comprises a laser cladding process in which the hardening of the surface section is achieved by surface deposition through local melting of the surface section and simultaneous application of a filler material or a filler material mixture, in particular a hard material. A ceramic filler material, which serves as wear protection, can be applied as a filler material.

[0019] Furthermore, the melting laser beam hardening process can include a laser alloying process in which the hardening of the surface section is achieved by locally melting the surface section and simultaneously introducing a hardening filler material or filler material mixture into the resulting melt to form an alloy consisting of the blank material and the filler material or filler material mixture. This also allows for the production of particularly hard and wear-resistant surface sections.

[0020] According to an advantageous embodiment, the melting laser beam hardening process can comprise a laser remelting process in which the hardening of the surface section is achieved by locally heating the surface section above its melting temperature. This also advantageously hardens the microstructure of the surface section.

[0021] According to a further advantageous embodiment of the process, the hardening step using a melting laser beam hardening process is combined with a further heat treatment step in order to adapt selected areas of the tool module to the structural stress expected there.

[0022] It has proven advantageous if the blank is made of a steel alloy, and at least one hardened surface section is formed by selective surface austenitization of the surface material.

[0023] Advantageously, for partial surface hardening of the tool module, it is possible to move the module relative to a selective hardening device to harden, and in particular austenitize, the partial surface area. It is proposed that, for surface hardening of the partial surface sections, either the tool module is moved against a laser beam source, or that the hardening device is moved relative to the tool module. Generally, it will be advantageous to move the tool module, which has low mass and free movement, relative to a stationary hardening device to selectively harden, and in particular austenitize, the partial surface sections.

[0024] The invention further relates to a tool module with a clamping section designed as a hollow shank cone (HSK), in particular according to the standard DIN 69893, wherein at least a partial surface section of the tool module is hardened at least on the clamping section by means of a melting laser beam hardening process, in particular according to one of the aforementioned processes.

[0025] The tool module can, for example, be a turning tool for machining workpieces.

[0026] The at least one hardened surface section can, for example, be provided on a drive groove of the clamping section. DRAWINGS

[0027] Further advantages become apparent from the accompanying drawing description. The drawings illustrate exemplary embodiments of the invention. The drawing, the description, and the claims contain numerous features in combination. A person skilled in the art will expediently consider the features individually and combine them into meaningful further combinations.

[0028] They show: Fig. 1 a partially sectioned side view of a hollow shaft cone according to DIN 69893-1; Fig. 2 a sectional view of another hollow shaft cone according to DIN 69893; Fig. 3 the detail “III” in Fig. 2; Fig. 4 a schematic partial sectional view of a hollow shaft cone after the hardening process; Fig. 5 a perspective view of a hollow shaft cone after the hardening process; Fig. 6 schematically a tool head of an embodiment of a tool module according to the invention formed as a rotary tool with hardening areas; and Fig. 7. In perspective, an embodiment of a tool module formed as a drilling tool with partially hardened surface areas.

[0029] In Fig. Figure 1 shows a scale view of a hollow shank taper 10 designated HSK-A100 according to DIN 69893-1 (May 2003). The hollow shank taper 10 is shown here, for example, on a rotary-driven cutting tool with an eroded or ground insert seat with a clamping thread, on a tool with a milled insert seat, or on a tool with brazed cutting edges, which can be made of PCD, CBN, or carbide (HM) inserts. However, it should be emphasized at this point that the hollow shank taper can also be used on tool holders without cutting edges or on so-called "base mounts" such as flanges, reducers, or extensions. Finally, it is also possible to use such hollow shank tapers on insert tools with other shanks.

[0030] DIN 69882-1 specifies the general requirements for inserting toolholders with hollow taper shanks according to DIN 69893-1, Form A and Form C, into the work spindle of machine tools, such as machining centers, lathes, drilling machines, milling machines, and grinding machines. Unless otherwise specified in the relevant product standard, the tensile strength of the steel used is at least 800 N / mm². 2 Furthermore, the hardness of the hardened surface sections is specified as 56 + 4 HRC and 590 + 80 HV 30, respectively.

[0031] The special feature of the hollow shaft cone 10 of this design is that various functional surfaces, which are located in the Fig. 1, Fig. 2, Fig. 3, Fig. 4 to Fig. 5, designated A, B, C, D, E and F, are subject to different stresses: A fixed axial planar contact with the counterpart of the HSK interface is established at the radial end faces A. In the area of ​​the outer cone B, radial surface contact exists, whereby a radial elastic preload of the cone section occurs due to the interference between the cone and the receptacle. In the area of ​​the respective drive groove 16 ( Fig. 1, Fig. 2 and Fig. 5) In section C provided for, T-nuts not shown engage with a fit to further increase the maximum transmissible torque.

[0032] According to DIN 69893-1, at least 75% of the clamping force acting on the internal wedge surface D via internal collets (not shown) must act on the flat contact surface A. Finally, a certain surface quality is also required in area E, i.e., in the area of ​​a gripper groove, to minimize wear caused by tool changing systems.

[0033] All functional surfaces A to F must be hardened to prevent excessive wear over the tool's service life.

[0034] However, the functional areas A to F have a fundamentally different stress profile, so it is desirable to design the hardened surfaces in such a way that the cross-section present there is optimally able to withstand the stresses.

[0035] Stress maxima under the influence of rotational speed typically form in the area of ​​a transition radius 12 between the clamping angle and the inner diameter of the shank, as well as in the groove root radius 14 of the deep drive groove 16. The limiting rotational speed of the HSK interface is thus determined, among other things, by the length of the supporting mounting taper, the radial interference between the shank and the mount, the dimensions of the mount, and the specific chip removal system used. Accordingly, it is crucial in each case that the manufacturing process of the hollow shank taper 10 is optimally adapted to the intended application.

[0036] According to the invention, this is achieved by surface-hardening at least selected surface sections of the functional surfaces A to F using a melting laser hardening process. In melting laser hardening processes, a high-power laser, primarily a diode laser or fiber laser, but also CO2 and Nd:YAG lasers, serves as the heat source.

[0037] A prime example of a melting laser hardening process is laser cladding. The hardening of the surface section is achieved through surface deposition by locally melting the surface area and simultaneously depositing a filler material, particularly a hard material. The filler material can be supplied in powder form, e.g., as metal powder, or via a welding wire or strip. In powder laser cladding, the laser typically heats the workpiece in a defocused manner, melting it locally. Simultaneously, an inert gas mixed with fine metal powder is supplied. The metal / gas mixture can be delivered to the working area via trailing or coaxial nozzles. At the heated area, the metal powder melts and bonds with the metal of the hollow shaft cone. In addition to metal powder, ceramic powder materials, especially hard materials, can also be used. Laser cladding with wire or...The tape method works analogously to the process with powder, but with wire or tape as an additional material.

[0038] By correctly setting the parameters laser power, feed rate, powder mass flow rate (or alternatively, wire or strip feed rate), and focus position, a material deposit is created on the workpiece. This deposit can be formed into a surface with the desired surface hardness through multiple passes – side by side or one on top of the other. The bond to the base material of the tool module blank can be influenced, for example, by the formation of an intermediate layer via these parameters. Subsequent post-processing steps such as milling, turning, or grinding are necessary to produce the final shape of the tool module blank. Typically, the tool module blank is manufactured undersized, at least in the areas of the surface sections to be hardened. The hard coating is then applied oversized, and finally, the tool module is machined to its final dimensions.

[0039] A second example of a melting laser hardening process is laser alloying, in which the hardening of the surface section is achieved by locally melting the surface section and simultaneously introducing a hardening filler material into the resulting melt to form an alloy consisting of the blank material and the filler material. While in laser cladding the property profile of the processed surface is determined solely by the filler material used, in laser alloying the base material into which the filler material is alloyed plays a crucial role. In the laser alloying process, the laser beam is moved continuously over the tool module blank, locally melting the base material. A stable melt pool is formed, into which the filler material is selectively blown using a powder nozzle.The powder particles dissolve completely in the superheated melt bath, leading to a change in its chemical composition. Homogenization of the melt bath is achieved through strong convection currents, the flow behavior of which can be specifically influenced by surfactants. A typical characteristic of the laser alloying process is the very fine microstructure produced by the rapid solidification. Final machining to precise dimensions is also possible.

[0040] A third example of a melting laser hardening process is laser remelting, in which the hardening of the surface section is achieved by locally heating it above its melting temperature. The material of the tool module blank is locally melted at the surface under the influence of the laser beam. Similar to laser hardening, rapid heat dissipation into the workpiece interior occurs through "self-quenching," or the surface layer is quenched using a spray nozzle filled with a cooling medium. As a result of grain refinement, the surface structure is altered, leading to modified properties. Laser remelting, like laser hardening, is a surface hardening process. The key difference between the two processes lies in the fact that, unlike laser hardening, the base material in laser remelting is heated above its melting temperature.

[0041] Upon heating, the initially present cementite-ferrite crystal mixture transforms into a homogeneous solid solution, austenite. The carbon that was bound in the cementite (Fe3C) is atomically dissolved in the austenite. The subsequent cooling must therefore occur so rapidly that the carbon remains dissolved even after the crystal transformation, thus suppressing the transformation of the austenite into pearlite and ferrite, which results in the hardening structure of martensite.

[0042] The hardening processes according to the invention can be integrated into the entire manufacturing process of the tool module. In other words, the material parameters as well as the geometric parameters are entered into a process control system. A corresponding hardening device for carrying out the hardening process, for example in the form of a robot, therefore has this system-inherent data either from the outset or via data transfer. Accordingly, for each workpiece currently being processed, exact values ​​for the microstructure to be achieved are defined at selected positions of the tool module. Consequently, the laser can be controlled with regard to movement and power so that the target microstructure is achieved at every desired location.

[0043] In this way, it is possible, for example, to determine the hardening depth TH in the area of ​​the functional surfaces of the hollow shaft cone, as in Fig. Figure 4 schematically indicates the control. The boundary between the hardened structure and the heat-unaffected zone is marked by a dashed line. It can be seen that this hardening depth TH can vary considerably across the surface of the hollow shaft cone. While it can be relatively large in the area of ​​the gripper groove E, it is only in the tenths of a millimeter range in the area of ​​the outer cone B. It can be larger in the area of ​​the drive slots 16 for the engagement of the drive T-nuts (not shown), as well as in the area of ​​the cone surface D, while it can disappear completely in the area of ​​the transition radius 12.

[0044] In other words, the one with the double arrow Q in Fig. 4. The area of ​​the material structure unaffected by the hardening process can be controlled according to the individual stress profiles and load conditions expected in the later use of the tool module, in order to fully exploit the ductility of the material where necessary, so that the service life of the tool or tool module can be increased reproducibly.

[0045] In Fig. Figure 6 shows a tool head 112 of a tool module designed as a turning tool 110. The tool head 112 comprises two main cutting edges 114a and 114b, which are connected by a cross-cutting edge 116. A chip groove 120 extends between the two main cutting edges 114a and 114b, separating the flanks of the cutting edges 114a and 114b. The chip groove 120 is bounded by secondary cutting edges of the cutting phase 122a and 122b. Outlet areas of a coolant channel 124a (shown with dashed lines) and 124b are recessed in the groove surfaces, branching off from a main coolant channel that extends along the axis of the turning tool 110.In the concentric surface area around the outlets 124a, 124b, the chamfered surface is designed as a hardening area 126a and 126b with a locally hardened surface to prevent the relatively thin material wall opposite the coolant channel 124a, 124b from breaking through under high thermal and mechanical stress. The hardening areas 126a, 126b can be produced, in particular, by one of the melting laser beam hardening processes described above according to the invention, but can also be selectively heated and subsequently quenched by another laser hardening process to achieve increased hardness compared to the rest of the tool head 112.

[0046] In Fig. Figure 7 shows a further embodiment of a tool module configured as a drilling tool 80 in perspective. The drilling tool 80 comprises a schematically depicted shank as a clamping section 82 and a tool head 84, which has several cutting edges 96 and a helical chamfer 92 as a boundary of a clamping groove 98. The clamping section 82 of the drilling tool can be fitted with a hollow shank taper 10 ( Fig. 1, Fig. 2, Fig. 3, Fig. 4 to Fig. 5), in particular with a tool carrier or holder having a hollow shank cone, detachably or permanently connected, or having a hollow shank cone as an integral component. The cutting edges 96 are arranged on an end face 94 of the tool head 84. Two coolant channels 88a, 88b have contoured outlets on the end face 94. The outlets are bounded by webs 86 against the circumferential surface of the tool head 84. Elliptical hardening areas 90 are arranged concentrically around the outlets of the coolant channels 88a, 88b. Further hardening areas, shown as dashed lines, are provided along the chip groove 98, which delimit the relatively thin material wall between the coolant channel 88a, 88b and the chip groove surface 98.The hardening areas 90 and / or the further hardening areas can in particular be produced by one of the melting laser beam hardening processes described above according to the invention, but can also be selectively heated and subsequently quenched by another laser hardening process in order to form an increased hardness compared to the rest of the drilling tool 80.

[0047] The turning tool 110 and / or the drilling tool 80 can be fitted with a hollow shank taper 10 ( Fig. 1, Fig. 2, Fig. 3, Fig. 4 to Fig. 5), in particular, being detachably or permanently connected to a tool carrier or holder having a hollow shank cone, or having a hollow shank cone as an integral component.

[0048] It is obvious that the inventive design of the manufacturing process minimizes process errors. Because the hardening process can be integrated into the production line, the parameters regarding geometry and material structure are already available in the system at the beginning of the hardening process. Transmission errors of such data are thus eliminated. Process reliability during hardening is noticeably increased in this way, with the additional advantage that, using suitable measuring systems, the hardening process can even be fine-tuned to the actual dimensions of the tool module to be hardened.

[0049] Naturally, deviations from the embodiment are possible without abandoning the basic concept of the invention. For example, the hardening process can be combined with a further heat treatment step by controlling the microstructure and additionally influencing selected areas.

[0050] The invention thus provides a method for manufacturing a tool module, such as a tool with brazed cutting edges (PCD, CBN or carbide), in which a cylindrical blank is fitted at one axial end with a hollow shank taper (HSK), in particular according to DIN 69893. Selected functional areas are subjected to a hardening process.

[0051] Particularly when machining aluminum alloys with a higher silicon content, high wear of a turning or drilling tool can occur, potentially leading to undesirable perforation of the coolant channel wall. To prevent such perforation, the areas of the tool head covering the coolant channel can be hardened using a selective surface hardening process, especially one of the melting laser beam hardening processes according to the invention. The advantage of a selective hardening process is that specific areas can be hardened, thus flexibly protecting partial surface areas of the tool head against mechanical wear. Laser beam hardening, electron beam hardening, ion beam hardening, or inductive hardening processes can all be used as hardening methods. Reference symbol list 10 hollow shaft cones 12 Transition radius 14 Groove base radius 16 drive groove A to F Functional surface, surface section Q Double Arrow TH hardening depth 110 Rotary tool 112 Tool head 114a, 114b Main cutting edge 116 Cross-cutting edge 118 Front surface 120 span groove 122a, 122b Secondary cutting edge 124a, 124b Coolant channel 126a, 126b Hardening area 80 Drilling tools 82 Shaft, clamping section 84 Tool head 86 Bridge 88a, 88b Coolant channel with contour outlet 90a, 90b hardening range 92nd phase 94 Front surface 96 cutting edge 98 Spannut

Claims

[1] Method for manufacturing a tool module having a clamping section (82) from a blank, wherein the clamping section (82) is designed as a hollow shank cone (HSK) (10), characterized by , that at least on the clamping section (10) at least a partial surface section (AF) of the blank is hardened by means of a melting laser beam hardening process. [2] Method according to claim 1, characterized by , that furthermore, at least one partial surface section (AF) is hardened by means of a melting laser beam hardening process on at least one cutting section and / or one cooling channel boundary section and / or one cooling channel outlet section. [3] Method according to claim 1 or 2, characterized by, that the melting laser beam hardening process includes a laser cladding process in which the hardening of the surface section (AF) is carried out by surface deposition by locally melting the surface section and simultaneously applying a hard material. [4] Method according to any one of the preceding claims, characterized by , that the melting laser beam hardening process includes a laser alloying process in which the hardening of the surface section (AF) is carried out by locally melting the surface section and simultaneously introducing a hardening filler material into the resulting melt to form an alloy consisting of the material of the blank and the filler material. [5] Method according to any one of the preceding claims, characterized by, that the melting laser beam hardening process includes a laser remelting process in which the hardening of the surface section (AF) is carried out by locally heating the surface section above its melting temperature. [6] Method according to any one of the preceding claims, characterized by , that the hardening process step using a melting laser beam hardening process is combined with a further non-melting heat treatment step. [7] Method according to any one of the preceding claims, characterized by , that the blank is made of a steel alloy, and that at least one hardened surface section (AF) is formed by selective surface austenitization of the surface material. [8] Tool module with a clamping section designed as a hollow shank taper (HSK) (10), characterized by, that at least on the clamping section at least a partial surface section (A to F) of the tool module (10) is hardened by means of a melting laser beam hardening process according to a method according to at least one of the preceding claims. [9] Tool module according to claim 8, characterized by , that the tool module is a turning tool (110) for machining workpieces. [10] Tool module according to claim 8 or 9, characterized by , that at least one hardened surface section (AF) is provided on a drive groove (16) of the clamping section.

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