Pressing tool and method for forming a cutting insert blank having a through hole

Abstract

The invention relates to a pressing tool and a method for forming a cutting insert blank (5) having a through hole (6) of length (L) by compressing powder. The pressing tool comprises a cavity (4) operable to define a compression space, a first core rod (7) and a second core rod (8) for forming the through hole (6) together, each of the first core rod and the second core rod having a contact surface (9) at the front end. Both core rods (7, 8) are arranged along a core axis (10) in a manner movable in both directions. When both core rods (7, 8) are in respective pressing positions, their respective contact surfaces (9) contact each other in the compression space, and when both the first core rod (7) and the second core rod (8) are in respective release positions, their respective contact surfaces (9) are separated by a distance greater than the length (L). The first core rod (7) comprises a base body (11) and a piston (12), the base body comprising a forwardly facing abutment surface (17), the piston having a shaft (13) and a front portion in the form of a head (14). The contact surface (9) of the first mandrel (7) is the front end surface of the head (14). The head (14) includes a rearwardly facing abutment surface (17). The piston (12) is movable to a plurality of extended positions and to a retracted position in which the abutment surface (17) of the head (14) abuts against the abutment surface (17) of the substrate (11). The piston (12) is in the retracted position when both the first mandrel (7) and the second mandrel (8) are in their respective pressing positions.

Description

Technical Field

[0001] The present invention relates to a pressing tool for forming a cutting insert blank having a through hole having a length (L) by compressing powder. The present invention also relates to a method of forming a cutting insert blank having a through hole having a length (L) using a pressing tool. Background Art

[0002] WO2004 / 0414463 discloses a uniaxial press for forming a green part from compressed metallurgical powder, wherein an opening is formed in the green part by placing the metallurgical powder around an elliptical core rod. The core rod comprises a first segment and a second segment, each segment having complementary ends. The segments are arranged on opposite sides of the press and are movable along its longitudinal axis. During operation, the segments are pushed together so that their ends meet and a continuous core rod is formed. Then, powder is filled into the die cavity and the green part is formed. Finally, the segments are retracted and the finished green part is ejected. The problem with this known press is that at the position where the ends of the segments contact each other, the segments leave a burr ring in the opening of the green part. In the finished cutting blade, these remaining burr rings may form sharp edges that can damage the fastening screws. Summary of the invention

[0003] The object of the present invention is to at least partially eliminate the above-mentioned problems. According to the invention, this object is achieved by a pressing tool according to the invention and a method according to the invention for forming a cutting insert blank.

[0004] The pressing tool of the present invention for forming a cutting insert blank having a through hole having a length (L) by pressing powder comprises:

[0005] - a cavity operable to define a compression space corresponding to the dimensions of the blank,

[0006] - a first mandrel and a second mandrel for forming together the through hole, the first mandrel and the second mandrel each having a longitudinal extension from a front end to a rear end and a contact surface at the front end,

[0007] in,

[0008] - the first mandrel and the second mandrel are both arranged longitudinally along the mandrel axis with their respective front ends facing each other,

[0009] - both the first mandrel and the second mandrel are arranged in a movable manner in both directions of the mandrel axis, wherein both the first mandrel and the second mandrel are movable to respective pressing positions and to respective release positions, wherein

[0010] - when both the first mandrel and the second mandrel are in their respective pressing positions, their respective contact surfaces are in contact with each other within the compression space, and wherein,

[0011] - when both the first mandrel and the second mandrel are in their respective release positions, their respective contact surfaces are separated by a distance greater than the length (L),

[0012] - the first mandrel comprises a longitudinally extending rearward portion in the form of a base body, the longitudinally extending rearward portion comprising a forwardly facing abutment surface at a front end, the piston having a rear portion in the form of a longitudinally extending shaft (13) and a front portion in the form of a radially protruding head, wherein

[0013] - The contact surface is the front surface of the head,

[0014] - the head comprises at the rear end a rearwardly facing abutment surface, and wherein

[0015] - the shaft (13) is arranged in the base body in a longitudinally movable manner along the core axis, so that the piston can be moved into a plurality of extended positions and into a retracted position in which the abutment surface of the head abuts against the abutment surface of the base body,

[0016] And wherein the piston is in the retracted position when both the first mandrel and the second mandrel are in their respective pressing positions.

[0017] A method of the present invention for forming a cutting insert blank having a through hole having a length (L) using a pressing tool, wherein the pressing tool comprises:

[0018] - cavity,

[0019] - a first mandrel and a second mandrel, each of which has a longitudinal extension from a front end to a rear end, and a contact surface at the front end, wherein the first mandrel comprises:

[0020] - a longitudinally extending rearward portion in the form of a base body comprising a forwardly facing abutment surface at a front end,

[0021] a piston having a rear portion in the form of a longitudinally extending shaft and a front portion in the form of a radially protruding head, wherein the contact surface is a front end surface of the head and the head comprises a rearwardly facing abutment surface at the rear end,

[0022] The method comprises the following steps:

[0023] - arranging both the first mandrel and the second mandrel longitudinally along the mandrel axis with their respective front ends facing each other,

[0024] - the piston and its shaft are arranged longitudinally in the base body along the core axis,

[0025] - filling the cavity with a predetermined amount of powder,

[0026] - moving the piston along the core axis into a retracted position in which the abutment surface of the head abuts against the abutment surface of the base body,

[0027] - moving the first mandrel and the second mandrel along the mandrel axis into respective pressing positions, wherein their respective contact surfaces come into contact with each other within the cavity in a compression space corresponding to the dimensions of the blank,

[0028] - operating the cavity to compress the powder in the compression space to form a cutting insert blank,

[0029] - moving the second contact rod backwards along the core axis and moving the piston forwards to the first extended position,

[0030] - moving the first mandrel and the second mandrel along the mandrel axis to respective release positions wherein their respective contact surfaces are separated by a distance greater than the length (L), and

[0031] - operating the cavity to decompress the compressed space, and

[0032] - Removing the cutting insert blank.

[0033] During the formation of the cutting blade blank, both the first mandrel and the second mandrel are placed in their respective pressing positions, wherein the contact surfaces are in contact with each other, and the adjacent surfaces are in contact with each other. At the first interface of the contact surfaces and the second interface of the adjacent surfaces, corresponding annular burr rings may be formed in the through hole of the cutting blade blank. Since the first mandrel includes a piston movable to an extended position, these burr rings can be removed, or at least significantly reduced, before the cutting blade blank is removed from the pressing tool. This can be achieved, for example, by first retracting the second mandrel from its pressing position backwards for a distance. Then, or at the same time, the piston moves forward and passes through the burr ring at the interface between the contact surfaces. Thereafter, both the first mandrel and the second mandrel move to their respective release positions, wherein the piston travels through the interface between the contact surfaces for the second time and travels through the interface between the adjacent surfaces. Since the piston travels through the burr rings, these burr rings are at least partially scraped off from the inner surface of the through hole.

[0034] The pressing tool according to the present invention is suitable for forming a cutting blade blank by pressing powders such as cermets, carbide powders or metallurgical powders. After the finished cutting blade blank has been formed and removed from the pressing tool, it can be subjected to other treatments such as sintering, grinding, edge treatment and / or coating. The cutting blade can be obtained from the cutting blade blank and used for processing (e.g. metal cutting). Examples of such cutting blades are milling cutting blades, turning cutting blades and drilling cutting blades.

[0035] The pressing tool according to the invention may be of any suitable type. Preferably, the pressing tool comprises a die and two punches which are movable towards and away from each other along a punch axis. For example, the pressing tool is a so-called uniaxial pressing tool comprising a die and two punches; a so-called split-die pressing tool comprising a die with at least two movable parts and two movable punches; or a so-called cross-hole pressing tool, in which the core axis is perpendicular to the punch axis. The space defined by the die and the punches in their closest position constitutes a compression space which corresponds to the shape and size of the cutting insert blank.

[0036] The first core rod and the second core rod are both arranged longitudinally along the core axis, with their respective front ends facing each other. The core axis can have any suitable extension in the pressing tool, such as horizontal extension or vertical extension. In a pressing tool including a movable punch, the core axis can be the same as the punch axis or perpendicular to the punch axis. In a pressing tool including a split mold (the split mold includes two halves that can move toward and away from each other along the mold axis), the core axis can coincide with the mold axis, or be perpendicular to one or both of the mold axis and the punch axis.

[0037] Preferably, the longitudinal axis of the first mandrel and the longitudinal axis of the second mandrel are aligned and coincident with the core axis. However, the axes may be slightly offset and parallel.

[0038] The forward movement of the mandrel is in the direction towards the other mandrel, and the backward movement is away from the other mandrel.Therefore, the forward movement can be a movement towards the center of the compression space, but it can also be a movement through the center.

[0039] Optionally, the first mandrel and the second core are separate components, or one or both of the first mandrel and the second core are integral and one-piece with the rest of the pressing tool. For example, the mandrel may be part of a punch or a die half and can only move together with the punch or the die half. However, it is preferred that the mandrel is a separate component that is movably guided in the pressing tool, for example in a die or a punch.

[0040] According to at least one embodiment, the first and second mandrels are arranged to be independently movable. Advantageously, the first mandrel can thus be brought to any of its positions independently of the position of the second mandrel, and vice versa. In another embodiment, the first mandrel and the second mandrel are arranged to be synchronously movable. Advantageously, the movement of the first and second mandrels towards and away from each other is thus easier to drive and control. Optionally, the piston is movable at least partially independently of the movement of the first mandrel and the second mandrel. The movement of the mandrels and the piston can be driven using one or several drive units, such as, for example, an electric motor, a pneumatic or hydraulic drive unit. The operation of the drive unit can be controlled by a control unit, such as a PLC (Programmable Logic Controller).

[0041] Preferably, the first mandrel is movable to a scraping position in which the forwardly facing abutment surface of the base body is at most as far forward as when the first mandrel is in the pressing position. The piston is in a first extended position of a plurality of extended positions in which the contact surface in the form of the front end surface of the head is further forward than in the pressing position. Thus, the base body of the first mandrel does not have to be moved further forward in order to drive the head of the piston forward.

[0042] According to at least one embodiment, the second mandrel comprises a segment tapering towards the front end, the base comprises a segment tapering towards the front end, the head has a constant cross section, and wherein, in the pressing position, the length (L) comprises at least a portion of the tapering segment of the second mandrel, the head and at least a portion of the tapering segment of the base. This is advantageous because a cutting insert blank having a through hole with countersunk heads at both ends can be formed in the pressing tool. Optionally, the tapering segments can extend all the way to the front end, or the segments can include a portion having the same cross section as the head closest to the front end.

[0043] Preferably, the first mandrel and the second mandrel together form a continuous mandrel when the first mandrel and the second mandrel are in their respective pressing positions.

[0044] Specifically, the shape of the cross section of the second mandrel at its contact surface is the same as the shape of the cross section of the head at its contact surface, and / or the shape of the cross section of the head at the adjacent surface is the same as the shape of the cross section of the substrate at the adjacent surface. For example, the shape of the cross section of the head and the mandrel over the length (L) is elliptical or cylindrical. The size of the cross section of the substrate and the second mandrel may increase from the head backward. At least along the length (L), the continuous mandrel may be mirror-symmetrical relative to a cross-sectional plane located at the center of the length (L). The longitudinal center of the length (L) may correspond to the longitudinal center of the head.

[0045] Optionally, when both mandrels are in their respective pressing positions, both contact surfaces are in a central position along the length (L), or are in a position lateral to the central position. Thus, during operation, the length (L) may be occupied by portions of mandrels having equal lengths, or the first mandrel may occupy a greater length than the second mandrel, or vice versa.

[0046] Preferably, the longitudinal length of the head is at least 1 mm shorter than the length (L). Preferably, the longitudinal length of the head is greater than 0.5 mm, more preferably greater than 1.3 mm. According to at least one embodiment, the longitudinal length of the head is 1 / 3 of the length (L).

[0047] According to at least one embodiment, the head has a length in the axial direction of the core axis, wherein in the pressing position, the axial length of the head can be reduced by 5-40 μm, preferably by 20-30 μm. This allows the pressing tool to be designed to provide additional compaction in the direction of the core axis, which is advantageous when forming a cutting insert blank with a countersunk head. For example, the head comprises a material having a Young's modulus (E) of less than 400 GPa, such as steel, or the head comprises a piezoelectric disk that can be operated to change its thickness.

[0048] According to at least one embodiment, the piston is arranged to be biased towards the first extended position. Thus, when the second mandrel moves backward, the piston automatically moves to the extended position, for example a more forward position, such as a scraping position. For example, a resilient element such as a spring can be arranged to press the piston forward to the extended position. Alternatively, the first mandrel can be configured to provide a bias to the piston by a pressurized fluid (e.g., air or oil).

[0049] Preferably, the first mandrel includes a stop mechanism that defines a maximum extension position of the plurality of extension positions of the piston. Therefore, when the piston is in the maximum extension position and the base moves backward, the piston will move backward with the base. The stop mechanism also prevents the piston from disengaging from the base.

[0050] According to at least one embodiment, the base body has a hole extending backwards from an opening in the front end of the base body, and the rear end of the shaft extends through the opening and into the hole. The forwardly facing abutment surface of the base body is the front end surface surrounding the opening. This is a convenient design of the first mandrel, which allows the shaft to be guided in the base body in the hole. In embodiments comprising a biasing element and / or a stop mechanism, the biasing element and / or the stop mechanism can be arranged in the hole.

[0051] According to at least one embodiment, the front end of one of the first mandrel and the second mandrel includes a recess extending backward, and the front end of the other of the first mandrel and the second mandrel includes a mating protrusion extending forward, wherein the protrusion is received in the recess when the first mandrel and the second mandrel are both in their respective pressing positions for aligning the first mandrel and the second mandrel. For example, the head includes a male protrusion protruding forward from the front end, and the second mandrel includes a mating female depression extending backward from the front end. With good alignment of the first mandrel and the second mandrel, good tolerances of the through hole of the cutting insert blank can be achieved.

[0052] Optionally, the contact surface is a front end surface facing forward. For example, the contact surface is a front end surface perpendicular to the core axis. In an embodiment with a mating protrusion / recess, the contact surface may be a surface of the protrusion / recess. In such an embodiment, the contact surface may also be or include a portion of a circumferential surface that is longitudinally extended forward of the protrusion / recess.

[0053] Optionally, the opening of the hole in the substrate comprises a countersunk portion.

[0054] According to at least one embodiment, the piston further comprises a neck extending along the core axis from the rear end of the head to the front end of the shaft and cooperating with a countersunk head in the base body hole. When the piston is in the retracted position, the neck is received in the countersunk head for aligning the piston and the base body. With good alignment of the piston and the base body, good tolerances of the through hole in the cutting insert blank can be achieved.

[0055] Preferably, both the front and rear ends of the head include protrusions cooperating with corresponding recesses in the second mandrel and the base body, respectively, for providing even better alignment, thereby further improving the tolerance of the through hole in the cutting insert blank. The protrusions / recesses may include tapered cooperating guide surfaces.

[0056] According to at least one embodiment, the countersunk head in the base does not cooperate with a corresponding neck of the head. Instead, the countersunk head is configured to receive debris from the scraped burr ring, thereby removing the debris from the surface of the shaft. Thus, wear caused by the debris sliding on the surface of the shaft and the inner surface of the through hole can be reduced. In addition, or alternatively, the head can be provided with an annular groove in the rearwardly facing abutment surface defining the shaft.

[0057] To improve the wear resistance of the head, the head may comprise cemented carbide.The head may be provided with a wear resistant coating, preferably deposited by PVD or CVD techniques.

[0058] Preferably, the piston is removably received in the base body. Thus, if the head is worn due to scraping off the burr ring (for example at the circumferential edge), the piston can be replaced.

[0059] According to at least one embodiment, the forward facing abutment surface of the base is a front end surface defining an opening in the base, and the rearward facing abutment surface of the head is a rear end surface defining the neck. Optionally, the abutment surface is perpendicular to the core axis. In embodiments with a mating neck / countersunk head, the abutment surface may also be or include part of a longitudinally extending circumferential surface of the neck / countersunk head.

[0060] According to at least one embodiment, the shaft and the hole in the base have the same cross-sectional shape at least along the portion closest to the opening. The inner dimensions of the hole are adapted to the outer dimensions of the shaft so that the shaft fits in sliding contact in the hole. The cross-sectional shape of the shaft and the hole can be circular. Optionally, the cross section has a shape that prevents relative rotation. For example, the cross-sectional shape is polygonal or includes a circular portion with straight edges. Alternatively, the shaft is provided with a radially protruding pin that is received in a slot in the hole.

[0061] According to at least one embodiment in which the core axis is horizontal, the shaft has side surfaces that converge upwards to form a ridge. Thus, debris from the scraped burr ring that falls on the shaft will be directed downwards away from the shaft. This reduces the risk of debris getting stuck at the opening and reduces the risk of debris causing the shaft to become blocked in the hole or to wear. For example, the shaft may have a triangular cross section.

[0062] At least one embodiment of the method of forming a cutting insert blank having a through hole having a length (L) using a pressing tool according to the present invention comprises: using a pressing tool according to the present invention and any embodiment thereof. The steps of the method of the present invention can be performed in any order suitable for the process.

[0063] Preferably, before starting the first pressing cycle, the steps of producing the pressing tool and arranging the first core rod, the second core and the piston in the pressing tool are first performed. In subsequent pressing cycles, these steps can be excluded.

[0064] Preferably, the following steps may be performed in any order:

[0065] - moving the piston along the core axis into a retracted position in which the abutment surface of the head abuts against the abutment surface of the base body,

[0066] - moving the first mandrel and the second mandrel along the mandrel axis to respective pressing positions, wherein their respective contact surfaces contact each other within the cavity in a compression space corresponding to the size of the blank, and

[0067] -Filling the cavity with a predetermined amount of powder.

[0068] According to an embodiment using a cross hole pressing tool, the first of these steps is to move the piston, the second is to move the first mandrel and the second mandrel, and the third is to fill the cavity. Both the first and second mandrels are moved forward into the cavity to reach their respective pressing positions.

[0069] According to an embodiment using a uniaxial pressing tool, the first of these steps is to fill the cavity, the second step is to move the piston, and the third step is to move the first mandrel and the second mandrel. The second mandrel moves back from a filling position in the cavity and the first mandrel moves forward to reach their respective pressing positions.

[0070] Preferably, the step of operating the cavity to compress the compression space is performed after the above three steps. Preferably, the step of operating the cavity to compress the compression space includes the step of moving the punches toward each other according to a predetermined scheme. For example, the movement of the punches can follow a curve that has a steeper inclination, for example, at the beginning of the compression step than at the end of the compression step. In an embodiment using a pressing tool including a split mold, the movement of the mold parts also follows a predetermined scheme. The movement of the mold parts can follow a curve that has a steeper inclination, for example, at the beginning of the compression step than at the end of the compression step. Optionally, the movement of each punch, and where applicable, the movement of each mold is controlled individually, or all or part of it moves synchronously.

[0071] When the cavity reaches the desired compression, a compression space is defined between the die and the punch. The compression space corresponds to the shape and size of the cutting insert blank.

[0072] According to an embodiment, the method comprises an unloading step after the compression step, wherein the punch is retracted only a short distance, for example 0.05-0.1 mm, in order to relax the blank so as to facilitate the subsequent movement of the core rod.

[0073] Optionally, the step of moving the second mandrel backwards includes moving the second mandrel completely out of the through hole of the blank, or at least out by 0.1 mm. Thus, the head has enough space to move forward and scrape off the burr ring that may have been formed during the powder compression step. Wherein, the head reaches a first extended position that is further forward than the pressing position. In the first extended position, the contact surface of the head is further forward than the burr ring formed at the interface between the contact surfaces during the compression step. In an embodiment of the method using a biased piston, the forward movement of the head is combined with the backward movement of the second mandrel.

[0074] Preferably, the forward movement of the head to the first extended position is at least the thickness of the burr ring, which is typically less than 0.1 mm. Preferably, the forward movement of the head is equal to the longitudinal length of the head.

[0075] Preferably, the following step comprises moving the first mandrel and the second mandrel to their respective release positions. Optionally, both mandrels are placed with their contact surfaces outside the through hole, or only one of the first and second mandrels is placed with its contact surface outside the through hole. Preferably, when both the first and second mandrels have been moved to their respective release positions, the distance between the contact surfaces is at least 1 mm greater than the length (L) of the through hole, preferably at least 5 mm greater.

[0076] Preferably, the step of operating the cavity to decompress the compression space comprises the step of moving the punch and, where applicable, the die parts away from each other according to a predetermined scheme, wherein the punch and any movable die parts may follow a curve that is less steep at the beginning of the decompression step than at the end of the decompression step.

[0077] Finally, the cutting insert blank is removed from the pressing tool. In an embodiment in which one of the core rods has a release position in the through hole, the cutting insert blank is lifted off the core rod and only then separated from the pressing tool. Optionally, in both the pressing position and the release position, the contact surface of one of the first and second core rods has the same position in the compression space. In an embodiment in which the distance between the contact surfaces in the release position is only a small distance greater than the length (L), the cutting insert blank is removed from the cavity perpendicular to the core axis. BRIEF DESCRIPTION OF THE DRAWINGS

[0078] In the following, example embodiments will be described in more detail with reference to the accompanying drawings, in which:

[0079] Figure 1 is an exploded view with partially cutaway portions of a general design of a press tool according to an embodiment of the present invention as implemented in a cross-hole press tool;

[0080] Figure 2 shows a longitudinal cross-section of a first mandrel and a second mandrel according to a first embodiment;

[0081] Figure 3 is a top view of a pressing tool according to a first embodiment;

[0082] Figure 3a-3f The pressing tool of the first embodiment of the method according to the present invention is as follows Figure 3 Longitudinal section shown;

[0083] Figure 4-6 shows a longitudinal cross-section of a first mandrel and a second mandrel according to a further embodiment;

[0084] Figure 7a-7c is a cross-sectional view through a substrate of another embodiment;

[0085] Figure 8 shows a longitudinal cross-section of a first mandrel and a second mandrel according to another embodiment;

[0086] Figure 9-11 A longitudinal cross section of a first mandrel according to a further embodiment is shown.

[0087] All the drawings are schematic, not necessarily drawn to scale, and generally only show parts which are necessary for explaining the respective embodiments, while other parts may be omitted or merely suggested. Unless otherwise specified, the same reference numerals in different drawings denote the same or corresponding parts. DETAILED DESCRIPTION

[0088] exist Figure 1 In the figure, the overall design of an embodiment of a pressing tool according to the present invention is shown in an exploded view. The pressing tool is a cross-hole pressing tool with a die 1. In the figure, the die is shown as being broken in the middle so as to show its interior. The pressing tool also includes an upper punch 2 and a lower punch 3. The upper punch 2 and the lower punch 3 are movable toward and away from each other along the punch axis. The die 1, the upper punch 2 and the lower punch 3 define a cavity 4 between them. The cavity (4) is operable to define a compression space by moving the punches toward each other along the vertical punch axis. The compression space corresponds to the space and size of the cutting insert blank 5 to be formed by the pressing tool. In Figure 1 In the embodiment, the compression space is occupied by a cutting insert blank 5 having a through hole 6 having a length (L), see Figure 3f .

[0089] The pressing tool further comprises a first mandrel 7 and a second mandrel 8. The first mandrel 7 and the second mandrel 8 each have a longitudinal extension from a front end to a rear end and a contact surface 9 at the front end. The first mandrel 7 and the second mandrel 8 are longitudinally arranged along a horizontal core axis 10, wherein the respective central longitudinal axes of the first mandrel 7 and the second mandrel 8 coincide with the core axis 10, and the respective contact surfaces 9 of the first mandrel 7 and the second mandrel 8 face each other. Both the first mandrel 7 and the second mandrel 8 are arranged in a movable manner in both directions of the core axis 10. The forward movement of the mandrel is in a direction towards the other mandrel, and the backward movement is away from the other mandrel.

[0090] Reference Figure 2 , the first mandrel 7 comprises a longitudinal rearward portion in the form of a base body 11 and a piston 12. In the longitudinal forward portion, the base body comprises a segment 16 which tapers towards the front end. The hole 15 extends rearward from an opening in the tapered segment 16 at the front end of the base body 11. The forward facing abutment surface 17 is a front end surface around the opening which is perpendicular to the core axis 10.

[0091] The piston 12 comprises a rear portion in the form of a longitudinally extending shaft 13, and a head 14 at the front end of the shaft, which radially protrudes from the shaft 13. The shaft 13 is longitudinally movably arranged in a hole 15 of the base body 11. Both the longitudinal axis of the shaft and the longitudinal axis of the hole coincide with the core axis 10. The contact surface 9 of the first mandrel is the front end surface of the head 14, which is perpendicular to the core axis 10. The head 14 has a rearwardly facing abutment surface 17, which is a rear end surface delimiting the shaft 13 and perpendicular to the core axis 10.

[0092] The second mandrel 8, the base body and the piston 12 are all arranged to be independently movable. Thus, each of the second mandrel 8, the base body and the piston 12 can be brought into position individually and independently of the position of the other two of the second mandrel 8, the base body and the piston 12. The individual movements are driven by electric motors which are controlled by a control unit (not shown) in the form of a PLC.

[0093] In the longitudinal forward portion, the second mandrel 8 comprises a section 18 which tapers towards the front end. The contact surface 9 of the second mandrel 8 is a front end surface which is perpendicular to the core axis 10.

[0094] The typical length (L) of the through hole of the cutting insert blank 5 that can be formed in the pressing tool of the present invention is 6-10 mm. In the cutting insert blank 5 having a through hole 6 (with countersunk heads on both sides), the typical length of the cylindrical center portion of the through hole 6 is 1-5 mm. In an exemplary embodiment, the longitudinal length of the head is 1.3 mm, a portion of 1 mm of the total length (L) is formed by the tapered segment of the second core rod 8, and a portion of 0.7 mm of the total length (L) is formed by the tapered segment 16 of the first core rod 7. The cross-section of the head 14 and the core rod over the length (L) is elliptical. The head 14 has a constant cross-section. The typical size of the major axis of the elliptical cross-section of the head is 3-10 mm, and is 5.4 mm in the exemplary embodiment.

[0095] The die, the punch, the second core rod 8, the base 11 and the shaft 13 of the piston 12 are made of cemented carbide. The head 14 of the piston 12 is made of steel having a Young's modulus (E) of 200 GPa.

[0096] Reference Figure 3-3f , the following is an embodiment of a method of forming a cutting insert blank using the above-described first embodiment of the pressing tool of the present invention.

[0097] exist Figure 3a, both the first mandrel 7 and the second mandrel 8 are longitudinally arranged along the core axis 10, wherein their respective contact surfaces 9 at the respective front ends of the first mandrel 7 and the second mandrel 8 face each other. The shaft 13 of the piston 12 is arranged in the hole 15 of the base 11, wherein the longitudinal axis of the shaft 13 coincides with the core axis 10. The piston 12 moves along the core axis 10 to a retracted position, wherein the abutment surface 17 of the head 14 abuts against the abutment surface 17 of the base 11.

[0098] The first mandrel 7 and the second mandrel 8 move to their respective pressing positions along the core axis. The first mandrel 7 and the second mandrel 8 both move forward toward the center position in the cavity 4. Figure 3b In their respective pressing positions shown, their respective contact surfaces 9 are in contact with each other in the cavity 4 in the compression space. The piston 12 is still in the retracted position, wherein the abutment surfaces 17 abut against each other. The lower punch 3 is raised to form a bottom in the cavity 4, and the cavity 4 is filled with a predetermined amount of metallurgical powder 19. The powder 19 flows around and through the first core rod 7 and the second core rod 8, and fills a part of the cavity from below and above. Finally, the first core rod 7 and the second core rod 8 are surrounded by the powder 19.

[0099] exist Figure 3c , the cavity is operated to compress the powder 19 by moving the upper punch 2 and the lower punch 3 toward each other and thereby compressing the powder 19 in the compression space. The compression space is a reduced space in the cavity 4 and has the same shape and size as the cutting insert blank 5 to be formed. At the beginning of the compression, the punch moves faster than at the end. During the compression, the first mandrel 7 and the second mandrel 8 remain in their respective pressing positions. As can be seen, the through hole 6 having a length (L) is formed by the first mandrel 7 and the second mandrel 8, wherein the first mandrel 7 and the second mandrel 8 together form a continuous mandrel. Among them, a part of the length (L) is occupied by the tapered segment 18 of the second mandrel 8, a part of the length (L) is occupied by the head 14, and a part of the length (L) is occupied by the tapered segment 16 of the base 11. The continuous mandrel formed by the first mandrel 7 and the second mandrel 8 is mirror-symmetrical with respect to the cross-sectional plane passing through the longitudinal center of the head 14. The continuous mandrel with the tapering section forms a through hole 6 which has countersunk parts on both sides.

[0100] In order to compact an additional amount of powder at the countersunk head, the core rod is pushed together to force the head 14 to elastically reduce its length by about 20-30 μm.

[0101] After the punches have reached their closest position and the powder 19 has been compressed by a predetermined amount, the pressing tool is unloaded by moving the upper punch 2 and the lower punch 3 apart by a small distance of 0.07 mm. This allows the compressed body to relax and prevents the first core rod 7 and the second core rod 8 from getting stuck in the through hole 6.

[0102] During compression, annular burr rings 20 are formed in the bore wall of the through hole 6 where the contact surface and the abutment surface meet, i.e. at both sides of the head 14. To remove these annular burr rings, the second mandrel 8 is moved back along the core axis 10 so that its contact surface 9 is outside the through hole 6 and the compression space. Thereafter, as in Figure 3d As seen in FIG. 1 , the piston 12 moves forward along the core axis 10 to the first extended position, while the base 11 remains stationary. When the base 11 and the piston 12 are arranged in this way, the first mandrel 7 is in the scraping position. Since the head 14 has a constant cross-section equal to the minimum cross-section of the tapered segment 18 of the second mandrel 8, the head can move forward without damaging the countersunk head provided by the tapered segment 18 of the second mandrel 8. In addition, the forward-facing abutment surface of the base 11 is longitudinally in the same position in the through hole 6 as when the first mandrel 7 is in the pressing position. Therefore, when the piston 12 moves forward, the countersunk head provided by the tapered segment 16 of the base remains unaffected. During the forward movement of the piston 12 to the first extended position, the head travels past the burr ring 20 formed in the through hole wall at the location of the interface between the contact surfaces 9. Therefore, the outer surface of the head 14 (especially the circumferential front edge) scrapes the burr ring 20 from the hole wall.

[0103] refer to Figure 3e , the base body 11 moves backward along the core axis 10 so that its abutment surface 17 is outside the through hole 6 and the compression space. Then, the piston 12 moves backward along the core axis 10. Therein, the head 14 passes through the burr ring 20 formed in the through hole wall at the position of the interface between the contact surfaces for the second time. Then, as the head 14 moves further backward, the head 14 passes through the burr ring 20 previously formed at the position of the interface between the abutment surfaces 17. Therefore, the outer surface of the head 14 (especially the circumferential rear edge) scrapes the burr ring 20 from the hole wall. Since the head 14 has a constant cross-section equal to the minimum cross-section of the tapered segment 16 of the base body 11, the head can move backward without damaging the countersunk head provided by the tapered segment 16.

[0104] Finally, the piston 12 is moved back so far that the contact surface 9 is located outside the through hole 6 and the compression space. Then, the contact surface 9 of the first mandrel 7 and the contact surface 9 of the second mandrel 8 are separated by a distance (21) greater than the length (L) of the through hole 6. Figure 3fIn the embodiment of the present invention, the cavity is operated to decompress the compressed space by moving the upper punch 2 and the lower punch 3 away from each other. At the beginning of the decompression, the punch moves slower than at the end. Finally, the cutting insert blank 5 formed by compressing the metallurgical powder 19 in the pressing tool is removed. The cutting insert blank 5 has a through hole 6 with countersunk parts at both ends.

[0105] exist Figure 4-11 In the embodiment of the present invention, alternative embodiments are shown. These embodiments differ from the first embodiment described above mainly in the construction of the first mandrel 7, which is why Figure 4-11 And the description is limited to the reasons for these components.

[0106] Figure 4 The second core 8 and the base 11 are shown, neither of which has a tapered section. Instead, the front portion of the second core rod 8, the head 14 and the front portion of the base 11 all have the same constant cross section. When the first and second core rods 7, 8 are in their respective pressing positions, a continuous core rod of constant cross section is formed. The continuous core rod forms a through hole 6 of constant cross section without a countersunk head.

[0107] Figure 5 A first mandrel 7 is shown, wherein the piston 12 is biased towards a first extended position. The hole 15 in the base 11 comprises a longitudinal front portion with a smaller cross section for guiding the shaft 13 and a longitudinal rear portion with a larger cross section. The shaft 13 extends into the rear portion. The rear end of the shaft comprises a thread on which a stop nut 22 is threaded. The stop nut can slide in the larger rear portion of the hole 15. At the rear end of the rear portion of the hole 15, a support block 23 is fixed to the hole wall. An elastic element in the form of a coil spring 24 is attached to the support block 23 at the rear end and to the stop nut 22 at the front end. Due to the force exerted by the coil spring 24 acting between the fixed support block 23 and the movable stop nut 22, the piston 12 is biased towards the extended position. This force can be adjusted by fixing the support block 23 at other longitudinal positions in the rear portion of the hole 15.

[0108] The maximum extension position of the piston 12 is defined by the stop nut 22 abutting against the front wall of the rear part of the hole 15. Therefore, the stop nut 22 and the front wall of the rear part of the hole 15 together form a stop mechanism. In this example, the stop mechanism comprises the rearward-facing front wall of the hole 15 and the forward-facing front surface of the stop nut 22, which are arranged oppositely and face each other along the core axis 10. When the piston 12 is in this maximum extension position and the base 11 moves backward, the piston 12 will move backward together with the base 11. The piston 12 is also prevented from detaching from the base 11.

[0109] Figure 6 The embodiments shown and reference Figure 5 The embodiment described differs in that the hole 15 has a constant cross section. A coil spring 24 is attached to the bottom of the hole 15 at the rear end and to the rear end of the shaft 13 at the front end. The first mandrel 7 is provided with a stop mechanism comprising a longitudinal slot 25 in the shaft 13 and a pin 26 protruding radially into the hole 15 and the slot 25. The maximum extension position of the piston 12 is defined by the abutment of the pin 26 against the rear wall of the slot 25. In this example, the stop mechanism comprises the forward facing rear wall of the slot 25 and the rearward facing surface of the pin 26, which are arranged oppositely and facing each other along / parallel to the core axis 10. An advantage of this embodiment is that a prior art mandrel can be retrofitted with the biasing piston 12 and the stop mechanism without having to access the rear end of the first mandrel 7.

[0110] In an alternative embodiment, the shaft 13 is provided with a radially projecting pin 26 which is received in a slot 25 in the hole 15 .

[0111] In an alternative embodiment, the biasing force is provided by introducing a pressurized fluid (such as air or oil) into the bore 15 .

[0112] Figure 7a-7c A cross section of a first mandrel 7 of a shaft 13 passing through a hole 15 of a base body 11 is shown, wherein a relative rotation of the shaft 13 and the base body 11 is prevented, according to various embodiments. Figure 7a In FIG. 1 , the shaft 13 and the hole 15 each have a planar surface 27. Figure 7b In the embodiment, the shaft is provided with a ridge 28 which is arranged in a slot 29 in the wall of the hole 15 in the base body 11. Figure 7c In the embodiment of the present invention, the shaft 13 is polygonal, and in this case triangular. When used in a press tool with a horizontal core axis 10, such as the cross hole press tool described above, the debris of the scraped burr ring 20 that falls on the shaft 13 will slide along the diverging side surfaces and is therefore less likely to get stuck between the shaft 13 and the hole 15.

[0113] exist Figure 8 , an embodiment is shown in which the front end of one of the second mandrels 8 includes a recess 30 extending rearward, and the front end of the head 14 includes a mating protrusion 31 extending forward. The contact surface 9 of the second mandrel 8 is the bottom surface of the recess 30, and the contact surface 9 is the front end surface of the protrusion 31. The circumferential side surfaces of the recess 30 and the protrusion 31 are tapered. When the first mandrel 7 and the second mandrel 8 are moved to their respective pressing positions, these tapered side surfaces guide the first mandrel 7 and the second mandrel 8 to align when the contact surfaces 9 come into contact.

[0114] exist Fig. 9, an embodiment is shown in which the opening of the hole 15 is provided with a countersunk head 32. The piston 12 comprises a neck 33 which extends along the core axis from the rear end of the head to the front end of the shaft and cooperates with the countersunk head 32 in the hole 15 of the base. The circumferential side surfaces of the countersunk head 32 and the neck 33 are tapered. These tapered side surfaces guide the head 14 when the piston 12 is retracted into the base 11. Therefore, when the corresponding abutment surfaces of the piston 12 and the base 11 abut against each other, the piston 12 and the base 11 are aligned.

[0115] Fig.10 and Fig.11 An exemplary embodiment is shown in which each of the annular grooves 34 is arranged in the abutment surface 17. Fig.11 In the embodiment of the invention, an annular groove 34 is provided in the abutment surface 17 around the opening of the hole 15. The annular groove 34 has a square cross section. Fig.11 In the embodiment, an annular groove 34 is provided in the abutment surface 17 of the head 14. Fig.11 In the embodiment of the present invention, both annular grooves 34 have a semicircular cross section. When used in a pressing tool (such as the cross hole pressing tool described above), the scraped burr ring 20 can be collected in these annular grooves 34 and is therefore less likely to get stuck between the shaft 13 and the hole 15.

Claims

1. A pressing tool for forming a cutting insert blank (5) by compressing powder, the cutting insert blank (5) having a through hole (6) having a length (L), the pressing tool comprising: - a cavity (4) operable to define a compression space corresponding to the dimensions of the cutting insert blank (5), - a first mandrel (7) and a second mandrel (8) for forming together the through hole (6), the first mandrel (7) and the second mandrel (8) each having a longitudinal extension from a front end to a rear end and a contact surface (9) at the front end, in, - the first mandrel (7) and the second mandrel (8) are both arranged longitudinally along the core axis (10), wherein respective front ends of the first mandrel (7) and the second mandrel (8) face each other, - the first mandrel (7) and the second mandrel (8) are both arranged in a movable manner in both directions of the mandrel axis (10), wherein the first mandrel (7) and the second mandrel (8) are both movable to respective pressing positions and to respective release positions, wherein - when both the first mandrel (7) and the second mandrel (8) are in their respective pressing positions, respective contact surfaces (9) of the first mandrel (7) and the second mandrel (8) are in contact with each other in the compression space, and wherein, - when both said first mandrel (7) and said second mandrel (8) are in their respective release positions, the respective contact surfaces (9) of said first mandrel (7) and said second mandrel (8) are separated by a distance greater than said length (L), It is characterized in that The first mandrel (7) comprises: - a longitudinally extending rearward portion in the form of a base body (11) comprising a forwardly facing abutment surface (17) at a front end, and a piston (12) having a rear portion in the form of a longitudinally extending shaft (13) and a front portion in the form of a radially protruding head (14), in, - the contact surface (9) is the front end surface of the head (14), - the head (14) comprises a rearwardly facing abutment surface (17) at the rear end, and wherein the shaft (13) is arranged longitudinally movably in the base body (11) along the core axis (10), so that the piston (12) can be moved into a plurality of extended positions and into a retracted position in which the abutment surface (17) of the head (14) abuts against the abutment surface (17) of the base body (11), Wherein, when both the first mandrel (7) and the second mandrel (8) are in their respective pressing positions, the piston (12) is in the retracted position.

2. The pressing tool according to claim 1, wherein The first mandrel (7) is movable to a scraping position, wherein - said forwardly facing abutment surface (17) of said base body (11) is at most as far forward as said first mandrel (7) is in said pressing position, and wherein The piston (12) is in a first extended position of the plurality of extended positions, wherein the contact surface (9) in the form of the front end surface of the head (14) is further forward than in the pressed position.

3. The pressing tool according to claim 1 or 2, wherein: The second mandrel (8) includes a segment (18) that tapers toward the front end, the base (11) includes a segment (16) that tapers toward the front end, the head (14) has a constant cross-section, and wherein, in the pressing position, the length (L) includes at least a portion of the tapered segment (18) of the second mandrel (8), the head (14) and at least a portion of the tapered segment (16) of the base (11).

4. The pressing tool according to any one of claims 1 to 2, wherein: The piston (12) is arranged to be biased towards the first extended position.

5. The pressing tool according to claim 4, wherein: The piston (12) is arranged to be biased by a resilient element (24) which abuts a forwardly facing surface of the base body (11) at a rearward end and a rearwardly facing surface at the shaft (13) at a forward end.

6. The pressing tool according to any one of claims 1 to 2, wherein: The first mandrel (7) comprises a stop mechanism which defines a maximum extension position of the piston (12) among the plurality of extension positions.

7. The pressing tool according to claim 6, wherein: The stop mechanism comprises: - a substrate stop surface, and - shaft stop surface, in, - when viewed along the core axis (10), the base stop surface and the shaft stop surface are arranged opposite and face each other, and wherein, - When the piston (12) is in the maximum extended position, the base stop surface and the shaft stop surface are in contact with each other.

8. The pressing tool according to any one of claims 1 to 2, wherein: The front end of one of the first mandrel (7) and the second mandrel (8) includes a rearwardly extending recess (30), and the front end of the other of the first mandrel (7) and the second mandrel (8) includes a matching forwardly extending protrusion (31), wherein, when both the first mandrel (7) and the second mandrel (8) are in their respective pressing positions, the protrusion (31) is received in the recess (30) for aligning the first mandrel (7) and the second mandrel (8).

9. The pressing tool according to any one of claims 1 to 2, wherein: - the base body (11) has a hole (15) extending rearwardly from an opening in the front end of the base body (11), - the rear end of the shaft (13) extends through the opening and into the hole (15), - The forwardly facing abutment surface (17) of the base body (11) is a front end surface surrounding the opening.

10. The pressing tool according to claim 9, wherein The opening of the hole (15) in the base body (11) comprises a countersunk portion (32).

11. The pressing tool according to claim 10, wherein The piston (12) further comprises a neck (33) extending along the core axis (10) from the rear end of the head (14) to the front end of the shaft (13), and the neck cooperates with the countersunk head (32), wherein - the rearwardly facing abutment surface (17) of the head (14) is the rear end surface defining the neck (33), and - When the piston (12) is in the retracted position, the neck is received in the countersunk head for aligning the piston (12) and the base (11).

12. The pressing tool according to any one of claims 1 to 2, wherein: The core axis (10) is horizontal and the shaft (13) has side surfaces that converge upwards to form a ridge.

13. The pressing tool according to any one of claims 1 to 2, wherein: The head (14) has a length in the axial direction of the core axis (10), wherein the axial length of the head (14) can be reduced by 5-40 μm in the pressing position.

14. The pressing tool according to claim 13, wherein The axial length of the head (14) can be reduced by 20-30 μm in the pressed position.

15. A method of forming a cutting insert blank (5) having a through hole (6) having a length (L) using a pressing tool, wherein: The pressing tool comprises: - a cavity (4), - a first mandrel (7) and a second mandrel (8), each of the first mandrel (7) and the second mandrel (8) having a longitudinal extension from a front end to a rear end and a contact surface (9) at the front end, wherein the first mandrel (7) comprises: - a longitudinally extending rearward portion in the form of a base body (11), said longitudinally extending rearward portion comprising a forwardly facing abutment surface (17) at a front end, a piston (12) having a rear portion in the form of a longitudinally extending shaft (13) and a front portion in the form of a radially protruding head (14), wherein the contact surface (9) is the front end surface of the head (14) and the head (14) comprises a rearwardly facing abutment surface (17) at the rear end, The method comprises the following steps: - longitudinally arranging both the first mandrel (7) and the second mandrel (8) along the mandrel axis (10), the respective front ends of the first mandrel (7) and the second mandrel (8) facing each other, - the piston (12) and its shaft (13) are arranged longitudinally in the base body (11) along the core axis (10), - moving the piston (12) along the core axis (10) into a retracted position, wherein the abutment surface (17) of the head (14) abuts against the abutment surface (17) of the base body (11), - moving the first mandrel (7) and the second mandrel (8) along the mandrel axis (10) to respective pressing positions, wherein respective contact surfaces (9) of the first mandrel (7) and the second mandrel (8) are in contact with each other within the cavity (4) in a compression space corresponding to the dimensions of the cutting insert blank (5), - filling the cavity (4) with a predetermined amount of powder, - operating the cavity (4) to compress the powder in the compression space to form the cutting insert blank (5), - moving the second mandrel (8) backwards along the mandrel axis (10) and moving the piston (12) forwards to a first extended position, - moving the first mandrel (7) and the second mandrel (8) along the mandrel axis (10) to respective release positions, wherein respective contact surfaces (9) of the first mandrel (7) and the second mandrel (8) are separated by a distance greater than the length (L), and - operating the cavity (4) to decompress the compression space, and - Removing the cutting insert blank (5).

16. The method according to claim 15, wherein: After the step of moving the first mandrel (7) and the second mandrel (8) to the corresponding pressing positions and the step of moving the piston (12) along the core axis (10) to the retracted position, the method comprises the following step: reducing the axial length of the head (14) in the direction of the core axis (10) by 5-40 μm by moving the contact surface (9) of the first mandrel (7) and the contact surface (9) of the second mandrel (8) against each other.

17. The method according to claim 16, wherein: The axial length of the head (14) in the direction of the core axis (10) is reduced by 20-30 μm.

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