METHOD FOR MANUFACTURING A TOOL HEAD

Abstract

A method for manufacturing a tool head includes forming a first and a second part from a powder composition. The first and the second parts include corresponding joining surfaces, and the parts have outer surface portions configured to form portions of a peripheral envelope surface of the tool head. The method further includes forming corresponding grooves in the corresponding joining surfaces, assembling the parts into a shape of a tool head by bringing the joining surfaces into contact to form an interface, so that each pair of corresponding grooves forms a channel extending in the interface, the channel having an inlet opening in a rear end of the tool head and an outlet opening in a front end or in the peripheral envelope surface of the tool head, and joining the assembled parts in a sintering operation to form the tool head.

Claims

1. A method for manufacturing a tool head of a rotary cutting tool, the tool head having a front end and a rear end between which a centre axis of rotation and a peripheral envelope surface extend, the method comprising: forming at least a first part and a second part from a powder composition, wherein the first part comprises has a first joining surface and wherein the second part comprises has a second joining surface, the first joining surface being configured to be brought into contact with the second joining surface, wherein the first part further comprises includes a first outer surface portion configured to form a first portion of the peripheral envelope surface of the tool head, and wherein the second part further comprises includes a second outer surface portion configured to form a second portion of the peripheral envelope surface of the tool head; forming at least one groove in the first joining surface and at least one corresponding groove in the second joining surface, wherein the at least one groove of the first joining surface is configured to face the at least one corresponding groove of the second joining surface when the first joining surface and the second joining surface are brought into contact; assembling the first and second parts into a shape of a tool head by bringing at least the first and second joining surfaces into contact to form an interface, so that at least one pair of the facing at least one and at least one corresponding grooves forms a channel extending in the interface, the channel having an inlet opening in the rear end of the tool head and an outlet opening in the front end and/or in the peripheral envelope surface of the tool head,; and joining the assembled first and second parts in a sintering operation to form the tool head.

2. The method according to claim 1, comprising wherein forming the first and second parts includes using one of a powder injection moulding, multiaxial pressing, uniaxial pressing and additive manufacturing process.

3. The method according to claim 1, wherein assembling the parts comprises assembling the parts in a non-sintered condition.

4. The method according to any one of the preceding claims claim 1, further comprising forming the first and second parts into an identical or substantially identical shape.

5. The method according to claim 1, comprising forming the first and second parts so that, when assembling the first and second parts, the first and second joining surfaces extend along the centre axis of the tool head.

6. The method according to claim 1, comprising forming the at least one groove as a curved groove.

7. The method according to claim 1, comprising forming at least a portion of the at least one groove with a smooth surface.

8. The method according to claim 7, wherein the smooth surface of the at least one portion of the at least one groove is a surface that has an arithmetic average roughness Ra3 m, when measured in any direction, wherein the smooth surface is selected from a direct pressed surface, a grinded surface, a polished surface and a surface created by means of powder injection moulding.

9. The method according to claim 1, wherein forming the at least one groove includes forming, in each of the first joining surface and the second joining surface, at least two grooves extending from a common depression so that, when assembling the first and second parts, at least two channels sharing a common inlet opening in the rear end of the tool head are formed in the interface.

10. The method according claim 1, further comprising providing the tool head with at least one cutting edge, wherein the at least one cutting edge is provided in adjacency to the outlet opening of the channel.

11. The method according to claim 9, comprising forming at least three parts, wherein a number of parts correspond to a number of cutting edges provided in the tool head.

12. The method according to claim 1, comprising providing the first and second joining surfaces with positioning means, wherein the positioning means of the first joining surface is configured to be engageable with the positioning means of the second joining surface, such that a relative position of the first and second parts during sintering is secured.

13. The method according to claim 1, wherein the powder composition is a hard metal powder composition or a cermet powder composition.

14. A tool head for use with a main body of a rotary cutting tool, the tool head comprising: a front end and a rear end between which a centre axis of rotation and a peripheral envelope surface extend, wherein the rear end is configured to be connected to the main body and wherein the front end is configured for cutting engagement with a workpiece at least one channel arranged for transporting liquid coolant to a cutting edge of the tool head, the at least one channel extending from an inlet opening in the rear end of the tool head to an outlet opening in the front end or in the peripheral envelope surface of the tool head, wherein the at least one channel is formed in at least one interface formed as a result of joining at least two parts to form the tool head, each part of the at least two parts being formed from a powder composition.

15. A rotary cutting tool comprising a main body and a tool head according to claim 13.

16. The rotary cutting tool according to claim 14, wherein the tool head has been joined to the main body by means of sintering.

17. The method according to claim 1, further comprising forming the at least one groove as a groove having a variable cross-sectional shape and/or size

18. The method according to claim 1, further comprising forming a major portion of the at least one groove with a smooth surface.

19. The method according to claim 1, further comprising forming the entire at least one groove with a smooth surface.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Embodiments of the invention will in the following be described by means of example with reference to the appended drawings, in which:

[0047] FIG. 1 is a flow chart illustrating a method according to an embodiment of the invention,

[0048] FIG. 2 is a perspective view of two parts for forming a tool head according to a first embodiment,

[0049] FIG. 3 is a side view of a part from FIG. 2,

[0050] FIG. 4 is a perspective view showing the parts in FIG. 2 assembled to form a tool head,

[0051] FIG. 5 is a front end view of the assembled parts from FIG. 4,

[0052] FIG. 6 is a cross sectional view showing a drilling tool comprising the tool head according to the first embodiment,

[0053] FIG. 7 is a perspective view of the drilling tool in FIG. 6,

[0054] FIG. 8 is a perspective view of two parts for forming a tool head according to a second embodiment,

[0055] FIG. 9 is a front end view showing the parts in FIG. 8 assembled to form a tool head,

[0056] FIG. 10 is a perspective view showing a drilling tool comprising the tool head according to the second embodiment,

[0057] FIG. 11 is a perspective view of two parts for forming a tool head according to a third embodiment,

[0058] FIG. 12 is a side view of a part from FIG. 11, and

[0059] FIG. 13 is a perspective view of a tool head according to the third embodiment.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

[0060] A method for forming a tool head according to an embodiment of the invention is schematically illustrated in the flow chart in FIG. 1. The method comprises the following steps A-C:

[0061] A: Forming a first part and a second part of a tool head from a powder composition comprising a binder phase in the form of a metal and a hard phase in the form of e.g. a carbide and/or a carbonitride and/or a nitride.

[0062] B: Assembling the first and second parts into a shape of a tool head.

[0063] C: Joining the assembled parts in a sintering operation to form the tool head.

[0064] Subsequent to step C, the formed tool head is machined to form e.g. cutting edges and clearance surfaces, and the tool head may also be provided with a coating. The final configurations of the tool heads, including e.g. chisel cutting edges and clearance surfaces, are not shown in the drawings.

[0065] Reference is now made to FIGS. 2-10, showing manufacturing of a tool head 1 according to a first embodiment (FIGS. 2-7) and a second embodiment (FIGS. 8-10). The same reference numbers are used for the same or corresponding features. The tool head 1 is intended to be permanently attached to a main body 2 to form a rotatory cutting tool 3, the tool head and the main body extending along a common centre axis C around which the tool 3 is rotatable in a direction R. The tool head 1 can also be an exchangeable head detachably attachable to the main body. In that case, the tool head is provided with a coupling interface.

[0066] Step A

[0067] First and second parts 4, 4 for a tool head 1 according to the first embodiment are shown in FIGS. 2-5, and first and second parts 4, 4 for a tool head according to a second embodiment of the invention are shown in FIGS. 8-9, respectively. The first part 4 and the second part 4 correspond to a first half and a second half of the tool head 1 to be formed, respectively. In the shown embodiments, the first part 4 and the second part 4 are identical.

[0068] As shown in FIGS. 2-3 and FIG. 8, respectively, the first part 4 comprises a first joining surface 5 and the second part 4, being identical, comprises an identical second joining surface, configured to be brought into contact with the first joining surface 5 in step B. The joining surfaces 5 extend in parallel to the centre axis C of the tool head 1 to be formed. The first part 4 further comprises a first outer surface portion 6 and the second part 4 comprises an identical second outer surface portion 6. Each outer surface portion 6, 6 is configured to form a first portion and a second portion, respectively, of a peripheral envelope surface 7 of the tool head 1.

[0069] In each part, a chip flute 8 is preformed, so that a cutting edge can later on be created in a grinding operation at an intersection 9 between the chip flute 8 and a front end 10 of the tool head 1. A gash 11 widening the chip flute 8 at the front end 10 of the tool head 1 is also provided.

[0070] In the first embodiment, four grooves 15 having an identical rounded shallow cross sectional shape are formed in each joining surface 5. The grooves 15 of the first joining surface 5 are configured to face the corresponding grooves of the second joining surface. Each groove 15 extends from a common central depression 16 formed at a rear end of the part 4, to a front end of the part 4. The grooves 15 are bent with a relatively large radius of curvature.

[0071] In the second embodiment, two bent grooves 17, 18 are formed in each joining surface 5. The grooves 17, 18 extend from a common depression 19. Of the two grooves 17, 18 formed in each joining surface 5, one groove 17 is relatively shallow and one groove 18 is relatively deep. The grooves 17, 18 are shaped so that a resulting channel formed from the two grooves 17, 18 obtains a cross-sectional shape of a so called Reuleaux triangle. This cross-sectional shape prevents rotational motion of coolant about a longitudinal axis of the channels. Such a rotational motion may otherwise result in a pressure drop within the channels.

[0072] In both embodiments, the grooves 15, 17, 18 have a smooth or substantially smooth surface, without transverse ridges or similar that would affect a flow of coolant through channels formed by the grooves.

[0073] In each joining surface 5, positioning means in the form of one recess 20 and one projection 21 are formed.

[0074] The parts 4 of the embodiments illustrated in FIGS. 2-5 and FIGS. 8-9, respectively, may be formed using powder injection moulding (PIM). Forming the parts using PIM comprises the following consecutive steps: [0075] i) Mixing of granulated composite powder, e.g. a cemented carbide powder composition comprising WC and Co, with a binder system, such as a polymer, to form a feedstock. [0076] ii) Performing injection moulding using the feedstock, comprising heating the feedstock to 100-240 C., forcing the feedstock into a mould formed as the part, cooling, and removing the obtained part from the mould. [0077] iii) Removing the binder system from the obtained part (debinding).

[0078] If necessary, irregularities may be removed from the parts prior to step B.

[0079] Step B

[0080] To assemble the parts 4, 4 into a shape of a tool head as shown in FIGS. 4-5 and FIG. 9, respectively, the first and second joining surfaces 5 are brought into contact to form an interface 22, so that each pair of facing grooves 15, 17, 18 forms a channel extending in the interface 22. In the first embodiment, four channels 23 are formed in the interface 22, and in the second embodiment, two channels 24 are formed. The channels extend from a common inlet opening 25 in a rear end 26 of the tool head 1 to outlet openings 27 in the front end 10 of the tool head 1. The positioning means 20, 21 ensure a correct alignment of the parts 4, 4 as the positioning means 20, 21 of the first joining surface 5 are brought into engagement with the positioning means of the second joining surface. The interface 22 extends in parallel with the centre axis C, so that the interface intersects a peripheral surface of the tool head 1 at the front end 10, at the rear end 26 and at the peripheral envelope surface 7.

[0081] The formed tool head 1 is rotationally symmetric about the centre axis C. The front end 10 of the tool head 1 will be configured for cutting engagement with a workpiece when the tool head 1 is rotated in the direction R about the centre axis C.

[0082] Step C

[0083] The sintering is performed at a temperature and time such that the binder phase, i.e. the metal of the composite powder, is in a liquid state during at least one minute. The temperature may e.g. be in the interval 1350-1500 C. during a time period of 10-120 minutes. The time and temperature used depend on the material composition, but also on the size and shape of the parts 4.

[0084] In an alternative embodiment, the individual parts 4 are sintered after step A, i.e. prior to assembling the parts. The sintered parts are thereafter assembled as previously described. The final sintering operation in which the parts are joined can in this case be shortened in order not to alter the material properties of the tool head. A time period of 10-20 minutes may, depending on size, composition and shape of the parts, be sufficient.

[0085] In the first and second embodiments, the sintered tool head 1 is joined to the main body 2 in another sintering operation to form the rotary cutting tool 3, here in the form of a drilling tool as shown in FIGS. 6-7 and FIG. 10, respectively. The main body 2 has in the shown embodiments been formed by extrusion followed by sintering. It comprises a central coolant duct 28 for supply of liquid coolant to the tool head 1. The common central inlet opening 25 in the rear end 26 of the tool head 1 is therefore connected to the central coolant duct 28 of the main body 2.

[0086] FIGS. 11-13 illustrate the manufacturing of an exchangeable tool head 30 according to a third embodiment of the invention. The tool head 30 is intended for use with a main body (not shown) of a drilling tool, wherein the main body is made of e.g. steel. A rear end 31 of the tool head 30 as shown is to be machined to form engagement means for securely attaching the tool head 30 to the main body (not shown). The tool head 30 is rotationally symmetric about a centre axis C around which the tool head is rotatable in a direction R.

[0087] For manufacturing of the tool head 30, a first part 34 and an identical second part 34 are formed in step A. However, in this embodiment, the parts 34, 34 are preferably formed from composite powder in a multiaxial pressing process instead of using PIM.

[0088] The first part 34 comprises a first joining surface 35 and the second part 34 comprises an identical second joining surface, configured to be brought into contact with the first joining surface 35 in step B. Like in the first and second embodiments, the first part 34 further comprises a first outer surface portion 36 and the second part 34 comprises an identical second outer surface portion 36. Each outer surface portion 36, 36 is configured to form a first portion and a second portion, respectively, of a peripheral envelope surface 37 of the tool head 30.

[0089] The joining surfaces 35 lack positioning means. Instead, the joining surfaces 35 are twisted around the centre axis C, so that the parts 34, 34 will automatically be aligned during assembly. In each joining surface 35, two front grooves 38 are formed in the pressing process, extending from a common depression 39 close to a rear end of the part 34 to a front end of the part 34. A common rear groove 40 extends from the common depression 39 to the rear end of the part 34. All grooves 38, 40 have a smooth or substantially smooth surface.

[0090] As the parts 34, 34 are assembled in step B, the front grooves 38 form two front channels 41 with circular cross sections extending in the interface between the assembled parts 34, 34. The front channels 41 have outlet openings in a front end 42 of the tool head 30, adjacent to cutting edges that will be formed later on in a grinding operation. The rear grooves 40 form a common rear channel (not shown) extending from an inlet opening in the rear end 31 of the tool head 30 to a central distribution chamber formed by the common depressions 39. Liquid coolant can thereby be supplied via the common rear channel, the distribution chamber and the front channels 41 to the outlet openings at the front end 42 of the tool head 30.

[0091] The assembled parts 34, 34 are joined in a sintering operation in step C as described above. After joining, the tool head 30 is machined to obtain its final shape (not shown), including cutting edges and engagement means for mounting the tool head 30 in a front seat of the main body, wherein the main body is configured to be mounted in e.g. a spindle of a machine.

[0092] The invention is of course not limited to the embodiments disclosed, but may be varied and modified within the scope of the following claims. For instance, the parts that are used to form the tool head do not need to be identical, and more than two parts may be used, such as three parts having joining surfaces extending along the centre axis. Furthermore, the rotary cutting tool may instead of a drilling tool be a milling tool, in which case the channels preferably have outlet openings provided in the peripheral envelope surface of the tool head, close to cutting edges of the milling tool.