CUTTING PLATE AND METHOD AND COMPRESSION MOLD FOR PRODUCING A GREEN BODY OF THE CUTTING PLATE

Abstract

A compression tool, a cutting plate and a method of producing a cutting plate by multiaxial pressing a powder mixture of a hard metal component and a binder to form a green body is provided. After pressing, the body has two parallel main surfaces and a peripheral edge surface extending between and connecting the main surfaces. The main surfaces include depressions, such that cutting edges are formed at the intersection of the bottom of the depressions and at least a part of the edge surface. A heading tool includes a main punch and an independently moveable form punch. In a first pressing step, the form punch is moved towards the powder mixture to form a preliminarily compressed portion. In a second step, the main punch and the form punch are both moved towards a final position to provide the green body with its final dimensions including the depressions.

Claims

1. A method of producing a cutting plate made of hard metal, in particular of sintered carbide, comprising: multiaxial pressing a powder mixture of a hard metal component and a binder to form a green body; and sintering the green body, which after pressing includes two substantially parallel main surfaces and a peripheral edge surface extending between the main surfaces at a periphery thereof and connecting the same, the two, parallel main surfaces each including depressions extending at least partly to the peripheral edge surface such that cutting edges are formed at an intersection of a bottom of said depressions and at least a part of said edge surface, wherein the powder mixture is supplied to a compression mold having a cavity, which is defined by side punches moveable along at least a first direction for forming said edge surfaces and at least one heading punch moveable substantially perpendicular to the first direction for compacting the powder mixture to form a cutting plate green body, wherein a heading tool is used, which is moveable perpendicular to and towards said main surfaces, the heading tool including two parts, one of the parts being a main punch and the other part being an independently moveable form punch, wherein the pressing step includes a first pressing step wherein the form punch is moved towards the powder mixture to form a preliminarily compressed portion of the green body adjacent the peripheral edge surface and including an area designated to become an area of a minimal final thickness of the green body, and a second pressing step wherein the main punch and the form punch are both moved towards a final position to provide the green body with its final dimensions of the parallel main surfaces including the depressions.

2. The method of claim 1, wherein each of the side punches is closed before supplying the powder mixture.

3. The method according to claim 1, characterized in that the wherein a preliminary pressing and a final compression is performed by two identical heading tools which are moved simultaneously towards two oppositely arranged main surfaces of the green body, each of said two identical heading tools including at least one main punch and form punch.

4. The method according to claim 1, wherein the pressing to the final dimensions by means of the main punch and the form punch occurs under control of a position of the punches to provide a similar amount of compaction and/or surface pressure in an area of a transition from the form punch to the main punch.

5. The method according to claim 1, wherein a portion of at least two depressions oppositely arranged on either side of the green body is pressed to a minimum thickness between the bottom of said depressions corresponding to less than 20% of the maximum cutting plate thickness (D) measured between the main surfaces outside of any depressions.

6. A compression tool for producing plate shaped green bodies by multiaxial pressing, the green bodies each having two substantially parallel main surfaces and a peripheral edge surface connecting the main surfaces, each green body being comprised of a powder mixture of hard metal and a binder, wherein the compression tool defines a cavity for receiving the powder mixture and includes at least two side punches moveable towards each other, front faces of each said side punches being arranged to form at least a part of the edge surface of the green body, wherein one the side punches may be replaced by a fixed side wall of a die, wherein there are provided two heading tools on two remaining opposite sides of the cavity, which are moveable towards each other along a common axis and perpendicular to a plane defined by the main surfaces, each of said heading tools including at least two parts, a main punch and an independently moveable form punch, a cross-section of which extends to the front face of at least one side punch, wherein a front face of the form punch is moveable towards the cavity beyond a front face of the main punch in order to form a depression such as a web thinning of the green body.

7. The compression tool according to claim 6, wherein the front face of the form punch, which in a plan view towards the pressing surface thereof amounts to less than ⅓ the front face of the main punch.

8. The compression tool according to claim 6, wherein each heading tool includes two form punches arranged at oppositely disposed edge faces.

9. The compression tool according to claim 6, wherein for each of the main and form punches there are provided independent means for determining and controlling the individual axial position of the punches and/or means for determining the pressing force and specific surface pressure, respectively.

10. The compression tool according to claim 6, wherein the mutually facing heading tools are arranged such that the front faces of the opposite form punches are at least partially overlapping each other when seen along the common axis.

11. The compression tool according to claim 6, wherein the front faces of the form punches in a closed condition of the cavity have a minimal distance of less than 1 mm.

12. A cutting plate for drilling or milling, said cutting plate being produced from a powder mixture of hard metal and a binder by a compression tool and by the method of claim 1 to form a green body, the green bodies each having two substantially parallel main surfaces, the compression tool including a cavity arranged to receive the powder mixture, and at least two side punches moveable towards each other, front faces of each said side punches being arranged to form at least a part of an edge surface of the green body, wherein one the side punches may be replaced by a fixed side wall of a die, wherein there are provided two heading tools on two remaining opposite sides of the cavity, which are moveable towards each other along a common axis and perpendicular to a plane defined by the main surfaces, each of the heading tools including at least two parts, a main punch and an independently moveable form punch, a cross-section of which extends to the front face of at least one side punch, wherein a front face of the form punch is moveable towards the cavity beyond a front face of the main punch in order to form a depression, such as a web thinning of the green body, and the method including sintering the corresponding green body which after pressing includes the two substantially parallel main surfaces, the peripheral edge surface extending between the main surfaces at a periphery thereof and connecting the same, which main surfaces include depressions extending at least partly to the edge surface such that cutting edges are formed at the intersection of the bottom of said depressions and at least a part of said edge surface, wherein a maximum depth of at least one depression is more than 80% of half of a cutting plate thickness defined as the distance between the two parallel main surfaces.

13. The cutting plate according to claim 12, wherein the thickness of the plate is less than one half of the maximum diameter of the plate as measured through a center of gravity and parallel to the planes defined by the main surfaces.

14. The cutting plate according to claim 12, wherein the cutting plate is a double sided plate including cutting edges at a transition of oppositely arranged edge surfaces to the main surfaces.

15. The cutting plate according to claim 12, wherein the depressions are provided at the bottom thereof with chip-breaking and/or chip-forming projections and/or recesses as produced only by the pressing of the powder mixture into the green body.

16. The cutting plate according to claim 15, wherein a ratio of the minimum distance between the bottom of depressions on opposite main surfaces, in particular in the area of the web thinnings, when compared to the maximum plate thickness is less than 1/10.

17. The cutting plate according to claim 12, wherein the bottom of at least one depression or web thinning includes chip breaking and/or chip forming projections and/or recesses, individual projections or recesses within the bottom of the depressions having a shape of knobs and/or dimples and/or of grooves and/or ribs.

18. The cutting plate according to claim 15, wherein the individual projections and/or recesses at the bottom of any depression do not exceed a dimension of more than 2 mm in at least one direction.

19. The cutting plate according to claim 12, wherein the cutting plate is symmetric with respect to rotation by 180° about a central axis extending in an intermediate plane between the main surfaces and parallel thereto through the center of gravity and the center of a dead end at a tip of the cutting plate.

20. The cutting plate according to claim 19, wherein a thinnest area of the cutting plate is an area of the dead end.

21. The cutting plate according to claim 12, wherein at least one depression on either side is a web thinning, wherein the web thinnings on opposite sides of the main surfaces are arranged such that a lowermost point of said at least one depression is approaching a same position on the edge surface.

Description

[0060] Further features and advantages of the cutting plates and the corresponding methods and devices for their production may become more apparent from the following description of preferred embodiments and the associated figures.

[0061] FIG. 1A,B show a planar side view and a front view, respectively, on a cutting plate according to the present invention, designed as a drilling plate having an axis of symmetry.

[0062] FIG. 2 shows a cross section along line II-II in FIG. 3, of a compression tool defining a cavity with a section parallel to the main surfaces of the cutting plate formed in such cavities.

[0063] FIG. 3 shows a cross section corresponding to the line III-III in FIG. 2.

[0064] FIG. 4 shows a cross section through the compression tool similar as FIG. 2, but without a cutting plate.

[0065] FIG. 5 shows another embodiment of a cutting plate according to the present invention.

[0066] FIG. 6 shows a double-sided cutting plate according to the present invention.

[0067] In FIG. 1A, there is shown a plan view on a cutting plate 10 on one of the main surfaces 1a, 1b. In the plan view, the cutting plate occurs as a polygonal body with a symmetry axis 50 extending through the center of gravity and the dead end 7 at the tip of the cutting plate in an intermediate plane 40 parallel to the main surfaces 1a, 1b and shown as a dashed dotted line.

[0068] As visible in FIG. 1B, the cutting plate has two generally planar and parallel main surfaces 1a, 1b, wherein both of these main surfaces are comprising depressions 4a, b and web thinnings 5a, b respectively, adjacent the edge surface portions 3a, 3b. The complete edge surface connecting the top and bottom surfaces 1a, 1b and surrounding the cutting plate and including the edge surface portions 3a, 3b is denoted by reference numeral 3. The depression 4a is formed as a chip groove extending along a cutting edge 6a which is formed and defined by the intersection between the bottom of the chip groove 4a and the edge surface portion 3a. A similar chip groove 4b is provided on the opposite side 1b of the cutting plate and the bottom of this chip groove 4b forms a cutting edge 6b at the intersection with the edge surface 3b. The edge surface portions 3a, 3b are effectively forming relief surfaces and therefore, these edge surface portions do not extend exactly perpendicular to the main surfaces 1a, 1b but are slightly angled such as to provide a sufficient relief angle behind the cutting edges 6a, 6b.

[0069] Depressions 4a, 4b are forming chip grooves adjoining the radial outer portions of cutting edges 6a, 6b. The depressions 5a, 5b are formed as web thinnings adjoining the radial inner portions of cutting edges 6a, 6b, i.e. they are approaching each other from opposite sides 1a, 1b to reduce the length of the dead end 7 which is formed as a crest at the tip of the cutting plate, which crest is formed by the intersection of the relief surfaces 3a, 3b. As will be seen from FIG. 1B, the cutting plate 10 is symmetric with respect to a rotation by 180° about an axis 50 extending through a center of gravity of the cutting plate and the centre of the dead end 7, i.e. within the middle plane 40 which is an imaginary plane in the middle between the planes defined by the main surfaces 1a and 1b, respectively.

[0070] The cutting plate 10 may have a central clamping hole 8 with an axis extending at an angle equal to or deviating from 90 with respect to the main surfaces 1a, 1b in particular at an angle of 50 to 80°, such as about 60° as shown by dashed lines in FIG. 1B. However, even without a central clamping hole 8, the cutting plate 10 may be clamped by the walls of a slot provided at the front end of a corresponding tool shaft.

[0071] The compression tool 20 is shown and described in connection with FIGS. 2 to 4.

[0072] FIG. 2 is a cross-section through the cavity of a compression tool 20 for pressing the corresponding green body 10, with a section along lines II-II in FIG. 3. FIG. 2 also shows a planar side view on the cutting plate 10 after pressing, corresponding to FIG. 1A.

[0073] FIG. 3 is a cross section according to section line III-Ill in FIG. 2 including a cutting plate received in the cavity of the tool.

[0074] FIG. 4 is a similar cross section through a compression tool as FIG. 2, but without a cutting plate located therein, such that the front faces of the main punch and form punch of the lower heading are visible.

[0075] The cavity 30 shown is formed by a die insert 25a, inserted in a slot of an inner surface of a die 25, two side punches 21, 22 movable along arrows A, and an upper and a lower heading each being comprised of a main punch 23a, 23b, respectively, and a form punches 24a, 24b, respectively. Before filling the cavity 30, the two side punches 21, 22 are closed, i.e. they are moved towards each other until they abut each other and/or the die insert 25a with their oppositely arranged faces 21a, 22a.

[0076] As shown in FIG. 3, the upper and lower form punches 24a,b are then moved along arrows B perpendicular to the arrows A (shown in FIG. 2), wherein the periphery of the combined punches 23a,b, 24a,b fit into the cavity space formed between the side punches 21, 22 and die insert 25a.

[0077] The cavity 30 is then filled with a powder mixture of a hard metal component, such as WC and a binder, such as cobalt. Thereupon, the upper tooling head will be moved downward towards the cavity 30 until there is a slight contact with the upper surface of the powder mixture by the form punch and optionally also by the main punch. Before contacting the powder mixture, the form punch 24a may be flush with or partly projecting beyond the front surface of the main punch 23a. In the next step, both form punches 24a, 24b will be moved towards each other along the arrows B visible in FIG. 3 until a certain amount of preliminary compression is obtained between the two form punches 24a, 24b, adjacent the front faces of one or both of side punches 21, 22, because the form punches are designed and provided for forming the web thinnings 5a, b visible in FIG. 1B and extend to the edge surfaces 3a, 3b. The amount of such preliminary pressing, i. e. the final position of the form punches 24a,b reached in the preliminary pressing step and optionally or alternatively the corresponding pressing force required therefor has to be determined by experiments and/or simulations since it depends on the composition of the powder mixture and also on the ratio between the thinnest and thickest portions of the cutting plate.

[0078] In the next step, also the main punches 23a, 23b are moved towards each other in order to compress the powder mixture along the axis defined by the arrows B. Before the final amount of compression is reached, both pairs of punches, namely the main punch 23a and the form punch 24a as well as the lower main punch 23b and the lower form punch 24b are moved in unison towards the oppositely arranged tool, until a desired position and compaction is reached. Optionally also the forces acting on the punches 23a,b and 24a,b may be considered and adapted such that a similar pressure acts on the green body along the whole upper and lower surface 1a and 1b including the depressions 4a, 4b and web thinnings 5a, 5b.

[0079] A typical compression cycle takes between 1 and 10 seconds, and thereafter the upper heading and the side punches may be removed, whereupon the green body can be ejected from the cavity, for instance by moving the lower tool 23b, 24b upward.

[0080] A portion 14 of the main punches 23a, 23b slightly projecting over the front face 11 and forming the chip grooves 4a, 4b on either side of the cutting plate is visible in FIG. 4. For deep chip grooves 4, the portion forming 14 might also be provided on the front face of the form punch 24a, b.

[0081] While FIG. 1A appears to show a border line 4c between the chip groove 4a and the web thinning 5a, there may in general be just a smooth transition between the respective depressions 4a, 5a. According to a standard definition for twist drills, the web thinning corresponds to any removed portion or recess within a central core which is not affected by any chip groove over the length of a cutting portion which in turn is defined by the axial length of the chip grooves. In FIG. 1B, a corresponding circle K is shown by a dashed line having a diameter corresponding to the maximum thickness of the cutting plate. Accordingly, removed material within a cylinder defined by the dashed circle K may be identified as a web thinning 5a, 5b.

[0082] Still, the cross-section of the form punch 24a, 24b may extend beyond the dashed circle K to the periphery of the depression 5a, 5b including the line 4c in the upper part of FIG. 1A, while a projection 14 extending from the otherwise planar front surfaces 11 of the main punches 23a, 23b may be provided for the generation of the chip grooves 4a, 4b and again be delimited by line 4c.

[0083] FIG. 5 shows another embodiment of the present invention including some additional modifications. Reference numerals in FIG. 5 are modified with respect to the previously described embodiment by adding just 100 for the respective equivalent features. For the ease of description, the same reference numerals are used for the identical features and elements on either side of the cutting plate 100.

[0084] Again, the cutting plate 100 comprises two main surfaces 101, (wherein only one of them is visible) and recesses or depressions 104, 105 from said main surfaces 101, wherein the depressions 104 are indicated and act as chip grooves or chip flutes, while a recess 105 adjacent the dead end 107 is a web thinning because for the generation of this web thinning, material has to be removed from the core of the cutting plate 100 which otherwise is not affected by depressions like the chip grooves 104.

[0085] In addition, relief surfaces adjacent cutting edges 106 are formed as relatively narrow lands 103 followed by relief recesses 113 axially retracted with respect to the lands 103 adjacent the respective cutting edges 106.

[0086] For the production of such a cutting plate, the front faces of the side punches or a single side punch may be shaped such as to form both, lands adjacent the cutting edges 106, which are forming relief surfaces 103, as well as the relief recesses 113. The dead end 107 is much shorter than a corresponding crest which might extend over the whole width of the cutting plate if no web thinning 105 would be provided. The web thinning 105 further comprises grooves 112 having an arc shaped bottom and ridges 111 there between extending from the respective main surfaces 101 to the cutting edges 106, so that the cutting edge 106 has a wavy shape adjacent to the web thinning and the dead end.

[0087] Also the radial outer portion of the cutting edges 106 is slightly curved due to the curved bottom of the respective chip groove 104 intersecting with the relief surfaces 103. Accordingly, the cutting edges 106 are formed by the transition from the depressions, more precisely the chip groove 104 and web thinnings 105, to a relief surface formed by the lands 103.

[0088] In addition, chip breaking structures like the knobs 114 and ribs 115 may be provided at the bottom of the chip grooves 104 and also the grooves 112 and ridges 111 forming the bottom of the web thinning 105 are acting as chip formers and chip breakers.

[0089] With the embodiment shown in FIG. 5, the actual length of the dead end 107 is only about 3% to 8% of the thickness D of the cutting plate. Without such web thinning the length of the dead end 107 would be at least the distance between the parallel main surfaces 101.

[0090] FIG. 6 shows another embodiment of the present invention which is configured as a double-sided cutting plate, which is designated by reference numeral 210.

[0091] The last two digits of the reference numerals used in FIG. 6 are similar or the same as those used for the previous description of FIGS. 1 to 5, wherein just a leading number 2 is used as a prefix.

[0092] In agreement with the previous embodiment, the cutting plate 210 is comprised of a body having two parallel top and bottom surfaces, wherein only the top surface 201a is visible in FIG. 6, while the opposite side has exactly the same appearance if the cutting plate 210 is turned around by 180°. Accordingly, it is sufficient to describe the cutting plate 210 only by the view shown in FIG. 6. The double-sided cutting plate 210 comprises two tips having short dead ends 207a and 207b, respectively, on oppositely arranged edge surfaces, more particular at the transition from an inner end of a cutting edge 206a to a cutting edge 206b on the opposite main surface. Web thinnings 205a and 205c form, together with further web thinnings on the opposite main surface (not visible), the inner portions of cutting edges 206a, 206b, 206c, 206d at the transition to the respective edge surfaces 203b, 203d (the remaining edge surface portions are not visible) and leave a dead end 207a, 207b connecting the inner ends of the respective cutting edges. The main surface 201a is comprised of a central portion and two outer portions, wherein slight concave depressions 211 are arranged between the planar central portion and each of the planar outer portions of the main surface 201a. Two mounting holes 208a, 208b extend from the main surface 201a to the opposite main surface (not visible), wherein a major part of the mounting holes extends through the bottom of the slightly concave depressions 211. Chip grooves 204a, c are visible on diagonally opposite sides of the main surface 201a.

[0093] The cutting plate 210 is symmetrical with regard to a rotation by 180° about either a horizontal axis extending through the dead ends 207a, 207b, a vertical axis extending through the center of the mounting holes 208a, 208b and also about a central axis perpendicular to the main surface 201a, extending through the plate at the position where the other two axes of symmetry cross each other.

[0094] When inserted within a slot at the front end of a corresponding cutting plate holder to be used as a drill, one of the tips or dead ends 207a, 207b is inactive while the other tip is projecting in the forward direction from the slot and is used as the tip of a drill. When the cutting edges 206a, 206b of the corresponding tip 207a are worn out, the cutting plate may be dismounted and turned around and again mounted within the slot of the cutting plate holder such that the cutting tip 207b is projecting in the forward direction and cutting edges 206c and 206d are becoming the active cutting edges.

[0095] The cutting plate is mounted within a slot at the front end of a tool holder, wherein mounting screws are guided through holes provided in the wall of a tool holder limiting the slot and extend through the mounting holes 208a, 208b into threaded holes provided in the wall of the cutting plate holder limiting the other side of the slot.

[0096] For the purpose of original disclosure it is to be noted that any features which may be gathered by a skilled person from the present description, the drawings and the claims, even if only described in connection with particular further features, may be combined individually as well as in arbitrary combinations with any other of the features or groups of features disclosed herein, unless this is explicitly excluded or technical conditions would render such combinations impossible or senseless. The comprehensive, explicit discussion of any combinations of features which might be thought of is dispensed with just for the sake of brevity and legibility of the description and claims.