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.

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.