Patent Publication Number: US-8119062-B2

Title: Method and apparatus for manufacturing a cutting insert

Description:
RELATED APPLICATIONS 
     This is a Continuation of U.S. patent application Ser. No. 12/489,980, filed Jun. 23, 2009, now U.S. Pat. No. 7,731,488, which is a Divisional of U.S. patent application Ser. No. 11/321,917, filed Dec. 29, 2005, now U.S. Pat. No. 7,560,068. The contents of the aforementioned applications are incorporated by reference in their entirety. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to a method and apparatus for manufacturing pre-sintered cutting insert green bodies, to be subsequently sintered into cutting inserts. 
     BACKGROUND OF THE INVENTION 
     Fabrication of cutting inserts from sinterable powders, i.e., metallurgical, cermets or ceramics powders, comprises compaction of the sinterable powder, with or without a fugitive binder, into a pre-sintered green body, and subsequent sintering of the green body to produce a cutting insert. Compaction takes place under high pressures obtained through large opposing forces generated by top and bottom punches urged towards a die cavity formed in a die containing the sinterable powder, as is well known in the art. However, while parts having undercut elements may generally be pressed, the undercut elements inhibit release and subsequent extraction of the compacted green body from the die cavity. 
     SUMMARY OF THE INVENTION 
     In accordance with the present invention, there is preferably provided a method for manufacturing a cutting insert green body, the method comprising the steps of:
         (i) Providing top and bottom dies and top and bottom punches associated therewith and slidably reciprocable relative thereto. Each die comprises opposing die abutment and die mounting faces and a die inner peripheral surface extending therebetween. Each die inner peripheral surface comprises an inner first peripheral surface extending from the die abutment face, an inner second peripheral surface extending from the inner first peripheral surface and converging inwardly to a die inner edge, and an inner third peripheral surface extending from the die inner edge to the die mounting face and forming a punch tunnel. Each punch comprises opposing punch pressing and punch mounting faces, with a punch peripheral surface extending therebetween and forming a punch edge at an intersection of the punch peripheral surface and the punch pressing face.   (ii) Positioning the top and bottom dies in a closed position, in which respective die abutment faces abut, and respective inner first and second peripheral surfaces form a die cavity. The bottom punch is located in the punch tunnel of the bottom die, and the top punch is external to the punch tunnel of the top die.   (iii) Filling the die cavity with a pre-determined amount of sinterable powder.   (iv) Moving the top punch into the punch tunnel of the top die.   (v) Compacting the sinterable powder by urging the punches through the respective punch tunnels towards each other to a compaction position. In the compaction position, the punch edge of the top punch and the die inner edge of the top die are contiguous, and the punch edge of the bottom punch and the die inner edge of the bottom die are contiguous, thereby forming the green body.   (vi) Moving the top die and punch away from the bottom die and punch to an open position, thereby enabling removal of the green body.       

     Preferably, the green body comprises opposing green body end faces and a peripheral side surface extending therebetween. The green body end faces are formed by the punch pressing faces. The green body peripheral surface is formed by the die inner first and second peripheral surfaces of the top and bottom dies. 
     Further preferably, the green body comprises top and bottom green body edges formed at intersections of the top and bottom green body end faces with the green body peripheral surface, respectively. Associated contiguous top and bottom punch edges and top and bottom die inner edges form top and bottom common die cavity edges, respectively. The top and bottom green body edges are formed at the top and bottom common die cavity edges. 
     Yet further preferably, the green body comprises a median plane M extending between the top and bottom green body end faces. In the compaction position, the abutting top and bottom die abutment faces coincide with the green body median plane M. 
     If desired, the green body peripheral surface comprises top and bottom green body relief surfaces adjacent the green body edges. Each green body relief surface forms a relief angle ρ with the green body median plane M. The relief angle ρ is obtuse at least a portion of each green body relief surface. 
     If further desired, the relief surfaces are formed by the inner second peripheral surfaces. 
     Typically, the green body end faces comprise rake surfaces adjacent the green body edges. Adjacent rake and relief surfaces form a wedge having a non-obtuse wedge angle ω. 
     Generally, the wedge angle ω is acute at least along a portion of the wedge. 
     In accordance with another preferred embodiment, the green body may comprise a longitudinal through-hole extending between the green body end faces. The longitudinal through-hole is formed by a longitudinal rod extending between the punch pressing faces through the die cavity. 
     If desired, the longitudinal rod comprises slidably reciprocable top and bottom longitudinal pins disposed in top and bottom punch pin through-bores formed in the top and bottom punches. 
     Alternatively, the green body may comprise a lateral through-hole extending between two opposing green body major side surfaces of the green body peripheral surface. The lateral through-hole is formed by a lateral rod extending through the die cavity between opposing inner side portions of the inner first peripheral surfaces of the top and bottom dies. 
     Preferably, the lateral rod comprises opposing slidably reciprocable lateral pins disposed in top and bottom die pin channels of the top and bottom dies. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a better understanding of the present invention and to show how the same may be carried out in practice, reference will now be made to the accompanying drawings, in which: 
         FIG. 1  is a perspective view of a green body manufactured in accordance with the method of the present invention; 
         FIG. 2  is an end view of the green body shown in  FIG. 1 ; 
         FIG. 3  is a major side view of the green body shown in  FIG. 1   
         FIG. 4  is a cross-sectional view of the green body shown in  FIG. 1 , taken along the line IV-IV in  FIG. 3 ; 
         FIG. 5  is a schematic cross-section of a tool-set in accordance with the present invention, in a compaction position; 
         FIG. 6  is the schematic cross section of the tool-set shown in  FIG. 5 , in a closed position; 
         FIG. 7  is the schematic cross section of the tool-set shown in  FIG. 5 , in a filling position; 
         FIG. 8  is the schematic cross section of the tool-set shown in  FIG. 5 , in an open position; 
         FIG. 9  is a schematic cross section of a longitudinal through-hole tool-set in the compaction position; 
         FIG. 10  is a schematic cross section of a lateral through-hole tool-set in the compaction position; 
         FIG. 11  is an exploded perspective view of the tool-set shown in  FIG. 5 ; 
         FIG. 12  is an exploded perspective view of the longitudinal through-hole tool-set shown in  FIG. 9 ; 
         FIG. 13  is an exploded perspective view of the lateral through-hole tool-set shown in  FIG. 10 ; 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Attention is drawn to  FIGS. 1 to 4 . A pre-sintered green body  20  is preferably formed by compaction of a sinterable powder consisting of metallurgical, ceramic or cermet powder, and a binder. The green body  20  is generally rectangular in an end view and has identical, opposing (i.e., facing in opposite directions) top and bottom green body end faces  22 ′,  22 ″. In the present description, when following a reference numeral, a single prime (′) denotes a feature associated with the top side of the green body cutting insert, while a double prime (″) denotes a feature associated with the bottom side of the green body cutting insert. Each green body end face  22 ′,  22 ″ has a 180° rotational symmetry about an axis of symmetry S which passes through the two green body end faces  22 ′,  22 ″. A peripheral green body side surface  24  extends between the two green body end faces  22 ′,  22 ″. The peripheral green body side surface  24  comprises two opposing, identical major side faces  24 J of a general parallelogram shape; two opposing, identical minor side faces  24 N, also generally parallelogram in shape; and four curved corner surfaces  24 C. Each corner surface  24 C extends between a major side face  24 J and an adjacent minor side face  24 N. 
     Major and minor green body axes J, N are defined as being perpendicular to each other and to the axis of symmetry S. The major axis J extends through the major side faces  24 J and the minor axis N extends through the minor side faces  24 N. Each major side face  24 J has a 180° rotational symmetry about the major axis J, and each minor side face  24 N has a 180° rotational symmetry about the minor axis N. The major and minor axes J, N define a median plane M extending between the top and bottom green body end faces  22 ′,  22 ″. 
     Intersections of each green body end face  22 ′,  22 ″ and the peripheral green body side surface  24  define top and bottom green body edges  26 ′,  26 ″, respectively. Following sintering, the green body  20  becomes an indexable and reversible cutting insert and at least a portion of each of the top and bottom green body edges  26 ′,  26 ″ becomes a cutting edge. 
     Each green body edge  26 ′,  26 ″ comprises two major edges  26 J′,  26 J″ formed by the intersection of the major side faces  24 J and each of the top and bottom end faces  22 ′,  22 ″; two minor edges  26 N′,  26 N″ formed by the intersection of the minor side faces  24 N and each of the top and bottom end faces  22 ′,  22 ″; and four corner edges  26 C′,  26 C″ formed by the intersection of the corner surfaces  24 C and each of the top and bottom end faces  22 ′,  22 ″. 
     The peripheral green body side surface  24  has top and bottom relief surfaces  28 ′,  28 ″ adjacent the top and bottom green body edges  26 ′,  26 ″, respectively. Each major side face  24 J has two major relief surfaces  28 J′,  28 J″ adjacent the major edges  26 J′,  26 J″; each minor side faces  24 N has two minor relief surfaces  28 N′,  28 N″ adjacent the minor edges  26 N′,  26 N″; and each corner surface  24 C has two corner relief surfaces  28 C′,  28 C″ extending along the corner edges  26 C′,  26 C″. A central peripheral surface  30  extends between the top and bottom relief surfaces  28 ′,  28 ″. Each major side face  24 J has a major central surfaces  30 J extending between the top and bottom major relief surfaces  28 J′,  28 J″; each minor side face  24 N has a minor central surfaces  30 N extending between the top and bottom minor relief surfaces  28 N′,  28 N″; and each corner surface  24 C has a corner central surface  30 C extending between the top and bottom corner relief surfaces  28 C′,  28 C″. In a preferred embodiment, the green body median plane M intersects the central peripheral surface  30 . 
     Each of the major relief surfaces  28 J′,  28 J″ forms a major relief angle ρJ with the green body median plane M. In accordance with the preferred embodiment, the major relief angles ρJ are obtuse, and therefor one of the top and bottom major relief surfaces  28 J′,  28 J″ constitutes an undercut element of the green body  20 . It is understood that, similarly, the minor and corner relief surfaces  28 N′,  28 N″,  28 C′,  28 C″ form minor and corner relief angles with the green body median plane M. 
     As best seen in  FIG. 2 , the green body top end face  22 ′ has a top land  32 ′ that extends parallel to, and inwardly from the top green body edge  26 ′ towards the axis of symmetry S. The top land  32 ′ comprises a pair of top major lands  32 J′ formed along the top major edges  26 J′, a pair of top minor lands  32 N′ formed along the top minor edges  26 N′ and four top corner lands  32 C′ formed along the top corner edges  26 C′. A Top rake surface  34 ′ extends inwardly from the top land  32 ′ towards the axis of symmetry S while sloping towards the median plane M. The top rake surface  34 ′ comprises a pair of top major rake surfaces  34 J′ adjacent the top major lands  32 J′, a pair of top minor rake surfaces  34 N′ adjacent the top minor lands  32 N′, and four top corner rake surfaces  34 C′ adjacent the top corner lands  32 C′. It is understood that the green body top end face  22 ′, and in particular its top rake surface  32 ′, may comprise various geometries and features, such as chip breakers. It is further understood that the green body bottom end face  22 ″ has a land and rake surface structure similar to that of the green body top end face  22 ′. 
     As seen in  FIG. 4 , adjacent top major relief surface  28 J′ and top major rake surface  34 J′ form a top major wedge  36 J′ having a top major wedge angle ωJ′. It is understood that a top minor wedge having a top minor wedge angle is formed between adjacent top minor relief surface  28 N′ and top minor rake surface  34 N′ while a top corner wedge  36 C′ having a top corner wedge angle is formed between each adjacent top corner relief surface  28 C′ and top corner rake surface  34 C′. In accordance with a preferred embodiment, the top major wedge angle ωJ′, the top minor wedge angle and the top corner wedge angle are all acute. It is understood that the green body bottom end face  22  also has such wedges and wedge angles. 
     Attention is now drawn to  FIGS. 5 and 11 . The green body  20  is compacted in a tool-set  38  having top and bottom dies  40 ′,  40 ″. Each die  40 ′,  40 ″ comprises a die mounting face  42 ′,  42 ″ used to attach the die  40 ′,  40 ″ to a press (not shown) opposing a die abutment face  44 ′,  44 ″ and die outer and inner peripheral surfaces  46 ′,  46 ″,  48 ′,  48 ″ extending therebetween. Each die inner peripheral surface  48 ′,  48 ″ comprises an inner first peripheral surface  50 ′,  50 ″ extending from, and transversely to, the die abutment face  44 ′,  44 ″; an inner second peripheral surface  52 ′,  52 ″ extending from the inner first peripheral surface  50 ′,  50 ″ and converging inwardly to a die inner edge  54 ′,  54 ″; and an inner third peripheral surface  56 ′,  56 ″ extending from the die inner edge  54 ′,  54 ″ to the die mounting face  42 ′,  42 ″. The inner third peripheral surface  56 ′,  56 ″ forms a punch tunnel  58 ′,  58 ″. 
     Top and bottom punches  60 ′,  60 ″ are associated with the top and bottom dies  40 ′,  40 ″, respectively, and adapted to be slidably reciprocable in relation thereto, through the respective punch tunnels  58 ′,  58 ″. Thus, each punch can slide in either direction within its punch tunnel. Each punch comprises a punch mounting face  62 ′,  62 ″, used to attach the punch to the press, opposing a punch pressing face  64 ′,  64 ″ and a punch peripheral surface  66 ′,  66 ″ extending therebetween, forming a punch edge  68 ′,  68 ″ at the intersection thereof with the punch pressing face  64 ′,  64 ″. Each die or punch  40 ′,  40 ″,  60 ′,  60 ″ is capable of independent reciprocating motion relative to each of the other top and bottom dies or punches  40 ′,  40 ″,  60 ′,  60 ″. 
     Attention is additionally drawn to  FIGS. 6 to 8 . To manufacture the green body  20 , the tool-set  38  is cycled through closing, filling, compaction and opening steps. In the closing step ( FIG. 6 ), the tool-set  38  is brought to a closed position, in which the die abutment faces  44 ′,  44 ″ abut, and the first and second inner die peripheral surfaces  50 ′,  50 ″,  52 ′,  52 ″, form a die cavity  70  extending between the top and bottom die inner edges  54 ′,  54 ″. The bottom punch  60 ″ is located in the punch tunnel  58 ″ of the bottom die  40 ″, with its punch edge  68 ″ located below the die inner edge  54 ″, while the top punch  60 ′ is positioned outside the punch tunnel  58 ′ of the top die  40 ′. 
     In the filling step ( FIG. 7 ), the die cavity  70  is filled through the punch tunnel  58 ′ of the top die  40 ′ with a pre-determined amount of sinterable powder  72 . Subsequent to filling the die cavity  70 , the top punch  60 ′ is lowered into the punch tunnel  58 ′ of the top die  40 ′, thereby sealing the sinterable powder  72  in the die cavity  70 . 
     In the compaction step, the sinterable powder  72  is compacted to form the green body  20 , as shown in  FIG. 5 , as the tool-set  38  is brought to a compaction position, by urging the top and bottom punches  60 ′,  60 ″ towards each other, until each punch edge  68 ′,  68 ″ and its associated die inner edge  54 ′,  54 ″ are contiguous, thereby forming top and bottom common die cavity edges  74 ′,  74 ″. In accordance with the preferred embodiment, during the compaction step, the green body end faces  22 ′,  22 ″ are formed by the punch pressing faces  64 ′,  64 ″. Each green body edge  26 ′,  26 ″ is formed at the common die cavity edges  74 ′,  74 ″. The green body relief surface  28 ′,  28 ″ are formed by the inner second peripheral surfaces  52 ′,  52 ″, and the green body top and bottom central surfaces  30 ′,  30 ″ are formed by the inner first peripheral surfaces  50 ′,  50 ″ of the top and bottom dies  40 ′,  40 ″, respectively, while the top and bottom die abutment faces  44 ′,  44 ″ coincide with the green body median plane M. 
     Due to the presence of the undercut elements of the green body, i.e. the top and bottom major relief surfaces  28 J′,  28 J″ having obtuse relief angles ρJ, and due to the matching geometry of the die inner second peripheral surfaces  52 ′,  52 ″, the green body  20  cannot be released from the die cavity  70  and extracted therefrom through the punch tunnel  58 ′ of the top die  40 ′. In order to release the green body  20  and extract it from the tool-set  38 , an opening step has to be performed, in which the tool-set is brought to an open position (see  FIG. 8 ). To arrive at the open position, the top die  40 ′ and the top punch  60 ′ are moved up and away from the bottom die  40 ″ and the bottom punch  60 ″, opening the die cavity  70  and thereby exposing the green body  20 , leaving it free to be removed from the bottom die  40 ″. 
     The method of manufacturing a cutting insert green body has been illustrated above for a cutting insert having no through-hole. However, it will be apparent to a person skilled in the art that the above described method can easily be applied to manufacturing of cutting insert green bodies having through-holes formed therein. 
     Attention is drawn to  FIGS. 9 and 12 . A longitudinal through-hole green body  220  is compacted by a longitudinal through-hole tool-set  238 . Since the longitudinal through-hole green body  220  and the longitudinal through-hole tool-set  238  have many features which are similar to those of the green body  20  without a through-hole and its associated tool-set  38 , similar features will be referred to herein below by reference numerals which are shifted by 200 from those of the green body  20  without a through-hole and the associated tool-set  38 . The longitudinal through-hole green body  220  comprises a longitudinal through-hole  76  extending between the longitudinal through-hole green body top and bottom end faces  222 ′,  222 ″ perpendicularly to the green body median plane M. The longitudinal through-hole tool-set  238  comprises top and bottom longitudinal pins  78 ′,  78 ″ slidably disposed in punch pin through-bores  80 ′,  80 ″ extending through the punch mounting face  262 ′,  262 ″ and the punch pressing face  264 ′,  264 ″ of the respective top and bottom punches  260 ′,  260 ″. During compaction of the longitudinal through-hole green body  220 , the longitudinal pins  78 ′,  78 ″ extend into the die cavity  270  and constitute a longitudinal rod  82  which extends between the top and bottom punch pressing faces  264 ′,  264 ″, to form the longitudinal through-hole  76  in the compacted longitudinal through-hole green body  220 . 
     Attention is now drawn to  FIGS. 10 and 13 . A lateral through-hole green body  420  is compacted by a lateral through-hole tool-set  438 . Since the lateral through-hole green body  420  and the lateral through-hole tool-set  438  have many features which are similar to those of the green body  20  without a through-hole and its associated tool-set  38 , similar features will be referred to herein below by reference numerals which are shifted by 400 from those of the green body  20  without a through-hole and the associated tool-set  38 . Thus, the tool-set  438  includes top and bottom dies  440 ′,  440 ″ and top and bottom punches  460 ′,  460 ″. 
     The lateral through-hole green body  420  comprises a lateral through-hole  84  extending between lateral through-hole green body major central surfaces  430 J of opposing lateral through-hole green body major side faces  424 J along the major axis J. The lateral through-hole tool-set  438  comprises first and second lateral pins  86 F,  86 S slidably disposed in first and second top and bottom die pin channels  88 ′F,  88 ′S,  88 ″F,  88 ″S. During compaction of the lateral through-hole green body  420 , the first and second lateral pins  86 F,  86 S protrude into the die cavity  470  and abut each other to form a lateral rod  90 . The lateral rod  90  extends through first and second top and bottom opposing portions  92 ′F,  92 ′S,  92 ″F,  92 ″S of the die inner first peripheral surface to form the lateral through-hole  84  of the lateral through-hole green body  420 . 
     The above-described apparatus and method may facilitate pressing and subsequent ejection of green bodies having undercut elements. They also may allow for the formation of green bodies which have sharp, well-defined edges and acute wedge angles of the sort generally found desirable in cutting inserts manufactured from the green bodies. Finally, by eliminating acute re-entrant elements in its design, a tool set in accordance with the present invention may have adequate rigidity without suffering from increased risks of powder adhesion to the dies or punches and subsequent tear-off damage to the compacted green body. 
     Although the present invention has been described to a certain degree of particularity, it should be understood that alterations and modifications to the present invention may possibly be made without departing from the scope of the invention as hereinafter claimed.