IMPACTING METHOD AND MACHINE FOR FORMING COMPACTS

Abstract: A process and apparatus for producing solid articles from loose particulate materials that are particularly useful in the production of green compacts used in sintering processes. A charge (30) is formed by charging a mass of loose particulate material into the cavity (34) of a die between opposed first (28) and second die (128) punches, operably disposed to slide within the cavity (34), and limited to reciprocating motion in a linear direction. The first (28) and second die (128) punches are preloaded against the charge (30) and then first and second cyclically reciprocating impacting forces are applied to the first (28) and second (128) die punches, respectively, along the linear direction while holding the die (26) fixed so as to prevent damping of the impacting forces. The first and second cyclical reciprocating impacting forces may be substantially equal and may be substantially asynchronous or synchronous.

Description: IMPACTING METHOD AND MACHINE FOR FORMING COMPACTS Field of the Invention In general, this invention relates to impaction and compaction methods and apparatus for forming or densifying particulate material such as powder metals, ceramics, cermets, and other similarly processed materials into compacts. More particularly, this invention relates to high kinetic energy cyclic impacting of particulate material in a die to form a compact. Background of the Invention Compaction processes and apparatus to form powders or particulate material into compacts are used for a variety of products. Green compacts are formed and then sintered to be used in a variety of tool products and magnets. The types of powders and particulate material used in the tool industry include metallic, semi- metallic, ceramics, cermets, and others. Prior art die press machines have been used to press against punch dies in a mold cavity filled with the powder material to form compacts with a desired density. The green compact is then sintered to form, for example, a final tool as is well known in the art. Typical types of tools made with such methods include cutting inserts and grinding wheels. U.S. Patent No. 5,566,373, entitled "Press Apparatus", discloses a compaction method and apparatus for manufacturing a powder metallurgy article such as a green compact. This patent also serves to provide background of mechanical and hydraulic pressing of compacts. Vibrational methods and apparatuses have also been proposed as a method to make compacts such as in U.S. Patent Nos. 4,105,729, entitled "Method of Making Shaped Bodies" and 4,456,574, entitled "Method And Apparatus For Forming Particles Into Shaped Articles". The latter forms particles into shaped preforms by confining the loose particles in a shaped closure having at least one moveable side, subjecting each particle of the mass and at least a portion of the mold to an acceleration of a magnitude of at least 25 to 50 G's, and preferably in the range of 500 G's to 5000 G's, or greater, to generate at each particle a force causing such particle to impact with adjacent particles and form a homogeneous, fused article. The acceleration is provided by rapidly impacting the mold at the movable portions thereof at opposed ends of a distinct displacement of the contents of the mold, and usually in a vertical direction between an oscillating table and an underdamped pneumatic system tuned to oscillate out of phase with the table. This process is contrasted to the present invention which transmits substantially all of the kinetic energy to the particulate matter inside the die by impaction of the die punch while the die is held motionless and prevented from vibrating. U.S. Patent No. 4,770,849, entitled "Dynamically Loading Solid Materials Or Powders Of Solid Materials" discloses an impaction method and apparatus with which solid materials are dynamically loaded by impact with a piston fired at the material in a suitable support. A punch that serves as a body of material that introduces an impedance mismatch, is inserted between the piston and the material. The compaction and impaction methods of the prior art have several drawbacks. Some use very heavy press machines that are expensive to procure and operate. These methods are also prone to compact distortion and non-uniform density, both of which can result in defects such as laminations. The great pressures can result in rapid die wear and short die life. It is, therefore, highly desirable to produce green compacts having a more uniform density using less pressure than previously taught in the art. Punch faces are conventionally placed on punch tips to provide the "negative" or the negative relief impression surface to be formed on the surface of the green compact such as the grooves and raised and angled surfaces of a cutting tool insert. The punch is typically a steel shank with carbide tip brazed in place. The carbide tip is then ground or electro-formed and polished to produce the negative relief impression surface. Short runs, about 1000 inserts or less, may be made using less expensive plastic tips. Shaping the carbide tip is a slow, difficult and, therefore, expensive process. Plastic tips are easily shaped to final form, but because plastic materials are so soft the tips do not hold up very well under the high loads which are required for conventional or standard pressing. A carbide tip typically will last for production of tens of thousands of inserts and a plastic one is typically worn out producing less than one thousand. It is, therefore, highly desirable to have a machine and process that extend the useful life of plastic tips and use plastic tips for longer runs to produce more green compacts than conventional machines and processes are capable of and of those found in the prior art. Summary of the Invention The present invention provides a process and apparatus for producing solid articles from loose particulate materials that are particularly useful in the production of green compacts used in sintering processes. The process includes forming a charge by charging a mass of loose particulate material into the cavity of a die that is part of a die set that further includes at least a first die punch. The first die punch is operably disposed to slide within the cavity such that it is limited to reciprocating motion in a linear direction within the cavity and, at least in part, together with the die, defines a closed volume within the cavity. The process further includes preloading the first die punch against the charge within the cavity and applying a cyclical reciprocating impacting force to the first die punch along the linear direction while holding the die fixed so as to substantially prevent damping of the impacting force. The process may further include charging the mass of loose particulate materials into the cavity between the first die punch and a second die punch that is operably disposed to slide within the cavity such that the second die punch is limited to reciprocating motion in a linear direction within the cavity, preloading the second die punch against the charge within the cavity, and simultaneously applying the first cyclically reciprocating impacting force to the first die punch and a second cyclical reciprocating impacting force to the second die punch along the linear direction while holding the die fixed so as to prevent damping of the impacting forces. The first and second cyclical reciprocating impacting forces may be substantially equal and may be applied asynchronously or substantially synchronously. The process may further include using first and second reciprocating rams to impart kinetic energy to the first and second die punches by striking to apply the first and second reciprocating impacting forces, respectively. The process may further include applying the reciprocating impacting forces for a period of time on the order of not more than several seconds. A more particular embodiment of the invention applies the reciprocating impacting forces with a frequency of about 30 cycles per second for a time of up to one second. The apparatus includes a die set having a die with a cavity therethrough and at least a first die punch mounted on the apparatus so that it can be operably disposed to slide within the cavity. The first die punch, at least in part, together with the die defines a closed volume therein for accepting a charge of the particulate material. A motion limiting means is provided for limiting the first die punch to linearly reciprocating motion within the cavity. A first preloading means is used for preloading the first die punch against the charge and a fixing means is used to hold the die fixed during the impaction process. A first motive means is used for applying a first cyclical reciprocating impacting force to the first die punch. A more particular embodiment of the apparatus includes a second die punch mounted on the apparatus so that it can be operably disposed to slide within the cavity such that the first and second die punches, together with the die, define the closed volume and provide the motion limiting means operable for limiting the first and second die punches to the linearly reciprocating motion within the cavity. This embodiment includes a second preloading means for preloading the second die punch against the charge and a second motive means for applying a second cyclical reciprocating impacting force to the second die punch. The first and second motive means may be fluid powered devices or, more particularly, pneumatic actuators (e.g., air hammers). Electrically powered devices may also be used for motive means of the present invention (e.g., electromechanical linear actuators, including those known as "voice coil" actuators). Control means are preferably used to operate the first and second motive means either asynchronously or synchronously. Advantages The present invention is advantageous over the prior art because it provides better compacts having a more uniform density, shorter processing time, and with smaller and less expensive machines than in the prior art. Another advantage is that the invention allows production of green compacts that have less flash along the edges of the compact and, thus, require less machining or finishing. Green compacts made by the present invention have greater strength than those made using prior art methods and machinery and, therefore, are less prone to damage such as chipping and cracking in subsequent handling. This is advantageous from a cost standpoint because of the reduced scrap rate the present invention affords. The present invention is advantageous over the prior art because it provides green compacts having less spring back after the compaction, thus, allowing the green compacts to be more easily removed or ejected from the dies with less damage and a lower scrap rate. The more uniform density provides a further advantage by allowing production of less distorted sintered products made from green compacts of the present invention. Another more particular advantage of the present invention is that green compacts for cutting tool inserts may be produced with deeper and better chip breaking grooves, and other surface features, than in the prior art. Another advantage of the present invention is that it allows for greater use of plastic tips for the punches instead of more expensive tips (e.g., carbide tips). The present invention provides a significant extension of the life of all punch faces and molds including plastic ones. This extended life may allow plastic punch faces to be used for full production. This may allow perhaps as much as a tenfold increase of useful life (e.g., for up to about 10,000 inserts from an inexpensive plastic punch face from about 1000 inserts as is presently capable). The present invention may allow the expensive, time consuming carbide faces to be replaced altogether for many applications, thus, providing a net savings on tool costs. Brief Description of the Drawings FIG. 1 is a schematic illustration of a compacting machine employing electromechanical impaction apparatus in accordance with a first exemplary embodiment of the present invention; FIG. 1 A is an enlarged view of a die set used in the machine of FIG. 1 ; FIG. 1 B is an enlarged view of the electromechanical impaction apparatus used in the machine of FIG. 1 ; FIG. 2 is a perspective view illustration of a green compact for a cutting tool insert produced in accordance with the present invention; FIG. 2A is a cross-sectional view of the insert taken along the line 2A-2A of FIG. 2; FIG. 2B is a perspective view illustration of an alternative plastic tipped die punch used in the machine of FIG. 1 ; FIG. 3 is a schematic illustration of a compacting machine employing air hammer impaction apparatus in accordance with a second exemplary embodiment of the present invention; FIG 3A is an enlarged view of a grinding wheel die set used in the machine of FIG 3, and FIG 3B is a perspective view of a green compact for a grinding wheel, produced in accordance with the present invention and with the apparatus of FIG 3 Description of the Invention Illustrated in FIGS 1 , 1A and 1B is a compacting machine 5 having at least a first or an upper impacting apparatus 10 with a die set 20 mounted in a die fixtuπng cross member 22 fixedly mounted to columns 23 of a machinery frame 24 of the compacting machine 5 The upper impacting apparatus 10 is one embodiment of an apparatus that may be used to form a compact by an impacting process of the present invention The die set 20 has a die 26 fixedly mounted to the fixturing cross member 22, with at least an upper die punch 28 operably disposed to slide within a linear cavity 34 of the die such that the upper die punch, at least in part, together with the die defines a closed volume 29 therein for accepting and containing a charge 30 of a mass of the particulate material which is to be compacted The die 26 has a smooth linear inner wall 32 that surrounds the cavity 34 which in part forms the closed volume 29 in the die set 20 The smooth linear inner wall 32 and the conformal linear cavity 34 provides a motion limiting means for limiting the upper die punch to linearly reciprocating motion, in a linear reciprocating direction A within the cavity 34, along a machine axis 36 The die fixturing cross member 22 provides a fixing means to hold the die 26 fixed during the impaction process An upper preloading means for preloading the upper die punch 28 against the mass or charge 30 is provided by a pneumatic upper preload actuator 40 mounted on a top cross member 42 which, in turn, is supported by the columns 23 The upper preload actuator 40 has a cylinder 43 and an extensible actuator rod 44 which is connected to an upper slidable cross member 46 by way of an upper sub-frame 48 The upper die punch 28 includes a shank 50, having a punch face 49 at its lower end, which contacts the charge 30 The shank 50 is operably disposed to slide through an aperture 54 in the upper slidable cross member 46, and has a shouldered head 56 at its upper end, extending beyond the aperture The upper slidable cross member 46 has a cover 58 over the shouldered head 56 that traps the head between the cover and the top surface 59 of the slidable cross member with a clearance C therebetween 7 that allows limited axial travel of the shank 50 within the aperture 54. The upper slidable cross member 46 is operably disposed to slide along the columns 23 such that its cover 58 can be brought to bear against the shouldered head 56, and thus preload the die punch 28 against the charge 30. An upper motive means for applying a cyclical reciprocating impacting force to the upper die punch 28 is illustrated in the form of an electromechanical upper impact actuator 60 mounted to the upper sub-frame 48. The impact actuator 60 shown is of the type often referred to as a "voice coil" actuator, and typically includes a coil 62 wound on a non-ferrous base 64 and a field core assembly 66. The coil 62 is situated in a gap 67 between the field and the core and must be mechanically confined to allow motion of the coil along the force vector. When coil current flows, force is generated. Direction A and amplitude is determined by the magnitude and direction of the current flow. Voice coils are most often used in acoustic speakers, so this particular application of a voice coil device is unique. BEI Sensors & Systems Company, Kimco Magnetics Division, is a commercial source of voice coil devices. One actuator which may be of particular use in this invention is disclosed in U.S. Patent No. 5,345,206, entitled "Moving Coil Actuator Utilizing Flux-Focused Interleaved Magnetic Circuit". Other types of electrically powered drivers may also be used for the motive means of the present invention, e.g., piezo-eiectric devices, and electromagnetic linear actuators. The coil 62 has a short bar 68 attached to it, and together they serve as a reciprocating ram 69. A cover aperture 70 is centered along the machine axis 36 through the cover 58 and allows the bar 68 to pass through the cover and strike the shouldered head 56, thereby transferring kinetic energy generated by the upper impact actuator 60 to the upper die punch 28 with the cyclical reciprocating motion and impacting force of the ram 69. The impacting force is used to impart substantially all of the kinetic energy to the charge 30 with a cyclical reciprocating motion, causing the mass to be compacted and form the final compact in only a few seconds at most. The fixing means, fixturing cross member 22, holds the die 26 stationary, so as to substantially prevent any damping of the impacting force, prevent unwanted vibrations of the die set, and cause substantially all of the kinetic energy to be imparted to the charge 30. Because the compacting force comes from the upper impact actuator 60, very little force is required from the upper preload actuator 40. As the mass of the charge 30 compacts under the impacting force, which is applied with the cyclical reciprocating motion, the upper preload actuator 40 continuously holds the upper die punch 28 against the charge 30 by urging the upper slidable cross member 46 and the upper sub-frame 48 towards the die 26. In other words, the upper preload actuator serves to merely hold the upper die punch 28 against the charge 30 and prevent the die set from coming apart. The preferred embodiment of the invention is the compacting machine 5 with the upper impacting apparatus 10 and a substantially identical second lower impacting apparatus 110. The die set 20 preferably has a lower die punch 128 which is operably disposed to slide within the cavity 34, in opposition to the upper die punch 28, such that the lower die punch 128, upper die punch 28, and die 26 define the closed volume 29. The smooth linear inner wall 32 and the conformal linear cavity 34 also provide a motion limiting means for limiting the lower die punch 128 to linearly reciprocating motion within the cavity 34. A second preloading means for biasing the lower die punch 128 against the mass or charge 30 is provided by a pneumatic lower preload actuator 140 mounted on a machine base 142 of the compacting machine 5. The columns 23 extend upward from the machine base 142. The lower preload actuator 140 has a cylinder 143 and an extensible actuator rod 144 which is connected to a lower slidable cross member 146 by way of a lower sub-frame 148. The lower die punch 128 includes a shank 150, having a second punch face 149 at its upper end, which contacts the charge 30. The shank 150 is operably disposed to slide through an aperture 154 in the lower slidable cross member 146, and has a shouldered head 156 at its lower end, extending beyond the aperture. The lower slidable cross member 146 has a cover 158 over the shouldered head 156 that traps the head between the cover and the bottom surface 159 of the slidable cross member with a clearance C therebetween that allows limited axial travel of the shank 150 within the aperture 154. The lower slidable cross member 146 is operably disposed to slide along the columns 23 such that its cover 158 can be brought to bear against the shouldered head 156, and thus preload the die punch 128 against the charge 30. The lower or upper preload actuators can also be used to eject the green compacts. The present invention yields a green compact that is easier to eject and requires low power pneumatic actuators, which improves the ejection step and lowers scrap rate. A second motive means for simultaneously applying a second cyclical reciprocating impacting force to the lower die punch 128 is illustrated in the form of a lower impact actuator 160 mounted to the lower sub-frame 148. The first and second motive means as illustrated by the upper and lower impact actuators 60 and 160, respectively, are preferably controlled by an electronic controller 400 that can control their operation such that they may impart kinetic energy to the charge 30 with impacting forces that are substantially equal, and either asynchronous or substantially synchronous. Illustrated in FIGS. 2 and 2A is a green compact 200 for a cutting tool insert typical of the present art, substantially similar to that disclosed in U.S. Patent No. 5,584,616. The green compact 200 and its corresponding insert have various surface features including a chip groove 204 with a depth D and used for chip breaking. The chip groove 204 is formed between a pair of cutting faces 205 sloping downwardly from sides 206 of the compact 200 and chip breaker faces 207 that slope upward from respective ones of the cutting faces. The present invention provides a better apparatus and process for forming green compacts and cutting tool inserts with such intricate surface features. A cutting tool insert is formed by sintering the green compact, and looks substantially like the green compact 200 illustrated in FIG. 2. FIG. 2B illustrates another more particular embodiment of the present invention, a plastic tip 208 having a plastic punch face 49 disposed at the end of the metal shank 50 which contacts the charge 30. The plastic punch face 49 includes a raised portion 209 which corresponds to the surface features of the chip groove 204 of the green compact 200. Using a plastic tip and punch face provides many economical advantages described above. Another type of green compact for which this invention was developed is a grinding wheel green compact 300 having a bore 302, as illustrated in FIG. 3B. The grinding wheel green compact 300 may be produced in accordance with the present invention using a compacting machine 5 with a grinding wheel die set 210 as illustrated in FIGS. 3 and 3A. FIGS. 3 and 3A illustrate an embodiment of the 10 invention having fluid powered drivers as the motive means and, more particularly, pneumatic powered upper and lower motive means in the form of upper and lower air hammers 61 and 161 for simultaneously applying cyclical reciprocating impacting force to upper and lower annular die punches 188 and 190, respectively. A pneumatic controller 410 is preferably used to control the operation of the upper and lower air hammers 61 and 161 , such that they may impart kinetic energy to the charge 30 with impacting forces that are substantially equal, and either asynchronous or substantially synchronous. The grinding wheel green compact 300 is formed within a cylindπcally shaped cavity 34 within an annular die 226 of the grinding wheel die set 210. The upper and lower annular die punches 188 and 190 and the charge 30 are disposed around a center post 228 of the grinding wheel die set 210. The center post 228 is used to form the bore 302 of the grinding wheel green compact 300. Flat annular upper and lower stop plates 232U and 232L, respectively, are placed in contact over the upper and lower annular die punches 188 and 190, respectively. The upper and lower air hammers 61 and 161 each have pneumatic cylinders 220 and pneumatic rams 222. The upper and lower punch tools 236 and 238 each have a tool shank 240 and a shouldered tool head 242 at one end of the shank, away from the die set 210. The upper and lower slidable cross members 46 and 146 engage respective ones of the tool heads 242, which, in turn, engage the upper and lower stop plates 232U and 232L, respectively, and preload the upper and lower annular die punches 188 and 190 against the charge 30. Annular rubber pads 250 are disposed within cylindrical center recesses 252 of the upper and lower stop plates 232U and 232L, respectively, to center and position the center post 228. When the air hammers 61 and 161 are operated, each pneumatic ram 222 impacts one of the tool shanks 240, and transfers kinetic energy generated by the air hammers to the charge 30. The fixturing cross member 22 used in the compacting machine 5 illustrated in FIGS. 1 , 1A and 1 B is not used in the compacting machine 5 with the grinding wheel die set 210 as illustrated in FIGS. 3 and 3A. The mass and inertia of the grinding wheel die set 210 and the charge 30, together with the preload forces provided by the upper and lower preloading means, using the upper preload actuator 40 and the lower preload actuator 140, provide a fixing means to hold the annular die 226 fixed, 11 so as to substantially prevent any damping of the impacting force, prevent unwanted vibrations of the die set, and cause substantially all of the kinetic energy to be imparted to the charge 30. This fixing means is enhanced by imparting kinetic energy to the charge 30 with impacting forces that are substantially equal and synchronous or sufficiently synchronous to prevent unwanted vibrations of the die set and to cause substantially all of the kinetic energy to be imparted to the charge 30. During loading of the charge 30 into the annular die 226, the annular die is held up off of the lower stop plate 232L with spacers 243 (shown with dotted lines in FIG. 3A) to permit the lower annular die punch 190 to project out of the bottom of the annular die 226 by the approximate distance it will travel along the axis 36 during impacting as the charge 30 is compressed (about the thickness of the spacers 243). After the center post 228 is inserted into lower annular die punch 190, the charge 30 is loaded, and then the upper annular die punch 188 is inserted into the top of the annular die 226. The upper annular die punch 188 is set so it also projects out of the annular die 226 approximately the distance it will travel along the axis 36 during impacting. The upper stop plate 232U is placed on the upper annular die punch 188 and then the assembly of the grinding wheel die set 210 together with the rubber pads 250 set in place as shown in FIG. 3A is positioned in the compacting machine 5 between the upper and lower punch tools 236 and 238, respectively. This operation may be done manually or may be automated. A preload is applied to the upper and lower stop plates 232U and 232L, respectively, through the upper and lower punch tools 236 and 238, respectively. The preload is preferably set to a value between two and ten percent of the load required to compact the charge 30 to a desired or predetermined density using only static pressing. Once the preload is achieved, the spacers 243 are removed. The preload on the powder of the charge keeps the annular die 226 from dropping down around the lower annular die punch 190 by pressure and friction against the inside surface of the annular die 226. During impacting the friction between the charge 30 and the annular die 226 prevents the annular die from moving either up or down from the impacting process, for both synchronous or asynchronous modes. After impacting, the preload is released and the grinding wheel die set 210 is removed from the compacting machine 5 for ejection or removal of the grinding wheel green 12 compact 300. Impacting times for larger compacts will obviously be longer than for smaller compacts. Other types of motive means contemplated by the present invention include, but are not limited to, a hydraulically powered driver; an electrically powered motor providing power to a mechanical linkage or cams which, in turn, provides a cyclical reciprocating motion and impacting force; and a piezo-electric crystal stack, energized by an electrical oscillator circuit. Compacts, such as green compacts for cutting tool inserts or grinding wheels, may be produced in accordance with a process of the present invention as will now be described. The process includes forming a charge by charging a mass of loose particulate material into the cavity of the die of the die set. The die set includes at least a first die punch and, preferably, an opposing second die punch. The die punches are operably disposed to slide within the cavity, and are thus limited to reciprocating motion in a linear direction. The die punches, together with the die, define the closed volume within the cavity that holds the charge. The opposed die punches are preloaded against the charge within the cavity, and first and second cyclical reciprocating impacting forces are simultaneously applied to the first and second die punches, respectively, along the linear direction, while holding the die fixed so as to substantially prevent damping of the impacting forces. The process in some instances may be practiced with just one die punch and by applying one cyclical reciprocating impacting force to the single die punch, but, as stated above, the preferred method uses first and second cyclical reciprocating impacting forces, simultaneously impacting opposed first and second die punches, respectively, such that the first and second cyclical reciprocating impacting forces are substantially equal, and may be simultaneously applied asynchronously or synchronously with respect to each other. The process may further use first and second reciprocating rams to impart kinetic energy to the first and second die punches by striking to apply the first and second reciprocating impacting forces, respectively. The process may further include applying the reciprocating impacting forces for a period of time on the order of not more than several seconds. These short time periods enhance the invention's value considerably over the prior art. It is has been found that for making small grinding wheels and tool inserts the 13 reciprocating impacting forces may be applied with a frequency of about 30 cycles per second for a time of up to one second. It may be noted that the green compact 200, depicted in Figs. 2 and 2A, might also be formed with a central hole similar to that of the insert of U.S. Patent No. 5,584,616, by employing a center post and post supporting technique like that shown and described in connection with the center post 228 of Fig. 3A. While the invention has been shown in connection with a preferred embodiment, it is not the intention that the invention be so limited. Rather, the invention extends to all such designs and modifications as come within the scope of the appended claims.

Claims: 14 What is claimed is: 1. A process for producing solid articles from loose particulate material, said process comprising: charging a mass of loose particulate material into a cavity of a die to form a charge, the die being an element of a die set having at least a first die punch operably disposed to slide within the cavity, the first die punch being limited to reciprocating motion in a linear direction within the cavity and at least in part, together with the die surrounding the cavity, defining a closed volume therein, preloading the first die punch against the charge within the cavity, and applying a first cyclical reciprocating impacting force to the first die punch along the linear direction while holding the die fixed so as to substantially prevent damping of the impacting force. 2. The process according to claim 1 further comprising preloading the first die punch against the charge within the cavity before applying the first cyclical reciprocating impacting force. 3. The process according to claim 2 further comprising: charging the mass of loose particulate material into the cavity of the die between the first and a second die punch that is operably disposed to slide within the cavity, preloading the second die punch against the charge within the cavity, and simultaneously applying the first cyclical reciprocating impacting force to the first die punch and a second cyclical reciprocating impacting force to the second die punch along the linear direction while holding the die fixed so as to prevent damping of the impacting forces. 4. The process according to claim 3 wherein the first and second cyclical reciprocating impacting forces are substantially equal. 15 5. The process according to claim 3 further comprising applying the first and second cyclical reciprocating impacting forces substantially asynchronously. 6. The process according to claim 3 further comprising applying the first and second cyclical reciprocating impacting forces substantially synchronously. 7. The process according to claim 3 further comprising using first and second reciprocating rams to impart kinetic energy to the charge by striking the first and second die punches to apply the first and second reciprocating impacting forces, respectively. 8. The process according to claim 3 further comprising applying the reciprocating impacting forces for period of time on the order of not more than several seconds. 9. The process according to claim 8 further comprising applying the reciprocating impacting forces with a frequency of about 30 cycles per second for a time of up to one second. 10. An apparatus for producing compacted shapes from a charge of particulate material by an impaction process, said apparatus comprising: a die set including a die having a cavity disposed therein, at least a first die punch operably mounted on said apparatus to slide within said cavity, said first die punch at least in part, together with said die, defining a closed volume within said cavity for accepting the charge of the particulate material, motion limiting means for limiting said first die punch to linearly reciprocating motion within said cavity, a first preloading means for preloading said first die punch against the charge, fixing means to hold said die fixed during said impaction process, and a first motive means for applying a first cyclical reciprocating impacting force to said first die punch. 16 11. The apparatus according to claim 10, said first motive means including a fluid powered driver. 12. The apparatus according to claim 10, said first motive means including a pneumatic hammer. 13. The apparatus according to claim 10, said motive means including an electromagnetic driver. 14. The apparatus according to claim 10, said motive means including an electric voice coil. 15. The apparatus according to claim 10, further comprising: a second die punch operably mounted on said apparatus to slide within said cavity, said first and second die punches together with said die defining said closed volume, said motion limiting means operable for limiting said second die punch to said linearly reciprocating motion within said cavity, a second preloading means for preloading said second die punch against the charge, and a second motive means for applying a second cyclical reciprocating impacting force to said second die punch. 16. The apparatus according to claim 15, said first and second motive means comprising first and second pneumatic hammers, respectively. 17. The apparatus according to claim 15, said first and second motive means comprising first and second electrically powered voice coils, respectively. 17 18. An article made from a green compact wherein the green compact is formed by an impacting process comprising: charging a mass of loose particulate material into a cavity of a die to form a charge, the die being an element of a die set having at least a first die punch operably disposed to slide within the cavity, the first die punch being limited to reciprocating motion in a linear direction within the cavity and at least in part, together with the die surrounding the cavity, defining a closed volume therein, preloading the first die punch against the charge within the cavity, and applying a first cyclical reciprocating impacting force to the first die punch along the linear direction while holding the die fixed so as to substantially prevent damping of the impacting force. 19. The article according to claim 18 wherein said process further comprises: preloading the first die punch against the charge within the cavity before applying the first cyclical reciprocating impacting force. 20. The article according to claim 19 wherein said process further comprises: charging the mass of loose particulate material into the cavity of the die between the first and a second die punch that is operably disposed to slide within the cavity, preloading the second die punch against the charge within the cavity, and simultaneously applying the first cyclical reciprocating impacting force to the first die punch and a second cyclical reciprocating impacting force to the second die punch along the linear direction while holding the die fixed so as to prevent damping of the impacting forces. 21. The article according to claim 20 wherein said first and second cyclical reciprocating impacting forces are substantially equal. 18 22. The article according to claim 21 wherein said process further comprises: applying said first and second cyclical reciprocating impacting forces substantially synchronously. 23. The article according to claim 22 wherein said compact is sintered after said impacting process. 24. The article according to claim 23 wherein said article is a cutting tool insert. 25. The article according to claim 24 wherein said cutting tool insert includes cutting surface features. 26. The article according to claim 25 wherein said cutting tool insert further includes chip breaking surface features. 27. The article according to claim 24 wherein said cutting tool insert includes at least one chip groove for chip breaking and said groove is formed between a pair of cutting faces sloping downwardly from sides of said insert and a pair of chip breaker faces sloping upward from respective ones of said cutting faces. 28. The article according to claim 23 wherein said article is a grinding wheel.

Inventors: SUPROCK DAVID M, WYDER WALTER C, SUPROCK, DAVID, M., WYDER, WALTER, C.
Applicants: CINCINNATI MILACRON INC, MILACRON INC.
Application year: 1999
Main classification: B30B11
IPC codes: B22F3, B23B27, B23P15, B24D7, B24D18, B30B11