Patent Publication Number: US-7913369-B2

Title: Ceramic center pin for compaction tooling and method for making same

Description:
This application is a Continuation of, and claims priority benefit from, U.S. patent application Ser. No. 10/320,331, filed Dec. 16, 2002, for a “CERAMIC CENTER PIN FOR COMPACTION TOOLING AND METHOD FOR MAKING SAME,” by L. Gakovic, which also claims the benefit from U.S. Provisional Application No. 60/371,816, filed Apr. 11, 2002 for a “CERAMIC CENTER PIN FOR COMPACTION TOOLING AND METHOD FOR MAKING SAME,” by Luka Gakovic, both applications are hereby incorporated by reference in their entirety. 
     This invention relates generally to compaction tooling components, and more particularly to a compaction tool, such as a center pin, incorporating a tip or wear surface comprising a ceramic component and the method for manufacturing and assembling such a center pin. 
    
    
     BACKGROUND AND SUMMARY OF THE INVENTION 
     The present invention is directed to improvements in the tooling used in compaction equipment and tableting machines, and particularly the tooling used in the equipment utilized in making components of dry-cell batteries, e.g., various sizes of 1.5 volt (AAA, AA, C, D) and 9 volt batteries used in consumer electronic devices. It will be further appreciated that various aspects of the invention described herein may be suitable for use with well-known compaction tooling and tableting equipment, and particularly to center pins and punches employed in the manufacture of oral pharmaceuticals, etc. 
     Heretofore, a number of patents have disclosed processes and apparatus for the forming of parts by the compression of unstructured powders, sometimes followed by heat-treating of the compressed part. The relevant portions of these patents may be briefly summarized as follows; and are hereby incorporated by reference for their teachings: 
     U.S. Pat. No. 5,036,581 of Ribordy et al, issued Aug. 6, 1991, discloses an apparatus and method for fabricating a consolidated assembly of cathode material in a dry cell battery casing. 
     U.S. Pat. No. 5,122,319 of Watanabe et al, issued Jun. 16, 1992, discloses a method of forming a thin-walled elongated cylindrical compact for a  magnet. 
     U.S. Pat. No. 4,690,791 of Edmiston, issued Sep. 1, 1987, discloses a process for forming ceramic parts in which a die cavity is filled with a powder material, the powder is consolidated with acoustic energy, and the powder is further compressed with a mechanical punch and die assembly. 
     U.S. Pat. No. 5,930,581 of Born et al, issued Jul. 27, 1999, discloses a process for preparing complex-shaped articles, comprising forming a first ceramic-metal part, forming a second part of another shape and material, and joining the two parts together. 
     Referring to  FIG. 1 , there is illustrated a prior art compaction tool as might be employed for the production of a cylindrically shaped battery component. In use of such a tool in battery manufacturing, the die  20  receives a lower punch  22  that is inserted into the die. The lower punch includes a through-hole in the center thereof that allows a center pin  24  to be inserted therein. The punch and center pin then, in conjunction with the die, form a cavity into which a powder mix employed in battery manufacture can be deposited. Such a powder mix may include wetting agents, lubricating agents, and other proprietary solvents added just before filing the die cavity. Once filled, the cavity is then closed by an upper punch  26  that is inserted into the upper end of the die and the punches are directed toward one another so as to compact the powder material  28  therein. In typical systems, the compaction force is applied by mechanical and/or hydraulic systems so as to compress the powder material and produce a compacted part (e.g., a tablet or a cylindrical component), examples of which are described in the patents incorporated by reference above. 
     During the compaction process, however, the application of significant compressive forces results in a high friction level applied to the interior of the die surface in region  30  and to the exterior of the center pin tip in region  31 . This friction force causes a high level of wear on the compaction tooling, resulting in the frequent need to change out and rework such tooling. Although it is known to employ ceramics in the interior region of the die, to reduce the wear from friction, ceramics have not been successfully employed on the center pin tip because of the difficulty in reliably affixing the ceramic to the center pin. Although a ceramic coating may be provided on a center pin tip by known methods, e.g. arc plasma spray coating, such coatings have not been found to be satisfactory. 
     Thus, it is often the case that the dies considerably outlast the center pins and that frequent replacement and rework of center pins continues to be a problem that plagues the powder compaction industry. One prior art method and apparatus for the manufacturing of cylindrical dry cell batteries, which entails the compression of powdered material is described in U.S. Pat. No. 5,036,581 of Ribordy et al, previously incorporated by reference. 
     The present invention is, therefore, directed to both an apparatus that successfully employs a ceramic component on the wear surfaces of a compaction tooling center pin or core rod, as well as the methods of making and repairing the same. In particular, the invention relies on various alternative embodiments for connecting a ceramic component to the end of a metal center pin base; the selection of the particular embodiment may be dependent upon the use characteristics for the apparatus. 
     In accordance with an aspect of the present invention, there is provided an apparatus for forming a powder material into a solid form through the application of pressure, comprising: a die; a lower compression punch insertable into a lower end of said die, said lower compression punch having a ceramic-tipped center pin passing therethrough where the ceramic reduces the wear of said outer surface of said center pin; means for filling at least a portion of the cavity defined by said die, said lower compression punch, and said center pin with the powder material; and an upper compression punch, insertable into an upper end of said die to compact the powder material. 
     In accordance with another aspect of the present invention, there is provided a method of manufacturing a compression center pin for use in a punch and die powder compaction apparatus, comprising the steps of: forming a center pin base of a rigid material (e.g., tool steel or pre-hardened steel); forming a center pin tip of a ceramic material (e.g., zirconia); and affixing the center pin tip to the center pin base. 
     In accordance with yet another aspect of the present invention, there is provided a method of repairing a compression center pin for use in a punch and die powder compaction apparatus, comprising the steps of: removing a center pin tip from a center pin base; reworking or replacing the center pin tip with a ceramic material (e.g., zirconia); and affixing the center pin tip to the center pin base. 
     One aspect of the invention is based on the discovery of techniques for connecting or semi-permanently affixing a ceramic tip for a center pin to the center pin base in a manner that will survive the high pressure and friction of the compaction apparatus. The techniques described herein not only allow for the successful attachment of ceramic tips, but also allow for the reworking and replacement thereof, so that only damaged or worn components are replaced, and not the entire center pin. It will be appreciated that solid ceramic center pins may be produced, however, they are believed to be cost prohibitive and difficult to repair and rework. 
     The techniques described herein are advantageous because they can be adapted to any of a number of compaction tooling applications. In addition, they can be used in other similar compaction embodiments to allow for the use of ceramic materials in high-friction environments where tool steels and other surface hardening processes fail to provide sufficient improvement in tool life. The techniques of the invention are advantageous because they provide a range of alternatives, each of which is useful in appropriate situations. As a result of the invention, the life of compaction center pins and other tooling may be significantly increased and the cost of reworking the same may be reduced. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross-sectional view of a prior art compaction tooling die, punch and center pin set for compaction of a powder material for use in a dry cell battery; 
         FIG. 2  is a cross-sectional view of the various components of  FIG. 1 , including an aspect of the present invention; 
         FIGS. 3A ,  3 B,  3 C, and  3 D are cross-sectional views of the components and assemblies of embodiments of the present invention; 
         FIGS. 4A ,  4 B, and  4 C are side elevation views of alternative center pin designs, for the purpose of illustrating, without limitation, three alternative configurations of attaching the center pin base to the associated tableting or compaction equipment; 
         FIGS. 5A through 5C  are cross-sectional views of alternative embodiments of the present invention; 
         FIGS. 6A and 6B  are cross-sectional views of the components and assemblies of an alternative center pin made in accordance with the present invention; 
         FIGS. 7A and 7B  are cross-sectional views of two alternative embodiments of the present invention; 
         FIG. 8  is a detailed cross sectional view of an embodiment of the present invention wherein a ceramic tip is joined to a base using adhesive, and wherein a shimming wire is helically disposed on the male part thereof to effect the alignment of such part with the female part; and 
         FIG. 9  is a cross sectional view of an additional embodiment of the present invention, in which a threaded fastener is used to join the parts thereof. 
     
    
    
     The present invention will be described in connection with a preferred embodiment, however, it will be understood that there is no intent to limit the invention to the embodiments described. On the contrary, the intent is to cover all alternatives, modifications, and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims. 
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     For a general understanding of the present invention, reference is made to the drawings. In the drawings, like reference numerals have been used throughout to designate identical elements. 
     Reference may also be had to Table 1, “Glossary Of Ceramic Terms”, and Table 2, “General Descriptions of Structural Ceramic Materials”, both Innex Industries, Inc. internal publications. Tables 1 and 2 are incorporated herein for their teachings of terms and properties related to ceramic materials used in the present invention. 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 GLOSSARY OF CERAMIC TERMS: ZIRCONIA WEAR PARTS 
               
            
           
           
               
               
            
               
                 TERM 
                 DEFINITION 
               
               
                   
               
               
                 Density 
                 Mass per unit volume of a substance 
               
               
                 (metric units: g/cm 3 , Kg/m 3 ) 
                   
               
               
                 Strength 
                 The stress (force per area) required to rupture, crack, fracture, 
               
               
                 Flexural strength 
                 break the material 
               
               
                 Modulus of Rupture, MOR 
                 High strength needed for impact and thermal shock 
               
               
                 3 or 4-point-bend strength 
                 Flaws cause fracture in ceramics and must be controlled by 
               
               
                 (metric units: MPa, GPa) 
                 careful processing 
               
               
                 Toughness 
                 Toughness is described as the load per unit area required to 
               
               
                 Fracture Toughness 
                 initiate a crack when load is applied to a surface. Ceramics and 
               
               
                 Critical Stress Intensity Factor 
                 glass are stronger than metals, but less tough and fail by 
               
               
                 K 1c   
                 fracture (cracking). 
               
               
                 (metric units: MPa-m 1/2 ) 
                 High toughness stops cracking 
               
               
                   
                 Toughness improves strength, impact resistance 
               
               
                   
                 Low toughness can lead to wear and fracture 
               
               
                 Hardness 
                 Hardness is the resistance of a material to compression, 
               
               
                   
                 deformation, denting, scratching, and indentation. Hardness is a 
               
               
                   
                 useful relative measure rather than a material property, and is 
               
               
                   
                 usually measured by indentation. 
               
               
                   
                 Hardness important for wear resistance, but higher 
               
               
                   
                 hardness leads to lower toughness 
               
               
                   
                 Hardness greatly affected by ceramic processing 
               
               
                 Vickers Hardness, H v   
                 The Vickers Hardness test is used for ceramics. It is similar to 
               
               
                 Vickers Hardness Number, VHN 
                 the Brinell Hardness test, using an indentor in the form of a 
               
               
                 (metric units: GPa, Kg/mm 2 ) 
                 square-based diamond pyramid. The result is expressed as the 
               
               
                   
                 load divided by the area of the impression. 
               
               
                 Wear-resistance 
                 Wear-resistance is generally defined as the progressive removal 
               
               
                   
                 of material from the surface under operational conditions. 
               
               
                   
                 High hardness, toughness, strength are best for wear- 
               
               
                   
                 resistance, but harder materials can lack toughness 
               
               
                   
                 Correct material must be selected for the application 
               
               
                 Zirconia 
                 Zirconia in the partially stabilized phase is a tough, white 
               
               
                 Zirconium oxide 
                 ceramic with fairly good hardness. Alumina can be added to 
               
               
                 Zirconium dioxide 
                 zirconia to increase the hardness. Zirconia&#39;s excellent wear 
               
               
                 ZrO 2   
                 resistant properties depend on a phase change (martensitic 
               
               
                 Partially stabilized zirconia, PSZ 
                 transformation) that limits the high temperature use. Fully 
               
               
                 Tetragonal zirconia polycrystal, 
                 stabilized zirconia is used in fuel cells, oxygen sensors, and 
               
               
                 TZP 
                 jewelry. 
               
               
                 Alumina 
                 Aluminum oxide is a very hard white ceramic that is stable at 
               
               
                 Aluminum oxide 
                 elevated temperatures but has fairly low toughness. Alumina is 
               
               
                 Corundum 
                 excellent in sliding wear, if there is no impact. Zirconia can be 
               
               
                 Al 2 O 3   
                 added to alumina to increase the toughness. 
               
               
                 Stabilizers 
                 Stabilizers are added to zirconia to produce the toughening 
               
               
                 Additives 
                 effect. The stabilizers are oxide additives that change the 
               
               
                 Stabilizing, stabilization 
                 zirconia to the toughened (partially stabilized) phase. These 
               
               
                 Partially stabilized 
                 include yttria (Y 2 O 3 ), magnesia (MgO), calcia (CaO), and ceria 
               
               
                   
                 (CeO 2 ). The additives also affect the hardness of the zirconia. 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 2 
               
             
            
               
                   
               
               
                 GENERAL DESCRIPTIONS OF STRUCTURAL CERAMIC MATERIALS 
               
            
           
           
               
               
               
               
            
               
                   
                   
                   
                 RELATIVE 
               
               
                 MATERIAL 
                 PROCESSING 
                 COMMON APPLICATIONS 
                 COST 
               
               
                   
               
            
           
           
               
               
               
               
            
               
                 Oxides 
                   
                   
                   
               
               
                 Alumina 
                 Pressureless sintering 
                 Wide range of applications including: 
                 1 
               
               
                 Al 2 O 3   
                 (1550-1700 C.) 
                 Electronic substrates, spark plug 
                   
               
               
                   
                 Hot Isostatic Pressing 
                 insulators, transparent envelopes for 
                   
               
               
                   
                 (HIPing) 
                 lighting, structural refractories, wear 
                   
               
               
                   
                   
                 resistant components, ceramic-to-metal 
                   
               
               
                   
                   
                 seals, cutting tools, abrasives. Thermal 
                   
               
               
                   
                   
                 insulation, catalyst carriers, biomedical 
                   
               
               
                   
                   
                 implants 
                   
               
               
                 Zirconia 
                 Pressureless sintering 
                 Wear resistant components, cutting 
                 3 
               
               
                 (ZrO 2 ) 
                 (1500 C.) 
                 tools, engine components, thermal 
                   
               
               
                   
                   
                 coatings, thermal insulation, biomedical 
                   
               
               
                   
                   
                 implants, fuel cell 
                   
               
               
                 Zirconia 
                 Pressureless sintering 
                 Wear resistant components 
                 3 
               
               
                 Toughened 
                 (1500-1600 C.) 
                   
                   
               
               
                 Alumina 
                   
                   
                   
               
               
                 (ZTA) 
                   
                   
                   
               
               
                 Alumina 
                 Pressureless sintering 
                 Wear resistant components 
                 3 
               
               
                 Toughened 
                 (1500-1600 C.) 
                   
                   
               
               
                 Zirconia 
                   
                   
                   
               
               
                 (ATZ) 
                   
                   
                   
               
               
                 Nonoxides 
                   
                   
                   
               
               
                 Silicon 
                 Pressureless sintering 
                 Refractories, abrasives, mechanical 
                 5 
               
               
                 Carbide 
                 Hot Pressing, HIPing 
                 seals, pump bearings 
                   
               
               
                 (SiC) 
                   
                   
                   
               
               
                 Silicon Nitride 
                 Pressureless sintering 
                 Molten-metal-contacting parts, wear 
                 6 
               
               
                 (Si 3 N 4 ) 
                 Hot Pressing, HIPing 
                 surfaces, 
                   
               
               
                   
                 Reaction bonding. 
                 Special electrical insulators, metal 
                   
               
               
                   
                   
                 forming dies, 
                   
               
               
                   
                   
                 Gas turbine components 
                   
               
               
                 Boron 
                 Hot Pressing (2100-2200 C.), 
                 Fine polishing, abrasive resistant parts 
                 10 
               
               
                 Carbide 
                 Pressureless 
                   
                   
               
               
                 (B 4 C) 
                 Sintering, HIPing 
                   
                   
               
               
                 Titanium 
                 Pressureless sintering 
                 Light weight ceramic armor, nozzles, 
                 9 
               
               
                 diboride 
                 Hot Pressing, HIPing 
                 seals, wear parts, cutting tools 
                   
               
               
                 (TiB 2 ) 
                   
                   
                   
               
               
                 Tungsten 
                 Pressureless sintering 
                 Abrasives, cutting tools 
                 3 
               
               
                 Carbide 
                 Hot Pressing, HIPing 
                   
                   
               
               
                 (WC) 
               
               
                   
               
               
                 Relative cost is on a scale of 1 (low) to 10 (high) for dense material suitable for structural applications. 
               
               
                 Note that gaps in the scale are indicative of large differences in cost. 
               
            
           
         
       
     
     Having described the basic operation of the compaction apparatus with respect to  FIG. 1 , attention is now turned to the particular components of the present invention as illustrated in  FIG. 2 .  FIG. 2  is a cross-sectional view of the components similar to  FIG. 1 , wherein the center pin assembly  34 , in accordance with the present invention, is comprised of a center pin base  40  and a center pin tip  42 . In the preferred embodiment, center pin tip  42  is preferably comprised of a structural ceramic material such as wear resistant ceramic oxides. 
     One such group of suitable wear resistant ceramic oxides is zirconia, which includes the species zirconium oxide, zirconium dioxide, tetragonal zirconia polycrystal (TZP), and partially stabilized zirconia (PSZ). Such partially stabilized zirconia may comprise stabilizers, e.g. yttria (Y 2 O 3 ), magnesia (MgO), calcia (CaO), and ceria (CeO 2 ). A second group of suitable wear resistant ceramic oxides is alumina, also known as aluminum oxide (Al 2 O 3 ) and corundum. A third group of suitable wear resistant ceramic oxides comprises mixtures of zirconia and alumina, including zirconia toughened alumina (ZTA), comprising between about 5 weight percent Zr 2 O 3  and about 40 weight percent Zr 2 O 3 . Further examples of suitable wear resistant ceramic oxides are found in Table 3, along with their relevant physical properties. 
     
       
         
           
               
             
               
                 TABLE 3 
               
             
            
               
                   
               
               
                 PROPERTIES OF WEAR RESISTANT CERAMIC OXIDES. 
               
            
           
           
               
               
               
               
               
            
               
                   
                 DENSITY 
                 STRENGTH 
                 HARDNESS 
                 TOUGHNESS 
               
               
                 MATERIAL 
                 (g/cm 3 ) 
                 (MPa) 
                 (GPa) 
                 (MPa-m 1/2 ) 
               
               
                   
               
               
                 Zirconia 
                 5.9-6.2 
                 400-1400 
                  8-14 
                  5-15 
               
               
                 *Y-TZP 
                 6.0 
                 800-1400 
                 13-14 
                 5-8 
               
               
                 **Y-PSZ 
                 6.0 
                 800-1400 
                 12-13 
                 5-8 
               
               
                 +Ce-TZP 
                 6.1-6.2 
                 1000-1300  
                 11-13 
                 10-15 
               
               
                   x Mg-PSZ 
                 5.9-6.0 
                 400-1100 
                  9-13 
                  6-11 
               
               
                 #Ca-PSZ 
                 5.9-6.0 
                 400-800  
                  9-11 
                 5-9 
               
               
                 ++Ce-PSZ 
                 6.1-6.2 
                 400-800  
                 7-9 
                  6-15 
               
               
                 ZTA 
                 4.1-5.0 
                 300-1600 
                 12-19 
                 3-8 
               
               
                 zirconia 
                   
                   
                   
                   
               
               
                 toughened 
                   
                   
                   
                   
               
               
                 alumina 
                   
                   
                   
                   
               
               
                 5% ZrO 2   
                 4.1-4.2 
                 300-500  
                 15-19 
                 3-5 
               
               
                 20% ZrO 2   
                 4.4-4.5 
                 500-1000 
                 14-17 
                 3-6 
               
               
                 40% ZrO 2   
                 4.8-5.0 
                 500-1600 
                 12-16 
                 4-8 
               
               
                 AZ 
                 5.4-5.6 
                 800-2000 
                 10-15 
                  5-10 
               
               
                 alumina 
                   
                   
                   
                   
               
               
                 strengthened 
                   
                   
                   
                   
               
               
                 zirconia 
                   
                   
                   
                   
               
               
                 80% ZrO 2   
                 5.4-5.6 
                 800-2000 
                 10-15 
                  5-10 
               
               
                 Alumina 
                 3.8-4.0 
                 250-600  
                 15-21 
                 3-4 
               
               
                 99% alumina 
                  3.80 
                 250-350  
                 15-17 
                 3-4 
               
               
                 99.5% alumina 
                 3.8 
                 300-400  
                 17-19 
                 3-4 
               
               
                 99.9% alumina 
                 3.9-4.0 
                 350-500  
                 17-20 
                 3-4 
               
               
                 99.95% 
                 3.9-4.0 
                 350-600  
                 18-21 
                 3-4 
               
               
                 alumina 
               
               
                   
               
               
                 NOTE: 
               
               
                 The wide range in properties is a result of the many different processing methods and raw materials. Typical values are found in the mid range. The best materials are found through head to head property analysis that can differ significantly from ceramic supplier data sheets. 
               
               
                 Note: 
               
               
                 The “stabilizing” additive is a minor addition to the zirconia, but has a significant effect on the hardness and toughness. In general, the higher toughness zirconias have lower hardness. 
               
               
                 *Y-TZP (also called TZP) = Yttria stabilized Tetragonal Zirconia Polycrystal (special case of hard Y-PSZ) 
               
               
                 **Y-PSZ = Yttria Partially Stabilized Zirconia 
               
               
                 +Ce-TZP = Ceria stabilized Tetragonal Zirconia Polycrystal (new material-special case of tough Ce-PSZ) 
               
               
                   x Mg-PSZ = Magnesia Partially Stabilized Zirconia 
               
               
                 #Ca-PSZ = Calcia Partially Stabilized Zirconia (not usually used in wear parts) 
               
               
                 ++Ce-PSZ = Ceria Partially Stabilized Zirconia 
               
            
           
         
       
     
     In one embodiment, center pin tip  42  was fabricated by machining a ceramic tube of zirconia supplied by the CoorsTeck Corporation. Such a tube was supplied in near net shape form, oversized by 0.030 on the outside diameter and undersized by 0.030 inch on the inside diameter. The tube was finished to a 0.250 inch inside diameter and a 1.250 inch outside diameter, using a cylindrical grinding machine tool. 
     In addition to ceramics, other materials are also suitable for the fabrication of a center pin tip, and to be considered within the scope of the present invention. For example, one may use a tip comprised of e.g., silicon carbide, tungsten carbide, titanium nitride, or carborundum. In one further embodiment, a tip comprising a pre-hardened steel sleeve having a diamond impregnated surface may be used. 
     Referring to  FIG. 3A , the center pin assembly  34  includes at least three components. A first component is a center pin base  40 , which is a generally cylindrical component having an aperture  38  in the lower end  39  thereof for controlling the position of the center pin with a shaft of the compaction apparatus (not shown) inserted into the aperture  38 . It will be noted that the present invention contemplates use in any number of compaction tooling machines and that aperture  38  may be replaced by any center pin attachment design, for example, those depicted in  FIGS. 4A ,  4 B, and  4 C. In a first embodiment depicted in  FIG. 4A , aperture  38  is replaced by center beam  38 A. In a second embodiment depicted in  FIG. 4B , aperture  38  is replaced by slot  38 B. In a third embodiment depicted in  FIG. 4C , aperture  38  is replaced by offset beam  38 C. 
     It will be apparent that corresponding mating tools are provided in the drive mechanism (not shown) to properly engage each of these three embodiments and apply an upward axial force thereupon. It will be further apparent that many other suitable configurations of center pin assembly  34  may be used, with the operative requirement being that center pin assembly  34  comprises a surface that is engageable with a mating tool to apply a force along the axis of center pin assembly  34 , as indicated by arrow  36  of  FIGS. 3A-3D . 
     At the upper end  41  of the center pin base  40 , in the embodiment of  FIGS. 3A-3D , is a cylindrical hole  68  that extends into the center pin base  40  for approximately 1.50 inches. Hole  68  may have a depth in the range of 0.500 inches to 2.000 inches. The center pin base is preferably made from tool steel or pre-hardened steel, although various metals and possibly other materials may be employed. The compositions and properties of suitable tools steels and pre-hardened steels are provided on pp. 2069-2095 of  Machinery&#39;s Handbook  22 nd Ed ., the disclosure of which is incorporated herein by reference. 
     Referring again to  FIGS. 3A-3D , a second component of center pin assembly  34  is a ceramic tip  42  that forms the wear surface of the center pin assembly  34 . Ceramic tip  42  is attached to center pin base  40  using a third component, mandrel arbor  44 , preferably made from tool steel or pre-hardened steel. As illustrated, mandrel arbor  44  is generally cylindrical, but includes either a tapered head at an upper end  37  thereof mated with tapered hole in ceramic tip  42 , or a square head mated with counterbored hole in ceramic tip  42 , so as to provide a positive engagement between mandrel arbor  44  and the ceramic tip  42 . 
     In one embodiment depicted in  FIG. 3A , ceramic tip  42  comprises a tapered hole  47 , and mandrel arbor  44  comprises a matching tapered head  45 , which is congruent with tapered hole  47  of ceramic tip  42 , when center pin assembly  34  is fully assembled. In a more preferred embodiment depicted in  FIGS. 3B-3D , ceramic tip  42  comprises a counterbored hole  53  having a shoulder, and mandrel arbor  44  comprises a matching square head  57 , which is congruent with counterbored hole  53  of ceramic tip  42 , when center pin assembly  34  is fully assembled. 
     To affix ceramic tip  42  to base  40 , the components  40  and  42  may be fastened together by a number of joining methods known in the art, such as the methods disclosed in “Mechanical and Industrial Ceramics” published in 2002 by the Kyocera Industrial Ceramics Corporation of Vancouver, Wash. As recited at page 19 of such publication, “Joining Ceramics to Other Materials” bonding methods include screwing, shrink fitting, resin molding, metal casting, organic adhesives, inorganic adhesives, inorganic material glazing, metallizing, and direct brazing. Soldering may also be a suitable joining method. 
     In the preferred embodiment depicted in  FIG. 3A , one end  51  of mandrel arbor  44  is provided with an outside diameter sufficient to provide joining by gluing or by an interference fit with the inside diameter of the hollow or hole  68  in the center pin base  40 . Such an interference fit is preferably achieved by performing a shrinkage fit, wherein base  40  is heated, and expands sufficiently to slide over mandrel arbor  44 . A description of allowances and tolerances for fits between two parts may be found in  Machinery&#39;s Handbook,  22 nd Ed.  pp. 1517-1566, the disclosure of which is incorporated herein by reference. In particular, the assembly of parts by a shrinkage fit is described on pp. 1520-1524. 
     To assemble the center pin assembly  34  by use of a shrinkage fit, two operations are required. In the first operation, mandrel arbor  44  is fitted within ceramic tip  42 . Mandrel arbor  44  may be a slip fit within ceramic tip  42 . In one embodiment, mandrel arbor  44  is an interference fit within ceramic tip  42 . In such an embodiment, either mandrel arbor  44  is cooled, or ceramic tip  42  is heated, or both, and mandrel arbor  44  is inserted through and engaged with ceramic tip  42 , as shown in  FIG. 3A . Assembled ceramic tip  42  and mandrel arbor  44  are allowed to thermally equilibrate with each other and reach approximately room temperature, whereupon such parts are firmly joined with an interference fit. 
     In another embodiment of an interference fit between mandrel arbor  44  and ceramic tip  42 , both mandrel arbor  44  and ceramic tip  42  are maintained at room temperature, and mandrel arbor  44  is “press fit” through ceramic tip  42  using a pressing machine. In another embodiment, mandrel arbor  44  and ceramic tip  42  are joined together using an adhesive. Suitable adhesives are described elsewhere in this specification. Alternatively, mandrel arbor  44  and ceramic tip  42  are joined together by brazing. 
     Subsequent to the formation of an arbor and tip subassembly, the subassembly is joined to base  40 . In one embodiment, base  40  is heated preferably by induction heating means, to expand the diameter of hole  68  therein. The lower end  51  of mandrel arbor  44  extending beyond tip  42  is then press fit into the heat-expanded hole  68 . Once assembled, the assembly  34  may be air cooled or quenched in a synthetic oil or similar liquid to cool the base and to prevent damage to the ceramic from uneven heating. 
     In one embodiment, mandrel arbor  44  was fabricated of Histar  40  pre-hardened steel with a diameter of 0.252 inch at its end  51 . Base  40  was fabricated of Histar  40  pre-hardened steel with an outside diameter of 0.50 inch, and a hole  68  therein of 1.50 inches in length and 0.250 inch in diameter. Base  40  was heated to a temperature of between 600° and 1000° Fahrenheit using induction heater Model No. 301-0114H of the Ameritherm Corporation, Inc. of Scottsville, N.Y. End  51  of mandrel arbor  44  was then immediately slidably inserted into heat-expanded hole  68  of base  40  to a depth wherein the ends of ceramic tip  42  and base  40  were in contact with each other. The resulting assembled center pin assembly  34  was then air cooled to approximately 100° Fahrenheit. 
     In an alternative embodiment, instead of or in addition to an interference fit, mandrel arbor  44  may be attached to the base  40 . In a manner similar to that described above, and referring to  FIG. 3B , mandrel arbor  44  is inserted through the tip  42 , and into hole  68  in base  40 . Once assembled, a retainer pin  48  is inserted through coaxially aligned hole  46  in base  40  and hole  49  in mandrel arbor  44  as illustrated in  FIG. 3B . In one embodiment, it is contemplated that the holes  46  in base  40  and hole  49  in mandrel arbor  44  are not drilled until the components are assembled and mandrel arbor  44  and tip  42  are held in a compressive relationship, thereby assuring a “tight” attachment of the tip  42  to the base  40 . In one embodiment, retainer pin  48  comprises pre-hardened steel of the same composition as mandrel arbor  44  of  FIG. 3B . 
       FIGS. 3C and 3D  depicts alternate embodiments of means for securing mandrel arbor  44  to base  40 . Referring to  FIG. 3C , in one embodiment, center pin assembly  34  further comprises a setscrew  58 , which is threadedly engaged with tapped hole  59 . Tapped hole  59  and the threads therein are formed through both center pin base  40  and mandrel arbor  44 . Thus, it is preferable that in the process of assembly of center pin base  40  and mandrel arbor  44 , mandrel arbor  44  is pressed into center pin base  40 , and tapped hole  59  is formed by drilling and tapping while mandrel arbor  44  and center pin base  40  are forcibly held together, followed by the screwing of setscrew  58  into hole  59 , until setscrew  58  has been forced into the bottom of hole  59 . 
     In one embodiment, setscrew  58  is bonded into tapped hole  59  by a thread locking sealant such as e.g. a cyanoacrylate adhesive. In another embodiment, setscrew  58  is a self locking setscrew, provided with a plastic (e.g. nylon) insert along its threaded length, which is deformed when setscrew  58  is engaged with tapped hole  59 . Such self-locking setscrews are well known in the art. In another embodiment, setscrew  58  is a self locking setscrew, having a coating of microencapsulated beads of reactive resin and hardener, such that when setscrew  58  is threadedly engaged with tapped hole  59 , the shearing action of threads of setscrew  58  with threads of tapped hole  59  rupture and mix the contents of the microencapsulated beads, thereby making an adhesive composition (e.g. an epoxy), which locks setscrew  58  into tapped hole  59 . Such reactive adhesive coatings for the securing of threaded fasteners are well known in the art. 
     Referring to  FIG. 3D , and in further embodiments, a plug  61  of material is engaged with hole  63  to effect the fastening of mandrel arbor  44  to base  40 . As was described for the uses of a setscrew fastener, it is preferable that mandrel arbor  44  is pressed into center pin base  40 , and hole  59  is formed by drilling through base  40  into mandrel arbor  44  while mandrel arbor  44  and center pin base  40  are forcibly held together, followed by the engagement of plug  61  of material with hole  63 . The manner in which plug  61  of material is engaged with hole  63  depends upon the material composition of plug  61 . 
     In one embodiment, plug  61  is a dowel pin, preferably made of a pre-hardened steel of the same composition as mandrel arbor  44  of  FIG. 3B . In such circumstances, plug  61  is dimensioned to have an interference fit in hole  63 , and plug  61  is forcibly pressed into hole  63 . In a similar embodiment, hole  63  is formed in a rectangular shape, and plug  61  is formed from a matching piece of rectangular key stock, and pressed into hole  63 . 
     In other embodiments, plug  61  is engaged with hole  63  by a phase change and/or an alloying operation. Plug  61  may be of the same composition as mandrel arbor  44  and base  40 , so that plug  61  may be welded into hole  63 . Alternatively, plug  61  may be brazed into hole  63 . Plug  61  may comprise a plug of solder, such that plug  61  is heated and melted, and flows into hole  63 , whereupon plug  61  cools and solidifies therein. 
     Alternatively or additionally, adhesives may be used to join mandrel arbor  44  and base  40 . Such adhesives may be applied to the wall surface of hole  68  of base  40 , or the end  51  of mandrel arbor  44  and/or the tapered surface  45  of mandrel arbor  44  (see  FIG. 3A ), or the stepped surface  57  of mandrel arbor  44  (see  FIGS. 3B-3D ), followed by inserting of mandrel arbor  44  into base  40 . 
     Suitable adhesives for such assembly may be e.g. cyanoacrylates, epoxies, and the like, and such adhesives may also include metal and/or ceramic fillers to match properties such as thermal expansion coefficient with those of mandrel arbor  44  and base  40 . One suitable product line of adhesives is manufactured by the Cotronics Corporation of Brooklyn, N.Y. In one embodiment, Cotronics Duralco 4535 Vibration Proof Structural Adhesive was used to join mandrel arbor  44  to base  40 . Other suitable adhesives manufactured by Cotronics are Resbond S5H13 epoxy, Duralco 4540 Liquid Aluminum Epoxy, and Duralco 4703 Adhesive and Tooling Compound. Such adhesives are described in Cotronics Corporation sales bulletin Volume 01 Number 41, “High Temperature Materials and Adhesives for Use to 3000° F.”. Other suitable adhesives used in ceramic-ceramic and ceramic-metal bonding may be used such as e.g., dental adhesives. 
     While many suitable embodiments have been disclosed in the foregoing description, applicants believe that the preferred center pin assembly comprises the embodiment of  FIG. 3B , wherein center pin base  40 , mandrel arbor  44 , and retainer pin  48  comprise tool steel, and tip  42  comprises zirconia ceramic material, and mandrel arbor  44  has a square head  57 , which engages with a counterbored hole  53  of ceramic tip  42 . 
     It will be appreciated that the reworking of the ceramic tip, in the event of wear or damage, can be easily accomplished by pressing retainer pin  48  out of the assembly  34 , replacing the worn ceramic tip  42  and reinstalling the mandrel arbor  44  and retainer pin  48 . A similar reworking method may be employed for the first embodiment, where the interference fit between the base and the mandrel arbor  44  is released by heating the base, thereby allowing mandrel arbor  44  to be pulled from the base. Such a process is believed to be superior to the complete replacement or known stripping, re-plating, and regrinding operations presently used to rework worn metal center pins. Such a process is clearly superior from an environmental, health, and safety standpoint, as the practice of chrome plating requires the use of hexavalent chromium reagent. 
     Referring next to  FIGS. 5A and 5B , there are illustrated two alternative embodiments of the center pin  34 . In the embodiment of  FIG. 5A , the center pin  34  consists of only two components: base  50  and ceramic tip  56 . Base  50  has a shoulder  52  and a shaft  54  extending outwardly beyond shoulder  52 . Ceramic tip  56  is formed as a hollow sleeve or tube, with an outside diameter, and an inside diameter. The shaft  54  of base  50  is made to slidably fit within the inner diameter of ceramic tip  56 . In this embodiment, the ceramic tip  56  may be affixed to shaft  54  by brazing the ceramic to the steel of the base  50  with a brazing compound. Brazing compound flows by capillary forces into the interstice  55  between the surfaces of shaft  54  and ceramic tip  56 . For such purposes, it is believed that Ticusil (Ag 49.7%, Cu 47.2%, Ti 3.1%) or Cusil (Ag 55.4%, Cu 36.5%, Ti 8.1%) brazing compounds sold by Wesgo Metals of San Carlos, Calif. may prove suitable for such brazing of the ceramic tip  56  to the steel shaft  54  of base  50 . A description of the art of brazing and the composition and properties of various brazing compounds is provided on pp. 2197-2204 of  Machinery&#39;s Handbook  22 nd Ed ., the disclosure of which is incorporated herein by reference. 
     In the alternative embodiment of  FIG. 5B , the base  60  is formed as described with respect to base  40  of  FIG. 3A . However, instead of employing an arbor to attach the ceramic tip, the ceramic tip  62  itself includes a shoulder  64  and a shaft  66  extending therefrom. The shaft  66  may be inserted into hole  68  of the center pin base  60  and brazed with brazing compound so as to retain the ceramic tip  62  therein. Brazing compound flows by capillary forces into the interstice  65  between the surfaces of shaft  66  and hole  68 . Alternatively, instead of brazing, it may be possible to produce the shaft  66  and base  50  so as to provide an interference fit between these parts as described above. 
     In a further alternative embodiment shown in  FIG. 5C , the shaft  77  may be produced with a slight negative taper—where the extreme end of the shaft  77  is larger in diameter than the end nearest shoulder  64 , and the diameter of the entire shaft being of a diameter so as to be interference fit with the inside diameter of hollow  68 . Then, in order to assemble the tip  62  to the base  60 , the base is heated, preferably by induction heating, to expand the diameter of the hollow  68  sufficiently to allow the tapered shaft of the tip  62  to slide into the hollow. Once cooled to ambient temperature, the interference fit, or alternatively the taper of the shaft, would serve to hold the ceramic tip in semi-permanent attachment to the base. In this embodiment, it will be appreciated that reworking of a worn tip may be accomplished simply by heating the base  60  to remove the worn tip and inserting a new tip therein, thereby significantly reducing the steps and labor of rework. 
     Alternatively, an adhesive may be used to join ceramic tip  56  and base  50  of  FIG. 5A , or ceramic tip  62  to base  60  of  FIG. 5B . Such adhesives may be applied to the respective tip or base in the same manner as described for the embodiments of  FIGS. 3A-3D , followed by the engagement of the tip with the base. 
     Attention is now turned to  FIGS. 6A and 6B , where a smaller diameter center pin is depicted. The reduced diameter leads to additional considerations in the methods by which the center pin assembly  34  might be produced in order to provide the ceramic tips of the present invention. More specifically, center pin base  70 , has a cylindrical hole  68  that extends into the center pin base for approximately 2.25 inches, but perhaps as far as aperture  38 . Ceramic tip  72  forms the center pin tip so as to provide a wear resistant surface for the center pin assembly  34 . Tip  72  is attached to the base using the mandrel arbor  74  as in the previously described embodiment shown in  FIG. 3A , and an interference fit is used to retain the mandrel arbor  74  therein. Alternatively, in the embodiment depicted in  FIG. 6B , a retainer pin  78  is inserted into hole  76  in the base  70  and hole  79  in mandrel arbor  74  to assemble the center pin assembly  34  as depicted in  FIG. 6B . It is further contemplated, due to the reduced diameter of the top of center pin base  70 , that the mandrel arbor  74  may be extended (and the cylindrical hollow  68  in the base  70  as well) so that the mandrel arbor  74  extends further into the base  70 . Retainer pin hole  76  is correspondingly lower on the base  70 , located in a region where the diameter of the base is somewhat larger than the minimum diameter at the tip, possibly near hole  38 , where the diameter is at a maximum. 
     Alternatively or additionally, an adhesive may be used to join mandrel arbor  74  and base  70  of  FIGS. 6A and 6B . Such adhesives may be applied to mandrel arbor  74  or base  70  in the same manner as described previously for the center pin assembly  34  of  FIGS. 3A-3D , followed by the engagement of mandrel arbor  74  with base  70 . 
     Referring finally to  FIGS. 7A and 7B , there are illustrated two additional embodiments of the reduced diameter center pin assembly  34 . In the embodiment shown in  FIG. 7A , the center pin assembly  34  consists of only two components, a base  80  having a shoulder  82  and a shaft  84  extending outwardly beyond shoulder  82 . The shaft  84  is made to slidably fit within the hole  88  of ceramic tip  86 . In this embodiment, the ceramic tip  86  may be affixed to shaft  84  by brazing the ceramic to the steel of the base  80  (as shown in  FIG. 5A ). For such purposes, it is believed that Ticusil or Cusil (as previously described) may prove suitable for such brazing or soldering so as to bond the ceramic to the steel shaft. It is known that such brazing materials may be used in a sheet or paste form. 
     In the alternative embodiment shown in  FIG. 7B , the base  90  is formed with a cylindrical hollow  98 , and ceramic tip  92  includes a shoulder  94  and a shaft  96  extending therefrom. The shaft may be inserted into the hollow cylindrical region  98  and brazed so as to retain the ceramic tip therein (as shown in  FIG. 5B ). In a further alternative embodiment, the shaft  96  may be produced with a slight negative taper. Then, in order to assemble the tip  92  to the base  90 , the base  90  is heated preferably by induction heating means, to expand the inner diameter of hollow  98  sufficiently to allow the tapered shaft  96  of the tip  92  to slide into the hollow  98 . Once cooled to ambient temperature, the taper of the shaft  96  would serve to hold the ceramic tip  92  in semi-permanent attachment to the base  90 . 
     Alternatively or additionally, adhesives may be used to join shaft  84  and ceramic sleeve  86  of  FIGS. 7A and 7B , in the same manner as recited previously for the center pin assembly  34  of  FIGS. 3A-3D . 
     Alternatively or additionally, an adhesive may be used to join shaft  84  and ceramic sleeve  86  of  FIGS. 7A and 7B . Such adhesives may be applied to the shaft  84  or ceramic sleeve  86  in the same manner as described previously for the center pin assembly  34  of  FIGS. 3A-3D , followed by the engagement of shaft  84  with ceramic sleeve  86 . 
     In all of the preceding embodiments of  FIGS. 3A-7B , in which adhesive is used as to join a base and a tip together, there is formed an interstice (such as e.g. interstice  55  of  FIG. 5A ) between such parts, in which the adhesive (such as e.g. a liquid glue) flows and contacts the surface of such parts. Such an interstice is typically between 0.001 and 0.002 inches wide. In one embodiment, a fixture is used, which coaxially aligns such parts when the male part is inserted into the female part, and maintains such alignment until the adhesive is cured. 
     In another embodiment, a shimming wire is used to provide coaxial alignment of the parts of a center pin assembly.  FIG. 8  is a detailed cross sectional view of an embodiment of the present invention wherein a ceramic tip is joined to a base using adhesive, and wherein a shimming wire is helically disposed on the male part thereof to effect the alignment of such part with the female part. Referring to  FIG. 8 , the upper end of the center pin assembly  34  of  FIG. 5A  is depicted, with ceramic tip  56  shown in cross-section. The front portion of ceramic tip  56  is thus removed, thereby exposing shaft  54  of base  50 . 
     A shimming wire  67  is helically disposed around shaft  54 , beginning near shoulder  52  of base  50 , and ending near the top  43  of ceramic tip  56 . Shimming wire  67  is of a uniform diameter along its length, equal to the width of interstice  55  between shaft  54  and ceramic tip  56 . Thus, shimming wire  67  serves the purpose of maintaining shaft  54  and ceramic tip  56  in coaxial alignment when shaft  54  and ceramic tip  56  are assembled. 
     When shaft  54  and ceramic tip  56  are joined together with an adhesive, such adhesive occupies interstice  55 , and shimming wire  67  maintains the coaxial alignment of shaft  54  and ceramic tip  56  while such adhesive cures. Suitable adhesives may be the same as those described for the embodiments of  FIGS. 3A-3D . 
     Shimming wire  67  is preferably disposed around shaft  54  for at least three full 360 degree turns, along at least half of the length of shaft  54 . In one embodiment interstice  55  has an average width of 0.005 inches; shimming wire has a diameter of 0.005 inches. 
     In the preceding embodiment, shaft  54  is considered to be the male part of center pin assembly, and ceramic tip  56  is considered to be the female part. It is to be understood that the preceding description is also applicable to the center pin assemblies of  FIGS. 3A ,  5 B,  6 A,  6 B,  7 A, and  7 B, wherein the shimming wire is helically disposed around the equivalent male (shaft) part. It is also to be understood that a narrow ribbon of shim stock having a rectangular cross section and a uniform thickness could be substituted for the shimming wire of the preceding embodiments, wherein such shim stock ribbon is helically disposed about the male part of the center pin assembly, thereby achieving substantially the same result. 
     In a further alternative embodiment, mandrel arbor  44  ( FIG. 3A ) or shaft  66  ( FIG. 5B ), or various other mating surfaces as described herein, may include a threaded portion to engage with a threaded mating portion of the base. For example, referring to  FIG. 3A , a lower portion  51  of mandrel arbor  44  may include threads that are screwed into threaded interior region within the base  40 . It is further contemplated that the exposed (top) end of mandrel arbor  44  may then have a slot, hex key or similar mechanism (not shown) to tighten mandrel arbor  44  within the base. Moreover, the use of a retaining pin or similar mechanism may be employed to lock the threaded shaft within the base. 
     In another embodiment, the center pin assembly of the present invention, which comprises a ceramic tip and a base, is joined together with a threaded fastener.  FIG. 9  is a cross sectional view of such an embodiment, in which a threaded fastener is used to join the ceramic tip to the base. Referring to  FIG. 9 , base  50  of ceramic pin assembly  34  is similar to base  50  of  FIG. 5A , but further comprises a threaded hole  69  tapped in the end thereof. Ceramic tip  56  is similar to ceramic tip  42  of  FIG. 3B , comprising a counterbore  53  disposed in the end  43  thereof. A threaded fastener  71  having a square shoulder  73  (such as, e.g. a socket head cap screw) is engaged with threaded hole  69  such that square shoulder  73  bears upon the base of counterbore  53  of ceramic tip  42 , thereby securing ceramic tip  42  to base  50 . 
     In one embodiment, threaded fastener  71  is bonded into tapped hole  69  by a thread locking sealant such as e.g. a cyanoacrylate adhesive. In another embodiment, threaded fastener  71  is a self locking setscrew, provided with a plastic (e.g. nylon) insert along its threaded length, which is deformed when threaded fastener  71  is engaged with tapped hole  69 . Such self-locking screws are well known in the art. In another embodiment, threaded fastener  71  is a self locking screw, having a coating of microencapsulated beads of reactive resin and hardener, such that when threaded fastener  71  is threadedly engaged with tapped hole  69 , the shearing action of threads of threaded fastener  71  with threads of tapped hole  69  rupture and mix the contents of the microencapsulated beads, thereby making an adhesive composition (e.g. an epoxy), which locks threaded fastener  71  into tapped hole  69 . Such reactive adhesive coatings for the securing of threaded fasteners are well known in the art. 
     In the preferred embodiment of  FIG. 9 , the inner diameter of ceramic tip  42  and the diameter of shaft  54  are preferably chosen such that the width of interstice  55  is substantially zero, and ceramic tip  42  requires only a hand press fit to be assembled onto shaft  54 . Thus, by providing a center pin assembly comprising a threaded fastener and ceramic tip that are easily removed by hand, the ceramic tip may be changed while the entire center pin assembly  34  remains installed in the compaction tool. Such a feature is advantageous, because it enables a simple and rapid changeover of ceramic tips, thereby minimizing the cost of downtime of the compaction process of battery manufacturing. 
     Although described relative to the tooling employed for the compaction of battery components, the present invention is intended to include, within its scope, the use of similar techniques to extend the life of other compaction tools and punches, including, but not limited to tablet compaction, powder metal compaction etc. For example, the techniques described with respect to  FIGS. 5A and 5B , and  FIGS. 7A and 7B  may be employed to produce ceramic tips for various compaction punches (upper and lower, etc.) wherein the tips may be manufactured from longer-wearing ceramic components and fitted to the metal punch base. 
     In recapitulation, the present invention is a method and apparatus for the production of compacted powder elements. More specifically, the present invention is directed to the improvement of tooling for powder compaction equipment, and the processes for making such tooling. The improvement comprises the use of a ceramic tip or similar component in high wear areas of the tooling. Moreover, the use of such ceramic components enables reworking and replacement of the worn tool components. 
     It is, therefore, apparent that there has been provided, in accordance with the present invention, a method and apparatus for improving the performance of compaction tooling. While this invention has been described in conjunction with preferred embodiments thereof, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art. Accordingly, it is intended to embrace all such alternatives, modifications and variations that fall within the spirit and broad scope of the appended claims.