Abstract:
The invention relates to an improved method and apparatus for manufacturing metal parts, preferably surgical blades ( 1 ), using bandoliering with die stamping and machining processed material at stations on the die. The method allows for cost efficient mass production while maintaining a high level of precision.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The invention claims priority to provisional application US60/718,027 filed on Sep. 15, 2005, the content of which is incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The invention relates to apparatus and methods for manufacturing precision metal parts by using a combination of machining and progressive dies. 
       BACKGROUND 
       [0003]    Bandoliering is commonly employed in manufacturing when using progressive dies. Starting material may be attached to a single or double bandolier at certain spacing. It allows for the mass production of metal objects using die stamping by carrying the metal object through a die automatically for processing. Although the process allows for the mass production of fabricated metals, it is not efficient for manufacturing precision devices such as surgical blades for several reasons including: 1) the process is cost prohibitive due to high tonnage requirements and interrupted flow of material, and 2) the products of metal stamping using dies are not as precise and have inferior surface finish compared to machined parts. The present invention addresses these problems by a method making it possible to mass produce precision devices or parts such as surgical blades by bandoliering using progressive dies. 
       SUMMARY OF THE INVENTION 
       [0004]    The present invention is directed to a method and apparatus for manufacturing precision metal parts, preferably surgical blades, that fulfills the considerations stated above. The method uses a bandolier to which the blade material is attached. The blade material is formed at various stations in one or more progressive dies. The first station coins the blade material to the correct volume leaving excess material unrestricted. The excess material is trimmed away to the correct volume of the finished blade cross section. The second station coins only the top of the blade material leaving the bottom flat to promote material flow. The edges of the blade material are coined to a thickness that matches the finished product at this station. The third station reforms the blade material to the net shape whereupon tools for machining radii on the ends of the blade material are applied. 
         [0005]    The method of the present invention has the advantages of mass production of precision parts with machined edges and superior surface finish with little variation between parts that cannot be achieved by machining or progressive die stamping alone. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]    The invention will now be further elucidated by way of exemplary embodiments that form no limitation to the appended claims, and with reference to the following drawings. 
           [0007]      FIGS. 1A-1C  illustrates a finished surgical blade, the preferred embodiment of the product manufactured by the claimed process. 
           [0008]      FIG. 2  is a schematic diagram of the progressive die apparatus. 
           [0009]      FIGS. 3A-3B  is a plan view of the first coining station. 
           [0010]      FIGS. 4A-4B  is a plan view of the second coining station. 
           [0011]      FIGS. 5A-5B  is a plan view of the third coining station. 
           [0012]      FIGS. 6A-6C  are elevation and plan views of finished surgical blades attached to the bandolier. 
           [0013]      FIG. 7  is a schematic diagram of machining tools for forming machined edges on the finished surgical blades. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0014]    Referring now to the drawings in detail, wherein like reference numerals indicate like elements throughout the several views, there is illustrated in  FIG. 1A-1C  a surgical blade  1 , the preferred embodiment of the product produced by the claimed process. The die tooling described below manufactures the blade  1  attached to the uncoined handle  2  through several coining and trimming processes to obtain the final dimensions of the desired blade width  3  and thickness  4  and edge thickness  5 . The finished blade  1  is capable of bending 90 degrees up and down across the narrow section ( 6   a  and  6   b ) without breakage. 
       Die Apparatus 
       [0015]      FIG. 2  shows a schematic diagram of a progressive die in accordance with an embodiment of the present invention. Wire stock  7  enters the die and is cut to length by a cutting apparatus  8 . The metal blank  9  cut from the wire stock  7  is attached to a bandolier  10  at a portion of the metal blank  9  that will not be coined. The bandolier carries the metal blank  9  to the first coining station  11  wherein the metal blank  9  is coined to a thickness thinner than the finished thickness  4  in one hit. The excess material is restricted and the bandolier  10  carries the metal blank  9  to the second coining station  12  where the thickness of the edges of the metal blank  9  are coined to the thickness of the finished product  5 . The bandolier  10  then carries the metal blank  9  to the third coining station  13  which reforms the metal blank  9  to it final shape of the surgical blade  1 . The finished blades  1  may remain on the coiled bandolier  10  for further processing. 
       First Coining Station 
       [0016]    The bandolier  10  carries the metal blank  9  to the first coining station  11  comprising an upper coining die  11   a  and a lower coining die  11   b  as shown in  FIG. 2 .  FIG. 3A  illustrates the first coining station wherein a portion of the metal blank  9  is coined to the correct volume and excess material is restricted.  FIG. 3B  shows the profile of the metal blank  9  following action of the first coining station  11  wherein the metal blank  9  is coined into an hourglass (convex) configuration  14 . The thickness  15  of the metal blank  9  is thinner than the thickness  4  of the finished product  1  in one hit. Coining by one hit reduces the effect of work hardening the material and reduces the tonnage required for coining at subsequent stations. Moreover, the first coining station is shaped with a radius having an area  16  for the material to flow and polished to further facilitate material to flow out from the center  17 . It is preferred that upon action of the first coining station  11  the thickness  15  of the metal blank is at least 75% of the thickness  4  of the finished product. The thickness  15  of the metal blank  9  having the hourglass configuration  14  facilitates the flow of material back to the center  17  at subsequent coining stations allowing greater precision in forming the edges of the finished product. Upon completion of the action at the first coining station  11 , excess metal material is trimmed away from the metal blank  9  and the resulting cross section of the metal blank is equal to the cross section of the finished product. The bandolier  10  then carries the metal blank  9  to the second coining station  12 . 
       Second Coining Station 
       [0017]    The second coining station  12  of the progressive die comprising an upper coining die  12   a  and a lower coining die  12   b  is show generally in  FIG. 2  and in greater detail in  FIG. 4A . The upper coining die  12   a  is shaped to provide the correct final cross section area and to promote the flow of material to the center  17 . The lower coining die  12   b  is flat to promote material flow.  FIG. 4B  shows the profile  18  of the metal blank  9  following action of the second coining station  12  wherein the edges  19  have a thickness  5  that matches the thickness of the finished product  1 . The bandolier  10  then carries the metal blank  9  to the third coining station  13 . 
       Third Coining Station 
       [0018]    The third coining station  13  of the progressive die comprising an upper coining die  13   a  and a lower coining die  13   b  is shown generally in  FIG. 2  and in greater detail in  FIG. 5A . The third coining station  13  reforms the metal blank  9  to the final shape and required dimensions.  FIG. 5B  shows the profile  20  of the finished product  1 . The first and second coining stations  11  and  12  established the conditions allowing the flow of material to the center  17  at the third coining station  13  providing the desired edge thickness  5  and blade thickness  4 .  FIGS. 6A-C  show the finished blade  1  mounted on a typical bandolier  10  at the blade handle  2 . The bandolier  10  containing the finished blades  1  may be coiled for subsequent processing. 
       Machining Tools 
       [0019]    The bandolier  10  secures and provides control to the product so the manufacturer can automate additional manufacturing steps such as machining. Machining tools capable of forming machined edges with a well-defined surface finish may be applied to the finished blades  1  following processing at the third coining station  13 .  FIG. 7  shows machining tools that may be comprised of an electronic or air operated spindle  21  that turns a carbide cutting tool  22 . The spindle  21  may be mounted on a slide  23  moved by a cam  24  with a profile that drives in the spindle  21  at a rate per tooth controlled by the spindle rpm and dwells the correct amount at the end of the stroke. This tooling allows for machining radii on the ends of the product produced. The addition of a machining process allows for greater precision in parts with machined edges and a surface finish that would be difficult to achieve using die stamping alone. 
       Additional Processing 
       [0020]    The bandolier assembly may also facilitate the automation of other processes including plating specific portions of the blade  1  with gold or other secondary operations such as cleaning and/or assembly. 
         [0021]    The progressive die of the present invention, which replaces the hand-operated, single-hit methods, allows for mass production of precision metal instruments exhibiting a high degree of flexibility and consistency in edge characteristics. This automated, progressive approach increases production that allows precision metal instruments to be produced more efficiently and effectively reducing variance resulting in superior quality. The reduced tonnage requirements described above increase the life span of the dies and allow use of lighter, less expensive parts resulting in even greater cost savings.