Abstract:
A method of finishing a workpiece is disclosed. The method includes the use of a container, preferably a drag finishing machine to displace a workpiece or part about a substantially vertically oriented axis. The workpiece is immersed in a media and an abrasive that adheres to the media via surface tension of a liquid disposed in the container or drag finisher. The workpiece is then displaced and the workpiece contacts or impacts the abrasive to provide the desired finishing. The abrasive may move from media to media as it is loosely attached via the surface tension of the liquid.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     This invention generally relates to a method for finishing parts. More particularly, this invention relates to displacing a workpiece within and relative to media and an abrasive.  
         [0002]     U.S. Pat. No. 5,251,409 discloses a method of drag finishing a housing that comprises lowering a workpiece or housing into media. When the housing is in the media, the housing is revolved in a first rotational direction about a vertical axis and also moved in first angular direction about a vertical axis. Then the housing is also revolved in a direction opposite to the first rotational direction, and moved in a second angular direction.  
         [0003]     U.S. Pat. No. 6,261,154 discloses a method and apparatus for media finishing. The workpiece or wheel is angularly displaced while being rotated about an oblique angle.  
         [0004]     Advances in the drag finishing arts include the method of moving a workpiece relative to the tub and media within the tub. The prior art also includes processes that utilize media and abrasive additives in vibratory and barrel finishing machines.  
         [0005]     Processes utilizing media and abrasives or abrasive additives have been used in the past in vibratory and barrel finishing processes to refine the surfaces and smooth the surfaces of parts or workpieces. Use of the vibratory or barrel finishing processes may be useful to reduce the surfaces of about 5 micro-inches to about 50 micro-inches. This process may take about 10 hours to 20 hours to complete.  
         [0006]     A drag finishing process has been used to recover the surfaces of workpieces that incurred surface degradation or surface roughness of about 10 RA micro-inches to about 15 RA micro-inches, from a prior operation, for cosmetic or bearing surface purposes.  
         [0007]     As can be seen, there is a need for improved apparatus and methods in the media that is disposed in the tubs used in the drag finishing apparatus and method. There is a need to reduce (1) processing costs, (2) the amount of media used, (3) the amount of solids (effluent) required to be treated, (4) disposal costs of the used media solids (effluent), (5) the amount of solids that are required to be sent to a land fill, and (6) multiple step finishing operations. There is also a need to accelerate the finishing and stock removal rate.  
         [0008]     There is also a need to reduce surfaces from between about 150 RA micro-inches to about 5 RA micro-inches. Surface roughness can be measured by a profilometer, which is a stylus device used to trace across the surface profile. The results are expressed either as RA, which is the arithmetic average deviation from the center line of the surface, or as RMS, which is the root mean square of the deviations from the center line. RA or RMS values are given in either microns (same as micrometers or μm) or micro-inches (μ). Typically RMS may be about 11 percent higher than the RA number for a given surface.  
       SUMMARY OF THE INVENTION  
       [0009]     One aspect of the present invention is a method of finishing a workpiece, comprising: providing a container; providing a media disposed within said container; providing an abrasive disposed within said container, said abrasive capable of adhering to said media to form a media-abrasive mixture; and displacing the workpiece within said media-abrasive mixture.  
         [0010]     Another aspect of the present invention is a method of finishing a workpiece, comprising: providing a drag finishing machine; providing a media disposed within said drag finishing machine; providing an abrasive disposed within said drag finishing machine, said abrasive capable of adhering to said media to form a media-abrasive mixture; and displacing the workpiece within said drag finishing machine.  
         [0011]     Another aspect of the present invention is a method of finishing a workpiece, comprising: providing a container; providing a media disposed within said container; providing an abrasive disposed within said container, said abrasive capable of adhering to said media to form a media-abrasive mixture; and displacing the workpiece within said container.  
         [0012]     These and other features, aspects and advantages of the present invention will become better understood with reference to the following drawings, description and claims. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]      FIG. 1  illustrates a perspective of one exemplary embodiment of a container;  
         [0014]      FIG. 2  illustrates an abrasive and a media forming a media-abrasive mixture; and  
         [0015]      FIG. 3 , illustrates the steps of the process of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0016]     The following detailed description is of the best currently contemplated modes of carrying out the invention. The description is not to be taken in a limiting sense, but is made merely for the purpose of illustrating the general principles of the invention, since the scope of the invention is best defined by the appended claims.  
         [0017]     The process of the present invention utilizes the combination of (1) a media  20  and (2) an abrasive  30 .  
         [0018]     The process involves displacing a workpiece  10  relative to the media  20  and abrasive  30 . The media  20 , abrasive  30 , and workpiece  10  are disposed in a container  40 . In one exemplar embodiment of the present invention, the container  40  is a drag finisher.  
         [0019]     In one exemplary embodiment, the media  20  may be either a preformed media  20 , a random media  20 , a metallic media  20 , or it may be a cast shape or a metal punching. One exemplary embodiment of the preformed media  20  is preformed ceramic media  20  or a preformed porcelain media  20 .  
         [0020]     As a workpiece  10  is displaced within the media  20 , the media  20  exerts pressure on the abrasive  30 , which contacts the workpiece  10  for finishing as the workpiece  10  moves through and past the media  20 . The media  20  acts as a carrier for the abrasive  30 . The cutting or metal removal function may be caused by the media  20  carrying or grinding the abrasive  30  between the media  20  and the workpiece  10 . The media  20  may contact the workpiece  10  and cause incidental finishing. The abrasive  30  may have one or a plurality of sharp edges  60  that are used to finish the workpiece  10 .  
         [0021]     In one exemplary embodiment the abrasive  30  or abrasive additive  30  may be a fused aluminum oxide, silicon dioxide, diamond powders, zirconia, or quartz. The types of abrasives  30  can be altered to achieve the desired effects and assist in the efficiency of the process. The abrasive  30  size may vary depending on the desired breakdown rate of the abrasive  30 . The breakdown rate is its effective life of usefulness as an abrasive  30 . Throughout use the abrasive  30  may become smoother. In other words, the abrasive  30  in its new or virgin state may be more aggressive and may impart a deeper cut pattern into the workpiece  10  surface. However, as the loose abrasive  30  wears down, its cutting ability may be reduced, which may impart a smoother surface or a shallower cut or scratch into the workpiece  10 . In one exemplary embodiment of the present invention the abrasive  30  may have an ANSI grit size of about 150 grit or coarser. In one exemplary embodiment, the ANSI grit size by be about 60 to about 220. The abrasive  30  may be either dry or viscous.  
         [0022]     In one exemplary embodiment of the present invention, renewal of the cutting ability through out the process cycle may be accomplished by either a periodic or a continuous addition of the abrasive  30  or abrasive additive  30  to the media  20 . In one exemplary embodiment of the present invention the abrasive  30  may be added either continuously or intermittingly, and then addition of the abrasive may cease towards the end of the process cycle, to allow coarser abrasives to wear down or erode, thus imparting a smoother finishing as the size of the abrasive  30  degrades or becomes finer. In one exemplary embodiment of the present invention, one may start the process cycle with coarser abrasives to provide for faster stock removal than the prior art, and then add finer or different abrasives  30  towards the end of the process cycle.  
         [0023]     It may be important to use the media  20 , or media mass  20  with respect to the final finishing capability of the abrasive  30  characteristic of the preformed media  20 , media  20 , or media mass  20 . This may be because the content level of the abrasive  30  of the media  20  may allow the final step or steps of the process cycle to achieve the desired surface condition of the workpiece  10 . This may also be because the shape of the media  20  may provide the maximum efficiency for the media  20  to carry the abrasive  30  to contact the workpiece  10  or part  10 .  
         [0024]     In one exemplary embodiment of the present invention the abrasive  30 , additive  30 , or abrasive additive  30  may adhere to the media  20  by the surface tension created by the addition sufficient amounts of a liquid  50 , such as water  50  or a finishing compound  50 .  
         [0025]     In one exemplary embodiment of the present invention, the media  20 , abrasive  30 , and workpiece  10  may be disposed in a container  40 , whereby the workpiece  10  may be displaced to create a force between the abrasive  30  and the workpiece  10 . The abrasive  30  may adhere to the media  20  via the surface tension of a liquid  50 . Some abrasive  30  may be loose, i.e. may not be adhered to the media  20 . In one exemplary embodiment of the present invention the container  40  may be a high energy machine  40 , such as a plunge machine  40 . In one exemplary embodiment of the present invention the container  40  may be a drag finisher  40 . In one exemplary embodiment, the drag finisher  40  may be a machine that has a “Lazy Susan”-like spinner, which has a series of parts hanging on stations or fixtures below. The spinner then lowers the workpiece  10  into the media  20 -abrasive  30  mixture as the workpiece  10  moves or revolves, or it can held statically and displaced around a vertical axis, into a bed of media  20 -abrasive  30  mixture that is contained in an annular ring bowl. As the workpiece  10  “plows” through the media  20 -abrasive  30  mixture, the process accomplishes its prescribed or desired work objective, depending on the selected media  20  and abrasive  30 . The drag finishing machine  40  and process may accomplish the desired pressure and velocity by displacing the workpiece  10  relative to the container  40  at velocities or angular velocities of about 300 to about 500 or more feet per minute. In one exemplary embodiment of the present invention utilizing a drag finisher  40  may speed up the finishing process by about 20 to about 40 times as compared with a vibratory finisher. For example, what may take only about less than two hours when using a drag finisher may take 24 hours or more when using a vibratory finisher.  
         [0026]     The present invention may use different types of containers  40 . In one exemplary embodiment of the present invention, the container  40  may pull, push, or drag the workpiece  10  in either a statically held position or in a rotational movement through the media  20  and abrasive  30 .  
         [0027]     In one exemplary embodiment of the present invention, desired material removal or metal removal is accomplished by proper sizing of the abrasive  30  or the abrasive additive  30 . In one exemplary embodiment of the present invention, a surface having about 150 RA micro-inches to about 5 RA micro-inches may be smoothly finished.  
         [0028]     To remove the abrasive  30  from the media  20 , copious amounts of liquid  50 , such as water  50 , may be added, which may break the surface tension and rinses the abrasive from the container  40  via a drain (not shown).  
         [0029]     The steps of the present invention include providing a container  100 , providing a media disposed within said container  200 , providing an abrasive disposed within said container  300 , and displacing the workpiece within said media-abrasive mixture  400 . In one exemplary embodiment of the present invention, the steps need not take place in any specific order.  
         [0030]     It should be understood, of course, that the foregoing relates to exemplary embodiments of the invention and that modifications may be made without departing from the spirit and scope of the invention as set forth in the following claims.