Abstract:
A process for retruing a profile in an abrasive wheel is provided. A lathe table including an edged cutting tool is used for fixturing a grinding wheel having an outside metal edge and an abrasive matrix adjacent thereto for rotation along an axis compatible for lathe removal of material at at least the outside edge of said wheel. A predetermined amount of material along said edge with the edged lathe cutting tool is removed using the lathe cutting tool. A rotating electrical discharge profiling tool which is attached to an electrical discharge machine is used for profiling of the wheel by electrical discharge machining of the abrasive surface with the rotating electrode. The process uses a machine specifically designed for electrical discharge machining of the profile. The machine also has a mechanism cutting a predetermined profile into the electrode without removing it from the machine.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 62/168,172, filed May 29, 2015. The disclosures of the above application are incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to retruing of diamond grinding wheels. 
       BACKGROUND OF THE INVENTION 
       [0003]    Diamond grinding wheels with abrasive grit matrix cutting surfaces sandwiched between outer steel walls are commonly used in glass edging operations. In recent years these wheels have become useful in edging contours in solar energy panels where precision grinding is essential. The cost of solar panels is high due to the value added processes during production. In addition, any quality issues with the edge profile grinding wheels has become more critically problematic than in the past, such as when edge grinding a more decorative surface of a glass table top, automobile lights, window or even an ophthalmic lens. 
         [0004]    Because of the quantity of solar panels being produced and the ever increasing cost of diamond grit materials, retruing of out of specification diamond matrix profiling wheels has become an important function in the manufacture of precision ground solar panels and the like. 
         [0005]    Past methods or retruing the wheels typically involve using an abrasive grit grinding wheel to remove the outside metal material and rough profile of a grinding wheel and thereafter to re-profile the proper grove or edge cutting pattern into the matrix. 
         [0006]    This process has generally been acceptable. However, the wheels resurfaced by this process and the cost of grinding wheels for retruing is problematic. 
         [0007]    Therefore, there remains a need in the art to provide a more precise, cost effective process for retruing of edge profiling grinding wheels which provides superior service capabilities for edge grinding of solar panels and other glass surfaces. 
       SUMMARY OF THE INVENTION 
       [0008]    A process for retruing a profile in an abrasive wheel is provided. A lathe table including an edged cutting tool is provided. A grinding wheel is operably fixtured, the grinding wheel having an outside metal edge and an abrasive matrix surface adjacent thereto for rotation along and axis compatible for lathe removal of material on at least the outside edge of said wheel. A predetermined amount of material along the edge of the grinding wheel is removed with the edged lathe cutting tool. The process further includes providing a rotating electrical discharge profiling tool attached to an electrical discharge machine (“EDM”), for rotating the profiling tool along an axis in a direction to provide electrical discharge profiling of the abrasive matrix surface of the wheel. Then profiling of the wheel by electrical discharge machining of the abrasive matrix surface with a rotating electrode. 
         [0009]    The process uses a machine specifically designed for electrical discharge machining of the profile. The machine has parallel rotating axes for simultaneous rotation of a wheel to be trued and an electrode having a profile for retruing of the surface of the wheel. The machine also has a mechanism for contacting of the discharge machine electrode cutting surface and cutting a predetermined profile into the surface. This provides a simpler electrical discharge machine for this purpose which provides a precise electrode surface which can be reformed or touched up without removing and replacing the electrode in the machine. 
         [0010]    The process is equally applicable for abrasive wheels with only one side wall being steel. However, explained herein is a process where both sides of the wheel are steel, aluminum, copper, steel, stainless steel or alloys of these with a profiling surface in between. 
         [0011]    Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein: 
           [0013]      FIG. 1  is a perspective view of a pencil edging wheel of the type retrued in the present invention; 
           [0014]      FIG. 2  is a side view showing the abrasive surface of the wheel with contour lines showing the abrasive contour of the wheel; 
           [0015]      FIG. 3  is a detailed sectional view of the wheel of  FIG. 2 ; 
           [0016]      FIG. 4  is a perspective view of the wheel being edge machined on a lathe as a first step of the present process; 
           [0017]      FIG. 5  is a front perspective view of a wheel getting retrued in accordance with the teachings of the present invention; 
           [0018]      FIG. 6  is a rear perspective view of the machine which illustrates the profile forming of the electrode; 
           [0019]      FIG. 7  is a perspective view similar to  FIG. 6  showing profiling of the graphite electrode; 
           [0020]      FIG. 8  is a figure showing electrode profiling tools useful in the present invention; 
           [0021]      FIG. 9  is a side view of another pencil edging wheel of the type retrued in the present invention; and 
           [0022]      FIG. 10  is a detailed sectional view of the wheel of  FIG. 9 . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0023]    The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. 
         [0024]    A typical edge profiling wheel is show generally at  10  or “wheel” in  FIGS. 1-3 . The wheel includes a central mounting orifice  12  which mounts to an arbor for rotating the wheel about an axis A-A. The wheel  10  has outer sides  14  and  16  which are metal, preferably, steel, and an abrasive matrix material  18  which is a sintered metal abrasive grit matrix at the outer peripheral edge  20  of the wheel  10 . At this outer peripheral edge  20  the steel sides  14  and  16  have a thickness “a” and the matrix has a concave working profile section  22  with outer peripheral edges having a thickness “b”. During use of the wheel  10  the working surface  22  becomes worn such as to a “V” like surface configuration shown at  24  or otherwise worn. When the wheel  10  becomes worn the working surface  22  must be retrued to the original profile such as that shown at  26 . Along with this retruing, the outer peripheral profile is reduced by a distance “c” to form outer steel walls  28  and  30  and abrasive matrix walls  32  and  34  and the profiling surface  26 . In the present invention the wheel  10  is retrued using the process as follows. 
         [0025]    Referring now to  FIG. 4 , a lathe device shown generally at  36  or “lathe table” or “lathe” is provided that is operable to take off the width “a” to a depth “c” steel from the outer sides  14  and  16  of the wheel  10  to form the surfaces  28  and  30 . The lathe  36  can be used to take off material from the sides one side at a time or both sides at once from either an axial or longitudinal direction. The steel sides  28  and  30  of the wheel  10  are the only parts which are removed by the lathe process. The lathe process removes the majority of the steel without disturbing the more sensitive matrix  18  material. While it depends on the extent of the wear in the abrasive wheel  10 , generally the dimension “c” is from 10 to 100 thousandths of an inch and typically 50 to 70 thousandths of an inch. 
         [0026]    The lathe  36  includes at least one edged cutting tool  38  with at least one cutting edge  38   a  to cut off part of the wheel  10  as the wheel  10  is held by an opposing edge  38   b.  The cutting edge  38   a  is operably shaped and located to take off the predetermined depth and dimensions (i.e., “a” and “c”) from the wheel  10  to form the respective one of the surfaces  28  and  30  as the wheel  10  rotates. According to another embodiment, at least two cutting edges  38   a  and  38   b  are operably shaped and located to take off the predetermined depth and dimensions (i.e., “a” and “c”) from the wheel  10  to form the both surfaces  28  and  30  at the same time as the wheel  10  rotates. The cutting edge  38   a  portion is connected by at least one fastener  39 , according to an embodiment of the invention, and is removable to change out for maintenance, repair or when a different cutting surface configuration is desired depending on the application. 
         [0027]    Referring now to  FIGS. 5 and 6 , a specialized electric discharge machining apparatus shown generally at  40  or “machine” is provided and includes an electrical discharge profiling tool  42  or “electrode”. The electrical discharge machine  40  is configured for controlled rotation along the first axis A-A of the profiling wheel  10  to be retried. The machine  40  is adapted for rotation of the profiled electrode  42  in a parallel axis B-B such that the electrode  42  can be contacted to the wheel  10  to be profiled. Thus, the machine  40  is adjustable for aligning the electrode  42  with the wheel  10  and then moving the electrode  42  toward the wheel  10  while both are turning and the electrical discharge is on to provide machining of the surface. The electrode  42  has an outer circumferential profile shown generally at  43  for contacting the profile to be retrued of the abrasive wheel  10  by electrical discharge machining. In the present invention the apparatus  40  has an electrode reforming apparatus shown generally at  44  in  FIGS. 6 and 7  which is diametrically opposed to the contact point of the electrode  42  with the wheel  10 . The electrode reforming apparatus  44  includes at least one table  46  which is moveable by a handle  48  toward and away from the electrode  42 . At least one cutting tool mechanism  50  or “cutting tool” is secured to the table  46 , e.g., by a plurality of fasteners, and is adapted for selectively contacting and reforming the contour of the electrode  42  by moving the cutting tool  50  into engagement with the electrode  42  to provide a predetermined contour in the electrical machining surface of the electrode  42 .  FIG. 8  illustrates various profiling tools  50   a,    50   b,    50   c  which are used depending on the type of wheel being retrued by the electrode  42 . It is appreciated that the cutting tool  50  can be positioned in alternative orientations depending on the application such as with the cutter edge upward or angled at 6 degrees. 
         [0028]    As will be appreciated by those skilled in the art a graphite electrode  42  is used and is oversized and generally from 8 to 12 inches in diameter. This allows the profile of the electrode  42  to be touched up, re-profiled or even reshaped many times without changing the electrode  42  which is a time consuming process. The electrode  42  can be made of other materials such as copper, steel or alloy materials which are useful as electrodes in EDM machining. 
         [0029]    Referring to the figures generally, in accordance with the present invention there is provided a process for retruing a profile  26  in an abrasive wheel  10  which has the steps of: first providing a lathe table  36  including an edged cutting tool  38 . As stated above the cutting tool  38  is used to cut off a portion “c” of the material from the steel side of the wheel  10 . The process is equally applicable for cutting wheels with only one side wall being steel (such as shown in  FIGS. 9 and 10 ). The wheel  10  is mounted in the lathe  36  for rotating the wheel  10  and the cutting tool  38  is used to remove material from the steel for a distance “a” inward and a distance “c” downward. This can be done one side at a time or both sides at a time in a radial or axial direction. 
         [0030]    Next a rotating electrical discharge profiling electrode  42  is attached along axis B-B parallel to axis A-A and aligned with the outer peripheral edge of the abrasive wheel  10 . The wheel  10  is attached to an electrical discharge machine  40 , for rotating the profiling tool along an axis in a direction to provide electrical discharge profiling of the abrasive surface of the wheel  10 ; and, profiling of the wheel  10  by electrical discharge machining of the abrasive surface  18  with the rotating electrode  42  while the wheel  10  prepared by the lathe process is also rotated is then accomplished using standard EDM machining processes to provide a finished retrued abrasive wheel with a new spec profile. EDM coolant  52  is used to remove the swarf generated by the process. 
         [0031]    The machine  40  provides adjustment of rotation and current to the electrode  42  and also rotation speed to the abrasive wheel  10 . There is also an adjustment for bringing the working surface of the electrode  42  and the working face  18  of the abrasive wheel  10  into contact with one another to provide the proper distance for EDM machining. Thus, the operator must select the proper combination of rotations, gap and current to be used to provide the proper finished profile. A finished profile can typically be achieved in one rotation of the abrasive wheel  10  using the present process. It will be readily appreciated that while the process shows use with a concave abrasive surface any contour and convex surfaces may also be machined using the process of the present invention. Thus, any type of glass cutting wheels normally used in glass for various applications in windows table tops or other uses may be retrued using the process of the present invention. 
         [0032]    Another typical edge profiling wheel is shown generally at  100  or “wheel” in Figures. The wheel  100  is substantially the same as the wheel  10 , however, the abrasive matrix material  118  profile is different and there is only one outer wall  116 . Any other type of profile style and outer wall configurations, contours and profiles depending on the application are within the scope of the present invention. 
         [0033]    The wheel  100  includes a central mounting orifice  112  which is mountable to an arbor for rotating the wheel a  100 . The wheel  100  has one outer side  116  which is steel and an abrasive matrix material  118  which is a sintered metal abrasive grit matrix (e.g., sintered diamond matrix) at the outer peripheral edge  120  of the wheel  100 . At this outer peripheral edge  120  the steel side  116  has a thickness “a” and the matrix  118  has a concave working profile section  122  with outer peripheral edges having a thickness “b”. During use of the wheel  100  the working surface  122  becomes worn such as to a “V” like surface configuration shown at  124  or otherwise worn configuration. When the wheel  100  becomes worn the working surface  122  must be retrued to the original profile such as that shown at  126 . Along with this retruing, the outer peripheral profile is reduced by a distance “c” to form outer steel wall  130  and abrasive matrix wall  134  and the profiling surface  126 . In the present invention the wheel  100  is retrued using the process as described previously. 
         [0034]    The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.