Abstract:
A method of fabricating a gear is disclosed. The method may include loading a donut blank onto a pallet through a bore in the donut bank. The method may further include loading the pallet and donut blank onto a plurality of different machines and performing a plurality of different machining processes on the donut blank to fabricate a gear.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application is based upon and claims the benefit of priority from U.S. Provisional Application No. 60/950,090 to Dodd filed on Jul. 16, 2007, the entire contents of which are incorporated herein by reference. 
     
    
     TECHNICAL FIELD 
       [0002]    The present disclosure relates generally to a method of gear manufacturing, and more particularly, to a method of manufacturing gears in low lots. 
       BACKGROUND 
       [0003]    The manufacturing of gears normally includes a series of fabrication stations and machines used to perform various steps of the manufacturing process. These may include a forge, hobbing machines, chamfering machines, finishing machines, and any number of other machines for working with gears. For example, a gear blank may be forged at the beginning of the process, and moved from machine to machine, each machine performing a specific manufacturing process on the gear blank, and ultimately producing a finished gear. 
         [0004]    A current method of manufacturing a gear involves forging a gear blank and then chucking that blank on an outside diameter while turning to semi-finish a central bore and one axial face. The gear may then be turned around and chucked on the internal bore to finish a second face. After the two axial faces are finished, the gear may be removed and chucked on the internal bore while the teeth slots are roughed by a hobbing machine. Following a lab check to ensure accuracy, the gear may be removed and chucked internally onto another machine for tooth finishing. Another lab check may follow and then the gear may be hardened by carborizing and quenching. The hardened gear may then be chucked on the tooth flanks using a pitch line chuck to hard finish the bore and faces. 
         [0005]    One of the problems associated with such a method of manufacturing a gear is the tendency for alignment errors introduced by the multiple chucking, unchucking, and re-chucking of the gear blank to different machines. If the blank is not accurately chucked each time to preserve a commonly aligned axis, the bore and/or teeth may not be in concentric alignment with the gear blank, requiring the gear to be discarded as scrap metal, or if used in a machine, increasing the risk of machine malfunction and/or premature wear. Further, this inaccuracy requires the gear to be chucked on the tooth flanks using a pitch line chuck during bore and face finishing, since it cannot be assured that the outer diameter of the teeth will always be concentric with the teeth profile and/or the bore. Lastly, using this method of manufacturing a lot of custom gears may take as long as twelve weeks from receiving the specific order to shipping the custom manufactured gears. 
         [0006]    One method of accelerating the manufacturing process and increasing production accuracy is U.S. Pat. No. 5,181,375 (the &#39;375 patent) issued to Thurman et al., which discloses a method for producing gears. The method of the &#39;375 patent includes forging a gear blank with roughly shaped teeth slots, and then performing various grinding operations to the tooth root and flank surfaces to produce a final finished shape. The method further includes grinding the teeth slots to their final finished profile before heat treating and hardening the gear. By completely grinding the teeth slots before heat treating the gear, the &#39;375 patent seeks to reduce production time and relax any imposed stresses resulting from prior gear fabrication processes. 
         [0007]    The method of the &#39;375 patent may provide a manufactured gear in less time than previous methods, but the multiple grinding operations may increase the likelihood of alignment errors. Further, the multiple grinding operations may still require substantial non-value added time for work holding changes. 
         [0008]    The disclosed method is directed to overcoming one or more of the problems set forth above. 
       SUMMARY 
       [0009]    In one aspect, the present disclosure is directed to a method of fabricating a gear. Specifically, loading a donut blank onto a pallet by chucking the pallet through a bore in the donut blank and then loading the pallet and donut blank onto various machines to shape the donut blank into a gear. 
         [0010]    In another aspect, the present disclosure is directed to a method of manufacturing a gear. The method includes securing the outside diameter of a puck blank, turning a bore in the center of the puck blank to create a donut blank, chucking the donut blank through the bore to a pallet, loading the pallet on a turning machine and turning a axial face or a radial surface, and unloading the pallet from the turning machine. 
         [0011]    In yet another aspect, the present disclosure is directed to a gear fabrication station for producing a gear from a donut blank. The gear fabrication station includes a pallet that mechanically secures the donut blank to allow machining on at least one axial face and a radial surface and a machine having a work-holding unit configured to mechanically secure the pallet to the machine. 
         [0012]    In still another aspect, the present disclosure is directed to a gear fabrication station for producing a gear from a gear blank. The gear fabrication station includes an edge rounding station for edge rounding the intersection of teeth profiles and axial faces, wherein the edge rounding station includes a moving media bath. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]      FIG. 1  is a pictorial view of a bar stock and puck blank according to one embodiment of the disclosure; 
           [0014]      FIG. 2  is a pictorial view of a puck blank manufactured according to one embodiment of the disclosure; 
           [0015]      FIG. 3  is a pictorial view of a donut blank manufactured according to one embodiment of the disclosure; 
           [0016]      FIG. 4  is a pictorial view of a gear blank manufactured according to one embodiment of the disclosure; 
           [0017]      FIG. 5  is a pictorial view of an exemplary manufactured gear according to one embodiment of the disclosure; and 
           [0018]      FIG. 6  is a flow chart of one embodiment of the disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0019]      FIG. 1  illustrates a bar stock  10  from which a puck blank  20  may be cut using a saw (not shown) or any other method known in the art. Bar stock  10  may include a steel alloy cylinder of a predetermined size. The predetermined size may relate to the desired final dimensions of the manufactured gear  50  of  FIG. 5 .  FIG. 2  illustrates puck blank  20 . Puck blank  20  may include a first face  21 , a second face  22 , and an outer diameter  23 . 
         [0020]      FIG. 3  illustrates a donut blank  30 . Donut blank  30  may include a first turned face  31 , a second turned face  32 , an outer diameter  33 , and a standard bore  34 .  FIG. 3  also illustrates a pallet  35  according to one embodiment of the disclosure. Pallet  35  may include a mandrel which mechanically secures donut blank  30  or a gear blank  40  from within standard bore  34  by expanding one or more collets  36  in response to an applied force. The applied force may be provided by a spring, hydraulic system, manually, or any other method of applying force known in the art. Pallet  35  may further be adapted to be mechanically secured to a machine (not shown) to allow machining of donut blank  30  or gear blank  40 . The machine may include a work table having a quick change system, clamp, or any other such work-holding unit known in the art. Pallet  35  may allow the donut blank  30  to be moved to a plurality of machines without the need to load and center the donut blank  30  each time.  FIG. 4  illustrates a gear blank  40 . Gear blank  40  may have a first face  41 , a second face  42 , a standard bore  43 , a plurality of teeth slots  44 , and an outer diameter  45 . Teeth slots  44  may include a root  441 , a flank  442 , and an outer diameter  443 . 
         [0021]      FIG. 5  illustrates an exemplary manufactured gear  50  according to one embodiment of the disclosure. Gear  50  may include a first finished face  51 , a second finished face  52 , finished bore  53 , and a plurality of finished teeth slots  54 . Teeth slots  54  may include a root  541 , a flank  542 , and an outer diameter  543 . As used herein, the term “gear” includes a structure having teeth slots  54  that transmit motion by a combination of rolling and sliding actions along flanks  542 . 
         [0022]      FIG. 6  illustrates steps of the disclosed gear manufacturing method. As shown, one may begin by cutting puck blank  20  from bar stock  10  (step  602 ). This puck blank  20  may then be chucked on the outer diameter  23  while a first face  21  may be machined and a standard bore  34  may be machined in the center of puck blank  20  to one of a plurality of standard cylinder process bores (step  604 ), thus creating donut blank  30 . Donut blank  30 , having a first turned face  31  and a standard center bore  34 , may then be unchucked and moved to pallet  35  (step  606 ). 
         [0023]    Pallet  35  may be configured to hold donut blank  30  from within standard bore  34 , with first turned face  31  facing the pallet. Pallet  35 , with donut blank  30  attached, may next be loaded onto a turning machine to turn outer diameter  33  and second turned face  32  (step  608 ). Pallet  35 , with donut blank  30  attached, may then be unloaded from the turning machine and transferred to a tooth roughing machine (step  610 ). 
         [0024]    Tooth roughing machine may first rough one tooth slot  44  with one or more of a small set of gashing cutters that may be positioned relative to the donut blank  30 . After roughing one tooth slot  44 , an in-process validation may be conducted to determine if the finishing stock envelope will be correct. An exemplary finishing stock envelope may be selected to balance the time required between the tooth roughing and the tooth finishing. If corrections are required, the corrections may be suggested to the operator by inspection software. The operator may then correct machine settings and continue with roughing all teeth slots  44 . It may also be contemplated that teeth slots  44  may be roughed through a hobbing process or any other teeth roughing process known in the art. After all teeth slots  44  are roughed, a post process validation of the finishing stock envelope and tooth spacing may be measured to verify the expected results. If corrections are required for tooth spacing, the corrections may be suggested to the operator by the inspection software. Pallet  35  and gear blank  40  are then unloaded from the tooth roughing machine and loaded onto a tooth finishing machine (step  612 ). 
         [0025]    The starting radial position for finishing teeth slots  44  may be automatically determined by the finishing stock envelope measured after the tooth roughing operation. One tooth slot  44  may be finished slightly short of the desired end size. After one tooth slot  44  is finished, an in process validation may be conducted to determine if flank  442  and slot  44  are correct in size, dimensions, and orientation. If the in process validation reveals that corrections may be required, the inspection software may suggest corrections to the operator. The operator may then accept and correct machine settings and continue with finishing all teeth slots  44 . After all teeth slots  44  are finished, pallet  35  and gear blank  40  may then be unloaded from the tooth finishing machine. 
         [0026]    Next, pallet  35  and gear blank  40  may be washed to remove any particles remaining from the previous machining operations (step  614 ). After washing, gear blank  40  may be removed from pallet  35  and transferred to a part marking machine (step  616 ). The operator may use the part marking machine to mark a part number on one of first or second finished face  41 ,  42 . The part number may be stamped below root  441  of teeth slots  44 . 
         [0027]    Gear blank  40  may further be transferred to an edge rounding station where gear blank  40  may be placed into a moving media bath to edge round the intersection of flanks  442 , roots  441 , outer diameters  443 , and first and second faces  41 ,  42  (step  618 ). In one exemplary aspect, the moving media bath may consist of a vibrating table which supports a spring mounted tub containing ceramic stones and a liquid, such as mild acid. The tub and table may vibrate rapidly in response to a moving eccentric weight attached to the table. As the tub and table vibrate, the mild acid may oxidize a thin layer of the gear blank  40 , particularly on the gear edges. The oxidized layer may be worn away by repeated collisions with the ceramic stones moving in response to the vibration caused by the moving weight. Over the course of one hour and after many repeated collisions, the edges of the part may become sufficiently rounded. 
         [0028]    After the edges have been rounded, gear blank  40  may be removed from the edge rounding station and chucked on outer diameter  45  (step  620 ). Bore  43  and at least one turned face  41 ,  42  may be soft machined to a pre-heat treat finished dimensions. Further, bore  43  and one of first and second turned faces  41 ,  42  may be semi-finished, thus creating finished bore  53  and one of finished first and second faces  51 ,  52 . Gear blank  40  may then be un-chucked and then re-chucked with the other of first and second faces  41 ,  42  facing outward. The outward facing first or second face  41 ,  42  may then be semi-finished, creating the other of first and second finished faces  51 ,  52 . After finished bore  53  and finished faces  51 ,  52  are semi-finished, a post process inspection may be conducted to confirm the correct size and form have been produced. Gear blank  40  may then be un-chucked and hardened by carborizing and quenching (step  622 ). 
         [0029]    After the hardening process, gear blank  40  may again be chucked on outer diameter  45  on a machine that may hard turn and grind finished bore  53  and finished faces  51 ,  52  (step  624 ). Finished bore  53  and finished faces  51 ,  52  may then be rough machined by hard turning. After this hard turning, an in-process validation may be used to verify that the desired dimensions are correct. Further, finished bore  53  and finished faces  51 ,  52  may be finish ground and then inspected to confirm the correct size, form, and surface finish have been produced. 
         [0030]    Next, if tooth hard finishing is required (step  626 ; yes), gear blank  40  may be reloaded onto pallet  35  (step  628 ) and pallet  35  may be loaded on to a tooth-grinding machine (step  630 ). One tooth slot  54  may be finished slightly short of the desired size and an in-process validation conducted to determine if tooth flank  542  will be correct. If the in process validation reveals that corrections may be required, the inspection software may suggest corrections to the operator. The operator may then accept and correct machine settings and continue with hard finishing all teeth slots  54 . A post process inspection may then be conducted to confirm tooth form and spacing are within a specified range. 
         [0031]    Pallet  35  may then be unloaded from the tooth-grinding machine (step  632 ) and transferred to an unchuck station where finished gear  50  may be removed from pallet  35  and washed. After being washed, gear  50  may be transferred to a burn inspection station (step  634 ). At the burn inspection station, teeth slots  54 , finished bore  53  and finished faces  51 ,  52  may be inspected for grinder burn. 
       INDUSTRIAL APPLICABILITY 
       [0032]    The disclosed method for manufacturing gears may be applicable in any gear manufacturing facility where the ability to create custom sized gears quickly and accurately is desired. The disclosed method may provide custom manufactured gears in a consistent, waste-reducing, lower cost configuration. 
         [0033]    According to the disclosed gear manufacturing method, the frequency of unchucking and rechucking donut blank  30  and gear blank  40  may be reduced, and based on the accuracy of finished gears  50  may be increased as alignment errors are reduced. Further, concentricity of outer diameter  45 , teeth roots  441 , teeth flanks  542 , and bore  43  provided by the disclosed method, gear blank  40  may be chucked on outer diameter  45  rather than in teeth slots  44  during bore and face finishing. Further, because the disclosed method uses standard bore  34  and pallet  35  for securing donut blank  30  and gear blank  40  while transferring between various processes, the time elapsed from receiving a specific order to shipping the custom manufactured gears and may be reduced, along with a reduction in the cost of work-holding tooling. 
         [0034]    It will be apparent to those skilled in the art that various modifications and variations can be made to the disclosed method. Other embodiments will be apparent to those skilled in the art from consideration of the specification and practice of the disclosed method. It is intended that the specification and examples be considered as exemplary only, with a true scope being indicated by the following claims and their equivalents.