Patent Publication Number: US-7914729-B2

Title: Precision notch machining fixture and method

Description:
This is a divisional of U.S. patent application Ser. No. 11/710,143, filed on Feb. 23, 2007, now U.S. Pat. No. 7,641,741. 
    
    
     BACKGROUND OF THE INVENTION 
     Various types of dies for stamping/forming sheet parts from sheet metal have been developed. Such dies are typically custom made to produce a particular part by a skilled tradesman. Numerous components of such dies are often made from hot-roll steel plate. Such components are typically rough-cut from a large plate of hot-roll steel utilizing a flame-cutting process, and the upper and lower surfaces of the plate are ground flat in a “Blanchard” grinder or the like. Die shops typically receive the rough-cut component from the supplier with flat ground parallel upper and lower surfaces, and a rough-cut perimeter having the approximate size and shape of the finished stripper or other such component. In general, hot-roll steel plate and the like can be rough cut more quickly and economically by flame-cutting than by sawing or the like. Thus, flame-cutting the part to the approximate final shape and size reduces the amount of labor by a skilled tradesman that would otherwise be required. 
     Typically, the rough-cut part/work piece must be further machined to form the various openings and other precision-machined features required for the particular die component being fabricated. Such plates often require machining operations to be performed on both the upper and lower side surfaces. To achieve this, the work piece is first clamped to the bed of a machine tool and machined on a first side. After completion of the machining operation on the first side of the part, the part is then flipped over and machined on the other side. The features machined into both sides of the part often need to be located precisely relative to one another, and the process of setting up the plate after flipping it over therefore tends to be time-consuming because the plate needs to be precisely located (“set up”) utilizing the features previously machined into the component. This set-up time results in not only extra labor on the part of the die maker or machinist, but also results in down time for the machine during the set-up operation. 
     Accordingly, a way to alleviate the drawbacks associated with prior arrangements for machining components made of hot-roll steel would be beneficial. 
     SUMMARY OF THE INVENTION 
     The present invention provides a way to quickly and easily secure a piece of hot-roll steel to a machine tool for machining. The part being machined can be machined on a first side and then flipped over for machining on a second side. The fixture/device of the present invention securely holds the part for machining, and also precisely locates the part without conventional manual set-up. The part is made from a piece of hot-roll steel that is cut from a larger sheet or plate of stock utilizing a flame-cutting process. The perimeter of the piece is flame-cut to the required size and shape for the part being made, and one or more locating/supporting features such as notches are flame-cut into the perimeter/edge of the piece. The notches preferably have a U-shape in plan view, and the notches are spaced apart around the perimeter of the piece of steel. 
     A fixture according to one aspect of the present invention is utilized to secure the flame-cut part to a machine tool. The fixture includes an enlarged plate having a flat upper surface with T-slots forming a grid on an upper side of the plate. The plate is secured to a bed of a mill or other machine tool utilizing conventional strap-type clamps or other suitable arrangement. The fixture includes a plurality of support members that are secured to the plate utilizing screws and T-nuts positioned in the T-slots. The support members include a key-type feature that is closely received in the T-slots to thereby prevent movement of the support member in directions transverse to the T-slots. The support members also include slot-engaging portions that are at least partially received in the flame-cut notches of the part to thereby prevent or limit movement of the part relative to the support member. The support members also include protrusions that may be in the form of flanges that have upper and lower surfaces. When the support members are in position, the part rests on the upper surfaces of the protrusions, and the lower surfaces of the protrusions contact the upper surface of the plate. The part is thereby supported away from the surface of the part at a distance equal to the thickness of the protrusions. 
     The fixture includes clamp members that are connected to the support members by bolts or the like. The clamp members engage the surface of the part at the notches and securely clamp the part to the support members. The clamp members have a cut-away portion that provides clearance for machining a small precision notch in the part at each flame-cut notch. 
     After machining on a first side of the part is completed and precision notches are machined at the flame-cut notches, the part is flipped over (i.e. rotated 180° relative to a horizontal axis) and the part is again secured to the plate utilizing the support members and clamp members. The support members include a small protrusion at an end of the notch-engaging portions of the support members having a size and shape closely corresponding to the size and shape of the precision notches. The small protrusions are positioned in the precision notches, and the clamp members are utilized to clamp the part in place on the plate. The small protrusions engage the precision notches and thereby precisely position the part relative to the support members. Because the support members are precisely located on the plate by the key-type feature which is received in the T-slots, the position of the part on the mill is therefore precisely controlled, and the time and effort required to secure and position the part on the second side is greatly reduced. 
     These and other features, advantages, and objects of the present invention will be further understood and appreciated by those skilled in the art by reference to the following specification, claims, and appended drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a partially schematic, fragmentary, plan view of a precision notch device according to one aspect of the present invention; 
         FIG. 2  is a fragmentary isometric view of a portion of the device of  FIG. 1 ; 
         FIG. 3  is a fragmentary isometric view of a work piece showing a large flame-cut notch and a smaller precision notch machined into the work piece; 
         FIG. 4  is a plan view of a work piece showing flame-cut notches in the perimeter of the work piece and machined precision notches machined into the work piece at the flame-cut notches; 
         FIG. 5  is an isometric view of a support member forming a part of the device of  FIG. 1 ; 
         FIG. 6  is a view of the support member of  FIG. 5  taken along the line VI-VI;  FIG. 5 ; 
         FIG. 7  is an isometric view of a clamp member forming a part of the device of  FIG. 1 ; and 
         FIG. 8  is a view of the clamp member taken along the line IIX-IIX;  FIG. 7 . 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENT 
     This application is related to co-pending U.S. patent application Ser. No. 11/709,951, filed on Feb. 23, 2007, entitled MODULAR TOOLING SYSTEM AND METHOD, the entire contents of which are incorporated herein by reference. 
     For purposes of description herein, the terms “upper,” “lower,” “right,” “left,” “rear,” “front,” “vertical,” “horizontal,” and derivatives thereof shall relate to the invention as oriented in  FIG. 1 . However, it is to be understood that the invention may assume various alternative orientations and step sequences, except where expressly specified to the contrary. It is also to be understood that the specific devices and processes illustrated in the attached drawings and described in the following specification are simply exemplary embodiments of the inventive concepts defined in the appended claims. Hence, specific dimensions and other physical characteristics relating to the embodiments disclosed herein are not to be considered as limiting, unless the claims expressly state otherwise. 
     A precision notch device  1  ( FIG. 1 ) according to one aspect of the present invention includes a plate member  2  having a flat upper surface  3  and a plurality of T-slots  4 . T-slots  4  have an upside-down T-shaped cross sectional shape to receive T-nuts (not shown) of a type that is generally well-known in the art. A plurality of retainers  10  engage flame-cut notches  11  in a work piece/part  12  to retain the part  12  on the plate member  2  via T-nuts received in grooves or slots  4 . Part  12  may be made of hot-roll steel, and includes a perimeter  13  that is formed by flame-cutting the part  12  from a larger plate of hot-roll steel. Upper and lower surfaces  14  and  15  of part  12  are precision ground flat surfaces. The plate member  2  may be secured to a bed  21  of a mill  20  or other machine tool utilizing a conventional strap-type clamp (not shown) or other suitable securing arrangement. The machine tool  20  may be a CNC mill, conventional mill, or other suitable machine tool having an appropriate capacity and capability for the machine operations to be performed on part  12 . It will be understood that machine tool  20  may comprise any one of a variety of machine tools or the like as required for a particular application. With further reference to  FIG. 2 , each T-slot  4  includes parallel side surfaces  16  that are formed within a high tolerance such that the width of the upper portions of T-slots  4  is held to a relatively high tolerance. Also, the positions of the T-slots  4  is also within a relatively high tolerance. 
     Each retainer  10  includes a support member  30  and a clamp member  50  that is operably interconnected to the support member  30  by a movable member such as socket head cap screw  29 . Support members  30  include a body portion  31  (see also  FIGS. 5 and 6 ) having first and second ends  35  and  36 , respectively, and flat, parallel opposite side surfaces  32 . End  35  includes a curved end surface  33  that extends between the side surfaces  32 . Portions of the side surfaces  32  and end surface  33  together define a notch-engaging portion  34  of support members  30  that is received in flame-cut notches  11  of part  12 . 
     Each retainer  10  also includes a downwardly-extending key  37  having parallel opposite side surfaces  38  that define a dimension therebetween that is equal to, or slightly smaller than, the width of T-slots  4  defined by the distance between surfaces  16  of T-slots  4 . As shown in  FIG. 2 , key  37  is closely received in T-slots  4  to thereby position support members  10  relative to plate  2 . 
     Referring again to  FIGS. 5 and 6 , support members  10  include protrusions  39  having a flange-like shape with flat upper surfaces  40  that are parallel to flat lower surfaces  41 . In use ( FIG. 2 ), a lower surface  22  of part  12  contacts upper surfaces  40  of protrusions  39  of support members  30 , and lower surfaces  41  of protrusions  39  contact upper surface  3  of plate  2 , such that lower surface  22  of part  12  is spaced apart from surface  3  a distance equal to the thickness “T” ( FIG. 6 ) of protrusions  39 . 
     Support members  30  include counter-bored openings  42  ( FIG. 5 ) that receive threaded fasteners or the like (not shown) that securely interconnect/clamp support members  30  to T-nuts (not shown) that are positioned in T-slots  4  of plate  2 . Support members  10  also include a threaded opening  43  that receives cap screw  29  ( FIG. 2 ) to clamp the clamp members  50  to support members  30  and thereby clamp part  12  in place on support members  30 . 
     Support members  30  include a small, precise, bullet-shaped protrusion  45  ( FIG. 5 ) extending from curved end surface  33 . Protrusion  45  includes a precisely-formed vertical surface  46  having a curved end portion  47  and flat opposite side portions  48 . Vertical surface  46  extends orthogonally from upper surface  40  of protrusion  39 , and ends at corner  49  formed at the intersection of vertical surface  46  and a top surface  44  of small protrusion  45 . As described in more detail below, surface  46  has substantially the same size and shape as precision notch  60  ( FIG. 3 ) to thereby position and retain part  12  on support members  30 . 
     Clamp members  50  ( FIGS. 7 and 8 ) include a lower key portion  51  with opposite side surfaces  52 . Key portions  51  are received in flame-cut notches  11  to position clamp members  50 . Because the flame-cut notches  11  have relatively rough flame-cut surfaces, the size and shape of notches  11  tends to vary somewhat. Accordingly, key portions  51  are sized to provide a loose fit in notches  11 . Clamp members  50  define lower surface portions  53  that contact upper surface  23  ( FIG. 2 ) of part  12 , and a counter-bored opening  54  that receives screw  29 . End  55  ( FIG. 7 ) of clamp member  50  includes a pair of extensions  56  with a cut-away portion  57  between extensions  56 . Cut-away portion  57  provides clearance to machine precision notches  60  ( FIG. 3 ) into part  12  adjacent flame-cut notches  11 . Lower surfaces  53  preferably extend to the extensions  56  to provide a clamping force on surface  23  of part  12  in the vicinity of extensions  56 . 
     Referring back to  FIGS. 1 and 2 , in use, a part  12  having flame-cut notches  11  pre-formed in perimeter  13  is positioned on plate  2  with notch-engaging portions  34  of support members  30  of retainers  10  positioned in flame-cut notches  11 . Clamp members  50  are then positioned above support members  30 , and screws  29  are tightened to thereby clamp part  12  to the support members  30 . Support members  30  are held in position on plate  2  by cap screws (not shown) that engage T-nuts (also not shown) that are positioned in T-slots  4  of plate  2 . 
     Various openings and other features are then machined into part  12  as required, and precision notches  60  (see also  FIGS. 3 and 4 ) are machined into part  12  at flame-cut notches  11 . Although precision notches  11  could take many forms, in the illustrated example notches  11  have side surfaces  61  that are orthogonal to upper surface  23  of part  12 , and base surface  62  that is parallel to upper surface  23 . 
     After the machining operations are completed on a first side of part  12 , the screws  29  are loosened to release part  12 , and part  12  is flipped over. Small protrusions  45  of support members  30  are then positioned in precision notches  60 , and screws  29  are tightened to clamp part  12  to support members  30  and plate  2 . The keys  37  of support members  30  securely and accurately position support members  30  on plate  2 , and small protrusions  45  engage precision notches  60  of part  12  to accurately position part  12  on support members  30 . Part  12  is thereby accurately positioned and retained for machining on a second side of part  12 . 
     In the foregoing description, it will be readily appreciated by those skilled in the art that modifications may be made to the invention without departing from the concepts disclosed herein. Such modifications are to be considered as included in the following claims, unless these claims by their language expressly state otherwise.