Abstract:
A method of altering an insert blank by disposing one or more of four shapes at a predetermined location on the blank to provide at least one sharpened edge. The blank can be either a new insert or one that has been dulled and is due to be discarded. The four shapes are a compound shape, a radius and flank shape, a bias helical shape and a helical rake shape. The bias helical shape and the helical rake shape can be either positive or negative. The radius and flank shape can be either concave or convex. The shapes can be ground on a blank using standard grinding machinery.

Description:
RELATED APPLICATIONS 
     This is a continuation of U.S. patent application Ser. No. 08/720,459 titled REMANUFACTURED CUTTING INSERT, filed on Sep. 30, 1996, now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to cutting inserts that are installed in a tool holder and intended to be thrown away after becoming dull and, in particular, to cutting inserts upon which one or more of four specific shapes are disposed at predetermined locations to provide enhanced performance. 
     2. Description of the Related Art 
     The use of cutting tools having replaceable cutting inserts began as long ago as 1917, when Fred P. Lovejoy invented the use of replaceable blades in order to obtain the economic advantages of having to replace only the dull portion of the tool, not the entire tool itself. 
     The next major improvement was the invention of the tungsten titanium carbide insert by Philip M. McKenna in 1938, especially for use in milling machines. A typical milling machine is an apparatus that features a rotating mill head having a number of indexable cutting inserts, where the rotating head is passed over the workpiece to remove material (chips) from the workpiece. A “chip” refers to the material that is removed during the cutting process. Ideally, the chips produced should be broken into pieces as small as possible since large chips can interfere with the cutting operation and are dangerous to workers. 
     Since the time of the invention of the carbide cutting insert, tremendous efforts have been made to understand the myriad factors effecting the performance of cutting inserts. These factors include insert geometry, insert construction, cutting temperature, cutting forces, workpiece material characteristics, and, particularly, chip control. 
     Kennametal, Inc., founded by inventor Philip McKenna, lists thousands of insert geometries/size/composition/coating combinations and permutations in order to meet the requirements of differing applications. 
     Inserts can be manufactured in various ways. The most common basic materials are tungsten carbide or tungsten titanium carbide combined with a metallic binder such as cobalt. It is also possible to construct inserts from ceramic material. These are referred to as Cermet. Various thin film coatings can be applied to the surface of the cutting insert. Examples of common thin film coatings are titanium nitride, aluminum oxide, chromium nitride, titanium carbo-nitride, titanium aluminum nitride and diamond. Coatings are used to improve the performance and durability of the insert. Each material/coating combination has a particular application to which it is most suited. 
     In addition to material choices, various basic geometric shapes can also be selected. The most common are the square, triangle, diamond rhomboid, rectangle, hexagon and round. Added to this complexity is a choice of fifteen different clamping options, five different cutting edge forms, dimension tolerance classification, insert thicknesses, etc. 
     Some inserts have only one sharpened edge suitable for cutting, however, most indexable inserts have a plurality of cutting edges. Once a particular cutting edge has become dull, the insert is indexed in its holder to expose a new cutting edge. Once all cutting edges are dull, the insert is believed to be useless and is thrown away. 
     All of the above are incorporated into a standardized insert identification system which enables a customer to accurately order any one of more than a million possible combinations and permutations to meet a particular need. Despite the overwhelming number of insert variations that are available, standard inserts still are “standardized”. A new insert&#39;s shape, type, size and coating are designed to serve many applications. 
     In spite of the development of sophisticated technology and vast improvements in the durability and cutting efficiency of cutting inserts and the cost increases commensurate with such advances, cutting inserts are still defined and treated as “throw-away”, even in the USA Standard Indexable Inserts for Cutting Tools (B94.25-1969). 
     An example of efforts to improve the cutting efficiency of inserts is found in U.S. Pat. No. 5,372,463, issued to Takahashi et al. on Dec. 13, 1994. In this patent entitled Throw Away (emphasis added) Insert, it is disclosed that the use of an arcuate small protrusion on the bisector of the nose of the cutting surface will improve chip breaking capabilities of the insert. 
     U.S. Pat. No. 5,405,711, issued to Noggle on Apr. 11, 1995, is representative of the effort being made to find better materials to construct the insert. Noggle discloses the use of polycrystalline composites to encase the cutting edges of carbide inserts. The polycrystalline material may be diamond, boron nitride or other similar materials. This particular design is said to make the entire insert indexable since the polycrystalline material is presented as a cutting edge around the periphery of the insert. 
     Still another approach to the improvement of the geometry of the insert is disclosed in U.S. Pat. No. 5,388,932, issued to DeRoche et al. on Feb. 14, 1995. This design is said to provide an efficient positive rake angle when the insert is secured in the milling cutter body. 
     Pantzar et al. disclose in U.S. Pat. No. 5,421,679, issued on Jun. 6, 1995, the use of a grinding operation intended to be used only along an area against a locating surface of a machine tool. Pantzar et al. disclose that inserts requiring a very high degree of dimensional accuracy have been met by after-grinding the surface(s) adjacent to the cutting edge after the insert is sintered. However, it is said that this grinding (called contour grinding) causes adverse modifications in the micro-geometry of the insert. This invention discloses modification of tool attachment surfaces for improving fit within the tool and avoiding the cutting surfaces. 
     As disclosed by Pantzar et al., it has been a commonly held truism in the art for more than 45 years that inserts cannot be sharpened once dull without damaging the geometry of the insert. Consequently, this is the reason for the mistaken belief that the inserts must be thrown away once dull. 
     This belief has been reinforced by failed efforts to regrind used inserts to gain additional useful life before the insert must be discarded. The most ambitious of the regrinding attempts to reclaim dulled inserts, frequently referred to as “down-sizing”, is provided by North American Carbide, Inc. of Broken Arrow, Okla. In this process, the “scrap”/used insert is reground using specially adapted grinding machinery so that an insert that is virtually identical to the original, only slightly smaller is obtained. Unfortunately, the success of this process has been rather limited. Since the reground insert is smaller than the original, the reground insert does not fit accurately in the original tool holder. Since the reground insert is smaller overall, the inscribed circle is also reduced. Inscribed circle is defined as the largest internal circle that can be drawn such that all sides of the insert are tangent to that circle. This can sometimes be countered by the use of shims, however, the use of shims then complicates the installation process. Many companies initially embraced this concept, recognizing the significant financial advantage of being able to increase the life span of an insert. However, the difficulties sometimes encountered with clamping the inserts to fit accurately in the tool holder once it had been refurbished quickly diminished the enthusiasm for the approach. Consequently, the belief that cutting inserts are only capable of a one time use and then must be thrown away continues to prevail after all these years. 
     A method of remanufacturing a cutting insert, either using a new insert or a dulled insert, that will provide sharpened edges with cutting performance equal to or exceeding a new insert and that will provide an insert which can be held in a tool holder without the use of shims or special holders is not known in the prior art. 
     SUMMARY OF THE INVENTION 
     The invention is a set of unique shapes, one or more of which are disposed at predetermined locations on either a worn insert or new insert to sharpen and improve the cutting edge(s). A worn insert or a new insert that is to be remanufactured will be referenced as a blank. While the shapes are intended primarily to be disposed on a worn insert, these shapes, when disposed on new inserts, improve the cutting efficiency and life expectancy of the insert. Instead of throwing away a dull insert, it can now be recycled for significant cost and energy savings. The volume of worn inserts in the waste stream can be reduced by 50%. Most importantly, the insert can be customized for a user&#39;s particular requirements by selecting a combination of one or more of the shapes and by selecting a particular angular configuration 
     One or more unique shapes are disposed at predetermined locations on an insert to produce the final sharpened edge. The shapes are: a compound shape using three angles from 0 to 45 ground on the top of the insert; a concave or convex shape ground on the insert radius and part of the adjacent flanks; a positive or negative helix ground at a bias angle on the top of the insert; and a positive or negative helical rake ground on a plane with the top edge of the insert. The compound shape is disposed on the top rake of a blank and comprises a rotational angle and two substantially equal wing angles. It is preferred that rotational angles be between 0° and 25°, with 10° being optimum in many applications, and wing angles be between 5° and 30°. The radius and flank shape is disposed on the radius and part of the adjacent flanks of the blank. It is preferred that the radius and flank shape comprise a runout angle that is greater than an angle formed between the adjacent flanks of the blank and that the shape further comprise either a concave or convex shape along the radius. The bias helical shape is disposed at a bias angle on the top edge of the blank such that the length from the center of the blank to the starting point of the bias helical shape is less than or equal to {fraction (1/16)} th  of one inch. It is preferred that the bias helical shape be formed at a bias angle between 15 and 45 degrees and at a helical radius equal to a length of the cutting edges, with an optimum being between 0.1 and 2.0 inches. In addition, in some embodiments the top rake of the blank is angled between five degrees and negative five degrees. The helical rake shape is disposed on the top rake of the blank and comprises a helical radius disposed tangent to a minimum depth. 
     These special shapes are not symmetrical to one or more planes of the insert but rather combine to provide a set of cutting angles and edge forms. The result is a sharpened and improved cutting edge optimized for specific cutting applications. 
     It is, therefore, an aspect of the invention to provide cutting inserts from blanks that have one of four unique shapes disposed upon the cutting insert to provide a sharpened edge. 
     Another aspect of the invention is to provide a way of customizing a cutting insert to a particular need given the user&#39;s machinery and material that is to be cut. 
     It is still another aspect of the invention to provide cutting inserts having more than one of four special shapes disposed at predetermined locations on the cutting insert to provide a sharpened edge. 
     Other aspects and advantages of the present invention will become apparent and obvious from a study of the following description and the accompanying drawings which are merely illustrative of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an isometric view of a typical rhomboid-shaped insert that has been remanufactured from a blank using the compound shape in accordance with the invention. 
     FIG. 2 is a top plan view of the insert of FIG.  1 . 
     FIG. 3 is a side view of the insert of FIG.  1 . 
     FIG. 4 is an isometric view of the insert of FIG. 1 identifying surfaces that are not ground to prevent clamping problems with the remanufactured cutting insert. 
     FIG. 5 is an isometric view of a typical diamond-shaped insert that has been remanufactured using the radius and flank shape in accordance with the invention. 
     FIG. 6 is a side view of the insert of FIG. 5 showing a concave radius and flank shape. 
     FIG. 7 is a side view of the insert of FIG. 5 showing a convex radius and flank shape. 
     FIG. 8 is a top plan view of the insert of FIG.  5 . 
     FIG. 9 is an isometric view of a typical parallelogram-shaped insert that has been remanufactured using the bias helical shape in accordance with the invention. 
     FIG. 10 is a top plan view of the insert of FIG.  9 . 
     FIG. 11 is a front plan view of the insert of FIG.  10 . 
     FIG. 12 is a side view of the insert of FIG. 9 showing the change in the top rake in the ground area. 
     FIG. 13 is a top plan view of the insert of FIG. 9 showing locating surfaces required to position the insert in the holder and that cannot be ground. 
     FIG. 14 is an isometric view of a typical square shaped insert that has been remanufactured using the helical rake shape in accordance with the invention. 
     FIG. 15 is a side view of the insert of FIG.  14 . 
     FIG. 16 is a top plan view of the insert of FIG.  14 . 
     FIG. 17 is an isometric view of the insert of FIG. 14 showing the clamping area and the locating area that cannot be ground. 
     FIG. 18 is an isometric view of a typical insert using both the compound shape combined with the radius and flank shape. 
     FIG. 19 is an isometric view of a typical insert using radius and flank shape combined with the bias helical shape. 
     FIG. 20 is an isometric view of a typical insert using helical rake shape combined with the radius and flank shape. 
     FIG. 21 is an isometric view of a typical triangular-shaped insert using the radius and flank shape. 
     FIG. 22 is an isometric view of a typical round insert using the helical rake shape. 
     FIG. 23 is an isometric view of a typical rectangular insert using the bias helical shape. 
     FIG. 24 is a graph of tool action for a typical insert as supplied by the manufacturer. 
     FIG. 25 is a graph of tool action for the same insert of FIG. 24 after it has been remanufactured in accordance with the invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The inventor has discovered that cutting inserts, irrespective of the basic geometry, clamping type, coating or absence thereof, indexable or single edged, and other myriad possibilities that go into making the cutting insert, can be remanufactured using one or more of four unique shapes to remanufacture the insert so that it can be used again. In fact, the inventor has found that by using one or more of these shapes on new inserts, the performance is substantially better than the originals. Each of the respective four shapes is shown and described with an insert having the basic geometry that is most suited for that shape. However, as will be appreciated by those skilled in the art, more than one of the shapes described herein can be applied to any particular specified insert. To more fully explain the shapes, ground surfaces that are provided to achieve the particular shape will be shown cross-hatched with parallel lines, while critical surfaces that cannot have material removed (to ensure that clamping will not be a problem) are shown shaded. 
     FIG. 1 is an isometric view of a typical rhomboid-shaped insert  120  that has been remanufactured from a blank using the compound shape  124  in accordance with the present invention. As is shown in FIGS.  2 - 4 , compound shape  124  is achieved by grinding rotational angle  12  and wing angles  16 , from 0° to 45° on the top rake  126  of the insert  120 . The preferred angle for each application depends on a number of factors. While a gross adjustment can be estimated using the criteria discussed below, the precise best choice for any particular cutting index will necessitate an optimization using an empirical approach until the desired results are achieved. Among the most important considerations are the following factors. 
     The size of the machine that the insert is to be used on will effect the angle selection. Other machine factors include such criteria as feed rates, machine horsepower, depth of cut, heat control, coolant systems, etc. Smaller machines generally require the use of a greater angle (higher wing), that is, more positive. Wing angle refers to the angle between the face of the cutting tool and the work. The work holding system is also an important consideration. The more rigid the clamping system that is utilized, the higher the wing angle that can be used. Tool rigidity also plays a role in the selection of the proper angle. The greater the extension of the tool holder and potential flexing, the less rake that can be used. Cutting edge preparation also plays an important role in the angle selection process. Most edges on inserts are pre-dulled in a process referred to as “honing”. An edge that has not been pre-dulled can fracture and prematurely fail. 
     The workpiece itself must also be considered. As a rule of thumb, soft materials such as aluminum require the use of greater wing angles, typically ranging from 15° to 50°, while harder materials such as steel necessitate the use of smaller wing angles. The physical shape of the part is a major factor that will determine how rigid the part can be held. The more rigid the part is held, the higher the wing angle that can be utilized. Finally, the insert shape itself will determine the limits of the angle selected since the shape of the remanufactured insert must compliment the shape of the original insert. 
     FIG. 2 is a top plan view of the insert  120  showing rotational angle  12 . The usual range for rotational angle  12  is from 0° to 25°. Usually, 10° is the typical angle for most applications. The length of the cutting edge  14  is the perimeter of insert  120 . As noted above, however, the angle selection can vary substantially depending on the particular selection of machine, workpiece, and insert. 
     FIG. 3 is a side view of the insert showing wing angle  16  usually from 5° to 30°. When hard metals are being cut, such as tool steel, wing angle  16  is normally selected to be from 5° to 15°. When soft metals are being cut, such as aluminum, wing angle  16  preferably ranges from 15° to 30°. As noted above, what determines which angle is finally selected depends on the factors discussed above and must be empirically derived by evaluating cutting performance factors such as chip length and shape. 
     Height  18  and center width  20  combine with wing angle  16  to produce the compound shape  124  that sharpens the cutting edge  22 . An average of 0.020 inches depth of material is removed in the sharpened area. Remanufactured insert  120  is easily identified from an insert fresh from the manufacturer in that the areas of the insert that have been ground have a high luster resulting from the grinding operation. This difference is easily noted even after the remanufactured insert has been recoated. The unique shapes can be ground on the used (or new) insert using standard grinding equipment that is well known in the art and readily available. While an automated approach permits a lower cost for each remanufactured insert, the use of very simple grinding equipment, as long as using one or more of the unique shapes discussed herein is utilized, will result in the insert being successfully remanufactured. 
     FIG. 4 is an isometric view of insert  120  in which areas that cannot be altered are identified. Areas  26  and  28  are required to position the insert in a holder (not shown) and cannot be ground. The compound shape  124  is normally used to sharpen inserts that are locked in a holder with a screw through a countersunk lockscrew hole  24 . As noted above, however, this shape is not limited to inserts having this particular geometry and method of attachment in its holder. 
     FIG. 5 is a perspective view of the radius and flank shape  132  ground on the side rake  130  of a typical diamond-shaped insert  128 . 
     FIG. 6 is a side view of insert  128  showing the ground concave shape  32 . This increases side rake angle  30  up to 5° through length  34 . Soft metals being cut, such as aluminum, require up to 5° increase in side rake angle  30 . As before, the precise selection of the preferred angle is dependent upon the particular need of the user. 
     FIG. 7 is a side view of the insert  128  showing the ground convex shape  38 . This decreases side rake angle  36  by up to 5° through length  40 . Hard metals being cut, such as tool steel, require up to 5° decrease in side rake angle  36 . 
     FIG. 8 is a top plan view of the insert  128  showing the length of the sharpened edge  44  from  42  to  46 . The ground shape has a runout angle  48  of 1° to 3° from the insert flank  47 , and a radius  45  adjacent to each flank  47 . An average of 0.020 inches depth of material is removed in the ground area. The inscribed circle  50  is tangent to the flank locating areas which position the insert  128  in the holder. Radius and flank grinding must not reduce the diameter of inscribed circle  50  or the insert  128  will not fit properly in its holder. The radius and flank shape is used to remanufacture inserts that are locked in a holder with a screw through lockscrew holder  52  or with a clamp that locks on the top surface  54 . 
     FIG. 9 is an isometric view of a typical parallelogram-shaped insert  134  that has been remanufactured using the bias helical shape. The bias helical shape  136  is ground at a bias angle  56  on the top rake of the insert  134 . 
     FIG. 10 is a top plan view of the insert  134  showing the length of the sharpened cutting edge  62  from  58  to  60  through width  64 . The bias angle  56  is 15° to 45° determined by the sharpened cutting edge  62  at point  60 . Length  66  may not be greater than {fraction (1/16)} of an inch beyond the center of the insert to maintain sufficient physical support in the cutter body. 
     FIG. 11 is a front plan view of the insert  134  showing the helical radius  68  which is equal to the length of the sharpened edge  62  in FIG. 10 from  58  to  60 . Radius  68  typically ranges from 0.1 to 2 inches with the most commonly selected value being about 1 inch. 
     FIG. 12 is a side view of the insert showing the change in top rake  70  in the ground area. Top rake  70  ranges usually from +5° to −5°. Soft metals being cut, such as aluminum require up to +5. Hard metals being cut, such as tool steel, require up to −5°. An average of 0.020 inches depth of material  72  is removed in the ground area. 
     FIG. 13 is a top plan view of insert  134  showing side  74 , back  76 , and top area  78  which are locating surfaces required to position the insert  134  in the holder and cannot be ground. The helical bias angle shape is normally used to remanufacture inserts which are locked in a holder with a screw through a lockscrew hole  135 . 
     FIG. 14 is an isometric view of the helical wing shape ground on a top plane with the top edge  140  of the insert  138 . While FIG. 14 depicts an insert remanufactured with a negative helical rake shape, a positive helical rake shape can also be used and the same principles apply thereto. 
     FIG. 15 is a side view showing the change in top rake  86 . This is usually from −10° to +10°. Hard metals being cut, such as tool steel, require up to −10°. Soft metals being cut, such as aluminum, require up to +10°. The helical radius  82  is tangent to the minimum depth  84  and can be determined as approximately 500 times minimum depth  84 . An average of 0.020 inches depth of material is removed in the grind area at  84 . This sharpens the cutting edge  80 . 
     FIG. 16 is a top plan view of the insert. The length of the cutting edge  92  is the perimeter of the view. The width of the sharpened area  90  can be determined as 0.15 times the overall width  88 . 
     FIG. 17 is a perspective view showing the top clamping area  96  and the locating area of the flank  94  which are required to clamp and position the insert in the holder and cannot be ground. The helical rake shape is normally used to remanufacture inserts that are locked in a holder with a screw through a lockscrew hole or with a clamp which locks on top surface  96 . 
     FIG. 18 is a perspective view of the compound shape on the top rake  98  as described in FIGS. 1,  2 ,  3 , and  4 , combined with the concave radius and flank shape on the side rake  100  as described in FIGS. 5,  6 ,  7 , and  8 . This is a typical application of the ground shapes used in combination. 
     FIG. 19 is a perspective view of the concave radius and flank shape ground on the side rake  104  as described in FIGS. 5,  6 ,  7 , and  8 , combined with the bias helical shape ground at a bias angle on the top rake  102  as described in FIGS. 9,  10 ,  11 ,  12 , and  13 . This is a typical application of the ground shapes used in combination. 
     FIG. 20 is a perspective view of the negative helical rake shape on a plane with the top edge  106  as described in FIGS. 14,  15 ,  16 , and  17 , combined with the concave radius and flank shape on the side rake  108  as described in FIGS. 5,  6 ,  7 , and  8 . This is a typical application of the ground shapes used in combination. 
     FIG. 21 is a perspective view of the concave radius and flank shape  110  as described in FIGS. 5,  6 ,  7 , and  8 , ground on a standard triangle insert. This is a typical application of this ground shape used to remanufacture other insert geometries as defined in “USA Standard Index (Throw-Away) Inserts for Cutting Tools (B94.25-1969)” by the United States of America Standards Institute. Ref. The American Society of Mechanical Engineers, United Engineering Center, 345 East 47 th  Street, New York, N.Y. 10017. 
     FIG. 22 is a perspective view of the helical rake shape on a plane with the top edge  112  as described in FIGS. 14,  15 ,  16 , and  17 , ground on a standard round insert. This is a typical application of this ground shape used to remanufacture other insert geometries. 
     FIG. 23 is a perspective view of the bias helical shape ground at a bias angle on the top rake  114  as described in FIGS. 9,  10 ,  11 ,  12 , and  13 , ground on a standard rectangular insert. This is a typical application of this ground shape used to remanufacture other insert geometries. 
     A representative example of performance improvement that is obtained is shown in FIGS. 24 and 25. A tool action analyzer, such as the ATAM-1100 manufactured by ATAM Systems Inc. of Worthington, Ohio, enables the visible, real-time measurement of the energy transfer between the tool and the workpiece. Vibration is common to all machine tools. Acceleration, which is one of the five components of vibration, provides the optimum indication of the interaction between the tool and the chip. The analyzer utilizes an accelerometer sensor which is used to determine the energy transfer. The greater the fluctuation in the tracing versus time, the greater the vibration or shock that the tool is experiencing and the quicker the tool will reach its breakage or wear limits. 
     In this example, the insert was a Helamill 2 manufactured by Iscar. A TiCN coating was used on the insert. The insert was being used to cut steam turbine blades. The machine was a vertical machining center operating at a speed of 800 surface feet per minute with a feed rate of 12 inches per minute. The depth of cut was 0.25 inches per pass. FIG. 24 shows a graph for a new insert while FIG. 25 shows the results from using a remanufactured insert using the shape described in FIGS.  1 - 4 . 
     In this example, a 100% improvement in insert edge productivity was found. Further, the cycle time wa s reduced by 25% per part. Non-cutting time was reduced by 50% per part and the surface finish was 100% improved. Similar improvements have been found with all of the remanufactured shapes disclosed herein. 
     While there have been described what are at present considered to be the preferred embodiments of this invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the invention and it is, therefore, aimed to cover all such chances and modifications as fall within the true spirit and scope of the invention.