HK1089994B - Cutting tool having a wiper nose corner - Google Patents

Description

Cutting tool with wiper nose corner

Technical Field

The present invention relates to a material cutting tool. More particularly, the present invention relates to turning inserts and other cutting tools that include at least one wiper corner. The cutting tool and turning insert of the present invention are particularly suitable for metal finishing applications. The turning insert may also be adapted for various turning operations including, for example, roughing, light load grinding, and finishing.

Background

It is well known to perform turning operations with material cutting tools in which a cut sheet is removed from a workpiece being machined. Turning operations are machining processes for forming an outer surface on a workpiece (typically a rotating workpiece) by the action of a cutting tool. Typically, the workpiece is mounted on a lathe. Most metal removal in lathe turning is accomplished by a cutting tool having a single point of contact with the workpiece. These cutting tools may be produced in one piece from solid bar stock of tool steel and have a suitable cutting edge ground at one end. They may also be constructed in two pieces, typically comprising a tool shank and a turning insert made of carbide or some other hard material. The turning insert of the two-piece tool may be mechanically held in place with screws or other fasteners, or the insert may be directly brazed, soldered, or welded to the toolholder. Brazed, soldered or welded blades typically can be sharpened, however blades that are mechanically held in place are often removed, discarded and replaced with new, sharp blades after they become worn. Carbide turning inserts made of powdered metal have replaced single-piece abrasive carbide tools in most turning applications due to their low cost and high wear resistance.

Fig. 1 is an end view of a typical turning operation of a cylindrical workpiece 10 being turned using a two-piece cutting tool including a typical turning insert 12 secured to a tool holder 14. The workpiece 10 is rotated on a lathe (not shown) about an axis of rotation 16. The turning operation is set to cut to a depth 18 at a relief angle 15. Fig. 2 is a plan view of the turning insert 12. The turning insert 12 is a diamond turning insert having a nose corner angle 26 of 80 at the nose corner 24. The primary cutting edge 22 moves in the feed direction to perform most of the workpiece cutting, while the secondary cutting edge 20 performs a significantly smaller amount of workpiece cutting.

The American National Standards Institute (ANSI) has established standard terms for identifying replaceable turning inserts. Each ANSI standard blade is identified by a nine digit alphanumeric string that specifically characterizes the blade. The insert holder is also designed uniformly according to ANSI standards. The nine digit alphanumeric string determines the following characteristics of the turning insert: shape, clearance angle, tolerance, type, size, thickness, corner, edge condition, and hand direction (hand). A typical turning insert may be numbered, for example, SNMG432AR, and the meaning of ANSI hash mark strings for turning inserts will be apparent to those skilled in the art. ANSI standard turning inserts typically have nose corner radii between 1/16 inches and 1/4 inches.

The efficiency and quality of the turning operation depends on the cutting parameters set on the lathe, the characteristics of the cutting insert and the characteristics of the material being turned. Relevant cutting parameters include, for example, feed rate, lead angle of the cutting insert, and workpiece rotational speed. The mechanic tries to optimize these parameters depending on the turning insert used and the material being turned to obtain the highest feed rate while achieving the desired surface quality on the finished product.

During a typical cutting operation, significant forces are exerted on the turning insert. When the insert begins to cut, it is subjected to a great deal of pressure. Due to the constantly changing slice thickness, the turning insert is subjected to very varying axial and radial forces as it moves through the workpiece. High axial forces can cause vibrations and chatter. Conversely, high radial forces may cause the workpiece to move in the lathe, resulting in poor tolerances and poor surface quality.

The lead angle of the insert on the lathe is primarily indicative of the relative magnitude of the axial and radial cutting forces generated. The lead angle also has a significant effect on the manner in which radial and axial forces are applied to the workpiece and turning insert during typical machining operations. The lead angle is defined as the angle between the main cutting edge and the feed direction. When adjusting the lead angle, the force exerted by the workpiece on the turning insert changes. As the lead angle increases, the radial force decreases and the axial force increases. With a 45 deg. lead angle and standard radius nose corner insert, the radial and axial forces exerted on the turning insert are approximately equal. Mechanics must attempt to balance these forces to optimize surface finish and dimensional accuracy.

The shape and characteristics of the insert are also important to the efficiency and quality of the turning process. The nose radius is the curve defined by the edge of the insert that connects the primary cutting edge to the secondary cutting edge. Conventional turning inserts have a single radius, wherein the edge of the insert connecting the main cutting edge and the secondary cutting edge is a segment of a circle having a fixed radius. Turning inserts with a relatively large radius will produce finished workpieces with the best surface quality. However, a larger nose radius will increase the cutting forces required to perform the turning operation both axially and radially and generally results in poor chip control.

Vibration of the workpiece and the lathe may also occur when turning inserts with large nose radii are used in the turning operation. The vibrations adversely affect the finish of the metal surface being turned and also the service life of the turning insert. Thus, turning inserts having large tip radii have very limited use in metal turning operations. However, for roughing operations, inserts with large tip radii provide the strongest cutting surfaces and thus the longest useful life. Thus, typically, round, square or rectangular blades with large radii are selected for roughing.

For metal finishing operations, triangular, trigon or diamond turning inserts with small nose radii are typically selected to produce the smoothest finished surface. Turning inserts with smaller cutting tip angles (i.e., the angle between the primary and secondary cutting edges) and smaller nose corner radii allow greater control over the forces generated in the turning operation and provide a smoother surface on the finished workpiece. Such inserts are not as strong as turning inserts with larger radius nose corners and larger cutting tip angles, and thus have higher wear rates and shorter service lives.

Thus, there is a need for a turning insert that combines the advantages of a small nose radius and a larger nose radius. In an attempt to address this need, wiper turning inserts have been developed. As used herein, a "wiper turning insert" is a turning insert that has a radius, but the radius is not a curve of a fixed radius between the primary cutting edge and the secondary cutting edge. For example, U.S. patent No.5634745 describes a turning insert that includes a nose corner defining at least five circular segments between a primary cutting edge and a secondary cutting edge. The design provided by the blade of the' 745 patent is limited by the fact that the transition between one segment and an adjacent segment is abrupt, although tangential, but subject to some limitations. The nose corner of the turning insert of the' 745 patent is limited in that it can only be described by a circle segment. Furthermore, the maximum radius in the plurality of circle segments as described in the' 745 patent is limited to less than 8 or 10 mm. The present study shows that the radius of the circular arc exceeding 10mm not only contributes to the surface accuracy but also reduces the sensitivity of the surface accuracy variation, which is caused by unavoidable machining errors of the cutting insert and the tool holder.

Thus, there is a need in the art for a turning insert that provides smooth surface finish on a machined surface under a wide range of cutting conditions. There is also a need for a turning insert that combines the advantages of small nose radius turning inserts with the advantages of larger nose radius turning inserts. There is also a need for a method of designing a wiper blade that produces a nose corner having a smooth, coherent transition point and a large radius arc.

Disclosure of Invention

In one embodiment, the present invention is directed to a cutting insert comprising a top surface, a bottom surface, at least three side surfaces extending from the top surface to the bottom surface, and a nose corner connecting two adjacent side surfaces. The intersection of the cutting insert may comprise an intersection of the nose corner and the top surface, wherein at least a portion of the intersection is defined by a multi-segment spline curve. The multi-segment spline curve may be a B-spline curve. The intersection may also be defined by two arcs at each end of the B-spline curve. In some embodiments, the radius of the two arcs is greater than 10 mm.

Embodiments of the present invention also include a method of designing a turning insert that includes the step of designing a nose corner that includes a multi-segment spline curve. The multi-segment spline curve may be a B-spline curve. In another embodiment, the method is a computer-implemented method of designing a turning insert comprising the steps of: determining a desired turning insert shape and size, determining a desired contact pattern between the contact turning insert and the machining surface at a particular lead angle, and establishing a B-spline curve that smoothly and tangentially connects two arcs that are symmetric with respect to an bisector of the nose corner.

The reader will appreciate the foregoing details and advantages of the invention, as well as others, upon consideration of the following detailed description of embodiments of the invention. The reader also may comprehend such additional details and advantages of the present invention upon making use of the present invention.

Drawings

The features and advantages of the present invention may be better understood by referring to the accompanying drawings in which:

FIG. 1 is a view showing a typical turning operation on a cylindrical workpiece with a cutting tool including a turning insert secured to a toolholder;

FIG. 2 is a top plan view of a conventional turning insert with a constant radius nose corner;

FIG. 3 is an enlarged top plan view of a nose corner illustrating an embodiment of a wiper nose corner constructed in accordance with the present invention superimposed on the constant radius nose corner of the conventional turning insert of FIG. 2;

FIG. 4 is a diagram of one-half of the wiper nose corner design of the wiper nose corner of FIG. 3 showing control points for determining a multi-segment spline curve;

FIG. 5 is a partial cross-sectional view of the turning operation shown in FIG. 1 performed with the conventional turning insert of FIG. 2;

FIG. 6 is a partial cross-sectional view of the turning operation shown in FIG. 1 utilizing a turning insert having an embodiment of the wiper nose corner of the present invention constructed as shown in FIG. 3;

FIG. 7 illustrates a portion of an embodiment of a method for locating control points for designing a multi-segment spline curve for a wiper turning insert of the present invention;

FIG. 8 further illustrates an embodiment of the method of FIG. 7 for locating control points of wiper turning inserts;

FIG. 9 is a flow chart of the method of the present invention for designing and manufacturing a turning insert incorporating the multi-segment spline curve nose corner of the present invention;

FIG. 10 is a wire frame model of an embodiment of the turning insert of the present invention;

fig. 11 is a cross-sectional view showing a wire frame model of the turning insert embodiment shown in fig. 10.

Detailed Description

The present invention provides a turning insert incorporating a nose corner defined at least in part by a non-fixed radius, segmented polynomial basis function (e.g., a multi-segment spline curve) as an improvement over the nose corner of conventional turning inserts defined by a fixed radius curve or a multi-segment circle. Embodiments of the turning insert may additionally comprise two adjacent circular arc segments. Thus, turning inserts having wiper nose corners of the present invention may be designed to combine the advantages of turning inserts having a small nose radius with the advantages of turning inserts having a large nose radius.

Figure 3 is an enlarged top plan view of a nose corner illustrating the difference between an embodiment of a nose corner constructed in accordance with the present invention and a constant radius nose corner of a conventional turning insert (as shown in figures 1 and 2). Conventional turning inserts have a fixed nose corner 36. The wiper nose corner 35 of the present invention may be specifically designed to provide a turning insert with unique design and machining flexibility. Embodiments of the wiper nose corner may additionally include arcs on either side of the multi-segment spline curve. These arcs may have any radius. Preferably, the radii of the circular arcs are between 0.1mm and 20 mm. However, an arc of greater than 10mm may be advantageous in some applications, and the nose corner may also be adjusted so that any desired position along the nominal nose corner 36, nose corner angle 26, etc. satisfies the desired radius of the arc 37. Furthermore, the shape of the wiper nose corner may be easily designed to suit different types of turning inserts to obtain improved performance in machining surface accuracy.

In geometric modeling of two-or three-dimensional objects, lines and circles (or arcs that are part of a circle) may be the basic elements that form a complex or free-form curve. Complex curves are required when designing objects such as automobiles, ships, airplanes, and other objects, where various shape constraints must be met. The standard expression for the curve is a well-known polynomial. The fixed radius nose corner of a conventional turning insert is determined by a basic polynomial equation, for example:

x²+y²＝r²

where r is the radius of the nose corner

The cutting edge of the turning insert may be defined by a straight line according to a linear equation, e.g.

Where r is the radius of the nose corner and θ is the turning tip angle of the insert

However, in geometric modeling, it is often not sufficient to determine a complex curve using polynomial equations. Typically, the designer may arrange a series of control points that determine the shape of the curve to be established. Mathematical modeling techniques can be used to generate the curves and then change various parameters that control the model to refine the break and complete the design. For single-segment polynomial mathematical modeling, these parameters include polynomial degree and control points. The main drawback of single-segment polynomial modeling is that polynomials require high polynomial degree to satisfy a large number of constraints and to fix most complex curves accurately. Also, a curve that is a single segment as determined by a polynomial equation is not well suited for interactive shape design because it is difficult to control the shape of the curve in a local segment of the curve without changing the shape of the curve over its entire length.

Multi-segment spline curves, such as those used by the present invention to combine curve segments (typically individual polynomial curves) into a single smooth curve. The polynomial curve segment may have a relatively low polynomial degree, however, it is still flexible enough to describe a compound curve. In comparison, for improved design flexibility using conventional single polynomial curves, a large number of control points must be determined and inserted into the higher order polynomial equation. For example, in order to model a nose corner determined by 8 control points, a 7 th order polynomial equation is required. See NURBS BOOK, published by Springer-Verlas, New York 1997, authors Les Piegl and Wayne Tiller, incorporated herein by reference. Such high degree polynomial equations are difficult to calculate and predict the final shape of the curve with changes at a single control point. To minimize the polynomial degree of the curve and still obtain the required design flexibility, multi-segment spline curves may be used. Multi-segment spline curves can use a large number of control points regardless of their polynomial degree because they are generated by connecting multiple polynomial segments into a single curve. Each segment has a very low polynomial degree compared to the degree required for a single polynomial curve to model a similar curve. The degree of the polynomial segment may be selected by the tool designer without regard to the number of control points and thus without regard to the complexity of the curve design. In most cases, a cubic (3-degree) multi-segment spline curve will suffice to construct a compound free-form curve for designing the nose corner of the turning insert.

The nose corners of the prior art are limited to only a single arc or a combination of arcs. The circular arc may be formed by a quadratic polynomial. Thus, the nose corners of the prior art have limited design capabilities and may have difficulty achieving smooth transitions between different wiper nose segments when large radius arcs are required.

The algorithm established for the multi-segment spline curve can be described as follows:

wherein P is_iIs the setting of the control point.

N_i，kRepresents a (k-1) th-order B-spline synthesis function, which is determined by the following regression equation:

wherein [ u ]_i，...，u_i+k]Is the node vector of the B-spline smoothing edge tool nose.

By changing the node vector, people can obtain different shapes of the knife tip profile of the wiper blade; by changing the number of the control points, people can adjust the shape fitting precision (fit accuracy) and the degree of finish of the tool nose of the wiper blade; by determining the location of the control points, one can control the overall shape of the nose curve profile. Knots are the intervals in a B-spline curve where the base or synthesis function is determined or synthesized with control points to produce a single, smooth, flexible and parameter controllable B-spline curve. The number of nodes is the sum of the control points plus the number of curves plus 1.

An example of a nose curve of the present invention is shown in figure 4. The conventional nose corner 36 can be described by the polynomial equation of the arc described above. The only variable that can be adjusted is the radius of the arc. However, the wiper nose corner 35 may be described by a B-spline curve equation. The curve may be modified by increasing or decreasing the number of control points 39, 41-47, changing the location of the control points, changing the number of times the spline curve is modified, or changing the number or location of the nodes of the embodiment shown in fig. 4.

As an example, a single-segment spline curve according to the above equation with polynomial degree 3, 2 endpoints and 2 control points may be determined by the following equation:

X(t)＝a_xt³+b_xt²+c_xt+x₀

wherein:

x₃＝x₀+c_x+b_x+a_x；

y(t)＝a_yt³+b_yt²+c_yt+y₀

wherein:

y₃＝y₀+c_y+b_y+a_y；

solving the above equation for the coefficients yields the following equation:

c_x＝3(x₁-x₀)

b_x＝3(x₂-x₁)-c_x

a_x＝x₃-x₀-c_x-b_x

c_y＝3(y₁-y₀)

b_y＝3(y₂-y₁)-c_y

a_y＝y₃-y₀-c_y-b_y

once both endpoints (x) are determined₀，y₀) And (x)₃，y₃) Control point (x)₁，y₁) And (x)₂，y₂) And the distance t, a complete B-spline curve is determined and can be drawn.

More simply, since the solution of the equation involves a complex regression algorithm, the B-spline curve can be drawn by a commercially available software product, such as UNIGRAPHICS Version 17. These commercially sold software products allow the user to determine the number of curves, the number and location of control points and end points, and the number of nodes to incorporate into the curves. The software may allow the curve to be controlled by adjusting any of these parameters to modify the curve design to a final shape. This process can be repeated to design the wiper nose corner to meet the requirements of the mechanic. In some embodiments, polynomial curves having an order of 2-6 may be used to create curves with sufficient flexibility to design nose corners. Preferably, polynomial curves of degree from 2 to 4 yield curves of sufficient flexibility without requiring as many calculations as curves of higher polynomial degree. The B-spline nose 35 can be adjusted to fit smoothly into the large radius arc 37 without an abrupt transition, as shown in fig. 4, where point 39 is the intersection of the B-spline curve 35 and the large radius arc 37.

Fig. 5 and 6 are partial cross-sectional views of the turning operation shown in fig. 1. Fig. 5 illustrates a turning operation using a conventional turning insert 36. Figure 6 shows a turning operation using the turning insert of figure 3 with an embodiment of the wiper nose of the present invention. In fig. 5, the turning insert 12 has a conventional circular arc nose corner with a constant radius 20. The turning insert 12 cuts through the workpiece 10 and is set at a lead angle 54 and a depth of cut 18. The feed rate may be determined by dividing the distance 52 between successive cuts by the time it takes the lathe to rotate the workpiece 10 one full revolution about the axis 16. The surface roughness 56 and 66 in fig. 5 and 6 is determined by the shape and type of turning insert used in the turning operation and the feed rate. As is clear from comparing fig. 6 and 5, the surface roughness 66 of the turning insert with the wiper nose corner is less than the surface roughness 55 of the conventional turning insert with all other machining parameters held constant.

The present invention also provides a graphical solution for locating control points and designing multiple segments. By way of example, a detailed flow is given below to describe how embodiments of turning inserts having a wiper nose corner nose profile can be produced. The method of the present invention includes selecting a conventional standard turning insert and modifying the nose corner to form a B-spline curve. The first step of the graphical method is to determine the basic parameters that determine the overall characteristics of the turning insert. In this example, the turning insert will be a diamond shaped insert, such as shown in fig. 2. A portion of the corner of a conventional standard turning insert 12 to be modified is shown in fig. 7. In fig. 7, the origin of coordinates or the center of the rounded nose corner is the nose center 122. As an example, a diamond turning insert is used here, the corner angle of which is 80 °, so that the half angle 100 thereof is 40 °. The initial nose profile 36 is a conventional standard turning insert nose corner having a circular nose profile of a fixed radius determined by the length of the radius line 103. Conventional standard turning inserts also include an initial straight cutting edge 102. The initial nose profile 36 and the initial straight cutting edge 102 join at a point of intersection 109. The radius line 103 is shown extending from the intersection point 109 to the nose center 112.

The subsequent step of the method of the present invention is to determine the approximate machining parameters that the turning insert will employ. In this example, the wiper turning insert would be designed to be used at a machining lead angle of approximately 5 °. The lead angle line 105 may be drawn at the design machining lead angle with respect to the original straight cutting edge 102. The lead angle line 105 is drawn tangent to the initial nose profile 36 at the lead angle point 108. A line of intersection 113 may be drawn from the forward corner point 108 to the nose center 112.

The boundary within which the wiper nose is designed can then be determined. The boundary line 106 may be a line offset from and parallel to the lead angle line 105, or may be a line offset from and at a slight angle to the lead angle line 105. The design of line 106 will depend primarily on the corner angle, nose radius, and insert size. As shown in the embodiment of fig. 7, the boundary line 106 may be offset from the lead angle line 105 and slightly inclined from the lead angle line 105.

The entire wiper profile may then be formed by the arc 37 tangent to the boundary line 106, the arc 37 having a large radius 115, and the B-spline nose profile 35 defined by the boundary line 104 and smoothly joining the arc 37. Since the center line 40 is also a line of symmetry for the entire corner, the entire wiper profile is actually constructed from a single multi-segment B-spline 35 and two arcs 37 that are symmetric along the center line 40 of the nose corner, as shown in FIG. 7. In this embodiment, the two arcs 37 have a radius of greater than ten (10) millimeters and are symmetrically located on either side of the centerline 40 of the nose corner.

Due to the nature of the B-spline curve, the B-spline nose profile 35 can be easily adjusted and smoothly fit two arcs 37 having different arc radii 115, or in other words, there is no limit to the size of the arc radii 115. However, larger radii, such as greater than ten (10) millimeters, are preferred. Different blade sizes, nose radii, and blade shapes may require different arc radii 115 for optimal performance. By way of example, the arc radius 115 used in embodiments provided herein is 13.5 millimeters.

One embodiment of a method of identifying a B-spline nose 35 is shown in fig. 8. A first control point line 40 (center line 40) plus a series of control point lines 118 may be drawn to help identify the B-spline wiper blade of the present invention. Each control point line 118 emanates from the nose center 112 and can be described by the following equation:

Y_i＝tan[90°-(θ₀+Δθ)]*X；

wherein theta is₀Is a starting angle 117 measured from the centerline 40 to a second control point line 118A; Δ θ is the angular increment, i.e., the ending angle 119 minus the starting angle 117, then divided by (k-1), where k is the number of control point lines 118. Then, a series of control points 116 may be generated, totaling (k + 1). All these control points are limited to the right of the boundary lines 104 and 106. The general rule for locating all control points is to produce a smooth B-spline curve that is smoothly tangent to and connected to the large radius arc 37. The tangent of the B-spline curve at control point 116A on the centerline 40 should be perpendicular to the centerline 40. The starting angle 117 may or may not be equal to the angular increment between control lines 118.

The present invention is also directed to a method of designing a turning insert having a wiper nose corner. The multi-segment spline corner nose algorithm developed by the present invention provides a smooth, flexible wiper nose and also provides a universal method of easily constructing a wiper nose for any type of turning insert, including but not limited to diamonds, triangles, squares and triangles with any corner angle. The use of the B-spline curve algorithm of the present invention allows the design of an optimal wiper nose profile for a particular cutting application, e.g., a turning insert for a particular machining lead angle having any of the above-described turning insert shapes. There is no limitation on the range of the large circular arc 37 that plays an important role in achieving the desired surface accuracy.

The circular arc 37 with a large radius plays a very important role in determining the surface accuracy during turning operations using wiper nose inserts. Theoretically, a wiper nose insert having a partially linear profile would be superior to a wiper nose insert having a curved profile with a radius of a circular arc in view of the surface finish achieved during the machining process. However, there are always some unavoidable manufacturing errors or tolerances or inaccuracies in the carbide insert and the tool holder used to position the insert. Wiper nose inserts with straight portions are very sensitive to these errors or tolerances, which may result in unsatisfactory surface finish. Thus, arcs with large radii are less sensitive to the above-mentioned manufacturing errors or tolerances or operating errors. In general, the larger the radius, the better the performance of the wiper nose insert, in view of surface precision and reduced sensitivity to these errors, tolerances or inaccuracies.

The initial offset from line 105 to line 106 may be initially determined based on the machining lead angle to be used. The overall wiper nose profile, including the B-spline curve 35 and the arc 37 with the large radius 115, can then be determined based on the dimensions of the insert, the nominal corner nose radius, and the predicted surface finish. If desired, the offset may need to be readjusted until an optimal wiper nose profile is achieved.

Figure 9 is a flow chart illustrating one method of designing a wiper nose insert. As shown in fig. 9, a first step 200 provides for determining basic insert parameters, such as nominal nose radius, insert type, and insert shape, for a conventional insert used to design a wiper nose corner. The next step 205 determines how the insert can be used in a lathe, such as a lead angle. The lead angle may be determined at this point so that the wiper nose designer may design the wiper nose contact pattern based on the application being performed with the insert. If the method is performed by a computer or a graphical model is created as previously described in step 210, a three-dimensional wire frame computer-generated model may be generated, as shown in FIG. 10. The lead angle or range of lead angles determined in step 205 is then applied to the model in step 215 to begin determining the area to change to a wiper nose insert. The remaining boundaries in which the wiper nose will be located are determined in step 220. The wiper nose boundary may surround the entire conventional nose corner or a small section thereof, depending on the criteria the designer uses to change the nose corner.

In step 225, the designer determines parameters of the B-spline nose and the great circle arc that will define the curve, such as polynomial degree, number and location of control points, and other parameters that will control the final shape of the created curve. The entire wiper nose profile is then constructed in step 230 based on the parameters determined in step 225. Referring to fig. 10, step 235, a three-dimensional wire frame model of the wiper blade is built, and if necessary, step 240, a slice geometry (chipcutting geometry) may be added on the wiper blade platform for slice shape control. In step 245, the design established in the previous step is edited and linked, generating an executable source file for a Computer Aided Design (CAD) system. A solid model of the wiper turning insert design is then created using CAD software in step 250. At step 260, the designer observes the design and decides if further changes are needed. The design of the wiper tip may be changed by changing the parameters used to form the solid model of the wiper tip turning insert, as indicated in step 265. Such changes include, but are not limited to, lead angle, desired contact pattern, machined surface, surface precision, number and location of control points, degree of polynomial segment, and radius of the large arc. Once the designer is satisfied with the solid model of the wiper turning insert, the design is complete and the wiper turning insert may be produced using conventional manufacturing techniques, such as computer aided manufacturing, step 270.

A wire frame model of the turning insert of the present invention is shown in fig. 10 and 11. The turning insert 300 has a top surface 315 with a chip-cutting geometry and a side surface 310 extending from the top surface 315 to a bottom surface 320, as shown in fig. 11. The side surfaces 310 are joined at a nose corner 305. The turning insert 300 may include an aperture 325 therethrough to facilitate fastening the insert 300 to a turning insert holder.

While the invention has been described in conjunction with a number of embodiments, those skilled in the art, on considering the foregoing description, will recognize that many modifications and variations of the invention may be employed. All such variations and modifications of the invention are intended to be covered by the foregoing description and the following claims.

Claims (18)

1. A cutting insert comprising:

a top surface;

a bottom surface;

at least three side surfaces extending from the top surface to the bottom surface;

a nose corner connecting two adjacent side surfaces;

the intersection of the nose corner and the top surface;

at least a portion of the junction is defined by a multi-segment spline curve, wherein the multi-segment spline curve is a B-spline curve, and wherein the junction is further defined by two arcs at each end of the B-spline curve that smoothly and tangentially connect to the two arcs at each end of the B-spline curve.

2. The cutting insert of claim 1, wherein the radius of the two arcs is greater than 10 mm.

3. The cutting insert of claim 1, wherein the B-spline curve and the arc form a wiper nose corner.

4. The cutting insert of claim 1, wherein the polynomial degree of the B-spline curve is from 2 to 6.

5. The cutting insert of any one of claims 1, 2 or 4, wherein the B-spline curve is symmetric with respect to a bisector of the nose corner.

6. The cutting insert of any one of claims 1, 2 or 4, wherein the B-spline curve defines a surface extending from the top surface to the bottom surface.

7. The cutting insert of claim 1, wherein the B-spline curve defines a radius that varies continuously along a portion of the nose corner.

8. A method of designing a cutting insert, the method comprising the steps of:

designing a nose corner comprising a multi-segment spline curve, wherein the multi-segment spline curve is a B-spline curve, and wherein the nose corner is further defined by two arcs at each end of the B-spline curve, the B-spline curve smoothly and tangentially connecting to the two arcs at each end of the B-spline curve.

9. The method of designing a cutting insert of claim 8, wherein the B-spline curve shares an endpoint with each of two arcs and the two arcs are symmetric with respect to an bisector of the nose corner.

10. The method of designing a cutting insert of claim 9, wherein the radius of the two arcs is greater than 10 mm.

11. The method of designing a cutting insert of claim 8, further comprising:

the B-spline curve is changed within a certain range around the contact point.

12. The method of designing a cutting insert of claim 9, further comprising:

determining a nominal nose radius for a standard cutting insert for a similar machining application; a B-spline curve and an arc are created based on the nominal nose radius.

13. The method of designing a cutting insert of claim 8, wherein designing a B-spline curve comprises interactively controlling computer software designed to form the B-spline curve.

14. The method of designing a cutting insert of claim 8, wherein designing a B-spline curve includes varying the number and location of control points.

15. The method of designing a cutting insert of claim 8, wherein creating a B-spline curve includes changing a polynomial degree of the B-spline curve.

16. A computer-implemented method of designing a cutting insert, comprising the steps of:

determining the shape and size of the desired cutting insert;

determining a desired contact pattern between the cutting insert and the machining surface at a particular lead angle; and

designing a nose corner comprising a multi-segment spline curve, the multi-segment spline curve being a B-spline curve, the B-spline curve being smoothly and tangentially connected to two arcs located at each end of the B-spline curve, the two arcs being symmetrical with respect to an bisector of the nose corner.

17. The computer-implemented method of claim 16, further comprising:

the B-spline curve is varied within a determined range around the point of contact using an interactive curve fitting procedure using a computer aided drawing program.

18. The computer-implemented method of claim 17, further comprising the steps of:

determining a nominal nose radius for a standard cutting insert for a similar machining application;

a B-spline curve and two arcs are established corresponding to the nominal radius, insert size and machining lead angle.