Indexable ball nose self-chip breaking cutting insert

Abstract

The application discloses a kind of indexable ball head self chip breaking type cutting inserts, belong to cutting tool technical field, including cutting part, clamping part and insert bottom, cutting part has multiple cutting units along the circumferential distribution.Each cutting unit includes cutting edge, contact blade, arched potential difference blade, extrusion chip pocket and open curved surface, shared transition blade, boss and extrusion chip protrusion are formed between adjacent cutting units, cooling pit is arranged in extrusion chip pocket. By gradually changing the elevation of transition blade, extrusion chip protrusion and extrusion chip pocket area, the chip is gradually enhanced in the movement process by lateral constraint and bending extrusion effect, so as to promote the chip to break automatically.At the same time, the arched potential difference blade adjusts the chip flow path by spatial form change, improves the chip breaking stability of different cutting positions.

Description

Technical Field

[0001] This invention belongs to the field of cutting tool technology, specifically an indexable ball-end self-chip breaking cutting insert. Background Technology

[0002] In aerospace, automotive manufacturing and other fields, workpiece surfaces often have curvature that varies in multiple directions and complex spatial contours. A single cutting edge is difficult to adapt to the machining needs of different areas. Indexable cutting inserts can utilize different cutting positions distributed on the insert to undertake tasks such as roughing, finishing and cutting at different angles, thereby improving the machining adaptability of complex curved surfaces.

[0003] However, existing indexable cutting inserts, in order to improve space utilization and increase the number of available cutting edges, typically require multiple cutting units within a limited insert area. The small spacing between these units limits the functional area of ​​each unit for guiding, curling, and breaking chips. In actual metal cutting, chip formation is influenced not only by cutting speed, feed rate, and material properties, but also by the insert rake angle, chip breaker structure, and chip evacuation space. When multiple cutting units are integrated onto the same insert, the chip breaker typically needs a compact design to avoid interference between adjacent units, resulting in a reduced ability of a single cutting unit to constrain chip flow.

[0004] When machining highly ductile metals or performing high-feed cutting, the limited chip handling space of the cutting unit can easily lead to problems such as abnormal chip curl radius and inability to break chips in a timely manner. Continuous long chips may not only entangle the tool or workpiece, affecting machining stability, but may also scratch the machined surface, reducing machining quality. Summary of the Invention

[0005] The purpose of this invention is to provide an indexable ball-end self-chip breaking cutting insert to solve the problems mentioned in the prior art.

[0006] A self-chip breaking cutting insert with an indexable ball end is provided, comprising: The cutting part, the clamping part, and the bottom of the insert are included. The cutting part has multiple cutting units distributed circumferentially. From the outside to the inside, the cutting unit has a cutting edge, a contact cutting edge, an arched differential cutting edge, a chip extrusion pit, and an open curved surface. Between two adjacent cutting units, from the outside to the inside, a common transition cutting edge, a boss, and a chip extrusion protrusion are formed. A cooling pit is formed in the chip extrusion pit. The cutting edge is arc-shaped. The plane where the cutting edge is located is the elevation reference plane. The planes perpendicular to the axis of symmetry of the cutting edge and the elevation reference plane are the tangent planes. The radial inward direction of the cutting edge is the travel direction. The direction of normal to the elevation reference plane away from the bottom of the insert is the positive direction. The direction of normal to the elevation reference plane near the bottom of the insert is the negative direction. The cutting unit area containing the transition blade, chip protrusion, and chip pit is cut off by the cutting surface, and the cut area forms a projection line on the cutting surface. The elevation difference between the highest elevation point on both sides of the projection line and the lowest elevation point in the middle of the projection line gradually increases in the direction of travel, and the distance between the highest elevation points on both sides of the projection line gradually decreases in the direction of travel.

[0007] As a further aspect of the present invention: the distance between the two edges of the arched differential cutting edge that are close to and far from the contact cutting edge in the same direction of travel is the width of the arched differential cutting edge, and the width of the arched differential cutting edge gradually increases from the middle to both ends.

[0008] As a further aspect of the present invention: in the direction of travel, the middle part of the arched differential blade has a first extension line extending in the negative direction and the first extension line forms an α1 angle of 2°-4° with the elevation reference plane, the two ends of the arched differential blade have a second extension line extending in the positive direction and the second extension line forms an α2 angle of 4°-6° with the elevation reference plane, and the arched differential blade has a smooth transition between the first extension line and the second extension line.

[0009] As a further aspect of the present invention: the projection line has a slope ratio between the highest elevation point in the transition blade zone region and the lowest elevation point in the chip pit region. In the direction of travel, the slope ratio gradually transitions from 7-10:100 to 16-19:100. The slope ratio is the ratio of the elevation difference between the two points to the distance between the projections of the two points onto the elevation reference plane.

[0010] As a further aspect of the present invention: the lowest elevation of the chip pit gradually decreases along the direction of travel, while the highest elevation of the transition blade gradually increases along the direction of travel.

[0011] As a further aspect of the present invention: the projection line has a slope ratio between the highest elevation point in the chip protrusion area and the lowest elevation point in the chip pit area. In the direction of travel, the slope ratio gradually transitions from 31-34:100 to 47-50:100. The slope ratio is the ratio of the elevation difference between the two points to the distance between the projections of the two points onto the elevation reference plane.

[0012] As a further aspect of the present invention: the lowest elevation of the extrusion pit gradually decreases along the direction of travel, while the highest elevation of the extrusion protrusion gradually increases along the direction of travel.

[0013] As a further aspect of the present invention: the contact blade has an inclination angle of -5° to -5° relative to the elevation reference plane.

[0014] As a further aspect of the present invention: multiple cutting units are rotationally symmetrically distributed in the circumferential direction of the cutting part, and the circumferential angle of the cutting edge of each cutting unit is in the range of 35°-45°.

[0015] As a further aspect of the present invention: the circumferential angle of all cutting edges of the cutting part is ≥270°.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. Multiple cutting units are set in the circumferential direction of the cutting part, and each cutting unit is sequentially set with a cutting edge, a contact cutting edge, an arched differential cutting edge, a chip extrusion pit, and an open curved surface, so that the insert can be processed by indexing to utilize different cutting positions, thereby improving the overall utilization rate of the insert and the adaptability to complex curved surface processing.

[0017] 2. By setting a shared transition edge, boss and chip extrusion protrusion between adjacent cutting units, and by gradually designing the elevation changes of the transition edge, chip extrusion protrusion and chip extrusion pit, the chips are subjected to gradually enhanced compression and bending during the discharge process, which promotes rapid chip breakage and reduces the probability of long chips being generated. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of this drawing or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this drawing. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of the overall structure of the milling cutter insert of the present invention; Figure 2 for Figure 1 Enlarged view of region A in the middle; Figure 3 This is a partial structural schematic diagram of the cutting part of the present invention; Figure 4 for Figure 3 One of the partial cross-sectional views of AA in China; Figure 5 for Figure 3 A partial cross-sectional view of BB in the middle; Figure 6 for Figure 3 A partial cross-sectional view of CC in the middle; Figure 7 for Figure 3 A partial cross-sectional view of DD in the middle; Figure 8 for Figure 3 A partial cross-sectional view of the EE in the middle; Figure 9 for Figure 3 Partial cross-sectional view of AA (center).

[0020] In the figure: 1. Cutting section; 2. Blade bottom; 3. Cutting unit; 301. Cutting edge; 302. Contact edge band; 303. Arched differential edge band; 304. Chip extrusion pit; 305. Opening curved surface; 306. Transition edge band; 307. Boss; 308. Chip extrusion protrusion; 309. Cooling pit. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this application clearer, the application is described and illustrated below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application. All other embodiments obtained by those skilled in the art based on the embodiments provided in this application without inventive effort are within the scope of protection of this application.

[0022] Obviously, the accompanying drawings described below are merely some examples or embodiments of this application. Those skilled in the art can apply this application to other similar scenarios based on these drawings without any inventive effort. Furthermore, it is understood that although the efforts made in this development process may be complex and lengthy, for those skilled in the art related to the content disclosed in this application, any changes to design, manufacturing, or production based on the technical content disclosed in this application are merely conventional technical means and should not be construed as insufficient disclosure of the content of this application.

[0023] However, there may be instances where unnecessary detailed descriptions are omitted. For example, detailed descriptions of well-known matters or repetitive descriptions of essentially the same structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0024] Please see Figures 1-3As shown in the embodiment of the present invention, an indexable ball-end self-chip breaking cutting insert includes a cutting part 1 and a insert bottom 2. The cutting part 1 has a plurality of cutting units 3 distributed circumferentially. The cutting unit 3 has a cutting edge 301, a contact cutting edge 302, an arched differential cutting edge 303, a chip extrusion pit 304 and an open curved surface 305 distributed sequentially from the outside to the inside. A common transition cutting edge 306, a boss 307 and a chip extrusion protrusion 308 are formed sequentially from the outside to the inside between two adjacent cutting units 3. A cooling pit 309 is formed in the chip extrusion pit 304.

[0025] The cutting edge 301 is arc-shaped. The plane where the cutting edge 301 is located is the elevation reference plane Q. The planes perpendicular to the axis of symmetry of the cutting edge 301 and the elevation reference plane Q are the tangent planes. The radial inward direction of the cutting edge 301 is the travel direction. The direction of the normal of the elevation reference plane Q away from the bottom of the insert 2 is the positive direction. The direction of the normal of the elevation reference plane close to the bottom of the insert 2 is the negative direction. The cutting unit 3 region containing the transition blade 306, chip protrusion 308, and chip pit 304 is cut off by the cutting surface, and the cut-off region forms a projection line on the cutting surface. The elevation difference between the highest elevation point on both sides of the projection line and the lowest elevation point in the middle of the projection line gradually increases in the direction of travel, and the distance between the highest elevation points on both sides of the projection line gradually decreases in the direction of travel.

[0026] Specifically, the cutting edge 301 is used to directly cut into the workpiece and generate chips. The contact edge band 302 is used to stabilize and support the cutting area, reducing the impact load directly borne by the cutting edge 301. The cambered differential edge band 303 changes the contact state between the chip and the rake face of the insert, causing the chip to be non-uniformly constrained during its flow. The chip-gathering recess 304 is used to provide a chip-gathering space, causing the chip to bend and deform during its movement. The open curved surface 305 is used to guide the chips outward.

[0027] Adjacent cutting units 3 are provided with a shared transition cutting edge 306, boss 307, and chip-extrusion protrusion 308, which can form a continuous chip-breaking guiding structure within the limited tool space. The transition cutting edge 306 avoids abrupt structural changes between the cutting tips of adjacent cutting units 3, ensuring continuous chip flow during cutting. The boss 307 and chip-extrusion protrusion 308 apply localized compressive force to the chips, causing additional plastic deformation and promoting chip breakage. Simultaneously, a cooling recess 309 is provided inside the chip-extrusion recess 304, which stores and guides coolant during cutting, bringing the coolant closer to the cutting area and improving heat dissipation and lubrication.

[0028] Furthermore, adjacent cutting units 3 share the transition edge 306, boss 307, and chip extrusion protrusion 308, which solves the structural interference problem under the dense arrangement of multiple cutting units 3. There is no need to set up separate partition sidewalls for a single cutting unit 3. Multiple sets of chip control functional structures are integrated in the limited arc cutting area, which can adapt to the space constraints of large arc cutting surfaces with large coverage angles.

[0029] In addition, the insert also defines the spatial elevation variation relationship of the cutting unit 3 region. By defining the plane where the cutting edge 301 is located as the elevation reference plane, and specifying that the radial inward direction of the cutting edge 301 is the chip movement direction, the transition cutting edge 306, the chip extrusion protrusion 308, and the chip extrusion pit 304 form a chip breaking surface with a specific three-dimensional variation trend.

[0030] Furthermore, the elevation difference between the highest point on both sides of the projection line and the lowest point in the middle continuously increases along the direction of the iron filings' movement. As the iron filings flow inward, they are continuously subjected to the squeezing effect caused by the increasing height difference, resulting in plastic bending deformation layer by layer. The lateral distance between the highest points on both sides of the projection line continuously narrows along the direction of movement, and the chip protrusions 308 on both sides continuously converge inward, applying a constant and increasing lateral clamping force to the iron filings, restricting their lateral extension and expansion, and forcing them to continuously curl inward.

[0031] The bending deformation caused by the vertical height difference and the clamping contraction caused by the lateral narrowing work simultaneously to cause bidirectional plastic deformation of the strip-shaped iron chip, continuously accumulating internal fracture stress, creating the mechanical conditions for complete breakage within the subsequent chip extrusion pit 304. The symmetrical gradient structure also ensures that the stress deformation law of the iron chip is completely consistent when the arc cutting edge 301 participates in cutting at any angle, adapting to the needs of multi-angle contouring of complex curved surfaces.

[0032] It should be noted that the cut surface area is limited to the cutting unit 3 region, which includes the transition edge 306, the chip extrusion protrusion 308, and the chip extrusion pit 304, but excludes the cooling pit 309 region. Since the cooling pit 309 is located inside the chip extrusion pit 304, its main function is to guide the coolant into the cutting area and it does not participate in chip flow constraint or chip breaking. Therefore, when determining the spatial elevation variation of the chip extrusion pit 304, the influence of the cooling pit 309 on the local elevation needs to be excluded.

[0033] Specifically, the lowest elevation point of the chip pit 304 is usually located near the intersection of the central region of the chip pit 304 and the cooling pit 309. However, this location is only considered as an extension of the structure of the chip pit 304 itself, and not as the bottom of the cooling pit 309. In other words, the lowest point of the chip pit 304 is determined based on the change in cross-sectional profile in the tangential direction, rather than the absolute lowest position in the entire three-dimensional structure.

[0034] It should be further explained that when calculating the slope ratio, if the lowest elevation point of the chip pit 304 is located at the intersection with the cooling pit 309, the area of ​​the cooling pit 309 on the projection line will be filled to the same height as the lowest elevation point, and the position of the lowest elevation point when calculating the slope ratio will be set at the central axis position of the chip pit 304.

[0035] In some embodiments, the distance between the two edges of the arched differential cutting edge 303 that are close to and far from the contact cutting edge 302 in the same direction of travel is the width of the arched differential cutting edge 303, and the width of the arched differential cutting edge 303 gradually increases from the middle to both ends.

[0036] The distribution pattern of the arched differential cutting edge 303, with its width gradually increasing from the middle to both ends, complements the structure where the spacing on both sides of the projection line narrows inward. On one hand, this structure primarily adjusts the constraint strength experienced by the chip when passing through the arched differential cutting edge 303. Because the cutting edge 301 is arc-shaped, the cutting speed direction and cutting thickness differ at different circumferential positions. Traditional equal-width cutting edges tend to cause unstable chip constraint, making it difficult for the chip to effectively curl or detach from the core constraint region.

[0037] By making the width of the central part of the arched differential cutting edge 303 smaller and the width of both ends gradually increase, the central region of the chip can maintain a faster flow, while the lateral regions are subject to greater frictional resistance and spatial restriction. As the chip flows backward from the cutting edge 301, the sides of the chip are subject to gradually increasing resistance, causing the chip to shrink from both sides towards the center of the chip extrusion pit 304.

[0038] In addition, when the chips flow through the arched differential cutting edge 303 of the structure, they are subjected to uneven stretching and curling in the chip width direction, which causes the chips to form a trumpet-shaped curl. Uneven bending deformation can increase the internal stress of the chips. When the stress concentration reaches the material fracture limit, it can promote chip breakage.

[0039] On the other hand, increasing the width at both ends of the arched differential cutting edge 303 can also improve the structural strength of the insert edge region. Because the cutting direction of ball-end inserts constantly changes during complex surface machining, the areas near the ends of the cutting unit 3 are susceptible to impact loads. Increasing the width of the cutting edge at both ends increases the load-bearing area between adjacent tangential units 3, reduces the cutting pressure per unit area, decreases the risk of cutting edge breakage, and improves insert reliability.

[0040] In some embodiments, please refer to Figures 2-4As shown, in the direction of travel, the middle part of the arched differential cutting edge 303 has a first extension line L1 extending in the negative direction and the first extension line L1 forms an angle α1 of 2°-4° with the elevation reference plane. The two ends of the arched differential cutting edge 303 have a second extension line L2 extending in the positive direction and the second extension line L2 forms an angle α2 of 4°-6° with the elevation reference plane. The arched differential cutting edge 303 smoothly transitions between the first extension line L1 and the second extension line L2.

[0041] This structure gives the arched differential cutting edge band 303 a spatial orientation that is low in the middle and high at both ends. When the chip passes through this area, the central region, due to its negative inclination, creates a larger chip-carrying space, reducing chip flow resistance and allowing the chip to smoothly enter the chip-squeezing area. Meanwhile, the positive inclination of the two end regions enhances the blocking ability against chip edge areas.

[0042] Since chips are typically ribbon-like, the stress states in the central and edge regions differ, with the edge regions being more prone to swaying or spreading. By designing structures where both ends are higher than the central part, the lateral spread of the chips can be restricted, causing them to gradually converge towards the center. Simultaneously, the height difference between the central and end sections, created by the different angles, increases the bending deformation of the chips.

[0043] Furthermore, the central part of the arched differential cutting edge 303 tilts 2°-4° in the negative direction of elevation, forming a downward concave passageway that causes the mainstream iron filings to bend downwards. The two ends tilt 4°-6° in the positive direction of elevation, lifting the edge diverted iron filings upwards. The mainstream and diverted iron filings form a reverse bending effect, significantly increasing the unevenness of stress distribution within the iron filings cross-section. Compared to a single-angle cutting edge, it is easier to reach the conditions for plastic instability fracture.

[0044] Two sets of tilt angle ranges are optimized for various cutting conditions, balancing chip breaking effect and insert structural strength. When the downward fold angle at the center is less than 2°, the potential difference height is insufficient, and the initial deformation of the chips is weak, making it impossible to achieve effective curling when machining highly ductile materials or under high feed conditions. Angles exceeding 4° will cause the central concavity of the cutting edge to be too deep, making chips easily stuck and accumulating, further increasing cutting resistance. When the upward fold angles at both ends are less than 4°, the edge chips are not lifted high enough and will overlap and entangle with the mainstream chips below. Angles exceeding 6° will cause the edge of the cutting edge to bulge too high, easily causing strong friction and chipping under cutting impact, shortening the insert's lifespan. This parameter range is particularly suitable for machining scenarios with large fluctuations in cutting depth and uneven workpiece material hardness.

[0045] Furthermore, the two inclined sections transition smoothly without any sharp angles. When high-speed flowing metal chips come into contact with sharp edges, they are subjected to instantaneous impact, causing cutting vibration and chip splashing. The smooth curved surface can guide the metal chips to complete the bending motion smoothly, reducing the fluctuation of cutting force, improving the dimensional stability of complex curved surface machining, and eliminating stress concentration points at the edges of the cutting edge, thus reducing the probability of chipping during the cutting process.

[0046] In some embodiments, please refer to Figure 5 and Figure 6 As shown, the projection line has a slope ratio between the highest elevation point in the transition blade zone 306 region and the lowest elevation point in the chip pit 304 region. In the direction of travel, the slope ratio gradually transitions from 7-10:100 to 16-19:100. The slope ratio is the ratio of the elevation difference H between the two points to the distance D projected onto the elevation reference plane. The transition blade zone 306, as the second-level potential difference bearing structure, exhibits a continuously increasing slope, indicating that the downward concavity amplitude increases as the chips flow inward, and the curling radius gradually decreases.

[0047] Specifically, this structure controls the rate of height change along the chip's movement path, causing the chip to be subjected to gradually increasing compression. When the chip first enters the chip-breaking zone, a smaller slope ensures a smooth transition, preventing chip flow blockage due to excessively rapid height changes. As the chip continues to move forward, the slope gradually increases, causing the contact area between the chip and the blade surface to be gradually compressed.

[0048] Since a steeper slope means a greater change in height per unit distance, the chips are subjected to stronger bending forces during their movement. Especially when the chips enter the chip pit 304, the larger height difference forces the chips to change their direction of movement rapidly, causing them to undergo greater plastic deformation.

[0049] Furthermore, the slope ratio range has clear upper and lower boundaries, balancing chip removal smoothness and chip shaping effect. When the slope ratio is below 11:100, the slope surface tends to be gentle, failing to form an effective second-level potential difference, resulting in a lack of chip gathering and shaping effect. When the slope ratio is above 24:100, the slope surface is too steep, and thick chips are prone to getting stuck at the 304 inlet of the chip extrusion pit, blocking the chip removal channel and increasing cutting torque. This range can ensure both smooth chip removal and chip shaping ability across the entire machining parameter range.

[0050] In a further embodiment, the lowest elevation of the chip extrusion pit 304 gradually decreases along the direction of travel, while the highest elevation of the transition blade 306 gradually increases along the direction of travel. The elevation difference between the two gradually increases with the flow of the chips, continuously amplifying the effect of the second-stage gradual potential difference. The continuously rising transition blade 306 continuously applies downward pressure constraint from the upper surface of the chips, while the continuously sinking bottom of the pit forms a lifting and limiting effect from below. The bidirectional clamping action continuously compresses the thickness of the chips, and the amount of plastic deformation accumulates step by step, shortening the fracture path of the chips after entering the chip extrusion pit 304.

[0051] During machining, the feed rate and depth of cut fluctuate randomly, and the chip thickness continuously changes. The bidirectional reverse gradient elevation difference structure can adaptively match chips of different thicknesses. Narrow chips generated by shallow depth of cut can be slightly bent and shaped by following the sinking pit, while thick and wide chips generated by deep depth of cut are strongly compressed by the raised transition edge band 306. Regardless of chip thickness, stable plastic deformation can be achieved, avoiding the uncontrolled problems of thin chips without deformation and thick chips directly splashing out of the chip control channel.

[0052] The transition edge band 306 is raised and the chip extrusion pit 304 is sunken, both of which are continuous, smooth, and gradually changing curved surfaces. There are no steps or sharp abrupt changes in the structure. The chips flow without any jamming or obstruction throughout the process. There will be no cutting vibration or chip splashing caused by chips hitting the steps. It is suitable for automated continuous batch processing scenarios and eliminates the faults of long chips wrapping around the machine tool spindle and scratching the workpiece surface.

[0053] In some embodiments, please refer to Figures 7-8 As shown, the projection line has a slope ratio between the highest elevation point in the chip protrusion 308 region and the lowest elevation point in the chip pit 304 region. In the direction of travel, the slope ratio gradually transitions from 31-34:100 to 47-50:100. The slope ratio is the ratio of the elevation difference H between the two points to the distance D between the projections of the two points onto the elevation reference plane.

[0054] This structure features a higher gradient slope ratio on the lateral slope between the chip protrusions 308 and the chip pits 304, with a significantly steeper slope than the transition blade area 306, corresponding to the third-level gradual potential difference structure. After the chips enter the chip pit 304 area, the chip protrusions 308 on both sides form steep inward-converging slopes, applying lateral extrusion force simultaneously from both sides. Combined with the downward-sloping curved surface at the bottom of the pit, this achieves three-dimensional extrusion from top to bottom and left to right, resulting in a significant contraction of the chip cross-section and a rapid increase in internal stress to the fracture critical value.

[0055] The entire chip control structure forms a three-stage, graded slope progression system. Different slopes correspond to different processes in chip shaping, with a clear and orderly division of labor. The arched differential cutting edge 303 uses a low, gentle slope to complete the initial layered bending deformation of the chips. The transition cutting edge 306 uses a medium, gradually changing slope to complete the compression and shrinking of the chip thickness. The chip extrusion protrusion 308 area uses a high, steep slope to achieve the final strong curling and shaping of the chips. The three slopes increase progressively, releasing deformation stress in stages, avoiding irregular chip fragmentation and splashing caused by a single, violent compression, and ensuring that the discharged chips have a uniform shape and short, regular size.

[0056] In a further embodiment, similar to the structural change trend of the transition blade 306 region, the lowest elevation of the chip pit 304 gradually decreases along the travel direction, while the highest elevation of the chip protrusion 308 gradually increases along the travel direction.

[0057] This structural trend, combined with the high-slope surface structure of the chip protrusion 308, ensures that the highest point of the chip protrusion 308 continuously rises along the direction of travel, while the lowest point of the chip pit 304 sinks synchronously. When the chip is subjected to stronger and continuously changing vertical and horizontal forces, an enhanced bending stress gradient will further form inside the chip. As the space of the chip extrusion area gradually shrinks, the bending radius of the chip continuously decreases, causing local stress to concentrate in the root region of the chip, and thus reaching the deformation required for fracture when entering the opening curved surface 305 region with abrupt angle change.

[0058] In some embodiments, please refer to Figure 3 and Figure 9 As shown, the contact cutting edge 302 has a tilt angle β of -5° to -5° relative to the elevation reference plane. The -5° to 0° slight negative tilt angle is suitable for finishing high-hardness workpiece materials, which can reduce cutting friction resistance and improve the surface finish of the workpiece. The 0° to 5° slight positive tilt angle is suitable for roughing and heavy-duty deep-cutting, which thickens the solid thickness of the cutting edge, enhances the impact resistance of the cutting edge, and resists the impact damage caused by deep-cutting.

[0059] The contact edge 302 is in close contact with the arc-shaped cutting edge 301. The newly formed iron chips after metal cutting and separation first come into contact with this structure. The absolute value of the inclination angle is controlled within 5°. There are no steep abrupt steps at the junction of the contact edge 302 and the cutting edge 301, so it will not scrape the newly formed workpiece surface. At the same time, the gentle curved surface can guide the initial iron chips to flow smoothly into the rear arched edge 303, avoiding the initial flow of iron chips being turbulent and tumbling, and reducing the generation of burrs on the workpiece surface.

[0060] A narrow inclination angle range ensures the structural strength of the cutting edge of the insert even with a dense arrangement of multiple cutting units 3. If the inclination angle of the contact cutting edge 302 exceeds +5°, the thickness of the cutting edge increases significantly, leading to a substantial increase in cutting resistance. Conversely, if the inclination angle of the contact cutting edge 302 exceeds -5°, the thickness of the cutting edge decreases significantly. With multiple cutting units 3 densely arranged in the arc-shaped cutting section, the thin-walled cutting edge is highly susceptible to localized chipping. The -5° to -5° range achieves both guiding and chip control functions while maintaining sufficient cutting edge thickness, balancing chip breaking performance with the overall lifespan of the insert.

[0061] In some embodiments, please refer to Figure 1 and Figure 3 As shown, multiple cutting units 3 are rotationally symmetrically distributed in the circumferential direction of the cutting part 1, and the circumferential angle of the cutting edge 301 of each cutting unit 3 is 35°-45°.

[0062] Multiple cutting units 3 are rotationally symmetrically distributed, allowing the cutting tool to be rotated and repositioned after local wear, so that a new cutting unit 3 can enter the effective cutting position. Since each cutting unit 3 has the same angular relationship with the center of the cutting tool, the new cutting edge 301 after indexing can maintain a similar cutting posture, cutting angle, and stress state as the original cutting edge 301.

[0063] Meanwhile, the rotationally symmetric layout allows the insert to adapt to the constantly changing cutting direction during ball end milling. When machining complex curved surfaces, the contact area between the tool and the workpiece shifts with changes in the tool's orientation, making the single-direction cutting edge 301 prone to localized excessive wear. Multiple circumferentially distributed cutting units 3 provide multiple alternative cutting areas, allowing the insert to select the appropriate cutting unit 3 based on the machining area, cutting direction, and wear condition, thus improving its machining adaptability.

[0064] The circumferential angle of each cutting edge 301 is set to 35°-45°, which ensures that a single cutting unit 3 has sufficient cutting coverage. Within this angle range, a single cutting edge 301 can undertake a certain length of machining task without occupying too much circumferential space, thereby enabling the arrangement of multiple cutting units 3, achieving a high number of indexing operations and greater flexibility in use.

[0065] Furthermore, since each cutting unit 3 is equipped with a cutting edge 301, a contact cutting edge 302, an arched differential cutting edge 303, and a chip breaking structure, the size of the circumferential angle of the cutting unit 3 will directly affect the length of the chip flow path and the effective range of the chip breaking structure.

[0066] When the circumferential angle of the cutting edge 301 is controlled between 35° and 45°, the chip has sufficient movement distance within a single cutting unit 3, allowing it to sequentially pass through structures such as the contact cutting edge 302, the cambered differential cutting edge 303, and the chip-breaking pit 304, thereby completing the guiding, bending, and crushing fracture processes. If the circumferential angle is too small, the chip may enter an adjacent area before it has been sufficiently subjected to the chip-breaking structure, resulting in insufficient chip constraint and the formation of continuous long chips. If the circumferential angle is too large, the chip action area is too long, which can easily increase the friction between the chip and the cutting tool, thus increasing the cutting resistance.

[0067] In a further embodiment, the circumferential angle of all cutting edges 301 of the cutting section 1 is ≥270°. A larger cutting edge 301 coverage angle can increase the effective cutting range of the insert, allowing the insert to have a larger machining coverage area when machining complex curved surfaces. Especially in ball-end cutting inserts, the workpiece contact area usually changes with the machining posture. By increasing the total length of the cutting edge 301, the situation where a single area bears the cutting load for a long time can be reduced, allowing the cutting load to be distributed to multiple cutting positions.

[0068] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A type of indexable ball-end self-chip breaking cutting insert, characterized in that, include: The cutting part (1) and the bottom of the blade (2) are provided. The cutting part (1) has multiple cutting units (3) distributed in the circumferential direction. The cutting unit (3) has a cutting edge (301), a contact cutting edge (302), an arched differential cutting edge (303), a chip extrusion pit (304), and an open curved surface (305) distributed from the outside to the inside. A common transition cutting edge (306), a boss (307), and a chip extrusion protrusion (308) are formed from the outside to the inside between two adjacent cutting units (3). A cooling pit (309) is formed in the chip extrusion pit (304). The cutting edge (301) is arc-shaped. The plane where the cutting edge (301) is located is the elevation reference plane. The planes perpendicular to the axis of symmetry of the cutting edge (301) and the elevation reference plane are the tangent planes. The radial inward direction of the cutting edge (301) is the travel direction. The normal direction of the elevation reference plane away from the bottom of the insert (2) is the positive direction. The normal direction of the elevation reference plane close to the bottom of the insert (2) is the negative direction. The cutting unit (3) area containing the transition blade (306), chip protrusion (308) and chip pit (304) is cut off by the cutting surface, and the cut area forms a projection line on the cutting surface. The elevation difference between the highest elevation point on both sides of the projection line and the lowest elevation point in the middle of the projection line gradually increases in the direction of travel, and the distance between the highest elevation points on both sides of the projection line gradually decreases in the direction of travel.

2. The indexable ball-end self-chip breaking cutting insert according to claim 1, characterized in that, The distance between the two edges of the arched differential cutting edge (303) that are close to and far from the contact cutting edge (302) in the same direction of travel is the width of the arched differential cutting edge (303). The width of the arched differential cutting edge (303) gradually increases from the middle to both ends.

3. The indexable ball-end self-chip breaking cutting insert according to claim 1, characterized in that, In the direction of travel, the middle part of the arched differential blade (303) has a first extension line extending in the negative direction and the first extension line forms an α1 angle of 2°-4° with the elevation reference plane. The two ends of the arched differential blade (303) have a second extension line extending in the positive direction and the second extension line forms an α2 angle of 4°-6° with the elevation reference plane. The arched differential blade (303) smoothly transitions between the first extension line and the second extension line.

4. The indexable ball-end self-chip breaking cutting insert according to claim 1, characterized in that, The projection line has a slope ratio between the highest elevation point in the transition blade zone (306) and the lowest elevation point in the chip pit (304). In the direction of travel, the slope ratio gradually transitions from 7-10:100 to 16-19:

100. The slope ratio is the ratio of the elevation difference between the two points to the distance between the projections of the two points onto the elevation reference plane.

5. A self-chip breaking ball-end cutting insert according to claim 4, characterized in that, The lowest point of the extrusion pit (304) gradually decreases along the direction of travel, while the highest point of the transition blade (306) gradually increases along the direction of travel.

6. The indexable ball-end self-chip breaking cutting insert according to claim 1, characterized in that, The projection line has a slope ratio between the highest elevation point in the chip protrusion (308) region and the lowest elevation point in the chip pit (304) region. In the direction of travel, the slope ratio gradually transitions from 31-34:100 to 47-50:

100. The slope ratio is the ratio of the elevation difference between the two points to the distance between the projections of the two points onto the elevation reference plane.

7. A self-chip breaking ball-end cutting insert according to claim 6, characterized in that, The lowest elevation of the chip pit (304) gradually decreases along the direction of travel, while the highest elevation of the chip protrusion (308) gradually increases along the direction of travel.

8. The indexable ball-end self-chip breaking cutting insert according to claim 1, characterized in that, The contact blade (302) has an inclination angle of -5° to -5° relative to the elevation reference plane.

9. A self-chip breaking ball-end cutting insert according to claim 1, characterized in that, Multiple cutting units (3) are distributed in a rotationally symmetrical manner in the circumferential direction of the cutting part (1), and the circumferential angle of the cutting edge (301) of each cutting unit (3) is 35°-45°.

10. A self-chip breaking ball-end cutting insert according to claim 9, characterized in that, The circumferential angle of all cutting edges (301) of the cutting part (1) is ≥270°.

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