Curved surface machining milling cutter and machining method

Abstract

According to the curved surface machining milling cutter, an end edge arc is arranged on a cutting edge part, the relation between the radius R of the end edge arc and the diameter D of a cutter body is accurately determined, and then the geometric shape of the cutting edge part is optimized according to a first convolution parameter k1 which meets the condition that k1 is larger than or equal to 4.5 and smaller than or equal to 5.5; the cutting performance and stability of the cutter are improved, and the problem that the machining efficiency is low when a traditional ball cutter is used for machining a flat cambered surface is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of cutting tools, and in particular to a curved surface machining milling cutter and a machining method thereof. Background Art

[0002] When machining relatively flat curved surfaces, conventional ball cutters have a small effective diameter. This results in a lower linear velocity of the effective cutting edge in the center area, creating an "extrusion process" between the tool and the workpiece. While maintaining the same roughness, the cutting width and feed rate are limited. This leads to high temperatures, accelerated oxidation, and increased wear at the contact point between the tool and the workpiece, even with sufficient coolant. Furthermore, surface roughness cannot be achieved, resulting in poor machining quality and high tool wear. Therefore, a new curved surface milling cutter is urgently needed to address the low machining efficiency of conventional ball cutters when machining relatively flat curved surfaces. Summary of the Invention

[0003] The embodiments of the present invention provide a curved surface machining milling cutter and a machining method, aiming to solve the problem of low machining efficiency when a conventional ball cutter in the prior art is used to machine a relatively flat curved surface.

[0004] In a first aspect, the present invention provides a curved surface machining milling cutter, comprising: a cutter body, the cutter body defining a rotation axis, the cutter body comprising a shank portion and a blade portion adjacently arranged along the rotation axis, the blade portion being provided with an end blade portion at one end away from the shank portion along the rotation axis, the end blade portion being defined by an end blade arc, wherein the cutter body is cylindrical, the relationship between the radius R of the end blade arc and the diameter D of the cutter body is R=k1*D, 4.5≤k1≤5.5, and k1 is a first rotation parameter.

[0005] In a second aspect, a curved surface machining method is provided, using the curved surface machining milling cutter as described above, the method comprising: using the curved surface machining milling cutter to feed the curved surface of the workpiece at a preset feed speed along the curved surface contour of the workpiece. Perform down milling, the feed rate for: ; Among them, Ra is the target surface roughness of the workpiece, is the number of cutting edges, n is the rotational speed; during the machining process, coolant is continuously sprayed into the cutting area.

[0006] Compared with the prior art, the present invention has the following beneficial effects: In the technical solution of the present invention, the curved surface machining milling cutter sets the end blade arc on the blade portion and accurately determines the relationship between the radius R of the end blade arc and the cutter body diameter D. Then, through the first swing parameter k1, 4.5≤k1≤5.5 is satisfied, so that the geometric shape of the blade portion is optimized, the cutting performance and stability of the tool are improved, and the problem of low machining efficiency when traditional ball cutters machine relatively flat arc surfaces is solved. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.

[0008] Figure 1 This is a schematic structural diagram of a curved surface machining milling cutter according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the state of a conventional ball cutter machining a flat surface under existing technology; Figure 3 This is a schematic diagram of the curved surface machining milling cutter according to an embodiment of the present invention when machining a flat curved surface; Figure 4 A schematic diagram of the blade portion of a curved surface machining milling cutter according to an embodiment of the present invention; Figure 5 A diagram showing the steps of a curved surface machining method according to an embodiment of the present invention; Description of the figure mark: 10. Cutter body; 11. Rotation axis; 20. Blade portion; 21. End edge arc; 30. Peripheral blade; 40. Transition part; 41. Transition arc; 50. Handle; 60. Cutting edge. DETAILED DESCRIPTION

[0009] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0010] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present invention are only used to explain the relative position relationship, movement status, etc. between the various components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0011] The embodiment of the present invention discloses a curved surface milling cutter, which is designed to solve the problem of low processing efficiency of conventional ball cutters when processing relatively flat curved surfaces. Figures 1 to 4 The curved surface milling cutter includes a cutter body 10, wherein the cutter body 10 defines a rotation axis 11, and includes a shank portion 50 and a blade portion 20 adjacently arranged along the rotation axis 11. The blade portion 20 is provided with an end cutting edge portion at one end away from the shank portion 50 along the rotation axis 11, and the end cutting edge portion defines an end cutting edge arc 21. The cutter body 10 is cylindrical, and the relationship between the radius R of the end cutting edge arc 21 and the diameter D of the cutter body 10 is R=k1*D, 4.5≤k1≤5.5, and k1 is a first convolution parameter. The so-called first convolution parameter refers to the logical relationship constant between the radius R of the end cutting edge arc 21 and the diameter D of the cutter body 10. The cutter body 10 of the curved surface milling cutter of the present invention is made of a solid carbide round rod. Its structure comprises a cylindrical cutter body 10 defining a rotation axis 11. The cutter body 10 comprises a shank portion 50 and a blade portion 20 disposed adjacent to each other along the rotation axis 11. At the end of the blade portion 20, away from the shank portion 50, an end cutting edge portion is precisely machined using a CNC grinder. This end cutting edge portion is provided with an end cutting edge arc 21. The radius R of the end cutting edge arc 21 and the diameter D of the cutter body 10 are designed to be related by the following equation: R=k1×D; The first gyration parameter k1 has a value range of 4.5 ≤ k1 ≤ 5.5. Furthermore, the preferred value of k1 is 5. The geometric structure of the end cutting edge arc 21 allows the end cutting edge to better fit the workpiece surface during machining, expanding the effective cutting diameter and improving the cutting linear velocity, thereby significantly enhancing machining efficiency.

[0012] To explain more fully, Figure 2 As an example of the traditional ball cutter processing state, when adding a flat arc surface with a panel curvature R4221.5mm, the radius of the end edge arc 21 of the traditional ball cutter is only R=D / 2, which makes the effective cutting diameter of the traditional ball cutter extremely small. When the diameter D of the cutter body 10 is 10mm, the effective cutting diameter Only 1.4mm. The effective cutting area is near the center of the tool, according to the following cutting edge 60 linear speed formula: ;

[0013] It can be seen that since the effective cutting diameter is very small, the cutting speed is very small. Here, n is the rotational speed. The tool, while nearly stationary, "extrudes" the surface being machined rather than cutting it, causing high-temperature oxidation and rapid wear. After machining, the surface becomes covered with chatter marks and furrows, failing to meet machining requirements and causing severe tool wear.

[0014] The design of the radius R of the end edge arc 21 of the curved surface machining milling cutter of the present invention increases the effective cutting diameter. Figure 3 For example, Figure 3 The cutter body 10 of the curved surface milling cutter of the present invention also has a diameter D of 10 mm, but its effective cutting diameter is increased to 4.5 mm, ensuring that the effective cutting edge 60 is always in the high linear velocity zone. This increases the linear velocity of the cutting edge 60 by nearly 3.2 times compared to a conventional ball cutter. This avoids extrusion and reduces the temperature of the cutting edge 60, thereby extending the tool life.

[0015] Further, refer to Figure 1 The blade portion 20 includes a peripheral blade portion 30, which is arranged near the end blade portion. A transition portion 40 is provided between the peripheral blade portion 30 and the end blade portion. The transition portion 40 is defined by a transition arc 41. The transition arc 41 is tangent to the end blade arc 21 and smoothly transitions to the peripheral blade. The relationship between the radius r of the transition arc 41 and the diameter D of the blade body 10 is R=k2*D, 0.08≤k1≤0.12, and k2 is the second convolution parameter. The so-called second convolution parameter refers to the logical relationship constant between the radius r of the transition arc 41 and the diameter D of the blade body 10. In the blade portion 20 of the blade body 10, the peripheral blade portion 30 is arranged adjacent to the end blade portion, and the two are geometrically connected by the transition portion 40. The transition portion 40 is provided with a transition arc 41, which is precisely ground to achieve G2-level continuous tangency with the end blade arc 21 and smoothly transitions to the peripheral blade portion 30, that is, there is no step mutation. The radius r of the transition arc 41 is designed according to the relationship: R=k2*D, and the value range of k2 is 0.08≤k2≤0.12. Among them, the preferred value of k2 is 0.1. The specific value of K2 will vary with the radius size requirements of the edge of the machined curved surface on the workpiece. For workpieces with small size and low material strength, k2 can be selected as 0.08. For workpieces with large size and high material strength, k2 can be selected as 0.12. If the k2 value is greater than 0.12, it may cause the size of the end blade arc 21 to be limited, and if the k2 value is less than 0.08, the cutting edge 60 will be prone to stress concentration in the transition portion 40, which may cause chipping. The curvature of the traditional ball cutter changes suddenly at the transition point. In this case, the curvature of the blade is continuous by setting the transition arc 41, that is, the transition arc 41 inherits the end blade arc 21. At this time, the cutting stress can be dispersed, micro-chipping caused by stress concentration can be avoided, the life of the tool can be improved, and the processing yield rate can be improved.

[0016] Further, refer to Figure 1 The cutter body 10 includes a plurality of cutting edges 60, and the cutting edges 60 start from the vertex of the end edge arc 21, and extend in sequence along the end edge arc 21 and the transition arc 41 to the peripheral edge portion 30. On the cutter body 10 of the solid hard milling cutter, a plurality of cutting edges 60 are formed at one time by a CNC grinder. The path of each cutting edge 60 follows the starting point from the vertex of the end edge arc 21, that is, the origin O of the tool coordinate system, first extending along the end edge arc 21 to the tangent point with the transition arc 41, and then continuously extending along the transition arc 41 to the peripheral edge portion 30, and finally parallel to the axis of the cutter body 10. The peripheral edge segment is guided in a straight line along the axial direction of the tool to form a straight peripheral edge. In actual processing, the continuous cutting edge 60 makes the moving speed of the cutting point at the transition between the flat arc surface and the side wall constant, avoiding the speed zeroing and extrusion wear of the traditional ball cutter in the transition zone, and significantly improving the edge and corner processing quality.

[0017] Further, refer to Figure 1 At the vertex of the end edge of the solid carbide milling cutter, that is, the highest intersection of the rotation axis 11 of the cutter body 10 and the end edge curved surface, a tool coordinate system O-XYZ is established. The origin O is located at the vertex of the end edge arc 21; the Z axis coincides with the rotation axis 11 of the cutter body 10, with the positive direction pointing toward the shank 50; the X axis is set based on the initial extension direction of the cutting edge 60 at the origin O; and the Y axis is determined according to the right-hand rule. The generatrix of the end edge arc 21 satisfies the parametric equation in the XOZ plane of the tool coordinate system O-XYZ: ; in, is the angle parameter between the point on the revolution generatrix of the end blade portion and the center of the end blade arc 21 relative to the tool axis, The angle corresponding to the connection point between the end edge arc 21 and the tangent transition arc 41 is in the range of ≤ ≤ , i.e. between 3° and 8°. Preferably, = . The lower limit is 3° to ensure that the end edge arc 21 can be fully extended. The upper limit of 8° is to prevent premature transition arc 41 from merging and causing transition stress concentration. When manufacturing the curved surface milling cutter of the present invention, the equation for the rotational generatrix of the end cutting edge arc 21 can be input into a grinding machine to generate CNC code. To ensure the technical performance of the finished product produced by the curved surface milling cutter of the present invention, a δ angle tolerance of ±0.05° is permitted.

[0018] Further, refer to Figure 1When the surface machining milling cutter of the present invention is machined using a grinder, the precise machining of the transition arc 41 also requires a corresponding revolution generatrix equation. In the XOZ plane of the tool coordinate system O-XYZ, the revolution generatrix of the transition arc 41 strictly follows the parametric equation: ; in, The angle parameter between the point on the revolution generatrix of the end blade arc 21 and the center of the transition arc 41 relative to the tool axis. During manufacturing, the connection point is locked on the CNC grinding machine. The base coordinates of: ; After positioning the diamond grinding wheel at this point, the grinding is performed in increments of Δθ=0.1 according to the equation until θ=90°. To ensure the continuity of the first-order derivative at θ=δ, the phase difference must be calibrated in real time by a laser interferometer throughout the grinding process. At the same time, the following conditions must be met at θ=90°: ; That is, it is parallel to the generatrix of the peripheral edge portion 30, and finally achieves a smooth transition connection, thereby eliminating stress concentration in the transition area. Among them, if θ does not reach 90°, that is, the peripheral edge starts too early, the effective cutting edge 60 will be shortened.

[0019] Further, refer to Figure 1 The end blade portion rotation generatrix rotates around the rotation axis to form an end blade portion rotation surface. On the rotation surface, the equation of the end blade arc is: ; in, To obtain the angle between the radial line of a point on the end blade rotation surface and the XOZ plane, is the helix angle of the cutting edge 60. The value range is 32° to 38°, preferably 35°. Using a helix angle of 35° can make the chip removal efficiency of the surface machining milling cutter reach the experimental optimal value, and reduce the accumulation of cutting heat, thereby improving the quality of the finished product. If the helix angle is less than 32°, the axial force will be too large, which may cause the milling cutter to vibrate during machining. If the angle is greater than 38°, the rigidity of the surface machining milling cutter will be weakened due to the radial force component.

[0020] Furthermore, on the rotation surface, the equation of the transition arc is: ; Among them, the 、 and They are the three-dimensional coordinate values ​​of the points on the transition arc.

[0021] Based on the above transition arc equation, during manufacturing, four-axis linkage control can be performed on the five-axis CNC grinding machine. Among them, the five-axis CNC grinding machine strictly follows Coordinate equation, continuous grinding with a grinding wheel, and real-time monitoring of the surface continuity through an online white light interferometer to ensure G2-level connection with the end blade rotating surface, so that the maximum cutting speed can be maintained when performing cutting work in the transition area of ​​the surface machining milling cutter.

[0022] In one embodiment, referring to Figure 1 , the diameter D of the cutter body 10 is: 6mm≤D≤12mm. When D=6mm, the end edge arc 21R=30mm, the transition arc 41r==0.6mm, and the curved surface machining milling cutter is suitable for precision flat curved surfaces with a curvature radius ≥2000mm, such as for machining curved mobile phone glass molds. When D=10mm, R=50mm, and r=1.0mm, the curved surface machining milling cutter can be used to process large automobile panels. When D=12mm, R=60mm, and r=1.2mm, it can be used to process the stamping die surface of large-sized shell parts. The reason why D<6mm cannot be taken is that the diameter of the grinding wheel in the current industry is insufficient, and the limit size is Φ0.4mm. If D>12mm, the sintering deformation rate of the solid hard tool will increase when the curved surface machining milling cutter is heat treated, increasing the processing cost of the tool.

[0023] The present invention also provides a curved surface processing method, which uses the curved surface processing milling cutter described in the above embodiments, referring to Figure 5 , the steps include: S110, using the curved surface machining milling cutter to feed along the curved surface contour of the workpiece at a preset feed speed Perform down milling, the feed rate for: ; in, is the target surface roughness of the workpiece, is the number of cutting edges 60, n is the rotational speed; S120, continuously spraying coolant to the cutting area during the machining process.

[0024] The processing method of the present invention is suitable for processing flat arc surface workpieces. The so-called flat arc surface workpiece refers to a workpiece whose arc surface radius is much larger than the size of the processing area. Figure 4The curvature radius of the machining surface shown is 4221.5mm. When machining, the curved surface machining milling cutter of the present invention is selected, with the specific parameters of the cutter body 10 diameter D = 10mm, the end edge arc radius R = 50mm, the transition arc radius r = 1.0mm, and the number of blades Zn = 4. Then, the tool path is programmed in the CAM software so that the milling cutter performs down milling along the workpiece curved surface contour. Set to: ;

[0025] Where Ra is the target surface roughness of the workpiece, such as 0.5 μm; is the cutting width, in mm. Since the actual roughness is the residual height formed after processing, the cutting width is the cutting width of the programmed cutting parameter. and cutting edge 60 feed These two parameters determine the residual height. = 60° cutting edge feed When , the surface roughness is the most uniform and the workpiece processing effect is the best. Therefore, according to the following two formulas: ; ; The processing feed speed mentioned above can be obtained Formula. Taking the tool parameters provided in the previous article as an example, we can calculate: ; If a high-speed milling machine with a speed n of 15000 is used, the actual cutting feed rate is for: ; During machining, a water-soluble coolant is continuously sprayed into the cutting area via the cooling system. Thanks to the improvements to the curved surface machining cutter disclosed herein, a coolant spray pressure of less than 0.5 MPa can be used. The coolant prevents overheating and deformation of the tool and the machined surface. After machining with this tool, a roughness tester measured an Ra value of 0.45 to 0.5 μm. Furthermore, the tool life is extended three times compared to traditional ball cutters, while machining efficiency is increased by 316%, effectively solving the problems of roughness, wear, and inefficiency on flat curved surfaces.

[0026] In order to more clearly illustrate the outstanding advantages of the curved surface machining milling cutter of the present invention, a comparison table of machining results obtained by the curved surface machining method of the present invention and the traditional ball cutter machining method is listed below:

[0027] Except for the tool, the above table has the same processing environment and parameters, so it is representative of the experiment and is sufficient to illustrate the performance superiority of the surface processing method of the present invention when processing surfaces with a larger curvature radius.

[0028] The surface machining method of the present invention can produce an aircraft engine turbine casing with a surface that avoids center extrusion compared to traditional ball cutters, resulting in a significantly improved surface fatigue strength. Furthermore, due to the method's adaptability to surfaces with large curvatures, the method can be combined with coolant injection technology when machining the curved surface of the turbine blade root to address the risk of composite material delamination that exists under existing technologies. In the field of precision electronics, such as machining optical glass molds, traditional ball cutters cannot achieve Ra ≤ 0.1 μm due to center vibration marks. This method achieves ultra-precision machining by expanding the effective diameter, enabling lower machining roughness expectations to be achieved.

[0029] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and such modifications or substitutions are intended to be within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be subject to the scope of protection of the claims.

Claims

1. A curved surface machining milling cutter, characterized in that: include: A blade body, wherein the blade body is defined with a rotation axis, and the blade body includes a shank portion and a blade portion adjacently arranged along the rotation axis, the blade portion is provided with an end blade portion at one end away from the shank portion along the rotation axis, and the end blade portion is defined with an end blade arc, wherein the blade body is cylindrical, and the relationship between the radius R of the end blade arc and the diameter D of the blade body is R=k1*D, 4.5≤k1≤5.5, and k1 is a first rotation parameter.

2. The curved surface machining milling cutter according to claim 1, characterized in that: The blade portion includes a circumferential blade portion, which is arranged close to the end blade portion. A transition portion is provided between the circumferential blade portion and the end blade portion. The transition portion is defined by a transition arc, which is tangent to the end blade arc and smoothly transitions to the circumferential blade. The relationship between the radius r of the transition arc and the diameter D of the blade body is R=k2*D, 0.08≤k2≤0.12, and k2 is the second rotation parameter.

3. The curved surface machining milling cutter according to claim 2, characterized in that: The cutter body includes a plurality of cutting edges, and the cutting edges start from the apex of the end edge arc and extend sequentially along the end edge arc and the transition arc to the peripheral edge portion.

4. The curved surface machining milling cutter according to claim 3, characterized in that: The tool body is defined with a tool coordinate system O-XYZ, and the construction process of the tool coordinate system O-XYZ is: The origin O is set at the vertex of the end edge arc, the Z axis coincides with the rotation axis and points to the tool handle as the positive direction, the initial extension direction of the cutting edge at the origin O is the positive direction of the X axis, and the Y axis direction conforms to the right-hand rule; The revolution generatrix of the end cutting edge arc satisfies the parametric equation in the XOZ plane of the tool coordinate system O-XYZ: ;in, is the angle parameter between the point on the revolution generatrix of the end blade and the center of the end blade arc relative to the tool axis, is the angle corresponding to the connection point between the end edge arc and the tangent transition arc, and ≤ ≤ .

5. The curved surface machining milling cutter according to claim 4, characterized in that: The rotation generatrix of the transition arc satisfies the parametric equation in the XOZ plane of the tool coordinate system O-XYZ: ;in, It is the angle parameter between the point on the revolution generatrix of the end cutting edge arc and the center of the transition arc relative to the tool axis.

6. The curved surface machining milling cutter according to claim 5, characterized in that: The revolution generatrix of the end blade portion rotates around the rotation axis to form a revolution surface of the end blade portion. On the revolution surface, the equation of the end blade arc is: ;in, To obtain the angle between the radial line of the point on the end blade rotation surface and the XOZ plane, is the helix angle.

7. The curved surface machining milling cutter according to claim 6, characterized in that: On the rotation surface, the equation of the transition arc is: ; wherein, 、 and They are the three-dimensional coordinate values ​​of the points on the end face arc.

8. The curved surface machining milling cutter according to claim 1, characterized in that: The first convolution parameter k1 is 5.

9. The curved surface machining milling cutter according to claim 2, characterized in that: The second convolution parameter k2 is 0.

1.

10. The curved surface machining milling cutter according to any one of claims 4 to 7, characterized in that: described The value of .

11. The curved surface machining milling cutter according to claim 1, characterized in that: The diameter D of the blade body is: 6mm≤D≤12mm.

12. A curved surface machining method, characterized in that: Using the curved surface machining milling cutter according to any one of claims 1 to 11, the method comprises: Use the surface machining milling cutter to feed along the arc contour of the workpiece at a preset feed rate Perform down milling, the feed rate for: ; Among them, Ra is the target surface roughness of the workpiece, is the number of cutting edges, n is the rotational speed; During machining, coolant is continuously sprayed into the cutting area.

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