Surface processing milling cutter and processing method

Abstract

The application discloses a curved surface processing milling cutter and a processing method, wherein the curved surface processing milling cutter is characterized in that an end edge arc is arranged on a blade part, the relationship between the radius R of the end edge arc and the diameter D of a cutter body is accurately determined, and the first convolution parameter k1 is satisfied, i.e. 4.5<=k1<=5.5, so that the geometric shape of the blade part is optimized, the cutting performance and stability of the cutter are improved, and the problem of low processing efficiency when a traditional ball cutter processes a relatively flat curved surface is solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of cutters, in particular to a curved surface machining milling cutter and a machining method. BACKGROUND

[0002] The effective diameter of the existing traditional ball cutter is small when machining relatively flat curved surfaces, which leads to a low linear speed of the effective cutting edge in the central area, so that the cutter and the workpiece work in a "extrusion machining" mode. Under the same roughness requirement, the cutting width and the feed amount are limited, so that high temperature, accelerated oxidation and aggravated wear occur at the contact between the cutter and the workpiece even in the case of sufficient cooling liquid, and the surface roughness cannot meet the standard, resulting in poor machining quality and high cutter loss. Therefore, a new curved surface machining milling cutter is needed to solve the problem of low machining efficiency of the existing ball cutter when machining relatively flat curved surfaces. SUMMARY

[0003] Embodiments of the present application provide a curved surface machining milling cutter and a machining method, aiming to solve the problem of low machining efficiency of the existing traditional ball cutter when machining relatively flat curved surfaces.

[0004] In a first aspect, the present application provides a curved surface machining milling cutter, comprising: a cutter body defining a rotation axis, the cutter body comprising a shank portion and a cutting edge portion arranged adjacent along the rotation axis, an end edge portion being provided at an end of the cutting edge portion away from the shank portion along the rotation axis, the end edge portion defining an end edge circular arc, wherein the cutter body is cylindrical, the radius R of the end edge circular arc and the diameter D of the cutter body satisfy the relationship R=k1*D, 4.5≤k1≤5.5, and the k1 is a first convolution parameter.

[0005] In a second aspect, a curved surface machining method using the curved surface machining milling cutter as described above is provided, the method comprising: using the curved surface machining milling cutter to perform face milling machining along the curved surface profile of a workpiece at a preset feed speed The feed speed is:

[0006] ;

[0007] wherein Ra is the target surface roughness of the workpiece, is the number of cutting edges, and n is the rotational speed; and continuously spraying cooling liquid to the cutting area during the machining process.

[0008] Compared with the prior art, the present application has the following advantages:

[0009] In the technical scheme of the present application, the curved surface machining milling cutter is provided with an end edge arc at the blade part, and the relationship between the radius R of the end edge arc and the diameter D of the cutter body is accurately determined, and the first convolution parameter k1 is satisfied, i.e. 4.5≤k1≤5.5, so that the geometry of the blade part is optimized, the cutting performance and stability of the cutter are improved, and the problem of low machining efficiency when the traditional ball cutter is used to machine a relatively flat curved surface is solved. BRIEF DESCRIPTION OF DRAWINGS

[0010] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor based on the drawings shown.

[0011] Figure 1 The figure is a structural schematic diagram of the curved surface machining milling cutter of the present application.

[0012] Figure 2 The figure is a state schematic diagram of the traditional ball cutter in the prior art when machining a flat curved surface.

[0013] Figure 3 The figure is a state schematic diagram of the curved surface machining milling cutter of the present application when machining a flat curved surface.

[0014] Figure 4 The figure is a schematic diagram of the blade part of the curved surface machining milling cutter of the present application.

[0015] Figure 5 The figure is a step diagram of the curved surface machining method of the present application.

[0016] Figure mark description:

[0017] 10, cutter body; 11, rotation axis;

[0018] 20, blade part; 21, end edge arc;

[0019] 30, peripheral edge part;

[0020] 40, transition part; 41, transition arc;

[0021] 50, shank part;

[0022] 60, cutting edge. DETAILED DESCRIPTION

[0023] Clearly, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative efforts fall within the scope of the present application.

[0024] It should be noted that all direction indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present application are only used to explain the relative position relationship, motion condition, etc. between components in a certain posture (as shown in the drawings), and if the certain posture changes, the direction indications also change accordingly.

[0025] The embodiments of the present application disclose a curved surface machining milling cutter, in order to solve the problem of low machining efficiency when the conventional ball cutter is used to machine a relatively flat curved surface in the prior art. Figures 1 to 4 The curved surface machining milling cutter comprises a cutter body 10, the cutter body 10 defines a rotation axis 11, the cutter body 10 comprises a shank part 50 and a blade part 20 which are adjacently arranged along the rotation axis 11, and the blade part 20 is provided with an end blade part at one end thereof which is away from the shank part 50 along the rotation axis 11, and the end blade part defines an end blade circular arc 21. The cutter body 10 is cylindrical, the relationship between the radius R of the end blade circular arc 21 and the diameter D of the cutter body 10 is R=k1*D, 4.5≤k1≤5.5, and the k1 is a first convolution parameter. The so-called first convolution parameter refers to a logical relationship constant between the radius R of the end blade circular arc 21 and the diameter D of the cutter body 10. The cutter body 10 of the curved surface machining milling cutter of the present application is made of a whole hard alloy round bar, and the structure comprises a cylindrical cutter body 10 which defines the rotation axis 11, and the cutter body 10 is composed of the shank part 50 and the blade part 20 which are adjacently arranged along the rotation axis 11. An end blade part is precisely machined by a numerical control grinding machine at the end of the blade part 20 which is away from the shank part 50, and the end blade part is provided with the end blade circular arc 21. The design relationship between the radius R of the end blade circular arc 21 and the diameter D of the cutter body 10 is as follows:

[0026] R=k1×D;

[0027] wherein the value range of the first convolution parameter k1 is 4.5≤k1≤5.5. Further, the preferred value of k1 is 5. The geometric structure of the end blade circular arc 21 enables the end blade to better fit the surface of a workpiece during the machining process, expands the effective cutting diameter, improves the cutting line speed, and thus greatly improves the machining efficiency.

[0028] In order to more fully illustrate, Figure 2The traditional ball cutter machining state is taken as an example, when the flat arc with a panel curvature R4221.5mm is added, the end blade arc 21 radius of the traditional ball cutter is only R=D / 2, which makes the effective cutting diameter of the traditional ball cutter extremely small, in the case that the cutter body 10 diameter D is 10mm, the effective cutting diameter is only 1.4mm. The effective cutting area is located near the cutter center, according to the following cutting edge 60 linear velocity formula:

[0029] ;

[0030] It can be seen that the cutting linear velocity is very small. Wherein, n is the rotating speed. The cutter is in the state of near static to extrude the machined curved surface, instead of cutting, which causes high temperature oxidation and rapid wear, after the machining is completed, the machined curved surface is full of vibration marks and furrows, which cannot meet the machining requirements, and the cutter is also seriously worn.

[0031] The design of the end blade arc 21 radius R of the curved surface machining cutter of the application makes the effective cutting diameter increase. For example, Figure 3 , the cutter body 10 diameter D of the curved surface machining cutter of the application in Figure 3 is also 10mm, but the effective cutting diameter increases to 4.5mm, which makes the effective cutting edge 60 always be located in the high linear velocity area, compared with the cutting edge 60 linear velocity of the traditional ball cutter, it increases by nearly 3.2 times. Thus, the extrusion machining is avoided, and the temperature of the cutting edge 60 is reduced, so that the service life of the cutter is prolonged.

[0032] Further, referring to Figure 1, the blade part 20 includes a peripheral blade part 30, the peripheral blade part 30 is arranged close to the end blade part, an excess part 40 is arranged between the peripheral blade part 30 and the end blade part, the excess part 40 is defined with a transition arc 41, the transition arc 41 is tangent to the end blade arc 21 and is connected with the peripheral blade part 30 in a smooth transition, the radius r of the transition arc 41 and the diameter D of the tool body 10 are in a relationship of R=k2*D, 0.08≤k1≤0.12, the k2 is a second convolution parameter. The so-called second convolution parameter refers to the logical relationship constant of the radius r of the transition arc 41 and the diameter D of the tool body 10. In the blade part 20 of the tool body 10, the peripheral blade part 30 is arranged adjacent to the end blade part, and the two are geometrically connected through the excess part 40. The excess part 40 is provided with a transition arc 41, which is continuously tangent to the end blade arc 21 through precision grinding to achieve G2 level, and is connected with the peripheral blade part 30 in a smooth transition, 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 of k2 is in the range of 0.08≤k2≤0.12. The preferred value of k2 is 0.1. The specific value of k2 will change with the size requirement of the corner radius of the workpiece to be machined. For small-size workpieces with low material strength, k2 can be selected as 0.08. For large-size workpieces with high material strength, k2 can be selected as 0.12. If k2 is greater than 0.12, the size of the end blade arc 21 may be limited, and if k2 is less than 0.08, the cutting edge 60 in the excess part 40 is prone to stress concentration and easy to break. The traditional ball cutter has a sudden change in curvature at the transition, and the present case makes the curvature of the cutting edge continuous by setting the transition arc 41, that is, the transition arc 41 receives the end blade arc 21. At this time, the cutting stress can be dispersed, the micro breakage caused by stress concentration can be avoided, the life of the tool is improved, and the processing yield is improved.

[0033] Further, with reference to Figure 1 , the tool body 10 includes a plurality of cutting edges 60, the cutting edges 60 are started from the vertex of the end blade arc 21, and are sequentially extended to the peripheral blade part 30 along the end blade arc 21 and the transition arc 41. On the whole-hard milling cutter tool body 10, a plurality of cutting edges 60 are formed at one time by a numerical control grinding machine. The path of each cutting edge 60 starts from the vertex of the end blade arc 21, that is, the tool coordinate system origin O, first extends along the end blade arc 21 to the tangent point of the transition arc 41, then continuously extends along the transition arc 41 to the peripheral blade part 30, and finally is parallel to the tool body 10 axis. The peripheral blade section is guided linearly along the tool axial direction to form a straight peripheral blade. In actual processing, the continuous cutting edge 60 makes the cutting point moving speed constant at the transition of the flat arc surface and the side wall, avoids the speed zero and extrusion wear of the traditional ball cutter in the transition area, and significantly improves the edge corner processing quality.

[0034] Further, with reference to Figure 1A tool coordinate system O-XYZ is established at the apex of the end-cutting edge of the solid carbide end mill, i.e., the highest intersection point of the rotation axis 11 of the cutter body 10 and the end-cutting edge surface. The origin O is located at the apex of the end-cutting arc 21; the Z-axis coincides with the rotation axis 11 of the cutter body 10, with its positive direction pointing towards the shank 50; the X-axis is set according to 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-cutting arc 21 satisfies the following parametric equations in the XOZ plane of the tool coordinate system O-XYZ:

[0035] ;

[0036] in, The angle parameter between a point on the generatrix of the end-cutting edge and the center of the end-cutting arc 21 relative to the tool axis. The angle corresponding to the connection point of the end-edge arc 21 and the tangent transition arc 41, with a specific value range of [value missing]. ≤ ≤ That is, between 3° and 8°. Preferably, = . The lower limit is set to 3° to ensure that the end-edge arc 21 can be fully extended. The upper limit of 8° is set to prevent premature engagement of the transition arc 41, which could lead to stress concentration at the transition point. When manufacturing the surface milling cutter of this invention, the equation of the generatrix of the end-edge arc 21 can be input into the grinding machine to generate CNC code. To ensure the technical performance of the finished product from the surface milling cutter of this invention, the δ angle tolerance is allowed to be within ±0.05°.

[0037] Furthermore, referring to Figure 1 When machining the curved surface milling cutter of this invention using a grinding machine, the precision machining of the transition arc 41 also requires a corresponding equation of rotation generatrix. Within the XOZ plane of the tool coordinate system O-XYZ, the rotation generatrix of the transition arc 41 strictly follows the parametric equation:

[0038] ;

[0039] in, The angle parameter between a point on the generatrix of the end-edge arc 21 and the center of the transition arc 41 relative to the tool axis. During manufacturing, the connection point is locked on a CNC grinding machine. Base coordinates:

[0040] ;

[0041] Then the diamond grinding wheel is positioned to this point, and then the equation increment Δθ = 0.1 step grinding until θ = 90°. In order to ensure the first derivative at θ = δ continuous, the phase difference is checked by the laser interferometer in real time during the polishing process. At the same time, it needs to meet θ = 90° at the point:

[0042] ;

[0043] That is, parallel to the generatrix of the peripheral edge part 30, and finally achieve the smooth transition connection, thereby eliminating the stress concentration in the transition area. If θ does not reach 90°, that is, the peripheral edge starts too early, it will cause the effective cutting edge 60 to be shortened.

[0044] Further, with reference to Figure 1 , the end edge part rotation generatrix rotates one revolution around the rotation axis to form an end edge part rotation surface, and on the rotation surface, the equation of the end edge arc is:

[0045] ;

[0046] Wherein, In order to obtain the included angle between the radial line of the point on the end edge part rotation surface and the XOZ plane, The helix angle of the cutting edge 60. The helix angle The value range is 32° to 38°, preferably 35°. Using a helix angle of 35° can make the chip removal efficiency of the curved surface machining milling cutter reach the experimental best value, and reduce the accumulation of cutting heat, thereby improving the quality of the finished product. If the helix angle Less than 32°, it will cause the axial force to be too large, which is easy to cause the curved surface machining milling cutter to vibrate during use. If the helix angle Greater than 38°, the radial component will weaken the rigidity of the curved surface machining milling cutter.

[0047] Further, on the rotation surface, the equation of the transition arc is:

[0048] ;

[0049] Wherein, the , and are the three-dimensional coordinate values of the points on the transition arc.

[0050] Based on the above equation of the transition arc, during manufacturing, four-axis linkage control can be performed on a five-axis numerical control grinding machine. The five-axis numerical control grinding machine strictly follows The coordinate equation, and continuously grinds the grinding wheel, and monitors the continuity of the curved surface in real time through the online white light interferometer, ensures the G2 level connection with the end edge rotation surface, so that the transition area of the curved surface machining milling cutter can maintain the maximum cutting speed when performing cutting work.

[0051] In an embodiment, referring to Figure 1 , the diameter D of the tool body 10 is: 6mm≤D≤12mm. When D=6mm, the end edge arc 21R=30mm, the transition arc 41r==0.6mm, the curved surface milling cutter is suitable for the curvature radius of the precision flat arc surface of ≥2000mm, such as for machining curved surface mobile phone glass mold. When D=10mm, R=50mm, r=1.0mm, the curved surface milling cutter can be used for machining large automobile panels. When D=12mm, R=60mm, r=1.2mm, it can be used for machining large size shell stamping die surface. The reason why D cannot be less than 6mm is that the grinding wheel diameter in the industry is insufficient at present, and the limit size is Φ0.4mm. If D>12mm, the sintering deformation rate of the whole hard tool will increase when the curved surface milling cutter is heat treated, which increases the processing cost of the tool.

[0052] The application also provides a curved surface machining method, which applies the curved surface machining milling cutter as described in the above embodiments, referring to Figure 5 , the steps of which include:

[0053] S110, using the curved surface machining milling cutter to perform face milling cutting processing along the arc surface contour of the workpiece at a preset feed speed , the feed speed is:

[0054] ;

[0055] Wherein, is the target surface roughness of the workpiece, is the number of cutting edges 60, and n is the rotational speed;

[0056] S120, continuously spraying cooling liquid to the cutting area during processing.

[0057] The machining method of the application is suitable for machining flat arc surface workpieces, and the so-called flat arc surface workpiece refers to a workpiece with an arc surface radius much larger than the size of the machining area, such as Figure 4 , the curvature radius 422 of the machining surface is 1.5mm. When machining, the curved surface machining milling cutter of the application is selected, and the specific parameters are: tool body 10 diameter D=10mm, end edge arc 21 radius R=50mm, transition arc 41 radius r=1.0mm, and edge number Zn=4. Then, the tool path is programmed in the CAM software, and the milling cutter is executed along the arc surface contour of the workpiece at a face milling cutting feed speed ;

[0058] ;

[0059] Wherein, Ra is the target surface roughness of the workpiece, such as 0.5 μm; is the cutting width, unit mm. Since the actual roughness is the residual height formed after processing, the cutting width is determined by the programmed cutting parameters and the feed amount of the cutting edge 60 These two parameters determine the residual height. When the cutting width = the feed amount of the cutting edge 60 , the surface roughness is the most uniform, and the workpiece processing effect is the best. Therefore, according to the following two formulas:

[0060] ;

[0061] ;

[0062] The processing feed speed formula in the foregoing can be obtained. Taking the tool parameters provided in the foregoing as an example, the following can be calculated:

[0063] ;

[0064] If a high-speed milling machine with a rotation speed n of 15000 is used, then the actual cutting processing feed speed is:

[0065] ;

[0066] During processing, the cutting area is continuously sprayed with water-soluble cooling liquid through a cooling system. Due to the improvement of the curved surface processing milling cutter of the present application, the cooling liquid spraying pressure can be lower than 0.5 MPa. Under the action of the cooling liquid, the tool and the processed surface can be prevented from overheating and deforming. After actual processing by the tool, the roughness is measured by a roughness meter to be Ra≈0.45~0.5 μm. The tool life is prolonged by 3 times compared with the traditional ball cutter, and the processing efficiency is improved by 316%. The roughness, wear and low efficiency problems of the flat arc surface are perfectly solved.

[0067] In order to more clearly illustrate the outstanding advantages of the curved surface processing milling cutter of the present application in processing, the following lists a comparison table of the processing results obtained by the curved surface processing method of the present application and the traditional ball cutter processing method:

[0068]

[0069] The above table is representative of the experiment except for the tool, and the other processing environments and parameters are the same, so as to illustrate the superior performance of the curved surface processing method of the present application when processing a curved surface with a large radius of curvature.

[0070] The aircraft engine scroll surface processed by the curved surface processing method of the present application has greatly improved surface fatigue strength because the center extrusion is avoided compared with the traditional ball cutter. In addition, due to the adaptability of the method to large curvature surfaces, when processing turbine blade roots, combined with cooling liquid injection technology, the risk of delamination of composite materials existing in the prior art can be solved. In the field of precision electronics, such as processing optical glass mold cores, the traditional ball cutter cannot achieve Ra≤0.1 μm due to the center vibration pattern. The present method realizes superfinishing by expanding the effective diameter, so that lower machining roughness is expected to be achieved.

[0071] The above is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art can easily think of various equivalent modifications or replacements within the technical range disclosed by the present application, and these modifications or replacements should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A milling cutter for machining curved surfaces, characterized in that, include: The blade body defines a rotation axis and includes a handle portion and a blade portion arranged adjacent to each other along the rotation axis. The blade portion has an end-edge portion at one end along the rotation axis away from the handle portion, and the end-edge portion defines an end-edge arc. The blade body is cylindrical, and the relationship between the radius R of the end-edge arc and the diameter D of the blade body is R=k1*D, 4.5≤k1≤5.5, where k1 is a first rotation parameter. The blade portion includes a peripheral blade portion, which is located close to the end blade portion. A transition portion is provided between the peripheral blade portion and the end blade portion. The transition portion defines a transition arc, which is tangent to the end blade arc and smoothly transitions to the peripheral blade portion. 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, where k2 is the second rotation parameter. The blade body includes multiple cutting edges, which start from the apex of the end edge arc and extend sequentially along the end edge arc and transition arc to the peripheral edge. The tool body defines a tool coordinate system O-XYZ, and the process of constructing the tool coordinate system O-XYZ is as follows: The origin O is set at the apex of the end-edge arc. The Z-axis coincides with the rotation axis and points towards the tool holder 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 generatrix of the end-edge arc satisfies a parametric equation in the XOZ plane of the tool coordinate system O-XYZ: ； in, The angle parameter between a point on the generatrix of the end-cutting edge and the center of the end-cutting arc relative to the tool axis. The angle corresponding to the connection point of the end-edge arc and the tangent transition arc is given, and ≤ ≤ .

2. The surface milling cutter according to claim 1, characterized in that, The generatrix of the transition arc satisfies the parametric equation in the XOZ plane of the tool coordinate system O-XYZ: ； in, The angle parameter between a point on the generatrix of the end-edge arc and the center of the transition arc relative to the tool axis.

3. The surface milling cutter according to claim 2, characterized in that, The generatrix of the cutting edge rotates around the axis of rotation to form a surface of revolution of the cutting edge. On this surface of revolution, the equation of the arc of the cutting edge is: ； in, The angle between the radial line at a point on the rotating surface of the cutting edge and the XOZ plane. It is the helix angle.

4. The surface milling cutter according to claim 3, characterized in that, On the surface of revolution, the equation of the transition arc is: ; Among them, the , and These are the three-dimensional coordinates of points on the end face arc.

5. The surface milling cutter according to claim 1, characterized in that, The first gyro parameter k1 is 5.

6. The surface milling cutter according to claim 1, characterized in that, The second cyclotron parameter k2 is 0.

1.

7. The surface milling cutter according to any one of claims 1 to 4, characterized in that, The The value is .

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

9. A method for machining curved surfaces, characterized in that, The method, using a surface machining milling cutter as described in any one of claims 1 to 8, comprises: The surface milling cutter is used to cut along the arc contour of the workpiece at a preset feed rate. For climb milling, the feed rate for: ； Where Ra is the target surface roughness of the workpiece. Where n is the number of cutting edges and n is the rotational speed; Coolant is continuously sprayed onto the cutting area during the machining process.

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