Cutting path and machining method for single-point diamond ultra-precision lathe cutting

Abstract

The present invention relates to the field of ultra-precision machining technology, and discloses a machining trajectory and a machining method for single-point diamond ultra-precision lathe cutting. The single-point diamond ultra-precision lathe includes a single-crystal diamond tool, and the single-crystal diamond tool includes a blade. The running path of the cutting edge at the contact surface with the workpiece surface on the blade is used as the machining trajectory, and the machining trajectory is used to cut the serrated tip of the workpiece; the machining trajectory includes two extension lines on both sides of the serrated tip and an arc, and both ends of the arc are tangent to the two extension lines respectively; the diameter of the arc is greater than the maximum width of the chips generated by cutting the workpiece. The present invention designs a new machining trajectory for the serrated tip, so that the cutting edge extends from the extension line on one side of the serrated tip, and then cuts into the other side of the serrated tip through the arc, so that when cutting into the workpiece again, the trajectory direction of the tool does not change, and the turning error is set on the trajectory outside the workpiece surface, ensuring the integrity of the serrated tip and avoiding the generation of jitter.

Description

Technical Field

[0001] The invention belongs to the technical field of ultra-precision machining, and in particular relates to a machining track and a machining method for single-point diamond ultra-precision turning. Background Art

[0002] Ultra-precision cutting is the process of fine machining of workpieces using high-precision lathes and designed tools. By precisely controlling the tool's motion trajectory and cutting parameters, extremely high machining accuracy and surface quality can be achieved. It can be used to manufacture high-precision parts in the fields of aerospace, electronics, and medical treatment, as well as for machining planes, spherical surfaces, aspherical surfaces, free-form surfaces, large-aperture aspherical surfaces, asymmetric free-form surfaces, optical elements and diffractive optical elements, Fresnel lenses and other microstructure elements.

[0003] The single-point diamond lathe is a type of ultra-precision cutting tool, suitable for processing non-ferrous metals such as copper and aluminum, as well as materials such as plastics. The surface finish of the processed parts needs to be very high to meet the high requirements of part surface quality in the fields of optics, biology, etc.

[0004] However, when cutting sawtooth-shaped workpieces, the chips generated during the processing of existing diamond tools are often unable to be discharged or dropped smoothly due to the existence of the lathe cooling air blind area and the continuous chip bands. For example, the strip-shaped chips entangle the tool, the space is narrow, the tool is blocked, other structures are blocked, etc., which make the cooling air unable to carry the chips away smoothly, thereby entangling the chips in the tool trajectory movement process, causing different degrees of scratches on the surface of the parts, affecting the surface quality and reducing the processing accuracy.

[0005] In addition, the machining trajectory often moves according to the shape of the workpiece during machining, and the sawtooth tip part often moves like Figure 1 The shape shown is an arc, and the arc trajectory oscillates and cannot meet the design requirements on the workpiece shape.

[0006] Therefore, it is urgent to design a machining trajectory and method for single-point diamond ultra-precision turning. Summary of the invention

[0007] In order to solve the above technical problems, the present invention provides a single-point diamond ultra-precision turning processing trajectory and processing method, which reduces the process of chips entering the tool running trajectory to participate in processing, improves precision, avoids increasing the number of processing times, and saves time, manpower and cost.

[0008] First aspect, the first object of the present invention is to provide a machining trajectory for single-point diamond ultra-precision turning. The single-point diamond ultra-precision lathe includes a single-crystal diamond tool, and the single-crystal diamond tool includes a blade. The running path of the cutting edge at the contact surface with the workpiece on the blade is used as the machining trajectory, and the machining trajectory is used to cut the serrated tip of the workpiece; the machining trajectory includes two extension lines and an arc on both sides of the serrated tip, and both ends of the arc are tangent to the two extension lines respectively; the diameter of the arc is greater than the maximum width of the chip generated by cutting the workpiece.

[0009] Further, the maximum width of the chip is: at a specific tool translation speed, workpiece rotation speed, and cutting depth, the trajectory length of the cutting edge on the workpiece surface from the start of cutting into the workpiece surface to reaching the workpiece surface again when the workpiece rotates one circle; wherein,

[0010] The starting position of the cutting edge cutting into the workpiece surface is: the intersection of the workpiece surface and the perpendicular bisector of the tool translation line segment.

[0011] Further, the translation distance of the tool when the workpiece rotates one week is W. Set the starting point of the tool movement as the first position and the end point of the tool movement as the second position; the trajectory length M is calculated by the following formula:

[0012] ,

[0013] ,

[0014] ,

[0015] ,

[0016] wherein, , and are set auxiliary angles, is the angle between the vertical line and the line connecting the point where the cutting edge leaves the workpiece surface and the second position, is the angle between the vertical line and the line connecting the point where the cutting edge cuts into the workpiece surface and the second position, is the angle between the line connecting the point where the cutting edge leaves the workpiece surface and the second position and the line connecting the point where the cutting edge cuts into the workpiece surface and the second position, R is the radius corresponding to the cutting edge arc of the tool, and H is the cutting depth.

[0017] Further, the distance W between the first position and the second position is calculated by the following formula:

[0018] ,

[0019] wherein, v is the tool translation speed and t is the time for the workpiece to rotate one circle.

[0020] Furthermore, the included angle between the two sides of the serrated tip is 0° to 180°.

[0021] Furthermore, the included angle between the blade and any side of the serrated tip is greater than or equal to 5°.

[0022] In a second aspect, the present invention provides a processing method for single-point diamond ultra-precision turning, which is a processing method for processing the serrated tip according to the processing trajectory of single-point diamond ultra-precision lathe cutting described in the first aspect.

[0023] The embodiments of the present invention have the following technical effects:

[0024] The present application designs a new processing trajectory for the serrated tip, so that the cutting edge extends from the extension line of one side of the serrated tip and then cuts into the other side of the serrated tip through an arc. When cutting into the workpiece again, the trajectory direction of the tool does not change, and the turning error is set on the trajectory outside the workpiece surface, ensuring the integrity of the serrated tip, avoiding the generation of jitter, and meeting the design requirements of the workpiece shape;

[0025] The radius of the arc part is greater than the maximum width of the chip, so that the farthest distance between the arc and the serrated tip must be greater than the maximum width of the chip. When the tool is in the arc part, the chip can fall from the middle gap, reducing the process of the chip entering the tool running trajectory to participate in processing, improving the accuracy; avoiding increasing the number of processing times, saving time, manpower and cost. Description of the Drawings

[0026] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for use in the description of the specific embodiments or the prior art. Obviously, the following drawings are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0027] Figure 1 It is a schematic structural diagram of the current processing trajectory provided by the embodiment of the present invention;

[0028] Figure 2 It is a schematic diagram of the processing trajectory of single-point diamond ultra-precision lathe cutting provided by the embodiment of the present invention;

[0029] Figure 3 It is a schematic diagram of a cutting process provided by the embodiment of the present invention;

[0030] Figure 4 It is a schematic diagram of the processing trajectory when the included angle between the two sides of the serrated tip provided by the embodiment of the present invention is 20°;

[0031] Figure 5 It is a schematic diagram of the machining trajectory when the included angle between the two sides of the serrated tip provided by the embodiment of the present invention is 90°;

[0032] Figure 6 It is a schematic diagram of the machining trajectory when the included angle between the two sides of the serrated tip provided by the embodiment of the present invention is 135°;

[0033] Figure 7 It is a schematic diagram of the actual machining trajectory of a single-point diamond ultra-precision turning provided by the embodiment of the present invention. Detailed implementation manners

[0034] To make the objectives, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be described clearly and completely below. Apparently, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts fall within the scope protected by the present invention.

[0035] Embodiment 1

[0036] During the working process of a single-point diamond ultra-precision lathe, the workpiece needs to be installed on the spindle of the machine tool. The rotation of the spindle causes the workpiece to rotate with the spindle, and the rotational movement of the spindle provides the necessary cutting speed for the workpiece; the workpiece can achieve transverse feed through the guide rail, so that the workpiece contacts the tool, and the tool can also perform transverse feed and cut along the surface of the workpiece to machine the required shape and size. The control system of the single-point diamond ultra-precision lathe is responsible for planning according to the given machining parameters and the tool machining trajectory to generate accurate motion commands, so as to achieve precise control of the relative displacement between the tool and the workpiece and complete the ultra-precision cutting of the workpiece.

[0037] During the machining process of a single-point diamond ultra-precision lathe, a large amount of heat will be generated during processes such as cutting and grinding. If it is not discharged in time, it will cause the temperature in the cutting area to rise, which will further affect the machining accuracy, equipment stability and service life. Therefore, cooling air is provided to take away the heat to maintain the normal working temperature of the lathe. However, blind spots will inevitably be generated during the working process of the cooling air, making the chips unable to be discharged normally and affecting the subsequent machining.

[0038] Moreover, in the prior art, when cutting the serrated tip, the lathe tool has a certain inertia and will generate a trajectory line with jitter due to sudden turning. The force of the servo motor cannot control the tool to reach the specified trajectory point, so there is an oscillating curve deviation between the actual trajectory and the theoretical trajectory. Therefore, it is necessary to improve the trajectory to achieve the purpose of machining an optical-grade mirror surface in one pass.

[0039] Figure 2 The double-dashed line part in the middle is a schematic diagram of the machining trajectory of a single-point diamond ultra-precision turning provided by an embodiment of the present invention. The single-point diamond ultra-precision lathe includes a single-crystal diamond tool, and the single-crystal diamond tool includes a blade. The running path of the cutting edge at the contact with the workpiece surface on the blade is taken as the machining trajectory, and the machining trajectory is used to cut the serrated tip of the workpiece; the machining trajectory includes two extension lines on both sides of the serrated tip and an arc, and the two ends of the arc are tangent to the two extension lines respectively; the diameter of the arc is greater than the maximum width of the chip generated by cutting the workpiece.

[0040] It should be noted that in this application, the running trajectory of the cutting edge at the contact with the workpiece surface when the tool exits is taken as the machining trajectory; other points can also be taken as the machining trajectory, but the contact parts of the tool and the workpiece surface during cutting-in and cutting-out need to be kept consistent. Correspondingly, the machining trajectory will also be scaled according to the ratio to avoid errors.

[0041] Among them, the maximum width of the chip is: at a specific tool translation speed, workpiece rotation speed, and cutting depth, the trajectory length of the cutting edge on the workpiece surface from the start of cutting into the workpiece surface to reaching the workpiece surface again when the workpiece rotates one circle; among them, the starting position of the cutting edge cutting into the workpiece surface is: the intersection of the workpiece surface and the perpendicular bisector of the tool translation line segment.

[0042] It should be noted that in this application, the running direction of the cutting edge is defined as the width direction.

[0043] The trajectory length can be approximately calculated in the following way:

[0044] See Figure 3 For the schematic diagram of the cutting process when the workpiece rotates one week, the running trajectory of the tool is simply represented by a circle, and the changes in the positions of the cutting edges are represented by two circles respectively. Assuming that the tool moves from right to left, the right part has been cut, the workpiece rotates with the main shaft, and the tool cuts the workpiece to make it a plane. The shaded part in the figure is the cutting section.

[0045] In this process, the cutting depth is set as H. During the time when the workpiece rotates one week, the tool makes a certain horizontal movement from right to left, that is, the center of the right circle moves leftward by a distance W to get the left circle, realizing the translation of the tool from the first position to the second position, and the distance between the first position and the second position is W.

[0046] If the radius corresponding to the cutting edge arc is R, set the auxiliary angles , and , which do not have actual physical meanings, is the angle between the vertical line and the line connecting the point where the cutting edge leaves the workpiece surface and the second position, is the angle between the vertical straight line and the line connecting the point when the cutting edge penetrates the workpiece surface and the second position. is the angle between the line connecting the point when the cutting edge leaves the workpiece surface and the second position and the line connecting the point when the cutting edge penetrates the workpiece surface and the second position. is and half of the sum of the angles. According to geometric relationships, the following formulas can be obtained respectively:

[0047] ,

[0048] ,

[0049] ,

[0050] During cutting, starting from the starting cutting point A, point A is the intersection of the workpiece surface and the perpendicular bisector of the tool translation line segment. The right side of point A is the machined plane, and the left side of point A is the part to be cut. The workpiece rotates continuously with the spindle, and the tool translates a distance W, which is calculated by the following formula:

[0051] ,

[0052] v is the tool translation speed, and t is the time for the workpiece to rotate one circle with the spindle. The workpiece and the tool cooperate with each other for relative displacement, so that the effect of the tool moving a distance W is finally obtained.

[0053] The end point of cutting is point B, which is the leftmost point where the tool and the workpiece contact and is also a point on the workpiece surface. Calculate the length of line segment AB to approximately estimate the maximum width M of the chip:

[0054] ,

[0055] Through the arc design, when each tooth is machined to the tip, the tool will lift to discharge chips, and the tool and the workpiece will be separated by a certain distance, which needs to be greater than the maximum width of the chip, so that the cooling air of the lathe blows the chips away from the workpiece surface and the tool tip; thus ensuring that there is no chip interference when cutting a new tooth profile, which is beneficial to improving the accuracy of the workpiece surface and improving the surface quality of the workpiece after cutting.

[0056] In this application, there is no restriction on the angle between the two sides of the serrated tip, and it can be within the range of 0° to 180°. See Figures 4 to 6 , which provides schematic diagrams of each machining trajectory under different settings of the angle between the two sides of the serrated tip. Obviously, the distance Q between the farthest end of the machining trajectory and the serrated tip must be greater than the maximum width of the chip, which is beneficial to the separation of the chips.

[0057] In this application, the machine tool precisely calculates and controls the movement trajectory of the cutting tool through an interpolation algorithm. The angle between the cutting blade and any side of the serrated tip is greater than or equal to 5°. The cutting blade includes a straight portion and an arc-shaped tip. For the straight portion, it needs to form a certain angle with the workpiece surface to facilitate meeting the cutting conditions at the tool tip, reducing frictional losses, and improving the rigidity and strength of the tool.

[0058] An object in motion will maintain a straight-line motion without the action of external forces. If you want to change the direction of motion, an external force needs to be applied to the object. The greater the mass of the object, the greater the external force required. The greater the angle of direction change, the greater the external force required. Since the direction of the cutting tool's movement trajectory has changed, work needs to be done to change the motion state of the cutting tool. Also, because the motion mechanism that drives the cutting tool on the machine tool is relatively heavy, sufficient external force needs to be applied to the cutting tool. During the motion process, there will be oscillations, and the generation of jitter should be avoided. The arc set in this application is a gradually changing vector of the applied force compared to other shapes, making the cutting process smoother, thereby optimizing the cutting speed, feed rate, etc., and further improving the processing efficiency.

[0059] Therefore, the smaller the included angle between the two sides of the serrated tip, if the required external force is insufficient, it is more likely to generate jitter, thereby affecting the workpiece accuracy.

[0060] In this application, the machining trajectory extends from one side of the serrated tip and then cuts in from the other side. The direction in which the cutting tool cuts into the workpiece again is straight, without changing the trajectory direction. Therefore, this direction is the direction that can bear the maximum stiffness of the serrated tip, which can maximize the integrity of the tip, keep the tip sharp, and avoid the influence of tool mapping accuracy and trajectory jitter on the tip.

[0061] In addition, referring to Figure 7 , in actual operation, the trajectory designed in this application will not move exactly according to the theoretical trajectory, and there will be a certain amount of jitter. The errors generated by turning are all set on the trajectory outside the tooling surface. The specific principle is as follows:

[0062] The equipment will generate a trajectory line with jitter due to sudden turning. Because the force of the servo motor cannot control the cutting tool to reach the specified trajectory point, when the theoretical trajectory is relatively straight in terms of bending degree, the actual trajectory line coincides more with the theoretical trajectory line. Therefore, this application places the errors caused by turning on the trajectory outside the workpiece surface.

[0063] Based on the above technical solutions, this application sets the turning error on the trajectory outside the workpiece surface, ensuring the integrity of the serrated tip, avoiding the generation of jitter, and meeting the design requirements of the workpiece shape; reducing the process of chips entering the cutting tool's movement trajectory to participate in machining, improving the accuracy; avoiding increasing the number of machining operations, saving time, labor, and cost.

[0064] Example 2

[0065] Based on the content of Example 1, the present application provides a processing method for single-point diamond ultra-precision turning. A processing method for machining a serrated tip according to the machining trajectory in Example 1 is specifically as follows:

[0066] The cutting edge of the single-crystal diamond tool extends along the extension line of one side of the serrated tip, and then cuts into the workpiece along an arc and enters the extension line of the other side of the serrated tip.

[0067] For other content, reference can be made to Example 1, and no further elaboration will be made here.

[0068] It should be noted that the terms used in the present invention are only for describing specific embodiments and do not limit the scope of the present application. As shown in the specification of the present invention, unless the context clearly indicates an exceptional situation, words such as "a", "an", "one" and / or "the" do not specifically refer to the singular and may also include the plural. The term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method or device comprising a series of elements not only includes those elements but also includes other elements not expressly listed, or also includes elements inherent to such process, method or device. Without further limitation, an element defined by the statement "comprising one..." does not exclude the existence of additional identical elements in the process, method or device comprising the said element.

[0069] It should also be noted that the orientation or positional relationship indicated by terms such as "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention. Unless otherwise clearly specified and limited, terms such as "installed", "connected", "connected to" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0070] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the technical solutions of the embodiments of the present invention.

Claims

1. A machining trajectory for cutting by a single-point diamond ultra-precision lathe, the single-point diamond ultra-precision lathe comprising a single-crystal diamond tool, the single-crystal diamond tool comprising a blade, the running path of the blade edge at the contact point with the workpiece surface being used as the machining trajectory, the machining trajectory being used for cutting a sawtooth tip of a workpiece; characterized in that: The machining trajectory includes two extension lines and an arc on both sides of the sawtooth tip, and the two ends of the arc are tangent to the two extension lines respectively; the diameter of the arc is greater than the maximum width of the chips generated by cutting the workpiece; The maximum width of the chip is: the length of the trajectory from the time when the blade cuts into the workpiece surface to the time when it reaches the workpiece surface again when the workpiece rotates one circle under a specific tool translation speed, workpiece rotation speed and cutting depth; The starting position of the cutting edge cutting into the workpiece surface is the intersection of the workpiece surface and the perpendicular midline of the tool translation line segment.

2. The machining trajectory of a single-point diamond ultra-precision lathe cutting according to claim 1 is characterized in that: The translation distance of the tool when the workpiece rotates one circle is W, the starting point of the tool movement is set as the first position, and the end point of the tool movement is set as the second position; the trajectory length M is calculated by the following formula: ， ， ， ， in, , and To set the auxiliary angle, is the angle between the vertical line and the line connecting the point where the blade leaves the workpiece surface and the second position, is the angle between the vertical line and the line connecting the point where the blade cuts into the workpiece surface and the second position, It is the angle between the line connecting the point where the blade leaves the workpiece surface and the second position and the line connecting the point where the blade enters the workpiece surface and the second position. R is the radius corresponding to the blade arc of the tool, and H is the cutting depth.

3. The machining trajectory of a single-point diamond ultra-precision lathe cutting according to claim 2 is characterized in that: The distance W between the first position and the second position is calculated by the following formula: ， Among them, v is the tool translation speed, and t is the time for the workpiece to rotate one circle.

4. The machining trajectory of a single-point diamond ultra-precision lathe cutting according to claim 1 is characterized in that: The angle between the two sides of the sawtooth tip is 0°~180°.

5. The machining trajectory of single-point diamond ultra-precision lathe cutting according to claim 1 is characterized in that: The angle between the blade and any side of the sawtooth tip is greater than or equal to 5°.

6. A single-point diamond ultra-precision lathe cutting method, characterized in that: A method for machining a sawtooth tip according to a machining trajectory cut by a single-point diamond ultra-precision lathe as described in any one of claims 1-5.

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