CN113618488B - A method of centering the center of rotation of the B-axis and the center of the circular arc of the cutting edge - Google Patents

Abstract

The invention discloses a centering method for a B-axis rotation center and a blade arc center, which is used for tool side device clamping. Use the tool swing machining method to cut out a complete structural unit on the surface of the workpiece, obtain the two-dimensional contour curve of the structural unit, and calculate the B-axis rotation center according to the two-dimensional contour curve; move the tool according to the calculated B-axis rotation center, If the X, Z position deviation after moving is within the acceptable range, then finish the fine tool setting, otherwise, repeat the fine tool setting process until the B axis rotation center and the X, Z position deviation of the blade arc center are within the acceptable range; In the present invention, the CCD camera is used for on-line tool setting, preliminary centering is performed, and then trial cutting is performed to perform precise tool setting, which can realize tool setting by means of side device clamping, and the precision tool setting process can quantify the error by calculation. , repeat the adjustment to achieve the desired accuracy.

Description

A method of centering the center of rotation of the B-axis and the center of the circular arc of the cutting edge

technical field

The invention relates to the technical field of ultra-precision machining, in particular to a method for centering a B-axis rotation center and a blade arc center.

Background technique

At present, there are CCD camera online tool setting and trial cutting method for tool nose and B-axis table rotation center alignment methods. Among them, the CCD camera online tool setting is to place the arc diamond tool in the field of view of the CCD camera, rotate the B axis to make the tool in three different positions, and move the tool to make the same point coincide with the center of the CCD field of view in these three positions. The three-point method automatically calculates the center of rotation of the B-axis, and the radius of the tool arc is known, so the tool position is adjusted so that the center of the arc of the blade coincides with the center of rotation of the B-axis. The B axis swings and moves along the X direction to cut out a groove. Since the arc radius is fixed, if the center of the tool coincides with the rotation center of the B axis, the depth of the cut groove is theoretically the same, but due to deviation, the depth of the cut groove If it is not uniform, it can be adjusted by calculating the deviation value of the center by the groove depth.

The above-mentioned existing tool setting method is only suitable for the tool clamping method with the rake face upward, and is not suitable for the tool setting of the blade arc center and the B-axis rotation center of the tool side device. Specifically, the CCD online tool setting is affected by the deviation of the placement angle of the CCD camera, the magnification of the lens and the focus definition. There is a certain error in the calculation of the insufficient accuracy of the B-axis rotation center, and the tool swing processing method for microspherical lens processing needs to be It is more difficult to accurately focus on the frontmost point of the cutting edge by using CCD observation after the tool side is clamped, and the resulting error is greater.

The Chinese patent with the application publication number CN 106001641 A discloses a tool setting device and tool setting method based on a laser-based virtual trial cutting method of a numerically controlled car. After the workpiece coordinate system is established with the reference tool, the adjustable laser device and The projection board confirms the diameter and length of the virtual workpiece, and uses the virtual workpiece as the "cutting" object to perform "trial cutting" tool setting. The tool setting process of this solution is similar to the actual trial cutting method, but it is far away from the real workpiece and will not happen. In the event of an accident, there is no need to measure each turning tool after turning the workpiece, as in the real trial cutting method, but directly input the coordinate value of the virtual workpiece after the turning tool is aligned with the reference point, which greatly reduces tool setting. However, this solution is limited to moving the turning tool to a known position, and cannot align the turning tool with the center of rotation where it is located.

The Chinese Patent Application Publication No. CN 111975021 A discloses a method for aligning an ultra-precision turning tool center with a B-axis rotary center. The ultra-precision turning device used includes an X-axis motion guide, a Z-axis motion guide, a main shaft, and a rotating platform. , Considering that the center of rotation of the rotating platform and the center of the tool need to be completely aligned, the virtual axis is introduced, that is, it is not necessary to completely align the center of rotation of the rotating platform and the center of the tool, but only the positional relationship between the two needs to be obtained. Compensate with the movement of the Z-axis motion guide rail to achieve complete alignment. This scheme no longer pursues forcibly aligning the tool center and the B-axis rotation center, but measures the relative positional relationship by trial cutting, through a series of mathematical calculations Therefore, the device can well achieve the target function even if the device is not aligned, that is to say, the solution only determines the relative position through trial cutting during initial use, and does not perform alignment in the actual sense.

Therefore, how to realize the centering of the B-axis rotation center of the tool side device and the center of the blade arc is an urgent technical problem to be solved.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a centering method for the center of rotation of the B-axis and the arc center of the blade, so as to solve the problems existing in the above-mentioned prior art, firstly use a CCD camera to perform on-line tool setting, perform preliminary centering, and then perform trial cutting and tool setting The precision tool setting can realize the tool setting method of the tool side device, and the precision tool setting process can quantify the error through calculation, and repeat the adjustment to achieve the expected accuracy.

For achieving the above object, the present invention provides the following scheme:

The invention provides a method for centering the B-axis rotation center and the arc center of the cutting edge, which is used for the tool side device clamping, and includes the following steps:

Coarse tool setting, use the CCD camera to set the tool online under the field of view of the CCD camera, and perform preliminary alignment;

Precise tool setting, use the tool swing machining method to cut out a complete structural unit on the surface of the workpiece, obtain the two-dimensional contour curve of the structural unit, and calculate the B-axis rotation center according to the two-dimensional contour curve;

Move the tool according to the calculated B-axis rotation center, if the X, Z position deviation after moving is within the acceptable range, then finish the fine tool setting, otherwise, repeat the fine tool setting process until the B-axis rotation center and the edge arc center X , Z position deviation is within the acceptable range.

Preferably, during rough tool setting, rotate the B-axis to make the tool in three different positions, at each position the tool tip coincides with the center of the CCD camera's field of view, calculate the B-axis rotation center position according to the three-point principle, move the tool, and realize B Preliminary alignment of the center of rotation of the shaft and the center of the circular arc of the blade.

Preferably, the three positions of the tool are spaced 90° apart.

Preferably, during fine tool setting, after cutting the workpiece, the tool needs to return to the position of rough tool setting before adjusting the tool movement.

Preferably, the structural unit is a concave ellipsoid.

Preferably, when cutting out the structural unit, the tool feeds a certain depth of cut in the Z direction, and rotates with the B axis to remove the workpiece material to complete the cutting.

Preferably, the two-dimensional contour curve is a contour curve formed by a tool nose trajectory.

Preferably, according to the two-dimensional contour curve, the center of rotation of the B-axis is calculated from three points of a given depth-of-cut position point, a cutting-in point of the tool, and a cutting-out point of the tool.

Preferably, the acceptable range is less than 1 μm.

Preferably, the 3D stereoscopic image of the structural unit is obtained by layer-by-layer scanning in the vertical direction with a 3D laser scanning microscope from Keyence, and then the 2D contour curve is obtained from the 3D stereoscopic image.

The present invention has achieved the following technical effects with respect to the prior art:

(1) In the present invention, the CCD camera is used for on-line tool setting, preliminary centering is performed, and then trial cutting is performed to perform fine tool setting, which can realize tool setting in the way of tool side device clamping, and the fine tool setting process is through the tool swinging. The machining method cuts out a complete structural unit and then obtains the two-dimensional contour curve of the structural unit. According to the two-dimensional contour curve, the B-axis rotation center can be calculated. The error can be quantified by calculation, repeated trial cutting, repeated calculation and adjustment can be achieve the desired accuracy;

(2) In the present invention, when performing rough tool setting, the three positions of the tool are designated as an interval of 90°, and the center position of the B axis can be calculated only by measuring the Z coordinate of the tool nose, which can avoid the measurement error caused by many parameters. It reduces the influence of measurement error and improves the accuracy of calculation results, so that more accurate rough tool setting effect can be obtained;

(3) In the present invention, the CCD camera is used for online tool setting to perform rough tool setting, and the trial cutting method is used to perform fine tool setting, and a tool setting method combining two tool setting methods is adopted, which can reduce the tool setting for the CCD camera. At the same time, it reduces the tedious steps of only using the trial cutting method for tool setting, which not only achieves higher tool setting accuracy but also reduces the operation steps of tool setting;

(4) In the present invention, the two-dimensional contour curve of the structural unit obtained by the trial cutting is obtained, and the B-axis rotation center is calculated on the two-dimensional contour curve through the three points of the given depth of cut position point, the cut-in point of the tool and the cut-out point of the tool , can use the mature algorithm for accurate calculation, and then obtain the accurate calculation result of the B-axis rotation center, and then adjust the position of the tool according to the calculation result, which can achieve accurate adjustment.

Description of drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the accompanying drawings required in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some of the present invention. In the embodiments, for those of ordinary skill in the art, other drawings can also be obtained according to these drawings without any creative effort.

Figure 1 is a schematic diagram of tool clamping and machine tool movement axes;

Fig. 2 is the enlarged schematic diagram at I place in Fig. 1;

Fig. 3 is a schematic diagram of a blade structure;

Figure 4 is a schematic diagram of the rough tool setting of the CCD camera;

Fig. 5 is the schematic diagram of fine knife setting by trial cutting method;

Among them, 1, the blade; 11, the tip; 12, the arc center of the blade; 2, the workpiece.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, but not 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 creative efforts shall fall within the protection scope of the present invention.

The purpose of the present invention is to provide a centering method for the center of rotation of the B-axis and the arc center of the blade, so as to solve the problems existing in the prior art. The fine tool setting can realize the tool setting by the tool side clamping method, and the precision tool setting process can quantify the error through calculation, and repeat the adjustment to achieve the expected accuracy.

In order to make the above objects, features and advantages of the present invention more clearly understood, the present invention will be described in further detail below with reference to the accompanying drawings and specific embodiments.

1 to 3, the present invention provides a method for centering the B-axis rotation center and the blade arc center 12, which is used for the tool side clamping. The tool side clamping means that the rake face is laterally clamped. and for the present invention, the cutting edge 1 of the tool is arc-shaped, having a cutting edge 11 (the frontmost point of the circular arc of the cutting edge 1 ) and a center 12 of the cutting edge circular arc. A tool position adjustment device consisting of X _B , Y _B , Z _B manual displacement table and tool holder can be installed on the B axis for tool setting adjustment, to ensure that the height of the tool nose 11 and the center of the C axis are consistent and the center of the blade arc 12 At the center of rotation of the B axis, the X _B , Y _B , and Z _B manual displacement stages can achieve high-precision adjustment with a stroke of 20 mm in three directions and a resolution of 1 μm. The tool rest is used for side clamping of swing turning tools. The alignment method includes the following steps:

For rough tool setting, the CCD camera is used for on-line tool setting under the field of view of the CCD camera. The tool setting method can adopt the method of on-line tool setting with CCD camera in the prior art. Specifically, the three-point method can be used to determine the B-axis rotation center by calculation. , perform preliminary alignment after moving the tool; it should be noted that since the CCD camera is located above the tool, and the tool is clamped on the side, therefore, after the tool is clamped on the side, it cannot be placed under the CCD camera. The arc of the blade 1 can be seen directly. At this time, the centering of the blade tip 11 can be achieved first, and then the length of the radius of the arc of the blade 1 can be moved to achieve the centering of the arc center 12 of the blade.

For precise tool setting, due to the inclination deviation and the limitation of resolution when the CCD camera is placed, after completing the preliminary adjustment of the blade arc center 12 and the B-axis rotation center, it is necessary to use the trial cutting method to make more accurate and quantifiable adjustments. ; Specifically, a complete structural unit is cut out on the surface of the workpiece 2 by using the tool swing machining method. The tool swing machining method here refers to the tool swinging along the B axis, moving from one side of the workpiece 2 to the other. In the process of one side, when it reaches the workpiece 2 from one side of the workpiece 2, the blade 1 contacts the workpiece 2 and cuts the workpiece 2 with the swing of the tool. After the blade 1 swings to the other side of the workpiece 2, it is completed. Oscillating cutting of workpiece 2; and since the position where the blade 1 contacts the workpiece 2 begins with an arc cutting process, a complete structural unit is a complete concave spherical surface (due to the existence of the blade arc center 12 and B The deviation of the relative position of the shaft rotation center, which is actually a concave ellipsoid); use 3D scanning or laser scanning to obtain a three-dimensional image of the structural unit, and then measure the two-dimensional contour curve of the structural unit, which is calculated from the two-dimensional contour curve ( For example, the center of rotation of the B-axis can be obtained after using the algorithm of determining the center of the circle with three points).

Move the tool according to the calculated B-axis rotation center. If the X and Z position deviations after moving are within the acceptable range, the fine tool setting is completed, and the tool setting process ends at this time. Otherwise, the fine tool setting process is repeated until the B axis rotates. The X, Z position deviation between the center and the blade arc center 12 is within an acceptable range. Therefore, the present invention can quantify the error through calculation, repeat trial cutting, and repeat calculation and adjustment to achieve the expected accuracy. The acceptable range mentioned here refers to the requirements related to the machining accuracy of the workpiece 2 . The invention uses the CCD camera to perform rough tool setting on-line, and uses the trial cutting method to perform fine tool setting, and adopts a tool setting method combining two tool setting methods, which can reduce the requirement for the CCD camera's tool setting accuracy. , At the same time, the tedious steps of only using the trial cutting method to set the knife are reduced, which not only achieves a higher precision of the knife, but also reduces the operation steps of the knife.

During rough tool setting, the tool setting process between the tool and the B axis is based on the principle of three points to determine the center of the circle. Under the field of view of the CCD camera, rotate the B axis to make the tool in three different positions. The cross marks at the center of the field of view of the CCD camera are coincident, so that the coordinates of the three positions are obtained by the CCD camera, and then the position of the rotation center of the B-axis is calculated according to the three-point principle, that is, the actual rotation of the tool is calculated according to the X and Z coordinates of the three different positions center (B-axis rotation center), and then move the tool to achieve preliminary alignment between the B-axis rotation center and the blade arc center 12.

If the X and Z coordinates of the three positions are measured, there are many parameters, and the introduced measurement error is large. In order to reduce the influence of the measurement error, the three positions of the tool are specified as the interval of 90°. At this time, only the tool tip 11 needs to be measured The Z coordinate of the B axis can be calculated to calculate the center position of the B axis.

As shown in Figure 4, in order to simplify the analysis process, the initial position of the blade 1 perpendicular to the spindle is set as the zero point A(0,0), and the tool is rotated 90° clockwise and counterclockwise respectively to obtain B(x ₁ , z ₁ ), C(x ₂ , z ₂ ), the coordinates of the B-axis rotation center are O(a,b).

The mathematical relationship between the three points A, B, and C and the coordinates of the circle center O is:

a ² +b ² =R ²

(x ₁ -a) ² +(z ₁ -b) ² =R ²

(ax ₂ ) ² +(bz ₂ ) ² =R ²

From the geometric relationship in the figure, x ₁ and x ₂ can be written as:

Substitute x ₁ and x ₂ into the previous formula, and the solution can obtain a and b in the center coordinate O, respectively:

That is, the coordinates of the center of rotation of the B-axis are:

Z方向移动

调整后，再次旋转B轴时，刀尖11在CCD视场下始终处于十字标记中心，再移动一个刀刃1圆弧的半径的长度，此时，便完成了刀具位置的粗调节，这一方法操作简单，且减小了测量误差对于对刀结果的影响。After calculating the rotation center of the B axis, use the X _B , Z _B stage to adjust the tool and move it in the X direction relative to the A(0,0) point position

Move in the Z direction

After adjustment, when the B-axis is rotated again, the tool tip 11 is always in the center of the cross mark under the CCD field of view, and then moves the length of the radius of the arc of the tool edge 1. At this time, the rough adjustment of the tool position is completed. This method The operation is simple, and the influence of measurement error on the tool setting result is reduced.

In the process of rough tool setting, since there is no need to cut the surface of workpiece 2, the tool is far away from the surface of workpiece 2, and for fine tool setting (tool setting by trial cutting method), the surface of workpiece 2 needs to be cut, and both X and Z directions need to be moved. A certain distance x' and z', therefore, during fine tool setting, the more accurate value calculated from the two-dimensional contour curve processed by trial cutting cannot be adjusted directly, but the X and Z axes of the machine tool should be returned to x' and z. ' distance, return to the position of rough tool setting, and then use the displacement table to adjust according to the calculated value, and then the process of fine tool setting can be completed.

For the structural unit obtained by trial cutting in the process of fine tool setting, a structural unit is a concave spherical surface. The size of the obtained concave spherical surface varies according to the depth of cutting. There is a deviation in the relative positions of the rotation centers of the 12 and B axes, which cannot be guaranteed to be an absolute concave sphere. Therefore, the structural unit obtained by trial cutting is actually a concave ellipsoid.

When cutting out the structural unit, the method of swing cutting is adopted, which requires the tool to feed a certain depth of cut in the Z direction, and then the tool rotates with the B axis, and the cutting edge 1 is used to contact the workpiece 2 to remove the material of the workpiece 2 to complete the cutting.

The two-dimensional contour curve obtained in the process of fine tool setting is the contour curve formed by the trajectory of the tool nose 11 , that is, the contour curve obtained by the tool nose 11 rotating around the B-axis rotation center to cut the workpiece 2 .

As shown in Figure 5, according to the two-dimensional contour curve, the center of rotation of the B-axis can be calculated according to the three-point method from the three points of the given depth of cut position point, the cutting point of the tool and the cutting point of the tool. Taking the surface of workpiece 2 as the 0 point in the Z direction, from the given Z-direction depth of cut position (x ₀ , z ₀ ), the cutting-in and cutting-out positions (x ₁ , 0) and (x ₂ , 0) of the rotation of the cutting edge 1 three Points are calculated by the following formula:

That is, the B-axis rotation center coordinate O(a ₁ , b ₁ ) obtained after the trial cutting is:

u, v, k ₁ , and k ₂ in the above formulas are the intermediate parameters of the calculation, and the substitute symbols used to simplify the formula have nothing to do with the calculation result.

Based on this, fine-tune the position of the arc center 12 of the blade, and repeat the trial cutting and calculation adjustment process until the calculated centering deviations in the X and Z directions are within the acceptable range. At this time, the structural unit cut out by the trial is an approximate A regular concave spherical surface, that is, the centering of the arc center 12 of the blade and the center of rotation of the B-axis is completed.

After the fine tool setting, the acceptable range can be less than 1μm, that is, after the fine tool setting, the precise tool setting is stopped when the relative position of the blade arc center 12 and the B-axis rotation center is less than 1μm.

When obtaining the two-dimensional contour curve of the structural unit, you can use the KEYENCE 3D laser scanning microscope (VK-X100) to scan layer by layer in the vertical direction to obtain the three-dimensional stereo image of the structural unit. For example, the scanning pitch in the z direction is 5nm, Then, the two-dimensional contour curve is obtained from the three-dimensional stereo image.

In the present invention, specific examples are used to illustrate the principles and implementations of the present invention, and the descriptions of the above embodiments are only used to help understand the method and the core idea of the present invention; There will be changes in the specific implementation manner and application scope of the idea of the invention. In conclusion, the contents of this specification should not be construed as limiting the present invention.

Claims (8)

1. a method for centering the center of rotation of the B-axis and the arc center of the blade, is characterized in that, for the tool side device clamping, comprising the following steps: Coarse tool setting, use the CCD camera to set the tool online under the field of view of the CCD camera, and perform preliminary alignment; For precise tool setting, use the tool swing machining method to cut out a complete structural unit on the surface of the workpiece, the structural unit is a concave ellipsoid, and obtain a two-dimensional contour curve of the structural unit, and the two-dimensional contour curve is the tool nose trajectory For the formed contour curve, calculate the center of rotation of the B-axis according to the two-dimensional contour curve; Move the tool according to the calculated B-axis rotation center, if the X, Z position deviation after moving is within the acceptable range, then finish the fine tool setting, otherwise, repeat the fine tool setting process until the B-axis rotation center and the edge arc center X , Z position deviation is within the acceptable range. 2. The centering method for the center of rotation of the B-axis and the arc center of the blade according to claim 1, characterized in that: during rough tool-setting, rotating the B-axis makes the tool in three different positions, and at each position the tool tip is equal to the The center of the CCD camera's field of view coincides, and the position of the B-axis rotation center is calculated according to the three-point principle, and the tool is moved to achieve the preliminary alignment of the B-axis rotation center and the center of the blade arc. 3 . The centering method for the center of rotation of the B-axis and the center of the circular arc of the blade according to claim 2 , wherein the three positions of the tool are separated by 90°. 4 . 4. The method for centering the center of rotation of the B-axis and the center of the blade arc according to any one of claims 1-3, characterized in that: during fine tool setting, the tool needs to return to the position of rough tool setting after cutting the workpiece. Perform tool movement adjustment. 5. The method for centering the center of rotation of the B-axis and the center of the circular arc of the blade according to claim 1, characterized in that: when cutting out the structural unit, the tool feeds a certain depth of cut in the Z direction, along with the B-axis Rotation removes workpiece material to complete the cut. 6. The centering method for the center of rotation of the B-axis and the center of the circular arc of the blade according to claim 1, characterized in that: according to the two-dimensional contour curve, a given depth of cut position point, a tool entry point and a tool cut out Point three points to calculate the B-axis rotation center. 7 . The centering method for the center of rotation of the B-axis and the center of the circular arc of the blade according to claim 4 , wherein the acceptable range is less than 1 μm. 8 . 8. The method for centering the center of rotation of the B-axis and the center of the blade arc according to claim 4, characterized in that: using a Keyence 3D laser scanning microscope to scan layer by layer in the vertical direction to obtain a three-dimensional image of the structural unit , and then obtain the two-dimensional contour curve from the three-dimensional stereo image.

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