WO2022095197A1

WO2022095197A1 - Blade grinding process for micro cutter

Info

Publication number: WO2022095197A1
Application number: PCT/CN2020/134494
Authority: WO
Inventors: 樊成; 张雷; 薛曹阳; 丁晨; 王可军; 王倩
Original assignee: 苏州大学
Priority date: 2020-11-04
Filing date: 2020-12-08
Publication date: 2022-05-12
Also published as: CN112318215A

Abstract

A blade grinding process for a micro cutter, the process comprising the following steps: A, selecting a grinding manner for machine tool machining according to a product to be machined; B, establishing an X-Y-Z coordinate system, simulating a machining motion path, and carrying out machining kinematics research; C, establishing a tool setting model according to the coordinate system, so as to determine a tool setting error and error compensation; and D, grinding said product. By modeling the material, shape, etc. of the cutter, a grinding manner, the kinematics of a machining machine tool, etc. are analyzed, such that an automatic machining and grinding method is provided, thereby improving the grinding efficiency and meeting the grinding repeatability of cutters of the same type, and guaranteeing the machining stability of batch products.

Description

A kind of sharpening process of miniature tool

technical field

The invention belongs to the technical field of medical instruments, and in particular relates to a sharpening process for a miniature tool.

Background technique

Micro scalpels are widely used in cardiovascular, neurosurgery, ophthalmology, otolaryngology and pathological examinations due to their advantages of smooth incision, no blind spot, low cross-infection rate, low safety risk, and little damage to patients. . Such as stenosing tenosynovitis, peripheral nerve entrapment syndrome, chronic injury and adhesion disease, joint stiffness, chronic strain and other diseases are very wide and numerous. After conservative treatment of these diseases fails, surgical soft tissue release treatment is often used. It is one of the main surgical methods and the mainstream of surgical treatment in recent years. Minimally invasive surgery is inseparable from minimally invasive tools. At present, the tools used for minimally invasive soft tissue release mainly include small needle knives and arthroscopes. The cutting edge of some microsurgery knives needs to be ground and formed on both sides. The traditional method uses a cylindrical knife handle with a rotary chuck for clamping. The traditional grinding methods are mostly manual grinding, with poor product consistency and low efficiency.

SUMMARY OF THE INVENTION

The sharpening process of the micro-knife of the present invention builds an automatic four-axis linkage machine tool by itself in view of the disadvantages of the traditional grinding method, studies the sharpening method and process of the micro-scalpel, analyzes the possible errors in the machining of the workpiece, and proposes a A new type of sharpening method can effectively improve the problem of grinding and polishing micro scalpels.

The sharpening process of the micro-tool of the present invention includes the following steps (it should be noted that the steps A, B, C, and D here are not strictly specified sequences, and can be adjusted according to actual operations),

A. Select the grinding method of machine tool processing according to the product to be processed, and the product to be processed includes one edge or two edges;

B. Establish an XYZ coordinate system, simulate the processing motion trajectory, conduct processing kinematics research, and determine the contact trajectory of the grinding tool (the coordinate system takes the vertex of the edge of the product to be processed as the origin O, and the direction of the spindle axis is the X axis direction, the direction of the line connecting the O point and the center of the grinding wheel is the Y-axis direction, and the Z-axis is perpendicular to XY, the specific direction selection depends on the demand), where the origin O coordinate is expressed as

For example, when a contemporary machined product has two symmetrical edges, the Y axis passes through the center line between the two edges; C. According to the coordinate system, establish a tool setting model, determine the tool setting error and error compensation, and obtain the tool contact coordinates vector is

Among them, xi, yi, and zi are the position representation of the tool contact in the machine tool, respectively, and li, mi, and ni are the respective components of the normal vector of the tool contact in the x-axis, y-axis, and z-axis directions, and determine the position of the tool contact. Processing kinematic model:

And the motion amount of each axis is obtained as γ=-sin ^-1 l _i or γ=cos ^-1 m _i , where dx, dy, and dz are the mathematical expressions of the motion of the x-axis, y-axis, and z-axis of the machine tool, and γ is is the C-axis rotation angle of the machine tool, Rp is the outer diameter of the grinding wheel used by the machine tool; θ is the edge inclination angle of the machined micro-tool, and L is the distance from the center of the grinding wheel to the center of rotation;

D. Grinding the products to be processed.

An improvement of the sharpening process of the micro-tool of the present invention, in step C, when the tool contact is translated in the XYZ coordinate system, the DH transformation is adopted and satisfies A _j =Trans(d _x , _dy ,d _z )A _i ,in

An improvement of the sharpening process of the micro-tool of the present invention, in step C, when the tool contact is rotated around the Z axis, the DH transformation is adopted and A _j =Rot(z,γ)A _i is satisfied, wherein

An improvement of the sharpening process of the micro-tool of the present invention, the confirmation of the tool-setting error in step C includes: the tool-setting error in the X-axis direction and/or the tool-setting error in the Y-axis direction and/or the Z-axis direction tool setting error.

An improvement of the sharpening process of the micro-tool of the present invention, the tool-setting error in step C is mainly the tool-setting error Δy in the Y-axis direction.

An improvement of the sharpening process of the micro-tool of the present invention, in the tool-setting model of step C, the tool-setting error Δy is a function with Δt as an independent variable.

An improvement of the sharpening process of the micro-tool of the present invention, the tool-setting error Δy in the tool-setting model in step C satisfies

Among them, θ is the inclination angle of the blade, and h, R, and d are the known constants calculated according to the drawings of the OEM products.

In an improvement of the sharpening process of the micro-tool of the present invention, the selection basis of the grinding method in step A includes at least one of the material information of the product to be processed and the shape information of the product to be processed.

An improvement of the sharpening process of the micro-tool of the present invention, the grinding method in step A includes clockwise grinding or counterclockwise grinding.

The solution of the present invention provides an effective automatic machining and grinding method by modeling the material, shape, etc. of the tool, so as to analyze the grinding method, the kinematics of the machine tool, etc., so that to a great extent While improving the grinding efficiency, it also satisfies the repeatability of the same type of tool grinding, and ensures the stability of batch product processing.

Description of drawings

In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the accompanying drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only These are some embodiments described in this application. For those of ordinary skill in the art, other drawings can also be obtained based on these drawings without any creative effort.

Fig. 1 is a schematic diagram of a micro-surgical knife sharpening process flow diagram in a specific embodiment of the present invention;

Fig. 2 shows the grinding method of the grinding wheel in the specific embodiment of the present invention;

Fig. 3 shows the simulated trajectory of machine tool processing in a specific embodiment of the present invention;

Fig. 4 shows the representation method of the edge inclination angle on the grinding wheel in the specific embodiment of the present invention;

FIG. 5 is a schematic diagram of the tool setting point error in a specific embodiment of the present invention;

6 is a schematic diagram of an error compensation method in a specific embodiment of the present invention;

FIG. 7 is a schematic diagram showing the error of the knife contact point in the specific embodiment of the present invention.

Detailed ways

The present invention will be described in detail below with reference to the various embodiments shown in the accompanying drawings. However, these embodiments do not limit the present invention, and the structural, method, or functional transformations made by those of ordinary skill in the art based on these embodiments are all included in the protection scope of the present invention.

The sharpening process of the miniature cutter of the present invention comprises the following steps:

First, select the grinding method during machine tool processing according to the material of the product to be processed, such as stainless steel. For example, for the product to be processed made of stainless steel, you can choose a counterclockwise grinding method. The product to be processed includes one blade or two blades. Micro scalpels generally have two blades, such as a lancet shape;

Clamp the product to be processed on the machining fixture of the machine tool, take the vertex of the edge of the product to be processed as the origin O, take the direction of the spindle axis as the X-axis direction, and take the direction of the line connecting the O point and the center of the grinding wheel as the Y-axis direction , the Z axis is perpendicular to XY, and the XYZ coordinate system is established in the processing space of the machine tool. In the coordinate system, the existing shape parameters of the product to be processed and the shape parameters of the target product that needs to be processed, that is, the product to be processed is in The state before and after processing is modeled, the processing motion trajectory is simulated, the processing kinematics research is carried out, and the contact trajectory of the grinding tool such as the grinding wheel is determined. Here, the origin O coordinate is set as

When the contemporary processing product has a micro scalpel with two blades, the Y-axis can pass through the center line between the two blades in the state of symmetry of the two blades, otherwise it will pass through the vertex formed by the two blades (ie the tip);

In the above coordinate system, based on the model of the product to be processed before and after processing, combined with the operating parameters of the grinding tool including the contact trajectory, etc., the tool setting model is established, and the appropriate tool setting error is determined and selected (here The tool setting error can be confirmed in the X-axis, Y-axis, and Z-axis directions, that is, there may be tool-setting errors in the X-axis direction and/or tool-setting errors in the Y-axis direction and/or alignment errors in the Z-axis direction. Multiple possibilities for tool error.

In this scheme, after confirmation, it can be found that the tool setting error is mainly the tool setting error Δy in the Y-axis direction, and the tool setting error Δy is a function with Δt as the independent variable.

Among them, θ is the blade inclination angle, h, R, and d are known constants calculated according to the drawings of the OEM product) and establish an error compensation scheme. Here, the coordinate vector of the tool contact is set as

According to the solution conclusion, the machine tool is set, the products to be processed are ground, and the processed products are inspected as qualified products. In the repeated production of batches, the quality of batch products has good repeatability.

In the above scheme, in step C, when the tool contact is translated in the XYZ coordinate system, DH transformation is adopted and A _j =Trans(d _x , d _y , d _z )A _i is satisfied, where

At the same time, when the knife contact is rotated around the Z axis, DH transformation can also be used to satisfy A _j =Rot(z,γ)A _i , where

As a demonstration of a more specific implementation:

With reference to Fig. 1, the present embodiment proposes a sharpening process for a micro-tool, including the steps:

1. The choice of grinding wheel grinding method;

2. Machine tool kinematics analysis;

3. Selection of tool setting method;

4. Tool setting error analysis and compensation.

Combined with Fig. 2, the machine tool adopts counterclockwise grinding method during processing. The workpiece material is stainless steel. When clockwise grinding is used, due to the good toughness of stainless steel, the workpiece will be "pulled" outward, which will affect the sharpness of the workpiece, so counterclockwise grinding is used.

Figure 3 shows the simulated trajectory of machine tool processing, and the vertex of the workpiece is used as the origin of the workpiece coordinate system.

The coordinates and vectors of the origin O of the workpiece coordinate system are:

The knife contact coordinates and vectors can be expressed as:

xi, yi, and zi are the positions of the tool contacts in the machine tool, respectively, and li, mi, and ni are the respective components of the normal vector of the tool contacts in the x-axis, y-axis, and z-axis directions.

At this time, as long as the tool contact coordinates coincide with the transformed origin coordinates and vectors, the machining can be completed. Vector coincidence means that the actual coordinates and directions are consistent, that is, the left and right sides of the kinematic formula are equal.

It can be seen from the D-H transformation that the formula for translational transformation along the X, Y, and Z axes is:

A _j =Trans(d _x , _dy ,d _z )A _i .

Here is the expression for the coordinate transformation of the machine center point along the x-axis, y-axis, and z-axis. Ai and Aj are the general representation methods of the points before and after the coordinate transformation, and do not need to be actually expressed.

in

At this point, the formula for the rotation transformation around the Z axis is:

A _j =Rot(z,γ)A _i

As mentioned above, this is the expression of the coordinate transformation of the center point of the machine tool rotating around the C axis. Ai and Aj are the general representation methods of the points before and after the coordinate transformation, and do not need to be actually expressed. γ is the C axis rotation angle.

in

When this machine tool is processing, the rotation center of the grinding wheel is point a, not point b. Therefore, at the beginning of the calculation, the coordinates of point a are calculated first, then rotated, and then translated, and finally the coordinates of point a' are translated to coincide with the contact point of the tool.

The processing process shown in FIG. 3 is a simulation of the movement process of the grinding wheel. During the processing, the workpiece is fixed on the worktable, and the grinding wheel moves along the trajectory of the workpiece. The idea of solving the kinematics formula is to make the coordinate system of the workpiece coincide with the coordinate system of the grinding wheel, so that the coordinate transformation is performed to coincide the tool and the contact point of the workpiece knife. Since the grinding wheel moves with the spindle of the machine tool during the movement, the rotation center of the grinding wheel is not the center point b of the grinding wheel, but point a on the spindle of the machine tool. Point a and the center point b of the grinding wheel are on the same straight line, so in When solving the kinematic inverse solution formula, the calculation should start from point a. First calculate the coordinates of point b, transform to point a through translation, and then perform rotation transformation, and finally translate point a' to coincide with the contact point of the workpiece tool, so the kinematics formula of machine tool processing is:

L is the distance from the center of the grinding wheel to the center of rotation, that is, the length of the line segment ab; Rp is the outer diameter of the grinding wheel used by the machine tool; θ is the edge inclination angle of the machined micro-tool; the rest of the parameters are consistent with the above. The rotation direction of the grinding wheel is perpendicular to the workpiece, and the workpiece is placed on the worktable parallel to the ground; point b is the center point of the grinding wheel, point a is the center of rotation of the grinding wheel, and the distance from the grinding wheel to the spindle is the length of ab, namely L .

Calculate the movement amount of each axis, that is, the inverse solution formula of machine tool kinematics:

Tool grinding and polishing should first consider the edge inclination angle θ of the blade. The blade inclination angle affects the sharpness of the tool to a certain extent. The blade inclination angle is also an important basis for us to calculate the position of the tangent point. Since the radius of the grinding wheel is much larger than the size of the workpiece blade trajectory, the grinding wheel is in The cutting surface formed by the surface of the workpiece can be approximately regarded as a plane. The angle between the plane and the horizontal plane is the inclination angle of the blade, and it is also the angle between the tangent of the cutting point and the horizontal plane. Therefore, it is concluded that the inclination angle of the blade is the connection between the cutting point and the center of the circle. The line forms an angle with the negative Z-axis, as shown in Figure 4.

When the edge inclination angle is determined, the relationship between the theoretical Z coordinate Z ₁ of the cutting point and the Z coordinate Z ₂ of the lowest point of the grinding wheel is as follows, and the grinding wheel radius is Rp:

Z ₁ =Z ₂ -(R _p -R _p *cosθ) (1)

When setting the tool, first rotate the C-axis (the C-axis refers to the axis that rotates around the Z-axis axis) to the mechanical coordinate 90° position (the position where the 0 point in Figure 3 is perpendicular to the paper), and shake the handwheel to adjust the center line of the grinding wheel and The center line of the tool coincides. At this time, the grinding wheel is lowered to the lowest point. When the grinding wheel just touches the tool, Z ₂ is obtained, and Z ₁ is obtained by formula (1), which is input into the workpiece coordinate system of the CNC system. Considering the thickness of the workpiece, it is also necessary to compensate the Z coordinate by about 0.1mm to reduce the error. After getting the Z coordinate, adjust the C axis to the 0° position of the mechanical coordinate, drop the Z to Z ₁ coordinate, and bring the grinding wheel close to the tool. When the grinding wheel touches the tool tip, record the corresponding X and Y coordinates, and input them into the numerical control system. On the knife. A large number of experiments have shown that due to the error of the tool setting, the processed workpiece must have errors with the required processing results. This error can be seen from the analysis that the tool setting error of the Z coordinate can be ignored, and because the grinding wheel has a certain thickness, it ensures that the tool setting error of the X axis can also be ignored, so the Y coordinate error has the greatest impact on the machining results. Denoted as Δy.

During the machining process, even if the machining trajectory deviates from the ideal trajectory, the grinding wheel will still grind a section of the blade trajectory surface with errors on the workpiece. Such trajectory must have errors, which needs to be calculated according to the feedback information of the processed workpiece. How much should be compensated for the Y coordinate of the tool setting point? Even if the compensation data cannot be very accurate, the compensated trajectory must be very close to the ideal trajectory. At this time, it is only necessary to use a microscope to observe the sharpening degree of the cutting edge and make fine adjustments to quickly get the ideal trajectory.

Taking the right arc edge as the research object, the tool setting error compensation formula is deduced. In the previous analysis, it is concluded that the error of the Y coordinate of the tool setting point is the main consideration. According to the processing principle described above, it is easy to know that the errors of different tool contacts on the same blade are the same Δy, as shown in the figure Errors between trajectory 2, trajectory 3, trajectory 4 with errors shown in 5, and ideal trajectory 1.

In the research process, take any contact point as an example. Project the processed workpiece into the plane (the plane is the plane of the paper where Figure 6 is located, the axis of the workpiece is parallel to the plane, and the blade of the workpiece is perpendicular to the plane of the paper), in the direction perpendicular to the axis of the workpiece, or In the Y-axis direction of the workpiece coordinate system, take a straight line. The vertical distance between this line and the tool tip is l, referred to as the L line. At the same time, the L line must intersect with the two edges of A and B, and the intersection point with the outside of the right arc edge is marked as C. , the inner intersection is recorded as B. Since the workpiece blade trajectory is an arc, a complete circle is filled, the center of the circle is O, the intersection of the vertical line from O to L is recorded as A, and the radius OD (length is recorded as R) is drawn to pass point B , and the blade trajectory intersects with point D. Point D is a certain knife contact point of the right circular arc edge obtained by the arbitrarily selected L line. The schematic diagram is shown in Figure 6. At this time, the overall tool setting can be obtained by studying the error of point D. error. According to the parameters on the workpiece drawing, the quantity that can be obtained is the thickness h of the workpiece at the positions of points OA, R, l and B, the length of OA is recorded as d, and the value of line segment BC is the data to be measured, recorded as Δt;

According to the established mathematical model, the length of AC can be known as:

So, the length of AB is:

According to the Pythagorean theorem, the length of OB can be obtained as:

According to these data, the length of line segment BD can be deduced as:

The workpiece is cut along OD, and the possible machining results of the cutting edge section of the tool contact D are shown in Figure 7.

The value of the error Δy is the difference between the ideal BD width and the actual BD width, then the expression of Δy is as follows:

Δy is a function with Δt as the independent variable. In the formula, h, R and d are calculated according to the parameters on the workpiece drawing, which are regarded as known quantities. The blade inclination angle θ is selected before machining and is also a known constant. Similarly, the error compensation method and formula of edge B are the same as those of edge A.

The concept of L line was introduced in the previous article. At the same time, it is also known that for the same tool setting error value, the Δy corresponding to any L line is the same. From the content of the previous section, BD ₁ corresponding to L ₁ is:

BD ₂ corresponding to L ₂ is:

Since Δl _actual =BD ₁ -BD ₂ , Δl _actual and Δl _theory are respectively:

α——Cutter face slope angle

Therefore, in theory, the difference between the actual values of BD corresponding to different L lines has nothing to do with Δy, and is only affected by the value of l, so Δl _actual = Δl _theory . The influencing factors of the actual value of BD are demonstrated here.

It will be apparent to those skilled in the art that the present invention is not limited to the details of the above-described exemplary embodiments, but that the present invention may be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments are to be regarded in all respects as illustrative and not restrictive, and the scope of the invention is to be defined by the appended claims rather than the foregoing description, which are therefore intended to fall within the scope of the claims. All changes within the meaning and scope of the equivalents of , are included in the present invention.

In addition, it should be understood that although this specification is described according to embodiments, not every embodiment only includes an independent technical solution, and this description in the specification is only for the sake of clarity, and those skilled in the art should take the specification as a whole , the technical solutions in each embodiment can also be appropriately combined to form other implementations that can be understood by those skilled in the art.

Claims

A kind of sharpening process of miniature cutter is characterized in that, comprises the following steps,

A. Select the grinding method of machine tool processing according to the product to be processed, and the product to be processed includes one edge or two edges;

B. Establish an XYZ coordinate system, simulate the processing motion trajectory, conduct processing kinematics research, and determine the contact trajectory of the grinding tool, where the origin O coordinate is expressed as

C. According to the coordinate system, establish a tool setting model, determine the tool setting error and error compensation, and obtain the tool contact coordinate vector as
Among them, x i , yi , and zi are the positions of the tool contacts in the machine tool, respectively, and li , m i , and ni are the respective components of the normal vector of the tool contacts in the x-axis, y-axis, and z-axis directions. And determine the machining kinematic model of the tool contact:
The motion of each axis is obtained as
Among them, d x , dy , d z are the mathematical expressions of the motion of the x-axis, y-axis, and z-axis of the machine tool, γ is the rotation angle of the machine tool C-axis, R p is the outer diameter of the grinding wheel used by the machine tool; θ is the machine tool. The inclination angle of the micro-tool, L is the distance from the center of the grinding wheel to the center of rotation;

D. Grinding the products to be processed.
The sharpening process of the miniature cutter according to claim 1, is characterized in that, in the step C, when the cutter contact does translation transformation in the XYZ coordinate system, DH transformation is adopted and satisfies A j =Trans(d x ,dy y ,d z )A i , where
The sharpening process of the miniature cutter according to claim 1, characterized in that, in the step C, when the cutter contact is rotated around the Z axis, DH transformation is adopted and A j =Rot(z,γ) A i , where
The sharpening process for a micro-tool according to claim 1, wherein the confirmation of the tool-setting error in the step C includes: the tool-setting error in the X-axis direction and/or the tool-setting error in the Y-axis direction and / or tool setting error in the Z-axis direction.
The sharpening process for a micro-tool according to claim 4, wherein the tool-setting error in the step C is mainly the tool-setting error Δy in the Y-axis direction.
The sharpening process for micro-tools according to claim 5, characterized in that, in the tool-setting model of step C, the tool-setting error Δy is a function with Δt as an independent variable.
The sharpening process for micro-tools according to claim 6, wherein the tool-setting error Δy in the tool-setting model in the step C satisfies
Among them, θ is the inclination angle of the blade, and h, R, and d are the known constants calculated according to the drawings of the OEM products.
The sharpening process for micro-tools according to claim 1, wherein the selection of the grinding method in the step A includes at least one of the material information of the product to be processed and the shape information of the product to be processed. .
The sharpening process for a micro-tool according to claim 1 or 8, wherein the grinding method in step A includes clockwise grinding or counterclockwise grinding.