CN101983838B - Milling, grinding and polishing device based on intelligent numerically-controlled platform - Google Patents

Abstract

The invention belongs to the technical field of modern optical processing, and specifically relates to a milling, grinding and polishing device based on an intelligent numerical control platform. The device is composed of an industrial robot and its control module, a drive module, a man-machine interface, working components, a polishing coolant circulation control system and a suction cup fixture. Among them, the control module and the drive module control and drive the spatial movement and spatial positioning of the industrial robot, thereby controlling the working state of the working component, that is, the grinding/polishing module; the control module also controls the man-machine interface, and controls the circulation control of the polishing fluid and cooling fluid. The stirring device, temperature control device and conveying device of the system; the suction cup fixture is used to clamp the workpiece. The invention has the advantages of low manufacturing cost, large processing caliber, wide processing surface type, and two functions of grinding and polishing can be realized by replacing the grinding head.

Description

Milling and polishing device based on intelligent numerical control platform

technical field

The invention belongs to the field of modern optical processing technology, and specifically relates to a milling and polishing device based on computer control (CNC), in particular to a milling and polishing device for large-diameter aspherical surfaces, planes, spherical surfaces, and optical parts with complex structures.

Background technique

Computer Controlled Optical Surface Shaping (CCOS) technology includes milling in the rough machining stage and polishing in the finishing stage. This technology emerged in the 1970s, thanks to the rapid development of computer technology and software technology, it has been widely used in the optical processing industry.

The characteristics of computer-controlled optical surface molding technology are: the processing process is completely controlled by the computer, the human influence factor is low or does not exist, the processing process is easy to control, the processing efficiency is high, the reliability is good, and the shape accuracy is easy to control; the range of surface types that can be processed is wide , can process various complex surface types including plane, spherical, rotationally symmetrical aspheric, off-axis aspheric, free surface and so on.

Computer-controlled optical surface forming technology uses a computer to control a grinding head or polishing head that is much smaller than the workpiece to move on the surface of the workpiece. The residence time of a region can be controlled to control the amount of material removal, so as to achieve the purpose of correcting the surface shape of the optical element. Using computer to process data is fast, control is accurate, and memory is reliable. Specific algorithm control can greatly improve work efficiency and processing quality, and reduce dependence on operator technology and experience. Therefore, it has broad development prospects and can improve advanced optical technology. manufacturing competitiveness.

However, the current optical processing equipment based on computer-controlled optical surface molding technology is basically dependent on imports. Whether it is a milling machine or a polishing machine, it costs millions or even tens of millions of dollars, and the price is extremely expensive. The present invention uses a mature commercial 6-axis industrial robot, integrates the grinding and polishing movement mechanism, the grinding cooling liquid or polishing liquid circulation control system and advanced algorithms to construct a cost-effective CCOS system, and provides a brand-new grinding and polishing equipment for optical parts. Save at least half of the cost under the premise of ensuring the same performance.

Contents of the invention

The purpose of the present invention is to overcome the disadvantages of current CCOS equipment such as insufficient flexibility, limited space, unadvanced algorithm and high price, and provide a brand-new milling and polishing device for optical parts.

Compared with the current commercial CCOS machine tool, the biggest advantage of this device is that it is low in cost, has a large processing caliber, can process a wide range of surfaces, and can realize two functions of grinding and polishing by replacing the grinding head. It has the characteristics of wide versatility, high processing efficiency, easy control and operation, simple structure, and deterministic grinding and polishing of various surface types.

The milling and polishing device provided by the present invention consists of a mature commercial industrial robot 1 (such as ABB, FANUC, Motoman, KUKA and other company products) and its control module, drive module, human-computer interaction interface, working component 4, and polishing cooling fluid circulation. A control system (including a storage device 9, a stirring device 8, a temperature control device 7, a delivery pump 6 and a return pump 10) and a suction cup fixture 11 are formed. Its composition structure block diagram like chart 1 shows. Among them, the control module and the driving module control and drive the spatial movement and spatial positioning of the commercial industrial robot 1, thereby controlling the working state of the working component, that is, the grinding/polishing module 4; the control module and the driving module also control the man-machine interface, and simultaneously control The storage device 9, the stirring device 8, the temperature control device 7, the delivery pump 6 and the return pump 10 of the polishing liquid cooling liquid circulation control system; the suction cup clamp 11 is used for clamping the workpiece.

The mechanical connection relationship of the milling and polishing device provided by the present invention is shown in FIG. 2 . The figure shows the connection relationship between the robot system and the working components and the cooling/polishing liquid circulation control system. The working component 4 is installed on the "wrist" of the robot 1 through the flange 3; the tool head 13 is located below the working component 4, and the tool head 13 (milling head or polishing head) is ground or polished under the control of the working component 4 Polishing action; a force sensor 2 is also installed between the flange 3 and the "wrist" of the robot to monitor and control the grinding or polishing force that the tool head 13 of the working component 4 acts on the workpiece 12.

Figure 3 shows a schematic diagram of the composition of the polishing coolant (liquid) circulation control system. The polishing coolant circulation control system includes a storage device 9, a stirring device 8, a temperature control device 7, a delivery pump 6 and a return pump 10; the storage device 9 is a box structure for storing liquid (that is, polishing coolant), and its cover The delivery pump 6, temperature control device 7, stirring device 8 and return pump 10 are installed on it; the delivery pump 6 transports the liquid from the storage device 9 to the working area (that is, the workpiece processing place) through the pipeline 5; the temperature control device 7 adopts a temperature The sensor, which is connected to the control module, is used to detect and control the temperature of the liquid, that is, the temperature sensor transmits the real-time temperature of the liquid to the control module, and when the temperature of the liquid is higher than the set temperature, it will be cooled, otherwise it will be heated; the stirring device 8 is used To stir the liquid, prevent the deposition of the processing medium, and keep the liquid concentration uniform; the return pump 10 is used to suck back the excess liquid in the working area to the liquid storage device 9 .

In the present invention, the industrial robot 1 can realize 6-axis linkage (vertical arm rotation, vertical arm swing, horizontal arm rotation, horizontal arm swing, wrist rotation, wrist swing), through the drive module of the robot system, and cooperate with the control software to make It is more in line with the needs of optical precision processing. That is, the position of the milling head or polishing head in space, the contact area with the workpiece, the dwell time at the working point and the feed movement mode (oscillating + rotating + spiral or grid) can be precisely controlled through the force sensor 2 and control software. Lattice polishing track design). According to different workpieces or different requirements, different working components (milling/polishing modules) are used and connected to the robot "wrist" through the flange 3. The working components carry out self-rotation and horizontal swing motion through the planetary motion structure, and perform grinding or polishing actions, and the speed and swing range can be adjusted. The tool head 13 moves on the surface of the processed workpiece with a removal function controlled by a specific algorithm, and the material removal amount at each point on the surface of the processed workpiece 12 is controlled by the dwell time of the tool head 13 at this point. The working pressure applied by the tool head 13 to the workpiece 12 is monitored and adjusted by the force sensor 2 to ensure the safety of the workpiece 12 and the constant working pressure. So as to ensure the stability of the removal rate during the processing and ensure the stable progress of the processing. The polishing cooling liquid is transported to the working area through the liquid delivery pipe 5 , and the excess liquid is recycled to the liquid storage tank 9 through the return pump 10 .

The following is the material removal theoretical basis of the present invention:

1. Milling.

a. For plane and spherical

When processing a plane or spherical surface, according to the principle of Fancheng method, that is, when a ring with a radius of r moves relative to a point, the trajectory envelope surface of all points on the ring is a spherical surface, and the radius of curvature of the spherical surface is any point on the ring distance to a fixed point. The fixed point is the center of the spherical surface to be processed, and the center of the circle is considered to be at infinity for the planar workpiece. When the radius r of the ring is constant, changing the distance from any point on the ring to a fixed point will change the radius of curvature of the trajectory enveloping the spherical surface accordingly, forming spherical surfaces with different curvature radii.

b. For aspheric and free surfaces

The diamond cylindrical grinding wheel is based on the following principle when milling a symmetrical aspheric workpiece: the diamond grinding wheel contacts the workpiece in a point contact manner, and the trajectory of the point in space is the meridian profile of the symmetrical aspheric surface. At the same time, the processed workpiece rotates around the axis of symmetry, and the obtained surface is the required symmetrical aspheric surface. The diamond grinding wheel is based on the following principle when processing free-form surface workpieces: the diamond grinding wheel contacts the workpiece in a point contact manner, and the workpiece remains stationary. The trajectory of the contact point between the diamond grinding wheel and the workpiece in space is a grating motion. The envelope surface formed by the path is the surface shape of the workpiece to be processed.

When processing other shapes or complex surfaces, it can be carried out according to the working method of ordinary milling machines, and different milling tools can be replaced according to needs.

2. Polishing.

The theoretical basis of CCOS technology is based on the Princeton (Preston) assumption and linear theory derivation. According to the Preston assumption, the material removal function of a small grinding head tool at a certain point (x, y) can be expressed by the following formula:

                 （1）

(1)

为该点的材料去除率，

为该点的压强，

为在该点工件与小磨头的相对运动速度，是工艺因子，包含了除压强、相对运动速度之外的所有因素。 in

is the material removal rate at that point,

is the pressure at that point,

is the relative velocity of the workpiece and the small grinding head at this point, It is a process factor, including all factors except pressure and relative motion speed.

According to the Preston assumption, it is possible to establish a material removal amount at a point (x, y) within a time t The mathematical model of:

                     （2）

(2)

代入上式得： Will

Substitute into the above formula to get:

             （3）

(3)

It can be seen that the material removal amount at a certain point (x, y) is the convolution function of the material removal rate function at this point with respect to time.

Assuming that the removal rate remains constant throughout the polishing process, the above formula can be simplified as:

                （4）

(4)

是根据Preston假设推导出的运动特征去除函数；

是驻留时间函数。由公式可知，一旦知道了抛光模运动的特征去除函数和驻留时间函数，在加工的时候只要控制工具在每点的驻留时间就可以精确的控制该点的材料去除量。 In the formula,

is the motion feature removal function derived from the Preston assumption;

is the dwell time function. It can be seen from the formula that once the feature removal function and dwell time function of the polishing die movement are known, the amount of material removal at that point can be precisely controlled as long as the dwell time of the tool at each point is controlled during processing.

来获得每点所要求的材料去除量，从而达到修正面型的目的。 When processing according to this theory, an appropriate removal function is selected, and the residence time of the polishing head at each point is controlled by analyzing the surface data obtained from the measurement feedback.

To obtain the material removal amount required by each point, so as to achieve the purpose of correcting the surface shape.

Generally speaking, the ideal removal function needs to have the following characteristics: (1) It is a continuous smooth function with rotational symmetry; (2) It has a Gaussian distribution shape, that is, it has a single peak and decreases with the increase of the radius; (3) Outside the maximum radius, the removal function has no material removal capability; (4) at the edges and at the central peak, the slope of the function is zero.

Considering the motion relationship between the grinding head and the workpiece, there are three ways: (1) The grinding head has self-rotation but no revolution, which is called the self-rotation type; (2) The grinding head has revolution, but no rotation, which is called the flat-rotation type; (3) The grinding head has both revolution and rotation, which is called planetary rotation type.

There are many moving devices that can realize the above-mentioned movements, and Fig. 4 shows a typical mechanism that can respectively realize the above-mentioned three kinds of movements. As shown in Figure 4, in the form of self-rotating motion, the tool head 13 is driven to rotate by the spindle motor 16 for grinding/polishing; Cutting/polishing movement, the eccentricity adjustment device 18 can adjust the size of the magnitude of the horizontal rotation; in the planetary rotation mode, the tool head 13 is driven by the main shaft 17 to rotate, and the planetary shaft 14 is driven to perform planetary rotation, and the magnitude of the planetary rotation It can be adjusted by the size of the eccentricity.

Fig. 5 is a schematic diagram of the mathematical model of planetary motion. In the figure, O ₁ is the main shaft with a rotation speed of ω ₁ , O ₂ is the planetary shaft with a rotation speed of ω ₂ , e is the eccentricity, the radius of the tool is r ₁ , and point A ( r , θ ) is a processed point (polar coordinate point) on the workpiece. The removal functions under the three motion modes are:

                                  （5） (1) Self-rotating type:

                                  (5)

(2) Flat rotation type:

            (6)

(6)

(3) Planetary rotation type:

， （7）

, (7)

，

，

，

in,

,

,

,

可知，在实际加工过程中，只要知道去除函数、驻留时间、材料去除量中的任意两个就可以求解第三个。在实际加工中，先是用测量仪器测量工件表面的实际面形，将它与要求的面形比较后得到表面面形的误差，即预期的材料去除量

。同时一旦抛光模的运动方式决定后，去除函数R(x，y)也就决定了，问题就转化为求解驻留时间。 Depend on

It can be seen that in the actual machining process, as long as any two of the removal function, dwell time, and material removal amount are known, the third one can be solved. In actual processing, the actual surface shape of the workpiece surface is first measured with a measuring instrument, and compared with the required surface shape, the error of the surface shape is obtained, that is, the expected material removal amount

. At the same time, once the movement mode of the polishing die is determined, the removal function R(x, y) is also determined, and the problem is transformed into solving the dwell time.

The polishing control software among the present invention comprises such function, input the removal function under certain polishing mode, the workpiece surface shape data that measuring instrument measures, and software can automatically calculate the residence time of polishing tool at each point, and can be polished Path planning and control.

Description of drawings

Fig. 1 is a structure and principle frame diagram of the milling and polishing device of the present invention.

Fig. 2 is a mechanical connection diagram of the milling and polishing device of the present invention.

Figure 3 is a composition diagram of the liquid circulation device.

Fig. 4 is a schematic diagram of a planetary motion structure model in the present invention.

Figure 5 is a diagram of a mathematical model of planetary motion.

Labels in the figure: 1—industrial robot, 2—force sensor, 3—flange, 4—working component, that is, milling/polishing module, 5—liquid delivery pipe, 6—liquid delivery pump, 7—temperature control device, 8—stirring device, 9—liquid storage device, 10—liquid return pump, 11—suction cup fixture, 12—workpiece, 13—tool head, 14—planetary shaft, 15—planetary shaft motor, 16—spindle motor, 17—spindle , 18—eccentric distance adjustment device.

Detailed ways

In order to describe the structure and features of the present invention in detail, the description is as follows in conjunction with the accompanying drawings. As shown in Figure 1 is the composition block diagram of milling polishing device of the present invention, and it mainly is made up of 3 parts:

1. Working component 4, namely the milling/polishing module component. This part adopts a modular design scheme, and the milling and polishing functions can be realized on the same machine only by changing the tool head. The working components are connected to the "wrist" of the robot through a flange. The working components perform self-rotation and horizontal swing motion through the planetary motion structure, and perform grinding or polishing actions, and the rotation speed and swing speed and amplitude can be adjusted. The tool head 13 is located below the working component 4, and the tool head 13 moves on the surface of the workpiece 12 with a removal function controlled by a specific algorithm, and the material removal amount at each point on the surface of the workpiece 12 is controlled by the dwell time of the tool head at this point . The working pressure applied by the tool head 13 to the workpiece is monitored and adjusted by the force sensor to ensure the safety of the workpiece and the constant working pressure, so as to ensure the stability of the removal rate and the stable progress of the machining process.

2. Liquid circulation control system. The liquid circulation control system is provided with a delivery pump, a temperature control device, a stirring device, a storage device, and a liquid return pump. The delivery pump is used to deliver the polishing liquid to the working area; the temperature control device is used to detect and control the temperature of the polishing cooling liquid, which is connected to the control module, that is, the temperature sensor transmits the real-time temperature of the liquid to the control module, when the liquid temperature is high Refrigeration is performed when the temperature is set, otherwise it is heated; the stirring device is mainly used to stir the liquid to prevent the deposition of the processing medium and maintain the uniform concentration of the liquid; the return pump is used to suck back the excess liquid in the working area to the liquid storage tank .

3. Robotic system. The robot system adopts commercial robots, which can realize 6-axis linkage (vertical arm rotation, vertical arm swing, cross arm rotation, cross arm swing, wrist rotation, wrist swing). The position and angle of the tool head (milling head or polishing head) in space, the dwell time at each point and the feed movement are precisely controlled by the control module (including control software). Through the driving module of the robot system and the cooperation with the control software, it is more in line with the needs of optical precision processing, that is, the position of the milling head or polishing head in space and the contact area with the workpiece can be precisely controlled through the force sensor and control software , Dwell time at the working point and feed motion mode (oscillating + rotating + spiral or grid type polishing trajectory design). According to different workpieces or requirements, different working components (milling/polishing modules) are used and connected to the robot "wrist" through flanges. The working components carry out self-rotation and horizontal swing motion through the planetary motion structure, and perform grinding or polishing actions, and the speed and swing range can be adjusted.

In the present invention, the removal method of material is carried out in the following manner, which is explained as follows from the angles of milling and polishing respectively:

1. Milling and grinding.

a. For plane and spherical

When processing a plane or a spherical surface, a cylindrical grinding wheel is used, which is based on the principle of the Fancheng method, that is, when a ring with a radius r moves relative to a point, the trajectory envelope of all points on the ring is a spherical surface, and the spherical curvature radius is the distance from any point on the circle to a fixed point. The fixed point is the center of the spherical surface to be processed, and the center of the circle is considered to be at infinity for the planar workpiece. When the radius r of the ring is constant, changing the distance from any point on the ring to a fixed point will change the radius of curvature of the trajectory enveloping the spherical surface accordingly, forming spherical surfaces with different curvature radii.

b. For aspheric and free surfaces

When processing aspheric and free surfaces, cylindrical grinding wheels are used, based on the principle that the diamond grinding wheel contacts the workpiece in point contact, and the trajectory of the point in space is the meridian profile of the symmetrical aspheric surface. At the same time, the processed workpiece rotates around the axis of symmetry, and the obtained surface is the required symmetrical aspheric surface. The diamond grinding wheel is based on the following principle when processing free-form surface workpieces: the diamond grinding wheel contacts the workpiece in a point contact manner, and the workpiece remains stationary. The trajectory of the contact point between the diamond grinding wheel and the workpiece in space is a grating motion. The envelope surface formed by the path is the surface shape of the workpiece to be processed.

When processing other shapes or complex surfaces, it can be carried out according to the working method of ordinary milling machines, and different milling and grinding tools can be replaced according to needs.

2. Polishing.

During polishing, material removal is based on the following principle: According to the formula derived from Preston’s hypothesis, once the feature removal function and dwell time function of the polishing die movement are known, it is only necessary to control the dwell time of the tool at each point during processing. The amount of material removed at this point can be precisely controlled. When processing according to this theory, the appropriate removal function is selected. By analyzing the surface data obtained from the measurement feedback, the residence time of the polishing head at each point is controlled to obtain the required material removal amount at each point, so as to achieve the corrected surface shape. the goal of.

Claims (2)

1. A milling, grinding and polishing device based on an intelligent numerical control platform, characterized in that it is composed of an industrial robot, a control module, a drive module, a man-machine interface, a working component, a polishing coolant circulation control system, and a suction cup fixture; wherein, the polishing The coolant circulation control system includes a storage device, a stirring device, a temperature control device, a delivery pump and a return pump; the control module and the drive module control and drive the spatial movement and spatial positioning of the industrial robot, thereby controlling the working status of the working components; the control module and The drive module also controls the man-machine interface, and at the same time controls the storage device, stirring device, temperature control device, delivery pump and return pump of the polishing liquid cooling liquid circulation control system; the suction cup fixture is used to clamp the workpiece; The working component is installed on the "wrist" of the robot through the flange; the tool head is set under the working component, and the tool head performs grinding or polishing under the control of the working component; the "wrist" between the flange and the robot A force sensor is also installed between the "wrist" to monitor and control the grinding or polishing force of the tool head on the workpiece; The tool head moves on the surface of the processed workpiece with a removal function controlled by a specific algorithm, and the amount of material removed at each point on the surface of the processed workpiece is controlled by the dwell time of the tool head at the point; According to the Preston hypothesis, the material removal function of the tool head at a certain point (x, y) is expressed by the following formula:

(1) in

is the material removal rate at that point,

is the pressure at that point,

is the relative velocity of the workpiece and the tool head at this point,

is the process factor; Amount of material removed at point (x,y) during time t

The mathematical model of is: (2) Substitute formula (1) into formula (2) to get:

(3) The amount of material removal at a point (x, y) is the convolution function of the material removal rate function at that point with respect to time; Assuming that the removal rate remains constant throughout the polishing process, the above formula simplifies to: (4) In the formula,

is the motion feature removal function derived from the Preston assumption;

is the dwell time function; the feature removal function and dwell time function of the polishing motion are known, and the amount of material removal at that point can be precisely controlled by controlling the dwell time of the tool at each point during processing; The removal functions in the three motion modes are: (1) Self-rotating type: (5) (2) Flat rotation type:

(6) (3) Planetary rotation type:

(7) in,

, ,

,

ω ₁ is the rotation speed of the main shaft of the spindle motor that drives the tool head to rotate in the self-rotation mode, ω ₂ is the rotation speed of the planetary shaft of the planetary shaft motor that drives the tool head to rotate in the planetary rotation mode, e is the eccentricity, r ₁ is The radius of the tool head, point A ( r, θ ) is a processed point on the workpiece. 2. The milling and polishing device based on an intelligent numerical control platform according to claim 1, wherein said storage device is a box structure for storing liquid, and a delivery pump, a temperature control device, Stirring device and return pump; the delivery pump transports the liquid from the storage device to the working area through the pipeline; the temperature control device uses a temperature sensor, which is connected with the control module to detect and control the temperature of the liquid. The real-time temperature is transmitted to the control module. When the liquid temperature is higher than the set temperature, it will be cooled, otherwise it will be heated; the stirring device is used to stir the liquid to prevent the deposition of the processing medium and keep the liquid concentration uniform; the return pump is used to make the working area redundant The liquid is sucked back into the liquid storage device.

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