Research on Surface Polishing Technology of Polycrystalline Diamond
Polishing large-area PCD products by conventional mechanical polishing method, the grinding wheel will first contact the convex portion which appears due to stress deformation, resulting in defects such as long polishing time and local thickness thinning. In this regard, the author designed and applied a double rocker swinging fixture to make the polishing surface adaptively contact with the grinding wheel end during the polishing process. This paper mainly describes the characteristics and application effects of this new technology equipment.
I. INTRODUCTION Since its inception in the 1970s, PCD products have been widely used in high-tech fields such as aerospace, defense, energy, automotive, geological drilling and cables with their excellent performance. In particular, the application of large-area PCD products has made the machining capacity and level a big step forward. The processing precision and the surface quality of the processing are continuously improved, and the processing efficiency is increased by several times or even hundreds of times. Large-area PCD products are mostly used to manufacture cutting tools for various materials. In order to improve chip breaking and improve the precision and surface quality of the workpiece, the PCD surface of most PCD products needs to be polished to achieve the mirror surface (surface roughness Ra≦0.05). Mm). Although many materials introduce new technologies such as electrochemical polishing and ultrasonic polishing on PCD, PCD surface mechanical polishing still dominates in industrial mass production applications.
Second, PCD surface polishing parameters selection PCD surface mechanical polishing process is polycrystalline diamond wear and carbonization process, due to the high hardness of polycrystalline diamond, generally with diamond polishing powder (paste) plus cast iron plate or polished with a grinding wheel. Practice has proved that the efficiency of polishing with diamond polishing powder (paste) and cast iron plate is too low, and most of them use grinding wheel polishing (the contact area between the grinding wheel and the polished surface of the workpiece is large and widely used).
PCD surface polishing quality requirements: (1) surface roughness Ra ≦ 0.05 μm; (2) uniform surface gloss, no refractive surface; (3) no unpolished edges; (4) matt uneven ring; 5) No scratches and pollution.
In order to achieve the quality requirements of PCD surface polishing, when grinding mechanically with a grinding wheel, it is necessary to select the grinding wheel width, concentration and particle size, grinding wheel and workpiece rotation speed, polishing pressure and grinding wheel dressing timing.
Firstly, the particle size and concentration of the grinding wheel should be selected properly. The particle size is too coarse to reach the surface roughness requirement of the workpiece; the particle size is too fine, the processing efficiency is low, the abrasive grain keeps sharp for a short time, the friction during polishing is large, and the temperature rises. The width of the grinding wheel should be selected appropriately, too narrow, the service life is short, the dressing frequency is high, the contact surface of the workpiece is polished and the grinding wheel is small, and the polishing efficiency is low; if the width is too wide, the end surface of the grinding wheel is difficult to level, and the linear speed difference between the inner and outer rings of the grinding wheel is large. There are many differences in the internal and external consumption of the grinding wheel. The frictional contact area in the polishing is large, and the heat dissipation condition of the workpiece is deteriorated. The high concentration of diamond in the working layer of the grinding wheel is beneficial to shorten the contact time between the grinding wheel and the surface to be polished, but the cost is high, which will cause the grinding wheel to degranulate too fast. , sometimes causing scratches on the polished surface.
The workpiece is generally rotated at a low speed during the polishing process, which is advantageous for the smooth running of the workpiece. The grinding wheel usually rotates at a high speed to achieve friction between the PCD surface and the surface of the grinding wheel, which generates heat, the rotation speed of the grinding wheel is too fast, and the friction heat is too high, which does not meet the polishing surface quality requirements.
During the polishing process, the surface to be polished must be in contact with the surface of the grinding wheel. Appropriate pressure must be applied. If the pressure is too small, the surface will be shaken, and the polished surface will be corrugated. If the pressure is too large, the grinding wheel will consume quickly, not only the friction temperature will rise, but also the drive. Motor overload.
The timing of dressing surface of the grinding wheel should be properly controlled. The end surface of the grinding wheel is not trimmed for a long time, the grinding wheel is not sharp, the surface of the polished surface is long with the end surface of the grinding wheel, and the processing efficiency is low; the end face of the grinding wheel is repaired too frequently, and the grinding wheel is consumed quickly. The unevenness of the end surface of the grinding wheel and the non-smooth transition will make the surface to be polished dull and sometimes scratched.
Third, the traditional polishing method and equipment problems The traditional polishing equipment structure is the grinding wheel high-speed rotation, the fixed polishing fixture holds the workpiece at low speed rotation, the polished surface is in contact with the end surface of the grinding wheel, and a certain contact pressure is applied, the rotation center of the workpiece The contact line with the grinding wheel is fixed, and the PCD surface is polished by friction, heat and carbonization.
In the past, PCD articles were large in thickness and the area of ​​the polished surface was small (less than or close to the end face width of the grinding wheel), and polishing with a conventional polishing apparatus was suitable. With the development of technology, the appearance of large-area PCD products has made the surface to be polished more than double the width of the end face grinding wheel, and the thickness of the workpiece is much thinner than in the past. When the polishing surface area of ​​the PCD product is more than 26cm2 and the thickness is not more than 2mm, the thin film Due to the stress deformation, the flatness of the surface to be polished is deteriorated, and the polishing difficulty is increased. Processing large area PCD sheets with conventional polishing equipment has the following problems:
(1) The rotation center of the fixture of the conventional polishing apparatus (and the workpiece to be clamped) has no relative movement with the end surface of the grinding wheel. When the surface to be polished is in contact with the grinding wheel, the distribution of the point (or surface) of the initial contact on the entire surface to be polished It is decisive because the polishing process will then spread around these points (or faces). If the initial contact points (or faces) are small (referred to as poor fit) and are locally concentrated, then only these points will be Or the face is removed, and other points (or faces) can be in contact with the end face of the grinding wheel, which makes the surface polishing become "de-polishing". Because of the poor cutting ability of the grinding wheel used for hard diamond and polishing, the contact point (or surface) ) The expansion to the surroundings is rather slow, resulting in an excessive polishing time and a decrease in processing efficiency.
(2) Since the contact center between the center of rotation of the workpiece and the end face of the grinding wheel is fixed, even if the surface of the polished surface is in contact with the grinding wheel (completely fitted), when the width (length or diameter) of the polished surface of the workpiece is larger than the width of the grinding wheel, the contact is everywhere. The probability of contact outside the workpiece is significantly lower than that of the middle part, so that the polished surface is prone to different refractive rings with different brightness and darkness, which cannot meet the quality requirements.
(3) Due to the fact that the middle part of the polished surface does not leave the end face of the grinding wheel during the polishing process, the friction heat in the middle is larger than the surrounding area, and the heat dissipation condition is poor. For large-area and thin-thick PCD products, local deformation causes the deformation of the workpiece to be intensified.
(4) The stress deformation causes the planar shape of the surface to be polished to be irregular, accompanied by distortion. Only by trimming the end face of the grinding wheel or the surface of the polished surface and the end face of the grinding wheel, the end face of the grinding wheel is as close as possible to the surface to be polished (the contact surface is more contact points and evenly distributed). However, the stress deformation is random, and the surface distortion causes the surface condition of each workpiece to be different. When the end surface of the grinding wheel is trimmed or worn to match the surface of the PCD of one workpiece, and the other workpiece is replaced, it does not match, and must be trimmed again by the grinding wheel or Wear and reach a new match, which not only has low processing efficiency, but also increases the labor intensity of the operator, which is not suitable for mass production.
(5) Due to the difference in surface shape of each PCD product, the possibility that the same grinding wheel end face is trimmed to coincide with the PCD surface of the two workpieces is small. Even if it can be matched at the same time, the friction temperature rise caused by one grinding wheel polishing two large-area PCD products at the same time, the middle part of the workpiece can not be disengaged from the grinding wheel (the heat dissipation condition is poor), and the traditional polishing equipment (using the same grinding wheel) simultaneously Polishing two large-area PCD products not only requires a large difference in processing time for each sheet, but also excessively high temperatures, which tend to burn the polished surface.
IV. Determination of the improvement scheme According to the above analysis, it is important to improve the polishing efficiency during the polishing process to improve the degree of contact between the polished surface and the end surface of the grinding wheel. During the polishing process, the self-rotating center of the surface to be polished is radially moved along the grinding wheel on the end face of the grinding wheel, and the adaptive contact function is used to improve the degree of contact fit (especially for the convexly deformed polished surface). When the center of rotation of the workpiece leaves the contact line on the end face of the grinding wheel, a part of the contact point (face) on the surface to be polished and the end face of the grinding wheel will be disengaged (microscopically, the end face of the grinding wheel is displaced in the radial direction) , is not a flat surface), the original stable contact state is broken, and with the cooperation of the adaptive contact function, some points (faces) that are not in contact with the end face of the grinding wheel are in contact with the end face of the grinding wheel at this time, thereby adding new contact points ( Face) improves the mutual contact and anastomosis, thus shortening the polishing time.
The displacement of the workpiece rotation center on the end face of the grinding wheel also has the following advantages:
(1) The polishing process is a mutual wear process between the grinding wheel and the surface to be polished. When the workpiece is displaced, the high end point of the grinding wheel is flattened, which not only eliminates the ring-shaped refraction ring that may appear on the polished surface, but also reduces the difficulty of dressing the flat end of the grinding wheel. .
(2) The contact between the middle and the edge of the polished surface is balanced with the end face of the grinding wheel to make the workpiece uniform throughout the workpiece; in addition, most of the polished surface is removed from the end face of the grinding wheel to improve the heat dissipation condition of the workpiece and reduce the workpiece. Thermal deformation caused by the polishing process.
(3) Shorten the time difference required for simultaneous polishing of workpieces with different surface deformation states. Since the polished surface is adaptively matched with the end face of the grinding wheel, the method of dressing the end face of the grinding wheel is not required to adapt to the surface to be polished, and the heat dissipation condition of the workpiece is improved, so that the same polishing device (using the same grinding wheel) simultaneously polishes two large-area PCDs. The product is realized.
There are various methods for realizing the relative displacement of the rotation center of the polished surface and the contact line of the grinding wheel end surface: one is to perform eccentric oscillation while the main shaft (grinding wheel) rotates at a high speed; the other is to radially displace along the grinding wheel at the center of rotation of the workpiece or In a certain angle (the center pressure point does not open the end face of the grinding wheel), according to the data, the polishing equipment produced abroad uses the grinding wheel to rotate at a high speed while performing eccentric oscillation.
Using the principle of double rocker oscillating mechanism, we designed the rotating, pressing, oscillating and contact adaptive clamps of the composite piece to make the workpiece oscillate within a certain angle (the central pressure point does not leave the end face of the grinding wheel) to realize the rotation center of the polished surface. Displacement on the end face of the grinding wheel, its advantages:
(1) The cost is low, the mechanical structure is relatively simple, and the basic structure of the conventional polishing equipment can be maintained (only the clamp portion is changed).
(2) Due to the harsh polishing environment (dust), the traditional screw and guide transmission mechanism are adopted, the cost is high, the dust easily enters the moving part, and the service life is reduced (protection is difficult); the cam or pneumatic and hydraulic mechanism are adopted. Complex, there are many peripheral accessories; and the four-bar linkage mechanism is not only simple in structure, strong in motion reliability, but also easy to protect and adaptable to the environment, suitable for application on polishing equipment.
(3) Selecting the double rocker swinging mechanism in the four-bar linkage mechanism, it is possible to simultaneously swing the workpiece from the rotation and the center of rotation at a certain angle by using one driving motor.
(4) Many parts of the original fixed structure fixture can be utilized without increasing the complexity of the operation.
V. Contrast experiment and analysis We used a new structure (with a double rocker oscillating polishing fixture) to polish the machine with a conventional (fixed polishing fixture) polishing machine for processing comparison experiments.
Firstly, the workpiece with the polished surface and the shape of the end face of the grinding wheel is selected to test. The new grinding wheel is used. On the traditional polishing machine, the new grinding wheel is basically smooth with the polished surface, because the end surface of the grinding wheel is not smooth, the polishing effect is poor (the polished surface is not bright and There are scratches), and on the new structure of the polishing machine, the surface quality after polishing meets the requirements, which proves that the polished surface has a dressing effect on the end face of the grinding wheel.
Then we choose the workpiece that is convex in the polished surface to be tested. On the traditional polishing machine, after processing for a period of time, the boundary between the polished surface and the untouched surface of the polished surface is clear. If the end surface of the grinding wheel is not trimmed, polishing is continued, not only for a long time. Moreover, there is a possibility that the thickness of the central portion of the PCD layer is reduced. On the new structure of the polishing machine, the same time is observed, the boundary between the surface polishing and the non-contact is blurred, and the edge has contact marks. After polishing, the flatness of the polished surface is basically the same as that before polishing. We chose the test of the concave part in the polished surface, the situation is basically the same, except that the surface polishing is extended from the edge to the center.
We carried out the comparison of the processing efficiency, and took 10 sets of equipment to measure the processing time respectively. The results show that the average processing efficiency of the new structure polishing machine is 20% higher than that of the polished surface even if the end face of the grinding wheel is basically matched with the polished surface.
We machined two workpieces simultaneously on the polishing machine equipped with two fixed polishing fixtures (the same amount of surface deformation), and found that the workpiece temperature rises quickly and high. If the grinding wheel is not sharp, the machining must be interrupted frequently (otherwise the workpiece surface burns) ), when one of the polished surfaces is completely in contact with the end face of the grinding wheel, the other piece has only 50% contact marks. Two workpieces are processed simultaneously on a polishing machine equipped with two double rocker oscillating polishing fixtures. The grinding wheel cycle is the same as that of a conventional polishing machine. The results show that not only the polishing surface quality is required, but also the processing time per piece. The polishing is only increased by about 10%, and the difference in polishing time between the two workpieces is small, which proves that the polishing machine with two double rocker swing polishing fixtures can increase the processing efficiency by 80% compared with the conventional polishing machine.
VI. Conclusions (1) If the polished surface does not match the end surface of the grinding wheel during polishing, the polishing is performed with the improved polishing equipment. The processing efficiency is significantly improved (at least 20%) compared with the conventional polishing equipment, and the heat dissipation condition of the workpiece is obviously improved.
(2) The polished surface of the workpiece machined by the improved polishing apparatus does not have a ring-shaped refraction aura, and the surface quality is remarkably improved.
(3) For the improved polishing equipment, the end face of the grinding wheel is less difficult than the conventional polishing equipment. The end surface of the grinding wheel of the conventional polishing equipment not only needs to be smoothed, but also fits as much as possible with the surface to be polished. In the new structure polishing equipment, the dressing end surface of the grinding wheel only needs to be in the stage of matching the surface to be polished and the end surface of the grinding wheel, so that the grinding grain on the grinding wheel can be sharp.
(4) The improved polishing equipment realizes one piece of equipment to simultaneously polish two large-area polycrystalline diamond products, and improves the utilization rate of the equipment by 80%.
I. INTRODUCTION Since its inception in the 1970s, PCD products have been widely used in high-tech fields such as aerospace, defense, energy, automotive, geological drilling and cables with their excellent performance. In particular, the application of large-area PCD products has made the machining capacity and level a big step forward. The processing precision and the surface quality of the processing are continuously improved, and the processing efficiency is increased by several times or even hundreds of times. Large-area PCD products are mostly used to manufacture cutting tools for various materials. In order to improve chip breaking and improve the precision and surface quality of the workpiece, the PCD surface of most PCD products needs to be polished to achieve the mirror surface (surface roughness Ra≦0.05). Mm). Although many materials introduce new technologies such as electrochemical polishing and ultrasonic polishing on PCD, PCD surface mechanical polishing still dominates in industrial mass production applications.
Second, PCD surface polishing parameters selection PCD surface mechanical polishing process is polycrystalline diamond wear and carbonization process, due to the high hardness of polycrystalline diamond, generally with diamond polishing powder (paste) plus cast iron plate or polished with a grinding wheel. Practice has proved that the efficiency of polishing with diamond polishing powder (paste) and cast iron plate is too low, and most of them use grinding wheel polishing (the contact area between the grinding wheel and the polished surface of the workpiece is large and widely used).
PCD surface polishing quality requirements: (1) surface roughness Ra ≦ 0.05 μm; (2) uniform surface gloss, no refractive surface; (3) no unpolished edges; (4) matt uneven ring; 5) No scratches and pollution.
In order to achieve the quality requirements of PCD surface polishing, when grinding mechanically with a grinding wheel, it is necessary to select the grinding wheel width, concentration and particle size, grinding wheel and workpiece rotation speed, polishing pressure and grinding wheel dressing timing.
Firstly, the particle size and concentration of the grinding wheel should be selected properly. The particle size is too coarse to reach the surface roughness requirement of the workpiece; the particle size is too fine, the processing efficiency is low, the abrasive grain keeps sharp for a short time, the friction during polishing is large, and the temperature rises. The width of the grinding wheel should be selected appropriately, too narrow, the service life is short, the dressing frequency is high, the contact surface of the workpiece is polished and the grinding wheel is small, and the polishing efficiency is low; if the width is too wide, the end surface of the grinding wheel is difficult to level, and the linear speed difference between the inner and outer rings of the grinding wheel is large. There are many differences in the internal and external consumption of the grinding wheel. The frictional contact area in the polishing is large, and the heat dissipation condition of the workpiece is deteriorated. The high concentration of diamond in the working layer of the grinding wheel is beneficial to shorten the contact time between the grinding wheel and the surface to be polished, but the cost is high, which will cause the grinding wheel to degranulate too fast. , sometimes causing scratches on the polished surface.
The workpiece is generally rotated at a low speed during the polishing process, which is advantageous for the smooth running of the workpiece. The grinding wheel usually rotates at a high speed to achieve friction between the PCD surface and the surface of the grinding wheel, which generates heat, the rotation speed of the grinding wheel is too fast, and the friction heat is too high, which does not meet the polishing surface quality requirements.
During the polishing process, the surface to be polished must be in contact with the surface of the grinding wheel. Appropriate pressure must be applied. If the pressure is too small, the surface will be shaken, and the polished surface will be corrugated. If the pressure is too large, the grinding wheel will consume quickly, not only the friction temperature will rise, but also the drive. Motor overload.
The timing of dressing surface of the grinding wheel should be properly controlled. The end surface of the grinding wheel is not trimmed for a long time, the grinding wheel is not sharp, the surface of the polished surface is long with the end surface of the grinding wheel, and the processing efficiency is low; the end face of the grinding wheel is repaired too frequently, and the grinding wheel is consumed quickly. The unevenness of the end surface of the grinding wheel and the non-smooth transition will make the surface to be polished dull and sometimes scratched.
Third, the traditional polishing method and equipment problems The traditional polishing equipment structure is the grinding wheel high-speed rotation, the fixed polishing fixture holds the workpiece at low speed rotation, the polished surface is in contact with the end surface of the grinding wheel, and a certain contact pressure is applied, the rotation center of the workpiece The contact line with the grinding wheel is fixed, and the PCD surface is polished by friction, heat and carbonization.
In the past, PCD articles were large in thickness and the area of ​​the polished surface was small (less than or close to the end face width of the grinding wheel), and polishing with a conventional polishing apparatus was suitable. With the development of technology, the appearance of large-area PCD products has made the surface to be polished more than double the width of the end face grinding wheel, and the thickness of the workpiece is much thinner than in the past. When the polishing surface area of ​​the PCD product is more than 26cm2 and the thickness is not more than 2mm, the thin film Due to the stress deformation, the flatness of the surface to be polished is deteriorated, and the polishing difficulty is increased. Processing large area PCD sheets with conventional polishing equipment has the following problems:
(1) The rotation center of the fixture of the conventional polishing apparatus (and the workpiece to be clamped) has no relative movement with the end surface of the grinding wheel. When the surface to be polished is in contact with the grinding wheel, the distribution of the point (or surface) of the initial contact on the entire surface to be polished It is decisive because the polishing process will then spread around these points (or faces). If the initial contact points (or faces) are small (referred to as poor fit) and are locally concentrated, then only these points will be Or the face is removed, and other points (or faces) can be in contact with the end face of the grinding wheel, which makes the surface polishing become "de-polishing". Because of the poor cutting ability of the grinding wheel used for hard diamond and polishing, the contact point (or surface) ) The expansion to the surroundings is rather slow, resulting in an excessive polishing time and a decrease in processing efficiency.
(2) Since the contact center between the center of rotation of the workpiece and the end face of the grinding wheel is fixed, even if the surface of the polished surface is in contact with the grinding wheel (completely fitted), when the width (length or diameter) of the polished surface of the workpiece is larger than the width of the grinding wheel, the contact is everywhere. The probability of contact outside the workpiece is significantly lower than that of the middle part, so that the polished surface is prone to different refractive rings with different brightness and darkness, which cannot meet the quality requirements.
(3) Due to the fact that the middle part of the polished surface does not leave the end face of the grinding wheel during the polishing process, the friction heat in the middle is larger than the surrounding area, and the heat dissipation condition is poor. For large-area and thin-thick PCD products, local deformation causes the deformation of the workpiece to be intensified.
(4) The stress deformation causes the planar shape of the surface to be polished to be irregular, accompanied by distortion. Only by trimming the end face of the grinding wheel or the surface of the polished surface and the end face of the grinding wheel, the end face of the grinding wheel is as close as possible to the surface to be polished (the contact surface is more contact points and evenly distributed). However, the stress deformation is random, and the surface distortion causes the surface condition of each workpiece to be different. When the end surface of the grinding wheel is trimmed or worn to match the surface of the PCD of one workpiece, and the other workpiece is replaced, it does not match, and must be trimmed again by the grinding wheel or Wear and reach a new match, which not only has low processing efficiency, but also increases the labor intensity of the operator, which is not suitable for mass production.
(5) Due to the difference in surface shape of each PCD product, the possibility that the same grinding wheel end face is trimmed to coincide with the PCD surface of the two workpieces is small. Even if it can be matched at the same time, the friction temperature rise caused by one grinding wheel polishing two large-area PCD products at the same time, the middle part of the workpiece can not be disengaged from the grinding wheel (the heat dissipation condition is poor), and the traditional polishing equipment (using the same grinding wheel) simultaneously Polishing two large-area PCD products not only requires a large difference in processing time for each sheet, but also excessively high temperatures, which tend to burn the polished surface.
IV. Determination of the improvement scheme According to the above analysis, it is important to improve the polishing efficiency during the polishing process to improve the degree of contact between the polished surface and the end surface of the grinding wheel. During the polishing process, the self-rotating center of the surface to be polished is radially moved along the grinding wheel on the end face of the grinding wheel, and the adaptive contact function is used to improve the degree of contact fit (especially for the convexly deformed polished surface). When the center of rotation of the workpiece leaves the contact line on the end face of the grinding wheel, a part of the contact point (face) on the surface to be polished and the end face of the grinding wheel will be disengaged (microscopically, the end face of the grinding wheel is displaced in the radial direction) , is not a flat surface), the original stable contact state is broken, and with the cooperation of the adaptive contact function, some points (faces) that are not in contact with the end face of the grinding wheel are in contact with the end face of the grinding wheel at this time, thereby adding new contact points ( Face) improves the mutual contact and anastomosis, thus shortening the polishing time.
The displacement of the workpiece rotation center on the end face of the grinding wheel also has the following advantages:
(1) The polishing process is a mutual wear process between the grinding wheel and the surface to be polished. When the workpiece is displaced, the high end point of the grinding wheel is flattened, which not only eliminates the ring-shaped refraction ring that may appear on the polished surface, but also reduces the difficulty of dressing the flat end of the grinding wheel. .
(2) The contact between the middle and the edge of the polished surface is balanced with the end face of the grinding wheel to make the workpiece uniform throughout the workpiece; in addition, most of the polished surface is removed from the end face of the grinding wheel to improve the heat dissipation condition of the workpiece and reduce the workpiece. Thermal deformation caused by the polishing process.
(3) Shorten the time difference required for simultaneous polishing of workpieces with different surface deformation states. Since the polished surface is adaptively matched with the end face of the grinding wheel, the method of dressing the end face of the grinding wheel is not required to adapt to the surface to be polished, and the heat dissipation condition of the workpiece is improved, so that the same polishing device (using the same grinding wheel) simultaneously polishes two large-area PCDs. The product is realized.
There are various methods for realizing the relative displacement of the rotation center of the polished surface and the contact line of the grinding wheel end surface: one is to perform eccentric oscillation while the main shaft (grinding wheel) rotates at a high speed; the other is to radially displace along the grinding wheel at the center of rotation of the workpiece or In a certain angle (the center pressure point does not open the end face of the grinding wheel), according to the data, the polishing equipment produced abroad uses the grinding wheel to rotate at a high speed while performing eccentric oscillation.
Using the principle of double rocker oscillating mechanism, we designed the rotating, pressing, oscillating and contact adaptive clamps of the composite piece to make the workpiece oscillate within a certain angle (the central pressure point does not leave the end face of the grinding wheel) to realize the rotation center of the polished surface. Displacement on the end face of the grinding wheel, its advantages:
(1) The cost is low, the mechanical structure is relatively simple, and the basic structure of the conventional polishing equipment can be maintained (only the clamp portion is changed).
(2) Due to the harsh polishing environment (dust), the traditional screw and guide transmission mechanism are adopted, the cost is high, the dust easily enters the moving part, and the service life is reduced (protection is difficult); the cam or pneumatic and hydraulic mechanism are adopted. Complex, there are many peripheral accessories; and the four-bar linkage mechanism is not only simple in structure, strong in motion reliability, but also easy to protect and adaptable to the environment, suitable for application on polishing equipment.
(3) Selecting the double rocker swinging mechanism in the four-bar linkage mechanism, it is possible to simultaneously swing the workpiece from the rotation and the center of rotation at a certain angle by using one driving motor.
(4) Many parts of the original fixed structure fixture can be utilized without increasing the complexity of the operation.
V. Contrast experiment and analysis We used a new structure (with a double rocker oscillating polishing fixture) to polish the machine with a conventional (fixed polishing fixture) polishing machine for processing comparison experiments.
Firstly, the workpiece with the polished surface and the shape of the end face of the grinding wheel is selected to test. The new grinding wheel is used. On the traditional polishing machine, the new grinding wheel is basically smooth with the polished surface, because the end surface of the grinding wheel is not smooth, the polishing effect is poor (the polished surface is not bright and There are scratches), and on the new structure of the polishing machine, the surface quality after polishing meets the requirements, which proves that the polished surface has a dressing effect on the end face of the grinding wheel.
Then we choose the workpiece that is convex in the polished surface to be tested. On the traditional polishing machine, after processing for a period of time, the boundary between the polished surface and the untouched surface of the polished surface is clear. If the end surface of the grinding wheel is not trimmed, polishing is continued, not only for a long time. Moreover, there is a possibility that the thickness of the central portion of the PCD layer is reduced. On the new structure of the polishing machine, the same time is observed, the boundary between the surface polishing and the non-contact is blurred, and the edge has contact marks. After polishing, the flatness of the polished surface is basically the same as that before polishing. We chose the test of the concave part in the polished surface, the situation is basically the same, except that the surface polishing is extended from the edge to the center.
We carried out the comparison of the processing efficiency, and took 10 sets of equipment to measure the processing time respectively. The results show that the average processing efficiency of the new structure polishing machine is 20% higher than that of the polished surface even if the end face of the grinding wheel is basically matched with the polished surface.
We machined two workpieces simultaneously on the polishing machine equipped with two fixed polishing fixtures (the same amount of surface deformation), and found that the workpiece temperature rises quickly and high. If the grinding wheel is not sharp, the machining must be interrupted frequently (otherwise the workpiece surface burns) ), when one of the polished surfaces is completely in contact with the end face of the grinding wheel, the other piece has only 50% contact marks. Two workpieces are processed simultaneously on a polishing machine equipped with two double rocker oscillating polishing fixtures. The grinding wheel cycle is the same as that of a conventional polishing machine. The results show that not only the polishing surface quality is required, but also the processing time per piece. The polishing is only increased by about 10%, and the difference in polishing time between the two workpieces is small, which proves that the polishing machine with two double rocker swing polishing fixtures can increase the processing efficiency by 80% compared with the conventional polishing machine.
VI. Conclusions (1) If the polished surface does not match the end surface of the grinding wheel during polishing, the polishing is performed with the improved polishing equipment. The processing efficiency is significantly improved (at least 20%) compared with the conventional polishing equipment, and the heat dissipation condition of the workpiece is obviously improved.
(2) The polished surface of the workpiece machined by the improved polishing apparatus does not have a ring-shaped refraction aura, and the surface quality is remarkably improved.
(3) For the improved polishing equipment, the end face of the grinding wheel is less difficult than the conventional polishing equipment. The end surface of the grinding wheel of the conventional polishing equipment not only needs to be smoothed, but also fits as much as possible with the surface to be polished. In the new structure polishing equipment, the dressing end surface of the grinding wheel only needs to be in the stage of matching the surface to be polished and the end surface of the grinding wheel, so that the grinding grain on the grinding wheel can be sharp.
(4) The improved polishing equipment realizes one piece of equipment to simultaneously polish two large-area polycrystalline diamond products, and improves the utilization rate of the equipment by 80%.
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