JP6344730B2 - EEM processing method - Google Patents

Description

  The present invention relates to an EEM processing method, and more particularly, to an EEM processing method of a nozzle type processing head type that forms a shape with high precision using a plurality of spot processing marks having different profiles.

  Conventionally, fine particles such as metal oxides are supplied to the surface of the workpiece in an environment where water molecules are present, and the fine particles bonded to the surface atoms are separated by an external force such as a water flow by a chemical reaction between solids. A processing method for removing atoms, that is, EEM (Elastic Emission Machining) is known. The EEM has an automatic flattening action in which convex portions on the surface are removed preferentially by flowing a slurry (working fluid) in which fine particles are dispersed in water along the surface of the workpiece, and the spatial wavelength is reduced. It has a feature that it can be flattened on the atomic order by removing short-period irregularities (roughness). In addition, EEM has the characteristics that crystallographically excellent surface equivalent to chemical etching can be obtained and processing controllability can be obtained.

  In EEM, it is necessary to create a high-speed velocity field of the machining fluid along the workpiece surface in order to remove the fine particles bound to the workpiece surface, and the flow velocity near the surface has a great influence on the machining speed. For this reason, it is required to achieve a high flow rate. As a method for creating such a working fluid velocity field, a nozzle type machining head system described in Patent Document 1 and a rotating sphere type machining head system described in Patent Document 2 and the like have been put into practical use. We also propose a numerically controlled EEM machining method that creates an arbitrary curved surface by scanning these machining heads relative to the surface of the workpiece and controlling the amount of local removal by controlling the staying time. The shape accuracy of PV value is 1nm or less, such as ellipsoidal mirrors for X-rays generated in large synchrotron radiation facilities such as Spring-8 and advanced optical elements used in extreme ultraviolet lithography (EUVL). Used to make high-quality mirrors.

  Nozzle-type machining head type EEM has a nozzle-type machining head placed at a position that is a predetermined standoff distance (gap) from the workpiece surface, and the workpiece surface is machined by the jets discharged from the nozzle. It creates a high-speed velocity field of liquid and enables numerically controlled machining of minute areas. As for the nozzle used here, the cross-sectional shape of an opening part is circular (circular hole) and a rectangle (slit hole), and the internal flow path is linear toward the opening part. The feature of such a direct current type nozzle is that the spot machining trace is loose with respect to the change of the gap, that is, the spot machining trace is stably obtained, which is advantageous in increasing the machining accuracy. Then, by scanning the direct current type nozzle or the workpiece with numerical control with respect to the other, it is possible to correct the long-period shape of the spatial wavelength. However, the opening diameter of a direct current nozzle that has been stable for a long time so far is about 150 μm at the minimum, thereby realizing a spatial resolution of 500 μm.

  A rotating sphere machining head type EEM has an elastic rotating body and a workpiece placed in a machining tank filled with a machining fluid, and presses the elastic rotating body against the workpiece surface with a constant load. While maintaining a gap of about 1 μm between the elastic rotator and the workpiece surface by balancing the fluid dynamic pressure and the load of the working fluid that is rotated and wound between the elastic rotator and the workpiece surface, Processing is performed by generating a locally high flow of cutting fluid across the gap. In this case, the size of the spot machining mark is in mm, and the spatial resolution is not high.

  Usually, the region with the lowest spatial frequency is generally the shape (Low spatial frequency roughness: LSFR), the middle region is the swell (Mid spatial frequency roughness: MSFR), and the region with the highest spatial frequency is the surface roughness (High spatial frequency roughness: HSFR). be called. Here, the long period region of the spatial wavelength corresponds to the LSFR, the medium period region corresponds to the MSFR, and the short period region corresponds to the HSFR, but there is no clear definition for the range of the region. Since the present invention is supposed to be applied to finishing processing of mirrors and the like that can be used in an X-ray optical system, the irregularities in the short period region correspond to the roughness that can be observed with a scanning tunneling microscope (STM). The shape accuracy is on the order of 0.1 nm in terms of PV value. In the present invention, it is assumed that the medium wavelength region of the spatial wavelength is about 50 to 1000 μm.

  In the processing of a planar shape or a curved surface shape close to a plane, the surface unevenness of almost all spatial wavelengths could be removed by using the above-described nozzle type processing head method and rotating sphere processing head method EEM together. However, if the curved surface has a large curvature or a shape that changes sharply, the spatial resolution region that can be removed by the EEM of the rotating sphere type machining head method becomes small, and the EEM of the conventional nozzle type machining head type has a medium spatial wavelength region. Since there is a weakness in the processing of, it can not be finished in an ideal shape. In general, with this type of processing method that removes unevenness by continuously creating spot processing marks of this type and creates the target shape, unevenness that is about half the size of the spot processing marks can be removed, but a smaller medium period It is difficult to completely remove the unevenness. Similarly, even when the target shape changes abruptly in the order of the size of the spot processing mark, it is difficult to process with the conventional DC type nozzle.

Japanese Patent No. 3860352 Japanese Patent Publication No. 07-016870

  Therefore, in view of the above-mentioned situation, the present invention is to solve the EEM processing method of the nozzle type processing head method, and a plurality of profiles without fixing the spot processing trace profile as in the prior art. An object of the present invention is to provide an EEM processing method capable of creating a target shape with high precision by actively using spot processing marks and superimposing them.

  The present invention provides an EEM processing method having the following configuration in order to solve the aforementioned problems.

(1)
A predetermined gap is provided between the tip of the nozzle and the workpiece, and the workpiece is placed in the water. A processing liquid in which fine particles are dispersed in water is discharged from the nozzle opening at a predetermined back pressure, and is applied to the surface of the workpiece. A high shear flow is generated along the surface, the fine particles bonded to the surface atoms by the solid-state chemical reaction are separated by the flow of water , and the nozzle is moved against the workpiece surface using the processing principle of removing the surface atoms together with the fine particles . In the EEM processing method that controls the local removal amount by scanning relatively and controlling the stay time, using one nozzle, changing at least one of the gap and the back pressure in a stationary state , Obtain spot processing trace profile data under each processing condition, control the spot processing trace profile by controlling the gap and back pressure, EEM processing method characterized by comprising by processing by Kasaneawashi a plurality of spots working mark to.

(2)
A predetermined gap is provided between the tip of the nozzle and the workpiece, and the workpiece is placed in the water. A processing liquid in which fine particles are dispersed in water is discharged from the nozzle opening at a predetermined back pressure, and is applied to the surface of the workpiece. A high shear flow is generated along the surface, the fine particles bonded to the surface atoms by the solid-state chemical reaction are separated by the flow of water, and the nozzle is moved against the workpiece surface using the processing principle of removing the surface atoms together with the fine particles. In the EEM processing method of controlling by scanning relatively and controlling the amount of local removal by controlling the staying time, a plurality of types of nozzles are used, and the processing conditions of the gap and the back pressure are used for each nozzle. By obtaining spot processing trace profile data and changing the nozzle, the spot processing trace profile is changed, and multiple spot processing traces with different profiles are overlapped and processed. EEM processing wherein the.

  In the EEM processing method of the present invention as described above, a predetermined gap is provided between the tip of the nozzle and the workpiece, and the processing liquid in which fine particles are dispersed in water is placed at a predetermined back pressure with a predetermined back pressure. An EEM processing method that discharges from the opening, generates a high shear flow along the surface of the workpiece, separates the fine particles bonded to the surface atoms by a chemical reaction between solids, and removes the surface atoms together with the fine particles. In the above, using a plurality of spot machining traces having different profiles, the nozzle is scanned relative to the surface of the workpiece, and the removal time is controlled by controlling the staying time. By adding the spot machining traces of multiple profiles, various shapes can be created, and the application of the machining object can be expanded. In particular, the present invention can be applied to ultra-precision processing of complex-shaped optical elements.

  That is, the present invention can create a removal amount distribution that matches a target shape by superimposing spot processing traces of a plurality of profiles, and can thereby process steep shapes and complex shapes. Here, the steep shape is a shape such as a spheroid having a width of 1 mm, a length of 50 mm, and a depth of about 10 μm. It is possible to find the optimum shape processing conditions when using multiple spot processing traces by putting the shapes of multiple spot processing traces in a computer. is expected.

It is the schematic of the EEM processing apparatus of a nozzle type processing head system. (A) is the fragmentary sectional view of the conventional direct current type nozzle for comparison, (b) is the fragmentary sectional view of the current collection type nozzle used for this invention. The simulation result of a straight flow path and a focusing flow path is shown, (a) is the velocity distribution on the XZ plane including the center line in the case of the straight flow path, and (b) is the XZ plane including the center line in the case of the focusing flow path. Upper velocity distribution, (c) velocity distribution on the surface of 1 μm from the workpiece surface in the case of the straight flow path, and (d) velocity distribution on the surface of 1 μm from the workpiece surface in the case of the focusing flow path. (E) shows the cross-sectional shape of the velocity distribution in the case of the straight flow path, and (f) shows the cross-sectional shape of the velocity distribution in the case of the focusing flow path. The removal distribution of the static spot profile when the standoff distance (gap) is 1 mm is shown, (a) is a direct current type nozzle, and (b) is a current collecting type nozzle. The removal distribution of the profile of a static spot machining trace at a standoff distance (gap) of 0.4 mm to 1.8 mm is shown, (a) is a case of a direct current type nozzle, and (b) is a case of a current collecting type nozzle. The cross-sectional profile of the spot processing trace in the stand-off distance (gap) of 0.4 mm to 1.8 mm is shown, (a) is a direct current type nozzle, (b) is a current collecting type nozzle. The longitudinal cross-sectional profile of the spot processing trace in the stand-off distance (gap) of 0.4 mm to 1.8 mm is shown, (a) is a direct current type nozzle, (b) is a case of a current collecting type nozzle. The relationship between the removal amount and the spot size with respect to the stand-off distance (gap) is shown, where (a) is a direct current type nozzle and (b) is a current collecting type nozzle. The STM image and surface roughness of the quartz surface are shown, (a) shows the surface before processing, and (b) shows the surface after processing using a collecting nozzle. It is a disassembled perspective view which shows the Example of a current collecting type nozzle. It is sectional drawing which similarly shows the Example of a current collecting type nozzle. It is a graph which shows the relationship between a back pressure and a flow volume. It is a graph which shows the relationship between the half value width of a gap and a spot processing mark using back pressure as a parameter. It is a graph which shows the relationship between a gap and the processing rate of a spot processing trace using back pressure as a parameter.

  Next, the present invention will be described in more detail based on the embodiments shown in the accompanying drawings. FIG. 1 shows a schematic view of a nozzle type machining head type EEM machining apparatus, wherein reference numeral 1 denotes a nozzle head, 2 denotes a workpiece, 3 denotes a water tank, and 4 denotes an NC stage.

  In this processing apparatus, the nozzle head 1 and the workpiece 2 are arranged inside the water tank 3 with a predetermined gap so that the nozzle head 1 can be relatively scanned along the surface of the workpiece 2. I have to. For example, the nozzle head 1 is fixed, the workpiece 2 is held on the NC stage 4, the NC stage 4 is driven to set the gap, and the surface of the workpiece 2 is placed on the nozzle head 1. It is possible to move against. Then, the slurry (processing liquid) in which water and fine particles are dispersed is supplied from the diaphragm pump 5 to the nozzle head 1 and discharged into the water tank 3, and the processing liquid accumulated in the water tank 3 is sucked by the diaphragm pump 5. Circulating. At this time, the pressure (back pressure) of the machining fluid supplied to the nozzle head 1 is set to a set value by the compressed air supplied from the air compressor 7 through the regulator 8 to the damper 6 connected to the outlet pipe of the diaphragm pump 5. The back pressure is monitored with a pressure gauge 9.

  In this embodiment, the NC stage 4 includes an XY stage for controlling the workpiece 2 on a horizontal plane in the water tank 3 and a Z stage for adjusting a gap between the nozzle head 1 and the workpiece 2. It consists of First, in a stationary state, a jet of the machining liquid discharged from the nozzle head 1 is sprayed on the surface of the workpiece 2 to stably generate a high shear flow along the surface, and a chemical reaction between solids. The fine particles bonded to the surface atoms are separated by the flow of water, and the profile data of the spot machining marks formed by removing the surface atoms together with the fine particles is acquired. Then, a removal amount distribution corresponding to the difference between the pre-processing shape and the target shape of the workpiece 2 is obtained, and the nozzle head 1 stays with respect to each local surface of the workpiece 2 based on the profile data of the spot machining trace. NC data defining the scanning speed for scanning the nozzle head 1 relative to the surface of the workpiece 2 is created so that the time is determined and the local residence time can be realized. Then, NC data is input to the control unit of the processing apparatus, the nozzle head 1 is scanned relative to the surface of the workpiece 2, and the local removal amount is controlled by controlling the scanning speed. To process. If the removal amount is large, it is difficult to obtain the target shape by one scan, so it is sufficient to set the intermediate target shape and perform a plurality of scans.

  The profile of the spot machining trace can be changed using the gap and back pressure as parameters of the machining conditions. First, the profile data of a plurality of spot machining traces is obtained for each machining condition determined by the gap and back pressure while the nozzle head 1 and the workpiece 2 are stationary. Then, NC data is created by selecting an optimum combination of spot machining trace profiles in order to obtain a target removal amount distribution. Based on the NC data, the gap and back pressure are controlled to control the profile of the spot machining trace, and machining is performed using a plurality of spot machining traces having different profiles.

  Here, as the fine particles, metal oxides such as silicon oxide (silica) and zirconium oxide having a particle size of 10 nm to 5 μm are mainly used. In addition to the single particles, it is also preferable to use aggregated fine particles obtained by aggregating fine particles having a particle diameter of 1 to 100 nm into an aggregate having an average diameter of 0.5 to 5 μm. And as for the water which disperse | distributes microparticles | fine-particles, it is preferable to use ultrapure water or pure water, and the density | concentration of a process liquid is 1-10 vol%.

  In the processing using the profile data, the dwell time of the spot machining trace profile is a parameter used to control the removal depth. The residence time distribution is converted into a scanning speed distribution of the NC stage 4. Features such as the size, removal rate, and reproducibility of the spot processing mark in a stationary state basically determine the shape correction performance. The size and removal speed of the spot machining marks are directly related to the spatial resolution and the machining time, respectively, in the shape correction. The high reproducibility of the characteristics can reduce the number of cycles between processing and measurement performed until the required accuracy is achieved.

  In the present invention, a converging flow path narrowed toward the opening at the tip is provided, and a processing liquid in which fine particles are dispersed in water is supplied to the converging flow path with a predetermined back pressure and discharged from the opening, A current collecting type nozzle having a function of generating a focused flow having a waist portion smaller than the size of the opening is used. In a nozzle-type EEM, a high shear flow is required on the surface to transport particles to the workpiece surface and remove them from the surface. The removal area and removal rate depend on the velocity distribution of the fluid in contact with the surface. The shape of the velocity distribution can be controlled by changing nozzle specifications such as the width, velocity, angle, and standoff distance of the flow path. Here, the standoff distance is defined as the length between the nozzle outlet and the workpiece surface.

  The nozzle used in the conventional nozzle type machining head type EEM has a straight flow path, and its opening is rectangular or circular as shown in FIG. The pressurized fluid is discharged from the nozzle toward the fluid in the container. In this case, since the jet flow is generally in a strong turbulent state, the flow may diverge after exiting from the opening. In order to satisfy both the smallness and removal rate required for stationary spot processing, the standoff distance is selected to be short. A micro static spot processing with a spot size of 500 μm in diameter is realized with a stand-off distance of less than 300 μm.

  More specifically, FIG. 2A shows a conventional DC type nozzle 10 for comparison, and FIG. 2B shows a current collecting type nozzle 20 used in the present invention. The direct current type nozzle 10 includes a straight flow path 12 in which the cross-sectional shape of the internal flow path is the same as that of the opening 11 at the tip. On the other hand, the collecting nozzle 20 includes a converging flow path 22 narrowed toward the opening 21 at the tip, a core 23 having a conical outer surface 24 at the tip, and a conical inner surface 26 at the tip. And an outer cylinder 25 having an opening 21 at the top and a concentric shaft disposed with a predetermined gap between the conical outer surface 24 of the core 23 and the conical inner surface 26 of the outer cylinder 25. Have.

  The collecting nozzle 20 supplies a working fluid to the focusing channel 22 at a predetermined pressure and discharges it from the opening 21, and is smaller than the size of the opening 21 at a certain distance from the opening 21. A function of generating a focused flow 28 having a waist portion 27 is provided. On the other hand, the machining liquid discharged from the direct current nozzle 10 does not become smaller than the size of the opening 11, and becomes a diffusion flow 13 that spreads as the distance from the opening 11 increases. Actually, it is not an extreme diffusion flow 13 as shown in FIG. 2A, but a flow that gradually spreads as the distance from the opening 11 increases. The collecting nozzle 20 has a converged point, and the maximum flow velocity is high even if it is far from the opening 21. Further, compared with the direct current nozzle 10 shown in FIG. 2A, the current collecting nozzle 20 has a narrow velocity distribution on the surface of the work piece and a small removal rate with a high standoff distance. Allows a static spot profile.

  In order to verify the characteristics of the focused flow, several fluid simulations were performed using fluid simulation software (PHOENICS CHAM). The simulation parameters are listed in Table 1. In the case of the collecting nozzle 20, as shown in FIG. 2B, the two flows merge after flowing in through two openings having a width of 500 μm and a thickness of 300 μm. The angle between the two flows is 90 °. On the other hand, the direct current nozzle 10 has a rectangular opening having a size of about 1 mm × 300 μm. The cross-sectional areas of the openings of both nozzles are the same. Three-dimensional velocity and pressure distributions were calculated for both nozzles. The k-ε model included in the software is used to calculate turbulence. In order to quantitatively analyze the effect of the channel structure, the flow velocity in both nozzle openings is set to be the same. FIG. 3 shows simulation results of the straight flow path and the focusing flow path. The velocity distribution on the XZ plane including the center line is shown in FIGS. 3 (a) and 3 (b). The velocity distribution on the surface of 1 μm from the workpiece surface is compared with FIGS. 3 (c) and 3 (d).

  As the flow approaches the workpiece surface, it undergoes a significant change in its velocity direction to rotate from a perpendicular direction to a direction substantially parallel to the wall. Even when the standoff distance is 1 mm, this results in a flow having a high shear rate on the workpiece surface. The fluid pressure increases on the plane at the center where the two flows meet. The mainstream direction changes toward the Y axis. From the viewpoint of workability, the speed near the surface is an important evaluation factor. 3E and 3F show cross-sectional shapes of velocity distributions for two types of nozzles. The velocity distribution profile when the collecting nozzle 20 is used is Gaussian having a full width at half maximum of 0.5 mm. In contrast, the DC nozzle 10 has two peaks in the velocity distribution profile, and the distance between the two peaks is 1 mm, which is the same as the nozzle opening width. In EEM, the shape of the profile of spot machining marks in a stationary state depends on the distribution of the number of particles supplied to the surface of the workpiece and removed from the surface. Since the diameter of the fine particles in this embodiment is about 2 μm, the particles move along the streamline. Comparison of the two profiles shows that a fine static spot profile can be obtained using a collecting nozzle because the removal depth is basically proportional to the velocity close to the workpiece surface.

Next, two types of nozzles having the same flow path structure as that used in the fluid simulation were prepared and attached to the processing apparatus. Several static spot machining traces were machined on the quartz surface and measured with a microscopic interferometer (ZYGO NewView ™ 700) with a field of view of 3.74 × 2.81 mm ² . The speed was also adjusted according to the simulation. The standoff distance was changed from 0.4 mm to 1.8 mm. Experimental parameters are listed in Table 2.

  FIGS. 4A and 4B are enlarged views showing the removal distribution of the profile of the static spot machining trace obtained by using the direct current type nozzle and the current collecting type nozzle each having a standoff distance (gap) of 1 mm. Yes. FIGS. 5 (a) and 5 (b) show the removal distribution of the static spot machining trace profile obtained using a DC nozzle and a collecting nozzle at a standoff distance of 0.4 mm to 1.8 mm, respectively. Yes. FIGS. 6 (a) and 6 (b) show the cross-sectional profiles of spot machining marks obtained using a direct current nozzle and a current collecting nozzle at a standoff distance of 0.4 mm to 1.8 mm, respectively. (A) And (b) has shown the longitudinal cross-sectional profile similarly obtained using the direct current | flow type nozzle and the current collecting type nozzle. It can be seen that the standoff distance (gap) affects the shape, depth, and size of the spot machining mark. FIGS. 8A and 8B show the relationship between the removal amount and the spot size with respect to the standoff distance (gap) in the case of a direct current type nozzle and a current collecting type nozzle, respectively. Here, the spot size is defined as the diameter of the region containing 80% of the total volume.

  When a collecting nozzle is used, the spot size decreases as the standoff distance (gap) increases from 0.4 mm to 1 mm. The minimum spot size is 1.3 mm with a standoff distance (gap) of 1 mm, and the spot diameter gradually increases as the standoff distance (gap) increases. The results show that the spot size and removal rate can be controlled by simply adjusting the standoff distance (gap) without changing the nozzle. Further, from FIGS. 6 and 7, it can be seen that, in the case of the current collecting type nozzle, the profile of the spot machining mark changes greatly according to the stand-off distance (gap). On the other hand, when a direct current nozzle is used, the spot machining trace remains the same regardless of the standoff distance (gap), and the profile does not change much. If it is necessary to change the processing conditions, nozzles of different sizes must be installed. On the other hand, when the current collecting type nozzle is used, it is possible to change the profile of the spot processing mark by changing the processing conditions such as the gap while maintaining the same nozzle. If the shape of the opening of the current collecting nozzle is a rotationally symmetric shape such as a circle, ideally, the spot machining trace is also rotationally symmetric.

  Next, in order to evaluate the roughness of the EEM processed surface, raster scanning was performed over a 5 mm square area on the quartz surface, and FIG. 9 shows the surface roughness before and after the treatment using the collecting nozzle. . The RMS values before and after the treatment are almost the same, so that the current collecting type nozzle can also be used for advanced optical element shape correction. It can be seen that the static spot profiles in FIGS. 4 (a) and 4 (b) are in good agreement with the velocity distributions in FIGS. 3 (c) and 3 (d), respectively. Therefore, the shape of a stationary spot profile with various forms of nozzles can be predicted using a fluid simulator.

  The specific structure of the current collecting nozzle 20 will be described in more detail with reference to FIGS. In the present embodiment, the current collecting type nozzle 20 projects from the core 23 at the center, the first member 29 having a joint surface 30 around the core 23, and the outer cylinder 25 at the center. And the second member 31 provided with the joining surface 32 around the outer cylinder 25 is joined to the first member 29 from the opposite side to the first member 29 in a sealed state. A main flow path 33 is formed at the center of the core 23, and a plurality of branch holes 34,... Communicating with the main flow path 33 are formed on the side surface closer to the base than the conical outer surface 24 of the core 23. And the converging inner surface 26 of the outer cylinder 25, the working fluid is supplied from the main channel 33 through the branch holes 34,. Further, the current collecting type nozzle 20 has a conical inner surface 26 of the outer cylinder 25 of the second member 31 extending to the joining surface 32 and a side surface on the base side of the conical outer surface 24 of the core 23 of the first member 29. The buffer flow path 35 is formed in this.

  Further, an O-ring groove 36 is provided on one of the bonding surface 30 of the first member 29 or the bonding surface 32 of the second member 31 so as to surround the flow path, and an O-ring 37 fitted in the O-ring groove 36. Is pressed against the other joint surface and sealed. Further, an annular step 38 is provided around the joint surface 30 of the first member 29 so that the core 23 and the outer cylinder 25 can be assembled accurately and concentrically. It is the structure which fits. Although not shown, the first member 29 and the second member 31 fasten the outside of the O-ring groove 36 with screws.

  The opening 21 of the current collecting nozzle 20 of the present embodiment is an annular slit having an inner diameter of 1 mm (diameter at the tip of the core 23) and a width of the focusing flow path 22 of 300 μm. First, when the flow rate of this nozzle was measured with pure water, the value was almost the theoretical value as shown in FIG. By providing the buffer flow path 35, it has a structure with little pressure loss. Then, the atmosphere was changed to the machining fluid, and the experiment was performed with the gap and back pressure changed. As a result, a machining trace smaller than the nozzle opening was obtained. FIG. 13 is a graph of the half width of the spot machining trace with respect to the gap when the back pressure is 2, 3, and 4 atm, and it can be seen that there is no dramatic change in the size of the machining trace even if the gap is released. . FIG. 14 is a graph of the processing rate of the spot processing trace with respect to the gap when the back pressure is 2, 3, and 4 atm. From this graph, it can be seen that even a long gap, which was not subjected to EEM processing with a conventional DC nozzle, can be processed with a current collecting nozzle. It was also confirmed that when the gap was small, the machining rate could be changed significantly by changing the back pressure. That is, it is suggested that the profile of the spot machining mark can be controlled by controlling the back pressure.

  In EEM, it has been experimentally confirmed that the shape of the spot processing mark profile in the stationary state is controlled by realizing a focused flow state between the nozzle outlet and the workpiece surface and controlling the gap and back pressure. The possibility of machining complex shapes and steep shapes using spot machining traces of multiple profiles was shown. And the simulation results show that the collecting nozzle sharpens the velocity distribution on the workpiece surface. Moreover, the result of the processing experiment confirmed the thing of simulation. It was found that the shape of the flow path affects the processing parameters. In order to control the shape of the static spot machining trace profile, the basic idea of considering not only the size of the nozzle hole but also the channel structure is the various EEM optical manufacturing processes, especially advanced with complex shapes It can be widely applied to various optical systems.

DESCRIPTION OF SYMBOLS 1 Nozzle head 2 Work piece 3 Water tank 4 NC stage 5 Diaphragm pump 6 Damper 7 Air compressor 8 Regulator 9 Pressure gauge 10 DC type nozzle 11 Opening part 12 Straight flow path 13 Diffusion flow 20 Concentration type nozzle 21 Opening part 22 Focusing Flow path 23 Core 24 Conical outer surface 25 Outer cylinder 26 Conical inner surface 27 Waist part 28 Concentrated flow 29 First member 30 Joint surface 31 Second member 32 Joint surface 33 Main flow path 34 Branch hole 35 Buffer flow path 36 O-ring groove 37 O-ring 38 Annular steps

Claims (2)

A predetermined gap is provided between the tip of the nozzle and the workpiece, and the workpiece is placed in the water. A processing liquid in which fine particles are dispersed in water is discharged from the nozzle opening at a predetermined back pressure, and is applied to the surface of the workpiece. A high shear flow is generated along the surface, the fine particles bonded to the surface atoms by the solid-state chemical reaction are separated by the flow of water , and the nozzle is moved against the workpiece surface using the processing principle of removing the surface atoms together with the fine particles . In the EEM processing method that controls the local removal amount by scanning relatively and controlling the stay time, using one nozzle, changing at least one of the gap and the back pressure in a stationary state , Obtain spot processing trace profile data under each processing condition, control the spot processing trace profile by controlling the gap and back pressure, EEM processing method characterized by comprising by processing by Kasaneawashi a plurality of spots working mark to. A predetermined gap is provided between the tip of the nozzle and the workpiece, and the workpiece is placed in the water. A processing liquid in which fine particles are dispersed in water is discharged from the nozzle opening at a predetermined back pressure, and is applied to the surface of the workpiece. A high shear flow is generated along the surface, the fine particles bonded to the surface atoms by the solid-state chemical reaction are separated by the flow of water, and the nozzle is moved against the workpiece surface using the processing principle of removing the surface atoms together with the fine particles. In the EEM processing method of controlling by scanning relatively and controlling the amount of local removal by controlling the staying time, a plurality of types of nozzles are used, and the processing conditions of the gap and the back pressure are used for each nozzle. By obtaining spot processing trace profile data and changing the nozzle, the spot processing trace profile is changed, and multiple spot processing traces with different profiles are overlapped and processed. EEM processing wherein the.

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