rus
Issue #3/2022
V. V. Lapshin, E. M. Zakharevich, A. S. Narikovich, A. S. Korotkov, I. I. Lyatun, A. A. Snigirev
Processing Technology Development for Hard-Alloy Punches with a Linear Parabolic Profile
Processing Technology Development for Hard-Alloy Punches with a Linear Parabolic Profile
DOI: 10.22184/1993-7296.FRos.2022.16.3.184.196
The article describes the processing technology for hard-alloy punches with a linear parabolic profile. The processing kinematics for the surfaces considered is presented. In order to provide the required kinematics using the available equipment, an additional linear machine axis has been developed. The dressing method for the grinding head edges to a certain radius has also been developed. The processed profile control method is explained. The results of the developed method application for processing of punches using various grinding heads are presented.
The article describes the processing technology for hard-alloy punches with a linear parabolic profile. The processing kinematics for the surfaces considered is presented. In order to provide the required kinematics using the available equipment, an additional linear machine axis has been developed. The dressing method for the grinding head edges to a certain radius has also been developed. The processed profile control method is explained. The results of the developed method application for processing of punches using various grinding heads are presented.
Теги: diamond grinding dressing grinding heads punches x-ray refractive lenses алмазное шлифование правка пуансоны рентгеновские преломляющие линзы шлифовальные головки
Processing Technology Development for Hard-Alloy Punches with a Linear Parabolic Profile
V. V. Lapshin 1, E. M. Zakharevich 1, A. S. Narikovich 2, A. S. Korotkov 2, I. I. Lyatun 2, A. A. Snigirev 2
Scientific and Production Association “Aspherika” LLC, Moscow, Russia
Immanuel Kant Baltic Federal University, Kaliningrad, Russia
The article describes the processing technology for hard-alloy punches with a linear parabolic profile. The processing kinematics for the surfaces considered is presented. In order to provide the required kinematics using the available equipment, an additional linear machine axis has been developed. The dressing method for the grinding head edges to a certain radius has also been developed. The processed profile control method is explained. The results of the developed method application for processing of punches using various grinding heads are presented.
Keywords: diamond grinding, dressing, punches, grinding heads, x-ray refractive lenses
Received on: 28.04.2022
Accepted on: 12.05.2022
Introduction
The use of refractive X-ray optics for the development of methods of X-ray focusing and imaging in order to study the microscopic and nano-scale objects has been successfully performed for 25 years [1]. Since the first experimental demonstration of their use, the X-ray refractive lenses have been permanently included in the toolkit of up-to-date specialized synchrotron radiation sources due to a number of advantages: they are easily adjusted, relatively insensitive to misorientation and mechanical vibrations, and are also able to withstand high thermal and radiation loads [2–4]. In comparison to the X-ray mirrors and crystal monochromators, the lenses do not change the direction of the primary X-ray beam propagation that significantly simplifies the optical circuit of synchrotron stations.
The first refractive lenses were a series of cylindrical apertures made in an aluminum block while forming a compound refractive lens (CRL). A large number of apertures made it possible to compensate for the weak X-ray refraction effect and, as a result, to obtain an acceptable focal distance in the energy range from 5 to 40 keV. According to the wave optics theory, such a focusing lens has strong spherical aberrations caused by the circular aperture profile. The solution to the problem of spherical aberrations is the use of a parabolic lens profile [5].
The operating principle of an X-ray lens is similar to that of a classical optical lens. It is based on the refraction effect, but at the same time, the refractive index of X-ray materials is less than one that determines the concave profile of focusing optics. Depending on the profile shape of single lenses forming the CPL, two types can be distinguished – for one-dimensional and two-dimensional X-ray focusing. Therefore, the recess profile shape for one-dimensional focusing has a linear parabolic profile, while the profile shape for two-dimensional focusing is a rotational paraboloid. The ultimate lens resolution and the quality of the image transmitted by the lens are directly affected not only by the internal material structure, but also by the perfection degree of the geometric lens specifications, such as the lens profile accuracy and the optical surface roughness [6].
The solution to the problem of obtaining a high-quality parabolic lens profile is primarily achieved by producing the special hard-alloy molds with a small bending radius (up to 50 µm), a small profile shape error (less than 1 µm), and high surface purity (RMS ~10 nm) using the ultra-precision CNC lathes [7]. Moreover, the manufacture of punches with the rotational paraboloid shape does not require any changes in the kinematic machining flow diagrams, while the manufacture of punches with a linear parabolic profile requires changes in the processing procedure for the parts. This paper presents the results of the developed processing technology for punches with a linear parabolic profile.
The workpiece (Fig. 1) is a hard-alloy rod with a diameter of 6 mm, on one end of which there is a protrusion, having a parabolic shape in its section. The linear parabolic protrusion also has recesses on both sides and its length is 4 mm. Moreover, the flattened surface is available along the entire rod.
The parabolic profile (Fig. 2) is described by the following formula:
z = ax2,
where a is a parameter used for the parabola curvature and is determined by the product consumer. The parabola base shall have a rounding radius of no more than 0.1 mm.
The following requirements for accuracy and quality are imposed on the part:
Features of the product
processing kinematics
Processing of the hard-alloy punches with a parabolic rotation body profile was considered in the articles [8, 9]. In order to manufacture the punch with a linear parabolic profile, the processing kinematics described in the articles are not suitable. Instead of two linear and two circular axes, three linear and one circular axes shall be used. For this purpose, it is necessary to perform processing using a three-axis-controlled machine. The parabola profile is formed based on the X and Z coordinates, and the tool or part shall oscillate along the Y axis, while there is a one-step displacement along the contour per one double move along the Y axis (Fig. 3).
Since the high requirements are set for the machined punch surfaces in terms of accuracy and surface quality, it is necessary to use the ultra-precise equipment. Scientific and Production Association “Aspherika” LLC has an Aspherika-F3 ultra-precision CNC machine in its fleet that has the following design features:
Since the machine has only two linear axes of movement (X, Z), then the punches with a linear parabolic profile cannot be machined using the basic machine configuration. In order to perform the processing, an additional Y-axis was developed (Fig. 4) that would oscillate the workpiece in the vertical direction. Since the workpieces are subject to the high requirements for the processing quality, the additional Y-axis is also equipped with the aerostatic guides.
The Y-axis consists of the following basic elements: a base, aerostatic guides, a slide, and a pneumatic cylinder. The slide moves up and down on the aerostatic guides with the help of a pneumatic cylinder, while the combined stroke is 25 mm. The smooth workpiece movement along the Y axis is achieved due to the use of a precision pneumatic cylinder.
Thus, due to the additional Y-axis, the Aspherika-F3 machine can ensure the processing of punches with a linear parabolic profile. The workpiece is fixed in a mandrel installed on the Y-axis slide and executes oscillations. The grinding spindle with an abrasive tool is mounted on the machine Z axis slide, and the Y axis is installed on the X axis of the machine.
Dressing technology
for an abrasive tool
The diamond grinding heads with various grain sizes and bonds are used for processing the hard-alloy punches.
In order to process a parabolic surface with a shape accuracy of up to 1 µm, it is necessary to know the grinding head radius R (Fig. 5), while the radius shall be 0.1 mm or less (to ensure the radius at the parabola base) and have the same value along the entire perimeter.
Typically, the grinding heads do not have any particular radius at the edge, and are variable along the perimeter. To ensure the required radius of the grinding head, it is necessary to perform a dressing operation. As a rule, dressing of the grinding heads is performed on the outer cylindrical surface using the straightening sticks or rollers. However, for processing the parts considered in the article, it is necessary to perform the profile dressing of the grinding heads along the radius.
In order to perform such dressing, a special setup has been developed, implemented for the Aspherika-F3 machine. The dressing diagram is shown in Figures 6, 7. The dressed grinding head was mounted on a high-speed aerostatic grinding spindle that was mounted on the Z-axis of the machine. The dressing wheel was fixed in the grinding spindle mounted on the X-axis bracket, while the rotation axis of the dressing wheel was perpendicular to the rotation axis of the dressing head. In the dressing process, the dressing wheel passes along the dressed head generatrix along a given trajectory, forming the required radius R (Fig. 7).
The grinding wheel with a multilayer composite electrolytic nickel-based coating was used as a dressing wheel. The grain size of a dressing wheel diamond was 125–160 µm.
According to the developed technology, the grinding heads were dressed (Fig. 8). Such heads were used for roughing and finishing the punches with a linear parabolic profile.
The punch roughing was performed using a grinding head with a grain size of 100–125 µm on a metal bond by Haefeli (Switzerland). Prior to the radius dressing operation, the grinding head was examined under a microscope in order to determine the current edge condition, as well as to determine the required material removal during dressing. Figure 9a shows the initial condition of the grinding head edge. As can be seen from the figure, the edge of the head is worn, since it has been previously used for other grinding operations and does not have a well-pronounced radius required for the punch processing.
The roughing head is dressed in several passes, and the total removal was 0.08 mm per diameter. The dressing modes are as follows: the dressing wheel rotational speed is 20,000 rpm, the dressed grinding head rotational speed is 10,000 rpm, the contour processing speed is 10 mm / min. 0.01 mm per diameter was removed from the dressed head in one pass.
After dressing, the grinding head was also examined under a microscope in order to determine the resulting radius. Figure 9b shows an example of measuring the dressed grinding head. As can be seen from the figure, the defects initially available on the head were eliminated and the resulting rounding radius was R = 0.1 mm.
The finishing grinding head was dressed using a similar process. The grinding head with a grain size of 7–10 microns on a polyurethane bond was made by special order by Research and Production Complex “Electrocrystal” LLC (Russia). Figure 10 a, b shows the measurements of a finishing grinding head before and after dressing. Dressing was performed using the same modes as for the roughing grinding head. The resulting radius was also R = 0.1 mm.
Punch processing technology
A special setup was designed for the Aspherika F‑3 machine in order to process the punches with a linear parabolic profile. The processing outline is shown in Fig.11. The grinding head was installed in a high-speed aerostatic spindle mounted on the Z slide bracket. The workpiece to be machined was fixed on the mandrel mounted on the Y axis slide. During processing, the workpiece made oscillatory movements in the vertical plane, and the grinding head was displaced relative to the workpiece along a given trajectory during each double stroke. The required trajectory was provided by the simultaneous movement of the slides along the X and Z axes. The control program was prepared in such a way as to ensure the even pitches along the parabola profile. The setup for the grinding head dressing was also located on the X axis slide together with an additional vertical Y axis.
The parabola profile was formed by separate processing on both sides, while the grinding head was accurately attached on both sides of the workpiece in order to ensure the absence of mismatches at the top of the parabola.
The developed technology for workpiece processing consists of the following stages:
Punch processing results
A number of punches with various parabolic profiles were processed according to the developed technology. The formula describing the parabolic surface was set by the product customer.
Processing (Fig. 12) was performed in the following modes:
The profiling sequence of the parabolic surface is shown in Fig. 13. The workpieces were controlled using a video-measuring microscope. A 2D profile of the required surface shape was superimposed on the resulting image using the special microscope software, and the remaining allowance was assessed. Figure 13 shows the sequence of obtaining a type 1 and type 2 parabola. The machined part before and after processing of the recesses is shown in Fig.14.
The final inspection of the punches was performed using a unique scientific installation “Scientific and educational multifunctional complex for the synchrotron research preparation and performance” (USI “SynchrotronLike”), using the high-resolution radiography method based on the MetalJet microfocus laboratory X-ray source with a characteristic line of 9.251 keV (Ga Kα) and a motorized adjustment system [10]. A Rigaku camera with a pixel size of 0.55 μm was used to record images with the high spatial resolution. The distance between the radiation source and the sample (set of punches) was 38.3 cm, and the distance between the sample and the camera was 1.2 cm. The main selection criteria for the measurement method of typical parameters were reproducibility and reliability of the measurement results, as well as the ease of method implementation and universality. Figure 15 shows a radiographic image of a set of punches with a nominal radius of 500 µm (Figure 15a). The analysis of the images obtained and measurement of accuracy of the punch parabolic profile (Figures 15b‑15c) were performed using the metrological approach applied for X-ray CPL diagnostics [11].
According to the results of the punch quality study and their compliance with the design requirements, it is experimentally shown that the proposed technology for processing the punches with a linear parabolic profile provides the required accuracy of the tool parabolic surface for the produced refractive lenses that completely meet the requirements of up-to-date synchrotron radiation sources.
Conclusion
The processing technology for punches with a linear parabolic profile has been developed and implemented. To ensure the processing kinematics using the available equipment, an additional vertical Y-axis with the aerostatic guides has been developed. The dressing technology for the grinding heads with a certain edge radius is also presented.
A number of punches with a linear parabolic profile were processed according to the developed technology. A study of the machined surface quality and accuracy showed that the required accuracy and surface roughness had been achieved. Possible dressing of the grinding heads to the required radius has also been confirmed. The study of the dressed grinding head accuracy and the machined punch profile accuracy was carried out using a video-measuring microscope.
The development prospects of the provided punch processing technology provide for an ultra-precision machine that allows increasing automation and efficiency. Such a machine shall have the following features:
Scientific and Production Association “Aspherika” LLC provides the development and manufacture of such machines according to the customer’s terms of reference.
Acknowledgement
The scientific equipment of the unique scientific installation “Scientific and educational multifunctional complex for the synchrotron research preparation and performance” (USI “SynchrotronLike”) was used for this paper. The experimental study of the high-precision tool was funded by the strategic academic leadership program “Priority 2030” at the Immanuel Kant Baltic Federal University. The required consumables were purchased with the support of the Ministry of Science and Higher Education as a part of the grant No. 075-15-2021-1362.
ABOUT AUTHORS
Lapshin Vasilii Vladimirovich, senior engineer researcher, LLC The Scientific and Production Association Aspherica”, lapshin_v@aspherica.ru, Moscow, Russia.
ORCID: 0000-0002-6971-8534
Zakharevich Evgeniy Mefodievich, chief technologist, LLC The Scientific and Production Association Aspherica”, zaharev@gmail.com, Moscow, Russia.
ORCID: 0000-0001-6997-3335
Narikovich Anton Sergeevich, research engineer, Immanuel Kant Baltic Federal University, Kaliningrad, Russia.
ORCID: 0000-0003-2570-1818
Korotkov Aleksandr Sergeevich, laboratory assistant, Immanuel Kant Baltic Federal University, Kaliningrad, Russia.
ORCID: 0000-0001-9425-8368
Lyatun Ivan Igorevich, Researcher, Immanuel Kant Baltic Federal University, Kaliningrad, Russia.
ORCID: 0000-0002-4988-8077
Snigirev Anatoly Alexandrovich, Cand.of Sciences(Math.&Phys), Professor, Head of the International Science Research Center “Coherent X-ray Optics for Megascience Facilities”, Immanuel Kant Baltic Federal University, Kaliningrad, Russia.
ORCID: 0000-0002-8892-1925
Contribution by the members
of the team of authors
Lapshin V. V., Zakharevich E. M.: development of technology for manufacturing punches, technology for filling grinding heads; Narikovich A. S.: analysis of the literature, description of the results, formation of the conclusions of the study; Korotkov A. S.: collection of experimental data, tabular and graphical presentation of the results; Lyatun I. I.: setting up a research methodology, conducting research and forming research conclusions; Snigirev A. A.: significant contribution to the concept and design of the research, carried out a critical review of the article for important intellectual content, approved the final version of the article before submitting it for publication.
Conflict of interest
The authors claim that they have no conflict of interest. The article was prepared on the basis of work by all members of the team of authors. All authors took part in writing the article and supplemented the manuscript in part of their work.
V. V. Lapshin 1, E. M. Zakharevich 1, A. S. Narikovich 2, A. S. Korotkov 2, I. I. Lyatun 2, A. A. Snigirev 2
Scientific and Production Association “Aspherika” LLC, Moscow, Russia
Immanuel Kant Baltic Federal University, Kaliningrad, Russia
The article describes the processing technology for hard-alloy punches with a linear parabolic profile. The processing kinematics for the surfaces considered is presented. In order to provide the required kinematics using the available equipment, an additional linear machine axis has been developed. The dressing method for the grinding head edges to a certain radius has also been developed. The processed profile control method is explained. The results of the developed method application for processing of punches using various grinding heads are presented.
Keywords: diamond grinding, dressing, punches, grinding heads, x-ray refractive lenses
Received on: 28.04.2022
Accepted on: 12.05.2022
Introduction
The use of refractive X-ray optics for the development of methods of X-ray focusing and imaging in order to study the microscopic and nano-scale objects has been successfully performed for 25 years [1]. Since the first experimental demonstration of their use, the X-ray refractive lenses have been permanently included in the toolkit of up-to-date specialized synchrotron radiation sources due to a number of advantages: they are easily adjusted, relatively insensitive to misorientation and mechanical vibrations, and are also able to withstand high thermal and radiation loads [2–4]. In comparison to the X-ray mirrors and crystal monochromators, the lenses do not change the direction of the primary X-ray beam propagation that significantly simplifies the optical circuit of synchrotron stations.
The first refractive lenses were a series of cylindrical apertures made in an aluminum block while forming a compound refractive lens (CRL). A large number of apertures made it possible to compensate for the weak X-ray refraction effect and, as a result, to obtain an acceptable focal distance in the energy range from 5 to 40 keV. According to the wave optics theory, such a focusing lens has strong spherical aberrations caused by the circular aperture profile. The solution to the problem of spherical aberrations is the use of a parabolic lens profile [5].
The operating principle of an X-ray lens is similar to that of a classical optical lens. It is based on the refraction effect, but at the same time, the refractive index of X-ray materials is less than one that determines the concave profile of focusing optics. Depending on the profile shape of single lenses forming the CPL, two types can be distinguished – for one-dimensional and two-dimensional X-ray focusing. Therefore, the recess profile shape for one-dimensional focusing has a linear parabolic profile, while the profile shape for two-dimensional focusing is a rotational paraboloid. The ultimate lens resolution and the quality of the image transmitted by the lens are directly affected not only by the internal material structure, but also by the perfection degree of the geometric lens specifications, such as the lens profile accuracy and the optical surface roughness [6].
The solution to the problem of obtaining a high-quality parabolic lens profile is primarily achieved by producing the special hard-alloy molds with a small bending radius (up to 50 µm), a small profile shape error (less than 1 µm), and high surface purity (RMS ~10 nm) using the ultra-precision CNC lathes [7]. Moreover, the manufacture of punches with the rotational paraboloid shape does not require any changes in the kinematic machining flow diagrams, while the manufacture of punches with a linear parabolic profile requires changes in the processing procedure for the parts. This paper presents the results of the developed processing technology for punches with a linear parabolic profile.
The workpiece (Fig. 1) is a hard-alloy rod with a diameter of 6 mm, on one end of which there is a protrusion, having a parabolic shape in its section. The linear parabolic protrusion also has recesses on both sides and its length is 4 mm. Moreover, the flattened surface is available along the entire rod.
The parabolic profile (Fig. 2) is described by the following formula:
z = ax2,
where a is a parameter used for the parabola curvature and is determined by the product consumer. The parabola base shall have a rounding radius of no more than 0.1 mm.
The following requirements for accuracy and quality are imposed on the part:
- the parabolic profile surface roughness Ra shall be not more than 0.01 µm;
- the parabolic profile shape accuracy is 1 µm;
- the end on which the protrusion is made shall have a flatness deviation of 1 µm and a roughness Ra of not more than 0.01 µm;
- the parabolic profile shall be parallel to the flattened surface plane with an accuracy of 1 µm.
Features of the product
processing kinematics
Processing of the hard-alloy punches with a parabolic rotation body profile was considered in the articles [8, 9]. In order to manufacture the punch with a linear parabolic profile, the processing kinematics described in the articles are not suitable. Instead of two linear and two circular axes, three linear and one circular axes shall be used. For this purpose, it is necessary to perform processing using a three-axis-controlled machine. The parabola profile is formed based on the X and Z coordinates, and the tool or part shall oscillate along the Y axis, while there is a one-step displacement along the contour per one double move along the Y axis (Fig. 3).
Since the high requirements are set for the machined punch surfaces in terms of accuracy and surface quality, it is necessary to use the ultra-precise equipment. Scientific and Production Association “Aspherika” LLC has an Aspherika-F3 ultra-precision CNC machine in its fleet that has the following design features:
- aerostatic guides on the X and Z linear axes;
- the machine frame is installed on the antivibration mounts;
- use of the direct linear drive units;
- minimum programmable displacement is 10 nm.
Since the machine has only two linear axes of movement (X, Z), then the punches with a linear parabolic profile cannot be machined using the basic machine configuration. In order to perform the processing, an additional Y-axis was developed (Fig. 4) that would oscillate the workpiece in the vertical direction. Since the workpieces are subject to the high requirements for the processing quality, the additional Y-axis is also equipped with the aerostatic guides.
The Y-axis consists of the following basic elements: a base, aerostatic guides, a slide, and a pneumatic cylinder. The slide moves up and down on the aerostatic guides with the help of a pneumatic cylinder, while the combined stroke is 25 mm. The smooth workpiece movement along the Y axis is achieved due to the use of a precision pneumatic cylinder.
Thus, due to the additional Y-axis, the Aspherika-F3 machine can ensure the processing of punches with a linear parabolic profile. The workpiece is fixed in a mandrel installed on the Y-axis slide and executes oscillations. The grinding spindle with an abrasive tool is mounted on the machine Z axis slide, and the Y axis is installed on the X axis of the machine.
Dressing technology
for an abrasive tool
The diamond grinding heads with various grain sizes and bonds are used for processing the hard-alloy punches.
In order to process a parabolic surface with a shape accuracy of up to 1 µm, it is necessary to know the grinding head radius R (Fig. 5), while the radius shall be 0.1 mm or less (to ensure the radius at the parabola base) and have the same value along the entire perimeter.
Typically, the grinding heads do not have any particular radius at the edge, and are variable along the perimeter. To ensure the required radius of the grinding head, it is necessary to perform a dressing operation. As a rule, dressing of the grinding heads is performed on the outer cylindrical surface using the straightening sticks or rollers. However, for processing the parts considered in the article, it is necessary to perform the profile dressing of the grinding heads along the radius.
In order to perform such dressing, a special setup has been developed, implemented for the Aspherika-F3 machine. The dressing diagram is shown in Figures 6, 7. The dressed grinding head was mounted on a high-speed aerostatic grinding spindle that was mounted on the Z-axis of the machine. The dressing wheel was fixed in the grinding spindle mounted on the X-axis bracket, while the rotation axis of the dressing wheel was perpendicular to the rotation axis of the dressing head. In the dressing process, the dressing wheel passes along the dressed head generatrix along a given trajectory, forming the required radius R (Fig. 7).
The grinding wheel with a multilayer composite electrolytic nickel-based coating was used as a dressing wheel. The grain size of a dressing wheel diamond was 125–160 µm.
According to the developed technology, the grinding heads were dressed (Fig. 8). Such heads were used for roughing and finishing the punches with a linear parabolic profile.
The punch roughing was performed using a grinding head with a grain size of 100–125 µm on a metal bond by Haefeli (Switzerland). Prior to the radius dressing operation, the grinding head was examined under a microscope in order to determine the current edge condition, as well as to determine the required material removal during dressing. Figure 9a shows the initial condition of the grinding head edge. As can be seen from the figure, the edge of the head is worn, since it has been previously used for other grinding operations and does not have a well-pronounced radius required for the punch processing.
The roughing head is dressed in several passes, and the total removal was 0.08 mm per diameter. The dressing modes are as follows: the dressing wheel rotational speed is 20,000 rpm, the dressed grinding head rotational speed is 10,000 rpm, the contour processing speed is 10 mm / min. 0.01 mm per diameter was removed from the dressed head in one pass.
After dressing, the grinding head was also examined under a microscope in order to determine the resulting radius. Figure 9b shows an example of measuring the dressed grinding head. As can be seen from the figure, the defects initially available on the head were eliminated and the resulting rounding radius was R = 0.1 mm.
The finishing grinding head was dressed using a similar process. The grinding head with a grain size of 7–10 microns on a polyurethane bond was made by special order by Research and Production Complex “Electrocrystal” LLC (Russia). Figure 10 a, b shows the measurements of a finishing grinding head before and after dressing. Dressing was performed using the same modes as for the roughing grinding head. The resulting radius was also R = 0.1 mm.
Punch processing technology
A special setup was designed for the Aspherika F‑3 machine in order to process the punches with a linear parabolic profile. The processing outline is shown in Fig.11. The grinding head was installed in a high-speed aerostatic spindle mounted on the Z slide bracket. The workpiece to be machined was fixed on the mandrel mounted on the Y axis slide. During processing, the workpiece made oscillatory movements in the vertical plane, and the grinding head was displaced relative to the workpiece along a given trajectory during each double stroke. The required trajectory was provided by the simultaneous movement of the slides along the X and Z axes. The control program was prepared in such a way as to ensure the even pitches along the parabola profile. The setup for the grinding head dressing was also located on the X axis slide together with an additional vertical Y axis.
The parabola profile was formed by separate processing on both sides, while the grinding head was accurately attached on both sides of the workpiece in order to ensure the absence of mismatches at the top of the parabola.
The developed technology for workpiece processing consists of the following stages:
- Roughing of the workpiece in order to make recesses on both sides of the parabola;
- Metrological control of the workpiece and roughing grinding head;
- Dressing of the roughing grinding head for processing along the contours;
- Metrological control of the dressed grinding head;
- Processing of the desired workpiece profile with a roughing grinding head;
- Metrological control of the processed workpiece and adjustment of the control program in the CNC system;
- Repetition of stages 5 and 6 until the minimum deviation of the processed profile from the theoretical one is achieved. If necessary, the grinding head shall be redressed;
- Dressing of the finishing grinding head;
- Processing of the desired workpiece profile with a finishing grinding head;
- Metrological control of the processed workpiece;
- Repetition of stages 9 and 10 until the required roughness of the processed profile is obtained;
- Turning the workpiece by 90° and processing of the recesses of the linear parabolic profile from both sides.
Punch processing results
A number of punches with various parabolic profiles were processed according to the developed technology. The formula describing the parabolic surface was set by the product customer.
Processing (Fig. 12) was performed in the following modes:
- rotational speed of the grinding head was 20000 rpm;
- the displacement value along the parabola profile per double step: 5 µm for roughing, 2 µm for finishing;
- the duration of double stroke was 1.7 seconds.
The profiling sequence of the parabolic surface is shown in Fig. 13. The workpieces were controlled using a video-measuring microscope. A 2D profile of the required surface shape was superimposed on the resulting image using the special microscope software, and the remaining allowance was assessed. Figure 13 shows the sequence of obtaining a type 1 and type 2 parabola. The machined part before and after processing of the recesses is shown in Fig.14.
The final inspection of the punches was performed using a unique scientific installation “Scientific and educational multifunctional complex for the synchrotron research preparation and performance” (USI “SynchrotronLike”), using the high-resolution radiography method based on the MetalJet microfocus laboratory X-ray source with a characteristic line of 9.251 keV (Ga Kα) and a motorized adjustment system [10]. A Rigaku camera with a pixel size of 0.55 μm was used to record images with the high spatial resolution. The distance between the radiation source and the sample (set of punches) was 38.3 cm, and the distance between the sample and the camera was 1.2 cm. The main selection criteria for the measurement method of typical parameters were reproducibility and reliability of the measurement results, as well as the ease of method implementation and universality. Figure 15 shows a radiographic image of a set of punches with a nominal radius of 500 µm (Figure 15a). The analysis of the images obtained and measurement of accuracy of the punch parabolic profile (Figures 15b‑15c) were performed using the metrological approach applied for X-ray CPL diagnostics [11].
According to the results of the punch quality study and their compliance with the design requirements, it is experimentally shown that the proposed technology for processing the punches with a linear parabolic profile provides the required accuracy of the tool parabolic surface for the produced refractive lenses that completely meet the requirements of up-to-date synchrotron radiation sources.
Conclusion
The processing technology for punches with a linear parabolic profile has been developed and implemented. To ensure the processing kinematics using the available equipment, an additional vertical Y-axis with the aerostatic guides has been developed. The dressing technology for the grinding heads with a certain edge radius is also presented.
A number of punches with a linear parabolic profile were processed according to the developed technology. A study of the machined surface quality and accuracy showed that the required accuracy and surface roughness had been achieved. Possible dressing of the grinding heads to the required radius has also been confirmed. The study of the dressed grinding head accuracy and the machined punch profile accuracy was carried out using a video-measuring microscope.
The development prospects of the provided punch processing technology provide for an ultra-precision machine that allows increasing automation and efficiency. Such a machine shall have the following features:
- three linear controlled axes on the aerostatic bearings (X, Y, Z);
- one circular axis C on the aerostatic bearings for precise punch turning;
- availability of a high-speed aerostatic grinding spindle (S axis);
- availability of a spindle for the grinding head dressing (S1 axis);
- availability of a built-in microscope to control the workpieces and grinding heads on the machine.
Scientific and Production Association “Aspherika” LLC provides the development and manufacture of such machines according to the customer’s terms of reference.
Acknowledgement
The scientific equipment of the unique scientific installation “Scientific and educational multifunctional complex for the synchrotron research preparation and performance” (USI “SynchrotronLike”) was used for this paper. The experimental study of the high-precision tool was funded by the strategic academic leadership program “Priority 2030” at the Immanuel Kant Baltic Federal University. The required consumables were purchased with the support of the Ministry of Science and Higher Education as a part of the grant No. 075-15-2021-1362.
ABOUT AUTHORS
Lapshin Vasilii Vladimirovich, senior engineer researcher, LLC The Scientific and Production Association Aspherica”, lapshin_v@aspherica.ru, Moscow, Russia.
ORCID: 0000-0002-6971-8534
Zakharevich Evgeniy Mefodievich, chief technologist, LLC The Scientific and Production Association Aspherica”, zaharev@gmail.com, Moscow, Russia.
ORCID: 0000-0001-6997-3335
Narikovich Anton Sergeevich, research engineer, Immanuel Kant Baltic Federal University, Kaliningrad, Russia.
ORCID: 0000-0003-2570-1818
Korotkov Aleksandr Sergeevich, laboratory assistant, Immanuel Kant Baltic Federal University, Kaliningrad, Russia.
ORCID: 0000-0001-9425-8368
Lyatun Ivan Igorevich, Researcher, Immanuel Kant Baltic Federal University, Kaliningrad, Russia.
ORCID: 0000-0002-4988-8077
Snigirev Anatoly Alexandrovich, Cand.of Sciences(Math.&Phys), Professor, Head of the International Science Research Center “Coherent X-ray Optics for Megascience Facilities”, Immanuel Kant Baltic Federal University, Kaliningrad, Russia.
ORCID: 0000-0002-8892-1925
Contribution by the members
of the team of authors
Lapshin V. V., Zakharevich E. M.: development of technology for manufacturing punches, technology for filling grinding heads; Narikovich A. S.: analysis of the literature, description of the results, formation of the conclusions of the study; Korotkov A. S.: collection of experimental data, tabular and graphical presentation of the results; Lyatun I. I.: setting up a research methodology, conducting research and forming research conclusions; Snigirev A. A.: significant contribution to the concept and design of the research, carried out a critical review of the article for important intellectual content, approved the final version of the article before submitting it for publication.
Conflict of interest
The authors claim that they have no conflict of interest. The article was prepared on the basis of work by all members of the team of authors. All authors took part in writing the article and supplemented the manuscript in part of their work.
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