WO2023045477A1

WO2023045477A1 - Method for manufacturing three-dimensional structure

Info

Publication number: WO2023045477A1
Application number: PCT/CN2022/103373
Authority: WO
Inventors: 史为; 王贤浩; 邱婷婷
Original assignee: 卡尔蔡司（上海）管理有限公司; 卡尔蔡司显微镜有限责任公司
Priority date: 2021-09-22
Filing date: 2022-07-01
Publication date: 2023-03-30
Also published as: CN113865958A

Abstract

A method for manufacturing a three-dimensional structure. The method comprises: drawing a three-dimensional model of a portion, which needs to be removed and/or deposited from/onto a blank in order to obtain a three-dimensional structure (S101); slicing the three-dimensional model in slicing software, so as to decompose the three-dimensional model into a plurality of slice layers (S102); and importing data of the plurality of slice layers into processing software, and removing and/or depositing the plurality of slice layers from/onto the blank layer by layer, so as to obtain the three-dimensional structure (S103). A three-dimensional model is decomposed into a plurality of slice layers by means of slicing the three-dimensional model, and a three-dimensional structure is then obtained by removing and/or depositing the slice layers layer by layer, such that a precise three-dimensional structure can be manufactured in a simple and reliable manner.

Description

Method for making three-dimensional structures

Cross References to Related Applications

This application claims the priority and rights and interests of the Chinese patent application No. 202111105699.4 submitted on September 22, 2021, and the content disclosed in the above Chinese patent application is cited in its entirety as a part of this application.

technical field

The present application relates to the field of optics and processing technology, in particular, to a method of manufacturing a three-dimensional structure.

Background technique

Focused Ion Beam (FIB) is a device that uses focused ion beams (Ga+, He+, etc.) to act on the sample to achieve etching and deposition processing on the surface of the sample. Because the focused ion beam has a certain energy, when the focused ion beam bombards the sample surface, the atoms on the sample surface obtain energy and escape from the surface, thereby realizing the function of etching the sample surface. When etching, because the ion beam is focused, the etching process can be carried out in the designated area according to the designed pattern. When the ion beam acts on the surface of the sample and there are different chemical precursors, the particles (secondary electrons) excited by the ion beam react with these precursors to realize different materials (such as Pt, C, SiO ₂ , W, Au etc.) graphics deposition.

The current common focused ion beam equipment is a dual-beam structure, and the two energy beams form a certain angle. In addition, there is a focused ion beam device with a three-beam structure (for example, three beams of He, Ne, and Ga ions).

Focused ion beam is a processing method that acts vertically on the surface of the sample, and the sidewalls of the etched or deposited shape can only be perpendicular to the surface of the sample. If you want to process a three-dimensional structure with non-vertical sidewalls, it is more difficult to realize the focused ion beam, but in fact, most of the three-dimensional structures have non-vertical sidewalls. Because for the processing of three-dimensional structure, it is difficult to realize the focused ion beam.

Contents of the invention

The starting point of the present application is to provide a method for manufacturing a three-dimensional structure, so as to solve the above-mentioned problems in the prior art.

Embodiments of the present application provide a method of manufacturing a three-dimensional structure, the method comprising:

drawing a 3D model of the parts that need to be removed and/or deposited from the billet in order to obtain the 3D structure,

Slicing the 3D model in slicing software, thereby decomposing the 3D model into multiple slice layers,

The data of the multiple slice layers are imported into processing software, and the multiple slice layers are removed and/or deposited layer by layer on the blank, so as to obtain the three-dimensional structure.

Optionally, the plurality of sliced layers are removed and/or deposited layer by layer on the blank using an energy beam.

Optionally, the energy beam includes at least one of the following: laser beam, electron beam, plasma and ion beam.

Optionally, the number of slice layers can be adjusted.

Optionally, the spacing between every two adjacent slice layers can be adjusted. That is to say, the interval between two adjacent slice layers can be flexibly controlled as required. If the intervals are set to be the same, the advantage is that the processing parameters can be set in batches in the processing software. If the intervals are set to be different, the advantage is that the number of repeated graphics of the same size can be reduced, and at the same time, the processing software can set the processing parameters of the graphics separately. In addition, for a drawn 3D model, a part of slice layers of the 3D model can be selected for processing according to actual needs. Therefore, for the same three-dimensional model, different three-dimensional structures may be obtained after processing different slice layers.

Optionally, the data of the slicing layer is exported from the slicing software in the form of a vector file and imported into the processing software. The advantage of using vector files is that it occupies less storage space, has good controllability during processing, and is very suitable for processing complex shapes.

Optionally, the three-dimensional structure is a hemispherical groove, then the method specifically includes:

Draw a 3D model of the hemispherical groove,

Slicing in a slicing software along a direction perpendicular to the axis of symmetry of the three-dimensional model, thereby decomposing the three-dimensional model into a plurality of circular slice layers with different diameters,

The plurality of circular sliced layers are removed layer by layer on the blank by using an energy beam, so as to obtain the hemispherical groove.

Optionally, the three-dimensional structure is a hemisphere formed in a truncated conical groove, then the method specifically includes:

Draw a hemisphere and a truncated cone with the bottom of the hemisphere as a small circle and the distance from the bottom to the apex of the hemisphere as a height, the part of the truncated cone that does not overlap with the hemisphere A 3D model of the part to be removed from the billet,

In the slicing software, slice along the direction perpendicular to the axis of symmetry of the three-dimensional model, thereby decomposing the three-dimensional model into a plurality of concentric ring-shaped slice layers with different inner diameters and outer diameters, wherein each slice The outer diameter of the layer gradually decreases from the maximum value, and the inner diameter of each slice layer gradually increases from basically 0, until the outer diameter and inner diameter of the last slice layer are basically equal to the diameter of the hemisphere,

The plurality of concentric annular sliced layers are removed layer by layer on the blank by means of an energy beam, thereby obtaining hemispheres formed in frustoconical grooves.

Embodiments of the present application also provide a hemispherical groove manufactured by the above-mentioned method according to the present application.

Embodiments of the present application also provide a hemisphere formed in a frustoconical groove, the hemisphere formed in the truncated conical groove being manufactured by the above method according to the present application.

Embodiments of the present application also provide a cone, which is manufactured by the above-mentioned method according to the present application.

The embodiment of the present application also provides an irregularly shaped truncated truncated column, which is manufactured by the above-mentioned method according to the present application.

Embodiments of the present application also provide a spherical cap structure formed in a hemispherical groove, the spherical cap structure formed in the hemispherical groove is manufactured by the above method according to the present application.

Embodiments of the present application also provide a microlens, which is manufactured by the method according to the present application, and the specific form of the microlens includes at least one of the following: a hemispherical groove, a truncated cone Hemispheres in shaped grooves, cones, irregularly shaped frustum columns, spherical cap structures formed in hemispherical grooves, and two one or more hemispheres.

Embodiments of the present application also provide a method of manufacturing a spherical cap structure formed in a hemispherical groove, the method comprising:

In the slicing software, slice along the direction perpendicular to the axis of symmetry of the three-dimensional model, thereby decomposing the three-dimensional model into a plurality of concentric ring-shaped slice layers with different inner diameters and outer diameters, wherein each slice layer The outer diameter gradually decreases from the maximum value, and the inner diameter of each slice layer gradually increases from basically 0 until the outer diameter and inner diameter of the last slice layer are basically equal to the diameter of the bottom surface of the spherical cap. The plurality of concentric annular slice layers are removed layer by layer from the blank, so as to obtain the spherical cap structure formed in the hemispherical groove.

Embodiments of the present application also provide two or more hemispheres formed in a cylindrical groove, a frusto-conical groove or a hemispherical groove, different hemispheres have the same radius or different radii , the two or more hemispheres formed in the cylindrical groove, the frusto-conical groove or the hemispherical groove are manufactured by the above method according to the present application.

The method for manufacturing a three-dimensional structure according to the embodiments of the present application has at least the following advantages:

In this application, the 3D model is decomposed into multiple slice layers by slicing the 3D model, and the 3D structure is obtained by removing and/or depositing the slice layers layer by layer, so that precise 3D structures can be manufactured in a simple and reliable manner .

Description of drawings

Further details and advantages of the present application will become apparent from the detailed description provided hereinafter. It should be understood that the following drawings are only schematic and not drawn to scale, and thus should not be considered as limiting the application. The following will be described in detail with reference to the accompanying drawings, wherein:

FIG. 1 shows a flowchart of a method for manufacturing a three-dimensional structure according to a specific embodiment of the present application.

FIG. 2A shows a perspective view of a three-dimensional model of a hemispherical groove drawn by drawing software according to another specific embodiment of the present application.

Fig. 2B shows a cross-sectional view along the axis of symmetry of a three-dimensional model of a hemispherical groove according to another embodiment of the present application.

FIG. 2C shows a schematic diagram of slicing a three-dimensional model of a hemispherical groove according to another specific embodiment of the present application.

FIG. 2D shows a hemispherical groove manufactured by the method of the present application according to another embodiment of the present application.

FIG. 3A shows a perspective view of a three-dimensional model of a hemisphere formed in a frustoconical groove drawn by drawing software according to yet another embodiment of the present application.

Fig. 3B shows a cross-sectional view of a three-dimensional model according to yet another specific embodiment of the present application, and the parts to be removed are shown with hatching.

Fig. 3C shows a schematic diagram of slicing a three-dimensional model according to yet another specific embodiment of the present application.

FIG. 3D shows the variation trend of each concentric circular slice layer according to yet another specific embodiment of the present application.

FIG. 4 shows a perspective view of a three-dimensional model of a cone manufactured by deposition with the aid of the method of the present application.

FIG. 5A shows a perspective view of a three-dimensional model of an irregular-shaped frusto-conical column manufactured by deposition by means of the method of the present application.

FIG. 5B shows a cross-sectional view of a three-dimensional model of an irregular-shaped frusto-conical column manufactured by deposition by means of the method of the present application.

Fig. 6 shows a cross-sectional view of a three-dimensional model of a spherical cap structure in a hemispherical groove manufactured by means of the method of the present application.

Fig. 7 shows a cross-sectional view of a three-dimensional model of two hemispheres in a cylindrical groove manufactured by means of the method of the present application, wherein the two hemispheres have the same radius.

Fig. 8 shows a cross-sectional view of a three-dimensional model of two hemispheres in a cylindrical groove manufactured by means of the method of the present application, wherein the two hemispheres have different radii.

Detailed ways

Embodiments of the present application are described below with reference to the drawings. In the following description, numerous specific details are set forth in order to enable those skilled in the art to more fully understand and practice the present application. It will be apparent, however, to one skilled in the art that implementations of the present application may be without some of these specific details. Furthermore, it should be understood that the application is not limited to the particular embodiments described. Rather, it is contemplated that the application can be practiced with any combination of the features and elements described below, regardless of whether they relate to different embodiments. Accordingly, the following aspects, features, embodiments and advantages are by way of illustration only and should not be considered elements or limitations of the claims unless explicitly stated in the claims.

Referring now to FIG. 1 , it shows a flowchart of a method for manufacturing a three-dimensional structure according to a specific embodiment of the present application. As shown in Figure 1, the method includes:

Step S101, drawing a three-dimensional model of the part that needs to be removed and/or deposited from the blank in order to obtain a three-dimensional structure.

The 3D model can be drawn using existing drawing software, such as simulation software such as AutoCAD, SolidWork, 3D Fusion, CST, and Zemax. The drawn 3D model can be exported in (.stl) format. For example, if the three-dimensional structure of manufacture is a hemispherical groove, then utilize drawing software to draw the three-dimensional model of the hemispherical groove, Fig. 2 A and 2B have shown respectively the three-dimensional view of the three-dimensional model of the hemispherical groove drawn and along the three-dimensional model A cross-sectional view of the axis of symmetry.

Step S102, slicing the 3D model in slicing software, so as to decompose the 3D model into multiple slice layers.

Still taking the manufacture of hemispherical grooves as an example, as shown in Figure 2C, slice along the direction (i.e. the Z axis in Figure 2C) perpendicular to the symmetry axis of the three-dimensional model of the hemispherical groove in the slicing software, thereby The 3D model is decomposed into slice layers of multiple circles with different diameters. Each slice layer can be approximately considered as a two-dimensional circle. Continuing as shown in FIG. 2C , assuming that the radius of the hemispherical groove is 30, for the convenience of processing, the interval between every two adjacent slice layers can be the same. The interval between every two adjacent slice layers can be set to 0.1, so as to obtain 301 layers of slices, and the coordinates of each slice layer on the Z axis are 0, -0.1, -0.2, -0.3, -0.4, ... -29.8, -29.9, -30. The number of slice layers (that is, the interval between adjacent slice layers) can also be adjusted. The more slice layers, the more precise the hemispherical grooves processed.

Step S103, import the data of multiple slice layers into the processing software, and remove and/or deposit multiple slice layers layer by layer on the blank, so as to obtain a three-dimensional structure.

The slice layer data obtained in the slicing software is preferably exported from the slicing software and imported into the processing software in a format (eg, .ely format) that can be directly opened by the processing software (eg, SmartFIB). Preferably, the data of the slicing layer is exported from the slicing software in the form of a vector file and imported into the processing software. Afterwards, using an energy beam (for example, a focused ion beam or a laser beam) to remove multiple circular slice layers layer by layer on the blank (for example, a square solid blank), thereby obtaining a hemispherical groove, as shown in Figure 2D schematically shows a hemispherical groove fabricated by the method of the present application.

Using the principles of the method of the present application, three-dimensional structures of arbitrary shapes can be fabricated, not limited to the above-mentioned hemispherical grooves. For example, using the method of the present application, it is also possible to manufacture hemispheres formed in frusto-conical grooves. First, draw a hemisphere and a truncated cone with the bottom surface of the hemisphere as a small circle and the radius of the hemisphere as the height. The part of the truncated cone that does not overlap with the hemisphere is the three-dimensional part that needs to be removed from the blank Model. 3A and 3B show a perspective view and a cross-sectional view along the axis of symmetry of the three-dimensional model, respectively, of a drawn three-dimensional model of a hemisphere formed in a frustoconical groove. In FIG. 3B, the parts that need to be removed are shown in hatching. Next, as shown in FIG. 3C , slicing is carried out in a slicing software along a direction perpendicular to the symmetry axis of the 3D model, thereby decomposing the 3D model into multiple concentric ring-shaped slice layers with different inner diameters and outer diameters. FIG. 3D shows the variation trend of the sliced layers of each concentric ring. As shown in Figure 3D, the outer diameter D1 of each slice layer gradually decreases from the maximum value, and the inner diameter D2 of each slice layer gradually increases from substantially zero, until the outer diameter D1 and inner diameter D2 of the last slice layer are both Basically equal to the diameter of a hemisphere. Finally, using an energy beam (for example, a focused ion beam or a laser beam) on the blank (for example, a square solid blank) to remove a plurality of concentric circular slice layers layer by layer, thereby obtaining a truncated conical A hemisphere in a groove.

In the above specific implementation manners in this application, the 3D model is decomposed into multiple slice layers by slicing the 3D model, and the 3D structure is obtained by removing the slice layers layer by layer, so that accurate three-dimensional structure.

The hemispherical grooves and the hemispheres formed in the frustoconical grooves manufactured by the method of the present application can be used to process micron-scale microlenses in the field of optoelectronics, and can also be used as microdevices in the field of electronic semiconductors.

In the field of photonics research, how to improve the light signal detection efficiency of luminescent materials is a very important issue. By processing microscopic curved surface structures (ie, microlenses) on the material, the light signal collection efficiency at the processed position can be improved. This method can directly convert the theoretically obtained three-dimensional model into a vector file that can be directly processed to obtain precise microlenses.

When the material has single-photon emission properties (such as negatively charged nitrogen vacancies in diamond), it can be applied to quantum storage, magnetic sensors, single-photon emission sources, and more. Microlenses can enhance the detection efficiency of single photons and improve their applications in these fields.

Processing microlenses in silicon waveguide materials can enhance the edge coupling effect of silicon optical integrated circuits, thereby improving the utilization efficiency of silicon waveguides.

In addition, the applicant wishes to point out that the method of manufacturing three-dimensional structures involved in this application is not limited to material removal processing, but can also be used for three-dimensional structure processing in additive manufacturing (ie, deposition of different materials). For example, using laser beams, electron beams, plasma and/or ion beams as heat sources, materials are heated and bonded to create three-dimensional structures. Material removal and additive manufacturing can also be used together to create complex three-dimensional structures. Therefore, the method for manufacturing a three-dimensional structure of the present application can not only manufacture three-dimensional structures symmetrical to the central axis, but also various asymmetric three-dimensional structures and complex three-dimensional structures can be processed. In addition, by adjusting the angle between the sample surface and the energy beam, combined with slicing or deposition techniques, different three-dimensional structures can also be obtained. For example, in the process of processing, multiple different 3D models can be drawn and sliced, and the processing of complex 3D structures can be realized through the combination of 3D models. It is also possible to draw multiple identical 3D models, and process multiple identical 3D structures at different positions of the same sample, thereby realizing array processing of 3D structures.

Below are several examples of three-dimensional structures manufactured according to the method of the present application:

Figure 4 shows a perspective view of a three-dimensional model of a cone manufactured by means of the method of the present application. The cone can be produced by material removal or deposition.

5A and 5B show a three-dimensional model of an irregularly shaped frustoconical column fabricated by means of the method of the present application. Wherein, FIG. 5A shows a perspective view of a three-dimensional model of an irregular-shaped frustum column, and FIG. 5B shows a cross-sectional view of a three-dimensional model of an irregular-shaped frustum column. The irregularly shaped frustum can be fabricated by material removal or deposition.

Fig. 6 shows a cross-sectional view of a three-dimensional model of a spherical cap structure in a hemispherical groove manufactured by means of the method of the present application. In order to manufacture the three-dimensional structure, for example, the hemispherical groove can be fabricated by material removal using the method described in FIGS. 2A-2D of the present application, and then the spherical cap structure can be deposited in the hemispherical groove by additive manufacturing. Alternatively, the method of the present application can also be used to manufacture the spherical cap structure in the hemispherical groove in the following way: first, slice along the direction perpendicular to the axis of symmetry of the three-dimensional model in the slice software, so that the three-dimensional The model is decomposed into a plurality of concentric annular slice layers with different inner diameters and outer diameters, wherein the outer diameter of each slice layer gradually decreases from the maximum value, and the inner diameter of each slice layer gradually increases from substantially zero. large until the outer diameter and inner diameter of the last sliced layer are substantially equal to the diameter of the bottom surface of the spherical cap, and then, the plurality of concentric annular sliced layers are removed layer by layer on the blank by using an energy beam, thereby obtaining A spherical cap structure formed in a hemispherical groove.

Fig. 7 shows a cross-sectional view of a three-dimensional model of two hemispheres in a cylindrical recess made by means of the method of the present application. where both hemispheres have the same radius. In order to manufacture the three-dimensional structure, it is possible, for example, to first manufacture a cylindrical groove by material removal using the method of the present application, and then deposit two hemispheres with the same radius in the cylindrical groove by additive manufacturing.

Fig. 8 shows a cross-sectional view of a three-dimensional model of two hemispheres in a cylindrical groove manufactured by means of the method of the present application. Here, the two hemispheres have different radii. In order to manufacture the three-dimensional structure, it is possible, for example, to first manufacture a cylindrical groove by material removal using the method of the present application, and then deposit two hemispheres with different radii in the cylindrical groove by additive manufacturing.

It should be noted that the above description is only an example, rather than limiting the application. In other embodiments of the present application, the method may have more, fewer or different steps, and the order, inclusion and function of the steps may be different from those described and illustrated. For example, often multiple steps can be combined into a single step, and a single step can be split into multiple steps. For those of ordinary skill in the art, on the premise of not paying creative work, the sequential changes of each step are also within the protection scope of the present application.

The essence of the technical solution of this application or the part that contributes to the prior art, or all or part of the technical solution can be embodied in the form of software products. The computer software products are stored in a storage medium, including several instructions. So that a computer device (which may be a personal computer, a server, or a network device, etc.) or a processor or a microcontroller executes all or part of the steps of the methods described in various embodiments of the present application.

Those of ordinary skill in the art can understand that all or part of the steps for implementing the above method embodiments can be completed by program instructions and related hardware. The aforementioned program can be stored in a computer-readable storage medium. When the program is executed, it executes the steps including the above-mentioned method embodiments; and the aforementioned storage medium includes: ROM, RAM, magnetic disk or optical disk and other various media that can store program codes.

Although the present application has been disclosed above with preferred embodiments, the present application is not limited thereto. Any alterations and modifications made by those skilled in the art without departing from the spirit and scope of the application should be included in the protection scope of the application, so the protection scope of the application should be defined by the claims. allow.

Claims

A method of manufacturing a three-dimensional structure, characterized in that the method comprises:

drawing a 3D model of the parts that need to be removed and/or deposited from the billet in order to obtain the 3D structure,

Slicing the 3D model in slicing software, thereby decomposing the 3D model into multiple slice layers,

The data of the multiple slice layers are imported into processing software, and the multiple slice layers are removed and/or deposited layer by layer on the blank, so as to obtain the three-dimensional structure.
The method of claim 1 , wherein the plurality of sliced layers are removed and/or deposited layer by layer on the blank with an energy beam.
The method of claim 1, wherein the energy beam comprises at least one of: a laser beam, an electron beam, a plasma, and an ion beam.
The method of claim 1, wherein the number of slice layers is adjustable.
The method according to claim 1, wherein the interval between every two adjacent slice layers can be adjusted.
The method according to claim 1, wherein the data of the slicing layer is exported from the slicing software and imported into the processing software in the form of a vector file.
The method according to any one of claims 1-6, wherein the three-dimensional structure is a hemispherical groove, and the method specifically includes:

Draw a 3D model of the hemispherical groove,

Slicing in a slicing software along a direction perpendicular to the axis of symmetry of the three-dimensional model, thereby decomposing the three-dimensional model into a plurality of circular slice layers with different diameters,

The plurality of circular sliced layers are removed layer by layer on the blank by using an energy beam, so as to obtain the hemispherical groove.
The method according to any one of claims 1-6, wherein the three-dimensional structure is a hemisphere formed in a frustoconical groove, and the method specifically comprises:

Draw a hemisphere and a truncated cone with the bottom of the hemisphere as a small circle and the distance from the bottom to the apex of the hemisphere as a height, the part of the truncated cone that does not overlap with the hemisphere 3D model of the part to be removed from the billet,

In the slicing software, slice along the direction perpendicular to the axis of symmetry of the three-dimensional model, thereby decomposing the three-dimensional model into a plurality of concentric ring-shaped slice layers with different inner diameters and outer diameters, wherein each slice The outer diameter of the layer gradually decreases from the maximum value, and the inner diameter of each slice layer gradually increases from basically 0, until the outer diameter and inner diameter of the last slice layer are basically equal to the diameter of the hemisphere,

The plurality of concentric annular sliced layers are removed layer by layer on the blank by using an energy beam, thereby obtaining hemispheres formed in frustoconical grooves.
A hemispherical groove, characterized in that the hemispherical groove is manufactured by the method according to claim 7.
A hemisphere formed in a truncated conical groove, characterized in that the hemisphere formed in the truncated conical groove is manufactured by the method according to claim 8 .
A cone, characterized in that the cone is manufactured by the method according to any one of claims 1-6.
A truncated truncated column of irregular shape, characterized in that the truncated truncated column of irregular shape is manufactured by the method according to any one of claims 1-6.
A spherical cap structure formed in a hemispherical groove, characterized in that the spherical cap structure formed in the hemispherical groove is manufactured by the method according to any one of claims 1-6.
A method of manufacturing the spherical cap structure formed in the hemispherical groove of claim 13, said method comprising:

In the slicing software, slice along the direction perpendicular to the axis of symmetry of the three-dimensional model, thereby decomposing the three-dimensional model into a plurality of concentric ring-shaped slice layers with different inner diameters and outer diameters, wherein each slice layer The outer diameter gradually decreases from the maximum value, and the inner diameter of each slice layer gradually increases from basically 0 until the outer diameter and inner diameter of the last slice layer are basically equal to the diameter of the bottom surface of the spherical cap. The plurality of concentric annular slice layers are removed layer by layer from the blank, so as to obtain a spherical cap structure formed in the hemispherical groove.
A kind of two or more hemispheres formed in a cylindrical groove, a truncated conical groove or a hemispherical groove, different hemispheres have the same radius or different radii, it is characterized in that the forming Two or more hemispheres in a cylindrical groove, a frusto-conical groove or a hemispherical groove are produced by the method according to any one of claims 1-6.
A microlens, characterized in that the microlens is manufactured by the method according to any one of claims 1-6, and the specific form of the microlens includes at least one of the following: hemispherical grooves, Hemispheres formed in frustoconical grooves, cones, irregularly shaped frustums, spherical cap structures formed in hemispherical grooves and structures formed in cylindrical grooves, frustoconical grooves or hemispherical Two or more hemispheres in a groove.