JP2005125439A - Grinding method of gems - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a grinding method of gems for contributing to the realization of numerically controlled grinding of a cut surface, by preventing reduction in work accuracy by partial reduction, by moving the gem so that the partial reduction is not caused in a grinding wheel. <P>SOLUTION: This working method is performed by using a numerical control machine tool having a grinding wheel rotary device 20 having a grinding wheel spindle for rotating a grinding wheel 22 in a horizontal plane, a table 14 moving in the X axis direction on a bed 12, a column 15 moving in the Z axis direction on the table 14, a saddle 16 moving in the vertical Y axis direction along a guide of the column 15, and a work holding shaft 18 having an indexing means for indexing the cut surface of the gems 60 held by the chuck part 30 and installed on the saddle 16 via a revolving shaft. The working method performs grinding at a grinding wheel rotating speed and a feed speed such as the whole grinding wheel surface touches a work 60, until the work 60 reciprocates once by crossing a grinding wheel width, by feeding the work 60 in the radial direction of the grinding wheel 22, by keeping a state of contacting the cut surface of the work 60 with a grinding wheel surface of the grinding wheel 22, while rotating the grinding wheel 22. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a jewelry grinding method, and more particularly, to a jewelry grinding method in which a cutting surface is ground by pressing the jewelry against a grinding wheel using an NC machine tool.

  Gemstones such as diamond, ruby, and sapphire are finished from gemstones through various processing steps to gems with cut structures. The beauty of jewels can be said to depend on the cut structure, and the value of the jewels is enhanced by the precise processing.

  For example, when diamond is described as a representative example of gemstones, diamond is a single crystal of carbon belonging to the equiaxed system. The rough diamonds are mostly produced in a deformed or deformed form, and the rough diamonds themselves are just crystals that are dull and rarely shine. However, when a rough surface is cut by grinding or polishing the rough, light incident from the cut surface is reflected to produce a beautiful glossy shine. The value of diamond as a gemstone is said to have been created only by the establishment of processing technology.

  Various cuts and trials have been carried out on the cut structure that maximizes the brightness of the diamond, and since the mathematician Marcel Turkey Fusky mathematically proved the ideally cut in 1919 that reflects light to the highest degree, The diamond is processed into a cut structure (hereinafter referred to as a brilliant cut) in which the angle and ratio of each part are defined in accordance with this ideal cut.

  FIG. 8 shows a brilliant cut of diamond. Each part of the brilliant cut is given the following name. In other words, it is roughly divided into an upper crown 1 and a lower pavilion 2, and the periphery of the boundary between the crown 1 and the pavilion 2 is called a girdle 3. The ceiling surface of the crown 1 is called a table 4, the slope of the crown 1 is called a bezel 5, and the apex of the pavilion 2 is called a curette 6.

  Such a brilliant-cut diamond has a 58-hedron cut, and the dimensional ratio of each part such as the crown 1, the pavilion 2, and the table 4 is strictly defined. Whether or not to maximize the brightness of the diamond depends on the processing technology to make the diamond precisely brilliant cut as designed. If the symmetry of the cut surface of the brilliant cut is slightly out of order, Leakage will decrease and the shine will decrease, and the commercial value of jewelry will be greatly reduced.

While diamond values are pursued as gemstones, diamonds are widely used in tools because of their unparalleled hardness. In the field of industrial diamond, gem value is not a problem, and processing is easy. Various machine tools for polishing the R portion of diamond tools and cemented carbide tools have been invented (for example, patents). Reference 1).
JP-A-2-224961

  However, in the field of dealing with diamonds that pursue value as gems, unlike diamonds as industrial products, labor concentration that the diamond processing industry has historically been established in certain parts of the world (Israel, India, etc.) In addition to the special circumstances of a traditional industry, the idea that processing by highly skilled craftsmen produces high-value gems has penetrated, so efficient and highly accurate brilliant cuts as designed At present, NC machine tools for machining have not been developed.

  The first problem in realizing NC is that if it is a professional craftsman with advanced technology, it is difficult to process while pressing the diamond against the rotating wheel flexibly according to intuition and experience. It is a typical part. In an NC machine tool, the advantage of moving exactly as instructed by a program is the disadvantage of moving only as instructed. For this reason, for example, even if the diamond is moved during processing, it is very difficult to prevent the diamond from being reduced.

  Accordingly, an object of the present invention is to solve the problems of the prior art, move the jewel so that the grinding stone does not decrease, prevent machining accuracy from being reduced, and grind the cut surface. An object of the present invention is to provide a method for grinding a jewelry that contributes to the improvement of the process.

  In order to achieve the above object, the present invention provides a disc-shaped grinding wheel, a grinding wheel rotating device having a grinding wheel shaft that rotates the grinding wheel in a horizontal plane, a table that moves on the bed in the X-axis direction, A column that moves in the Z-axis direction on the table, a saddle that moves in the vertical Y-axis direction along the guide of the column, and indexing means for indexing a cut surface of jewelry that is a work held by the chuck portion And a workpiece holding shaft attached to the saddle via a turning shaft, and a grinding method using a numerically controlled machine tool, the cutting surface of the workpiece while rotating the grinding wheel Rotating the grinding wheel so that the entire grinding wheel surface hits the workpiece while the workpiece moves in the radial direction of the grinding wheel while the workpiece makes one reciprocation across the grinding wheel width. Number and feed Is characterized in that the grinding in degrees.

  As is clear from the above description, according to the present invention, it is possible to move the jewelry so that the grinding stone is not reduced, and to prevent a reduction in processing accuracy due to the reduction, and to grind the cut surface of the jewelry. It is possible to contribute to the realization of machining NC, and it is possible to perform machining efficiently and continuously as designed by numerical control replacing the skill of skilled craftsmen.

Hereinafter, an embodiment of a jewelry grinding method according to the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a side view of a processing apparatus used for carrying out the jewelry grinding method according to the present embodiment, and FIG. 2 is a plan view of the processing apparatus. 1 and 2, reference numeral 10 indicates the entire processing apparatus. Reference numeral 12 indicates a bed. The processing apparatus 10 includes a table 14, a column 15, a saddle 16, a work holding shaft 18, a grindstone rotating device 20, and the like.

A grindstone rotating device 20 and a table base 21 are installed on the upper surface of the bed 12. The grinding wheel rotating device 20 includes a grinding wheel 22. In this processing apparatus 10, the direction toward or away from the grinding wheel 22 with respect to the grinding wheel 22 is the Z-axis direction, the direction orthogonal to the Z-axis direction and parallel to the grinding wheel 22. The direction to do is the X axis, and the vertical direction is the Y axis.

  X-axis guides 23a and 23b extending in parallel with the X-axis direction are laid on the upper surface of the table base 21, and the table 14 can be guided and moved by the X-axis guides 23a and 23b. On the table 14, Z-axis guides 24a and 24b extending in parallel with the Z-axis direction are laid, and the column 15 installed on the table 14 moves along the Z-axis guides 24a and 24b. It has become. A saddle 16 is attached to the front of the column 15 via Y-axis guides 25a and 25b so as to be movable in the vertical direction. Reference numeral 26 indicates an X-axis servo motor that drives a ball screw mechanism that feeds the table 14, reference numeral 27 indicates a Z-axis servo motor that drives a ball screw mechanism that feeds the column 15, and reference numeral 28 indicates a saddle 16 This is a Y-axis servo motor that drives a ball screw mechanism that feeds.

  A workpiece holding shaft 18 having a chuck portion 30 that holds diamond as a workpiece to be ground is attached to the saddle 16. Next, the workpiece holding shaft 18 will be described.

FIG. 3 is a view showing a side surface of the work holding shaft 18, and FIG. 4 is a view showing a cross section of the turning shaft portion of the work holding shaft 18.
A diamond is denoted by reference numeral 60 as a workpiece to be ground. The diamond 60 is detachably held at the tip of the chuck portion 30. The chuck portion 30 is coaxially connected to a Kirbic coupling 32 (registered trademark of US Gleason Co., Ltd.) constituting indexing means for indexing the cut surface of the diamond 60. As shown in FIG. 4, this Kirbic coupling 32 can be determined by dividing 360 ° into 32 parts. When the air cylinder 33 is supplied with air and the piston 33a is lowered, the carbide coupling 32 is released from the clamp so that the chuck portion 30 and the lower half of the carbide coupling 32 can be manually indexed every 1/32 rounds. It can be done. The diamond 60 is firmly held at the tip of the chuck portion 30. The diamond 60 is held by a press-fitting method.

  In FIG. 4, reference numeral 34 indicates a turning axis of the work holding shaft 18, and this turning axis 34 is parallel to the direction of the X axis. A bracket 35 is attached to the saddle 16, and a support block 36 is fixed to the bracket 35. A bearing 37 is attached to the inside of the support block 36, and the pivot shaft 34 is rotatably supported by the bearing 37. A U-shaped joint member 38 is attached to the pivot shaft 34, and the upper end portion of the cylinder 65 is fixed to the joint member 38. Therefore, the work holding shaft 18 constituted by the joint member 38, the air cylinder 33, the carbide coupling 32, and the chuck portion 30 can be swung in the YZ plane around the swivel shaft 34 as a unit. . The control axis of this turning motion is the A axis.

  In FIG. 4, reference numeral 40 indicates an A-axis servomotor connected to the turning shaft 34. The main body of the A-axis servomotor 40 incorporating this rotary encoder is attached to a frame 41 fixed to the support block 36, and the rotating shaft 40 a of the A-axis servomotor 40 is connected to the pivot shaft 34 via a joint 39. It is connected with.

Next, the grindstone rotating device 20 will be described with reference to FIGS. 1 and 2.
The disc-shaped grinding wheel 22 is connected to a grinding wheel shaft 42 coaxially. When the grinding wheel shaft 42 rotates, the grinding wheel 22 can rotate in a horizontal plane (XZ plane). As shown in FIG. 2, an annular grindstone 43 is fixed to the upper surface of the grinding wheel 22. This grindstone 43 is mixed with diamond powder.

  In FIG. 1, reference numeral 50 indicates a numerical controller. In this embodiment, the machining apparatus 10 is configured as a numerically controlled machine tool for four-axis control of the X axis, Y axis, Z axis, and A axis.

  The numerical control device 50 sends a command calculated by analyzing a processing program relating to jewelry grinding to the servo drive unit 52. The servo drive unit 52, based on the command, sends an X-axis servo motor 26, a Z-axis servo. The motor 27, the Y-axis servo motor 28, and the A-axis servo motor 40 are controlled. The control loop for feedback control of the position and the like is not shown.

  Further, the grindstone shaft 42 of the grindstone rotating device 20 is driven by a grindstone motor 44 provided inside the case 41. The grindstone motor 44 rotates at a rotational speed commanded from the numerical controller 50.

  Next, a processing method performed using the above-described grinding apparatus will be described by taking an example of grinding a cut surface of diamond.

  In this embodiment, in order to perform grinding by numerical control by making good use of the structural features of the brilliant cut of diamond, first, each cut surface to be ground of the brilliant cut of diamond will be described.

  The diamond 60 to be ground is the brilliant cut diamond of 58 facet cut shown in FIG. FIG. 9 is a plan view of the brilliant cut as seen from the crown 1, and FIG. 10 is a plan view of the brilliant cut of diamond as seen from the pavilion 2.

  In the brilliant cut of diamond, the axis passing through the curette 6 from the center of the table 4 is a rotationally symmetric axis 100. The crown 1 has 32 cut surfaces, the pavilion 2 has 24 cut surfaces, the table 4 has 1 cut surface, and the curette 6 has 1 cut surface, for a total of 58 surfaces.

  As shown in FIG. 9, the cut surface of the brilliant-cut crown 1 is made up of four types of cut surfaces: a cut surface a, a cut surface b, a cut surface c, and a cut surface d, as distinguished from its shape and arrangement. I understand that. Among them, the cut surfaces a are arranged on the outer periphery of the crown 1 and there are eight planes symmetrically by 45 ° with respect to the rotational symmetry axis 100. There are eight cut surfaces b symmetrically with respect to the rotational symmetry axis 100 by 45 ° so as to be adjacent to the cut surface a. The cut surface c has eight surfaces of 45 ° with respect to the rotational symmetry axis 100 between the cut surface a and the cut surface b. The cut surface d has eight surfaces of 45 ° with respect to the rotational symmetry axis 100 between the adjacent cut surfaces c. Therefore, the cut surface of the brilliant-cut crown 1 can be determined by turning the rotational symmetry axis 100 by 1/8 for each type of the cut surfaces a to d.

  Next, in FIG. 10, regarding the cut surface of the brilliant-cut pavilion 2, the pavilion 2 includes three types of cut surfaces e, g, f, and g. Each of the eight planes is symmetric about 45 ° with respect to the rotational symmetry axis 100. Therefore, the cut surface of the pavilion 2 can also be determined by rotating the rotational symmetry axis 100 by 1/8 for each type.

  First, as shown in FIG. 3, the diamond 60 that is a workpiece is held at the tip of the chuck portion 30 so that the rotational symmetry axis 100 coincides with the center line of the Kirvic coupling 32.

  In FIG. 5, when the work holding shaft 18 turns, this causes a specific cut surface of the diamond 60 to be ground to be parallel to the surface of the grindstone 43 on the grinding wheel 22. Further, the table 14 moves in the X axis, and the column 15 moves in the Z axis on the table 14, whereby the position of the diamond 60 is positioned at a predetermined position on the grindstone 43.

  Here, in the grinding of the pavilion 2 of the diamond 60 (the same applies to each of the cut surfaces a to d of the crown 1), in FIG. 6, when the cut surface e is ground and when the cut surface f is ground, the cutting is performed. The turning angle θ of the work holding shaft 18 when the cut surfaces e to g are made parallel to the surface of the grindstone 43 differs depending on whether the surface g is ground (in this specification, according to the diamond cut surface). Matching the turning angle of the workpiece holding shaft 18 is defined as setting the cut surface angle).

  Therefore, if the turning angle θ of the workpiece holding shaft 18 changes depending on which of the cut surfaces e to g is to be ground, the position of the diamond 60 on the Z axis naturally changes. Based on the design data of 60 brilliant cuts, the turning angle θ and the position on the Z-axis are calculated for each cut surface.

Next, the position where the diamond 60 is ground on the X axis, the Y axis, and the Z axis in the processing apparatus 10 will be described.
Here, FIG. 7 shows an example of a grinding position on the grinding wheel 43 of the grinding wheel 22. In this embodiment, eight positions from P1 to P8 that are positioned symmetrically by 45 ° are preliminarily ground to measure the grinding resistance, and among these, positions that can be ground while being fed in a direction with a small grinding resistance are measured. Check it. Therefore, for example, when grinding is performed while feeding in the X-axis direction at the grinding position P1, it is assumed that the grinding resistance is small.

  In addition to the position for grinding the diamond 60 as described above, the data necessary for numerical control of the grinding of the diamond 60 are mainly the cutting amount Δy in the Y-axis direction, and the diamond 60 in the width direction on the surface of the grindstone 43. A machining program is created using numerical data such as the amount of movement in the X-axis direction to be reciprocated, the feed speed thereof, and the rotational speed of the grinding wheel 22, and this machining program is executed by the numerical controller 50 as follows. The grinding of the pavilion 2 of the diamond 60 can be performed semi-automatically.

  In this embodiment, in each of the cut surfaces e to g of the pavilion 2 of the diamond 60, all the eight cut surfaces e are ground first, and then the cut surface f and the cut surface g are advanced in this order.

  First, when the machining program is executed, controlled by the numerical controller 50, the A-axis servo motor 40 is first activated, and the workpiece holding shaft 18 turns until the turning angle θ matches the command value. Settings are made. Thereafter, this turning angle is maintained. Further, the table 14, the column 15, and the saddle 16 are moved, and as described above, the diamond 60 at the tip of the work holding shaft 18 is positioned at the grinding standby position at the center of the grindstone 43 shown in FIG. Further, the grindstone rotating device 20 is also activated at the same time, and the grindstone wheel 22 starts rotating at a predetermined number of revolutions.

  Next, the saddle 16 is moved down by the Y-axis movement to a position where the cut surface e of the diamond 60 held by the chuck portion 30 of the workpiece holding shaft 18 is ground by the grindstone 43. Then, feeding by the following X-axis movement is performed.

  In FIG. 7, the grinding wheel 22 is rotating during the grinding process, and the diamond 60 is positioned so as to cross the width of the grinding wheel 43 in the X-axis direction, that is, in the radial direction of the grinding wheel 22 on the machine coordinate system. ) To and from position (i). Then, while the diamond 60 reciprocates once, grinding is performed by instructing the rotational speed of the grinding wheel 22 and the feed speed of the diamond 60 by the numerical controller 50 so that the entire surface of the grindstone 43 hits the diamond 60. Such rotation speed and feed speed vary depending on the surface of the grindstone 43 and the area of the cut surface of the diamond 60. Therefore, trial grinding is performed in advance to optimize the rotation speed and feed speed. Find the value.

  Thereafter, the diamond 60 reciprocates in the X-axis direction so that the cut surface e contacts the surface of the grindstone 43 so as to cross the grindstone 43 in the width direction, and the entire surface of the grindstone 43 hits the diamond 60 during one reciprocation. become. Then, the cut surface e of the first surface can be ground by lowering the saddle 16 by a minute cutting amount Δy while continuing this reciprocation.

  Since the feed in the X-axis direction as described above corresponds to a feed direction with a small grinding resistance, the grinding efficiency can be increased. In addition, since the diamond 60 comes into contact with the grinding wheel 43 of the grinding wheel 22 uniformly, it is possible to prevent a decrease in accuracy due to the reduction of the piece and the reduction of the piece.

  Next, as shown in FIG. 7, when trial grinding at the grinding position P4 reveals that this is the direction in which the grinding resistance is small, a position (j ') To the outside position (i'), and in the same manner, the numerical control device 50 causes the grinding wheel 22 to move so that the entire surface of the grindstone 43 hits the diamond 60 while the diamond 60 reciprocates once. Grinding may be performed by instructing the rotation speed and the feed rate of the diamond 60.

  When the grinding of the cut surface e of the first surface is thus completed, the workpiece holding shaft 18 rises to the standby position together with the saddle 16, and the diamond 60 escapes from the grindstone 43.

  After that, when air is supplied to the air cylinder 33 of the Carbic coupling 32 and the chuck portion 30 is manually turned by 1/8 rotation, the surface of the grindstone 43 is the next cut surface e after the ground surface. And the next cut surface can be indexed. Then, the air is turned off to fix the Kirvic coupling 32. Thereafter, the same operation as the first cut surface is repeated for all eight cut surfaces e.

  When the grinding of all eight cut surfaces e of the diamond 60 is completed in this way, the workpiece holding shaft 18 is raised to the standby position together with the saddle 16 again. Then, the A-axis servomotor 40 is controlled based on the turning angle command corresponding to the cut surface f of the pavilion 2, and the workpiece holding shaft 18 is set so that the first surface of the cut surface f is parallel to the surface of the grindstone 22. Turns. Hereinafter, as in the case of the cut surface e, grinding and cut surface indexing may be repeated for all eight cut surfaces f.

  The same applies to the grinding of the remaining cut surface g in the pavilion 2 of the diamond 60, and the description is omitted to avoid repeated description. Further, with respect to each of the cut surfaces a to d of the crown 1 of the diamond 60, the diamond 60 is held in the direction opposite to FIG. 6 so that the crown 1 protrudes from the tip of the chuck portion 30 of the workpiece holding shaft 18. Grinding can be done in exactly the same way.

  In the brilliant cut of the diamond 60, the table 4 has only one cut surface, and this cut surface is perpendicular to the rotational symmetry axis 100. Therefore, if the workpiece holding shaft 18 is fixed perpendicularly to the surface of the grindstone 22 after the grinding of all the cut surfaces of the crown 1 is completed, grinding can be performed without the need for indexing.

  As described above, according to the present embodiment, since the NC of the grinding process can be achieved instead of the skill of a skilled craftsman, the efficiency is continuously determined while accurately determining each cut surface of the brilliant cut of diamond. Good and can be ground precisely as designed.

  As described above, the method for grinding a jewelry according to the present invention has been described with reference to a preferred embodiment. However, the object to which the present invention can be applied is not limited to diamond, but is symmetrical with respect to the rotational symmetry axis of the polyhedron. As long as it has a cut structure with a simple cut surface, it can be applied to various kinds of jewelry such as ruby and sapphire. In addition, the present invention can be performed in the same manner as grinding for polishing jewelry. Furthermore, since the present invention is particularly useful for processing a cut surface that enhances the aesthetic value as a gemstone, the contents of the invention are described as a method for processing a jewelry for the sake of convenience. Of course, it can also be applied to processing. Of course, the present invention can be applied to a fully automatic processing apparatus by automating the indexing means for determining the cut surface of diamond.

The side view of the processing apparatus for enforcing the jewelry grinding method by this invention. The top view of the processing apparatus. The side view which shows the workpiece | work holding shaft with which the same processing apparatus is provided. The partially notched side view which shows the turning axis | shaft part of the workpiece holding shaft. The side view of the state in which the workpiece holding shaft was turned to the machining standby position. Explanatory drawing which shows grinding of the brilliant cut of the diamond by one Embodiment of the grinding method of the jewelry of this invention. The figure which shows the example of the grinding position and feed movement of a diamond with respect to a grinding wheel. Explanatory drawing of brilliant cut of diamond. A plan view of a brilliant diamond cut from the crown. The top view which looked at the brilliant cut of diamond from the direction of the pavilion.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Crown 2 Pavilion 3 Girdle 5 Bezel 6 Curette 12 Bed 14 Table 15 Column 16 Saddle 18 Work holding shaft 20 Grinding wheel rotating device 22 Grinding wheel 26 X-axis servo motor 27 Z-axis servo motor 28 Y-axis servo motor 30 Chuck part 32 Car Big coupling (indexing means)
34 Rotating shaft 40 A-axis servo motor 42 Grinding wheel shaft 60 Workpiece (diamond)
100 rotational symmetry axis

Claims (2)

A disc-shaped grinding wheel, a grinding wheel rotating device having a grinding wheel shaft that rotates the grinding wheel in a horizontal plane, a table that moves on the bed in the X-axis direction, a column that moves on the table in the Z-axis direction, The saddle has a saddle that moves in the vertical Y-axis direction along the guide of the column, and indexing means for indexing a cut surface of jewelry that is a work held by the chuck portion, and is attached to the saddle via a pivot shaft. A grinding method performed using a numerically controlled machine tool provided with a workpiece holding shaft,
While rotating the grinding wheel, keep the cut surface of the workpiece in contact with the grinding wheel surface of the grinding wheel,
Jewel characterized in that the workpiece is fed in the radial direction of the grinding wheel, and is ground at a grinding wheel rotational speed and a feeding speed so that the entire grinding wheel surface hits the workpiece while the workpiece makes one reciprocation across the grinding wheel width. Kind of grinding method.   2. The method for grinding a jewelry according to claim 1, wherein the workpiece is a diamond having a 58-sided structure.

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