HK40003584B - Diamond wire cutting method for crystal boules - Google Patents

Description

Diamond wire cutting method for crystal bar

Technical Field

The invention relates to a method for cutting at least one ingot using a cutting line, in particular a diamond wire, for producing a crystal wafer.

The present invention relates to the field of making crystal elements for watches and jewellery, in particular elements inscribed between two parallel surfaces, such as watch mirrors or the like.

Background

The cutting of the ingot is a complex operation because of the difficulty in maintaining these irregularly shaped raw materials. Their hardness requires cutting with diamond wire. Cutting is an expensive operation and is also extremely sensitive to vibrations and any impurities encountered. Furthermore, it is difficult to make a sheet with perfectly parallel surfaces without scratches or scuff marks.

Patent application DE102004043718a1 in the name of SILTRONIC discloses a method for cutting wafers/chips from crystals or rods of brittle material, such as semiconductor crystals, using two or more workpieces placed on a rotating support provided for a diamond saw with a plurality of parallel lines. The workpiece holder rotates about a central axis and is mounted to an indexing drive to feed the workpiece onto the saw. The total cutting motion results from a combination of reciprocating saw drive and rotational motion of the workpiece holder.

Patent application WO2010/009881 in the name of MEYER bug AG also discloses a multi-wire sawing device with a rotating workpiece holder, and a method for sawing solid substrates, for example for use as wafers in the semiconductor, optoelectronic, optical, ceramic, electrical and permanent magnet motor technology industries.

Disclosure of Invention

The present invention proposes a method of controlling the operation of cutting a boule, allowing to cut a plurality of boules simultaneously, ensuring control of the production costs, in particular in terms of saving diamond wires and cutting time, and ensuring a good finished product.

To this end, the invention relates to a method for cutting at least one ingot.

More specifically, it relates to a method for cutting at least one boule using a diamond cutting wire, wherein the boule axis is determined, the at least one boule having a boule radius is cut perpendicular to this boule axis, the boule is driven around a main axis parallel to the boule axis, and the cutting wire is held in tension and driven along a straight section in a plane perpendicular to the main axis, wherein a temporary column is made, which throughout the cutting operation fixes the at least one boule in position relative to the main axis, and in the cutting operation the boule axis is passed on both sides of the straight section during cutting of the at least one boule inside the temporary column, wherein the temporary column is established on the basis of a sacrificial mandrel which coincides with the main axis by its axis of rotation and has a radius equal to the difference between the eccentricity and the boule radius -forming an axial tube or cylinder, the at least one boule being bonded to the sacrificial mandrel after preparation to form a bonded assembly in such a way that each boule is oriented with its boule axis parallel to the main axis, wherein, after the boules are bonded to the sacrificial mandrel, the bonded assembly is inserted into a housing, the bonded assembly is clad with a coating material in the housing, the coating material is cured to form an overmoulded assembly, characterized in that, after curing of the coating material, the overmoulded assembly is removed from the housing and tempered to obtain the temporary column.

Drawings

Other features and advantages of the present invention will become apparent upon reading the following detailed description and upon reference to the drawings in which:

FIG. 1 shows a schematic perspective view of a bonded assembly comprising a sacrificial mandrel around which a plurality of surface-prepared unprocessed boules are bonded.

Fig. 2 shows a schematic end view of the adhesive assembly of fig. 1.

Fig. 3 shows, in a similar manner to fig. 2, the same adhesive assembly, which is inserted into a housing as a mold, in which it is overmoulded with a coating material.

FIG. 4 shows, in a similar manner to FIG. 3, the overmolded assembly after the overmolding operation in FIG. 3, after it has been removed from the housing and heat stabilized, to form a temporary column to be cut.

Fig. 5 shows, in a similar manner to fig. 4, the operation of cutting the temporary column, in a simplified manner, the movement of the cutting line between the two rollers through the column.

Fig. 6 shows a schematic perspective view of the resulting circular cut at the end of the cutting operation, by cutting away the sacrificial mandrel and any remaining portion of the coating to completely separate it from the remaining temporary column.

Fig. 7 shows a schematic perspective view of the remaining portion of the circular cut after removal of the remaining coating.

Fig. 8 shows a schematic perspective view of the crystal slices left after removal of the remaining sacrificial mandrels and adhesive.

Detailed Description

The invention relates to a method for cutting at least one ingot 1 of the sapphire or ruby ingot type using a cutting wire, in particular a diamond wire, to produce a crystalline slab 10.

More specifically, a boule axis DB is determined, and the at least one boule 1 having a boule radius RB is selected to be cut perpendicular to the axis.

This boule radius RB determines the size of the crystal piece 10 resulting from the cutting operation and, therefore, the size of the product resulting from the crystal piece 10, such as a watch crystal or the like.

The cutting is performed by driving the ingot 1 around a main axis DP parallel to the ingot axis DB. More specifically, the main axis DP is separated from the ingot axis DB by an eccentricity E that is greater than the ingot radius RB.

The cutting wire 2 is kept tensioned and driven along a straight section in a plane perpendicular to the main axis DP, in particular but not exclusively between a soft access position, in which the distance of the cutting wire 2 from the main axis DP has a value equal to the sum of the eccentricity E and the ingot radius RB, and a detached position, in which the distance of the cutting wire 2 from the main axis DP has a value equal to the difference between the eccentricity E and the ingot radius RB.

According to the invention, a temporary column 3 is made which immobilizes the position of the at least one ingot 1 with respect to the main axis DP throughout the cutting operation in which the ingot axis DB is passed on both sides of a straight section in the form of a cutting line 2 during the cutting of the at least one ingot 1 inside the temporary column 3.

In particular, during cutting using the diamond wire 2, the temporary column 3 rotates. More specifically, the rotation speed thereof is constant, and the moving speed of the diamond wire 2 is also constant.

More specifically, and in a non-limiting manner, at a given moment, the straight section corresponding to the engagement portion of the cutting line 2 in the temporary column 3 is perpendicular to a radial straight line originating from the main axis DP, which coincides with the axis of the column and is symmetrical with respect to this radial straight line.

More specifically, this temporary column 3 is arranged for simultaneously cutting a plurality of such boules 1, each arranged radially with respect to the main axis DP in the same way.

Advantageously, the temporary column 3 is built on the basis of a sacrificial mandrel 4, which sacrificial mandrel 4 is formed, in a non-limiting manner, by an axial tube or cylinder. The axis of rotation of the axial tube or cylinder coincides with the main axis DP and has a radius equal to the difference between the eccentricity E and the ingot radius RB. Then, each boule 1 is bonded to the sacrificial mandrel 4 such that its boule axis DB is oriented parallel to the main axis DP, via appropriate preparation processes, to form a bonded assembly 5.

In another particular and non-limiting variant, the adhesion is carried out using commercially available products, for example a two-component adhesive consisting of an epoxy resin and a curing agent such as 1,4,7, 10-tetraazadecane (the epoxy resin and the curing agent together forming a polyepoxide after mixing and curing), in particular from HuntsmanProduct family, or any other adhesive suitable for the materials to be assembled.

In another particular and non-limiting variant, the adhesion is carried out using another commercially available product, such as methacrylate, cyanoacrylate or any other suitable adhesive, for example anaerobic641 binder, which is a methacrylate with a use temperature of up to 150 ℃ and which melts very easily at 250 ℃ under the action of, for example, a stream of hot air.

In a particular application, the ingot 1 extends longitudinally and has a substantially cylindrical shape at least in a central portion thereof; in this example, the ingot axis DB is the axis of the column.

More specifically, the crystal bars 1 are bonded substantially parallel to each other with a distance of 4mm to 6mm therebetween, if possible.

In one particular application for the manufacture of timepiece components, the outer diameter of the temporary column 3 is about 240mm, while the cutting depth in the column 3 is between 30mm and 55mm, the minimum inner support diameter (internal support diameter) of the crystal bar being close to 130 mm. Naturally, the method can be carried out with other dimensional features without departing from the invention.

Due to the excellent continuous nature of the cutting operation, the present invention enables to save diamond wire 2 and operating time and to guarantee a very regular surface state of the edges thus cut in the crystalline sheet 10 obtained at the end of the operation. Finishing by grinding is well known to those skilled in the art and will not be described in detail herein.

Advantageously, the preparation is done by sandblasting or micro-sandblasting or shot-blasting each boule, etc., and subsequently cleaning it with alcohol or other solvent to remove any grease and solid particles, so that the diamond wire 2 does not encounter any particles that cause accelerated wear.

More specifically, as shown in fig. 1 to 8, after the boule 1 is bonded to the sacrificial mandrel 4, the bonded assembly 5 thus formed is inserted into a housing 6 as a mold, in which the bonded assembly 5 is coated with a polymer coating 7 having a specific viscosity, such as epoxy resin, and then left to cure for a necessary time, in particular at least 24 hours, by cooling to a substantially constant temperature to form an overmolded assembly 8. The cooling may be performed with a flow of cold water at room temperature, and the cooling may prevent the coated product from reaching an excessively high temperature, thereby preventing stress causing non-uniformity.

Next, after curing of the coated product 7, preferably epoxy resin, the overmoulded component 8 thus formed is removed from its advantageously recyclable casing, tempered and in particular tempered at a temperature between 40 ℃ and 50 ℃ for at least 12 hours to obtain a temporary column 3.

Thus, the actual cutting operation is applied to the temporary column 3: the temporary column 3 is cut into pieces by moving the diamond wire 2 radially towards the main axis DP and at least to the separation position, to form a blank of circular cut 9.

The separation of these circular cuts 9 is done by cutting the sacrificial mandrel 4 by turning or other tool/machine machining or other means.

The coating 7, in particular epoxy or the like, is then removed from the circular cut 9 by raising the temperature and/or soaking in a heated fluid and/or placing in a tumbling device or the like, to release a crystal piece 10 having two parallel surfaces. Depending on the coating material and the adhesive material selected, the removal of the adhesive can be carried out simultaneously or in different operations, in particular by increasing the temperature.

More specifically, the method is applied to sapphire or ruby crystal bars.

More specifically, the method can be applied to the manufacture of watch mirrors by shape treatment and finishing of the crystal slices thus obtained.

More specifically, the method can be applied to the manufacture of jewelry for timepieces by shape-processing and finishing the crystal piece thus obtained.

The present invention enables a large number of diamond wires 2 to be saved, provides control over reduced cutting time and ensures that the resulting crystal piece 10 has two perfectly parallel main surfaces and a very regular surface state.

Claims (15)

1. Cutting method for cutting at least one ingot (1) using a diamond cutting wire (2), wherein an ingot axis (DB) is determined, perpendicular to which the at least one ingot (1) having an ingot Radius (RB) is cut, the ingot (1) is driven around a main axis (DP) parallel to the ingot axis (DB), and the cutting wire (2) is held tensioned and driven along a straight section in a plane perpendicular to the main axis (DP), wherein a temporary column (3) is made which throughout the cutting operation secures the at least one ingot (1) in place relative to the main axis (DP), throughout the cutting operation the ingot axis (DB) is passed on both sides of the straight section during cutting of the at least one ingot (1) inside the temporary column (3), wherein the temporary column (3) is established on the basis of a sacrificial mandrel (4) formed by an axial tube or cylinder whose axis of rotation coincides with the main axis (DP) and whose radius is equal to the difference between the eccentricity (E) and the ingot Radius (RB), the at least one ingot (1) being bonded to the sacrificial mandrel (4) after preparation in such a way that each of the ingots (1) is oriented with its ingot axis (DB) parallel to the main axis (DP) to form a bonded assembly (5), wherein, after the ingot (1) is bonded to the sacrificial mandrel (4), the bonded assembly (5) is inserted into a housing (6), the bonded assembly (5) is clad with a coating material (7) in the housing (6), the coating material being cured to form a clad assembly (8), characterized in that, after the curing of the coating material (7), the overmoulded component (8) is removed from the casing (6) and the overmoulded component (8) is tempered to obtain the temporary column (3).

2. The cutting method according to claim 1, wherein the preparation process of each of the boules (1) is performed by: the boule is grit blasted or shot blasted and then cleaned with a solvent that removes any grease and solid particles to remove any grease and solid particles.

3. The cutting method according to claim 1, wherein the main axis (DP) is located at an eccentricity (E) from the ingot axis (DB) that is greater than the ingot Radius (RB), wherein the cutting wire (2) is held in tension and driven between a soft-close position, in which the distance of the cutting wire (2) from the main axis (DP) has a value equal to the sum of the eccentricity (E) and the ingot Radius (RB), and a disengaged position, in which the distance of the cutting wire (2) from the main axis (DP) has a value equal to the difference between the eccentricity (E) and the ingot Radius (RB).

4. The cutting method according to claim 2, wherein the main axis (DP) is located at an eccentricity (E) from the ingot axis (DB) that is greater than the ingot Radius (RB), wherein the cutting wire (2) is held tensioned and driven between a soft-close position, in which the distance of the cutting wire (2) from the main axis (DP) has a value equal to the sum of the eccentricity (E) and the ingot Radius (RB), and a disengaged position, in which the distance of the cutting wire (2) from the main axis (DP) has a value equal to the difference between the eccentricity (E) and the ingot Radius (RB).

5. Cutting method according to claim 1, characterized in that the temporary column (3) is arranged for cutting a plurality of the boules (1) simultaneously, each arranged radially with respect to the main axis (DP) in the same way.

6. Cutting method according to claim 3 or 4, characterized in that the temporary column (3) is cut into pieces by moving the cutting line (2) radially towards the main axis (DP) at least to the separation position, so as to form a blank of circular cut (9).

7. Cutting method according to claim 6, characterized in that the separation of the circular cut (9) is done by cutting the sacrificial mandrel (4) by means of a tooling method that can cut the sacrificial mandrel (4).

8. Cutting method according to claim 7, characterized in that the coating material (7) is removed from the circular cut (9) by increasing the temperature and/or soaking in a hot fluid and/or in a tumbling device to release a crystal piece (10) with two parallel surfaces.

9. The cutting method according to claim 1, wherein the ingot is selected to be made of sapphire or ruby.

10. The cutting method according to claim 2, wherein the blasting is micro blasting.

11. The cutting method according to claim 2, wherein the solvent is alcohol.

12. The cutting method of claim 7, wherein the tooling is turning.

13. Cutting method according to claim 1 or 8, characterized in that the coating material (7) is an epoxy resin.

14. Use of the cutting method according to claim 8 for manufacturing a watch mirror, characterized in that the crystal piece (10) made according to the cutting method is subjected to a shape treatment and a finishing operation.

15. Use of the cutting method according to claim 8 for the manufacture of a timepiece gemstone, characterized in that a shape treatment and a finishing operation are performed on the crystal piece (10) made according to the cutting method.