CH714641A1 - Method of manufacturing a quartz resonator and cutting tool for the implementation of the method - Google Patents

Abstract

The present invention relates to a method of manufacturing a quartz piece comprising a dome delimited by an inner sphere portion (2a) and an outer sphere portion, and a central portion (3a) passing through the dome, the method comprising the following steps: machining in parallel of the central portion (3a) inside the dome and the inner sphere portion (2a) following the rotation of the piece | 17) and the cutting tool (4 ) respectively around an axis of the workpiece (18) and a first machining axis (13) inclined relative to the axis of the workpiece (18) and to the translation of said cutting tool (4) on along the axis of the workpiece (18), machining the outer sphere portion and the central portion (3a) external to the dome following the rotation of the workpiece (17) and the cutting tool (4) respectively about the axis of the workpiece (18) and a second machining axis. The present invention also relates to the cutting tool (4) used to carry out the method.

Description

Description

OBJECT OF THE INVENTION The present invention relates to the field of machining. It relates more precisely to a process for manufacturing a quartz resonator comprising a dome. It also relates to the machining tool specifically designed to carry out the method according to the invention.

Technological background and state of the art Glass resonators are used in many fields (space, military, etc.). Their geometry depends on the application. They may include a spherical cavity as shown in FIG. 1A. This geometry is particularly complex to machine because, on the one hand, it is difficult to obtain perfect sphericity with manufacturing tolerances of the order of a micron and, on the other hand, it is necessary to avoid bringing the part into resonance , which would break it.

To date, dome resonators are manufactured with abrasive tools of small diameters requiring extremely long manufacturing times, of several tens of hours (40-50 h).

SUMMARY OF THE INVENTION The main object of the present invention is to propose a new method for manufacturing a quartz resonator making it possible to drastically reduce the manufacturing time while guaranteeing very high precision machining. It also aims to provide a new cutting tool for implementing this process.

The resonator comprises a dome delimited by an inner sphere portion and by an outer sphere portion. The machining process according to the invention of the dome, which will be called a generative process, follows from the principle in geometry that a plane which cuts a sphere gives a circle and consists in machining a multitude of circles on the basic part in order to ultimately produce the interior and exterior spherical portions. In separate steps, the inner and outer sphere portions are machined using a specific tool comprising a cavity terminated by an abrasive toric surface with a working face inside the cavity and a working face outside the cavity. By rotating the part and the tool around separate axes and partranslation of the tool along the axis of rotation of the part, the portion of the inner sphere is hollowed out. In addition, the inner sphere portion has in its inner volume a central part of a tree. This central part is machined in parallel with the inner sphere portion, the outer working face and the inner working face of the cutting tool machining the inner sphere portion and the central part respectively. In addition, the outer sphere portion is also machined by rotating the part and the cutting tool around separate axes. In addition, the resonator shaft may have cylindrical surfaces external to the dome, arranged on either side of the latter. These surfaces are machined during the same process with a conventional grinding wheel.

The method according to the invention thus makes it possible to produce the part in a single take, which means that the spatial orientation of the part is never lost. The machining process according to the invention guarantees perfect concentricity between the portion of the inner sphere and the portion of the outer sphere. Likewise, the method guarantees a perfect geometric agreement between the portions of the sphere and the shaft line formed by the central part and the two end cylindrical bearings. The process developed for the production of the spherical portions thus guarantees very high precision of the shape and an excellent surface condition obtained by crossing the machining lines. This process also allows a much higher productivity, at least a factor of 4 compared to the current process.

Other advantages will emerge from the characteristics expressed in the claims, from the detailed description of the invention illustrated below with the aid of the appended drawings given by way of non-limiting examples.

Brief description of the figures

[0008] Figs. 1A and 1B respectively represent a plan view and a longitudinal sectional view along the axis A-A of the resonator intended to be manufactured with the method according to the invention. Fig. 2A shows a three-dimensional view of the tool according to the invention used to implement the method according to the invention. Fig. 2B shows a view in longitudinal section of this tool, with an enlargement B of its abrasive end in contact with the material. Figs. 3 to 7 are schematic sequential views of the manufacturing process according to the invention. Figs. 3 and 4 represent the step of machining the front span of the resonator with a conventional cylindrical grinding wheel.

CH 714 641 A1

Figs. 5A-5C represent the step of machining the inner sphere portion with the cutting tool according to the invention. In fig. 5A, the cutting tool is positioned to start machining. In fig. 5B and 5C which are plan and sectional views respectively, the cutting tool has finished machining the inner sphere portion and the central part of the shaft.

Fig. 6 shows the step of machining the outer sphere portion and the central part of the shaft with the cutting tool according to the invention.

Fig. 7 shows the final cutting step at one end of the part.

Fig. 8 shows a variant of the resonator of FIG. 1A with the tool according to the invention in place for machining the outer sphere portion.

General description of the invention [0009] The part and, more specifically, the resonator 1 intended to be manufactured with the method according to the invention is shown in FIGS. 1A and 1B. It comprises a dome 2 delimited by a portion of inner sphere 2a and by a portion of outer sphere 2b which each form a half-sphere in the example illustrated. The dome 2 is crossed by a shaft 3. This shaft 3 is formed by a central part 3a on the one hand inside the dome 2 and on the other hand outside the latter on the side of the outer sphere portion. It further comprises two cylindrical surfaces 3b and 3c respectively attached to the ends of the central part 3a. A so-called front bearing 3b is disposed on the side of the inner sphere portion 2a and a so-called rear bearing 3c is arranged on the side of the outer sphere portion 2b. In the example illustrated, both have a diameter smaller than that of the central part 3a. The portions of spheres 2a and 2b as well as the ranges 3b and 3c are in geometric agreement in terms of concentricity and total beat.

Note that alternatively, as shown in fig. 8, the part 1 could be devoid of the rear bearing 3c and of the central part 3a which makes the connection up to the outer sphere portion 2b. Furthermore, it will be specified that the dimensions in FIG. 1A are given by way of illustration, other dimensions which can easily be produced with the method according to the invention. However, to emphasize the critical nature of the machining of the quartz piece, it should be mentioned that the thickness of the wall of the dome can be less than a millimeter. More precisely, it can be between 1.5 and 0.5 mm, and even more precisely between 1 and 0.6 mm.

To implement the machining process according to the invention, a cutting tool 4, also called an abrasive wheel, shown in Figs. 2A and 2B was specifically designed. It comprises a cavity 5 delimited at its end intended to be in contact with the material an abrasive surface 6 in diamond of toric shape shown in more detail in FIG. 2B. The inner 5b and outer 5a walls of the cavity 5 have clearances intended to receive parts of the part being machined in order to avoid a collision between the part and the cutting tool. These clearances are adapted to the geometry of the workpiece. The outer wall 5a thus comprises, following the cylindrical part 7, a notch 8 extending over the entire circumference of the wall 5a of the cavity. This notch 8 is intended to receive the circular periphery of the inner sphere portion 2b when the latter is at the end of machining (fig. 5C). Inside the cavity 5, the wall 5b comprises, following the cylindrical part 7, a notch 9 followed by a frustoconical part 10 intended to accommodate the front bearing 3b during the machining of the inner sphere portion 2a (figs.5B and 5C). The frusto-conical part 10 has a decreasing diameter in the direction opposite to the abrasive surface 6 and ends in a channel 11 passing through the tool 4 to the surface opposite to the abrasive surface 6 or to a lateral surface (variant not shown) relative to the longitudinal axis of the tool. This channel allows the flow of a cutting liquid intended to cool the part and to evacuate the particles produced by the cutting.

As shown in Figs. 3 to 5C; the machining machine has a first spindle 16 on which the part 17 to be machined is fixed. The spindle 16 is rotatably mounted around an axis 18. The machining machine further comprises a second spindle 19 serving as a spindle for taking up the part being machined and being rotatably mounted along the same axis 18 (fig. 6). The machine is also equipped with a machining spindle 15 which can receive the various cutting tools. The machining spindle 15 receives a first conventional cutting tool 12, such as a cylindrical grinding wheel shown in FIGS. 3 and 4, intended to machine the front range 3b and the rear range 3c of the resonator. The spindle 15 also receives a second cutting tool which is the diamond wheel 4 according to the invention. The machining spindle 15 is rotatably mounted around an axis inclined at an angle a with respect to the axis 18 of the spindle 16. This axis is referenced 13 when the abrasive wheel 4 manufactures the portion of inner sphere 2a ( Fig. 5B) and referenced 14 when the abrasive wheel 4 machines the outer sphere portion 2b (Fig. 6). For the machining of the resonator 1 with the cutting tool 4 according to the invention, this angle a is between 20 and 150 ° and preferably between 20 and 135 °. More precisely, the axis of rotation 13 is inclined at an angle a, preferably between 20 and 45 ° and the axis of rotation 14 is inclined at an angle a between 90 and 150 ° and, preferably , between 90 and 135 °. The machining spindle 15 is also mounted movable in translation along the axis 18 of the spindle 16 (fig. 5A). It can also be mounted movable in translation along its axis of rotation.

The manufacturing method according to the invention of the resonator is illustrated using the sequential views of FIGS. 3 to 7 and includes the following steps:

- Machining of the rear reach 3c with the conventional cutting tool;

CH 714 641 A1

- Machining of the front reach 3b with the conventional cutting tool;

- Machining of the inner sphere portion 2a and the central portion 3a inner to the inner sphere portion 2a with the cutting tool 4 according to the invention;

- Machining of the outer sphere portion 2b and of the central portion 3a outside the dome with the cutting tool 4 according to the invention.

It will be noted that the above steps can be carried out in different orders. The only constraint is to machine at least partially the front bearing 3b, before machining the inner sphere portion 2a and to at least partially machine the rear bearing 3c and its central connection part 2a before machining the portion of outer sphere to create space for the placement of the cutting tool. Furthermore, the step of machining the inner sphere portion being the most critical, it is preferably carried out before the step of machining the outer sphere portion in order to have more material and therefore reduce the fragility of the piece. In addition, it goes without saying that, when the part is devoid of the rear bearing surface and of the central connection part with the outer sphere portion, the machining steps which are related to it need not be.

The machining begins by starting from a cylindrical piece 17 of quartz fixed on the spindle 16 (fig. 3). The length of the piece is greater than the length of the finished part so as to have sufficient grip. The length is preferably 10 mm longer, and more preferably 15 mm, than the length of the finished part. The first machining step consists of roughing and finishing the front span 3b, including the chamfer at the free end of the latter (fig. 4). This step is carried out in a conventional manner using the cutting tool 12.

The second step shown in Figs. 5A-5C consists in machining the portion of inner sphere 2a (roughing and finishing) by the so-called generative process. The combination of the rotations of the part 17 and the abrasive wheel 4 around the two respective axes 18,13 inclined relative to each other will generate the almost perfect hemisphere regardless of the diameter of the tool. However, a condition must be fulfilled for the sphere to be perfectly spherical. The axis of rotation 13 of the abrasive wheel 4 must pass through the center 0 of the sphere as shown in fig. 5B. The method simultaneously generates the interior sphere portion 2a, the central portion 3a and the radius at the junction between the interior sphere portion 2a and the central portion 3a. The grinding wheel 4 is brought opposite the part 17 with an axis of rotation 13 inclined at a given angle relative to the axis of rotation 18 of the part (fig. 5A). The abrasive wheel 4 translated along the axis 18 of the workpiece and rotating around the axis 13 is brought into contact with the material and generates a circular machining path within the material (fig. 5A-5C ). More specifically, the inner face 6b of the abrasive surface 6 machines the central part 3a and the outer face 6a of the abrasive surface 6 machines the inner sphere portion 2a. Preferably, the workpiece and the tool are rotated in opposite directions so that the machining grooves intersect for a better surface finish.

Then, similarly to the first step, the rear seat and the central part of connection with the outer sphere portion are roughed out with the conventional cutting tool (fig. 5A-5C with the conventional cutting tool not shown).

For the machining of the outer sphere portion 2b, the part 17 is supported using the recovery pin 19 clamped on the front bearing 3b machined in the first step (fig. 6). The two pins 16,19 work in synchronized mode. In this step, the roughing and finishing of the outer sphere portion 2b is carried out according to the generative method with the cutting tool 4 rotated around the axis 14 and with the part rotated around the axis 18 with again, preferably, opposite directions of rotation for the two axes. As before, the axis of rotation 14 of the abrasive wheel 4 intersects the axis of rotation 18 of the part 17 at the center of the sphere. The finishing of the central part 3a as well as the machining of the radius at the junction between the central part 3a and the outer sphere portion 2b are also carried out with the cutting tool according to the invention moving along the axis 18 of the room. As for the finishing of the rear reach 3c, it is carried out with the conventional cutting tool. It will be noted that it is possible to introduce a support (not shown), preferably flexible, within the interior sphere portion so as to dampen any vibrational behavior that could be generated in the finishing phase of the sphere portion exterior. For the variant of fig. 8 without a rear bearing surface and without a central connection part, the outer sphere portion is similarly produced with the generative method according to the invention. In the example illustrated, the angle a is maintained at a value of the order of 130 ° during machining but could be increased up to 150 °.

The last step shown in FIG. 7 is the embodiment of the chamfer of the rear bearing 3c and the cutting of the end of the latter after removal of the part from the first spindle 16. The finished part 1 is then released from the take-up spindle 19.

During the machining, a coolant 20 can be injected into the channel 11 of the abrasive wheel 4. In addition, as illustrated in figs. 5C and 6, a clearance is maintained between the part 17 and a part of the abrasive surface 6 of the grinding wheel 4 to allow the liquid 20 and the machined material to flow.

Legend [1] (1) Resonator

CH 714 641 A1 (2) Dome

at. Inner sphere portion

b. Portion of outer sphere (3) Tree

at. Central part

b. Front range

vs. Rear reach (4) Cutting tool, also called abrasive wheel (5) Tool cavity

at. Outer wall

b. Inner wall (6) O-ring part of the tool coated with an abrasive surface

at. External working face

b. Inner working face (7) Cylindrical part of the cavity (8) Notch on the outer wall of the cavity (9) Notch on the inner wall of the cavity (10) Tapered part of the cavity (11) Cooling channel (12 ) Another cutting tool, also called conventional grinding wheel (13) First axis of rotation of the abrasive wheel (14) Second axis of rotation of the abrasive wheel (15) Machining spindle, also called third spindle (16) First spindle, also called workpiece holder (17) Workpiece or piece of quartz (18) Rotation axis of the first spindle (19) Second spindle or return spindle (20) Coolant

claims

Claims (15)

1. Method for manufacturing a piece (1) of quartz comprising a dome (2) delimited by an inner sphere portion (2a) and by an outer sphere portion (2b), and a shaft (3) comprising a part central (3a) connection with the inner sphere portion (2a) and extending at least in the interior volume of the dome (2), the method comprising the following steps: - Provision of a machining machine including: • a workpiece carrier (16) rotatably mounted about an axis (18), called the workpiece axis, • a machining spindle (15) rotatably mounted around another axis (13,14), said axis machining, inclined at an angle a relative to the axis of the workpiece (18), and mounted movable in translation along the axis of the workpiece (18), said machining spindle (15) being able to receiving at least a first cut tool (12) and a second cut tool (4), the second cutting tool (4) being provided with a cavity (5) terminated at one end by an abrasive O-ring surface (6) comprising a inner working face (6b) to the cavity (5) and an outer working face (6a) to the cavity (5), CH 714 641 A1 - Provision of a piece of quartz (17) and fixing of the piece (17) in the workpiece carrier (16), - Machining in parallel of the central part (3a) of the shaft (3) and of the inner sphere portion (2a) following the rotation of the workpiece carrier (16) and the second cutting tool (4) around the workpiece axis (18) and the machining axis (13) respectively, and at the translation of the second cutting tool (4) along the workpiece axis (18), l machining of the central part (3a) and of the inner sphere portion (2a) being carried out by contact respectively with the inner working face (6b) and with the outer working face (6a) of the abrasive toric surface (6 ) - Machining of the outer sphere portion (2b) following the rotation of the workpiece carrier (16) and the second cutting tool (4) around the axis of the workpiece (18) and the axis respectively machining (14). 2. Method according to claim 1, characterized in that the inner sphere portion (2a) is machined before the outer sphere portion (2b). 3. Method according to claim 1 or 2, characterized in that the shaft (3) comprises, following the central part (3a), a front bearing (3b) disposed outside the interior volume of the dome (2) on the side of the inner sphere portion (2a), said front face (3b) being machined, using the first cutting tool (12), at least partially before the step of machining the part central (3a) of the shaft (3) and of the inner sphere portion (2a). 4. Method according to any one of the preceding claims, characterized in that the central part (3a) further extends outside the dome (2) on the side of the outer sphere portion (2b), l 'shaft (3) comprising following said central part (3a) extending outside the dome (2) a rear bearing (3c), said central part (3a) extending outside the dome (2) and said rear surface (3c) being machined using the first cutting tool (12) at least partially before the step of machining the portion of the outer sphere (2b). 5. Method according to claim 4, characterized in that the finishing machining of the central part (3a) extending outside the dome (2) is carried out during the step of machining the portion outer sphere (2b) with the second cutting tool (4). 6. Method according to any one of the preceding claims, characterized in that the second cutting tool (4) comprises a channel (11) for the flow of a cooling fluid, said channel (11) passing through the second tool cutting (4) from the cavity (5). 7. Method according to any one of the preceding claims, characterized in that a clearance between an area of the abrasive toric surface (6) and the piece (17) is maintained during the machining steps with the second cutting tool. (4). 8. Method according to any one of the preceding claims, characterized in that the workpiece carrier (16) and the second cutting tool (4) are rotated in opposite directions during the machining steps. 9. Method according to any one of the preceding claims, characterized in that the angle a is between 20 and 150 °, and preferably between 20 and 135 °. 10. Method according to any one of the preceding claims, characterized in that the angle a is between 20 and 45 ° during the step of machining the central part (3a) of the shaft (3) and of the inner sphere portion (2a) and between 90 and 135 ° during the step of machining the outer sphere portion (2b). 11. Method according to any one of claims 2 to 10, characterized in that a support is disposed within the interior sphere portion (2a) during the step of machining the exterior sphere portion (2b ) in order to dampen any vibration behavior. 12. Cutting tool (4) suitable for machining a part (1) comprising a dome (2) delimited by an inner sphere portion (2a) and by an outer sphere portion (2b), and a shaft (3) comprising a central part (3a) connecting with the inner sphere portion (2a) and extending at least in the interior volume of the dome (2), said cutting tool (4) being provided with a cavity (5) terminated at one end by an abrasive toric surface (6), said abrasive toric surface (6) comprising an inner working face (6b) at the cavity (5) and an outer working face (6a) at the cavity (5). 13. Cutting tool (4) according to claim 12, characterized in that it comprises on its outer wall (5a) to the cavity (5) a notch (8) intended to receive one end of the portion of the inner sphere ( 2a) during the machining of the latter. 14. Cutting tool (4) according to claim 12 or 13, characterized in that it has on its inner wall (5b) to the cavity (5) clearances intended to accommodate a front bearing (3b) when the shaft (3) comprises, following the central part (3a), a front bearing (3b) external to the interior volume of the cup (2) and disposed on the side of the interior sphere portion (2a), said clearances forming a frustoconical part (10) positioned opposite the abrasive O-ring surface (6). 15. Cutting tool (4) according to any one of claims 12 to 14, characterized in that it comprises a channel (11) passing through the cutting tool (4) from the cavity (5).