CN107262906A - A kind of Miniature lathe - Google Patents

Abstract

The invention discloses a miniature lathe, which is used to process workpieces by using the FIB/SEM dual-beam system in the vacuum chamber of the FIB/SEM dual-beam system, including a base with only t-axis rotational freedom and fixedly installed on the A multi-axis precision mobile platform with x, y, z three-axis degrees of freedom on the base, an isolation plate is installed on the multi-axis precision mobile platform, and a bearing seat is installed on the isolation plate. A sliding bearing with automatic centering function is installed to support the main shaft. One end of the main shaft has an ER elastic collet structure for clamping a cylindrical workpiece. The main shaft is driven by a stepping motor through a belt; the FIB/ The SEM dual-beam system includes the FIB pole piece for turning the workpiece and the SEM pole piece for in-situ on-line observation of the workpiece. The invention is simple in structure, stable and reliable, and can realize on-line monitoring of the machining process of miniature shaft parts.

Description

a miniature lathe

technical field

The invention relates to the technical field of micro lathes, in particular to a micro lathe using focused ion beams for work processing.

Background technique

With the development of high technology, the fields of semiconductor, aerospace and national defense have increasingly extensive demand for miniature shaft parts with feature sizes ranging from microns to millimeters.

At present, miniature shaft parts are usually turned on ultra-precision lathes under traditional conditions. Because the processing scale is at the micro-nano level, traditional turning processing has problems such as difficult tool setting and complicated clamping process, and contact processing is easy to cause deformation of the workpiece under force and affect processing accuracy. In addition, when the processing quality of traditional turning workpieces is characterized offline, additional uncertainties may be introduced, including air oxidation, dust pollution, etc., and there are still certain limitations in the ultra-precision machining of miniature shaft parts.

Focused ion beam has been widely used in the field of micro-nano manufacturing in recent years due to its advantages of nanoscale manufacturing precision, direct writing processing, and good flexibility. Therefore, it is of great significance to develop a lathe that utilizes focused ion beams to work on machining to realize ultra-precision non-contact machining of miniature shaft parts.

Contents of the invention

The object of the present invention is to provide a micro-lathe that uses focused ion beams to process workpieces in view of the technical defects in the prior art.

The technical scheme adopted for realizing the purpose of the present invention is:

A kind of miniature lathe, used for processing the workpiece by using the FIB/SEM dual-beam system in the vacuum chamber of the FIB/SEM dual-beam system, including a base with only t-axis rotation degree of freedom and fixedly installed on the base A multi-axis precision mobile table with three-axis degrees of freedom of x, y, and z. An isolation plate is installed on the multi-axis precision mobile table. A bearing seat is installed on the isolation plate, and a bearing seat is installed in the bearing seat. The sliding bearing with automatic centering function is used to support the main shaft. One end of the main shaft has an ER collet for clamping the cylindrical workpiece. The main shaft is driven by a stepping motor through a belt; the FIB/SEM double-beam system Including the FIB pole piece for turning the workpiece and the SEM pole piece for in-situ on-line observation of the workpiece.

The stepping motor is installed on the isolation plate through a motor bracket, and the main shaft is connected with the motor shaft of the stepping motor through a toothed belt and a pulley.

There are two groups of sliding bearings, which are installed on both sides of the bearing seat respectively, and each group of sliding bearings includes a convex hemispherical journal and a concave hemispherical bearing bush.

A retaining ring is installed on the motor side of the bearing seat, the outer circle of the retaining ring is fixed on the bearing seat by bolts, and the inner circle of the retaining ring axially positions the concave hemispherical bearing bush installed on the motor side , the concave hemispherical bearing pad on the other side is fixed on the bearing seat by bolts.

The rotation angle of the base ranges from -10° to 52°.

The beam current of the focused ion beam formed by the FIB pole piece is 1pA-20nA, and the accelerating voltage is 1keV-30keV.

The x- and y-direction strokes of the multi-axis precision moving stage are ±20 mm, the z-direction stroke is 10 mm, and the movement accuracy is 1 μm.

The ER collet is equipped with a conical nut that allows the ER collet to grip the workpiece.

The sliding bearing is made of brass, and the main shaft is made of stainless steel.

The motor controller of the stepper motor is placed in the external atmosphere of the FIB/SEM dual-beam system, and is connected to the stepper motor through a flange to realize motion control of the stepper motor.

The invention is simple in structure, stable and reliable, and can realize on-line monitoring of the machining process of miniature shaft parts. It can be applied to the focused ion beam FIB processing of typical miniature shaft parts, and it is convenient for clamping and tool setting, and can significantly improve the processing efficiency and processing accuracy.

Description of drawings

Fig. 1 is the structural representation of miniature lathe of the present invention;

Fig. 2 is an exploded view of the main shaft transmission part of the micro lathe;

Fig. 3 is a schematic diagram of the machining process of miniature shaft parts;

Fig. 4 is a schematic diagram of the FIB processing area on the workpiece;

In the figure: 1 base; 2 multi-axis precision moving table; 3 isolation plate; 4 workpiece; 5FIB pole shoe; 6SEM pole shoe; 7 stepping motor; 8 motor bracket; 9 toothed belt and pulley; 11 bearing seat; 12 bearing bush; 13 journal; 14 main shaft; 15 fastening nut; 16 tapered nut; 17ER collet; 50 polyion beam;

detailed description

The present invention will be described in further detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention.

As shown in Figure 1-4, a miniature lathe is used to process workpieces by using the FIB/SEM dual-beam system in the vacuum chamber of the FIB/SEM dual-beam system, including a base with only t-axis rotational freedom 1, and a multi-axis precision mobile table 2 with x, y, z three-axis degrees of freedom fixedly installed on the base, an isolation plate 3 is installed on the multi-axis precision mobile table, and the isolation plate is installed There is a bearing seat 11, a sliding bearing with automatic centering function is installed in the bearing seat 11 to support the main shaft 14, and one end of the main shaft has an ER collet 17 for clamping the cylindrical workpiece 4, the The spindle is driven by a stepping motor 7 through a belt, and the FIB/SEM dual-beam system includes a FIB (Focused ionbeam) pole shoe 5 for turning the workpiece and an SEM pole shoe 6 for in-situ on-line observation of the workpiece.

During processing, under the real-time observation of the SEM pole shoe 6, the multi-axis precision moving table 2 quickly moves the workpiece 4 to the area to be processed, and rotates the base 52° along the t-axis so that the axes of the FIB pole shoe 5 and the workpiece 4 are aligned. vertical relationship, so that the FIB pole piece 5 can be used to replace the turning tool to realize material removal on the order of 4 micronano to the workpiece.

Specifically, the stepping motor 7 is mounted on the isolation plate 3 through an "L"-shaped motor bracket 8 , and the main shaft is connected to the motor shaft of the stepping motor 7 through a toothed belt and a pulley 9 . Among them, the isolation plate 3 is fixed on the multi-axis precision mobile table 2, and the "L" type motor bracket 8 and the bearing seat 11 are fixed on the isolation plate by screws. The function of the isolation plate is to prevent the motor bracket 8 and the bearing seat 11 from directly contacting The multi-axis precision mobile platform is damaged due to the connection of the multi-axis precision mobile platform 2.

Wherein, the motor bracket 8 is provided with a hole, so that the motor shaft extends out of the motor bracket when the stepper motor 7 is fixed, and the motor shaft is connected with the toothed belt and the pulley 9 through the top wire, and the rotational movement and the torque are passed through The belt drive is transmitted to the main shaft 14 .

Specifically, the sliding bearings are two groups, using hemispherical sliding bearings, installed on both sides of the bearing seat respectively, and processed by ultra-precision lathe, with automatic centering function, which can improve the rotation accuracy of the main shaft. Wherein, each set of sliding bearings includes a convex hemispherical journal 13 and a concave hemispherical bearing bush 12 . The convex hemispherical structure of the convex hemispherical journal 13 cooperates with the concave hemisphere of the concave hemispherical bearing bush 12 to realize the installation of the convex hemispherical journal 13 in the concave hemispherical bearing bush 12. Shaped bearing bush 12 is installed in the bearing housing 11, and the main shaft 14 is connected with the sliding bearings on both sides.

Wherein, the motor side of the bearing seat is installed with a retaining ring 10 for pressing the bearing bush, the outer circle of the retaining ring is fixed on the bearing seat 11 by bolts, and the inner circle of the retaining ring is installed on the motor side The concave hemispherical bearing bush 13 on the other side is fixed on the bearing seat 11 by bolts for axial positioning. During assembly, firstly, the bearing bush 12 on one side is fixed on the bearing housing 11 by bolts, and the bearing bush 12 on the other side is compressed and fixed by the retaining ring 10 fixed by bolts. Then, the main shaft 14 is passed through the bearing housing 11 and the bearing bushes 12 at both ends, and then a pair of journals 13 are fixed on the main shaft 13 by fastening nuts 15, and the shaft shoulders on both sides of the main shaft 14 are positioned.

In the present invention, the base provides support for the entire set of micro lathes, and the base can be provided with a t-axis rotation degree of freedom by configuring a well-known t-axis rotation control mechanism. Preferably, the t-axis rotation angle range of the base is -10°～52°.

Preferably, the beam current of the focused ion beam formed by the FIB pole piece is 1pA-20nA, and the accelerating voltage is 1keV-30keV.

In the present invention, the multi-axis precision mobile stage is a FIB/SEM dual-beam system with its own worktable stage, fixed on the base, and can realize t-axis rotation with the base. In addition, it has x, y horizontal degrees of freedom and z vertical degrees of freedom, which can realize fast and accurate tool setting in the horizontal aspect.

Preferably, the x- and y-direction strokes of the multi-axis precision moving stage are ±20 mm, the z-direction stroke is 10 mm, and the movement accuracy is 1 μm.

Wherein, the ER elastic collet is equipped with a conical nut 16 for clamping the workpiece by the ER elastic collet, and is assembled on the main shaft 14 with the ER elastic collet. When processing the workpiece, the workpiece to be processed is placed in the ER collet at one end of the main shaft 14 , and then the workpiece to be processed is fixed by the conical nut 16 .

Preferably, the sliding bearing is made of H62 brass material, which can be processed into a convex hemispherical journal and a concave hemispherical bearing bush by an ultra-precision lathe, which is beneficial to the automatic centering of the sliding bearing and improves the rotation accuracy of the main shaft. The contact surfaces of the journal and the bearing bush of the sliding bearing are all processed into a mirror surface quality to reduce the coefficient of friction.

Preferably, the main shaft is made of stainless steel, one end is processed into an ER elastic chuck structure, and the workpiece is clamped on the ER elastic chuck by using a conical nut 16; the shaft end of the main shaft and the ER elastic chuck adopt an integral structure , which is beneficial to improve the rigidity of the lathe and reduce the fit error.

Specifically, the motor controller of the stepper motor is placed in the external atmosphere of the FIB/SEM dual-beam system, and is connected to the stepper motor through a flange to realize motion control of the stepper motor.

It should be noted that, in the present invention, the multi-axis precision moving table 2 itself has three degrees of freedom of x, y, and z, and the workpiece can be moved to the field of view center of the FIB/SEM dual-beam system through the x, y axes. And control the workpiece to move up along the z-axis to the optimum height for FIB non-contact processing (wherein the distance between the area to be processed and the FIB pole shoe 5 is about 5 mm).

Before FIB processing, the workpiece is rotated 52° by the t-axis, so that the FIB is perpendicular to the axis of the workpiece, and the FIB processing area 41 is determined according to the processing requirements and the FIB in-situ measurement scale. Figure 3 is a schematic diagram of the machining process of the workpiece. First, set the FIB acceleration voltage to 30keV and the beam current to 3nA to rough the workpiece to improve the processing efficiency; then use the FIB acceleration voltage to 5keV and the beam current to 0.1nA to perform Finishing to improve machining accuracy.

After "turning" the workpiece by using FIB instead of the turning tool, rotate the t-axis from 52° to 0°, and then use the SEM in-situ online observation function to perform high-resolution characterization of the removal amount and processing quality of the workpiece, and then complete the miniature Focused ion beam ultra-precision machining of shaft parts.

Due to the limited space in the vacuum chamber of the FIB/SEM dual-beam system, in the present invention, the transmission mode of the stepper motor and the spindle adopts a belt drive, so that the micro lathe has a "U"-shaped layout and a compact structure.

Outside the vacuum environment of the FIB/SEM double-beam system, a dial gauge is used to test the rotation accuracy of the micro lathe of the present invention. By controlling the speed of the motor and the deceleration process of the pulley drive, the speed of the spindle of the micro lathe reaches 0.5r/min. The measured rotation accuracy of the main shaft of the micro lathe is 2 μm, which shows that the rotation accuracy of the main shaft of the present invention meets the processing requirements.

The miniature lathe that utilizes focused ion beam (FIB) to replace the turning tool proposed by the present invention is used to realize FIB processing of typical miniature shaft parts. Compared with traditional lathes, it has the following significant advantages:

First of all: the present invention is applied to the FIB/SEM dual-beam system for material removal processing in a high-vacuum environment. It can realize SEM high-resolution online observation of processed materials, which is convenient for in-situ characterization and analysis of material removal amount and processed surface quality. Additional uncertain factors such as air oxidation and dust pollution introduced by offline characterization are avoided.

Secondly: the integrated structure of the spindle and the chuck is beneficial to improve the lathe rigidity and reduce the matching error; the hemispherical sliding bearing has the function of automatic centering, which is beneficial to improve the rotation accuracy of the spindle and the machining accuracy of the workpiece.

In addition: the core components are non-ferromagnetic, and the tool setting process is carried out under the high-resolution online monitoring of SEM, with high precision and flexible operation, easy "tool setting", which significantly improves the processing efficiency of the workpiece; moreover, by controlling the energy of the focused ion beam With the size of the beam, the controllable adjustment of the material removal rate can be realized.

The above is only a preferred embodiment of the present invention, it should be pointed out that, for those of ordinary skill in the art, without departing from the principle of the present invention, some improvements and modifications can also be made, these improvements and Retouching should also be regarded as the protection scope of the present invention.

Claims (10)

1. A miniature lathe, is characterized in that, utilizes FIB/SEM double-beam system to process workpiece in the vacuum cavity that is used to be integrated in FIB/SEM double-beam system, comprises the base that only has t-axis rotation degree of freedom and fixed A multi-axis precision mobile table with three-axis degrees of freedom of x, y, and z installed on the base, an isolation plate is installed on the multi-axis precision mobile table, and a bearing seat is installed on the isolation plate. A sliding bearing with automatic centering function is installed in the bearing seat to support the main shaft. One end of the main shaft has an ER elastic collet for clamping a cylindrical workpiece. The main shaft is driven by a stepping motor through a belt; The FIB/SEM dual-beam system includes the FIB pole piece for turning the workpiece and the SEM pole piece for in-situ on-line observation of the workpiece. 2. miniature lathe as claimed in claim 1, is characterized in that, described stepper motor is installed on described isolation plate by motor bracket, and described main shaft passes toothed belt and pulley and the motor shaft of described stepper motor connect. 3. The miniature lathe according to claim 1, wherein the sliding bearings are in two groups, respectively mounted on both sides of the bearing seat, and each group of sliding bearings includes a convex hemispherical journal and a concave hemispherical journal. Bearing bush. 4. The miniature lathe according to claim 3, wherein a retaining ring is installed on the motor side of the bearing seat, the outer circle of the retaining ring is fixed on the bearing seat by bolts, and the inner circle of the retaining ring The circle axially locates the concave hemispherical bearing bush installed on the motor side, and the concave hemispherical bearing bush on the other side is fixed on the bearing seat by bolts. 5. The miniature lathe according to claim 1, wherein the rotation angle of the base ranges from -10° to 52°. 6 . The micro lathe according to claim 1 , wherein the beam current of the focused ion beam formed by the FIB pole piece is 1 pA-20 nA, and the accelerating voltage is 1 keV-30 keV. 7 . The micro lathe according to claim 1 , wherein the strokes of the multi-axis precision moving table in the x and y directions are ±20 mm, the travel in the z direction is 10 mm, and the movement accuracy is 1 μm. 8 . The micro lathe according to claim 1 , wherein the ER collet is equipped with a conical nut for clamping the workpiece by the ER collet. 9. The miniature lathe according to claim 1, wherein the sliding bearing is made of brass, and the main shaft is made of stainless steel. 10. The miniature lathe according to claim 1, wherein the motor controller of the stepper motor is placed in the external atmosphere of the FIB/SEM double-beam system, and is connected to the stepper motor through a flange to realize Motion control of the stepper motor.