JPS63295173A - Aspherical surface processing machine - Google Patents

Abstract

PURPOSE:To create a figure in high precision by performing three-axis control so that the rotary shaft of a tool is identical to the normal to the aspherical surface of a work, controlling the gap between the work and the tool, and performing processing while this gap is filled with the processing liquid. CONSTITUTION:Three-axis control is made with an X-axis linear location mechanism 4, a Z-axis liner location mechanism 15, and a theta-axis rotational location mechanism 16 so that the rotary shaft of a tool 14 is identical with the normal to the aspherical surface of a work 1. The gap between the work 1 and tool 14 is finely controlled by a control mechanism 17 on the basis of measurements given by a gap sensor 30, and processing is performed while the gap is filled with a processing liquid 33 with abrasive grains. This accomplishes contactless processing, and performing processing with the gap measured enables creation of high precision figure.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is applicable to high-precision mirror finishing of molds used for molding aspherical lenses made of plastic or glass, and aspherical mirrors made of hard brittle materials such as ceramic or glass. , relates to an aspheric processing machine for processing lenses.

Conventional technology Conventionally, high-precision mirror finishing of molds used for molding aspherical lenses involves cutting and grinding the shape using an ONO lathe, curve generator, etc., and then mirror finishing using a lens polisher or by hand. There is a processing method that uses an ultra-precision diamond lathe to achieve shape processing and mirror finishing at the same time (Ken Hirai et al.: Mold processing technology for aspherical plastic lenses, National Techni.
cal Report, 31.5 (1985) 632
).

On the other hand, cemented carbide and ceramics are used as materials for molds for molding glass lenses, but high-precision, high-speed rotation is required to process the aspherical shapes of molds, mirrors, and lenses made of these hard and brittle materials. There is a processing method in which the diamond grindstone is moved along the desired processing shape to process the shape, and it also attempts to process it into a mirror surface (Ueda et al., Proceedings of the 1986 Japan Society of Precision Machinery Autumn Conference Academic Lectures, PO2) )
.

Since the processing method described above is a fixed position cutting method, the processing accuracy matches the accuracy (positioning, runout, etc.) of the processing machine. Therefore, with a normal machine configuration, the accuracy limit is on the order of several microns, and in order to obtain submicron accuracy, high-precision positioning is required by incorporating hydrostatic bearings and a laser length measurement feedback system into the machine configuration. There is a need to do.

Problems to be Solved by the Invention However, the above conventional example has the following problems.

(1) Machining by cutting and grinding alone results in roughness of the processed surface, which is on the order of microns, and the shape accuracy is also on the order of microns. High-precision processing such as ultra-precision diamond cutting and diamond fine grinding achieves a mirror surface with surface roughness and shape accuracy of submicron or less, but there are problems such as tool feed marks remaining, and in both cases the final finish is difficult to achieve. is necessary.

(2) Due to the problem described in (1) above, the surface roughness is processed on the order of several nanometers by performing the final polishing process, but due to this process, it is impossible to make the shape better than the previously processed surface. It often collapses to something like this or even less.

Therefore, the present invention can create a shape with high precision, perform mirror finishing of an aspherical surface on the submicron order, easily realize the processing of micro optical components, and further The present invention aims to provide an aspherical surface processing machine that can easily process highly hard and brittle materials that have been difficult to process with high accuracy.

Means for solving the problems and technical means of the present invention for solving the above problems include a work rotation mechanism that holds and rotates the work,
A processing tool that processes the workpiece, a drive mechanism that holds and rotates the processing tool, a linear positioning mechanism that relatively positions the workpiece and the processing tool in two orthogonal axes, and a rotation axis of the processing tool. a rotational positioning mechanism that rotates the workpiece within the coordinate plane of the orthogonal two axes, a gap sensor that measures the gap between the workpiece and the processing tool, and a control mechanism that controls the gap between the workpiece and the processing tool based on commands from the gap sensor. and means for supplying a machining liquid mixed with abrasive grains between the workpiece and the machining tool.

For production The effects of the above technical means are as follows.

In other words, the three axes are controlled using a two-axis linear positioning mechanism and a rotational positioning mechanism so that the rotation axis of the processing tool matches the normal direction of the aspherical shape of the workpiece, and the gap between the workpiece and the processing tool is measured using a gap sensor. A control mechanism performs extremely fine control based on measurements, and a machining liquid mixed with abrasive particles is interposed between the workpiece and the machining tool to achieve non-contact machining and high-precision mirror machining. In addition, by performing machining while measuring the gap between the workpiece and the machining tool, high-precision shape creation can be achieved.

EXAMPLES Hereinafter, examples of the present invention will be described with reference to the drawings. FIG. 1 is a partially cutaway front view showing an aspheric surface processing machine according to an embodiment of the present invention.

As shown in FIG. 1, a workpiece 1 is fixed on a rotary table 2 by a chuck 3. The rotary table 2 is rotatably supported by an X-axis linear positioning mechanism 4, and is moved and positioned in the X-axis direction (horizontal direction) by the X-axis linear positioning mechanism 4. To explain the details, a movable base 6 is supported on a fixed base s via a rolling bearing 7 so as to be movable in the X-axis direction. Movable stand 6
A ball screw nut 8 is attached to the lower side of the ball screw, and a screw shaft 9 of the ball screw screwed into the nut 8 is rotatably supported by the fixed base 6, and the screw shaft 9 is supported by the fixed base 5. It is linked to the motor 1o.

The movable table 6 is formed into a frame shape, and a small diameter portion 2a at the middle portion of the rotary table 2 is fixed and rotatably supported in a hole 6a in the upper surface. Rotary table 2 is motor 1
Rotated by 1. This motor 11 is composed of a stator 12 and a rotor 13. The stator 12 is supported at the bottom of the movable table 6, and the rotor 13 is attached to the lower end of the rotary table 2. Therefore, by rotating the screw shaft 9 by driving the motor 10, the movable table 6, rotary table 2, workpiece 1, etc. can be moved in the X-axis direction with respect to the fixed table 6 via the nut 8.

The processing tool 14 is aligned with the normal direction of the aspherical shape of the workpiece 1 by a Z-axis linear positioning mechanism 16 and a θ-axis rotational positioning mechanism 16, and the distance from the workpiece 1 is controlled by a control mechanism 17. To explain the details, a movable plate 18 is supported by a frame-shaped guide column 17 via a rolling bearing 19 so as to be movable in the Z-axis direction (vertical direction). The device is moved in the Z-axis direction. A disk 22 is rotatably supported by the movable plate 18 and rotated by a driving means (not shown). Disk 2
A guide member 23 is attached to the guide member 2, a holding frame 24 is supported on the guide member 23 so as to be linearly movable via a rolling bearing 26, and a spindle 26 having the processing tool 14 is supported on the holding frame 24. , the spindle 26 and the processing tool 14 are rotated by the drive of the motor 27. The holding frame 24, spindle 26, processing tool 14, etc. are powered by a motor 28,
The processing tool 14 is moved along the guide member 23 by a driving means such as a screw shaft 29 so that the tip of the processing tool 14 is directed approximately to the center of the disk 22.

The gap between the workpiece 1 and the processing tool 14 is detected by the gap sensor 30 based on the capacitance generated between the two.

A machining fluid 33 (see FIG. 2) mixed with abrasive grains 32 is stored in the container 31, and the machining fluid 33 mixed with abrasive grains 32 is supplied to the workpiece 1 and the machining tool 14 through a supply port 34 communicating with the container 31. will be supplied between.

Next, the operation of machining an aspherical surface according to the above embodiment will be explained.

Since the aspherical shape is expressed as a quadratic function, the aspherical surface of the workpiece is determined by determining the positions of both the X and 2 axes of the workpiece 1 and the processing tool 14 using the Shapes can be created. In the present invention, the rotation axis of the processing tool 14 is set to the above-mentioned orthogonal X, so that one point of the processing tool 14 is always the point where processing is performed.
In addition to positioning the processing tool 14 with respect to the workpiece 1 by the θ-axis rotation positioning mechanism 16 within the Z2-axis coordinate plane,
Controls the axis. Then, when the workpiece 1 and the processing tool 14 are relatively positioned, and the motors 11 and 27 are driven to rotate the workpiece 1 and the processing tool 14 to machine an aspherical shape, the workpiece 1 is actually pre-processed. Since there is an error in the shape, there is a deviation in the gap between the workpiece 1 and the processing tool 14 at each processing position. Therefore, this gap is constantly measured by the gap sensor 30, and the control mechanism 1
7, the machining tool 14 is moved in the θ-axis direction and the gap is controlled, thereby making it possible to control the shape.

FIG. 2, which explains the shape control by the gap control in more detail, is an enlarged view of the workpiece 1 and the processing tool 14 viewed from the center of the workpiece 1 to explain the processing operation. In FIG. 2, the workpiece 1 is moving from right to left due to rotation. The machining tool 14 is positioned on the workpiece 1 with a gap of several microns, and a machining fluid 33 containing abrasive grains 32 exists between the two. As the workpiece 1 rotates, the machining fluid 33 causes a flow as shown by the arrow, and the abrasive grains 32 in the machining fluid 33 collide with the workpiece 1 to scrape the workpiece 1, thereby progressing machining. The main factors that contribute to the speed of progress of this machining include the rotational speed of the workpiece 10 and the gap length, and other factors include the machining tool 14
The rotation speed, abrasive grain size, etc. can be mentioned. When the gap is made smaller, the machining speed increases, and when the gap is made larger, the machining speed becomes slower.

FIG. 3 shows an example of gap control for the front shape of the workpiece 1. FIG. 3 (,) shows the previous shape of the workpiece 1, and the vertical axis represents the error from the desired shape. The figure (b) shows the output of the gap sensor 3o when the gap sensor 3o is positioned to have a constant gap, the vertical axis is the gap length, and the output shape is opposite to that in the figure (a).

Even if machining is continued in this state, deviations can be removed. However, in order to process time efficiently.

The gap is controlled as shown in FIG. 4(c). The gap length g is a distance at which no machining progresses. The horizontal axis of Fig. 3 (a), (b), and (C) used above can be considered to be the radial direction of the workpiece 10 or the circumferential direction within the same radius. The machining tool 14 is controlled in three axes, the gap between the workpiece 1 and the machining tool 14 is extremely finely controlled based on the measurement of the gap sensor 30, and a machining fluid 33 mixed with abrasive grains 32 is provided between the workpiece 1 and the machining tool 140.
The work 1 and the processing tool 14 are connected to the motors 11 and 2.
By rotating with the drive of 7, high-precision mirror finishing can be performed in a non-contact manner.

Effects of the Invention In short, according to the aspheric processing machine of the present invention, three-axis control is performed using a two-axis linear positioning mechanism and a rotational positioning mechanism so that the rotational axis of the processing tool is aligned with the normal direction of the aspherical shape of the workpiece. However, the gap between the workpiece and the processing tool is controlled by a control mechanism based on sensor measurements, and processing is performed by interposing a processing fluid containing abrasive particles between the workpiece and the processing tool. In this way, it is possible to realize non-contact machining of a workpiece using a machining tool, and by minutely controlling the gap between the workpiece and the machining tool, highly accurate mirror machining can be performed on any material.

In addition, by performing machining while measuring the gap between the workpiece and the machining tool, it is possible to perform corrective machining for shape errors on the entire surface of the workpiece, and it is possible to create a highly accurate shape with good concentricity. In addition, since the shape is created by three-axis control as described above, it is possible to process any shape, and in particular, it is possible to easily realize high-precision machining of micro optical components, which has been difficult in the past.

[Brief explanation of the drawing]

Figures 1 to 3 show an aspherical surface machining machine according to an embodiment of the present invention, where Figure 1 is a partially cutaway front view of the whole, and Figure 2 is a machining machine showing a workpiece and a processing tool viewed from the center of the workpiece. The enlarged views for explaining the operation and FIGS. 3(a) to 3(c) are diagrams for explaining processing control. 1... Workpiece, 2... Rotary table, 4...
・X-axis linear positioning mechanism, 11...Motor, 14...
・Processing tool, 15...Z-axis linear positioning mechanism, 1e・
... θ-axis rotation positioning mechanism, 17... control mechanism, 3o
... Gap sensor, 32 ... Abrasive grain, 33 ... Machining liquid. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
figure

Claims (1)

[Claims] A workpiece rotation mechanism that holds and rotates a workpiece, a processing tool that processes the workpiece, a drive mechanism that holds and rotates the processing tool, and a drive mechanism that rotates the workpiece and processing tool relative to each other in two orthogonal axes directions. A linear positioning mechanism for positioning, a rotary positioning mechanism for rotating the rotary axis of the machining tool within the coordinate plane of the two orthogonal axes, a gap sensor for measuring the gap between the workpiece and the machining tool, and a command from the gap sensor. An aspherical surface machining machine comprising: a control mechanism for controlling the gap between the workpiece and the machining tool; and means for supplying a machining fluid containing abrasive grains between the workpiece and the machining tool.