JPH0729258B2 - High precision cutting method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a high-precision cutting method, and more particularly to a cutting method suitable for obtaining an ultra-precision machined surface.

[Prior Art] Ultra-precision diamond turning, which is used to manufacture optical components such as aspherical metal mirrors, has the property that the relative positional relationship between a tool and a workpiece is extremely accurately transferred to the workpiece surface shape. Suitable for obtaining ultra-precision machined surface. in this case,
Accurate control of the relative positional relationship between the tool and the workpiece
This is the first condition for obtaining a highly accurate machined surface.

In the past, in order to satisfy this condition, efforts have been made to improve the movement accuracy of the main components of the lathe, that is, the spindle and the tool slide. However, it is very difficult to improve the motion accuracy of these elements, and at the same time, other elements that make up the lathe, for example, the mechanical structure between the spindle and the tool slide, or the thermal deformation of the workpiece fixture, etc. It is also very difficult to sufficiently reduce the deformation due to load or load, and as a result, it is difficult to control the relative positional relationship between the tool and the workpiece with sufficient accuracy in such a method, especially in the dimension of the workpiece. Very difficult when is large.

[Problems to be Solved by the Invention] The present invention provides a control positional accuracy of a relative positional relationship between a tool and a work piece, that is, a machining shape accuracy, a relative positional relationship between the tool and the work piece without accumulating accuracy of each part of the machine. The present invention intends to obtain easily and easily by advancing processing while directly detecting.

Further, as described above, in advancing machining while directly detecting the relative positional relationship between the tool and the workpiece, the present invention can be applied even when the influence of the orientation change between the tool and the workpiece is large. It is intended to obtain a high precision cutting method.

[Means and Actions for Solving Problems] In order to solve the above-mentioned problems, the high-precision cutting method of the present invention uses a cutting tool to cut a tool on a tool slide in cutting a high-precision processing surface using a cutting tool. Provided with a tool base that can control the amount minutely, and a non-contact displacement meter that is arranged at two intervals that can measure the distance between the tool slide and the work surface of the workpiece, and output signals of both displacement meters It is characterized by displacing the tool base by eliminating the influence of the azimuth change between the tool slide and the workpiece rotation axis based on the above, and controlling the cutting amount so as to perform cutting along a preset target shape. It is a thing.

In the above method, the cutting by the tool is performed by moving the tool slide along the guide during the rotation of the spindle, and at this time, the non-contact displacement gauge always measures the distance between the work surface and the already cut work surface. The position of the tool base is controlled so as to perform measurement and perform cutting along a preset target shape based on the output signal of the displacement meter.

The tool slide may tilt with respect to the workpiece rotation axis during movement, but the distance between the already-cut surface and the tool slide is measured by two non-contact displacement gauges, and the output of those displacement gauges is measured. Since the distance measurement is carried out on the basis of, the effect of the orientation change between the tool slide and the workpiece axis of rotation is eliminated by simple means.

When the cutting is performed in this way, the control accuracy of the relative positional relationship between the tool and the work, that is, the machining shape accuracy, does not depend on the accumulation of the accuracy of each part of the machine, but the relative position including the orientation change between the tool and the work. It can be easily and easily enhanced by direct detection of relationships.

[Embodiment] With reference to the drawings, the configuration of a cutting apparatus for carrying out the high-precision cutting method of the present invention will be described below.

FIG. 1 shows the structure of a cutting apparatus applied to face cutting by a processing lathe that does not consider the influence of azimuth change, which is the premise of the present invention. In this cutting apparatus, a work piece 3 is attached to a main shaft 1 of a lathe via a work piece mounting tool 2, and the work piece 3 is rotationally driven by the main shaft 1 around a work shaft 3a. On the other hand, the tool slide 5 moving along the guide 4 has a minute displacement tool base 6 capable of minutely controlling the amount of cutting, and a non-contact displacement capable of measuring the distance between the tool slide 5 and the workpiece surface 3b in the cutting direction. A total of 7 is attached, and a tool 8 is attached to the tip of the micro-displacement tool base 6.

The micro-displacement tool base 6 can have a structure as shown in FIG. 2, for example. The micro-displacement tool base 6 shown in the figure has a thin-walled elastic bent portion in which four side members 11 having rigidity are located at four corners.
An elastic deformation guide member 10 is formed by connecting them at 12 and integrally forming them with an elastic metal material. The tool 8 is fixed on the guide member 10 and upper and lower side members are formed.
A piezo-electric element 14 for parallelly moving the convex portions 13 and 13 from 11, 11 is provided, and a non-contact displacement gauge 15 for detecting the displacement of the tool 8 is provided at one end of the tool 8 as a pair. . Therefore, when the interval between the convex portions 13 and 13 is changed by the control input to the piezoelectric element 14, the position of the tool 8 can be controlled in the cutting direction, and the position can be detected by the displacement meter 15. .

In the above lathe, cutting with the tool 8 is performed by moving the tool slide 5 along the guide 4 in the x direction while the spindle is rotating. At this time, the non-contact displacement gauge 7 is positioned so as to face the work surface 3b that has already been cut, and the distance between the work surface and the already worked work surface is constantly measured during cutting. As the displacement gauge 7 and the displacement gauge 15 for detecting the displacement amount of the tool, a capacitance type, an eddy current type, or an optical type displacement gauge can be used.

The control device 18 connected to the micro-displacement tool base 6 and the non-contact displacement meter 7 sends a cutting amount control signal for cutting along a preset target shape based on the output signal of the non-contact displacement meter 7. The tool table 6 is generated by the generated control signal.
Is controlled by displacing the cut amount, and the control unit 18 performs the following calculation.

Now, the displacement output at time t is s (t), the control input to the tool base 6, that is, the cut amount of the tool base 6 is u (t),
Further, the shape of the cut work piece 3 is expressed as z (x). Here, x is a coordinate in the radial direction from the center and z is a coordinate in the thickness direction.

It is assumed that the tool slide 5 is moving in the x direction at a constant velocity v during cutting and the tool is at the position x = vt at time t.
Then, assuming that the tool slide 5 does not change its inclination angle with respect to the workpiece rotation axis 3a during the movement, the following relationship is established.

s (t) = − z (x−vτ) + z (x) + u (t) ...
(1) where (D is the distance between the tool and the displacement gauge 7 in the x direction).

Let Z ₀ (x) be the target shape of the workpiece 3 and u (t) = s (t) + z {v (t−τ)} − Z ₀ (x ) ...
If (2), then z (x) ≡Z ₀ (x), and the control of the relative positional relationship between the tool 8 and the workpiece 3 caused by the motion error of the spindle 1 and the tool slide 5, the deformation of the mechanical structure, etc. The workpiece geometry can be matched to the desired value independent of the error.

However, at the time of cutting, the shape z (x) of the workpiece 3 needs to be known in advance in the section −vτ ≦ x ≦ 0. However, in this short section, it is considered that the influence of disturbance on the obtained surface shape is sufficiently small even if cutting is performed by the normal method without the control described above. It can also be a face. In this case, the reference surface is the primary reference surface,
By cutting according to the control rule of the equation (2), 0 ≦
The shape of the workpiece 3 obtained in the section of x ≦ vτ can be determined.
If the same control is performed using the surface thus obtained as the secondary reference surface, the shape of the workpiece 3 can be determined even in the next section vτ ≦ x ≦ 2vτ.

In this way, starting from the primary reference surface of known shape and performing the cutting process while performing the above control,
The work 3 shape z (x) is spread over a wide surface without being affected by an undesired relative positional error between the tool 8 and the work 3 due to expansion and contraction of the spindle 1, deformation of the mechanical structure, meandering of the tool slide 5, and the like. Can be matched to the desired value Z ₀ (x).

Next, an example of an experiment conducted using the above-mentioned device will be described.

FIG. 4 shows that in frontal cutting of an aluminum alloy, an external force is applied to the tool slived 5 in a direction away from the workpiece 3 to deform the mechanical structure, and as a result, the resulting force between the tool slide and the workpiece is increased. This shows the influence of the change in distance on the shape of the work surface of the workpiece 3, and therefore the above-mentioned control is not performed. In this experiment, as shown in the figure, the mechanical structure was deformed to such an extent that a projection corresponding to 0.2 μm, 0.5 μm, and 1.0 μm was formed on the surface to be cut.

On the other hand, FIG. 5 shows a state in which the deformation of the work surface is removed by the above control in the case of 0.5 μm described above.

The tool slide 5 in the apparatus example of FIGS. 1 and 2 described above may tilt with respect to the workpiece rotation axis 3a during movement. Further, there is a change in the orientation of the rotary shaft (angular motion) associated with the rotation of the main shaft 1, which also causes a change in the orientation between the tool slide 5 and the workpiece rotary shaft 3a. In the configuration of FIG. 1, it is impossible to distinguish this change in orientation from the change in the distance between the tool slide 5 and the workpiece 3.

In order to eliminate the influence of the azimuth change between the tool slide 5 and the workpiece rotating shaft 3a, in the processing apparatus to which the high precision cutting method of the present invention is applied, the tool slide as shown in FIG. 25 is used. Tool slide shown in the figure
25, two non-contact displacement meter 27a for measuring the distance between the existing cutting surface and the tool slide 25 of the workpiece 23, the 27b, arranged at a position d _1, d ₂ of two different from the tool 28, their displacement meter Based on the outputs of 27a and 27b, the distance between the tool slide 5 and the workpiece rotation axis 3a is measured while eliminating the influence of the change in orientation, but other configurations are measured by the device example of FIG. It is substantially the same as the case of.

The output of the displacement gauges 27a and 27b in the device example of FIG.
₁ (t), s ₂ (t) and the tilt angle of the tool slide 25 is θ, then s ₁ (t) = u (t) + z (x) −z (x−d ₁ ) −d ₁ θ s ₂ (T) = u (t) + z (x) −z (x−d ₂ ) −d ₂ θ holds, and from this, To get

here, In other words, Z (x) ≡Z ₀ (x), and a desired surface to be machined can be obtained as in the case of the embodiment shown in FIG.

The high-precision cutting method described above has been described by exemplifying front cutting with a lathe, but the present invention is not limited to such front grinding, and can be similarly applied to, for example, cylindrical grinding. .

[Effects of the Invention] As described in detail above, according to the high-precision cutting method of the present invention, the control accuracy of the relative positional relationship between the tool and the work, that is, the processing accuracy, does not depend on the accumulation of the accuracy of each part of the machine. By directly detecting the relative positional relationship between the tool and the workpiece and proceeding with the machining, it can be easily and easily obtained.

[Brief description of drawings]

FIG. 1 is a block diagram of an apparatus for carrying out a high-precision cutting method that does not consider the influence of azimuth change, which is the premise of the present invention, FIG. 2 is a side view of a micro-displacement tool table in the apparatus, and FIG. 3 is a tool. FIG. 4 is a schematic view of an essential part of an example of an apparatus for carrying out the present invention, which is adapted to cope with a change in orientation between a slide and a workpiece rotation axis, and FIGS. 4 and 5 show experiments by the apparatus of FIGS. 1 and 2. It is a diagram showing the results of. 3,23 …… Workpiece, 5,25 …… Tool slide, 6 …… Tool stand, 7,27a, 27b …… Displacement gauge, 8,28 …… Tool, 18 …… Control device.

Claims (1)

[Claims] 1. When cutting a high-precision machined surface using a cutting tool, it is possible to measure the distance between the tool slide and the work surface to be machined, and the tool base that can finely control the amount of cutting of the tool on the tool slide. And a non-contact displacement gauge arranged at two intervals, and based on the output signals of both displacement gauges, the influence of the azimuth change between the tool slide and the workpiece rotation axis is eliminated and the tool base is removed. A high-precision cutting method characterized in that the cutting amount is controlled so as to perform cutting along a preset target shape by displacing the.