JPS63216652A - Highly accurate metal cutting method - Google Patents

Abstract

PURPOSE:To secure machined form accuracy so easily without accumulating each part accuracy in a machine, by measuring a distance between a tool slide and the ground surface of a workpiece with a noncontact displacement gauge, displacing a tool rest on the basis of the signal, and controlling the infeed rate. CONSTITUTION:During revolution of a spindle 1, a tool slide 5 is moved in the X-axis direction along a guide 4, and cutting by a tool 8 takes place. At this time, a distance between the tool slide and the ground surface 3b of a workpiece 3 is measured by a noncontact displacement gauge 7 of an electrostatic capacity system or the like, and on the basis of this measuring signal, a control unit 18 generates an infeed rate control signal for cutting along the preset object form, displacing a tool rest 6 to some extent, thus control over an infeed rate is carried out. Thus, control accuracy in a relative positional relationship between the tool and the workpiece, namely, accuracy of finishing is securable simply and easily without accumulating each part accuracy in a machine.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a high-precision cutting method, and 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 parts such as aspherical metal mirrors, has the property that the relative positional relationship between the tool and the workpiece is extremely accurately transferred to the shape of the workpiece surface. , suitable for obtaining ultra-precise machined surfaces. in this case,
Accurately controlling the relative position of the tool and workpiece
This is the first condition for obtaining a highly accurate machined surface.

Conventionally, in order to meet this requirement, efforts have been focused on improving the motion accuracy of the main components of the lathe, namely the spindle and the tool slide. However, it is very difficult to improve the interlocking precision of these elements, and at the same time, thermal deformation of other elements that make up the lathe, such as the mechanical structure from the spindle to the tool slide, or workpiece fixtures, etc. It is also very difficult to sufficiently reduce the deformation caused by the load and the load, and as a result, with this method, it is difficult to control the relative positional relationship between the tool and the workpiece with sufficient accuracy, especially when changing the dimensions of the workpiece. This is extremely difficult when .

[Problems to be Solved by the Invention] The present invention improves the control accuracy of the relative positional relationship between the tool and the workpiece, that is, the machining shape accuracy, without relying on accumulating the accuracy of each part of the machine. It is intended to be obtained simply and easily by proceeding with processing while directly detecting it.

[Means and effects for solving the problem] In order to solve the above problems, the first high-precision cutting method of the present invention provides the following method: When cutting a high-precision machined surface using a cutting tool, A tool stand that can minutely control the depth of cut of the tool,
A non-contact displacement meter that can measure the distance between the tool slide and the machined surface of the workpiece is installed, and the tool stand is displaced based on the output signal of the displacement meter to perform cutting along a preset target shape. The feature is that the amount of cut is controlled.

In addition, in the second cutting method of the present invention, when cutting a high-precision machined surface using a cutting tool, a tool stand that can minutely control the amount of cut of the tool is placed on the tool slide, and the tool slide and the workpiece are placed on the tool slide. Two non-contact displacement meters are installed at intervals that can measure the distance to the workpiece surface, and the orientation change between the tool slide and the workpiece rotation axis is detected based on the output signals of both displacement meters. This method is characterized by displacing the tool rest while eliminating the influence of the above, and controlling the depth of cut so as to perform cutting along a preset target shape.

In the above method, cutting by the tool is performed by moving the tool slide along the guide while the spindle is rotating, and at this time, the non-contact displacement meter constantly measures the distance between the cut surface and the cut surface. Based on the output signal of this displacement meter, the position of the tool stand is controlled so as to perform cutting along a preset target shape.

The tool slide mentioned above may tilt with respect to the workpiece rotation axis during movement, but if this influence is large, measure the distance between the cut surface and the tool slide using two non-contact displacement meters. However, based on the outputs of these displacement meters, the distance between the tool slide and the workpiece rotation axis can be measured while removing the influence of changes in orientation.

When cutting is performed in this way, the control accuracy of the relative positional relationship between the tool and the workpiece, that is, the machining shape accuracy, can be improved by directly controlling the relative positional relationship between the tool and the workpiece, without relying on accumulating the accuracy of each part of the machine. It can be simply and easily enhanced by detection.

[Example] The configuration of a cutting device for carrying out the high-precision cutting method of the present invention will be described below with reference to the drawings.

FIG. 1 shows the configuration of a cutting device in which the processing method of the present invention is applied to face cutting using a lathe. In this cutting device, a workpiece 3 is attached to the main shaft 1 of the lathe via a workpiece fixture 2. The workpiece 3 is rotated around the workpiece rotation axis 3a by the main shaft l. On the other hand, the tool slide 5 that moves along the guide 4 includes a small displacement tool stand 6 that can minutely control the amount of cut, and a non-contact displacement tool that can measure the distance in the cutting direction between the tool slide 5 and the workpiece surface 3b. A total of 7 tools are attached, and a tool 8 is attached to the tip of the minute displacement tool stand 6.

The minute displacement tool stand 6 can have a structure as shown in FIG. 2, for example. The micro-displacement tool stand 6 shown in the same figure connects four rigid side members 11 at thin elastic bending parts 12 located at the four corners, and is made of an elastic metal material to allow elastic deformation. The tool 8 is fixed on the guide member 10, and a piezoelectric element 14 is provided between the convex portions 13.13 from the upper and lower side members 11.11 to move the tool in parallel. A non-contact displacement meter 15 is installed at one end of 8 to detect the displacement of the tool.
are set up opposite. Therefore, by changing the distance between the protrusions 13.13 by controlling the piezoelectric element 14, the position of the tool 8 in the cutting direction can be controlled, and the position can be detected by the displacement meter 15. .

In the lathe described above, cutting with the tool 8 is performed by moving the tool slide 5 in the X direction along the guide 4 while the main shaft is rotating. At this time, the non-contact displacement meter 7 is positioned so as to face the cut surface 3b that has already been cut, and constantly measures the distance between it and the already cut surface of the workpiece during cutting.

As the displacement meter 7 and the displacement meter 15 for detecting the amount of displacement of the tool, a capacitance type, eddy current type, or optical type displacement meter can be used.

A control device 18 connected to the minute displacement tool stand 6 and the non-contact displacement meter 7 generates a depth of cut control signal for cutting along a preset target shape based on the output signal of the non-contact displacement meter 7. The tool stand 6 is generated by the control signal.
The control device 18 controls the amount of cut by displacing the .

Now, let the displacement output at time E be 5(t), the control input to the tool rest 6, that is, the depth of cut of the tool rest 6, be u (t), and the shape of the cut workpiece 3 be z (X) Expressed as. Here, X is a coordinate taken from the center in the radial direction, and 2 is a coordinate taken in the thickness direction.

It is assumed that during cutting, the tool slide 5 is moving in the X direction at a constant speed V, and the tool is at the position x=vt at time. During the movement, the tool slide 5 rotates around the workpiece rotation axis 3a.
Assuming that there is no change in the inclination angle, the following relationship holds true.

s (t) = −z (x −v τ) + Z (
X) + u (t) Φ... (1) distance in the ° direction).

Assuming that the shape of the target workpiece 3 is 20 (X), the depth of cut u (t) to be controlled is: u (t) = 5 (t) +z (v (t - τ) )
-Zo(x)・Fist・(2) If Z (X)=20(+), the tool 8 and workpiece 3 due to motion errors of the spindle 1 and tool slide 5, deformation of the machine structure, etc. The shape of the workpiece can be made to match the desired value regardless of control errors in the relative positional relationship between the two.

However, during cutting, the shape Z (X) of the workpiece 3 needs to be known in advance in the range -Vτ≦X≦0. However, in this short section, even if cutting is performed using the normal method without the above-mentioned control, the influence of disturbance on the resulting surface shape is considered to be sufficiently small, so the cut surface can be used as a reference with a known shape. It can also be a face. In this case, by using the reference surface as the gg primary reference surface and cutting according to the control law of equation (2), the 0
The shape of the workpiece 3 obtained in the interval ≦X≦Vτ can be determined. By using the surface thus obtained as a secondary reference surface and performing similar control, the shape of the workpiece 3 can be determined even in the primary section Vτ≦X≦2vτ.

In this way, by starting from the primary reference surface with a known shape and performing cutting while performing the above control,
The shape Z (X) of the workpiece 3 can be maintained over a wide area without being affected by undesired relative positional errors between the tool 8 and the workpiece 3 due to expansion and contraction of the spindle l, deformation of the machine structure, meandering of the tool slide 5, etc. can be made to match the desired value 20(X).

Next, an example of an experiment related to the present invention conducted using the above-mentioned apparatus will be explained.

Figure 4 shows that during face cutting of aluminum alloy, an external force is applied to the tool slide 5 in the direction of separating it from the workpiece 3, deforming the machine structure, and as a result, there is a gap between the bundled tool slide and the workpiece. This figure shows the effect of a distance change on the shape of the cut surface of the workpiece 3, and therefore, control based on the present invention is not performed. In this experiment, as shown in the figure, the machine structure was deformed to the extent that convex portions corresponding to 0.2 m, 0.5 m, and 1.0 m were formed on the machined surface. giving.

On the other hand, FIG. 5 shows a state in which the deformation of the cut surface is removed by the control based on the present invention in the case of 0.5 gm described above.

The tool slide 5 in the device example shown in FIGS. 1 and 2 described above may tilt with respect to the workpiece rotation axis 3a during movement. Furthermore, as the spindle 1 rotates, there is a change in the orientation of the rotation axis (angular motion), which also causes a change in the orientation between the tool slide 5 and the workpiece rotation axis 3a. In the configuration shown in FIG. 1, it is not possible to distinguish between this change in orientation and a change in the distance between the tool slide 5 and the workpiece 3.

When the influence of such a change in orientation between the tool slide 5 and the workpiece rotation axis 3a is large, it is effective to use a tool slide 25 as shown in FIG. 3. The tool slide 25 shown in the figure has two non-contact displacement meters 27a and 2 that measure the distance between the cut surface of the workpiece 23 and the tool slide 25.
7b from the tool 28 in two different positions d I + d
2, and based on the outputs of these displacement meters 27a and 27b, the distance between the tool slide 5 and the workpiece rotation axis 3a is measured while removing the influence of changes in orientation. However, the other configurations are substantially the same as the example of the apparatus shown in FIG.

If the outputs of the displacement meters 27a and 27b in the example of the device shown in FIG. 3 are 51(t) and 52(t), and the tilt angle of the tool slide 25 is θ, then 51(t) = u (t) + z (x) −z
(x-d+) -d+θ52(t) = u (t)
+ z (ri −z (x−d2) −d2θ holds, and from this, −51(t) + 52(t) ) is obtained.

Here, −d2(z (x−d+)+5t(t))] −Z
If we set o(x), then Z (K) −Zo(x),
As in the case of the embodiment shown in FIG. 1, a cut surface having a desired shape can be obtained.

Although the high-precision cutting method described above has been explained using front cutting using a lathe as an example, 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 detailed 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 workpiece, that is, the machining accuracy, is determined by the cumulative accuracy of each part of the machine. This can be simply and easily obtained by proceeding with machining while directly detecting the relative positional relationship between the tool and the workpiece.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of an apparatus for carrying out the high-precision cutting method according to the present invention, Fig. 2 is a side view of a micro-displacement tool stand in the above-mentioned apparatus, and Fig. 3 is an illustration of the space between the tool slide and the workpiece rotation axis. A configuration diagram of another example of equipment that can respond to changes in the orientation of
FIGS. 4 and 5 are diagrams showing the results of experiments related to the present invention. 3.23@・Workpiece, 5.25-・Tool slide, 6
・Kai tool stand, ? , 27a, 2? b*m displacement meter,
8.28...Tools, 18.@Control equipment. Figure 1 R Figure 2

Claims (1)

[Claims] 1. In cutting a high-precision machined surface using a cutting tool, there is a tool stand on the tool slide that can minutely control the depth of cut of the tool, and a distance between the tool slide and the already machined surface of the workpiece. A non-contact displacement meter capable of measuring the displacement meter is provided, the tool rest is displaced based on the output signal of the displacement meter, and the depth of cut is controlled so as to perform cutting along a preset target shape. Precision cutting method. 2. When cutting high-precision machined surfaces using cutting tools, two tools are installed on the tool slide: a tool stand that can minutely control the depth of cut of the tool, and a device that can measure the distance between the tool slide and the already machined surface of the workpiece. non-contact displacement meters arranged at intervals are provided, and the tool rest is displaced based on the output signals of both displacement meters while eliminating the influence of changes in orientation between the tool slide and the workpiece rotation axis. , a high-precision cutting method characterized by controlling the depth of cut so as to perform cutting along a preset target shape.