JPH03281138A - Mirror cutting equipment and its processed products - Google Patents

Abstract

PURPOSE:To conduct machining without producing a stepped part on a workpiece by forming a variable part of an elasticity recovering quantity on an elastic chuck so as to perform machining in accordance with machining power variation during machining without producing the stepped part on the workpiece. CONSTITUTION:A vacuum chuck 12, whose thickness of an inside periphery is L, that of an outside periphery is (l), and whose outside periphery side, wherein machining power particularly rear component power is decreased abruptly due to hindered discharge of chips at a side cutting edge part of a workpiece 2, is thinned in thickness, is bonded to and retained by a chuck base 13. The thickness (l) at the outside periphery part of the vacuum chuck 12 is determined in such a way that a quantity of elasticity recovering on the vacuum chuck caused by the abrupt decrease of machining power at the outside periphery part of the workpiece 2 is not exceeding a required machining precision. Even when the machining power is decreased abruptly at the outside end part of the workpiece 2, since the elasticity recovering quantity of the vacuum chuck 12 is not exceeding roughness of a machined surface, specular surface machining on the workpiece 2 can be conducted without producing a stepped part on the machined surface.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a mirror cutting device and its processed products, and is particularly suitable for mirror-cutting the surface of, for example, a magnetic disk substrate without creating a step. The present invention relates to a mirror cutting device and mirror cutting products manufactured using the same.

[Conventional technology]

In the conventional mirror cutting device, for example,
As described in Publication No. 30, a workpiece such as a computer disk substrate is attracted to a vacuum chuck and rotated, and the non-adsorbed side is processed with a cutting tool. One side was adsorbed to a vacuum chuck whose shape almost matched the warp caused by the process, and the other side was cut.

[Problem to be solved by the invention]

In the above-mentioned conventional technology, no consideration is given to cutting force fluctuations occurring at the outer periphery of the workpiece, especially fluctuations in back force, which is a force in the cutting direction that affects machining accuracy. There was a problem in that the chuck surface that holds the object recovers elastically, changing the depth of cut of the tool and creating a step in the workpiece.

FIG. 4 is a diagram of a machined surface and a cross-sectional curve of a stepped portion that occurs when mirror-cutting an aluminum alloy, and FIG. 5 is an explanatory diagram showing the mechanism of occurrence of an outer circumferential step when cutting the outer circumferential portion of a workpiece.

The diagram of the machined surface shown in Fig. 4 corresponds to an enlarged photograph of the step on the outer periphery of the workpiece (hereinafter referred to as the outer periphery step) using a differential interference microscope, and the cross-sectional curve shows the cross-sectional shape of the outer periphery step. It is something.

As shown in FIG. 4, it can be seen that the outer circumferential step is a step of approximately 0.2 μm that occurs approximately 1.3 mm (corresponding to the blade width of the tool) inward from the outermost circumference of the workpiece. If a step as described above exists on a mirror-cut workpiece, for example, a magnetic disk substrate, a variation in film thickness occurs when a magnetic film is coated on the substrate, resulting in variation in the output signal of the magnetic disk.

The inventors have clarified through experiments the cause of the above-mentioned outer circumferential step difference.

Figure 5 shows the mechanism by which the outer periphery level difference occurs.
FIG. 2 is a sectional view of the tool 1 being vacuum-adsorbed onto the chuck 12 and rotated to move the tool 1 in the tool feeding direction shown by the arrow for cutting.

When machining both sides of the workpiece 2, the chuck 1 that holds the workpiece 2 is used to prevent scratches on the first cut surface.
2 is generally made of an elastic body made of soft 3' material such as urethane rubber, and the chuck 12 is held on a chuck base 13.

On the other hand, the inventors' experiments revealed that the thrust force during cutting of the workpiece 2 can be divided into the following two types. That is, 1) Workpiece - Back force F generated at the side cutting edge of the tool 1 that discharges thick chips 14 corresponding to the feed rate f of the rotating tool
N% 2) Back force F9 generated at the front cutting edge of the tool where the depth of cut is very small.

The values of FN and FN' vary depending on the setting conditions of the tool, the state of wear, the cutting conditions, the material of the workpiece, etc., but according to the inventors' experiments, usually F, = 1. ON.

F, '#ON level. Therefore, at the outermost periphery of the workpiece 2, the cutting force is 1. It is considered that the cutting speed suddenly decreases from ON to ON, the chuck 2 made of a soft material recovers elastically, and the depth of cut becomes larger than the predetermined depth of cut d by Δ, causing a step on the outer periphery on the machined surface.

Here, a point 4 on an infinite flat plate supported by an elastic body Consider a model in which a concentrated weight is added to .

At this time, the displacement Δ' at a distance χ from the load point is 1,
The maximum value Δ of Δ′ is given by Pi″ Δ=−T3

Here, P: load, E: Young's modulus of the plate, h: thickness of the plate, C: Poisson's ratio E' of the plate, Young's modulus of the elastic body, and the thickness of the elastic body.

Therefore, the rubber hardness of an Al plate with a thickness of 1.9 mm is 90.
Supported with urethane rubber with a thickness of about 5.0 m, 1.
When cutting with ON cutting force, P=1. ON, E=7.
000kg/mm2. h=1.9mm, ν=0.3
5. l=5.0mm.

E' = 4.0 kg/mm2, and the displacement of the load point △c becomes △ = 0.207 μm.

This agrees well with the actual measured value of the outer circumferential step shown in FIG.

The present invention has been made in order to solve the problems of the prior art described above, and the chuck that holds the workpiece recovers elastically even if the cutting force, especially the thrust force, fluctuates during mirror cutting of the workpiece. The object of the present invention is to provide a mirror cutting device that can perform cutting without creating a level difference in a workpiece by varying the surface area of the workpiece, and a mirror cutting product manufactured using the same.

[Means to solve the problem]

In order to achieve the above object, a mirror cutting device according to the present invention has a configuration including a main shaft to which an elastic chuck is attached for holding a workpiece, a motor for rotationally driving the main shaft, and a tool holder for holding a cutting tool. and a means for moving the tool holder in the axial direction and perpendicular direction of the main spindle, the mirror cutting device is capable of cutting a workpiece without creating a step in response to fluctuations in cutting force during cutting. The chuck is provided with a portion where the amount of elastic recovery varies so that the amount of elastic recovery can be varied.

More specifically, the portion where the amount of elastic recovery of the chuck fluctuates is due, in part, to the fact that the chuck that holds the workpiece is formed to be thinner at least in the portion where the cutting force suddenly decreases; One of these is that the chuck that holds the workpiece has a Young's modulus that is larger than other ranges, at least in the range where the cutting force sharply decreases.

[Effect]

According to the above technical means, the thickness of the chuck is thinner in the part where the cutting force suddenly decreases, and even if the cutting force suddenly decreases during cutting in this part, the amount of elastic recovery of the chuck can be reduced. can.

If the amount of elastic recovery is set below the cut surface roughness obtained by mirror cutting, even if the depth of cut changes during cutting, it will be below the cut surface roughness, and no steps will occur in the workpiece.

Furthermore, if a material with a high Young's modulus is used for the chuck in the portion where the cutting force suddenly decreases, even if the cutting force suddenly decreases during cutting in this portion, the amount of elastic recovery of the chuck can be reduced.

・ 7 ・ As a result, even if the depth of cut changes during cutting, the roughness of the cut surface will not exceed the roughness of the cut surface, and no steps will occur on the workpiece.

〔Example〕

Embodiments of the present invention will be described below with reference to FIGS. 1 to 3.

FIG. 1 is a detailed sectional view showing a workpiece holding state of a mirror cutting device according to an embodiment of the present invention, and FIG. 2 is a perspective view of the mirror cutting device according to an embodiment of the present invention.

First, the configuration of the mirror cutting device will be explained.

The mirror cutting device shown in FIG. 2 includes a main spindle device (hereinafter simply referred to as the main spindle) 3 to which a vacuum chuck 12 for suctioning and holding a workpiece 2 is attached via a chuck base 13, and a main spindle 3 that rotates the workpiece 2. The main shaft motor 4 is connected to the bed 9.
Fixed on top. Further, a table 6 is provided which can slide only in a direction perpendicular to the rotational axis of the main spindle 3 (tool feeding direction). This table 6 is driven by a feed motor 8.
The rotation of the slider of the table 6 is transmitted directly through the feed screw.
8. It converts it into linear motion. On table 6, spindle 3
A tool rest 5 related to a tool holder that can slide in a direction parallel to the rotation axis (in the cutting direction) is equipped. This tool rest 5
This drive converts the rotation of the feed motor 7 into linear movement of the slider of the tool post 5 via a feed screw. A tool 1 is fixed on the tool rest 5. Also, on the tool post 5, there is a nozzle 1o for supplying pressure fluid such as cutting fluid and air.
is provided. A chip suction duct 11 is provided at a position facing this nozzle 10.

The details of the vacuum chuck 12 are shown in FIG.

As shown in FIG. 1, when the thickness of the vacuum chuck 12 on the inner circumference side is L1 and the thickness on the outer circumference side is 1, chips are not discharged at the side cutting edge of the tool 1, and the cutting force, especially the back force. The outer periphery side where the amount rapidly decreases is thinner, and is adhesively held on the chuck base 13. This chuck base 13 has mounting bolts 18
It is fixed to the main shaft 3 by.

The vacuum chuck 12 has concentric chuck grooves 16 formed on its chuck surface 15 for vacuum suction of the workpiece 2, and a vacuum suction path 17 communicating with these chuck grooves 16 formed in the chuck base 13. It is set up. This vacuum suction path 17 passes through the axis of the main shaft 3 and communicates with a vacuum suction pump (not shown).

The general operation of such a mirror cutting device is as follows.

That is, the tool rest 5 is moved on the inner circumferential side of the workpiece 2 held by a self-turning vacuum chuck 12 rotated by the spindle motor 4, the tool 1 is cut into the workpiece 2 by a predetermined amount, and then , table 6 is workpiece 2
The end face of the workpiece 2 is cut by moving it toward the outer periphery of the workpiece 2.

In relation to the above machining operation, the thickness 1 at the outer periphery of the vacuum chuck 12 is such that the amount of elastic recovery of the vacuum chuck 12 due to the sudden decrease in cutting force at the outer periphery of the workpiece 2 increases the required machining accuracy. You can set it as follows.

In order to determine the thickness 1 at the outer periphery of the chuck 12, a model where a concentrated load (cutting force) at one point is applied to an infinite flat plate supported by an elastic body, given by Δ'= and elastic recovery amount) is applied. think of.

The displacement Δ P1″ T ok χ of the load point distance χ is the maximum value Δ of Δ (For the vacuum chuck 12, Pl2 P Δ=□=□ 8D s, /'f5T...・・・・・・・・・・・・・・・(1)
h3 D-12(1-ν') ・・・・・・・・・・・・・・・・・・・・・・・・(
2) E'=- ・・・・・・・・・・・・・・・・・・・・・・・・・・・
・(3) becomes.

Here, P: E: hni Ji: E: 1: Load (cutting force), Young's modulus of plate (workpiece), The thickness of the plate (workpiece), Poisson's ratio of the plate (workpiece), Young's modulus of elastic body (chuck), Thickness of elastic chuck It is.

From equations (1), (2), and (3), the thickness 1 of the vacuum chuck is 64Δ”DE 1-P2 ・・・・・・・・・・・・・・・・・・
......(4). Therefore, using equation (4), 8 is the required processing.

It is sufficient to set it to 1 so that it is less than the accuracy.

- As an example, consider the case where an A1 plate with a thickness of 1.9 mm is chucked with urethane rubber having a rubber hardness of about 90 degrees (Young's modulus 4.0 kg/mm2) and mirror-cut. The cutting force at this time varies depending on machining conditions, tool shape, tool setting conditions, etc., but according to experiments conducted by the inventors, the cutting force averages 1. ON
The roughness of the cut surface obtained is 0.04μ
m Rmax. Therefore, Pl, ON, E=
7.000kg/mm2. h=1.9mm, ν
=0.35°E' ==4.0kg/mm2. Δ=
4 Xl, 0-5mmx, vacuum chuck thickness 1
1=64Kari4Xl0-')'X4559X4=o,
If t9 machining is 0.1” and 150.1.9 mm, even if the cutting force suddenly decreases from 1.ON to ON at the outer end of the workpiece 2, the amount of elastic recovery of the vacuum chuck 12 will depend on the roughness of the cut surface. The workpiece 2 can be mirror-cut without creating a step on the machined surface.

Further, the range of 150.19 mm may be the part where the cutting force during cutting of the workpiece 2 suddenly decreases. The thickness 1 may be reduced from the outer edge of the workpiece to the inner side by the blade width of the tool 1.

Therefore, when cutting from the outer periphery to the inner periphery, the opposite is true, and the thickness 1 may be reduced at least from the inner end of the workpiece to the outside by the blade width of the tool 1.

In addition, in this embodiment, only the part of the vacuum chuck 12 where the cutting force suddenly decreases is made thinner, so when the vacuum chuck 12 reaches the end of its life due to self-turning of the vacuum chuck 12, there is no need to replace the entire vacuum chuck. , only the thin parts need to be replaced.

Next, a second embodiment of the zero invention will be described with reference to FIGS. 2 and 3.

FIG. 3 is a detailed sectional view showing a workpiece holding state of a mirror cutting device according to another embodiment of the present invention.

In the figure, the same reference numerals as those in FIG. 1 are the same parts as in the previous embodiment, so the explanation thereof will be omitted.

The overall structure of the mirror cutting device of the second embodiment is the same as that shown in FIG. 2, and only the structure of the vacuum chuck 12A differs from that of the first embodiment.

A vacuum chuck 12A shown in FIG. 3 has a chuck 20 made of a material having a higher Young's modulus than the chuck 19 in the inner circumference fixed to the outer circumference where the cutting force, particularly the thrust force, decreases rapidly.

This allows the chuck 19 with a small Young's modulus to
can support most of the area without damaging it.

In addition, since the outer periphery of the workpiece 2 is supported by the chuck 20 having a large Young's modulus, the elastic recovery of the chuck 20 due to fluctuations in cutting force at the outer periphery can be reduced, and the workpiece 2 can be mirror-finished without creating a step. I can do it.

The Young's modulus E' of the chuck 20 may be set such that the amount of elastic recovery of the chuck 20 is less than or equal to the required processing accuracy. (
From formulas 1), (2), and (3), 1, IP' E-84DA”・・・・・・・・・・・・・・・・・・
......(5).

Consider the case where a 1.9 mm thick AJ plate is mirror-cut using a 3 mm thick vacuum chuck 12A. From equation (5), E
7-3 mowing “1)” -64,3kg/m”64X
4559
If the chuck 20 is made of a material such as PTFE, the workpiece 2 can be mirror-cut with a cutting surface roughness of 0.04 μm Rmax.

Furthermore, in the second embodiment, the chuck in the portion where the cutting force rapidly decreases is made of a material with a large Young's modulus, and the other portions are made of a soft material. Therefore, even when machining both sides of a workpiece, mirror cutting can be performed without damaging the surface of the workpiece.

〔Effect of the invention〕

As described above in detail, according to the present invention, even if the cutting force, particularly the thrust force, changes during mirror cutting of the workpiece, the elastic recovery of the chuck holding the workpiece is varied, It is possible to provide a mirror cutting device that can cut a workpiece without creating a step, and a mirror cutting product manufactured using the same.

[Brief explanation of drawings]

FIG. 1 is a detailed sectional view showing a workpiece holding state of a mirror cutting device according to an embodiment of the present invention, and FIG. 2 is a perspective view of the mirror cutting device according to an embodiment of the present invention. FIG. 3 is a detailed cross-sectional view showing the workpiece holding state of a mirror cutting device according to an embodiment of the present invention, and FIG. 4 is a diagram and cross-section of a machined surface of a stepped portion that occurs when mirror-cutting an aluminum alloy. The curve in FIG. 5 is an explanatory diagram showing the mechanism of occurrence of a step on the outer periphery during cutting of the outer periphery of a workpiece. 1...Tool, 2...Workpiece, 3...Spindle, 4...
・Spindle motor, 5...Turret, 6...Table, 7, 8
...Feed motor, 12, 12. A...Vacuum chuck,
19.20...Chuck◇ 16゛〒1Figure JP-A-3-281138 (6) 〒zFigure〒5Figure+2A-Shinmenchi↑77 13.20-1-S ↑7 Child 5 Figure〒4

Claims (1)

[Scope of Claims] 1. A main spindle with an elastic chuck attached to hold a workpiece, a motor that rotationally drives this main spindle, a tool holder that holds a cutting tool, and a main shaft that holds this tool holder with respect to the axis of the main spindle. In a mirror cutting device equipped with a means for moving the workpiece in both the direction and the perpendicular direction, the chuck is provided with an elastic recovery amount so that the workpiece can be cut without creating a step in response to fluctuations in cutting force during cutting. A mirror cutting device characterized by forming a variable part. 2. The portion where the amount of elastic recovery of the chuck varies is characterized in that the chuck that holds the workpiece is formed so that the thickness thereof becomes thinner at least in the portion where the cutting force suddenly decreases. The mirror cutting device described. 3. A variation in the elastic recovery amount of the chuck is characterized in that the chuck holding the workpiece has a Young's modulus larger at least in a range where the cutting force suddenly decreases than in other ranges. 1. The mirror cutting device according to 1. 4. A mirror-cut product, characterized in that the surface of a workpiece is mirror-cut using the mirror-cutting device according to any one of claims 1 to 3, and the machined surface has no step. 5. A mirror-cut product according to claim 4, wherein the mirror-cut product is a disk substrate.