JP2005279902A - Polishing device and polishing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polishing device and a polishing method capable of generating a fine working surface with high form accuracy without a wave, in polishing a workpiece with a spherical surface, an aspheric surface, and a free-form surface. <P>SOLUTION: This polishing device is provided with an air cylinder reciprocating the polishing tool 1 relative to the workpiece 16, a rotating means varying the tilt angle of the polishing tool and the air cylinder, and a control means controlling at least one or the other of pressure of the air cylinder in the thrust direction and pressure compensating its own weight of a movable section in the air cylinder. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a polishing apparatus and a polishing method for polishing a workpiece having a spherical surface, an aspherical surface, and a free-form surface with high shape accuracy.

  For workpieces having spherical, aspherical, and free-form surfaces such as optical elements and molding dies for molding optical elements, the following polishing process using pressure transfer has been conventionally performed. .

  That is, Japanese Patent Laid-Open No. 2002-361546 discloses a polishing apparatus including a load mechanism unit that presses a polishing tool against a workpiece having a free-form surface shape. As the load mechanism part, an air cylinder having two pressure receiving parts with different pressure receiving areas is used. One pressure receiving part compensates the weight of the movable part including the polishing tool, and the other pressure receiving part is subjected to arbitrary processing. It is configured to generate pressure.

  In the polishing apparatus described in Japanese Patent Laid-Open No. 10-15801, the relationship between the direction of the thrust and the normal direction at the processing point is always constant with respect to the processing point of the workpiece having a spherical or aspherical shape. The structure is such that the workpiece is processed while controlling the posture of the workpiece by three axes of up / down, left / right, and rotational directions. In this case, a force in the direction opposite to the direction of thrust is applied by air pressure, hydraulic pressure, and magnetic force, and the differential pressure between this pressure and the weight of the tool portion is used as the machining pressure.

The polishing apparatus described in Utility Model Registration No. 2607184 has a structure that tilts the tool axis with respect to a workpiece such as a lens having a spherical shape and always applies a machining pressure toward the center of curvature of the workpiece. The force in the direction of the tool axis is urged by an air cylinder, and a force is applied by a spring in the direction opposite to the direction of this force to cancel the weight of the tool axis.
JP 2002-361546 A Japanese Patent Laid-Open No. 10-15801 Utility Model Registration No. 2607184

  In the polishing apparatus disclosed in Japanese Patent Laid-Open No. 2002-361546, the tool portion and the workpiece can be relatively moved only in the tool axis (load axis) direction and only in a plane perpendicular to the tool axis. In this case, except when the workpiece is a plane, the angle formed by the tool axis (load axis) and the normal line at the machining point of the workpiece changes depending on the position of the workpiece. Become.

  On the other hand, in the polishing process, Preston's rule of thumb is known. This is a relationship expressed by the equation (1) where δ is the polishing amount, K is the proportionality constant, P is the processing pressure, v is the polishing rate, and t is the polishing time.

δ = K · P · v · t (1) Equation (1) The machining pressure P in the equation (1) is the pressure that the workpiece receives from the normal direction at the machining point.

  On the other hand, in the polishing apparatus described in Japanese Patent Application Laid-Open No. 2002-361546, the angle formed between the tool axis (load axis) and the normal line at the processing point of the workpiece varies depending on the position of the workpiece. Therefore, the processing pressure P also varies depending on the processing position of the workpiece. If v and t in the equation (1) are constant, the polishing amount δ changes in proportion to the change in the processing pressure P. For this reason, the polishing apparatus described in Japanese Patent Application Laid-Open No. 2002-361546 has a problem that the amount of polishing varies depending on the processing position, making it difficult to perform stable processing.

  The polishing apparatus described in Japanese Patent Application Laid-Open No. 10-15801 has a problem that it is difficult to control the posture of the workpiece when the weight or size of the workpiece is large.

  In the polishing apparatus described in Utility Model Registration No. 2607184, the tool portion tilts, but the tool portion tilts because the pressure in the tool axis direction and the pressure in the direction opposite to the direction of this pressure are always constant. Then, when the component force in the tool axis direction in the weight of the tool portion changes, the machining pressure fluctuates. Therefore, as in JP 2002-361546 A, there is a problem that the polishing amount varies depending on the processing position.

  The present invention has been made in consideration of such problems. When machining a workpiece having a spherical surface, an aspherical surface, or a free-form surface, the present invention has high shape accuracy and good undulation. An object of the present invention is to provide a polishing apparatus and a polishing method capable of creating a surface.

  The invention according to claim 1 is a polishing apparatus that polishes a workpiece by a polishing tool that rotates, and an air cylinder that moves the polishing tool forward and backward relative to the workpiece, and an inclination angle of the polishing tool and the air cylinder And a control means for controlling at least one of the pressure in the thrust direction of the air cylinder and the pressure for compensating the dead weight of the movable part in the air cylinder in accordance with the inclination angle. Features.

  In the first aspect of the present invention, when the rotation driving means changes the inclination angle of the polishing tool and the air cylinder, the control means compensates the pressure in the thrust direction of the air cylinder or the weight of the movable part according to the inclination angle. Therefore, the processing pressure in the normal direction at the processing point can always be kept constant. For this reason, it is possible to create a good machined surface without waviness with high shape accuracy.

  The invention according to claim 2 is the polishing apparatus according to claim 1, wherein the control hand throw includes a proportional electromagnetic pressure control valve for controlling the pressure in the thrust direction of the air cylinder, and a movable part in the air cylinder. And a pressure control valve for controlling the pressure to compensate for the self weight.

  In the second aspect of the invention, since the control means includes the proportional electromagnetic pressure control valve and the pressure control valve, the pressure in the thrust direction of the air cylinder and the pressure for compensating the weight of the movable part in the air cylinder are controlled with high accuracy. be able to.

  A third aspect of the present invention is the polishing apparatus according to the first or second aspect, wherein the air cylinder includes a cylinder rod that advances and retreats together with the polishing tool, and surrounds the cylinder rod to support the cylinder rod with aerostatic pressure. And a cylinder tube.

  In the invention according to claim 3, since the cylinder tube supports the cylinder rod by the static air pressure, the polishing tool connected to the cylinder rod can be controlled with high accuracy.

  According to a fourth aspect of the present invention, in the polishing method for polishing with a polishing tool that rotates the workpiece, the polishing tool is brought into contact with the workpiece with an air cylinder, and the polishing tool and the workpiece are separated. The pressure of at least one of the step of varying the inclination angle of the polishing tool and the air cylinder according to the contact location, and the pressure in the thrust direction of the air cylinder and the pressure compensating the weight of the movable part in the air cylinder according to the inclination angle And controlling the workpiece to polish the workpiece.

  In the invention according to claim 4, in order to polish the workpiece by controlling the pressure in the thrust direction of the air cylinder or the pressure of the movable part in the air cylinder according to the inclination angle of the polishing tool and the air cylinder, The processing pressure in the normal direction at the processing point can always be kept constant, and a good processing surface with no waviness can be created with high shape accuracy.

  According to the polishing apparatus of the present invention, when processing a workpiece having a spherical surface, an aspherical surface, or a free-form surface shape, the control means controls the direction of thrust of the air cylinder according to the inclination angle of the polishing tool and the air cylinder. Since the pressure or the pressure that compensates the weight of the movable part is controlled, the machining pressure in the normal direction at the machining point can always be kept constant. For this reason, it is possible to create a good machined surface with high shape accuracy and no waviness, and to improve and stabilize the quality of the workpiece.

  According to the polishing method of the present invention, since the processing pressure in the normal direction at the processing point can be kept constant at the time of polishing the workpiece, a good processed surface with high shape accuracy and no waviness. Can be created, and the quality of the workpiece can be improved and stabilized.

  Hereinafter, the present invention will be specifically described with reference to embodiments.

(Embodiment 1)
In this embodiment, a case where a workpiece having a spherical or aspherical shape is polished will be described. FIG. 1 is a front view of the main part of the polishing apparatus, FIG. 2 is a side view showing the periphery of the tool portion from the arrow A in FIG. 1, and FIG. 3 is a sectional view of the air bearing cylinder.

  The tool unit 5 includes a spherical polisher 1 for polishing a workpiece 16 as a workpiece. The polisher 1 is rotatable by being attached to the spindle 2. The spindle 2 is attached to a plate 4a by a bracket 3, and the plate 4a is attached to a rod 7 of an air bearing cylinder 6 via plates 4b and 4b.

  The air bearing cylinder 6 is provided with three air ports 8, 9 and 10. The bearing port 8 is supplied with air decompressed to an appropriate pressure by the precision regulator 11. The thrust port 9 is supplied with air having a pressure appropriately controlled by a proportional electromagnetic pressure control valve 12 as a first control means. Air that has been decompressed to an appropriate pressure by the precision regulator 13 as the second control means is supplied to the cancel port 10. In this case, a proportional electromagnetic pressure control valve may be used instead of the precision regulator 13.

  As shown in FIG. 3, the air bearing cylinder 6 is a cylinder in which a cylinder rod 7 and a cylinder tube 33 are supported by static air pressure, and the straightness accuracy when the cylinder rod 7 advances and retreats without using a guide or the like. It is high and does not require a guide, so that the sliding resistance when the cylinder rod 7 moves back and forth is extremely small.

  As shown in FIG. 3, in the air bearing cylinder 6, the cylinder rod 7 has a substantially cylindrical shape, and a ring-shaped protrusion 7a is provided at the center. The protrusion 7 a has a thrust side pressure receiving portion 39 on the top surface and a cancel side pressure receiving portion 40 on the bottom surface. In addition, a substantially cylindrical cylinder tube 33 is disposed around the cylinder rod 7, and the cylinder tube 33 is provided with three air ports including a bearing port 8, a thrust port 9, and a cancel port 10. It has been.

  The bearing port 8 passes through the inside of the cylinder tube 33 and communicates with a first porous member 36 a surrounding the upper side surface of the cylinder rod 7 and a second porous member 36 b surrounding the lower side surface of the cylinder rod 7. . Therefore, the air from the precision regulator 11 is supplied from the bearing port 8 to the upper side surface and the lower side surface of the cylinder rod 7 through the porous members 36a and 36b, and supports the cylinder rod 7 with static air pressure.

  The thrust port 9 communicates with the space above the thrust side pressure receiving portion 39 through the inside of the cylinder tube 33. Therefore, the air from the proportional electromagnetic pressure control valve 12 acts to push down the thrust side pressure receiving portion 39 in the tool axis B direction via the thrust port 9.

  The cancel port 10 communicates with the lower space of the cancel side pressure receiving portion 40 through the inside of the cylinder tube 33. Accordingly, the air from the precision regulator 13 acts to push up the cancel side pressure receiving portion 40 in the tool axis B direction via the cancel port 10.

  By the operation of the air bearing cylinder 6 as described above, the tool 5 including the polisher 1 can advance and retreat in the tool axis B direction. The machining pressure at this time is generated as a differential pressure between the weight and thrust of the movable part including the cylinder rod 7 in the air bearing cylinder 6 and the pressure on the side that compensates the weight of the movable part.

Further, the air bearing cylinder 6 is attached to a disc-shaped rotary table 14 and is rotated around a central axis θ ₁ (see FIG. 1) of the rotary table 14 by a θ-axis servo motor 15 as a rotation driving means. Can be tilted.

  The work 16 is connected to a motor 18 fixed to a work base 19 via a yatoy 17 and can rotate about a Z axis (vertical axis). The work table 19 is connected to a nut (not shown) that is screwed to an X-axis ball screw 21 that is rotated by an X-axis servomotor 20, thereby moving on the X-axis guide 22 in the X-axis direction (horizontal direction). It has become.

  A nut (not shown) screwed into the Z-axis ball screw 24 is attached to the Z-axis guide 25, and the work base 19 and the X-axis constituent members are moved on the Z-axis guide 25 by the rotation of the Z-axis servo motor 23. It is movable in the axial direction (vertical direction).

  With the above configuration, the workpiece 16 can freely move in the XZ plane.

  The operation of the polishing apparatus of this embodiment will be described.

  First, the inclination angle of the tool axis with respect to the normal direction at the machining point of the workpiece 16 is set. Normally, when the polisher 1 is spherical, it is appropriate to set the inclination angle to about 30 to 60 ° so that the side surface of the polisher abuts the workpiece 16 in order to contribute to the processing speed of the polisher 1. In this embodiment, this inclination angle is set to 45 °.

  When the polisher 1 does not hold the abrasive in advance, the abrasive is supplied onto the work 16 before processing, and if necessary, the abrasive is supplied at an appropriate time during processing. The operation during processing is as follows.

  While rotating the workpiece 16 and the polisher 1 and controlling the X axis, the Z axis, and the θ axis, the polisher 1 is placed on the outermost peripheral portion in the positive direction of the X axis on the bus bar on the surface of the workpiece 16 within a preset processing range. Abut. At this time, as a matter of course, the angle formed between the normal line at the contact point between the workpiece 16 and the polisher 1 and the tool axis is a set value (45 °).

  After that, the X-axis, Z-axis, and θ-axis are appropriately controlled so that the angle between the normal line at the contact point between the workpiece 16 and the polisher 1 and the tool axis is kept constant, while the polisher 1 is previously applied to the bus on the surface of the workpiece 16. Move relatively according to the set moving speed. After passing through the center of the workpiece 16, the polisher 1 finishes one machining when reaching the outermost peripheral portion in the negative direction of the X axis on the generatrix on the surface of the workpiece 16 within a preset machining range. FIG. 4 shows a trajectory 26 in which the polisher 1 relatively moves on the workpiece 16 at this time.

  The above operation is performed by executing an NC program created in advance based on the design drawing of the workpiece.

  The case where the polisher 1 in the above operation is at X = 0 (state of FIG. 1) will be described.

  When the thrust is P, the pressure for compensating the dead weight of the movable part (pressure in the direction opposite to the direction of the thrust) is R, and the dead weight of the movable part is W, the load F in the tool axis direction is expressed by equation (2).

F = P + W · cos 45 ° −R (2) Equation (2) W · cos 45 ° in the equation (2) represents the component force in the tool axis direction due to the weight of the movable portion of the air bearing cylinder 6.

  Next, as shown in FIG. 5, a case where the polisher 1 is at a position where X = a will be described.

  At this time, if the angle between the normal line at the contact point between the polisher 1 and the workpiece 16 and the vertical direction is α, the inclination angle of the tool axis is 45 ° + α with respect to the vertical direction. When the thrust is P ′, the pressure for compensating the weight of the movable part (pressure opposite to the direction of the thrust) is R, and the weight of the movable part is W, the load F ′ in the tool axis direction is expressed by the following equation (3): Become.

  F ′ = P ′ + W · cos (45 ° + α) −R (3)

From the relationship between these equations (2) and (3),
P ′ = P + W · (cos 45 ° −cos (45 ° + α)) (4) Therefore, F = F ′, and the processing pressure at the position of X = 0 and the position of X = a can be made constant.

Specifically, at the position of X = 0, when the voltage applied to the proportional electromagnetic type pressure control valve 12 was set to V _0, the voltage V _a to provide at the position of X = a proportional electromagnetic pressure control valve 12, the number The equation (5) shown in FIG.

  The angle α in the equation (5) is obtained by taking the pulse signal of the θ-axis servomotor 15 that drives the rotary table 14 into a calculation computer (not shown) and converting the angle, and then substituting it into the equation (5) to obtain the desired angle α. The voltage value can be obtained by applying analog voltage to the proportional electromagnetic pressure control valve 12 after analog conversion by a DA converter (not shown).

(Embodiment 2)
In this embodiment, the case of polishing a workpiece having a free-form surface will be described. In this embodiment, it is assumed that the normal line on the workpiece 16 at the machining point coincides with the axial direction of the tool axis.

  Although the configuration on the workpiece axis side is not shown, a Y-axis drive unit that can move the workpiece portion in a direction perpendicular to the X-Z plane is provided for the first embodiment, and the workpiece portion is in the XYZ space. Is configured to be orthogonally moved.

  FIG. 6 is a front view of the tool portion 5 portion in this embodiment, and FIG. 6 is a side view of the tool portion 5 portion.

The air bearing cylinder 6 is attached to a θ ₁ axis rotary table 27 that is driven to rotate about the θ ₁ axis by a θ ₁ axis servo motor 28. The θ _1- axis servo motor 28 is rotatable by a bracket 29 in a plane perpendicular to the θ ₁ rotation plane. That is, the θ _1- axis servomotor 28 is attached to a θ ₂ axis rotary table 30 that is rotatable about a θ ₂ axis that is perpendicular to and horizontal with respect to the θ ₁ axis. The θ _2- axis rotary table 30 is rotationally driven by being attached to a θ _2- axis servo motor 31.

In machining the workpiece 16 having a free-form surface shape, the X, Y and Z axes are generally controlled so that the polisher 1 scans the workpiece 16 so as to draw a locus 32 as shown in FIG. is there. At this time, the θ ₁ axis servo motor 28 and the θ ₂ axis servo motor 31 are controlled so that the normal line on the workpiece 16 at the machining point and the tool axis coincide.

If the angle between the normal direction of the workpiece 16 and the vertical direction is β at a certain machining point, and the θ ₁ axis is tilted by θ ₁ ° and θ ₂ is tilted by the axis θ ₂ °, the angle β is several Therefore, the workpiece 16 having a free-form surface can be machined by controlling the thrust by the same method as in the first embodiment.

  In the above-described first and second embodiments, the case where the thrust is controlled is shown, but the pressure on the side compensating for its own weight may be controlled, or both may be controlled.

It is a front view of the grinding | polishing processing apparatus in Embodiment 1 of this invention. FIG. 2 is a side view from the direction of arrow A in FIG. 1 showing the tool part of the first embodiment. It is sectional drawing of the air bearing cylinder used for a grinding | polishing apparatus. FIG. 6 is a plan view showing a movement locus of the polisher relative to the workpiece in the first embodiment. FIG. 2 is a front view of the polishing apparatus during processing according to the first embodiment. 10 is a front view of a tool unit according to Embodiment 2. FIG. 6 is a side view of a tool unit according to Embodiment 2. FIG. FIG. 10 is a plan view showing a movement locus of a polisher with respect to a workpiece in the second embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Polisher 2 Spindle 5 Tool part 6 Air bearing cylinder 7 Cylinder rod 8 Bearing port 9 Thrust port 10 Cancel port 11 Precision regulator 12 Proportional electromagnetic pressure control valve 13 Precision regulator 14 Rotary table 15 θ-axis servo motor 16 Work piece 19 Work base 20 X-axis servo motor 23 Z-axis servo motor

Claims (4)

In a polishing apparatus for polishing a workpiece with a rotating polishing tool,
An air cylinder for advancing and retracting the polishing tool with respect to the workpiece;
Rotation drive means for varying the inclination angle of the polishing tool and the air cylinder;
Control means for controlling at least one of the pressure in the thrust direction of the air cylinder and the pressure for compensating the weight of the movable part in the air cylinder according to the inclination angle;
A polishing apparatus characterized by comprising:   The control hand throw comprises a proportional electromagnetic pressure control valve that controls the pressure in the thrust direction of the air cylinder, and a pressure control valve that controls the pressure to compensate for the weight of the movable part in the air cylinder. The polishing apparatus according to claim 1.   3. The polishing apparatus according to claim 1, wherein the air cylinder includes a cylinder rod that advances and retreats together with the polishing tool, and a cylinder tube that surrounds the cylinder rod and supports the cylinder rod with aerostatic pressure. 4. In a polishing method of polishing a workpiece by a rotating polishing tool,
Abutting the polishing tool against a workpiece by an air cylinder, and varying an inclination angle of the polishing tool and the air cylinder according to a contact position between the polishing tool and the workpiece;
Polishing the workpiece by controlling at least one of the pressure in the thrust direction of the air cylinder and the pressure compensating for the dead weight of the movable part in the air cylinder according to the inclination angle;
A polishing method characterized by comprising:

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