JP2000237931A - Curved surface working method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily and accurately work a free curved surface by previously working a dummy work having a circular cross section of the same curvature radius as the minimum curvature radius among the circular arc approximation, and deciding the tool feeding speed, the number of revolution of the tool and response condition of the load control. SOLUTION: Traverse direction is decided (step S01), and the locus of a tool contact point is obtained (step S102). Circular arc is approximated in each block, and the minimum curvature radius is obtained (step S103), and a dummy work having a cylinder surface, of which curvature radius is set at the minimum curvature radius, and made of the same raw material as a work is used to decide the tool feeding speed and the number of revolution of the tool as working condition for obtaining the satisfied surface roughness as a target in polishing of work (step S104). Tool feeding speed in each operation block is decided on the basis of a ratio of the approximate curvature radius to the minimum curvature radius in each operation block (step S108). Finally, the number N of revolution of the tool is decided (step S109).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a curved surface processing method, and more particularly to a curved surface processing method for finishing a curved surface into a mirror surface usable as an optical component.

[0002]

2. Description of the Related Art Conventionally, a toric lens having a different curvature radius in a longitudinal direction and a lateral direction, a deformed toric lens having a cross section of a specific circular arc, or a mold polishing method therefor is disclosed in Japanese Patent Application Laid-Open No. Sho 62-246467. As described, in the polishing of the mold, an auxiliary die having the same height as the periphery of the die is fitted around the die, and the start, end, or switching of the processing direction of the polishing operation is performed by the auxiliary die. There is a polishing method performed above. That is, in the related art, a polishing method in which a small-diameter tool is pressed with a constant force and scanned therewith is widely used.

In such a conventional polishing method, the accuracy of the shape can be improved by controlling the posture of the tool or the rotation axis of the tool so as to always make a constant angle with respect to the normal to the surface to be processed. .

[0004]

However, in such a conventional curved surface machining technique, in order to improve the shape accuracy, the position of the tool or the rotation axis of the tool is set with respect to the normal line of the surface to be processed. It is controlled so that it always makes a certain angle.

By performing such an attitude control, the load in the normal direction of the polishing tool at the processing point can be made constant regardless of the inclination angle of the processing surface of the workpiece. In order to perform the control, in addition to the tool load axis, an X as disclosed in Japanese Patent Application Laid-Open No. 9-323252 is used.
4-axis simultaneous control such as Y orthogonal 2 axes, AB rotation 2 axes,
Alternatively, it is necessary to perform simultaneous three-axis control such as two axes of XY orthogonal and one axis of A rotation as disclosed in JP-A-6-126607.

However, when the simultaneous control of four axes or the simultaneous control of three axes is performed, the apparatus becomes complicated and large in size. In addition, these apparatuses are used to scan a tool to perform polishing, cutting, or grinding. Requires an NC program. However, it is necessary to create a complicated program that performs a tilt operation and a parallel movement operation at the same time. To create such a complicated program, a dedicated CAM (Computer Aid
Without ed Manufacturing), there was a problem that enormous labor and work time were required, workability was poor, and cost was high.

In view of the above, according to the first aspect of the present invention, while rotating a tool having a smaller diameter than the workpiece at a predetermined rotational speed around the axis, the load of the tool is made substantially constant and a predetermined locus is formed on a predetermined locus. When machining a curved surface by scanning at a tool feed speed of a tool, the contact locus of the tool with the workpiece is approximated by an arc, and the dummy machining having an arc cross section having the same radius of curvature as the minimum radius of curvature in the arc approximation. Preliminarily processing the object, determining the tool feed speed, tool rotation speed and load control response condition, and processing the workpiece based on the determined tool feed speed, tool rotation speed and load control response condition. Therefore, without using a complicated device such as four-axis control and a machining program, a conventional simple curved surface machining device composed of an NC table of two axes orthogonal to the tool load axis can be used at low cost.
Another object of the present invention is to provide a curved surface processing method capable of easily and accurately processing a free curved surface.

According to a second aspect of the present invention, while rotating a tool smaller in diameter than the workpiece at a predetermined tool rotation speed around the axis, the load of the tool is made substantially constant and a predetermined tool is moved on a predetermined trajectory. When scanning a curved surface by scanning at the feed rate, the contact trajectory of the tool with the workpiece to the workpiece surface is approximated by an arc,
From the arc approximation, the minimum radius of curvature is determined, and the minimum curvature is determined from a database of the tool feed speed, the tool rotation speed, and the response condition of load control determined by preliminarily preliminarily processing a dummy workpiece having an arc cross section of various curvature radii. By reading the tool feed speed, tool rotation speed and load control response condition based on the radius, and processing the workpiece based on the read tool feed speed, tool rotation speed and load control response condition, the 4-axis Without using complicated equipment such as control and machining programs, using a conventional simple curved surface machining device consisting of an NC table with two axes perpendicular to the tool load axis, tool feed speed, tool rotation speed and load control It is an object of the present invention to provide a curved surface processing method capable of quickly determining a response condition, and more accurately and easily processing a free-form surface at low cost.

According to a third aspect of the present invention, the rise time and the overshoot amount with respect to the step command value of the load control of the tool are used as the response conditions of the load control. Processing without changing, while suppressing the deterioration of the shape,
It is an object of the present invention to provide a curved surface processing method capable of easily and accurately processing a free-form surface at low cost.

According to a fourth aspect of the present invention, a tool feed speed of a contact locus having a radius of curvature other than the minimum radius of curvature is determined based on a ratio between the radius of curvature of the contact locus and the minimum radius of curvature. The tool feed speed is increased in proportion to the radius of curvature to increase the machining efficiency, and to increase the delay in following unnecessary high-period surface undulations.
It is an object of the present invention to provide a curved surface processing method capable of improving a surface undulation removal performance and processing a free-form surface with higher accuracy.

According to a fifth aspect of the present invention, the scanning of the tool includes a linear motion in the X-axis direction or the Y-axis direction and a folding operation of a predetermined width in the Y-axis direction or the X-axis direction for performing the linear motion. By adopting a scanning trajectory of only one-axis linear motion excluding the turning operation as a contact trajectory for performing circular arc approximation, it is possible to reduce a mechanical motion error as compared with simultaneous two-axis feeding. In addition to enabling general-purpose precision processing machines to perform higher-precision processing, NC programs for scanning polishing tools can be created more easily and in a shorter time, making free-form surfaces easier and cheaper. It is an object of the present invention to provide a curved surface processing method capable of processing accurately.

According to a sixth aspect of the present invention, the scanning of the tool includes a linear motion in the X-axis direction or the Y-axis direction and a folding operation of a predetermined width in the Y-axis direction or the X-axis direction for performing the linear motion. Performing the circular arc approximation of the contact trajectory of the tool, projecting the tool trajectory in a plane formed by a linear motion axis and an axis for applying a load to the work surface of the workpiece orthogonal to the linear motion axis,
By approximating the projected tool trajectory by the least square method, even when the contact trajectory bends when viewed from the tool load axis direction, the radius of curvature corresponding to the load control response can be easily and accurately determined. It is an object of the present invention to provide a curved surface processing method capable of processing a free-form surface more precisely.

According to a seventh aspect of the present invention, in the case where the workpiece surface of the workpiece includes both a convex curved surface and a concave curved surface, the tool trajectory is divided by the inflection points of the convex curved surface and the concave curved surface, and the tool trajectory of the convex curved surface is divided. Surface machining method that can perform high-shape precision machining even on a complex free-form surface where the tool path forms a convex arc and a concave arc by performing arc approximation for each of the tool trajectory and the concave curved surface. It is intended to provide.

According to an eighth aspect of the present invention, there is provided a curved surface processing method comprising:
By applying to the polishing of the work surface of the work,
Without using a complicated device such as 4-axis control and a machining program, using a conventional simple curved surface polishing device composed of an NC table having two axes orthogonal to the polishing load axis, the tool feed speed, the number of rotations of the tool and the load are used. It is an object of the present invention to provide a curved surface processing method capable of quickly determining a control response condition and inexpensively and easily polishing a free-form surface more accurately.

According to a ninth aspect of the present invention, there is provided a curved surface processing method comprising:
By applying to cutting or grinding of the work surface of the work piece, it can be easily applied to the processing machine configuration that is replaced with a cutting axis with a fixed size of the tool load axis, and the free-form surface can be created with high precision. It is another object of the present invention to provide a curved surface processing method capable of performing cutting or grinding with high accuracy while suppressing surface waviness.

[0016]

According to a first aspect of the present invention, there is provided a curved surface machining method, wherein a tool having a smaller diameter than a workpiece is rotated around a predetermined axis at a predetermined number of tool rotations to reduce a load of the tool. In a curved surface machining method of machining a curved surface by scanning a predetermined trajectory at a predetermined tool feed speed while maintaining a substantially constant, a contact trajectory of the tool with respect to a workpiece surface of the workpiece is circularly approximated, and the circular arc approximation is performed. Of these, a dummy workpiece having an arc cross section having the same radius of curvature as the minimum radius of curvature is preliminarily processed, and a tool feed speed, a tool rotation speed, and response conditions of load control are determined, and the determined tool feed speed, tool rotation speed and The above object is achieved by processing the workpiece based on a load control response condition.

According to the above construction, while rotating the tool smaller in diameter than the workpiece at a predetermined tool rotation speed around the axis, the load of the tool is made substantially constant, and the predetermined tool feed speed is set on a predetermined trajectory. When machining a curved surface by scanning with a tool, the contact trajectory of the tool with the workpiece is approximated by a circular arc, and a dummy workpiece having an arc cross section having the same radius of curvature as the minimum radius of curvature of the circular arc approximation is preliminarily processed. And the tool feed rate,
The tool rotation speed and load control response conditions are determined, and the workpiece is processed based on the determined tool feed speed, tool rotation speed, and load control response conditions. Without using a program, a free-form surface can be accurately machined easily and inexpensively by using a conventional simple surface machining apparatus composed of an NC table having two axes perpendicular to the tool load axis.

According to a second aspect of the present invention, there is provided a curved surface machining method in which a tool having a smaller diameter than a workpiece is rotated around a predetermined axis at a predetermined number of tool revolutions while the load of the tool is kept substantially constant. In a curved surface machining method for machining a curved surface by scanning a trajectory at a predetermined tool feed speed, a contact trajectory of the tool with respect to a workpiece surface of the workpiece is circularly approximated, and a minimum radius of curvature of the circular arc approximation is obtained. From a database of tool feed speeds, tool rotation speeds and load control response conditions determined in advance by pre-machining a dummy workpiece having an arc cross section of various curvature radii, a tool feed speed, a tool based on the minimum radius of curvature, The above object has been achieved by reading the response conditions of the rotation speed and the load control and processing the workpiece based on the read tool feed speed, the tool rotation speed and the response conditions of the load control. There.

According to the above construction, while rotating the tool smaller in diameter than the workpiece at the predetermined tool rotation speed around the axis, the load of the tool is made substantially constant, and the predetermined tool feed speed is set on the predetermined trajectory. When machining a curved surface by scanning with a tool, the contact locus of the workpiece with the workpiece is approximated by an arc, the minimum radius of curvature is determined from the arc approximation, and a dummy workpiece having an arc cross section having various radii of curvature is obtained. The tool feed speed, the tool rotation speed and the response condition of the load control are read out based on the minimum radius of curvature from the database of the tool feed speed, the tool rotation speed and the response condition of the load control determined by preliminary machining in advance. Since the workpiece is machined based on the tool feed speed, tool rotation speed and load control response conditions, it does not require complicated equipment such as 4-axis control and machining programs,
Using a conventional simple curved surface processing device composed of a tool load axis and an NC table of two orthogonal axes, the tool feed speed, tool rotation speed and response conditions of load control are quickly determined, and inexpensively, and The free-form surface can be more accurately processed more easily.

In each of the above cases, for example, as set forth in claim 3, the curved surface machining method includes, as response conditions of the load control, a rise time and an overshoot amount with respect to a step command value of the load control of the tool. It may be used.

According to the above configuration, since the rise time and the overshoot amount with respect to the step command value of the load control of the tool are used as the response conditions of the load control, the tool feed speed is changed regardless of the skill level of the operator. Without
In addition, the processing can be performed while suppressing the deterioration of the shape, and the free-form surface can be accurately and easily processed at low cost.

For example, in the curved surface machining method, the tool feed speed of a contact trajectory having a radius of curvature other than the minimum radius of curvature may be determined by changing the tool feed speed of the contact trajectory to the radius of curvature of the contact trajectory. It may be determined based on the ratio to the radius of curvature.

According to the above configuration, the tool feed speed of the contact locus having a radius of curvature other than the minimum radius of curvature is determined based on the ratio between the radius of curvature of the contact locus and the minimum radius of curvature. Increase the tool feed speed in proportion to the size,
Higher processing efficiency can be achieved, and
It is possible to enhance the follow-up delay with respect to unnecessary high-period surface undulations, improve the surface undulation removal performance, and process the free-form surface with higher accuracy.

Further, for example, as set forth in claim 5, in the curved surface machining method, as the scanning of the tool, a linear motion in the X-axis direction or the Y-axis direction and a Y-axis direction for performing the linear motion. A trajectory of a predetermined width in the X-axis direction is performed, and as a contact trajectory for performing the circular arc approximation, a trajectory of only the linear motion in one axis direction excluding the wrapping operation may be adopted. .

According to the above arrangement, X is used as the tool scan.
A linear motion in the axial direction or the Y-axis direction and a folding operation of a predetermined width in the Y-axis direction or the X-axis direction for performing the linear motion are performed. Since the scanning trajectory of only the linear motion in the axial direction is adopted, it is possible to reduce the possibility of mechanical movement error compared to simultaneous two-axis feed, and to perform higher-precision processing with a general-purpose processing machine. Along with
An NC program for scanning the polishing tool can be created more easily and in a shorter time, and the free-form surface can be accurately and easily processed at a lower cost.

For example, in the curved surface machining method, as the scanning of the tool, a linear motion in an X-axis direction or a Y-axis direction and a Y-axis direction or a Y-axis direction for performing the linear motion. A folding operation of a predetermined width in the X-axis direction is performed, and a circular arc approximation of the contact trajectory of the tool is performed. The linear motion axis and the load on the workpiece surface of the workpiece that is orthogonal to the linear motion axis The tool trajectory may be projected in a plane formed by the application axis, and the projected tool trajectory may be approximated by the least square method.

According to the above arrangement, X is used as the tool scan.
A linear motion in the axial direction or the Y-axis direction and a folding operation of a predetermined width in the Y-axis direction or the X-axis direction for performing the linear motion are performed. Since the tool trajectory is projected in a plane perpendicular to the operating axis and formed by a load applying axis to the work surface of the workpiece of the tool, and the projected tool trajectory is obtained by approximation by the least square method, contact Even when the trajectory bends when viewed from the tool load axis direction, the radius of curvature corresponding to the response of the load control can be easily and accurately obtained, and the free-form surface can be machined more accurately.

Further, for example, as described in claim 7, in the curved surface machining method, when the surface to be machined of the workpiece has a mixture of a convex curved surface and a concave curved surface, the tool trajectory is defined by the convex curved surface and the concave curved surface. The curved surface may be divided at an inflection point, and the arc approximation may be performed on each of the tool trajectory of the convex surface and the tool trajectory of the concave surface.

According to the above configuration, when the workpiece surface of the workpiece has both a convex curved surface and a concave curved surface, the tool trajectory is divided by the inflection point of the convex curved surface and the concave curved surface, and the tool trajectory of the convex curved surface and the concave curved surface are divided. Since arc approximation is performed for each of the tool trajectories on a curved surface, machining with high shape accuracy can be performed even on a complicated free-form surface where the tool trajectory forms a convex arc and a concave arc.

Further, for example, as set forth in claim 8, the curved surface processing method may include a step of polishing a surface to be processed of the workpiece.

According to the above configuration, since the curved surface processing method is applied to the polishing of the processing surface of the workpiece, the polishing load axis can be reduced without using a complicated apparatus such as four-axis control and a processing program. The tool feed speed, tool rotation speed, and response conditions for load control are quickly determined using a conventional simple curved surface polishing machine composed of a two-axis NC table orthogonal to the axis. The free-form surface can be accurately polished.

Further, for example, as set forth in claim 9, the curved surface processing method may include cutting or grinding the surface to be processed of the workpiece.

According to the above configuration, since the curved surface processing method is applied to the cutting or grinding of the surface to be processed of the workpiece, the processing machine can be easily replaced with a cutting shaft having a fixed dimension of the tool load axis. In this case, the free-form surface can be formed with high accuracy, and the cutting or grinding can be performed with high accuracy while suppressing the surface undulation.

[0034]

Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings. It should be noted that the embodiments described below are preferred embodiments of the present invention, and therefore, various technically preferable limitations are added. However, the scope of the present invention is not limited to the following description. The embodiments are not limited to these embodiments unless otherwise specified.

FIGS. 1 to 10 are views showing one embodiment of a curved surface processing method of the present invention. FIG. 1 is a front view of a polishing apparatus 1 to which one embodiment of the curved surface processing method of the present invention is applied. FIG.

In FIG. 1, a polishing apparatus 1 has an XY orthogonal 2
Based on the NC table of the axis,
X that can be moved in the X-axis direction
The axis table 3 is placed. On the X-axis table 3, a Y-axis table 4 that can move in the Y-axis direction, which is the left-right direction indicated by a double-headed arrow in FIG. 1, is mounted. Fixed. The workpiece 100 is a lens, a mirror, and a mold for these.

On the base 2, a linear motion guide shaft 5 has an X axis and a Y axis.
The linear motion guide 6 is movably mounted on the linear motion guide shaft 5 so as to extend in the Z-axis direction (vertical direction in FIG. 1) which is a direction perpendicular to the axis. A spindle 7 is fixed to the linear guide 6, and a tool 8 is fixed to the tip of the spindle 7 so as to be replaceable.

As the tool 8, for example, as shown in FIG. 2, a polishing tool is used, and the spindle 7 drives the tool 8 to rotate around its rotation axis.

The linear guide 6 is moved up and down by a pressing mechanism 9 mounted on the linear guide shaft 5, and the pressing mechanism 9 applies a predetermined polishing load to the tool 8 mounted on the spindle 7. . A load cell 10 is attached to a position of the linear motion guide 6 facing the pressure mechanism 9, and a weight 11 is attached to the load cell 10. Then, the polishing load is detected by the load cell 10, and the polishing apparatus 1 presses the pressing mechanism 9 based on the detection result.
Are sequentially determined, and the polishing load is feedback-controlled.

That is, as shown in FIG. 3, the polishing apparatus 1 employs a PID (proportional integral derivative) method as a feedback control method. Specifically, the tool processing pressure setting unit 20, the PID controller 21, the pneumatic regulator 22, the air cylinder 23,
A polishing load is applied to the load cell 10, the tool 8, and the workpiece 100, and the workpiece 8 is polished by the tool 8. The PID controller 21, the pneumatic regulator 22, and the air cylinder 23 are built in the
The adjuster 21 drives the pneumatic regulator 22 with the target command value set in the tool pressure setting unit 20 and moves the linear motion guide 6 by the air cylinder 23. The polishing load at this time is detected by the load cell 10, and based on the detection result of the load cell 10, the PID controller 21 feedback-controls the drive command value, and drives the pneumatic regulator 22 and the air cylinder 23 to perform the polishing load. Control.

Next, the operation of the present embodiment will be described. In the following description, a case where the inside of a rectangular region is polished on the spherical workpiece 100 will be described as an example.

Now, as shown in FIG. 4, assuming that a region shown by a broken line in FIG. 4 is a polishing region 101 with respect to a workpiece 100 having a spherical shape,
It has a rectangular shape when viewed from the Z direction.

When the polishing area 101 of the workpiece 100 as shown in FIG. 4 is polished by the polishing apparatus 1, the polishing apparatus 1 moves linearly in the Y-axis direction as shown by the solid arrows in FIG. And a turning operation 103 of a predetermined width in the X-axis direction for performing the linear operation, and the tool 8 is brought into contact with the polishing area 101 of the workpiece 100 in a trajectory as shown in FIG. Do. The contact trajectory (hereinafter, referred to as a tool path) 102 is a scanning line having a substantially linear shape when viewed from the Z direction. The tool path 102 includes a linear scanning operation and a switching operation 103.

When performing the polishing process, the polishing apparatus 1 first performs a return operation 1 from the tool path 102.
03 is deleted, and the trajectory of the scanning operation is approximated by an arc. This arc approximation is shown as shown in FIG. As shown in FIG. 6, a method of performing this circular arc approximation is to use a linear motion axis in the Y-axis direction and a workpiece 10 of the tool 8 orthogonal to the linear motion axis.
The tool trajectory is projected on the YZ plane formed by the axis (Z axis) for applying a load to the workpiece surface of the workpiece 0 (dummy work 200), and the projected tool trajectory is approximated by the least-squares method to obtain an approximate circle radius. Ask.

In the arc approximation of the trajectory of the scanning operation, when the polishing area 101 of the workpiece 100 is a complicated free-form surface, a convex arc and a concave arc may be mixed in one scanning line. In such a case, the scanning lines are separated at the inflection points of the convex arc and the concave arc, and the same arc approximation is performed on each of the separated scanning lines.

Now, in the case of a scanning line approximated by a convex arc as shown in FIG. 6, the absolute value of the approximate arc radius Rn of each scanning line is compared, and the minimum approximate arc radius Rmin which becomes the minimum value is obtained.
Find Now, in FIG. 6, R1 <R2 <R3.
When <Rn, the approximate arc radius R1 is the minimum approximate arc radius Rm
Let it be in.

Next, as shown in FIG. 7, a dummy work 200 having the same material as the workpiece 100 and having a cylindrical shape having a curvature radius of the approximate arc radius R1 which is the minimum approximate arc radius Rmin found above is prepared. And the workpiece 10
Polishing conditions for obtaining a target surface roughness in polishing of 0 are experimentally obtained.

That is, as shown in FIG. 7, the dummy work 200 is fixed on the Y-axis table 4 of the polishing apparatus 1 and
While controlling the movement of the axis table 3, the Y-axis table 4, and the linear guide 6, the polishing load is controlled by the pressing mechanism 9,
Polishing of the dummy work 200 with the tool 8
In the polishing of No. 00, polishing conditions for polishing to the target surface roughness of the workpiece 100 by polishing to the target surface roughness, that is, the tool feed speed Fmin, the tool rotation speed Nmin, and the polishing load P To get.

In this polishing experiment, the parameters of the control system of the mechanism for generating the tool load are set to a dull response in the category of the stable state. The dull response means a response state in which the rise time is relatively long with respect to the specified step value and the overshoot amount is relatively small. This step response waveform is shown in FIG. 8, where the rise time refers to the time required for 10% to 90% of the target value, and the overshoot amount refers to the ratio (%) of the overshoot amount to the target value.

When the target surface roughness is secured by the above polishing experiment, the deterioration of the shape is evaluated. In the evaluation of shape deterioration, the dummy work 200 has a cylindrical shape, and its cross section is a circular arc. In the evaluation of shape deterioration, reduction of the radius of curvature does not matter.

The evaluation result of the shape deterioration can be shown in FIG. 9. In FIG. 9, the outer peripheral edge is deeply removed and both ends are sagged. Such shape collapse can be improved by adjusting the response characteristics of the load control without changing the polishing processing conditions. Specifically, the sagging of the outer peripheral edge can be improved by adjusting the rise time in FIG. 8, and the disturbance at the top can be improved by adjusting the overshoot amount. . Further, in order to remove the undulation on the surface, it is effective to make the response as dull as possible within a range where the roundness accuracy is not lost.

By a polishing experiment using the dummy work 200, a basic tool feed speed Fmi was set as a basic processing condition.
n, the basic tool rotation speed Nmin, and the polishing load P can be determined, and adjustment of the polishing load control system (setting of the response condition of the polishing load P) can be performed.

Next, based on the relationship between the minimum radius of curvature Rmin and the basic tool feed speed Fmin, the feed speed F2 of the scanning line path having other radiuses of curvature R2, R3,..., Rn shown in FIG. , F3,..., Fn.

In this case, based on the following equation (2) derived from the ratio of the following equation (1), the tool feed speeds F2, F3,.
・ Calculate Fn.

Rmin: Fmin = Rn: Fn (1) Fn = (Fmin × Rn) / Rmin (2) That is, the radius of curvature R other than the minimum radius of curvature Rmin
The tool feed speed F of the contact locus of 2, R3, ..., Rn
2, F3,..., Fn are defined as the radius of curvature R of the contact locus.
2, R3,..., Rn and the minimum radius of curvature Rmin.

In this way, the radii of curvature R2, R3,... Different from the minimum radius of curvature Rmin, which is the basic radius of curvature, are set.
· Polishing can be performed on the surface to be processed having Rn without destroying the front shape.

Finally, the tool rotation speed Nn in each scanning line is set in order to make the removal depth of each scanning line uniform. Since the polishing removal depth is substantially proportional to the feed amount per one rotation of the tool, the tool rotation speed Nn is determined based on the following equation (4) derived from the ratio of the following equation (3).

Fmin: Nmin = Fn: Nn (3) Nn = (Nmin × Fn) / Fmin (4) By executing the above procedure, the tool feed which is the polishing processing condition of each scanning line is performed. The speed Fn and the tool rotation speed Nn are determined. The polishing load P is common regardless of the scanning line.

The polishing conditions are performed according to the procedure shown in FIG. That is, first, the traverse direction is determined (step S101), and the locus of the tool contact point is obtained (step S102). Next, each section is approximated by an arc to determine a minimum radius of curvature Rmin (step S103). For the dummy work 200 having the cylinder surface having the minimum radius of curvature Rmin as the radius of curvature, and made of the same material as the workpiece 100, Feed rate F, which is a processing condition such that the surface roughness satisfies the target surface roughness in polishing the workpiece 100
min and the tool rotation speed Nmin are experimentally obtained (step S104).

It is checked whether or not the front shape (roundness) of the dummy work 200 polished in the experiment has been broken (step S1).
05), when the roundness is not broken, the processing conditions experimentally obtained are determined as basic processing conditions Fmin and Nmin (step S106).

When the roundness of the polished dummy work 200 is broken in the experiment, the gain and damping performance of the pressure control system are changed to adjust the responsiveness so that the roundness is maintained (step S107). ), The experimentally determined processing conditions are determined as basic processing conditions Fmin and Nmin (step S106).

Next, each scanning section R2, R3,.
n based on the ratio of the approximate radius of curvature Rn (n = 1, 2,..., n) to the minimum radius of curvature Rmin (Rmin: Rn =
Fmin: Fn), each scanning section R2, R3,.
The tool feed speed Fn at n (n = 1, 2,..., n) is determined (step S108).

Finally, each scanning section R2, R3,.
The tool rotation speed Nn in each scanning section R2, R3,..., Rn is determined so that the tool feed amount per rotation of the tool at Rn becomes equal (step S109).

When the tool feed speed Fn, the tool rotation speed Nn, and the polishing load P, which are the polishing processing conditions, are determined in this manner, the workpiece 100 to be processed is moved to the Y-axis table 4.
The workpiece 100 is polished with the tool feed speed Fn, the tool rotation speed Nn, and the polishing load P, which are the above polishing conditions.
Polishing.

As described above, according to the curved surface processing method of the present embodiment, the processing surface (polishing region) 1 of the workpiece 100 of the tool 8 is
01 is approximated by an arc, and a dummy workpiece (dummy work) 200 having an arc cross section having the same radius of curvature as the minimum radius of curvature R1 in the arc approximation is preliminarily processed.
The tool feed speed, the tool rotation speed, and the response condition of the load control are determined, and the workpiece 100 is machined based on the determined tool feed speed, the tool rotation speed, and the response condition of the load control.

Therefore, without using a complicated device such as four-axis control and a machining program, a tool orthogonal to the tool load axis can be used.
The free-form surface can be accurately and simply machined at low cost by using the polishing apparatus 1 which is a conventional simple curved-surface processing apparatus composed of a shaft NC table.

Further, the curved surface machining method of the present embodiment uses a rise time and an overshoot amount with respect to a step command value of the load control of the tool 8 as a response condition of the load control.

Therefore, irrespective of the skill level of the operator, the machining can be performed without changing the tool feed speed and while suppressing the deterioration of the shape. Can be processed.

Further, the curved surface processing method of the present embodiment
Radius of curvature R2, R3 other than the minimum radius of curvature Rmin,
..., the tool feed speeds F2, F3, ... of the contact locus of Rn
.., Fn by the radii of curvature R2, R3,.
.. Are determined based on the ratio between Rn and the minimum radius of curvature Rmin.

Therefore, the tool feed speed can be increased in proportion to the radius of curvature to perform machining with higher machining efficiency, and the delay in following an unnecessary high-period surface undulation is increased, thereby increasing the surface undulation. The removal performance can be improved, and the free-form surface can be more accurately processed.

In the curved surface machining method according to the present embodiment, as the scanning of the tool 8, a linear motion in the Y-axis direction and a folding operation of a predetermined width in the X-axis direction for performing the linear motion are performed. As a contact trajectory for performing approximation, a trajectory of scanning of only a linear motion in one axial direction excluding the folding operation is employed.

Therefore, compared to simultaneous two-axis feed, mechanical motion errors are less likely to occur, so that a highly accurate machining can be performed with a general-purpose machining machine, and the polishing tool is scanned. NC programs can be created more easily and in a shorter time, at lower cost, and
A free-form surface can be easily processed accurately.

Further, the curved surface processing method of the present embodiment
The circular arc approximation of the contact trajectory of the tool 8 is defined by a plane (X axis) formed by a linear motion axis (Y axis) and a load application axis (X axis) orthogonal to the linear motion axis and applied to the work surface of the workpiece 100 of the tool 8. The tool trajectory is projected in the (YZ plane), and the projected tool trajectory is obtained by approximation using the least square method.

Therefore, even when the contact trajectory bends when viewed from the tool load axis direction, the radius of curvature corresponding to the response of the load control can be easily and accurately obtained, and the free-form surface can be more accurately formed. Can be processed.

Further, according to the curved surface machining method of the present embodiment, when the workpiece surface of the workpiece 100 includes both a convex curved surface and a concave curved surface, the tool trajectory is divided by the inflection points of the convex curved surface and the concave curved surface.
Arc approximation is performed for each of the tool trajectory of the convex curved surface and the tool trajectory of the concave curved surface.

Therefore, even on a complicated free-form surface where the tool path forms a convex arc and a concave arc, high-precision machining can be performed.

Further, the curved surface processing method of the present embodiment
Since it is applied to the polishing of the work surface of the work,
Without using a complicated device such as axis control and a machining program, using a conventional simple curved surface polishing device composed of an NC table of two axes orthogonal to the polishing load axis, the tool feed speed,
Quickly determine tool rotation speed and load control response conditions,
The free-form surface can be accurately and precisely polished at low cost.

Then, by using the polishing processing conditions determined by the same procedure as described above, uniform polishing while maintaining the front shape even on a free-form surface can be easily realized by a processing machine based on a biaxial NC. be able to.

Although the invention made by the inventor has been specifically described based on the preferred embodiments, the present invention is not limited to the above-described embodiment, and various modifications may be made without departing from the gist of the invention. It goes without saying that it is possible.

For example, in the above-described embodiment, a dummy workpiece (dummy work 200) having an arc cross section having a minimum radius of curvature is preliminarily machined to determine a tool feed speed, a tool rotation speed, and response conditions for load control. Although it has been determined, a database of the tool feed speed, the tool rotation speed, and the response condition of the load control determined by pre-processing a dummy workpiece having an arc cross section having various curvature radii is created, and the minimum radius of curvature is obtained. The tool feed speed, the tool rotation speed, and the response condition of the load control may be read from the database based on the minimum radius of curvature and determined.

In this way, the tool feed speed, the tool rotation speed, and the response condition of the load control can be quickly determined, and the free-form surface can be accurately and inexpensively machined more accurately.

In the above embodiment, the present invention is applied to the case where the workpiece is polished. However, the present invention is also applicable to the case where the surface of the workpiece is cut or ground. In this case, it can be easily applied to the processing machine configuration in which the cutting axis of the fixed size of the tool load axis is replaced, and the free-form surface can be created with high precision. Can be cut or ground.

[0083]

According to the method for machining a curved surface according to the first aspect of the present invention, the load of the tool is made substantially constant while the tool having a smaller diameter than the workpiece is rotated around the axis at a predetermined tool rotation speed. When processing a curved surface by scanning a predetermined trajectory at a predetermined tool feed speed, the contact trajectory of the tool with respect to the processing surface of the workpiece is circularly approximated, and the circular arc approximation has the same radius of curvature as the minimum radius of curvature. Preliminary machining of the dummy workpiece having an arc cross section determines the tool feed speed, tool rotation speed and load control response conditions, and based on the determined tool feed speed, tool rotation speed and load control response conditions, Since the workpiece is machined, the conventional simple curved surface machining device consisting of a tool load axis and a 2-axis orthogonal NC table can be used at low cost without using complicated equipment such as 4-axis control and machining programs. And easy It can be processed free-form surface accurately.

According to the curved surface machining method according to the second aspect of the present invention, the load of the tool is made substantially constant while rotating the tool having a smaller diameter than the workpiece around the axis at a predetermined number of rotations of the tool. When processing a curved surface by scanning the trajectory at a predetermined tool feed speed, the contact trajectory of the tool with respect to the processing surface of the workpiece is circularly approximated, the minimum radius of curvature of the circular arc approximation is obtained, and the various radii of curvature are calculated. From a database of tool feed speed, tool rotation speed and load control response conditions determined by pre-machining a dummy workpiece having an arc cross section, the tool feed speed, tool rotation speed and load control are determined based on the minimum radius of curvature. The response condition is read, and the read tool feed speed,
Since the workpiece is machined based on the tool rotation speed and the response conditions of the load control, the NC of the tool load axis and two axes orthogonal to the tool load axis can be used without using complicated equipment such as 4-axis control and a machining program.
Using a conventional simple curved surface processing device consisting of a table, the tool feed speed, tool rotation speed, and response conditions for load control are quickly determined, and a free-form surface can be accurately and accurately made at low cost. Can be processed.

According to the curved surface machining method of the present invention, since the rise time and the overshoot amount with respect to the step command value of the load control of the tool are used as the response conditions of the load control, the skill level of the operator can be improved. Regardless,
The machining can be performed without changing the tool feed speed and while suppressing the deterioration of the shape, and the free-form surface can be accurately and easily machined at low cost.

According to the curved surface machining method of the present invention, the tool feed speed of the contact locus having a radius of curvature other than the minimum radius of curvature is determined based on the ratio of the radius of curvature of the contact locus to the minimum radius of curvature. The tool feed speed can be increased in proportion to the radius of curvature to perform machining with higher machining efficiency.In addition, the following delay for unnecessary high-period surface waviness is strengthened, and surface waviness is reduced. The removal performance can be improved, and the free-form surface can be more accurately processed.

According to the curved surface machining method of the present invention, as the scanning of the tool, a linear motion in the X-axis direction or the Y-axis direction and a predetermined motion in the Y-axis direction or the X-axis direction for performing the linear motion. As the contact trajectory for performing the wrapping operation of the width and performing the arc approximation, the trajectory of the scanning of only the linear motion in the one axis direction excluding the wrapping operation is adopted.
Compared to axial feed, mechanical motion errors are less likely to be introduced, so that high-precision processing can be performed with a general-purpose processing machine, and the NC program for scanning the polishing tool can be made simpler and shorter. The free-form surface can be created in a short time, and the free-form surface can be accurately and easily processed at a lower cost.

According to the curved surface machining method of the present invention, as the scanning of the tool, a linear motion in the X-axis direction or the Y-axis direction and a predetermined motion in the Y-axis direction or the X-axis direction for performing the linear motion. The width of the tool is wrapped around, and the circular approximation of the contact trajectory of the tool is made in the plane formed by the linear motion axis and the axis that is orthogonal to the linear motion axis and that applies the load to the workpiece surface of the workpiece. Is calculated by approximating the projected tool trajectory by the least-squares method. Therefore, even when the contact trajectory bends when viewed from the tool load axis direction, the curvature radius corresponding to the response of the load control is obtained. Can be easily and accurately obtained, and the free-form surface can be more accurately processed.

According to the curved surface machining method of the present invention, when the surface to be machined of the workpiece has both a convex curved surface and a concave curved surface, the tool trajectory is divided by the inflection points of the convex curved surface and the concave curved surface. ,
Since arc approximation is performed for each of the tool trajectory of the convex curved surface and the tool trajectory of the concave curved surface, high-precision machining is performed even on a complicated free-form surface where the tool trajectory forms a convex circular arc and a concave circular arc. be able to.

According to the curved surface processing method of the present invention, since the curved surface processing method is applied to the polishing of the surface to be processed of the workpiece, a complicated apparatus such as four-axis control and a processing program are used. Without using the N, N of two axes orthogonal to the polishing load axis
Using a conventional simple curved surface polishing device composed of a C table, the tool feed speed, tool rotation speed and response conditions for load control are quickly determined, and a free-form surface can be accurately and inexpensively more easily and accurately. Can be polished.

According to the curved surface machining method of the ninth aspect, the curved surface machining method is applied to the cutting or grinding of the surface to be machined of the workpiece, so that the cutting shaft having a fixed dimension of the tool load axis. The present invention can be easily applied to a processing machine configuration that has been replaced with the above, and can perform free-form surface creation processing with high accuracy, and can perform high-precision cutting or grinding processing while suppressing surface undulations.

[Brief description of the drawings]

FIG. 1 is a front view of a polishing apparatus to which an embodiment of a curved surface processing method according to the present invention is applied.

FIG. 2 is an enlarged perspective view of a tool and a workpiece of FIG. 1;

FIG. 3 is a control block diagram of the polishing apparatus of FIG. 1;

FIG. 4 is an enlarged perspective view showing a polished region of a workpiece to be subjected to curved surface processing;

FIG. 5 is a diagram showing a contact locus (tool path) of a workpiece in FIG. 4;

FIG. 6 is a view showing a state where the tool path of FIG. 5 is approximated by an arc;

FIG. 7 is an enlarged perspective view of a dummy work and a tool showing a state in which a cylindrical dummy work is being experimentally polished to determine polishing conditions.

FIG. 8 is a diagram showing a step response waveform.

FIG. 9 is a view showing a shape evaluation result of preliminary polishing of a dummy work.

FIG. 10 is a flowchart showing a procedure for determining polishing conditions.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Polishing apparatus 2 Base 3 X-axis table 4 Y-axis table 5 Linear guide shaft 6 Linear guide 7 Spindle 8 Tool 9 Pressurizing mechanism 10 Load cell 11 Weight 20 Tool processing pressure setting part 21 PID regulator 22 Pneumatic regulator 23 Air cylinder 100 Workpiece 101 Polishing area 102 Contact locus 103 Switching operation 200 Dummy work

Continuation of the front page F term (reference) 3C001 KA01 KB07 TA05 TA06 3C049 AA03 AA11 AA16 AB01 AB06 BA01 BA02 BA04 BA05 BB02 BB08 BC01 BC02 CA01 CA03 CB01 CB05

Claims (9)

[Claims] 1. A tool having a diameter smaller than that of a workpiece is rotated around a predetermined axis at a predetermined number of revolutions while the load of the tool is kept substantially constant, and a predetermined locus is scanned at a predetermined tool feed speed. In a curved surface machining method for machining a curved surface, a contact locus of the tool with respect to a surface to be machined of the workpiece is approximated by an arc, and a dummy workpiece having an arc cross section having the same radius of curvature as a minimum radius of curvature of the arc approximation. Preliminary machining, determine the tool feed rate, tool rotation speed and load control response conditions,
A curved surface machining method, wherein the workpiece is machined based on the determined tool feed speed, tool rotation speed, and response condition of load control. 2. A tool having a diameter smaller than that of a workpiece is rotated around a predetermined axis at a predetermined rotational speed while the load of the tool is kept substantially constant, and a predetermined locus is scanned at a predetermined tool feed speed. In the curved surface machining method for machining a curved surface, a contact locus of the tool with respect to a surface to be machined of the workpiece is approximated by an arc, a minimum radius of curvature is determined from the arc approximation, and a dummy having a circular cross section having various radii of curvature is obtained. -Read out the tool feed speed, tool rotation speed and load control response condition based on the minimum radius of curvature from a database of tool feed speed, tool rotation speed and load control response condition determined by pre-processing the workpiece in advance. And processing the workpiece based on the read tool feed speed, tool rotation speed, and response condition of load control. 3. The curved surface machining method according to claim 1, wherein a rising time and an overshoot amount with respect to a step command value of the load control of the tool are used as response conditions of the load control. Curved surface processing method. 4. The method for machining a curved surface according to claim 1, wherein a tool feed speed of a contact locus having a radius of curvature other than the minimum radius of curvature is determined based on a ratio between the radius of curvature of the contact locus and the minimum radius of curvature. The curved surface processing method according to any one of claims 1 to 3, wherein: 5. The curved surface machining method according to claim 1, wherein the scanning of the tool includes a linear motion in the X-axis direction or the Y-axis direction and a folding operation of a predetermined width in the Y-axis direction or the X-axis direction for performing the linear motion. And a scanning locus of only the linear motion in one axial direction excluding the turning motion is adopted as a contact locus for performing the arc approximation.
The curved surface processing method according to any one of claims 1 to 4. 6. The curved surface machining method according to claim 1, wherein the scanning of the tool includes a linear motion in an X-axis direction or a Y-axis direction and a folding operation of a predetermined width in the Y-axis direction or the X-axis direction for performing the linear motion. And the circular approximation of the contact trajectory of the tool,
Projecting a tool trajectory in a plane formed by a linear motion axis and an axis for applying a load to the workpiece surface of the workpiece perpendicular to the linear motion axis and the tool, and projecting the tool trajectory by the least square method. 6. The method according to claim 1, wherein the value is obtained by approximation.
The method for processing a curved surface according to any one of the above. 7. The curved surface machining method according to claim 1, wherein, when the surface to be machined of the workpiece has both a convex curved surface and a concave curved surface, the tool trajectory is divided by an inflection point of the convex curved surface and the concave curved surface. 7. The curved surface machining method according to claim 1, wherein the circular arc approximation is performed for each of a tool path and a tool path of a concave surface. 8. The curved surface processing method according to claim 1, wherein said curved surface processing method includes polishing a surface to be processed of said workpiece. 9. The curved surface machining method according to claim 1, wherein said curved surface machining method comprises cutting or grinding a surface to be machined of said workpiece.