JP2008192001A - Method for preparing nc program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To grind an axisymmetric aspherical surface shape presenting an arbitrary shape without generating any interference between a working tool and a workpiece regardless of whether the surface of the workpiece is concave or convex. <P>SOLUTION: In a super-precise working device 4 for bringing a rotating tool grinding stone 19 supported by a tool rotary shaft b inclined by a B axial angle θb to a main shaft rotary axis (a) in contact with a rotating workpiece 20 fixed to the main shaft rotary axis (a) to be ground, software 7 for preparing an NC program which controls a super-precise working device 4 is provided with: a workpiece arithmetic function 11 and a workpiece graphing function 12 for calculating the shape of the workpiece 20, and for outputting it as a graph 20a; a tool orbit arithmetic function 13 and a tool orbit graphing function 14 for calculating the orbit of a tool grinding stone 19, and for outputting it as a graph 19a; and an initial angle input function 16 for changing the B axial angle θb when any interference is generated between the graph 20a and the graph 19a. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a NC (numerical control) program creation technique, for example, a high-precision optical element of a rotationally symmetric aspherical lens used in an optical instrument, or a molding surface portion of a molding die for molding the same. The present invention relates to a method for creating an NC machining program used for production of the above.

  For example, an optical component such as an axisymmetric aspheric lens and a mold for molding the optical component are required to have very high shape accuracy and surface roughness accuracy. The following conventional techniques exist as a method for grinding such a highly accurate optical component.

  For example, Patent Literature 1 discloses a grinding apparatus for normal spherical machining, in which the axial direction of a work spindle to which a workpiece is attached and the axial direction of a grinding wheel spindle to which a grindstone is attached can be obliquely crossed. The surface of the work piece is divided into a plurality of concentric annular zones, and the surface of each annular zone is a spherical surface having a spherical radius that minimizes the error from the corresponding portion in the rotationally symmetric aspheric surface to be processed. A technique for realizing rotationally symmetric aspherical processing as a set of concentric annular zoned spherical surfaces by performing grinding while tilting the workpiece spindle axis direction and the grindstone spindle axis direction from each other is disclosed. .

  In the case of this Patent Document 1, a rotationally symmetric aspherical surface can be processed as a set of concentric circular zone-divided spherical surfaces, and the cup-shaped grindstone ring is used as a grinding action point. Since the grindstone acting point is per line, the processing efficiency is improved and the surface roughness is also improved.

  Next, Patent Document 2 proposes a method for avoiding tool interference. In the case of Patent Document 2, the average inclination angle of the machining curved surface in the machining range of the workpiece is calculated, and when the angle of the workpiece spindle axis direction and the grinding wheel spindle axis direction is tilted to the above angle, the interference check is performed over the entire machining range. If there is no interference, processing is performed with the above calculated angle fixed, and if there is interference, the interference avoidance angle at which interference does not occur is obtained according to a certain theory, and interference occurs from this interference avoidance angle and the above average tilt angle. There has been proposed a method for avoiding interference by obtaining a non-indexing angle.

  However, in the above-described rotationally symmetric aspherical surface processing method of Patent Document 1, for example, when the processing surface of the workpiece has an inflection point, or depending on how the curvature radius of the workpiece is changed, a point or place other than the processing point is used. However, there is a case where the workpiece and the grindstone interfere with each other, and there is a technical problem that it cannot be applied to all rotationally symmetric aspheric surfaces.

Further, in the method of avoiding the interference of the tool disclosed in Patent Document 2 described above, since the machining is performed with a constant angle, the grindstone acting point becomes a point, so the machining amount is reduced and the machining efficiency can be improved. There was no technical problem.
Japanese Patent No. 3482079 Japanese Patent No. 3116129

  The object of the present invention is to provide an axially symmetric aspherical shape grinding process that exhibits an arbitrary shape without causing interference between the machining tool and the workpiece regardless of whether the workpiece surface of the workpiece is concave or convex. It is to provide an NC program creation technique capable of realizing the above.

  Another object of the present invention is to provide an NC program creation technique capable of realizing an axisymmetric aspherical grinding process having an arbitrary shape without reducing machining efficiency.

The present invention is an NC program creation method for machining an axisymmetric curved surface of a workpiece by simultaneous movement control of a plurality of axes,
A first step of creating each machining point sequence according to the curved surface shape setting formula;
A second step of calculating a contour shape of the workpiece from the shape setting formula;
The point of the angle between the first rotation axis of the machining tool and the second rotation axis of the workpiece determined by the first step as the locus of the position of the entire machining tool at each machining point constituting the machining point sequence A third step of calculating from the column;
A fourth step of examining whether there is interference other than the machining point between the locus of the position of the entire machining tool and the contour shape of the workpiece;
A fifth step of branching to the second step by changing the angle between the first axis and the second axis when it is determined in the fourth step that the interference is present;
A sixth step of outputting an NC program for realizing the trajectory of the machining tool obtained in the second step when it is determined in the fourth step that there is no interference;
A method for creating an NC program including

  According to the present invention, an axisymmetric aspherical shape grinding process that exhibits an arbitrary shape without causing interference between the machining tool and the workpiece regardless of whether the workpiece surface of the workpiece is concave or convex. It is possible to provide an NC program creation technique capable of realizing the above.

  Further, it is possible to provide an NC program creation technique capable of realizing an axially symmetric aspherical shape grinding process having an arbitrary shape without reducing the machining efficiency.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[Embodiment 1]
FIG. 1 is a conceptual diagram showing an example of a functional configuration of software for implementing an NC program creation method according to an embodiment of the present invention, and FIG. 2 is a flowchart showing an example of the operation thereof.

FIG. 3 is a conceptual diagram illustrating an example of a machining state in the ultraprecision machining apparatus according to the present embodiment, and FIG. 4 is a schematic perspective view illustrating a configuration example of the ultraprecision machining apparatus according to the present embodiment.
[Constitution]
First, a configuration example of the first embodiment will be described.

  As shown in FIG. 4, the ultraprecision machining apparatus 4 of the present embodiment rotates the Z-axis stage 1 that is controlled to move in the Z-axis direction and the Y-axis direction as a rotation axis at a position facing the Z-axis stage 1. A B-axis table 3 to be operated, an X-axis stage 2 for controlling movement in the X-axis direction, and a controller 5 are provided below the B-axis table 3.

The movement of the three axes of the Z-axis stage 1, the X-axis stage 2, and the B-axis table 3 can be synchronously controlled by the controller 5.
In the ultraprecision machining apparatus 4, during machining, the grinding action point of the tool grindstone 19 (machining tool) is adjusted so that the rotation center axis of the B-axis table 3 coincides.

The control controller 5 of the ultraprecision machining apparatus 4 is connected to the information processing apparatus 6 via a network such as cable wiring.
The information processing apparatus 6 is installed with software 7 that is mounted on the controller 5 and creates an NC program 21 for controlling the ultraprecision machining apparatus 4.

The information processing apparatus 6 includes a computer main body 6a, a display 6b, and an interface cable 6c.
The computer main body 6a is composed of, for example, a central processing unit (not shown) and a computer having a main memory, an external storage device, etc., and the central processing unit executes the software 7 stored in the main memory, so Processing for creating the program 21 is performed.

  The computer main body 6a is connected to the controller 5 via the interface cable 6c, and the NC program 21 created by the information processing apparatus 6 is transferred to the controller 5 via the interface cable 6c.

  The display 6b is a user interface for visualizing and outputting information processed by the computer main body 6a. In the case of the present embodiment, as will be described later, it is possible to display a graph generated by the computer main body 6a.

An example of the internal logical structure of the software 7 installed in the information processing apparatus 6 of this embodiment is illustrated in FIG.
Inside the software 7 of the present embodiment, a workpiece database 8 that can input the shape of the workpiece and save it as data, and a tool database 9 that can input the shape of the machining tool and save it as data A storage area such as a processing condition database 10 can be provided in which processing conditions can be input and saved as data.

  The software 7 includes a workpiece calculation function 11 for calculating a workpiece shape from the workpiece database 8, a workpiece graphing function 12 for drawing a calculation result on a graph, and a workpiece. A tool trajectory calculation function 13 for calculating the machining trajectory of the machining tool using information in the database 8, the tool database 9 and the machining condition database 10, and a tool trajectory for drawing the calculation result on the same graph as the workpiece graphing function 12 A graphing function 14 and an initial angle input function 16 capable of manually inputting the initial angle of the tool rotation axis b of the B-axis table 3 in order to avoid interference are provided.

Further, the software 7 includes an NC conversion function 17 that converts the calculated machining point sequence into a format that can be read by the NC (numerical control) device of the controller 5 of the ultra-precision machining device 4, and the converted point sequence as NC. A file saving function 18 that can save a file as the program 21 is provided.
[Action]
First, the operation of the first embodiment will be described with reference to the drawings. The operation of the first embodiment will be specifically described below, but these do not limit the present invention.

  As shown in FIG. 3, the workpiece 20 is attached to the main shaft rotation axis a (first rotation shaft), and is rotated about the main shaft rotation axis a. Similarly, the tool grindstone 19 is rotated at high speed around the tool rotation axis b (second rotation axis). In this state, according to the NC program 21 stored in the controller 5, the three-axis movement of the X-axis stage 2, the Z-axis stage 1, and the B-axis table 3 is simultaneously controlled by the controller 5. Grinding is performed while scanning the processing surface of the workpiece 20.

In the case of the present embodiment, the NC program 21 for controlling the movement of each axis of the ultraprecision machining apparatus 4 is created by the following method as exemplified in the flowchart of FIG.
First, the software 7 inside the information processing apparatus 6 is activated. Next, the shape of the workpiece 20 is input and registered in the workpiece database 8 (step 101), and the shape of the tool grindstone 19 is input and registered in the tool database 9 (step 102). The processing conditions for performing are registered in the processing condition database 10 (step 103). This is the first step.

  Next, using the information of the workpiece database 8 and the machining condition database 10, the workpiece calculation function 11 calculates the shape of the workpiece surface (step 104) (second step). At this time, the calculation is performed using, for example, an aspherical expression (shape setting expression) represented by the following (Expression A).

However, in (A), x is a coordinate in the radial direction of the workpiece 20, R ₀ is an aspheric curvature radius, k is a conic constant, and C _i is an aspheric coefficient.
After the calculation, the workpiece shape is graphed as a graph 20a by the workpiece graphing function 12, and displayed on the display 6b (step 105).

  Next, using the calculation result of the workpiece calculation function 11 and the information in the tool database 9, the tool path calculation function 13 is used to calculate the tool path (step 106) (third step). The B-axis angle θb at this time is calculated from a B-axis angle conversion formula (shape formula) represented by (B formula).

However, in (b), f ′ (x) is the one-time differential equation of the above (b), d is the diameter of the tool grindstone 19, α is a safety factor, and R (x) is the workpiece. The radius of curvature of the object 20 at the x position, r ₀ is the grindstone nose radius, and B ₀ is the initial angle of the tool rotation axis b.

  At this time, in (b), the left term indicates the angle formed by the vertical axis (normal line) of the machining point and the spindle rotation axis a of the workpiece 20, and the middle term is the diameter of the workpiece 20 at the machining point. The angle formed by the vertical axis (normal line) of the machining point and the spindle rotation axis a of the workpiece 20 is shown in accordance with the curvature radius R (x) in the direction. In addition, the safety factor α is multiplied by the curvature radius R (x) of the workpiece 20.

  After calculating the B-axis angle θb, the tool trajectory graphing function 14 displays the tool trajectory as a graph 19a on the same graph screen as the workpiece shape graph 20a on the display 6b (step 107).

FIG. 5 shows a screen example of the display 6b on which the graph 19a and the graph 20a are displayed.
After displaying the graph 19a and the graph 20a on the display 6b, whether or not there is a place where the tool grindstone 19 and the workpiece 20 interfere at a place other than the grinding point P0 on the entire machining surface as the whole graph is shown in the graph 19a Confirmation is made based on the presence or absence of the intersection of the graph 20a (step 108) (fourth step).

  If interference is found, an appropriate avoidance angle is input to the initial angle input function 16 (step 109) (fifth step), the process returns to step 106, and the tool path calculation function 13 calculates the tool path again. Let After the calculation, the graph 19a is redrawn on the display 6b by the tool locus graphing function 14. When interference is observed, the input of the avoidance angle to the initial angle input function 16 is repeated again until the interference between the tool grindstone 19 and the workpiece 20 disappears.

  If there is no interference, the calculation result of the tool trajectory calculation function 13 is output as a point sequence (step 110) (sixth step). The calculation result includes the wear amount and shape error of the tool grindstone 19, the tool grindstone 19 and An error such as a position error with respect to the B-axis rotation center of the B-axis table 3 is offset and converted into the NC program 21 by the NC conversion function 17 (step 111).

  After the conversion to the NC program 21, the file storage function 18 stores the file of the NC program 21 (step 112). The NC program 21 stored in the file is transferred to the control controller 5 in the ultraprecision machining apparatus 4 via a network such as an interface cable 6c.

After the transfer, according to the point sequence of the NC program 21, the Z-axis stage 1, the X-axis stage 2, and the B-axis table 3 are moved and controlled, and the workpiece 20 is ground.
At this time, at the stage of creating the NC program 21 in the information processing apparatus 6 described above, as described above, the tool grindstone 19 does not interfere with an arbitrary contour shape of the workpiece 20 at a portion other than the grinding point P0. Since the NC program 21 is created, grinding can be performed without any trouble even when the workpiece 20 has an arbitrary contour shape such as a concave surface or a convex surface.

  Further, the tool grindstone 19 and the workpiece 20 are inscribed, and the curvature radius of the tool grindstone 19 and the curvature radius of the workpiece 20 are always close to each other at the grinding action point (grinding point P0). Therefore, the processing is performed with a crescent-shaped line contact.

That is, the amount of grinding per unit time at the grinding point P0 is larger than that in the case of conventional point contact.
[effect]
As described above, according to the grinding process using the NC program 21 created by the NC program creation method of the first embodiment, the machining surface of the workpiece 20 has an arbitrary shape regardless of the concave surface or the convex surface. Grinding can be performed on the symmetrical aspherical shape without causing interference between the tool grindstone 19 and the workpiece 20.

  Further, during grinding, the tool grindstone 19 and the workpiece 20 are inscribed, and the curvature radius of the tool grindstone 19 and the curvature radius of the workpiece 20 at the grinding action point (grinding point P0) are always close. Therefore, processing can be performed with a crescent-shaped line contact. By performing line contact in this way, the number of abrasive grains acting on the grinding area per unit time increases, and high-load machining becomes possible.

As a secondary effect, since the number of abrasive grains acting on the grinding region per unit time increases, an angle is set according to the radius of curvature of the machining point of the workpiece 20 that can improve the surface roughness. An NC program 21 can be created.
[Embodiment 2]
[Constitution]
Next, software 7 for implementing the NC program creation method according to the second embodiment of the present invention will be described with reference to FIG.

  In the case of the second embodiment, an interference calculation function 22 for calculating a difference between the calculation result of the workpiece calculation function 11 and the calculation result of the tool path calculation function 13 in the software 7 exemplified in the first embodiment. The interference determination function 23 for determining interference from the calculation result of the interference calculation function 22 is provided.

Further, instead of the initial angle input function 16, an input value changing function 24 for automatically changing the input value is provided.
In the following, the same components as those in the first embodiment are denoted by the same reference numerals and description thereof is omitted.
[Action]
An example of the operation of the second embodiment will be described with reference to the flowchart of FIG. The difference from the flowchart of FIG. 2 will be described as follows.

  First, as in the case of the above-described first embodiment, the calculation result by the workpiece calculation function 11 and the calculation result by the tool path calculation function 13 are obtained from the workpiece graphing function 12 and the tool path graphing function 14, respectively. The workpiece shape and the tool trajectory are displayed on the same graph (steps 101 to 107).

  Next, the difference between the calculation result of the workpiece calculation function 11 and the calculation result of the tool path calculation function 13 is calculated from the interference calculation function 22 (step 121). Thereafter, the interference determination function 23 checks whether there are several solutions in the difference calculation result (step 122). If there are two or more solutions, it is determined that there is interference.

  If it is determined that there is interference, the input value change function 24 changes the value of the initial angle input function 16 by a set value (for example, a constant value) of an angle variable (not shown) provided in the software 7. (Step 123), the process returns to step 106 described above. Then, a difference is again obtained from the interference calculation function 22, and interference is determined by the interference determination function 23.

  Until the interference is eliminated, the processes of Step 105, Step 107, Step 121, Step 122, and Step 123 are repeated. The above is different from the first embodiment.

The subsequent steps 110 to 112 are the same as those in the first embodiment.
[effect]
According to the second embodiment, the same effects as those of the first embodiment can be obtained, and the tool grindstone 19 and the object to be covered can be obtained by the functions such as the interference calculation function 22 and the interference determination function 23 provided in the software 7. By automatically setting an angle that avoids interference with the workpiece 20, the creation time of the NC program 21 can be shortened.

  As described above, according to the NC program creation method according to each of the above-described embodiments of the present invention, the workpiece surface of the workpiece is an axisymmetric aspherical surface that exhibits an arbitrary shape regardless of a concave surface or a convex surface. When grinding the shape, there is no interference between the tool grindstone and the work piece, the tool grindstone and the work piece are inscribed, and the curvature radius of the tool grindstone and the curvature radius of the work piece at the grinding action point, It is possible to create an NC program that performs machining with a crescent-shaped line contact by making it possible to set it to be always close.

  That is, according to the NC program obtained by the present embodiment, the B-axis angle θb corresponding to the radius of curvature of the machining point of the workpiece is set, so that the tool grindstone 19 is in line contact with the workpiece 20. Therefore, the number of abrasive grains acting on the grinding per unit time increases, and high-load machining becomes possible. Further, as a secondary effect, the number of abrasive grains acting on the grinding process per unit time increases, so that the surface roughness can be improved.

Needless to say, the present invention is not limited to the configuration exemplified in the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention.
For example, the processing tool is not limited to a tool grindstone, and may be another processing tool.

It is a conceptual diagram which shows an example of the function structure of the software which implements the preparation method of NC program which is one embodiment of this invention. It is a flowchart which shows an example of the effect | action. It is a conceptual diagram which shows an example of the processing state in the ultraprecision processing apparatus which is one embodiment of this invention. 1 is a schematic perspective view illustrating a configuration example of an ultraprecision machining apparatus according to an embodiment of the present invention. It is a conceptual diagram which shows an example of the display screen during the accident of NC program which is one embodiment of this invention. It is a conceptual diagram which shows an example of the function structure of the software which implements the preparation method of NC program which is another embodiment of this invention. It is a flowchart which shows an example of the effect | action.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Z-axis stage 2 X-axis stage 3 B-axis table 4 Ultra precision processing apparatus 5 Control controller 6 Information processing apparatus 6a Computer main body 6b Display 6c Interface cable 7 Software 8 Workpiece database 9 Tool database 10 Processing condition database 11 Workpiece Calculation function 12 Workpiece graphing function 13 Tool path calculation function 14 Tool path graphing function 16 Initial angle input function 17 NC conversion function 18 File saving function 19 Tool grindstone 19a Graph 20 Workpiece 20a graph 21 NC program 22 Interference calculation Function 23 Interference judgment function 24 Input value change function B0 Initial angle P0 Grinding point a Spindle axis b Tool rotation axis θb B axis angle

Claims (8)

An NC program creation method for machining an axisymmetric curved surface of a workpiece by simultaneous movement control of a plurality of axes,
A first step of creating each machining point sequence according to the curved surface shape setting formula;
A second step of calculating a contour shape of the workpiece from the shape setting formula;
The point of the angle between the first rotation axis of the machining tool and the second rotation axis of the workpiece determined by the first step as the locus of the position of the entire machining tool at each machining point constituting the machining point sequence A third step of calculating from the column;
A fourth step of examining whether there is interference other than the machining point between the locus of the position of the entire machining tool and the contour shape of the workpiece;
A fifth step of branching to the second step by changing the angle between the first axis and the second axis when it is determined in the fourth step that the interference is present;
A sixth step of outputting an NC program for realizing the trajectory of the machining tool obtained in the second step when it is determined in the fourth step that there is no interference;
A method for creating an NC program, comprising: The NC program creation method according to claim 1,
An NC program creation method, wherein an angle formed between the first rotation axis and the second rotation axis is set according to a radius of curvature at each machining point of the workpiece. The NC program creation method according to claim 1,
An NC program creation method, characterized in that an angle formed between the first rotation axis and the second rotation axis is set according to an inclination of a normal line at each machining point of the workpiece. The NC program creation method according to claim 1,
In the fourth step, a step of drawing a graph of the contour shape of the workpiece;
Drawing a graph of the overall trajectory of the machining tool at each machining point;
Outputting a determination result of interference when there is a portion that intersects the contour shape graph and the trajectory graph;
A method for creating an NC program, comprising: The NC program creation method according to claim 1,
In the fourth step,
Calculating a shape setting expression representing the shape of the workpiece;
Calculating a shape formula representing the entire trajectory of the machining tool;
Obtaining a difference between the shape setting formula and the shape formula;
Obtaining a solution from the calculation result of the difference between the shape setting formula and the shape formula;
Determining that there is interference when there are two or more of the solutions including the processing point within a predetermined processing range;
A method for creating an NC program, comprising: The NC program creation method according to claim 1,
In the fifth step, the NC program creating method is characterized in that an angle formed between the first rotating shaft and the second rotating shaft is changed by manual setting. The NC program creation method according to claim 1,
In the fifth step, the NC program creation method is characterized in that the angle formed by the first rotating shaft and the second rotating shaft is changed by adding the value of an angle variable. The NC program creation method according to claim 7,
The method of creating an NC program, wherein the value of the angle variable is a constant.