JP2001282332A - Nc data preparing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an NC data preparing method for preparing NC data for performing a machining by simultaneous biaxial machining with nano-meter order precision. SOLUTION: In this NC data preparing method of a tool path 4 at the time of machining a work 2 with high precision by simultaneous biaxial machining by fixing one axial value among coordinate values, tool central coordinates C0 are calculated on a normal at an arbitrary point set by a prescribed pitch on the work 2, and a point on the work 2 is offset only by differential quantity (a) between the value on the fixed axis of the tool central coordinates C0 and the fixed value, and tool central coordinates C1 is recalculated on the normal at this offset point, and that operation is repeated until the differential quantity (a) can reach the prescribed value of a nano-meter order or less. Thus, it is possible to decide tool ]central coordinates C, and to calculate the tool central coordinates C corresponding to each point on the work 2, and to calculate tool passage coordinates based on those tool central coordinates. Therefore, it is possible to prepare NC data.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for preparing NC data of a tool path when cutting a workpiece having a three-dimensional free-form surface or the like with high accuracy.

[0002]

2. Description of the Related Art Generally, a CAD / CAM system is used to generate NC data of a tool path when cutting a workpiece having a three-dimensional free-form surface or the like. CAD
In the CAM system, a group of points on the machined surface is obtained from an expression representing the shape of the free-form surface and its constant, and an approximated surface of the curved surface is created from the group of points. Then, for each coordinate point on the approximated surface, a set of points moved by the tool radius in the normal direction is obtained,
Creating NC data. Usually, the accuracy of such NC data is about 1 μm due to the limitation of the number that can be input to the CAD / CAM system. Since the accuracy required when machining a free-form surface mold or the like is several nm, instead of the above-described method, a point group obtained by dividing the machining surface into necessary accuracy is obtained, and a tool is set in a normal direction of each point. It is said that a machining method that uses a point moved by the radius as a tool position and a group of points at the tool position as a tool path is good.

When a non-axisymmetric or aspherical surface such as a free-form surface is machined, three-axis machining is performed by simultaneous three-axis control. However, as the number of axes to be controlled increases, machine motion errors accumulate. Therefore, two-axis machining is performed, in which machining is performed by fixing the coordinates of one axis (usually the Y axis) in one line during machining rather than three-axis machining. In the NC data creation method,
The tool Y coordinate in one line during machining does not become a constant value, and machining is performed with the tool center Y coordinate during machining being constant.
It is difficult to find C data.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and is intended to generate NC data for performing cutting by simultaneous biaxial machining with an accuracy on the order of nanometers. It is an object to provide a data creation method.

[0005]

According to the present invention, there is provided a tool for cutting a workpiece with high precision by simultaneous two-axis machining while fixing one axis value among coordinate values. In the NC data creation method for a path, a tool center coordinate is obtained on a normal line at an arbitrary point provided at a predetermined pitch on a work, and a point on the work is fixed to a value on a fixed axis of the tool center coordinate and a fixed value. The tool center coordinates are obtained again on the normal line at the offset point by this difference amount (a), and this operation is repeated until the difference amount (a) becomes equal to or smaller than a predetermined value on the order of nanometers. The center coordinates are determined, the tool center coordinates are obtained corresponding to each point on the workpiece, and the coordinates of the tool path are obtained based on these tool center coordinates to obtain NC data.

If the difference (a) does not converge below the predetermined value, the amount of offset of a point on the work is calculated as follows:
It is preferable to prevent divergence by making the difference amount smaller than the difference amount (a).

In the above invention, the difference (a) between the value on the fixed axis of the tool center coordinate located on the normal to the point on the workpiece and the fixed value is converged to a predetermined value on the order of nanometers. Therefore, the tool center coordinates can be brought close to the fixed axis of the processing machine to the order of nanometers. In addition, since the convergence is performed only on the fixed value on one axis, the tool center coordinates can be determined in a short time.

[0008]

FIG. 1 is an enlarged view of a spindle head 1 and a work 2 of a three-axis ultra-precision processing machine controlled based on NC data created by the method of the present invention. The spindle head 1 is provided in parallel with the Y axis, and has a cutting tool 3 at the tip of an arm 1a protruding in a direction perpendicular to the spindle. The spindle head 1 is rotated by a spindle head rotating device (not shown) so that the cutting tool 3 can be turned around the spindle, and the tool center (the cutting edge of the cutting tool 3) The center of curvature is located on the axis of the spindle head 1 in this embodiment.) Can be controlled in three axial directions. When the tool center of the spindle head 1 passes through a predetermined tool path 4 obtained by the NC data creation method described below, the cutting tool 3 cuts the work 2.

Next, a method of creating NC data according to an embodiment of the present invention will be described with reference to a flowchart shown in FIG. In step 101, free-form surface shape data of the workpiece 2 to be processed is read, and in step 102, processing conditions such as a processing range, a processing direction, a tool feed speed, and a feed pitch are set. Next, in step 103, the fixed coordinate y of the Y axis fixed from the machining range in the Y axis direction
= Y ₀ (the starting point is the minimum value of the processing range).

Then, in step 104, FIG.
The coordinates of the feed pitch increment in the X-axis direction of the processing range shown
(X, y₀), The coordinate point that is the minimum value in the X-axis direction
(X₀, Y₀Point S on the surface at₀(X₀, Y₀, Z₀)
In step 105, the point S on the curved surface₀Touch
Tool center coordinate C₀(X₁, Y₁, Z₁). This song
Point S on the surface₀(X₀, Y₀, Z₀) Tool center coordinates C
₀(X₁, Y₁, Z₁) Is the point S₀To the point S₀Unit normal
In the vector direction, move by the tool radius (r) shown in FIG.
Can be obtained by doing And step 1
At 06, the obtained tool center coordinates C shown in FIG.₀of
Y coordinate y = y₁And fixed coordinates y = y₀And the difference amount a (= y₁
-Y₀). In step 107, the difference
If the amount a is 1 nm or less, in step 108,
This tool center coordinate C₀To the point S₀As the tool center coordinates for
To output an NC data file. If a is 1 nm or more
In step 111, the point S on the curved surface₀Y coordinate of
S on a curved surface obtained by offsetting₁(X₀, Y
_Two, Z_Two). Then, returning to step 105,
S ₁With the start point as the starting point, calculate the tool center coordinates again,
Tool center coordinate C₁(X_Three, Y_Three, Z_Three), And the difference a
Repeat until 1 nm or less. Usually this way
If, for example, tens of convergence calculations are performed, the difference amount a becomes
Tool center coordinates can be obtained.

In step 109, it is determined whether or not the point S ₀ is the maximum value in the X-axis direction among the coordinates (x, y) of the feed pitch in the X-axis direction of the processing range. In step 112, the next coordinate S ₀ ′ in increments of the feed pitch in the X-axis direction is obtained, and the flow returns to step 104. As a result, the coordinates S ₀ , S ₀ ′ at every feed pitch in the X-axis direction in the processing range when y = y ₀ .
In S ₀ ″,..., An NC data file is output. If it is the maximum value, in step 110, among the coordinates (x, y) of the feed pitch in the Y-axis direction of the processing range, the Y-axis It is determined whether or not the value is the maximum value in the direction. If the value is not the maximum value, in step 113, the next coordinate T ₀ ′ in increments of the feed pitch in the Y-axis direction is obtained, and the process returns to step 103. An NC data file of the tool center coordinates is output at all points on the work 2 that satisfy the processing conditions in the processing range, if the value is the maximum value in step 110. I do.

FIG. 5 is a flowchart showing a method for creating NC data in a modification of the embodiment of the present invention.
The center coordinates C _{0 of the} tool obtained in step 105
Step 1 of judging whether or not (x ₁ , y ₁ , z ₁ ) is inappropriate, such as being outside the machining range of the workpiece 2 to be machined
And 06-1, a / n of the difference amount a Y coordinate of S ₀ point on the case is not suitable curved (n is an integer) (about typically n = 2)
This is the same as the above-described embodiment except that a step 114 for obtaining a point S ₁ (x ₀ , y ₂ , z ₂ ) on the curved surface offset by only and returning to step 105 is added. Thus, the tool center coordinates C ₀ obtained can be prevented NC data file output when it is unsuitable. Note that even when the convergence calculation shown in the above embodiment does not converge due to a feature unique to the work and diverges, the NC data can be obtained by the same method as in the above modification.

On the basis of the NC data created by the above method, the spindle head 1 is rotated by a spindle head rotating device (not shown) while the Y-axis is fixed by a spindle head control device (not shown) and its tool is rotated. Center is tool path 4
Are controlled so as to continuously pass through the tool center coordinates C, C ′, C ″,.... As a result, the spindle center of the spindle head 1 has the tool center coordinates C, C ', C ", ...
When the cutting tool 3 is at each position, the work 2 is cut at points _St , _St ', _St ",... On the work 2 with which the cutting tool 3 contacts.

The above embodiment is an example in which the tool center C is located on the axis of the spindle head 1 as shown in FIG. 2. However, as shown in FIG. when in position the shaft apart sincerely wheel radius R of the head 1, the rotation locus and the point S ₁ of the cutting edge of the tool obtains a point O in contact at one point, which is referred to as coordinates of the tool path 4.

[0015]

As is apparent from the above description, according to the present invention, NC data for machining an arbitrary free-form surface by simultaneous biaxial machining can be obtained with high accuracy on the order of nanometers in a short time. It has the effect of being able to do so.

[Brief description of the drawings]

FIG. 1 is an enlarged view of a spindle head and a work part of a three-axis ultra-precision processing machine according to an embodiment of the present invention.

FIG. 2 is a side view of the spindle head of FIG. 1;

FIG. 3 is an enlarged schematic view of FIG. 1;

FIG. 4 is a flowchart of an NC data creation method according to the embodiment of the present invention.

FIG. 5 is a flowchart of an NC data creation method according to a modification of the embodiment of the present invention.

FIG. 6 is a side view of a spindle head according to another embodiment.

[Explanation of symbols]

 1 spindle head 2 work 3 cutting tool 4 tool path C, C ', C ", ... Tool center coordinate a Difference amount

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Masayuki Takahashi 1006 Kadoma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. F-term (reference) 5H269 AB05 BB03 CC02 DD01 EE03 GG04

Claims (3)

[Claims] 1. A method in which one axis value is fixed among coordinate values, and
In the method of creating NC data of a tool path when cutting a workpiece with high precision by axis machining, a tool center coordinate is obtained on a normal line at an arbitrary point provided at a predetermined pitch on the workpiece, and a point on the workpiece is defined as the center of the tool. Difference between the value on the axis with fixed coordinates and the fixed value (a)
The tool center coordinate is again obtained on the normal line at the offset point, and this operation is performed by the difference amount (a).
The tool center coordinates are determined by iterating until is less than or equal to a predetermined value on the order of nanometers.The tool center coordinates are obtained for each point on the workpiece, and the tool path coordinates are obtained based on these tool center coordinates. NC data creating method, wherein NC data is used as NC data. 2. The method according to claim 1, wherein when the difference amount (a) does not converge below the predetermined value, an offset amount of a point on the workpiece is made smaller than the difference amount (a). 2. The method according to 1. 3. A tool center coordinate is obtained on a normal line at an arbitrary point provided at a predetermined pitch on the work, and a point on the work is defined as a difference between a value on the fixed axis of the tool center coordinate and the fixed value. Offset by the amount (a), the tool center coordinates are obtained again on the normal line at this offset point, and this operation is repeated until the difference amount (a) becomes equal to or less than a predetermined value on the order of nanometers, thereby obtaining the tool center coordinates. Decide,
The tool center coordinates are obtained for each point on the workpiece, the coordinates of the tool path are obtained based on the obtained tool center coordinates, and the tool is simultaneously subjected to two-axis machining while fixing one axis value among the coordinate values. Processing method that cuts the workpiece by controlling the work.