JP2005028556A - Machining method of free curved surface - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for far more efficiently and precisely performing finish machining of a workpiece having free-form surface than an automatic machining with a ball end mill irrespective of level of skill or level of mastership of an operator when machining the workpiece having free curved surface. <P>SOLUTION: When the neutral direction of a wheel spindle 7 is set to be Y axis and the surface orthogonal to the Y axis is set to be a XZ plane, the line of intersection between imaginary surfaces S<SB>1</SB>, S<SB>2</SB>, etc. parallel to the XZ plane and the workpiece 4 is set with a predetermined pitch P according to the grinding width as the lines C<SB>1</SB>, C<SB>2</SB>, etc.of the grinding direction based on a three-dimensional form data of the workpiece 4. The line orthogonal to at least adjacent two lines of the grinding direction is set with a predetermined pitch as the angle correction lines A<SB>1</SB>, A<SB>2</SB>, etc. and the tool path is set by matching the center of the wheel spindle 7 with the position to offset the angle correction lines A<SB>1</SB>, A<SB>2</SB>, etc. interposed by the two lines of the grinding direction from their positions to the normal direction of the workpiece 4 by the amount of radius r of the grinding wheel. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

The present invention relates to a free curved surface machining method for machining a workpiece having a free curved surface such as a compressor blade.

In order to automatically machine a workpiece having a free-form surface such as a compressor blade, conventionally, an attempt has been made to attach a ball end mill to an NC milling machine or a machining center and perform high-speed machining based on the three-dimensional shape data of the workpiece. Yes.

Since the tip of the ball end mill has a hemispherical shape, even a workpiece having a complicated shape such as a blade is required to use three NC processing machines with three degrees of freedom if the front side and the back side are each one side. Machining can be performed simply by controlling the axis coordinates.

However, since the ball end mill has a small processing area, not only is the productivity low, but there is a problem that the tool wears quickly and the tool must be changed frequently.
For this reason, in order to improve productivity, there are cases where rough machining is performed by a machine and only finishing is performed manually by a skilled worker.

However, for example, a jet engine or the like is provided with 10 or more stages of stationary vanes and rotating blades for compressors having different diameters in the air compression part, and dozens of blades are attached to each stage. Dozens of types of blades, dozens of each, must be processed in hundreds.
In such a case, no matter how much finishing processing is performed, the burden on the operator is great, and the quality of the blade surface is influenced by the skill level and proficiency level, and the processing accuracy must be maintained at a constant quality. There was a problem that was difficult.

Therefore, the present invention, when machining a workpiece having a free-form surface, performs the finishing process much more efficiently and accurately than the automatic machining by the ball end mill, regardless of the skill level or proficiency level of the operator. It is a technical issue.

The present invention is a free-form surface machining method in which a wheel-shaped grindstone is rotated and moved in accordance with the three-dimensional shape data of a workpiece having a free-form surface, and a workpiece is ground on the outer peripheral surface of the cylinder to finish a desired shape. Then, when the neutral direction of the grinding wheel axis is the Y axis and the plane orthogonal to this is the XZ plane, the intersection of the virtual plane parallel to the XZ plane and the workpiece based on the three-dimensional shape data of the workpiece Is set at a predetermined pitch according to the grinding width as a grinding direction line, and at least a line orthogonal to two adjacent grinding direction lines is set as an angle correction line at a predetermined pitch and sandwiched between the two grinding direction lines. The tool path is set by aligning the center of the grindstone axis with the position where the angle correction line is offset from the position in the normal direction of the workpiece by the grindstone radius.

According to the free curved surface machining method of the present invention, when the work material is ground on the cylindrical outer peripheral surface of the wheel-shaped grindstone, the tool path is set so that the center of the grindstone axis coincides with the offset angle correction line. The
When the tool path is set in this way, the center of the grindstone shaft is offset from the angle correction line set on the workpiece surface by the grindstone radius with respect to the normal direction, so that the grindstone attached to the grindstone shaft The cylindrical outer peripheral surface is in contact with the three-dimensional shape data with the angle correction line, and the tangent line accurately overlaps with the angle correction line, so that the adjacent grinding direction lines are ground with high accuracy according to the three-dimensional shape data.
Similarly, by sequentially grinding between the respective grinding direction lines, the work material is ground according to the three-dimensional shape data, and a workpiece having a desired shape can be efficiently and accurately finished. effective.

In this example, when machining a workpiece having a free-form surface, regardless of the skill level or proficiency level of the operator, the purpose of performing the finishing process much more efficiently and accurately than the automatic machining using a ball end mill, This was achieved by grinding using a wheel-shaped grindstone.

FIG. 1 is a conceptual diagram of a machine tool used in the method of the present invention, FIG. 2 is an explanatory diagram showing the relationship between cutting direction lines and angle correction lines of the method of the present invention, and FIG. 3 is an explanatory diagram showing a tool path setting method. 4 is an explanatory diagram showing the curved surface shape of the workpiece and the position of the tool path.
In this example, a compressor blade (workpiece) having a free-form surface is machined using a machine tool such as a 5-axis numerical control machining center having three orthogonal axes of XYZ and two orthogonal rotation axes of θ _X and θ _Z. The case will be described.

The machine tool 1 clamps the rough-cut work material 2 and rotates the wheel-shaped grindstone 5 according to the three-dimensional shape data of the compressor blade (workpiece) 4 read from the NC control device 3 while rotating the grindstone shaft. 7 is moved, and the workpiece 2 is ground by the cylindrical outer peripheral surface 6 of the grindstone 5.
The grindstone 5 of this example uses diamond abrasive grains or CBN abrasive grains formed into a wheel shape using a binder such as vitrified.
Then, when the neutral direction of the grindstone shaft 7 is the horizontal Y-axis, the horizontal direction orthogonal to this is the X-axis, and the vertical direction is the Z-plane, the grindstone shaft 7 and the clamped work material 2 are XYZ Position control is relatively possible with respect to three orthogonal axes and five axes of X axis around θ _X and Z axis around θ _Z.

The NC control device 3 sets the tool path of the grindstone shaft 7 according to the following procedure based on the three-dimensional shape data of the compressor blade 4 input in advance.
First, based on the three-dimensional shape data when it is assumed that the blade 4 is fixed at the same position as the clamped work material 2, the intersection line between the virtual surfaces S ₁ , S ₂ . the set at a predetermined pitch corresponding to the grinding width P as grinding direction line C _1, C 2 _..., grinding direction line C ₁ of _each, C 2 _... orthogonal to the angle correction lines a _1, a 2 _... the finished surface roughness The pitch is set according to the degree, and each intersection is calculated.

Next, based on the intersection coordinates, the angle correction lines A ₁ , A ₂ ... Sandwiched between the two adjacent grinding direction lines C _n , C _{n + 1} are moved from the position to the normal direction of the blade surface of the blade 4. Offset is made by the radius r, and the grindstone axis locus lines CP _n1 , CP _n2 ... _Are set at the positions.
Then, the tool path 8 is set by continuing the grindstone axis trajectory lines CP _n1 , CP _n2 ... Thus set, and the grindstone axis trajectory lines CP _n1 , CP _n2 . The machine tool 1 is controlled with five axes of X, Y, Z, θ _X , and θ _Z so that the centers of the two overlap.

When the tool path 8 is set in this way, the center of the grindstone shaft 7 is offset from the angle correction lines A ₁ , A ₂ ... Set on the surface of the blade 4 by the grindstone radius r relative to the normal direction. Through the angle correction lines A ₁ , A ₂ ...
Thus, the cylindrical outer peripheral surface 6 of the grinding wheel 5 attached to its wheel spindle 7 is the angle correction lines A _1, A 2 _... in contact with the three-dimensional shape data, the tangent and the angle correction lines A _1, A 2 _... is Since it overlaps correctly, between the adjacent grinding direction lines C ₁ and C ₂ is ground with high accuracy according to the three-dimensional shape data.
Similarly, by sequentially grinding between adjacent grinding direction lines C _n and C _{n + 1} , the work material 3 is ground according to the three-dimensional shape data, so that the blade 4 having a desired shape is extremely efficient. There is an effect that it can finish well with high precision.

In the above description, the case where the compressor blade 4 is machined as a workpiece has been described. However, the present invention is applicable to a workpiece having an arbitrary shape having a free-form surface.
Moreover, although the case where the finishing process of the rough-cut work material was performed was demonstrated, you may be made to perform a finishing process from the beginning, without roughing depending on a workpiece.

As described above, according to the present invention, even a workpiece that is difficult to machine with high precision unless it is obtained by a skilled worker such as a compressor blade, regardless of the skill level and proficiency level of the worker. It can be applied to a machine finishing process with high accuracy and high production efficiency.

The conceptual diagram of the machine tool used for this invention method. Explanatory drawing which shows a cutting direction line and an angle correction line. Explanatory drawing which shows the setting method of a tool path. Explanatory drawing which shows the curved surface shape of a workpiece, and the position of a tool path.

Explanation of symbols

1 Machine Tool 2 Work Material 3 NC Controller 4 Compressor Blade (Workpiece)
5 Whetstone 6 Cylindrical outer peripheral surface
7 Wheel axis
8 Tool path S ₁ ... Virtual plane parallel to XZ plane C ₁ ... Grinding direction line A ₁ ... Angle correction line

Claims (1)

A free-form surface processing method for moving a wheel-shaped grindstone while rotating it according to the three-dimensional shape data of a workpiece having a free-form surface, and grinding the work material on the outer peripheral surface of the cylinder, to finish the desired shape,
Based on the three-dimensional shape data of the workpiece, the intersection of the virtual plane parallel to the XZ plane and the workpiece is ground when the neutral direction of the grinding wheel axis is the Y axis and the plane orthogonal to the Y axis is the XZ plane. A direction line is set at a predetermined pitch according to the grinding width, and at least a line orthogonal to two adjacent grinding direction lines is set as an angle correction line at a predetermined pitch and sandwiched between the two grinding direction lines A free curved surface machining method, wherein a tool path is set by aligning a center of a grindstone axis with a position obtained by offsetting an angle correction line from the position in the normal direction of the workpiece by a grindstone radius.

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