JP2845710B2 - Machining method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a machining method, and more particularly to a machining method using an NC machine tool having a rotary feed shaft.
While avoiding interference between the workpiece and the tool system in the grinding process, use a spherical tool such as a ball end mill and defeat the tool as much as possible, and the outer periphery of the cutting edge at the tool tip farthest from the tool axis is the workpiece. The present invention relates to a machining method for performing continuous machining by improving the machining ability of a tool by machining in contact.

[0002]

2. Description of the Related Art In the processing of a workpiece having a curved surface, triaxial processing is mainly performed using a ball end mill or a grinding wheel with a shaft having a spherical tip. When performing axis machining, interference occurs between the workpiece and the tool gripping portion. In order to avoid this interference, lengthen the protruding length of the tool or change the mounting position of the work, for example,
By rotating the A-axis and the B-axis of the axis machine tool, the workpiece is indexed several times in an easy-to-machine direction, and the relative posture between the workpiece and the tool grip is changed to perform the machining.

[0003]

FIG. 7 is an explanatory view of a conventional three-axis machining method. In the three-axis machining, a ball end mill 71 is used as a tool, and a tool holder 72 or a tool holder for holding the ball end mill 71 is used. 7 shows a state in which a main shaft 73 that grips 72 interferes with a work 74 in an interference area 75. To avoid this interference, the tool length may be increased from l1 to l2. However, if the tool length is increased, the position of the tip of the tool is shifted during machining, thereby reducing machining accuracy. Since the vibration disappears and chatter vibration occurs, there is a problem that the cutting feed speed must be reduced and the machining efficiency is reduced.

FIG. 8 is an explanatory view of a five-axis interrupted machining method according to the prior art. When a tool holder 82 for holding a ball end mill 81 or a main shaft 83 for holding the tool holder 82 interferes with a work 84 in an interference area 85. An example in which the work 84 is rotated clockwise by θ ° around the A-axis or the B-axis in five-axis machining to avoid the interference will be described. In this case, the rotation angle is intermittently indexed several times in a direction in which the workpiece can be easily processed, and the X-axis, Y-axis, and Z-axis processing are performed by setting the A-axis and the B-axis at a predetermined angle. There is a problem that the setup requires time and labor. In addition, since the workpiece is machined by indexing several times, a step of several microns occurs between the machining surfaces machined in different indexing postures,
There is a problem that the machined surface is not smooth, and it takes time and effort to work the workpiece surface in the finishing process. In order to solve this problem, it is conceivable to perform surface processing continuously.

On the other hand, when a spherical tool such as a ball end mill is used, and the above-mentioned interference is avoided to process the work alone, the tool axis is often made substantially perpendicular to the work, and the tool is actually used. In addition, there is a problem that the rotation speed of the cutting portion that comes into contact with the workpiece is reduced, and the machining ability of the tool cannot be exhibited. Particularly, in the case of a small-diameter tool, there is a problem that a machining defect occurs unless the tool rotation speed is set to an excessively high speed.

Accordingly, an object of the present invention is to eliminate the above-mentioned problems, that is, to avoid the interference between the workpiece and the tool gripping portion and to tilt the tool as far as possible to cut the cutting edge at the tool tip farthest from the tool axis. Since the outer peripheral part is in contact with the workpiece, the tool can be machined in the part where the rotational speed of the cutting part where the tool actually contacts the workpiece is high, improving the machining capability of the tool. It is an object of the present invention to provide a machining method for performing continuous machining without using the same.

[0007]

FIG. 1 is a flow chart showing the basic processing of a machining method according to the present invention. In order to achieve the above object, the machining method according to the present invention comprises three linear feed axes orthogonal to each other, that is, an X axis, a Y axis, and a Z axis;
At least one of the B-axis rotating around the Y-axis or the Y-axis is mounted on the rotary spindle of the NC machine using a tool having an arcuate cutting edge at the tip. In the machining method for machining a workpiece by using the method, the method includes the following steps.

(First stage) Shape data as data representing the shape of a workpiece to be processed is stored. (Second stage) The shape data of the conical interference model obtained by connecting the tool center point at the tip of the tool and the tool holder for holding the tool or the outermost portion of the main spindle for holding the tool holder is stored. (Third step) While feeding a tool according to a previously specified tool path, the angle between a tangent drawn in the tool advancing direction on the tool path and the tool axis is determined based on the workpiece shape data and the cone shape interference model shape data. And the minimum angle for avoiding interference that is minimized within a range where the interference model does not interfere with the conical interference model. (Fourth step) The A-axis or B-axis rotary feed shaft is rotated, and the relative posture between the workpiece and the tool is changed so that the angle between the tangent and the tool axis is the minimum angle for avoiding interference.

[0009]

FIG. 2 is a block diagram of the control means of the present invention.
A control unit 21 comprising a CPU for controlling the whole, a work shape data storage unit 22 for storing work shape data, a cone shape interference model data storage unit 23 for storing cone shape interference model data described later, A machining program storage unit 24 that stores a machining program mainly including a moving path of the tool, and an A that drives an A axis that is a rotation axis around the X axis and a B axis that is a rotation axis around the Y axis of the 5-axis NC machine tool 26. , B-axis drive unit 25.

The control unit 21 stores the work shape data storage unit 2
From the workpiece shape data stored in the storage unit 2 and the cone shape interference model shape data stored in the cone shape interference model data storage unit 23, a tangent at each position of the tool along the tool movement path and the tool axis are formed. An interference avoidance minimum angle is calculated so that the angle is minimized within a range where the workpiece does not interfere with the conical interference model. Next, A axis or B
The A / B axis drive unit 25 is controlled to rotate the feed axis of the shaft and change the relative posture between the work and the tool so that the angle between the tangent and the tool axis is the minimum angle for avoiding interference, and perform machining. I do. The A and B axis driving units 25 control the 5 axis N
The A axis and the B axis of the C machine tool 26 are rotated by a predetermined angle. Next, the control unit 21 controls the tool to move along the tool path and to continue machining.

According to the machining method of the present invention, while checking the interference between the workpiece and the tool gripping part, the relative posture of the workpiece and the tool gripping part is controlled so that they do not interfere with each other, and as much as possible. Since the outer periphery of the cutting edge farthest from the tool axis at the tip of the tool by tipping the tool comes into contact with the workpiece and machining, the machining ability of the tool is improved and continuous machining is performed.
Even if the tool length is short, interference with the workpiece can be avoided, high-precision high-speed machining can be realized, and machining with a small-diameter tool without excessively high tool rotation speed can be realized.

[0012]

FIG. 3 is an explanatory view of a 5-axis continuous machining method according to the present invention. The figure shows a tool holder 32 for holding the ball end mill 31 or a spindle 33 for holding the tool holder 32.
An example is shown in which the tool axis is rotated counterclockwise by θ ° with the center point 36 of the tool as a fulcrum in order to avoid the interference when the tool interferes with the work 34 in the interference area 35. In this case, X, while continuously performing this rotation angle control,
Since the three-axis machining of Y and Z is performed, the problem of the prior art is solved,
That is, it is possible to maintain the processing accuracy, improve the processing efficiency, and further reduce the time and labor required for setup. The same is true if the work is inclined instead of the tool.

FIG. 4 is an explanatory view of the milling roughing process. A procedure for roughing the workpiece 44 by the milling cutter 41 will be described below. This figure shows a sectional view of the work 44 and the milling cutter 41 immediately before processing. The cross section of the material shape of the work 44 is a rectangle surrounded by points L1, L2, L3, and L4, and the cross-sectional shape of the product after final processing is a shape surrounded by points L41, L42, L3, and L4. A curve between the points L42 is a curve. When performing such a process, first, a milling roughing process is performed.

It is apparent from the figure that in this rough milling, it is preferable to perform the above-described indexing three times using a 5-axis NC machine tool. After the first indexing, that is, after setting the A-axis and the B-axis at a predetermined angle, the milling roughing is performed from the linear processing between L1 and L2 to L1.
1. Straight line processing is performed several times from right to left in the figure until straight line processing between L12. Similarly, after the second indexing, the milling roughing is performed from the linear machining between L21 and L22 to L23 and L2.
The straight line machining is performed several times from the lower left to the upper right in the figure several times until the straight line machining between four. Similarly, after the third indexing, the milling roughing is performed by straight-line machining from the lower right to the upper left in the figure several times from the linear machining between L31 and L32 to the linear machining between L33 and L34.

FIG. 5 is an explanatory view of a conical interference model according to the present invention. This drawing is a cross-sectional view when a tool 51 such as a ball end mill, a tool holder 52 for holding the tool 51, and a tool gripping portion composed of a main shaft 53 for holding the tool holder 52 move on the curved surface of the work to process the work. Show. The conical interference model of the present invention is a tool which is a point which is directed from the foremost point 57 of the tool 51 having an arc-shaped cutting edge to the main axis 53 along the tool center axis by an arc radius R formed by the tool tip. The center point 56 is obtained by connecting the tool holder 52 and the outermost portions of the main shaft 53, M1 and M2 in this case. The conical shape interference model data is data representing the shape of the conical shape interference model. This data is stored in the storage unit of the control means, and the data is used for checking the interference between the workpiece and the tool gripping unit. The curve P1P2 representing one curved surface of the work is subdivided, and at each of the subdivided points, tool posture control is performed while performing an interference check.

FIG. 6 is an explanatory view of a working example according to the present invention. This figure shows the cross section when the tool gripper moves on the curved surface of the workpiece and the workpiece is machined. In the machining using a 5-axis machine tool, the workpiece shape after roughing and the conical interference model of the tool are shown. One XZ plane orthogonal to the Y axis is shown to determine the amount of rotation change around the Y axis that does not interfere. In this drawing, the workpiece shape after the roughing is shown by a solid line, the movement locus (tool path) of the tool center point during the workpiece surface processing is shown by an alternate long and short dash line, and the final machining shape of the workpiece is shown by an alternate long and two short dashes line. The tool center point of each tool during workpiece machining is A, B, C,
The shapes of the conical interference models at the positions D, E, and F are indicated by dotted lines. In addition, ball end mill 6
1 is held by a tool holder 62, and the tool holder 62 is held by a main shaft 63.

By analyzing FIG. 6, it is possible to obtain a rotation change amount around the Y-axis where the workpiece shape after the roughing and the conical interference model do not interfere as described below. While controlling the X, Y, and Z axes of the 5-axis machine tool to move the tool, A is a rotation axis around the X axis so that the conical interference model does not interfere with the workpiece shape after roughing. Continuous machining is performed by controlling the rotation of the B-axis, which is a rotation axis about the axis and the Y-axis. In the present embodiment, at the position of the tool center point during the machining of the workpiece, the posture of the tool is obtained by rotating the B axis clockwise by α around the Y axis from the tangent drawn on the tool path, that is, from the horizontal state. Interference can be avoided by setting the axis, which rotates the Z axis clockwise around the Y axis by α, as the tool axis. Similarly, the tool center point is point B, point D, point E,
The posture of the tool that avoids interference at the position of the point F can be obtained. When the tool center point is at position C, the posture of the tool is obtained by rotating the B axis clockwise by β around the Y axis from the tangent drawn on the tool path, that is, by rotating the Z axis clockwise by β around the Y axis. Interference can be avoided if the rotated axis is used as the tool axis. Although FIG. 6 shows only the amount of rotation change about the Y axis, the amount of rotation change about the X axis may be similarly analyzed on a YZ plane orthogonal to the X axis, and a description thereof will be omitted.

[0018]

As described above, according to the machining method of the present invention, the rotation angle of the A-axis and the B-axis can be adjusted along the tool moving path in the five-axis machine tool while the tool length is short. Since continuous machining can be performed while rotating to avoid interference with the system, high-speed and high-precision machining can be realized, and the outer edge of the cutting edge farthest from the tool axis at the tip of the tool by tilting the tool as far as possible The tool is capable of continuous machining by improving the machining ability of the tool by contacting with the tool.Thus, even if the tool length is short, high-precision and high-speed machining can be realized. Processing can be realized.
In addition, since the tool can be machined at the highest possible machining speed on the outer periphery of the arc cutting edge of the tool, the machining efficiency of the tool is good.

[Brief description of the drawings]

FIG. 1 is a flowchart of basic processing steps of a machining method according to the present invention.

FIG. 2 is a block diagram of control means of the present invention.

FIG. 3 is an explanatory diagram of a 5-axis continuous machining method according to the present invention.

FIG. 4 is an explanatory diagram of a milling roughing process.

FIG. 5 is an explanatory diagram of a conical interference model of the present invention.

FIG. 6 is an explanatory view of a working example according to the present invention.

FIG. 7 is an explanatory view of a conventional three-axis machining method.

FIG. 8 is an explanatory view of a conventional 5-axis machining method.

[Explanation of symbols]

 31, 61, 71, 81 ... ball end mill 32, 62, 72, 82 ... tool holder 33, 63, 73, 83 ... spindle 34, 44, 64, 74, 84 ... work 35, 75, 85 ... interference area 36, 56, 66: Tool center point 41: Milling cutter

Continuation of front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G05B 19/4093 B23Q 15/00 301

Claims (1)

(57) [Claims] At least one of three linear feed axes orthogonal to each other, X-axis, Y-axis, and Z-axis, and at least one of an A-axis rotating around the X-axis and a B-axis rotating around the Y-axis. In a machining method for machining a workpiece by using a NC machine tool having an axis and mounting a tool having an arc-shaped cutting edge at a tip on a rotary spindle of the NC machine tool, the data as data representing the shape of the workpiece to be machined is provided. A first step of storing workpiece shape data; a cone-shaped interference obtained by connecting a tool center point at a tip portion of the tool and a tool holder for holding the tool or an outermost portion of a main spindle for holding the tool holder. A second step of storing shape data of the model; and, while feeding the tool according to a tool path specified in advance, an angle between a tangent on the tool path and a tool axis is the workpiece shape data and the cone shape. A third step of calculating an interference avoidance minimum angle that is a minimum within a range in which the workpiece and the conical interference model do not interfere with each other from the shape data of the interference model; and rotating the rotary feed shaft, the tangent and the tool. And a fourth step of changing a relative posture between the workpiece and the tool so that an angle between the axis and the axis is the minimum angle for avoiding interference, and performing processing.