JPH06262483A - Numerically controlled machine tool - Google Patents

Abstract

PURPOSE:To improve accuracy of machining shape by determining an interpolation point for fixing a distance between interpolation points by a machining locus indicator having a machining locus creating means, storing a depth of cut of this time spindle rotary shaft and grinding wheel, and controlling machining by a main control unit. CONSTITUTION:In a numerically controlled machine tool, a workpiece W is machined by simultaneous two-shaft control of rotation of a spindle 19 for supporting the workpiece W and cutting of a rotary edge tool, G having a cutting edge on the circumference to perform machining while rotating. Here is provided a machining locus indicator 2, and in a machining locus creating means 3 provided in this indicator, a plurality of interpolation points with a fixed interpolation space, provided on a machining locus line, which is a machining locus of the workpiece W, to give a relative moving locus of the edge tool G relating to the workpiece W, are determined. Coordinates in a system, constituted of a feed shaft of the edge tool G of the spindle 19 in these interpolation points, are calculated to be stored, and based on a result of this calculation, a rotational angle of the spindle 19 and a depth of cut of the edge tool G are controlled through a main control unit 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an NC grinder or the like, and when machining a workpiece by simultaneous two-axis control of rotation of the workpiece and cutting of a grindstone, the machining speed with respect to the machining surface of the workpiece. In particular, the present invention relates to a numerically controlled machine tool for machining with a constant machining time per unit machining length.

[0002]

2. Description of the Related Art Conventionally, when a workpiece is machined by simultaneous two-axis control of rotation of a workpiece and cutting of a grindstone, profile data for determining a rotation angle of a spindle and a cutting amount of a grindstone as shown in FIG. , And the machining was performed by controlling the rotation of the spindle and the cutting of the grindstone according to the profile data. Further, at this time, the grinding speed was controlled to be a preset grinding speed.

As a means for creating the profile data, as shown in FIG. 7, first, a grinding locus line L along which the grindstone shaft 13, which is the rotating shaft of the grindstone G when the workpiece W is machined, moves is obtained. Next, radial auxiliary lines are equally spaced from the C-axis (spindle), which is the rotation axis of the workpiece, at an interpolation pitch R0 that is empirically determined in advance in consideration of the accuracy of the workpiece W and grinding resistance. And the intersections with the grinding locus line L are determined as interpolation points (N1 to N5 in FIG. 7). Then, the rotation angle (interpolation pitch R0) of the C-axis (main axis) and the amount of cutting (X-axis) of the grindstone (D1 to D4 in FIG. 7) at this time were used as profile data.

[0004]

When the workpiece W is machined in the grinding process, it is considered preferable to make the grinding efficiency defined by the grinding amount per unit time uniform so as not to change the grinding resistance. ing. That is, assuming that the grinding allowance is constant, it is ideal that the grinding speed be constant.

However, in the prior art interpolation point determining means, when grinding a planar working surface P or the like as shown in FIG. 7, the interpolation pitch R0 in the rotation of the C axis is kept constant and the interpolation points N1 to N1. When N5 is determined, a difference occurs in the distances (intervals N1-N2, N2-N3, N3-N4) between the interpolation points determined on the grinding locus line L. N
In the C grinder, the grinding speed for grinding between the interpolation points (section N1-N2, section N2-N3, section N3-N4) (specifically, the relative grinding speed between the rotation of the workpiece and the cutting of the grindstone). Can be controlled to be constant. But N
Due to the calculation processing time of the C control device and the tracking delay in feedback control, etc., each interpolation point N1, N is actually
At 2, N3, N4 and N5, a very short time stop occurs. Then, even when the distances on the same grinding locus line L are the same, if the number of interpolation points is different, the number of the minute times is changed, resulting in the actual grinding time, that is, the grinding speed. Difference will occur. Then, the grinding resistance changes due to the change in the grinding speed, and problems such as the generation of a non-uniform ground surface of the workpiece W and the generation of a defective shape occur.

Therefore, an object of the present invention is to provide a numerically controlled machine tool that solves the above-mentioned problems by performing machining on a machined surface of a workpiece at a uniform machining speed.

[0007]

In order to solve the above-mentioned problems, as shown in FIG. 1, there exists a cutting tool G for a workpiece W which exists on a machining trajectory line which is a machining trajectory of the workpiece W.
Has a machining locus creating means 1 for determining a plurality of interpolation points having a constant interpolation interval that gives a relative movement locus, and coordinates in the system constituted by the spindle 19 and the feed axis of the rotary cutting tool G at the interpolation points. Machining path instruction device 2 for calculating and storing
And a main controller 3 for controlling the rotation angle of the main shaft 19 and the cutting amount of the rotary cutting tool G based on the coordinates of the interpolation points of the machining trajectory instruction device 2.

[0008]

The machining locus instructing device 2 having the machining locus creating means 1 determines an interpolation point that makes the distance between the interpolation points constant, and the rotation angle of the spindle 19 and the cutting amount of the grindstone G at this time are stored. It Then, the main control device 3 drives the numerically controlled machine tool in accordance with the rotation amount of the main spindle 19 and the cutting amount of the grindstone G given by the processing trajectory instruction device 2 to process the workpiece.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A specific embodiment of the present invention will be described below with reference to the drawings. FIG. 2 is an overall configuration diagram of an NC grinder having the present invention. In the grinding machine 10, 11 is a bed, and the bed 11 is provided with a grindstone base 12 and a table 16. The whetstone base 12 is adapted to reciprocate in the X-axis direction (vertical direction in the drawing) via the feed screw mechanism by the X-axis feed screw 15 by the drive of the X-axis drive servomotor 14 provided in the bed 11. There is. A grindstone shaft 13 that is rotated by a grindstone rotation motor (not shown) is attached to the grindstone base 12 in the Z-axis direction, and a grindstone G is replaceably fixed to the grindstone shaft 13.

The table 16 is reciprocally moved in the Z-axis direction (left-right direction in the drawing) by a Z-axis driving servomotor 22 provided on the bed 11 via a feed screw mechanism by a Z-axis feed screw 23. Has become. Table 16
A tailstock 17 and a headstock 18 are provided on the top, and a workpiece W is detachably held between them. Headstock 18
Is provided with a spindle 19 that is rotated by the drive of the C-axis driving servomotor 20, and a drive fitting 20 that transmits a rotational force from the spindle 19 to the workpiece W. The C-axis driving servomotor 20 has a spindle. An encoder 21 for detecting the rotation amount of 18 (C axis) is attached.

Reference numeral 30 is a numerical control (NC) device, and the numerical control device 30 is provided with a CPU 31a, an interface 31, and a memory 32. An X-axis driving device 33, a Z-axis driving device 34, and a C-axis driving device 35 are connected to the interface 31, respectively, so that the X-axis, Z-axis, and C-axis driving servomotors 14,
The control unit 20 and 22 are controlled respectively. Further, the detection value of the encoder 21 is input to the interface 31. And the spindle 19 (C
(Axis) rotation feed of grindstone G (X axis)
Simultaneous two-axis control for controlling quantity is possible. Further, a keyboard 36 which is an input device is connected to the interface 31.

The memory 32 has an NC operation program 32a for performing the above-mentioned simultaneous two-axis control, a profile data creating program 32b for creating profile data, and profile data 32c created by the profile data creating program 32b. Remembered The machining locus instructing device 2 and the main control device 3 having the machining locus creating means 1 in the claims are mainly realized by a computer system of the numerical control device 30.

Next, the profile data creation program will be described. FIG. 3 is a flow chart showing a flow up to the creation of the profile data 32c, and FIG. 4 shows a relative grinding locus of the grindstone G when the workpiece W is fixed when the flat surface portion of the workpiece W is ground. It is the figure shown. First, in step 200, a machining shape parameter of the workpiece W and a grindstone diameter r of the grindstone G described later are input. The machining shape parameter is a parameter that determines the machining shape of the workpiece W in the coordinate system (x-y) when the workpiece W is fixed, and includes the inclination φ of the machining surface P and the grinding start point S in FIG. The coordinates and the coordinates of the grinding end point E are meant.

In step 201, the equation of the grinding locus line L, which is the locus of movement of the grindstone shaft 13 from the machining shape parameter and the grindstone diameter r, and the grindstone shaft 1 at the grinding start point S.
The coordinates of the starting point s of 3 and the grinding wheel axis 13 at the grinding end point E
The coordinates of the end point e of are calculated. Here, the starting point s of the grindstone shaft 13 at the grinding start point S is the position where the perpendicular line extending from the grinding start point S of the machined surface P intersects the grinding locus line L, and the end point e of the grinding wheel shaft 13 at the grinding end point E. Is a position where a perpendicular line extending from the grinding end point E of the processed surface P intersects the grinding locus line L.

At step 202, the interpolation interval K, which is the interval between the interpolation points determined on the grinding locus line L, is input from the keyboard 36. It should be noted that the value of the interpolation interval K to be input is a value that is empirically obtained depending on the machining accuracy of the workpiece W and the like. In step 203,
The machining locus line L is divided from the start point s to the end point e at the interpolation interval K to determine the interpolation points M2 and M3, and the interpolation points M2 and M
Calculate the coordinates of 3. However, the start point s is the interpolation point M1 and the end point e is the interpolation point M4. Further, the interval between the interpolation point immediately before the end point e (the interpolation point M3 in FIG. 4) and the end point e is not necessarily the interpolation interval K because of the length of the interpolation interval K.
It may not be.

At step 204, each interpolation point M1, M
The coordinates at 2, M3 and M4 are the rotation angles of the main shaft (R1, R2 and R3 in FIG. 4) and the cut amount of the grindstone G (H1 in FIG. 4).
H2, H3) to create the profile data 32c shown in FIG. 5 and terminate the profile data creation program 32b. In step 202 described above, the interpolation interval K is manually input with an empirical value obtained in advance, but it can be automatically determined by using the following means. That is, a decision table as shown in FIG.
To remember. The decision table is a crossing angle range that determines a range of a crossing angle (see an angle U in FIG. 4) that is an angle when the grinding locus line L and the auxiliary line extended from the C axis intersect and the crossing angle. The interpolation distance used within the range is determined, and each value is set by a value obtained empirically.

First, from the start point s to the end point e on the grinding locus line L.
The minimum crossing angle that is the smallest value among the crossing angles that can be taken between is calculated. In this embodiment, the intersection angle (angle U in FIG. 4) at the starting point s is the minimum intersection angle. Then, the interpolation distance for the minimum intersection angle is obtained from the decision table stored in the memory 32, and this value is determined as the interpolation interval K. If the above-mentioned means is added to the profile creation program 32b, the interpolation interval K can be automatically set.

Next, the operation of the NC grinder having the above-mentioned structure will be described. It is assumed that the following rotation of the main shaft 19 and driving of the cutting of the grindstone G are performed according to the profile data 32c described above. Further, although the profile data 32c of this embodiment does not include data relating to the drive of the table 16 in the Z-axis direction, in reality
It shall also have axial data.

First, the Z-axis driving servomotor 22 is driven to move the table 16 in the Z-axis direction so that the grindstone G faces the surface of the workpiece W to be machined. Subsequently, the workpiece is rotated about the C axis by driving the X-axis driving servomotor 14, and the grindstone G is rotated by driving the grindstone rotating motor (not shown), while the X-axis driving servomotor 14 is rotated. By driving, the grindstone base 12 and the grindstone G are moved in the X-axis direction orthogonal to the C-axis, and the grindstone G is moved so as to move on the grinding locus line L relative to the workpiece W.
At this time, the grinding speed (specifically, the relative speed between the workpiece W and the grindstone G) moves at a preset speed F.

In the actual grinding process, as described in the prior art, between the interpolation points (section M1-M2, section M2-).
Although it is possible to perform the grinding movement in M3, the section M4 to M5) at the speed F, the interpolation points M1, M2, M3 and M4 are actually set due to the calculation processing time of the NC controller and the tracking delay in the feedback control. At, a minute time stop occurs. However, the profile data 3 of this embodiment
2c is set so that the intervals of the respective interpolation points are equal to each other at the interpolation interval K, so that the minute time generated per unit length is constant, and a uniform time on the same grinding locus line L, That is, grinding is performed at a uniform grinding speed.

As described above, in this embodiment,
Since the profile data 32c in which the interpolation pitch K which is the distance between the interpolation points is equalized can be created by changing the interpolation pitch of the C axis, it is possible to perform grinding at a uniform grinding speed with respect to the ground surface of the workpiece. Is constant, and therefore, the deformation amounts of the workpiece W and the grindstone G due to the grinding resistance are made uniform, and the shape accuracy of the workpiece is improved. Further, since the interpolation points are made uniform with respect to the processing surface P, there is also an advantage that the delay of the grinding processing time which is caused by the overcrowding of the interpolation points can be eliminated.

In this embodiment, the profile data 32c for forming a flat surface on the workpiece W has been described. However, profile data can be similarly created for a curved surface described later. That is, in order to keep the interpolation interval K constant, it is necessary to be able to calculate the length on the grinding locus line L, that is, the grinding locus line L needs to be mathematically expressed. The grinding locus line L can be calculated as an envelope curve when a circle having a diameter r (grinding stone diameter) moves on the machining surface P. Therefore, for the curved surface where the machining surface P is given by a function, the profile similar to that of this embodiment is used. The data 32c can be created. The method of calculating the envelope described above is mathematically established, and therefore its description is omitted. Incidentally, the envelope of a circle moving on a certain straight line as in this embodiment is a straight line.

[0023]

As described above, according to the present invention, a machining locus that makes the distance between interpolation points constant is created, and machining is performed according to this machining locus, so that the machining surface of the workpiece is machined uniformly. Can be processed at speed. As a result, the machining efficiency becomes constant, the deformation amounts of the workpiece and the cutting tool due to the resistance caused by machining are made uniform, and the shape accuracy of the workpiece is improved. Further, there is an advantage that the distance between the interpolation points becomes constant and the processing time delay caused by the congestion of the interpolation point distance can be eliminated.

[Brief description of drawings]

FIG. 1 is a diagram corresponding to a claim of the present invention.

FIG. 2 is an overall configuration diagram of an NC grinding machine according to this embodiment.

FIG. 3 is a flow chart showing a profile creating procedure of the present embodiment.

FIG. 4 is a diagram showing interpolation points in the present embodiment.

FIG. 5 is a diagram showing profile data of this example.

FIG. 6 is a diagram showing a decision table of this embodiment.

FIG. 7 is a diagram showing interpolation points in the conventional technique.

FIG. 8 is a diagram showing profile data of a conventional technique.

[Explanation of symbols]

 10 Grinding machine 11 Bed 14 X-axis drive servo motor 20 C-axis drive servo motor 30 Numerical control device G Grindstone W Workpiece P Machining surface L Grinding trajectory line

Claims (1)

[Claims] 1. Rotation of a spindle for supporting and driving a workpiece,
In a numerically controlled machine tool for machining the workpiece by simultaneous two-axis control with a cutting of a rotary blade having a cutting edge on the circumference and performing processing while rotating, it is a machining trajectory of the rotary blade for the workpiece. There is a machining locus creating means that exists on a machining locus line and determines a plurality of interpolation points with a constant interpolation interval that gives a relative movement locus of the rotary cutting tool with respect to the workpiece, and the main axis and the main axis at the interpolation point. A machining trajectory indicating device that calculates and stores coordinates in a system constituted by the feed axis of the rotary blade, and based on the coordinates of the interpolation points of the machining trajectory indicating device, the rotation angle of the spindle and the cut of the rotary blade. A numerically controlled machine tool having a main controller for controlling the quantity.