JPH059803B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field to Which the Invention Pertains] The present invention relates to a machine tool in which a table on which a workpiece is placed and a turret that holds a cutting tool are mutually moved to form a contour of the workpiece. This invention relates to a numerical control device that efficiently accomplishes cutting.

[Prior art and its problems]

BACKGROUND ART Today, as a machine tool controlled by a numerical control device, for example, a vertical lathe shown in FIG. 1 is in widespread use. This vertical lathe includes a rotary table RT for placing the workpiece, a tool rest TB for holding the cutting tool MT and positioning it so that it can move left and right (X-axis direction) and up and down (Z-axis direction). It is configured to automatically perform boring and turning on a workpiece placed on the rotary table RT based on a numerical control program.

However, since this type of vertical lathe performs cutting while rotating a rotary table on which a workpiece is placed, it is mainly used for surface cutting of large cylindrical bodies or conical bodies. However, as the machining accuracy of machine tools using numerical control devices has improved, there has been an increasing demand for cutting workpieces into complex shapes. For example, in the case of a workpiece that requires machining a square prism part on a part of a truncated cone, it is impossible to continuously machine the prismatic part with a conventional vertical lathe, so only the truncated cone part is cut with the vertical lathe. After that, it is necessary to change the setup of the workpiece to another lathe and then cut the rectangular face piece, which not only takes time and effort to change the setup and align, but also requires a large amount of machining time. However, there were limits to the reduction of manufacturing costs.

[Purpose of the invention]

An object of the present invention is to provide a machine tool in which a workpiece is placed on a rotary table and a cutting tool that is movable horizontally and vertically performs cutting on the workpiece. It is an object of the present invention to provide a numerical control device that can relatively move horizontally and vertically as necessary, and easily perform continuous machining of a prismatic body on a workpiece.

[Key points of the invention]

The present invention provides a machine tool equipped with a rotary table on which a workpiece made of a polygonal prismatic body is placed, and a cutting tool movable in two predetermined axes with respect to the rotary table. The cutting tool is moved parallel to the central axis C of the table in the direction of its central axis Z, and the central axis C of the rotary table is moved.
In a numerical control device configured to cut a prismatic workpiece on a rotary table by moving the cutting tool in a predetermined axis X direction perpendicular to the central axis Z of the rotary table and the central axis Z of the rotary table, The distance x from C to the center axis Z of the cutting tool, the distance R0 obtained by adding the radius R of the cutting tool to the distance r from the center axis C of the rotary table to the cutting surface of the prismatic workpiece, and the distance _R0 of the cutting tool. Due to the interrelationship between the distance z in the central axis Z direction, the cutting movement distance of the cutting tool with respect to the prismatic workpiece, and the rotation angle θ at the central axis C of the rotary table, the distance x, z and the rotation angle θ are Minute movement amount Δ that controls the servo mechanism
, Δz, Δx, and Δθ, based on the preset movement speed command F', the minute velocity F in the direction of the cutting surface L of the prismatic workpiece and the minute velocity F in the direction of the central axis Z of the cutting tool. _z is the following formula Based on the relationship, calculate the minute movement amounts Δ, Δz for each sampling period in each direction, and then calculate the amount of movement for each sampling period from each movement amount calculated by accumulating these minute movement amounts Δ, Δz for each sampling period. An arithmetic processing unit is provided that determines a control value for the servo mechanism by calculating a rotational axis command Δθ _o and a linear axis command ΔX _o to be distributed to a digital differential analyzer using a digital differential analyzer, and based on the control value calculated by the arithmetic processing unit. The present invention is characterized in that it is equipped with a servo mechanism that simultaneously controls the rotary table and the cutting tool at predetermined timing with sample values, and performs continuous plane cutting on the side surface of the prismatic workpiece.

That is, in the present invention, the rotary table on which the prismatic workpiece is mounted is rotated about its central axis C, and at the same time, the cutting tool is moved in the direction of the predetermined axis X with respect to the rotationally displaced prismatic workpiece. Accordingly, plane cutting can be easily realized on the side surface of the prismatic workpiece.

[Embodiments of the invention]

Next, an embodiment of the numerical control device according to the present invention will be described in detail by exemplifying a vertical lathe that performs continuous cutting of a prismatic body.

FIGS. 2 to 4 are explanatory diagrams showing the positional relationship between a workpiece placed on a rotary table and a cutting tool in a vertical lathe. Note that the numerical control device according to the present invention can be applied as is to a vertical lathe having the configuration shown in FIG.

In FIG. 2, reference numeral 10 indicates a rotary table, and 12 indicates a spindle attached to a tool rest. A workpiece 14 is placed on the rotary table 10 so as to be rotatable about a central axis C perpendicular to the horizontal surface of the rotary table 10 . Further, a cutting tool 16 is attached to the tip of the spindle 12 so as to be able to move up and down on an axis Z parallel to the central axis C. Workpiece 14 in the plane (X-axis direction)
The structure is arranged so that it approaches and moves away from the object. These basic configurations are exactly the same as those of conventional vertical lathes.

Therefore, in the present invention, the rotary table 10
In order to planarly cut the side surface of the workpiece 14 placed on it, the rotation center (C) of the rotary table 10 is
This is characterized in that the cutting tool 16, which is displaced on the X-axis with respect to the X-axis, is configured to be movable relative to the workpiece 14.

Therefore, in the present invention, the basic positions of the workpiece 14 and the cutting tool 16 are determined as shown in FIG.
If the positional relationship between the workpiece 14 and the cutting tool 16 is as shown in FIG. 4, the relative movement positional relationship between the workpiece 14 and the cutting tool 16 can be determined as follows.

First, the workpiece 14 and cutting tool 1 shown in FIG.
The positional relationship with 6 is defined as follows.

θ: rotation angle of the rotary table 10 (workpiece 14
(It is _{also the} rotation angle _of Distance R: Radius of rotation of the cutting tool 16: Distance of contour movement of the contact point P between the workpiece 14 and the cutting tool 16 R ₀ : R ₀ = R + r Based on the above definition, the following relational expression can be obtained from the state shown in Fig. 4. To establish.

x ² = ² +R ₀ ² R ₀ /x=cosθ or = _{R 0} tanθ .

X: Movement in the x distance direction (X-axis direction) θ: Movement in the rotation angle θ direction of the rotary table 10 Z: Movement in the Z-axis direction L: Movement in the distance direction F': Movement speed command F: Movement Travel speed F' when the minute speed Z = 0 of the speed command F' in the L direction In this case, the travel speed command F' is given in advance as a predetermined value, and the travel speed F is also given as a predetermined value, or It can be calculated in advance from the movement commands X and θ. Furthermore, if there is a movement command Z, the minute velocity Fz in the Z direction can also be determined in advance.

Based on the above definition, the following relational expression is established from the states shown in FIGS. 2 to 4.

From the above equations (1) and (2), the minute movement amounts Δ and Δz for each sampling period in the L and Z directions are:
They can be calculated in advance, and since these values are constant values, they only need to be calculated once.
Therefore, when these minute movements are accumulated for each sampling period, the following equation is obtained.

_o = _o-1 +Δ...(3) z _o =z _o-1 +Δz...(4) However, n and n-1 represent the current or previous sampling period.

The amount of movement in the L direction obtained using equations (3) and (4) above, _{o and o
-1} to find the movement amounts θ _o and θ _o-1 in the θ direction, the following equations are obtained.

θ _o =tan ^-1 _o /R ₀ ... (5) θ _{o -1} = tan ^-1 _{o -1} /R ₀ ... (6) However, R ₀ = r + R (see Figure 4).

Therefore, the rotational axis command Δθ _o to be distributed for each sampling period is expressed by the following equation in the same way as the above equations (5) and (6).

Δθ _o = θ _o −θ _o-1 = tan ^-1 _o /R ₀ −tan ^-1 _o-1 /R ₀ ...(7) Furthermore, the θ direction obtained from the above equations (5) and (6) If the moving amounts x _o and x _o-1 in the X direction are calculated using the moving amounts θ _o and θ _o-1 of , the following equations are obtained.

x _o = R ₀ /cosθ _o ...(8) x _o-1 = R ₀ /cosθ _o-1 ...(9) However, R ₀ =r+R (see Figure 4).

Therefore, from the above equations (8) and (9), the linear axis command Δx _o to be distributed for each sampling period is expressed by the following equation, similar to the above equation (7).

Δx _o = x _o −x _o-1 = R ₀ /cosθ _o −R ₀ /cosθ _o-1 ...(10) From the above calculation results, in the present invention, the above equations (1) to (10) are By performing digital differential analysis in the arithmetic processing section of the numerical control device and inputting predetermined outputs Δθ _o and Δx _o to the servo mechanism, the cutting tool is moved to one side of the workpiece 14 as shown in FIG. Route 1
8 for contour cutting.

Similarly, by inputting predetermined outputs Δθ _o , Δx _o , and Δ _z to the servo mechanism, the cutting tool is moved along the contour along the path 20 shown in FIG. 6 on one side of the workpiece 14. Can be cut.

In addition, in the above formulas (3) to (10), _o-1 , z _o-1 ,
Give positive and negative signs to θ _o-1 and x _o-1 , determine the direction of interpolation from the initial position and the reversal of the sign of _o-1 or θ _o-1 , and select either of the (±) operators. or choose one. It goes without saying that depending on how the command is given, contour cutting can also be performed continuously on the other side of the workpiece 14 along the path shown in FIG. 5. Furthermore, in a numerical control device, when executing the calculations of equations (1) to (10) above, there is a delay in the servo mechanism relative to the point at which the (±) operator is reversed. Therefore, irregular cutting as shown by the broken line in FIG. 7 may occur. Therefore, when calculating the above equations (1) to (10), (±)
By making an error determination in consideration of the delay of the servo mechanism at the time when the operator is reversed, the seventh
Irregular cutting as shown in the figure can be reduced.

〔Effect of the invention〕

As is clear from the above-mentioned embodiments, the numerical control device according to the present invention uses the above-mentioned calculation formulas [Equations (3) to (10)]
is calculated using digital differential analysis (DDA) in an arithmetic processing unit using a computer, and the servo mechanism is controlled based on the obtained data to calculate Planar contour cutting can be easily achieved on the workpiece. Note that as a control system for the servo mechanism, a sample value control method is adopted in which a speed detector and a position detector are provided and sampling is performed at a predetermined timing.

In this way, according to the numerical control device according to the present invention, a machine tool can be controlled to move a cutting tool vertically (in the Z-axis direction) and left and right (in the X-axis direction) with respect to a workpiece on a rotary table. , it is now possible to perform plane contour cutting on workpieces on a rotary table, which was previously considered difficult, and it is now possible to perform partial plane cutting on large workpieces that are subjected to boring and turning operations at the same time using the same machine tool. Since this can be achieved, machine tools can be made multifunctional and their utilization rate can be increased, and processing costs can be reduced as well as mass production of workpieces with complex shapes.

Furthermore, according to the device of the present invention, instead of data for each unit angle for a prismatic workpiece, only the data for the intersection points of the polygons (starting point, end point) is required, and intermediate paths are automatically determined within the numerical control device. Through calculation, numerical control of cutting tools can be achieved simply and easily.

Although the preferred embodiments of the present invention have been described above, it goes without saying that various design changes can be made without departing from the spirit of the present invention.

[Brief explanation of the drawing]

Fig. 1 is a perspective view showing an example of the configuration of a vertical lathe controlled by a numerical control device, and Fig. 2 shows a workpiece on a rotary table and a cutting machine controlled by a numerical control device according to the present invention. A perspective view showing the relative positional relationship with the tool, FIGS. 3 and 4 are plan explanatory views analyzing the movement state of the workpiece and cutting tool shown in FIG. 2, and FIG. 5 is a diagram according to the present invention. An explanatory diagram showing one embodiment of the case where a workpiece is cut by a numerical control device, and FIG. FIG. 7 is a diagram illustrating an irregular cutting state that can occur due to a delay in a servo mechanism when the sign of an operator in an arithmetic expression is reversed in the numerical control device according to the present invention. RT...Rotary table, MT...Cutting tool, TB
...Turret, 10... Rotary table, 12... Spindle, 14... Workpiece, 16... Cutting tool, 18... Cutting path, 20... Cutting path.

Claims (1)

[Scope of Claims] 1. A machine tool equipped with a rotary table on which a workpiece consisting of a polygonal polyhedron in cross section is placed, and a cutting tool movable in two predetermined axes with respect to the rotary table. and moving the cutting tool in the direction of the central axis Z parallel to the central axis C of the rotary table and in the direction of a predetermined axis X perpendicular to the central axis C of the rotary table and the central axis Z of the cutting tool, respectively. In a numerical control device configured to move a cutting tool to cut a prismatic workpiece on a rotary table, the distance x from the central axis C of the rotary table to the central axis Z of the cutting tool, and the distance x of the rotary table Distance R ₀ which is the sum of the radius R of the cutting tool to the distance r from the central axis C to the cutting surface of the prismatic workpiece, Distance z of the cutting tool in the direction of the central axis Z, and Cutting tool for the prismatic workpiece Due to the interrelationship between the cutting movement distance according to
, Δz, Δx, and Δθ, based on the preset movement speed command F', the minute velocity F in the direction of the cutting surface L of the prismatic workpiece and the minute velocity F in the direction of the central axis Z of the cutting tool. _z is the following formula Based on the relationship, calculate the minute movement amounts Δ, Δz for each sampling period in each direction, and then calculate the amount of movement for each sampling period from each movement amount calculated by accumulating these minute movement amounts Δ, Δz for each sampling period. An arithmetic processing unit is provided that determines a control value for the servo mechanism by calculating a rotational axis command Δθ _o and a linear axis command ΔX _o to be distributed to each other using a digital differential analyzer, and based on the control value calculated by the arithmetic processing unit. A numerical control device comprising: a servo mechanism that simultaneously controls sample values of a rotary table and a cutting tool at predetermined timing, and performs continuous plane cutting on a side surface of a prismatic workpiece.