JP2750959B2 - NC non-circular processing machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an NC non-circular processing machine for processing a non-circular shape by turning or grinding.

[0002]

2. Description of the Related Art Conventionally, in order to process a workpiece having a non-circular cross-section such as an elliptical piston or a camshaft at high speed and with high efficiency, a non-circular processing machine generally using a cam copying method or an NC method, for example, a piston processing lathe. , Cam grinders and the like are used.

[0003]

As described above, in a non-circular processing machine, a tool is made to follow the rotation of a cam integrated with a workpiece,
Processing is performed by synchronizing with NC and swinging so as to follow a non-circular shape. For this reason, when the rotation speed of the workpiece is increased, the inertia force of the movable portion increases, the reaction force at the time of reversal increases, and the machine vibrates to increase the machining shape error. Therefore, the weight of the movable part is reduced to reduce the reaction force in order to reduce the error. In order to reduce the acceleration at the time of reversing, control is performed so that the rotational speed of the workpiece becomes unequal. Before machining the product, trial cutting is performed, the shape error of the workpiece is measured, and the master cam and profile data are corrected. However, there has been a problem that the desired high speed and high accuracy cannot be achieved economically, and the demands of users have not been satisfied.

[0006] As a result of pursuing the cause of error generation in various studies, when machining a non-circular shape, as shown in FIG. 6, the actual tool trajectory xa (θ) is changed to the command shape xc as shown in FIG.
An error δ (θ) due to bending and vibration of the machine is added to (θ), and xa (θ) = xc (θ) + δ (θ). Here, if a shape obtained by subtracting the error δ (θ) from the target shape xo (θ) as a correction value, that is, xc (θ) = xo (θ) -δ (θ) is specified, the actual tool path xa (θ) Is xa (θ) = xc (θ) + δ (θ) = (xo (θ) −δ (θ)) + δ (θ) = xo (θ), and machining according to the target shape is possible. This indicates that highly accurate non-circular processing can be performed by accurately detecting and correcting the error δ (θ).

The trajectory xa (θ) of the tool during machining of a non-circular shape
Includes an error δ (θ), so that xa (θ) = xo (θ) + δ (θ)... At this time, the moving acceleration αa (θ) of the tool is given by the following equation: θ = ωt ω: rotational angular velocity of the work (rad / s)
ec) t: time (sec), and when differentiated twice at time t, αa (θ) = ω ² {(d ² xo (θ) / dθ ² ) + (d ² δ (θ) / dθ ² )} ............ Here, ω ² · {d ² xo (θ) / dθ ² } is a theoretical acceleration when the tool moves with an error = 0.

If αo (θ) = ω ² · {d ² xo (θ) / dθ ² }, the equation is αa (θ) = αo (θ) + ω ² · (d ² δ (θ) / dθ ² ) d ² δ (θ) / dθ ² = ω ⁻² {αa (θ) −αo (θ)}... Therefore, the error δ (θ) is obtained by integrating the expression twice at time t, and δ (θ) = ω ⁻² ∬ ｛αa (θ) -αo (θ)｝ dt... The error δ (θ) can be calculated by calculating αo (θ) from the target shape and detecting the actual acceleration αa (θ) during the movement of the tool by the acceleration sensor. By using this value as a correction value, it has been conceived that highly accurate non-circular shape processing can be performed.

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above-mentioned problems of the prior art, and has as its object to provide an NC non-circular shape which is economically and sufficiently satisfactory in high-speed and high-precision non-circular processing. It is intended to provide a processing machine.

[0008]

SUMMARY OF THE INVENTION In order to achieve the above-mentioned object, the present invention comprises rotating a workpiece mounted on a main shaft ,
In NC processing machine for processing a non-circular shape by reciprocating the cutting direction in synchronism with the tool to the spindle rotation, before
The angle detector of the spindle and the acceleration in the cutting direction of the tool
An acceleration sensor for detecting an inertial force, a calculating means for calculating a cutting error component based on actual acceleration data corresponding to the number of divisions of the spindle angle detected by the acceleration sensor, and a target for calculating the calculated error component as a shape correction value And calculating means for calculating command value data from the shape data, and drives the tool with the command value data.

[0009]

The acceleration sensor 22 provided on the tool post 20 on the sub-horizontal feed stage obtains N pieces of actual acceleration data of the main shaft angle division number, and the shape correction is carried out based on the data αai, the main shaft rotation speed n, and the main shaft angle division number N. The value data Xhi is determined, and the tool is driven by the command value data Xci determined based on the value to process the non-circular shape.

[0010]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of a lathe according to an embodiment. In a known lathe, a headstock 1 is fixedly mounted on a bed (not shown), and a spindle 3 having a chuck 2 fitted at the tip is rotatably supported by a bearing. A pulley at a rear end is an output shaft of a spindle drive motor 4. Are rotationally connected by a pulley and a belt. On the bed, a tailstock 5 that can move and position in opposition to the main shaft 3 is placed, and a workpiece W is supported at the center of the tailstock 6.

Further, a carriage 9 is movably mounted on a horizontal guide surface 8 parallel to the main shaft on the bed, and a nut is screwed into a feed screw 10 supported on the bed to rotate the servo motor 11. Is used to control the movement and positioning. On the carriage 9, the main traverse 1 on the guide surface in the X-axis direction
2 is mounted and the nut 1 is mounted on the carriage 9 and the feed screw 1
3, and the movement position is controlled by the rotation of the servomotor 14.

Further, on the main traverse 12, a sub traverse 16 is mounted on a guide surface in the X-axis direction, and a nut is screwed with a feed screw 17 mounted on the main traverse 12. Movement and positioning control is performed by rotation of the servo motor 18 provided with the position detector 23 (hereinafter, a drive shaft for this control is referred to as a cam shaft). The turret 1
A turret tool rest 20 having a turret 9 is provided. A signal generator such as an optical or magnetic angle detector or pulse generator 21 is provided on the headstock 1 or the spindle 3. In addition, the turret tool post 20 has inertia
An acceleration sensor 22 for detecting by force is attached.

The NC device 30 has at least the following configuration. The non-volatile bubble memory 31 stores data created by a shape data creating device such as a personal computer, data read from a floppy disk 41 by a floppy drive 42, or various data read from a tape 43 by a tape reader 44. Is stored.

The main processor 32 is provided with a CPU 321 for controlling the entire machine and a RAM 322 for various data. The RAM 322 includes the following. In FIG. 2, a spindle speed data area 322a for storing a spindle speed n when machining a workpiece, and a spindle angle division number data area 322 for storing a spindle angle division number N.
b, a target shape data area 322c for storing target shape data Xoi representing the cross-sectional shape of the workpiece in a polar coordinate system, the target shape data, the spindle rotation speed during machining, and the theoretical speed data Voi calculated based on the spindle angle division number. Theoretical speed data area 322d for storing

A theoretical acceleration data area 322e for storing theoretical acceleration data α ₀ i calculated based on theoretical speed data, spindle rotation speed, and spindle axis division number, and actual acceleration data for storing actual acceleration data αai detected by the acceleration sensor 22. An area 322f, an actual speed data area 322g for storing actual speed data Vai calculated from the actual acceleration data, the spindle speed, and the spindle angle division number;

A shape correction value data area 322h for storing shape correction value data Xhi for correcting an error such as machine vibration caused by swinging of the cam shaft, a target shape data, and a shape correction value data. A command value data area 322j for storing command value data Xci to be used and a temporary data area 322k for temporarily storing data in the process of calculating the shape correction value data Xhi are provided.

The cam shaft control processor 33 for controlling the cam shaft with high speed and high accuracy includes the following. In FIG. 2, the timing of outputting command value data, the correction value data of control delay, the position signal from the camshaft position detector 23, and the timing of taking actual acceleration data from the acceleration sensor 22 by the signal of the pulse generator 21 attached to the main shaft. Access controller 3 that controls
31,

Command value data RAM 33 for storing command value data Xci transferred from main processor 32
2. RAM 333 for control delay correction value data for correcting the control delay of the cam shaft servo system for driving the cam shaft according to the command value, repetitive control which is the control method of the conventional control for the control delay correction value data A deviation value data RAM 334 for temporarily storing the deviation value data to obtain
Note that the RAM for deviation value data is not always necessary when calculating control delay data by calculation or the like.

A RAM 335 for actual acceleration data for temporarily storing actual acceleration data αai detected from the acceleration sensor 22 provided near the tool, and a cam shaft position detector 23
Adder / subtractor 34 for adding / subtracting the detected value of the above and the storage value of the command value data RAM, and an adder 3 for adding the output of the adder / subtractor 34 to the data of the control delay data 333.
5. An arithmetic unit 39 for obtaining control delay correction value data from the deviation value data is provided. 36 and 37 are motor driving devices, 38 is an interface, and 39 is an A / D converter.

The procedure for creating the shape correction data and the command value data in the above configuration will be described with reference to FIGS. First, command value data is obtained based on FIG. In step S <b> 1, the main shaft angle division number N is read from the bubble memory 31 into the main shaft angle division number data area 322 b in the RAM 322.

In step S 2, the target shape data Xoi read from the floppy disk 41 or the tape 43 and stored in the bubble memory 31 is stored in the main processor 3.
2 is read into the target shape data area 322c in the RAM 322 at the clock timing. When Δθ = 2π / N, Xoi = Xo (Δθxi), where i = ₁ , ₂ , _3, ... _N. Similarly, in step S3, the spindle speed n is changed from the bubble memory 31 to the spindle speed data area 32 in the RAM 322.
2a is similarly read.

In step S4, target shape data Xo
i is stored as a command value Xci in the command value data RAM 332 in the cam shaft control processor 33. Here, i is i = ₁ , ₂ , _3, ..., _N and the number of main shaft angle divisions, and the same applies hereinafter. That is, N numbers are stored.

In step S5, the cam shaft position detector 2
3 and the command value data X stored in the RAM 332
Ci is output to the driving device 37 through the adders / subtractors 34 and 35, and the servo motor 18 is rotated to drive the cam shaft of the feed screw 17. At this time, a control delay correction value is obtained by repetitive control or the like, and control and drive are performed so that control delay does not occur. When the main shaft 3 is rotated at the main shaft rotation speed n at a timing regulated by the access controller 311 based on the signal of the pulse generator 21 from the acceleration sensor 22 in a state where the control is not delayed, and the cam shaft is driven to follow the rotation. The actual acceleration αai of the tool rest 20 is calculated as RA for acceleration data.
Read in M335.

In step S6, the actual acceleration αai is stored in the RAM 322 in the main processor at the clock timing from the RAM 335 for acceleration data in the cam shaft control processor.
To the actual acceleration data area 322f. Step S
At 7, the calculation of the shape correction value data Xhi is performed.
This calculation is shown in the flowcharts of FIGS. 4 and 5, and calculates shape correction value data.

In step S71, Xo ₁ and Xo read into the target shape data area 322c, the spindle speed data area 322a, and the spindle angle division number data area 322b.
Based on o _N , n, N, the CPU 321 performs an operation of (Xo ₁ −Xo _N ) × n × N / 60 when i = ₁ to obtain theoretical speed data Vo ₁ and (i = ₂ , ₃ ,... _N Regarding), the calculation of {Xoi− (Xoi− ₁ ) × n × N} / 60 is performed to obtain the theoretical speed data Voi, which is similarly stored in the theoretical speed data area 322d.

In step S72, step S71
Data Vo ₁ stored in the theoretical velocity data area 322d obtained in, ...... Vo _N and regions 322a and 3
Based on the spindle speed n and spindle angle division number N stored in 22b, when i = ₁ (Vo ₁ −Vo _N ) × n × N / 6
0 to calculate the theoretical acceleration data αo ₁ and (i = ₂ ,
₃ ,... _N ) ｛Voi− (Xoi− ₁ ) × nx
N｝ / 60 is calculated and the theoretical acceleration data αoi is similarly stored.

In step S73, the theoretical acceleration data αoi and the spindle speed n stored in the theoretical acceleration data area 322e, the spindle speed data area 322a, the spindle angle division number data area 322b, and the actual acceleration data area 322f of the RAM 322. , The main shaft angle division number N, and based on the actual acceleration αai, when i = ₁ (αa ₁ −αa _N ) ×
60 / (n × N) is calculated by the CPU 321 to obtain V′a ₁ . And (for i = ₂ , ₃ ,... _N ) (a) Equation {(αai−αoi) × 60 / (n × N)} + V′ai
₋₁ , and further (for i = ₁ , ₂ ,..., _N ) (b) The operation of Expression 1 is performed by the CPU 321 to determine the actual speed Vai, and the actual speed Vai is similarly calculated in the actual speed data area 322 g in the RAM 322. It is memorized.

(Equation 1)

In step S74, the spindle speed n, the spindle angle division number N, and the actual speed Va stored in the actual speed area.
Based on i, when i = ₁ , Va ₁ × 60 / (n × N) is calculated by the CPU 321 to obtain X′hi. And (i =
₂ , ₃ ,..., _N ) (c) Equation Vai × 60 /
(N × N) + X′hi− ₁ is calculated and X′hi is calculated as C
Determined in PU321. Note that (i = ₁ , ₂ ,
... ( _N ) (d) Expression 2 is calculated by the CPU 321.
The shape correction value data Xhi is obtained and stored in the shape correction value data area 322h of the RAM 322. Then, the calculation of the shape correction value data ends.

(Equation 2)

(Note) Equations (a) and (b) are for obtaining Vai. When the equation (a) is written as a general equation, Va (t) = {αa (t) −αo (t)} dt, but this equation alone does not determine the integration constant and Va (t)
Is not found. Equation (2) seeks to obtain Va (t) based on the condition that the moving distance in one revolution of the spindle = 0.

(Equation 3) In order to satisfy this equation, Vai is tentatively calculated by equation (a), and is calculated by equation (2) so that equation 4 is obtained.

(Equation 4) The same applies to (c) and (d).

When the shape correction value data Xhi is calculated as described above, the flow shifts to step S5, where the main processor 32
CPU 321 based on shape correction value data Xhi stored in shape correction value data area 322h in RAM 322 of FIG.
In step (3), the target shape data Xoi-Xhi is calculated to obtain command value data Xci, which is stored in the command value data area 322j of the RAM 322.

When the command value data taking into account the shape correction value is obtained as described above, NC sets the Z-axis servo motor 1
1, X-axis servomotor 14, camshaft servomotor 18
, And the workpiece W is rotated together with the main shaft 3 to cut the cam by the screw shaft control of the tool 19.

[0032]

As described above, the present invention has the following effects. An acceleration sensor was attached to the tool post, the cutting error was calculated based on this data, and the NC control was performed using the command value data that takes into account the error correction value.
Acceleration sensors can detect errors caused by vibrations that are not detected by the camshaft control position detector attached to the camshaft, and can correct the errors, enabling high-speed, high-precision machining of non-circular shapes. It became.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a control block diagram in an NC non-circular processing machine of the present invention.

FIG. 2 is a block diagram of a control device.

FIG. 3 is a flowchart for calculating shape correction value data;

FIG. 4 is a flowchart for obtaining command value data.

FIG. 5 is a flowchart following FIG. 4;

FIG. 6 is a diagram illustrating a tool trajectory and a command shape error during non-circular machining.

[Explanation of symbols]

 Reference Signs List 2 chuck 3 main shaft 9 carriage 12 main traverse 14, 18 servo motor 16 sub traverse 17 feed screw 21 pulse generator 22 acceleration sensor 23 position detector 30 controller 31 bubble memory 32 main processor 33 cam shaft control processor 321 CPU 322 RAM 331 Access controller 332 RAM for command value data 333 RAM for control delay correction value data 334 RAM for deviation value data 335 RAM for acceleration data

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G05B 19/404 B23Q 15/013

Claims (1)

(57) [Claims] 1. A workpiece mounted on a spindle is rotated,
In NC processing machine for processing a non-circular shape by reciprocating the cutting direction in synchronism with the tool to the spindle rotation, before
The angle detector of the spindle and the acceleration in the cutting direction of the tool
An acceleration sensor for detecting an inertial force, a calculating means for calculating a cutting error component based on actual acceleration data corresponding to the number of divisions of the spindle angle detected by the acceleration sensor, and a target for calculating the calculated error component as a shape correction value An NC means for calculating command value data from the shape data, wherein the tool is driven by the command value data.