JPH0319751A - Thermal displacement correcting device in lathe - Google Patents

Abstract

PURPOSE:To perform machining of very high accuracy by providing constitution in such a way as detecting the thermal displacement between a tool rest and a headstock and an angle error and correcting a moving target value of the tool rest based on this detection. CONSTITUTION:The thermal displacement between a headstock and a tool rest is detected by thermal displacement detecting means 14, 15. Further an angle error of the tool rest for a spindle is detected by an angle error detecting means 34. Being based on these detection results, a moving target value of the tool rest is corrected by a correcting part 40. In this way, since the thermal displacement between the headstock and the tool rest and the angle error of the tool rest are actually measured and corrected for the moving target value, a deviation by the thermal displacement can be corrected with very high accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a thermal displacement correction device for a lathe in which a headstock supporting a main shaft and a tool rest are arranged side by side.

[Conventional technology]

In machine tools such as lathes, various parts undergo thermal displacement due to heat during workpiece machining. In particular, the space between the spindle portion on which the workpiece is mounted and the tool stand on which the tool is mounted is susceptible to thermal displacement. Therefore, when it is necessary to perform high-precision machining, heat countermeasures are important.

Therefore, some conventional lathes and the like are provided in which, for example, the headstock is cooled to suppress thermal displacement. It has also been considered to detect the temperature of the machining part, etc., and correct the machining target value data in accordance with this temperature.

[Problem to be solved by the invention]

In conventional systems that cool head stocks, for example, the cooling structure becomes complicated, resulting in an increase in the size of the entire device. Further, in those that perform correction by temperature detection, it is not possible to accurately correct thermal displacement, and it is difficult to perform highly accurate processing. In particular, when high-speed and high-precision machining is required, as is the case these days, the above-mentioned conventional methods cannot adequately handle the situation.

An object of the present invention is to provide a thermal displacement correction device for a lathe, which can correct thermal displacement in a lathe and perform highly accurate machining.

[Means to solve the problem]

The thermal displacement correction device for a lathe according to the present invention is applied to a lathe in which a movable tool stand is arranged in parallel to a headstock that supports a main spindle. The apparatus includes a thermal displacement amount detection means for detecting the amount of thermal displacement between the headstock and the tool rest, an angular error detection means for detecting an angular error of the tool rest with respect to the spindle, and a correction means.

The correction means corrects the movement target value of the tool stand based on the detection results of the thermal displacement amount detection means and the angular error detection means.

[Effect]

When considering thermal displacement in a lathe, what greatly affects machining accuracy is the thermal displacement of the distance between the headstock that supports the spindle and the tool stand, that is, the distance in the radial direction of the workpiece. Thermal displacement also causes an angular error with respect to the main axis of the tool stand, and this angular error also appears as a displacement of the distance in the radial direction.

Therefore, in the present invention, the amount of thermal displacement between the headstock and the tool stand is detected by the thermal displacement amount detection means, and
The angular error detection means detects the angular error of the tool stand with respect to the spindle. Then, based on each of these detection results,
Correct the movement target value of the tool stand.

In this way, the amount of thermal displacement between the headstock and the tool rest and the angular error of the tool rest are actually measured and corrected against the movement target value, making it possible to correct deviations due to thermal displacement with extremely high accuracy. I can do it.

〔Example〕

FIG. 2 is an overall perspective view of a turret lathe to which a thermal displacement correction device according to an embodiment of the present invention is applied.

In this talent lathe 1, a main shaft 2 and a tool stand 7 including a turret 3 and the like are arranged side by side in the horizontal direction.

The tool stand 7 is movable in the longitudinal and lateral directions of the apparatus. Further, a tail stock 4 that supports the center of the tip of the workpiece is movably arranged opposite to the main shaft 2. A control section 6 in which a CRT and various operation keys are arranged is provided on the upper part of the main body frame 5.

FIG. 3 is a plan view showing details of the main spindle 2 and the tool rest 7. As shown in FIG. As shown in this figure, a spindle chuck 10 for gripping a workpiece W is fixed to the tip of the spindle 2. As shown in FIG. The main shaft 2 is connected to the headstock ■3 via bearings 11 and 12.
is rotatably supported. First and second touch sensors 14 and 15 are attached to the front end (right side in the figure) and rear end (left side in the figure) of the lower part of the side wall of the hemlock stock 13 on the tool stand 7 side.

The tool stand 7 is movable in the X direction and the Z direction orthogonal thereto with respect to the head 16 of the apparatus main body.

Rails 17 and 18 are arranged on the upper surface of the bed 16 in the X direction, and a cross slide 19 is movable in the X direction along the rails I7 and 1. Also,
Rails 20 and 21 are arranged on the upper surface of the cross slide 19 in the Z direction, and the index house 22 is movable in the Z direction along the rails 20 and 2l. Note that four linear guides 24 to 27 are attached to the lower surface of the index house 22, so that the linear guides 24 and 26 slide on the rail 20, and the linear guides 25 and 27 slide on the rail 21. ing.

The index house 22 is for rotatably supporting the talent shaft 23 and for positioning the rotation angle. A turret 3 around which a tool 8 is attached is fixed to the tip of the turret shaft 23.

The cross slide 19 is driven by a ball screw 29 arranged in the X direction, and the ball screw 29 is rotated by a servo motor 28 with an encoder.

Further, the cross slide 19 is equipped with a servo motor (not shown) equipped with a Yuncoder, and a ball screw 30 for driving the index house 22 is connected to this servo motor.

FIG. 1 is a control block diagram of a thermal displacement correction device according to an embodiment of the present invention. The control unit 5 6 shown in FIG. 2 includes a thermal displacement correction unit 31 .

The thermal displacement correction section 31 is connected to the first and second touch sensors 14 and 15 shown in FIG.
4 outputs are connected.

In addition, this thermal displacement correction section 31 receives the output of a temperature sensor 32 consisting of a thermal sensor placed near the force U machining section, and the output of a target value input section 33 for inputting a target value for machining. is connected. Further, the output of the thermal displacement correction section 31 is connected to a tool section drive system 35 constituted by the servo motor 28 shown in FIG. 3 and the like.

The thermal displacement correction section 31 determines the main shaft 2 based on the outputs of the first and second toughness sensors 14 and 15 and the output of the encoder 34.
and a tool part thermal displacement calculating section 37 that calculates the amount of thermal displacement and angular error between the tool table 7 and the workpiece 7, and a tool part thermal displacement calculating section 37 that calculates the amount of thermal displacement and angular error between the workpiece and the tool stand 7, and a workpiece that similarly detects the amount of thermal displacement from the output of the temperature sensor 32. A tool part thermal displacement amount detection section 36, an addition section 39 that adds each thermal displacement amount, and a correction section 40 that corrects the target value data from the target value input section 33 using the addition result of the addition section 39. The tool section movement control section 41 outputs data for controlling the tool section drive system 35 based on the output of the correction section 40. Note that the thermal displacement correction section 31 is composed of a CPU, ROM, RAM, etc.

Next, the operation of thermal displacement correction will be explained.

First, the turret lathe 1 shown in FIGS. 2 and 3 will be modeled as shown in FIG. 4.

In FIG. 4, the same reference numerals as in FIGS. 2 and 3 indicate the same parts. P, is the workpiece machining point which is the target coordinate,
P2 is a tool machining point (tool cutting edge point) which is an actual machining coordinate. In addition, N is a reference point when considering thermal displacement correction by modeling the lathe l, N3 is the midpoint between the bearings 11 and 12 on the main shaft 2, and N2 is the vertical line passing through N and the horizontal line passing through N3. It is the intersection with N5 is the center position of the system consisting of the index house 22 and the talent 3, and corresponds to the center positions of the linear guides 24 to 27 provided on the lower surface of the index house 22. N4 is the intersection of the system consisting of the bed 16 and the ball bed 29 and the vertical line passing through N. N6 is an intersection point obtained by drawing a perpendicular line from the tool cutting edge point P2 to the system consisting of the index house 22 and the talent 3. And N1 and N
Let the distance between 2 be l,, the distance between N2 and N3 be l2, P and N
Let the distance between 3 be L, and the distance between N and N4 be j2 and N4.
The distance between and N5 is f5, and the distance between N,, and N6 is j!
Let the distance between Nb and P2 be l.

In the model shown in FIG. 4, if the hectors from the reference point N to the target coordinate Pl and the actual machining coordinate P2 are respectively P + N+ and P z N + , then p, P
,=N,P. -N,P. becomes. Also, p2p, one (ΔX, Δy, Δz)
When calling, this P2P. is considered to be the machining error of Talent lathe 1. At this time, ΔX becomes an error in the radial direction, which greatly affects the machining accuracy of the lathe. Therefore, if we express ΔX in the formula, ΔX - ηX (j2,) - ηX<it) - η8 (poor.)
? ηX (f4)+η. (/!5)+η. (72.)η
．． (j27)+n, ・θ13-l:l(θ,2
+θ22) ~ 25(θ33+θ43)+E6(θ3
■+θ4■+θ5■), ...(1). Here, ηx (i): Displacement θ1 of each part (i part) due to heat in the X direction. :J direction of each part (i part) (1=X, 2=Y,
3-Z) Considering the above formula (1) briefly, the amount of displacement of the workpiece in the X direction can be expressed as ηX (W) - ηX (j2.) + ηX (22) + η.
(pz)...(2) The amount of displacement in the X direction of the tool is η. (T)-η. (L)+η−(ps)×ηX (
ib) One η. (2 7) ...(The angular error around the Z axis of the third headstock is θ, = 01, ...
(4) The angular error around the Y axis of the headstock is θ9■ - θ1■
+θ22...[5) 9 10? If the angular error around the Z axis of the tool is θT3-θ33+θ43...(6) and the angular error around the Y axis of the tool is θ1■=θ32+θ42+θ5■...(7), then ΔX11ηX (W) η-(T)+1+ θ83pV
．． 3 θ8■-l, θr*+lb θT1...(8
).

Therefore, in this embodiment, the Cutch sensors 14 and 15 are used to measure ηX (T) and l6θ,2, which have the greatest influence on the machining error due to thermal displacement among the terms in equation (8).

That is, first, the cross slide 19 is positioned at the origin position. Then, the cross slide 19 is moved toward the headstock 13 from this origin position, and the timing at which the first touch sensor 14 and the second touch sensor 15 are turned on is detected. A counter reads the number of output pulses from the encoder 34 until each of the tangent sensors 14 and 15 turns on.

As a result, the tool section thermal displacement calculating section 37 determines the above η8? T
) and the displacement l6θ7■ in the χ direction due to the angular error. This calculation is performed, for example, every 5 minutes to determine the positional deviation due to thermal displacement during processing. Further, for the remaining terms in the equation (8), the amount of change with respect to temperature is determined in advance and stored in a ROM or the like, and the amount of change data is read from the ROM in accordance with the temperature detection result by the temperature sensor 32.

In this way, ΔX is estimated by adding the predicted thermal displacement amount due to temperature and the measured thermal displacement amount due to the Kunchi sensors 14 and 15 and the encoder output.

This ΔX is output to the correction section 40. Correction section 40
, the target coordinates for machining are entered manually from the target value input section 33. In the correction section 40, the machining error (Δχ) is corrected by marking the target coordinates, and the corrected output is output to the tool section movement control section 41. The movement of the tool drive system 35 is controlled by the control signal from the tool drive control unit 41, and extremely highly accurate machining is performed in consideration of thermal displacement of each part.

[Other Embodiments] (a) In the embodiment described above, the tool stand 7 is made up of the cross sleight 19, the index house 22, and the talent 3. However, the structure of the tool stand 7 is not limited to the embodiment described above. The present invention can be similarly applied to a device that is arranged parallel to the main shaft 2 and is movable, and the same effects as in the embodiment described above can be obtained.

Middle) In the above embodiment, the first and second touch sensors 14 and 15 are used as means for detecting the distance between the spindle 2 and the tool rest 7, and as means for detecting an angular error of the tool rest 7 with respect to the main shaft 2. However, each detection means is not limited to the tanti sensors 14 and 15, and any method that can measure the amount of displacement of the front and rear ends of the cross slide 19 with respect to the hend stonk 13 may be used, such as ultrasonic waves, laser light, etc. Any type of sensor may be used instead of a distance sensor or a touch sensor, such as a limit switch or a microswitch.

(C) In the above embodiments, the present invention was applied to the turret 1/lathe, but the present invention can be similarly applied to a lathe without a turret.

〔Effect of the invention〕

In this way, in the present invention, the amount of thermal displacement and angular error between the tool stand and the headstock are detected, and the movement target value of the tool stand is corrected based on this, so machining can be performed with extremely high precision. I can do it. Furthermore, the structure for this purpose is simple, and the lathe main body does not need to be enlarged.

[Brief explanation of the drawing]

FIG. 1 is a control block diagram of a thermal displacement correction device according to an embodiment of the present invention, FIG. 2 is an overall perspective view of a talent lathe to which the thermal displacement correction device is applied, and FIG. 3 is a headstock of the turret lathe. and a schematic plan view of the tool rest portion. FIG. 4 is a modeled view of the headstock and tool rest portion shown in FIG. 3. ■... Talent lathe, 2... Main spindle, 3... Talent, 7... Tool stand, 13... Head stock, 14
．． 15... Tanchi sensor, 19... Cross slide, 22... Index house, 23... Turret shaft, 28... l3 1 4- servo motor with encoder, 29.30... Ball screw, 31... Thermal displacement correction section, 33... Target value input section, 34... Encoder, 35... Tool part drive L
3 7... Tool part thermal displacement calculation part, 39... Addition part, 40... Correction part, 4l... Tool part movement control part.

Claims (1)

[Claims] (1) In a lathe in which a movable tool stand is installed in parallel to a headstock that supports a spindle, a thermal displacement amount detection means for detecting the amount of thermal displacement between the headstock and the tool stand, and a tool for the spindle. Thermal displacement in a lathe comprising an angular error detection means for detecting an angular error of the table, and a correction means for correcting a movement target value of the tool stand based on the detection results of the thermal displacement amount detection means and the angular error detection means. correction device.