JPH04146046A - Thermal displacement correction device for lathe - Google Patents

Abstract

PURPOSE:To enable correction of the position of a tool with respect to thermal displacement from the operation start time after stoppage by detecting the relative thermal displacement between a spindle stock and a tool rest, computing a specified computation from the detection value, and correction the feeding command value of the tool rest. CONSTITUTION:At the time of operation start-up of a lathe 1 or at an arbitral time after the start-up, thermal displacement detection means S1, S2 detect the relative thermal displacement between a spindle stock 7 and tool rest 8 in a condition where the tool rest 8 is made close to the spindle stock 7. Then, a compensation computation means 24 computes the thermal displacement of tool position T of tool rest 8 from the thermal displacement of plural number of portions computed, and by the thermal displacement computed a feed command value 25 is corrected. With this arrangement, the working accuracy is improved and thereby the error correction of thermal displacement can be made even with respect to the first workpiece after the stoppage.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a lathe thermal displacement correction device for a turret lathe or the like.

[Conventional technology]

In a lathe, a large amount of heat is generated by cutting, so thermal displacement of various parts causes deviations in the precision position and direction of the main spindle, or deviations in the axial center position and direction of a tool rest such as a turret. As a result, machining accuracy decreases.

Conventionally, in NC lathes, in order to deal with such thermal displacement and tool wear, a touch sensor installed in a turret, etc. measures the diameter of a machined workpiece, and when machining the next workpiece, The tool position is corrected so that machining errors fall within dimensional tolerances.

[Problem to be solved by the invention]

However, since this method measures the machining error after machining and corrects it when machining the next workpiece, when correcting thermal displacement, it is not possible to correct the first one after the operation is stopped. That is, since the thermal displacement of the lathe returns when the operation is stopped, the error measurement value of the previous workpiece cannot be used when the operation is resumed after the stop.

SUMMARY OF THE INVENTION An object of the present invention is to provide a thermal displacement correction device for a lathe that can correct a tool position with respect to thermal displacement from the start of operation after a halt.

[Means to solve the problem]

The structure of this invention will be explained with reference to FIG. 1 corresponding to an embodiment.

The thermal displacement correction device for this lathe includes a thermal displacement amount detection means (Sl ),
(S2) and performs a predetermined calculation from the detected value to correct the feed command value of the tool rest (8).
24). The turret (8) is attached to the main shaft (6
).

[For production]

Detection by the thermal displacement amount detection means (SL), (S2) is as follows:
This is done when the lathe (1) starts operating or at any time after starting.

The thermal displacement amount detection means (Sl) and (S2) are connected to the tool rest (8).
) is close to the headstock (7), and the amount of relative thermal displacement between the headstock (7) and the tool rest (8) is detected. The correction calculation means (24) calculates the thermal displacement amount of the tool position (T) of the tool post (8) from the detected thermal displacement amounts at the plurality of locations, and uses the calculated thermal displacement amount to set the feed command value (25 ) is corrected.

〔Example〕

An embodiment of the present invention will be explained based on FIGS. 1 to 5.

In FIG. 2, the lathe 1 is a turret lathe, and the cross slide 3 on which the turret 2 is mounted is placed on the rail 5 of the bed 4 in a direction (X-axis direction) perpendicular to the axial direction (Z-axis direction) of the main shaft 6. It is set up so that it can be moved freely. The turret 2 and cross slide 3 constitute a tool post 8. The spindle 6 is supported by a spindle stock 7 installed on the bed 4, and spindle chucks 6a and 6b are exchangeably mounted thereon.

As shown in FIG. 1, a pulley 9 for rotational driving is provided at the rear of the main shaft 6, and a chuck cylinder 10 is connected thereto. The chuck cylinder 10 drives the main shaft chucks 6a and 6b to open and close via a chuck drawbar (not shown) passing through the main shaft 6.

The cross slide 3 supports the turret 2 so as to be rotatable and movable back and forth (Z-axis direction) via the turret shaft 2a, and has a built-in mechanism for indexing and rotating the turret 2 and for moving the turret 2 back and forth. Movement of the cross slide 3 is performed by a servo motor (not shown) via an X-shaped ball screw II.

The turret 2 has a polygonal drum shape from the front, and a tool 12 is attached to each peripheral surface portion.

On the side surface of the headstock 7, there are two detectors S1. S2 is attachment via the attachment jig 13.

These detectors Sl and S2 detect the amount of displacement by contacting the detection plate 14 provided on the side surface of the cross slide 3 when the cross slide 3 is brought close to the headstock 7. is used. Both detectors Sl,
S2 are arranged apart from each other in the axial direction of the main shaft 6, and are arranged at the same height as the main shaft 6.

These detectors S1. The output of S2 is inputted to the controller 17 via the amplifiers 15 and 16 in the thermal displacement controller 18, A/D converted in the controller 17, and then transferred to the **device f19 by serial transmission.

The f1411I device 19 is composed of a programmable controller and an NC device, and includes an arithmetic control section 21 that analyzes and executes the cannibal program 20, and a servo driver 22 that drives the servo motor 23 for each axis. The calculation control section 21 is provided with a correction calculation means 24.

The correction calculation means 24 performs a correction calculation, which will be described later, from the amount of thermal displacement at the two locations obtained by the output of the thermal displacement controller I8, shifts the tool coordinate system, and adjusts the X of the cross slide 3.
This is to correct the axis feed command value 25. The Y-axis feed command value 26 and the two-axis feed command value 27 are transferred to the servo driver 22 as they are.

A correction operation using the above configuration will be explained. Detection of thermal displacement is
The following procedure is performed at the start of operation or at predetermined time intervals after the start of operation.

That is, the cross slide 3 is brought close to the headstock 7 to the set position, and both detectors S1. S2 is brought into contact with the detection plate I4 of the cross slide 3. This contact causes the detector S1. which consists of an actuating transformer. In S2, the relative thermal change positions sl and s2 (FIG. 4) in the X-axis direction between the headstock 7 and the cross slide 3 at two locations in the axial direction of the spindle 6 are detected.

Based on the relative thermal displacement amounts sl and s2, the correction calculation means 24 calculates the
Calculate the error δX in the axial direction.

δx=[(a+b)sl-bs2]/a ■
In the above formula (2), a is the distance between both side extractors SL, 32 (FIG. 5), and b is the distance from the detector S2 to the workpiece machining point W. From FIG. 4, relative thermal displacement amount s1. It can be seen that the error δX can be calculated using the formula s2. Note that this calculation is an approximate calculation assuming that the thermal displacement of each part has linearity.

In FIG. 2, when the spindle chuck 6a is replaced with the spindle chuck 6b for gripping a short workpiece 28, the workpiece machining point moves to wb, so the distance b2 (
Figure 5).

The correction calculation means 24 corrects the X-axis feed command value 25 by the error δX calculated in this way and outputs it to the servo driver 22.

By correcting the X-axis feed command value 25 in this way,
The X between the workpiece machining point W, which is the target coordinate, and the cutting edge T of the tool 12, with respect to the deviation of the spindle 7 in the minute position and direction due to thermal displacement, and the deviation of the turret 2 in the minute position and direction.
Eliminates errors in the axial direction and improves machining accuracy. Moreover, since the error is detected and corrected before machining, it is possible to correct the error for thermal displacement from the time when the first workpiece 28 after the suspension of operation is machined. Therefore, the occurrence of defective products can be prevented. Although the thermal displacement in the Y-pongee and Z-axis directions was not corrected, the thermal displacement in these directions hardly affects the machining accuracy.

In addition, although the above error correction was calculated assuming that the coordinate systems of the spindle 6 and the headstock 7 coincide, the chuck cylinder lO
Strictly speaking, the spindle 6 tilts with respect to the headstock 7 due to thermal displacement of various parts due to large temperature changes in the chuck drawbar and the chuck drawbar. Therefore, if it is necessary to perform correction with higher accuracy, the relationship between the inclination of the main shaft 6 and the temperature is determined through experiments or the like, and the correction is performed by the correction calculating means 24. That is, by providing appropriate temperature measuring means,
When performing the displacement detection, the temperature is measured, and the correction amount for the inclination of the spindle 6 with respect to the headstock 7 is added to the value of δX, which is the calculation result of the above equation (2), to perform correction.

Next, the relationship between thermal displacement and correction will be explained using a simple model shown in FIG. The figure shows each part of the lathe as x, y,
It is modeled using line segments in each direction of z, and includes the headstock 7, the main shaft 6, a portion 32 consisting of the bed 4 and the X-wheel ball screw 11, the cross slide 3, and the turret shaft 2.
This is an expression for a and turret 2. The O mark indicates a sliding part. O is the reference point, fl-J! 7 is the length of each part.

In the same figure, if the machining point error is fδJ, then fδ)=
It is given by TW. The component of the TW in the X-axis direction is the error δX in the X-axis direction, and this error δX affects the accuracy of the lathe. δX is expressed by the following formula (■).

δ x=-+7x(1) +nx(d)+11 θ,
.

13θ−z f5 θrs+I16 θ7□ ■Here, nX indicates a translation error, and θ indicates an angular error. The codes 1 to 3 appended to θ are 1 for around the X axis and 2 for around the X axis, respectively.
indicates rotation around the Y axis, and 3 indicates rotation around two axes. In the above formula (■), nX) is the elongation of the workpiece in the X-axis direction, and B(expansion) = ηx(j'l) + ηxU'2)
+ ηx (j!3) ηx (T) is the elongation of the tool in the X-axis direction, nX (T) = rtX (14) + 1
x(15+rt x(16)-ηx(77) θ1. is the rotation of the headstock 7 around the two axes, θw, = θ
1°θ1. is the rotation of the headstock 7 around the Y axis, and θW2°θ
I2+θZ2 θA is the rotation of the tool around two axes, θT, = θ3.
+θ4°θa is the rotation of the tool around the Y axis, and θ7. =θ3.
+θ4. +θ,.

It is. Note that θ1. teeth,! This is the angular error around each axis of the portion whose length is indicated by 1 to 17.

In this way, the error δX shown by the above equation (2) is the relative thermal displacement amount s1. From s2, it is approximately calculated and corrected as J in the above equation (2).

FIG. 6 shows another embodiment. In this example, a touch sensor is used as the black discoloration amount detection means Sl, 32, and the cross slide 3
The amount of displacement is detected from the output of the feed detector 29 of the X-axis ball screw If when the X-axis ball screw If comes into contact with each of the thermal displacement amount detection means SL, S2. Feed detector 29 consists of a rotary encoder connected to an X-axis servo motor.

In the thermal displacement controller 30, the cross slide 3 moves from the origin position to each thermal displacement amount detection means S1. Count the number of pulses until it touches S2. Other structural effects are the same as in the previous embodiment.

In the embodiment shown in FIG. 1, a displacement meter that performs non-contact detection may be used as the detector 31°S2.

FIG. 7 shows yet another embodiment. In this example, the headstock 7
A mounting jig 31 is provided that extends from the precise position of the spindle 6 on the top surface to the side surface of the headstock 7, and the detector S is installed at the height of the spindle 6.
1 and S2 are attached.

With this configuration, deviations in the coordinate systems of the spindle 6 and the headstock 7 due to thermal displacement are reduced, and correction can be performed with even higher accuracy.

Although the above embodiment has been described with reference to the application to a turret lathe, the present invention can be applied to various other types of turret type lathes.

〔Effect of the invention〕

The thermal displacement correction device for a lathe of the present invention is provided with thermal displacement amount detection means for detecting the relative thermal displacement amount between the headstock and the tool rest at a plurality of locations separated in the axial direction of the spindle, and a predetermined value is determined from the detected value. Since a correction calculation means is provided for calculating the feed command value of the tool post, it is possible to eliminate machining errors due to thermal displacement and improve machining accuracy. Furthermore, there is an effect that the thermal displacement error can be corrected even for the first workpiece after the pause.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of the configuration of an embodiment of the present invention, Fig. 2 is a perspective view of the lathe, Fig. 3 is an explanatory diagram of the shape model of the lathe, and Fig. 4 is the relative thermal displacement amount. An explanatory diagram of the relationship with error, FIG. 5 is also an explanatory diagram of the distance relationship,
FIG. 6 is a configuration explanatory diagram of another embodiment, and FIG. 7 is a partial front view of a lathe in still another embodiment. 2-...Turret, 3...Cross slide, 6...
Spindle, 7... Headstock, 8... Turret, 12... Tool, 14... Detected plate, 18... Thermal displacement controller, 19... Control device, 24... Correction calculation means, 2
5...X-axis feed command value, 28...Workpiece, 31. S
2...Detector (thermal displacement detection means), sl, s2.
... Relative thermal displacement amount, T - Cutting edge, W ... Workpiece machining point, δX ... Error Patent applicant Murata Machinery Co., Ltd. Agent Masashi Noda Patent attorney Figure Figure Figure Figure

Claims (1)

[Claims] thermal displacement amount detection means for detecting relative thermal displacement amounts between the headstock and the tool rest at a plurality of locations spaced apart in the axial direction of the spindle, with the tool rest moving in a direction perpendicular to the spindle being brought close to the headstock; , correction calculating means for calculating the thermal displacement amount of the tool position of the tool post from the detected thermal displacement amounts at the plurality of locations, and correcting the feed command value of the tool post by the calculated thermal displacement amount. Lathe thermal displacement correction device.