JPH05237742A - Correcting method for thermal displacement of machine tool - Google Patents

Abstract

PURPOSE:To improve machining efficiency by shortening the total cycle time required for machining a workpiece of a machine tool. CONSTITUTION:A thermal displacement correcting cycle in which the quantity of relative thermal displacement between a work table 12 to support a workpiece W and a grinding wheel 111 on a wheel spindle stock 11 is detected by displacement sensors 17a, 17b, and the work table 12 is positionally controlled to the grinding wheel 111 according to the quantity of detected thermal displacement to correct the thermal displacement is thrown in between the grinding cycles of a grinding machine 10. An operating time after starting the grinding machine 10 is measured by a timer 25, and until the above measured value attains predeterminate setting up time, the correcting cycle is thrown in, for instance, at short intervals for which several pieces of workpieces W are ground. In an operational stage where the operating time of the grinding machine exceeds its set time, the correcting cycle is thrown in, for instance, at long intervals for which about 10 pieces of workpieces W are ground.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for correcting thermal displacement of a machine tool applied to a cutting machine tool such as a grinder.

[0002]

2. Description of the Related Art In a grinder or other cutting machine tool, thermal displacement occurs in a portion such as a spindle involved in machining of a workpiece due to a temperature change of a movable portion or a temperature change of lubricating oil. This causes variations in the processing accuracy of the object, which causes a reduction in the yield of the workpiece. Therefore, it is necessary to correct the thermal displacement between the machine tool, especially the machine tool such as a grindstone, and the workpiece in order to always obtain stable machining accuracy without being influenced by the temperature change of the machine tool moving part and the lubricating oil. ..

FIG. 3 is a schematic view of a grinder to which a conventional thermal displacement correction method is applied. In FIG. 3, 1 is a bed, 2
Is a work table movably provided on the bed 1, a work W is set on the work table 2, and non-contact displacement sensors 3a and 3b are installed. A column 4 is movably installed on the bed 1, and a spindle head 5 is vertically movably attached to a side surface of the column 4 facing the work table 2. A grindstone 6 for grinding the pre-processed groove w of the workpiece W is attached to the spindle 5 a of the spindle head 5.

In the grinding machine constructed as described above, after the work table 2 is moved to the column 4 side by a preset amount before the grinding is started, the spindle head 5 is moved downward to move the periphery of the grinding wheel 6. The displacement sensor 3 as shown in FIG.
It is located between a and 3b. As a result, each displacement sensor 3
a, 3b is this detects the distance l _1, l ₂ of the respective opposing grinding wheel side, determine the thermal displacement amount of the spindle 5a from the difference between the detected value (l ₁ -l _2). After that, the work table 2 is moved in the direction of the arrow in FIG. 3 so that the amount of thermal displacement is zero, that is, the center of the grindstone width and the center between the displacement sensors 3a and 3b (corresponding to the center of the pre-processed groove w of the workpiece W) match. The relative position between the grindstone and the work table is corrected by moving the work table to. Then, when the above-described position correction cycle is completed, the work table 2 and the spindle head 5 are controlled in accordance with the grinding program to machine the pre-machined groove w of the workpiece W to a predetermined size.

[0005]

However, in the conventional thermal displacement correction method as described above, the position correction cycle is inserted at a constant interval during the operation of the grinding machine, for example, every time a predetermined number of workpieces are ground. Since the method is adopted, there are the following problems. The rate of change of thermal displacement in a machine tool such as a grinder is large in the initial stage from the start of the operating time of the machine tool to t ₁ as shown in FIG. It becomes smaller at the operating time stage of t ₁ or more when the temperature change of oil becomes stable, and the necessity of thermal displacement correction becomes smaller.

Therefore, if the setting interval of the position correction cycle is set in accordance with the thermal displacement change in the initial stage from the start of operation to time t ₁ , the setting interval of the position correction cycle becomes short, and this correction cycle interval is It is suitable for grinding in the early stage of operation when there is a great need for thermal displacement correction, but a position correction cycle is unnecessarily entered when thermal displacement stabilizes and the need for thermal displacement correction becomes small. The total cycle time required for machining the machine tool is increased, and the machining efficiency of the machine tool is reduced.

Contrary to the above, when the closing interval of the position correction cycle is set in conformity with the thermal displacement change in the operation stage in which the thermal displacement is stabilized, the thermal displacement correction in the initial stage of operation becomes insufficient. As a result, the machining accuracy of the workpiece deteriorates, and the product yield decreases. The present invention solves the above problems, and an object thereof is to provide a thermal displacement correction method for a machine tool that can shorten the total cycle time required for machining a workpiece of a machine tool and improve machining efficiency. To do.

[0008]

In order to achieve the above object, the present invention counts the operating time after the machine tool is started by the time counting means, and the count value of the time counting means is set to a predetermined set time. Until it reaches, the thermal displacement correction cycle of the machine tool is input at short intervals, and when the operating time exceeds the set time, the thermal displacement correction cycle of the machine tool is input at long intervals. It is a thing.

[0009]

With the above construction, in the initial stage of the operation start time when the thermal displacement rate of the machine tool is large, for example, the thermal displacement correction cycle is introduced at short intervals where several workpieces are ground, and In the stable operation stage in which the displacement rate is small, for example, the thermal displacement correction cycle is input at long intervals at which about 10 workpieces are ground, so thermal displacement correction according to the thermal change state of the machine tool becomes possible, Highly efficient and accurate work piece machining is possible.

[0010]

EXAMPLES Examples of the present invention will be described below. FIG. 1 is an overall configuration diagram of a thermal displacement correction device for a grinding machine to which the method of the present invention is applied. In FIG. 1, 10 is a grinder, 20
Is a numerical controller for controlling the grinder. Grinder 10
Is equipped with a grindstone base 11 movably provided on the bed (not shown) so as to be movable in the Y-axis direction, and a work table 12 movably provided on the bed (not shown) so as to be movable in the Z-axis direction. And the ball screw 14 rotated by this
The work table 12 is moved in the Y-axis direction by the servo motor 15 and the ball screw 16 rotated by the servo motor 15 in the Z-axis direction.

The grindstone base 11 includes a grindstone 111 for grooving and a motor 112 for rotationally driving the grindstone 111. A workpiece W to be grooved is formed on the work table 12.
Is mounted, and this workpiece W has a pre-machined groove w. Further, on the work table 12, a thermal displacement detection unit 17 that detects a relative thermal displacement amount in the Z-axis direction between the grindstone 121 and the work table 13 is installed.

The thermal displacement detection unit 17 is provided with a channel-shaped support member 171 mounted on the work table 12, and the grindstone 111 is provided at the left and right ends of the support member 171.
Displacement sensors 17a, 1 spaced apart by a distance larger than the width dimension of
7b are installed opposite to each other, and the displacement sensors 17a, 1
By inserting the peripheral edge of the grindstone 111 between the 7b at a predetermined position, the relative displacement amount between the grindstone and the work table due to the thermal displacement of the grinder is detected.

The numerical control device 20 is detected by a central processing unit (hereinafter referred to as CPU) 21 that manages and controls the whole, a memory 22 that stores data such as a grinding program and a thermal displacement correction program, and displacement sensors 17a and 17b. Calculation unit 23 for calculating the relative thermal displacement between the grindstone and the work table from the detected value, and the first timer 2 for counting the time from the end of grinding one workpiece to the start of grinding the next workpiece
4, a second timer 25 that counts the time after the start of the operation of the grinder, and these are connected to the CPU 21.

An operation panel 26 is connected to the CPU 21 of the numerical controller 20, and the operation panel 26 has a CRT (cathode recording) 27 for displaying a grinding program, a power on / off button 28, and an operation stop button 29. The operation start button 30 and the grinding cycle start button 31 are provided. Further, the CPU 21 is connected to the grinding wheel head servo motor 13 and the work table servo motor 15 via the respective drive circuits 32 and 33.

Next, the operation of this embodiment will be described with reference to the flowchart of FIG. First, in step S1, the power on / off button 28 on the operation panel 26 is operated,
The power of the grinding machine 10 and the numerical control device 20 is turned on. In the next step S2, the exercise activation button 30 on the operation panel 26
The operation start switch is turned on by operating. When this ON signal is taken in by the CPU 21, the known coolant supply device and bearing oil supply device are driven, and the grinding machine 10 shifts to a state in which it can perform a grinding operation. Then, in step S3, the first and second timers 24 and 25 are reset and started, and the value A of the thermal displacement measurement interval counter (not shown) configured by the CPU 21 and the memory 22 as software is set to A = A1 + 1. Set to. Here, A1 is a first set value representing the proper number of workpieces to be ground in the initial stage of operation of the grinding machine, which requires a large amount of thermal displacement correction, and corresponds to, for example, several pieces, and
The reason why the first set value A1 is incremented by +1 is that the thermal displacement correction cycle is always entered when the grinding machine restarts operation from the rest.

In the next step S4, the grinding cycle starting button 31 on the operation panel 26 is operated to turn on the grinding cycle starting switch. When this ON signal is fetched by the CPU 21, it is determined in step S5 whether the count value of the first timer 24 is equal to or less than the set value T1. This set value T1 is the workpiece W from the end of the previous grinding to the start of the next grinding.
It corresponds to the preparation time required for the machining and the preparation time spent for cleaning up, and when the set value is T1 or more, it is determined that the idle time cannot be used due to a failure of the grinding machine or the like.

In step S5, the count value is the set value T1.
If they are equal to or less than the same, the process proceeds to step S6, and it is determined whether the count value of the second timer 25 is equal to or less than the set value T2 (T2> T1). This set value T2 is the operating time t of the grinding machine in which the temperature changes of the movable parts of the grinding machine and the lubricating oil are stable, and the necessity of thermal displacement correction becomes small as shown in FIG.
Equivalent to ₁ .

If it is determined in step S5 that the value is equal to or greater than the set value T1, the process proceeds to step S7 and the second
The timer 25 is reset and restarted. Then, in the next step S8, the value A of the thermal displacement measurement interval counter is set to A = A1 + 1, and the process proceeds to step S6.
When it is determined in step S6 that the count value of the second timer 25 is equal to or less than the set value T2, step S9
Then, it is determined whether the value A of the thermal displacement measurement interval counter is less than or equal to the first set value A1. Also, the second timer 2
When it is determined that the count value of 5 is equal to or greater than the set value T2, the process proceeds to step S10, and it is determined whether the value A of the thermal displacement measurement interval counter is equal to or less than the second set value A2. Here, the set value A2 is the appropriate number of workpieces to be ground at the stage when the operating time of the grinding machine is the set value T2 or more and the change in thermal displacement is relatively stable, and the need for thermal displacement correction becomes small. The number is set to be larger than the first set value A1, for example, about 10 pieces.

When it is determined in step S9 that the value A of the thermal displacement measurement interval counter is less than or equal to the first set value A1, the process proceeds to step S14, and the groove grinding of the workpiece W by the grindstone 111 is executed. If it is determined that the value A of the thermal displacement measurement interval counter is greater than or equal to the first set value A1, the process proceeds to step S11, and thermal displacement measurement is performed.

That is, by starting the thermal displacement measuring program, the servo motor 15 is driven to move the work table 12 in the direction of arrow Z1 in FIG. 1, and the thermal displacement detecting unit 17 is moved to a predetermined thermal displacement measuring position. Index to. Thereafter, the grindstone base 11 is moved in the direction of the arrow Y1 in FIG. 1 to insert the peripheral edge of the grindstone 111 between the positioned displacement sensors 17a and 17b. Thereby, the grindstone 11
Displacement sensors 17a, 17b facing both side surfaces of 1 and
The gaps l ₁ and l ₂ between them are detected, and the detection signal is output to the arithmetic unit 23. The calculation unit 23 calculates the relative thermal displacement amount between the grindstone 111 and the work table 12 caused by the thermal displacement of the grinding machine by performing the calculation of L = l ₁ -l ₂ , and outputs this to the CPU 21.

The CPU 21 drives the servo motor 15 by applying a drive signal (pulse) corresponding to the calculated thermal displacement amount to the servo motor 15 through the drive circuit 33 to move the work table 12 to the arrow Z1 in FIG. Or Z
It is moved in two directions, and the position of the work table 12, that is, the amount of thermal displacement is corrected so that the signals detected by both displacement sensors 17a and 17b become equal (step S12).

Thereafter, in step S13, the value A of the thermal displacement measurement interval counter is reset, and the process proceeds to the grinding cycle of step S14. On the other hand, step S
10, the value A of the thermal displacement measurement interval counter
Is determined to be the second set value A2 or less, step S
Proceeding to 14, the groove of the workpiece W is ground. Further, when it is determined that the value A of the thermal displacement measurement interval counter is equal to or larger than the second set value A2, the process proceeds to step S11, and the process of step S11 and thereafter is executed.

In step S15, it is determined whether or not the grinding process for the preprocessed groove w of the workpiece W has been completed. When it is determined that the grinding has ended, the value A of the thermal displacement measurement interval counter is incremented by 1 in step S16. Then, in step S17, the first timer 24 is reset and restarted. In the next step S18, it is determined whether or not the operation starting switch is turned off. If not, the process returns to step S4 to execute the processing of step S4 and thereafter. If it is determined that the operation start switch has been turned off, the process proceeds to step S19 and the power is turned off.

In this embodiment, the grinding machine 1 is used.
The first and second timers 24 and 25 are started by the operation start of 0.
And the time until the grinding cycle is restarted is counted by the first timer 24 and compared with the set value T1. When the counted value is equal to or less than the set value T1, the grinding is counted by the second timer 25. Operating time of panel 10 is set value T
If the count value of the first timer 24 is equal to or greater than the set value T1, the second timer 25 is reset and restarted, and then the count value is set to the set value T2.
If the operating time of the grinder 10 is less than or equal to the set value T2, for example, a thermal displacement correction cycle is inserted every time several workpieces W are ground, and the operating time of the grinder 10 is also set. Is greater than or equal to the set value T2, a thermal displacement correction cycle is inserted every time, for example, about 10 workpieces W are ground, whereby the initial stage of operation and the thermal displacement correction in which there is a great need for thermal displacement correction. Since it is divided into stable stages that are less necessary and the intervals of each thermal displacement correction cycle are set appropriately, the total cycle time required for grinding the workpiece of the grinding machine can be shortened and the grinding efficiency can be improved. It enables high precision grinding with good product yield.

In the above embodiment, the thermal displacement correction of the groove grinding machine has been described, but the present invention is not limited to this, and is similarly applied to other machine tools in which the thermal displacement affects the machining accuracy of the workpiece. can do. Further, the method of the present invention is
The present invention is not limited to the configuration shown in the above embodiment, and can be variously modified without departing from the scope described in the claims.

[0026]

As described above, according to the present invention, the thermal displacement correction cycle of the machine tool is set at short intervals from the time the machine tool is started until the operating time reaches a preset set time. When the machine is turned on and the operating time exceeds the set time, the thermal displacement compensation cycle of the machine tool is turned on at long intervals, so the thermal displacement rate of the machine tool is large. It is possible to input the thermal displacement correction cycle at a lean interval adapted to the operation stage in which the temperature becomes small. Along with this, the total cycle time required for machining the work of the machine tool is shortened, the machining efficiency is improved, and highly accurate machining with good product yield can be achieved.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment in which the method of the present invention is applied to a grinder.

FIG. 2 is a flowchart showing an operation procedure of thermal displacement correction in the present embodiment.

FIG. 3 is a schematic view of a grinding machine to which a conventional thermal displacement correction method is applied.

FIG. 4 is an explanatory diagram showing a relationship between a displacement sensor and a grindstone at the time of detecting thermal displacement in the related art.

FIG. 5 is a graph showing the relationship between the operating time of the grinding machine and the amount of thermal displacement.

[Explanation of symbols]

 W Workpiece 10 Grinding machine 11 Grindstone base 111 Grindstone 12 Worktable 13 Servomotor 15 Servomotor 20 Numerical control device 21 CPU 22 Memory 23 Computing unit 24 First timer 25 Second timer 26 Operation panel

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takayuki Yoshimi 1-1-1, Asahi-cho, Kariya city, Aichi prefecture Toyota Koki Co., Ltd.

Claims (1)

[Claims] 1. A relative thermal displacement amount between a work table supporting a workpiece and a processing tool for processing the workpiece is detected by a displacement sensor, and at least one of the work table and the processing tool is detected according to the thermal displacement amount. In a thermal displacement correction method for a machine tool that inputs a correction cycle for correcting thermal displacement by controlling the position between machining cycles, the operating time after the machine tool is started is counted by a time counting means,
The thermal displacement correction cycle of the machine tool is input at short intervals until the count value of the time measuring means reaches a predetermined set time, and when the operating time exceeds the set time, the machine tool A method for correcting thermal displacement of a machine tool, characterized in that thermal displacement correction cycles are input at long intervals.