JPH11110021A - Precision machining method and device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stabilize the blade edge position of a tool by calculating the cooling liquid supply start timing, the spindle start timing and the machining start timing according to the front and next spindle rotational speeds and based on each stored data and then performing the start of supply of the cooling liquid, the start of a spindle and the start of the machining. SOLUTION: The displaced variable of a spindle 7 is previously calculated and stored in a storage means 31 in its each state that is set when the thermal deformation of the spindle 7 is almost stabilized against its each rotational speed. Then the data are acquired and stored in the means 31 for the cooling liquid supply start timing of a cooling liquid supply means 17, the spindle start timing and the machining start timing which are decided with respect to the displaced variable of the spindle 7. A control means 29 calculates the cooling liquid supply start timing, the main spindle start timing and the machining start timing according to the front and next main spindle rotational speeds and based on those stored data. Thus, the supply of the cooling liquid, the spindle 7 and the machining are started in each calculated timing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a precision machining method and apparatus for precisely machining a workpiece by controlling thermal displacement of a spindle of a machine tool.

[0002]

2. Description of the Related Art A machine tool has a spindle cooling means for circulating a coolant whose temperature is controlled around a spindle or a periphery of the spindle in order to suppress thermal deformation of the spindle. When machining a workpiece in a machine tool, usually, the start of the spindle and the start of the supply of the coolant by the spindle cooling means are performed simultaneously, and the method is started after the thermal deformation of the spindle is almost stabilized.
Then it takes time.

[0003] As one method for solving this,
There is a dynamic thermal displacement correction method as disclosed in JP-A-9-70739. This is to start processing before the thermal deformation of the machine is almost stabilized, and to theoretically eliminate the processing error by performing the thermal deformation correction.However, the processing is started before the machine is stabilized, and the small diameter Not suitable for precision machining with tools.

[0004]

For the purpose of tool exchange, tool length measurement, confirmation of machining results of a workpiece by an operator, the spindle is temporarily stopped, and thereafter, the spindle is activated to resume machining. However, a change in the thermal displacement of the spindle that occurs during the stop / start of the spindle causes a problem in machining accuracy. Therefore, it is necessary to warm up the spindle device at the time of resuming machining to return it to the same state as before the temporary stop.
An object of the present invention is to shorten the warm-up time and improve the processing accuracy.

[0005] To further explain, when the machining including the automatic tool change or the machining with different spindle rotation speeds is continuously performed, the change in the spindle thermal displacement due to the length of the spindle stop time, and the change in the spindle speed due to the difference in the rotation speed. Due to the difference in the amount of thermal displacement, the position of the cutting edge of the tool mounted on the tip of the spindle fluctuates, resulting in a processing error. The present invention stabilizes the cutting edge position at the machining rotational speed in a shorter time and secures high machining accuracy by optimally controlling the start timing of the spindle cooling device with respect to the stop time of the spindle and changes in the spindle rotational speed. It is intended to do so.

As shown in FIG. 5, thermal deformation of the spindle has a time region in which the spindle is stabilized in accordance with each spindle rotation speed.
Once in this time range, there is a phenomenon that the spindle does not undergo any further thermal deformation and becomes stable. The present invention has been made by focusing on the fact that this phenomenon is reproducible in each device.

One method of reducing the warm-up time from the start of the spindle at each rotation speed to the entry into the stable region is to change the speed from a low rotation speed to a high rotation speed, and to reduce the warm-up time from the high rotation speed. The speed may be shifted to a low rotation speed.

This is accomplished by first obtaining a spindle displacement δ as shown in FIG. 4, and using this δ as a medium amount, a delay time (spindle low rotation speed → In the case of a high rotation speed), the spindle stop time (in the case of the spindle high rotation speed → low rotation speed), and the warm-up time from the start of the spindle to the start of machining (in the case of using the method of the present invention) can be obtained.

For example, in continuous machining including tool change, when machining accuracy on the order of several microns (steps on the machining surface by various tools) is controlled, not only changes in the cutting edge position due to differences in machining rotational speed, but also changes in the same rotational speed. Even if all the operations can be carried out, the spindle is cooled due to the stop of the spindle during tool change, and the fluctuation of the cutting edge position of the tool due to the influence cannot be ignored.

That is, in the conventional processing method, all the finished surfaces are processed again with one tool. However, this is not practical due to the problems of tool wear, tool types (ball end mill, flat end mill, etc.) required by the machining shape, limitations on tool size (use of minimum tools), and machining time. In continuous machining including tool change, the machining rotation speed is set to be the same as much as possible irrespective of the tool type and tool size, and the amount of change in the tool edge position due to the difference in the rotational speed of the spindle thermal displacement is suppressed. Here, even at the same rotation speed, a running operation for several minutes is required until the position of the cutting edge is stabilized by the effect of stopping the spindle during tool change. In continuous machining including tool change, if the machining rotation speed is different before and after the tool change, do not perform machining immediately after the tool change, perform preliminary running, measure the tool length again after the spindle thermal deformation is stabilized, and machine again. To start. This preliminary running time requires, for example, about 10 minutes. Particularly in high-speed, high-precision processing machines, the processing accuracy of the machine itself is improved and the processing time is shortened. It is important to stabilize.

[0011]

Means for Solving the Problems The present invention is configured as follows to solve the above-mentioned problems. (1) In a precision machining method using a machine tool in which a spindle device is warmed up before machining to start machining of a workpiece after thermal deformation of the spindle is substantially stabilized, a cooling means for the spindle device by circulation of a coolant is used. The main shaft displacement amount in each state when the thermal deformation of the main shaft is substantially stabilized with respect to each rotational speed of the main shaft is obtained and stored in advance, the main shaft is started to reach the commanded rotational speed, and the thermal deformation of the main shaft is substantially reduced. Each data of the coolant supply start timing, the spindle start timing, and the machining start timing of the cooling means with respect to the spindle displacement amount that quickly reaches the spindle displacement amount at the time of stabilization is obtained and stored in advance, and in actual machining, Coolant supply start timing, spindle start timing, and machining start timing in the machining according to the spindle rotation speed and the next spindle rotation speed Is calculated based on the stored data, and the start of the coolant supply at each calculated timing,
A precision machining method that starts the spindle and starts machining.

(2) The data of the coolant supply start timing, the spindle start timing, and the machining start timing with respect to the spindle displacement amount from the start of the spindle until the thermal deformation of the spindle is quickly stabilized are determined by the spindle stop time. In actual machining, the actual stop time of the spindle,
The precision machining method according to (1), wherein a coolant supply start timing, a spindle start timing, and a machining start timing in the machining are calculated based on the stored data in accordance with the front spindle rotation speed and the next spindle rotation speed.

(3) In a precision machining device for a machine tool in which a spindle device is warmed up before machining to start machining a workpiece after thermal deformation of the spindle is substantially stabilized, thermal displacement of the spindle of the spindle device is performed. A coolant supply means for circulating a coolant whose temperature is controlled in the spindle or the spindle head so as to control the spindle displacement amount until the thermal deformation of the spindle becomes substantially stable with respect to each rotation speed of the spindle determined in advance. Each data of the coolant supply start timing of the coolant supply means, the spindle start timing, and the machining start timing with respect to the spindle displacement amount from the start of the spindle until the thermal deformation of the spindle is quickly stabilized is stored in advance. In the actual processing, the warming-up time of the spindle device is minimized in accordance with the front spindle rotation speed and the next spindle rotation speed. A precision machining apparatus comprising control means for calculating and controlling a coolant supply start timing, a spindle start timing, and a machining start timing based on the stored data.

(4) The storage means further comprises a coolant supply start timing, a spindle start timing, and a machining start timing with respect to the spindle displacement from when the spindle is started until the thermal deformation of the spindle is quickly stabilized. A plurality of data are set and stored according to the stop time of the spindle, and in the actual machining, the control means controls the actual stop time of the spindle, the timing of starting the supply of the coolant according to the front spindle rotation speed and the next spindle rotation speed, and the start of the spindle. The precision processing apparatus according to (3), wherein the timing and the processing start timing are arithmetically controlled based on the stored data.

[0015]

According to the present invention, a drive shaft and a bearing portion of a spindle of a machine tool head of a machine tool according to the present invention are cooled by a coolant so as not to be affected by a thermal displacement caused by a change in heat generation temperature due to the rotation. Supply is controlled so that the spindle does not generate thermal displacement, so it can respond to changes in the spindle speed and temperature changes due to drive stop, and machining in a short time without thermal displacement of the spindle Can be performed.

[0016]

FIG. 1 is an explanatory view showing a precision machining apparatus including a coolant supply mechanism in a spindle device of a machine tool according to an embodiment of the present invention. FIG. 2 is an operation flowchart of control means in FIG. FIG. 3 is an explanatory diagram for controlling the supply of the coolant in accordance with the spindle rotation speed, FIG. 4 is an explanatory diagram of a spindle displacement amount caused by a change in the spindle rotation speed and a coolant supply timing, and FIG. 5 is a spindle rotation diagram. FIG. 7 is a diagram showing a relationship between a change in speed, time, and a spindle displacement amount.

In FIG. 1, a spindle 7 is rotatably supported on a spindle head 1 by bearings 3 and 5 lubricated with grease.
It is configured to be driven by a built-in motor 9. The tip of the main shaft 7 rotates with a tool T mounted thereon, and performs relative movement in the X, Y, and Z-axis directions with a workpiece fixed on a table (not shown) to process the workpiece. Coolant jackets 11, 13, and 15 are provided in the spindle head 1 so as to be built in the spindle head 1 at the outer peripheral portions of the bearings 3 and 5 and the built-in motor 9, which are portions where temperature changes occur.

A coolant is supplied to each of the coolant jackets 11, 13, and 15 from a coolant supply path 21 via an on-off valve 19 by a coolant supply means 17 provided outside.
The refrigerant is returned to the cooling liquid supply means 17 through 23. When it is not necessary to supply the coolant to the jacket section, the coolant supply means 17 is provided with a coolant circulation path 25 through an on-off valve 19.
To the coolant supply means 17
To be returned to. This is because the cooling liquid supply means 17 is always turned on, and the effect of improving the cooling response as much as possible and the compressor of the cooling liquid supply means 17
The effect of extending the life of the compressor by reducing the ON / OFF frequency can be obtained.

The spindle 7 is driven by controlling the rotation of the built-in motor 9 by the NC device 27. The control is performed by controlling the NC device 27 by the control means 29, and at the same time, the cooling is performed in connection with the NC device 27. The opening / closing valve 19 for controlling the flow of the cooling liquid from the liquid supply means 17 is also controlled. It should be noted that the control means 29 is performed in consideration of information from a storage means 31 provided separately.

FIG. 2 is an operation flowchart of the control means 29 according to the present invention. Consider a case in which machining is restarted after stopping the spindle for some reason such as tool change, work state confirmation, tool length measurement, or the like. As shown in FIG. 4A, which stores the front spindle rotation speed, stores the next spindle rotation speed, and then illustrates the spindle displacement amount and the coolant supply timing caused by a change in the spindle rotation speed. ,
A main shaft displacement amount δ corresponding to the difference between the next main shaft rotation speed and the front main shaft rotation speed is calculated from the main shaft rotation amount-main shaft rotation speed curve. When the front spindle rotation speed and the next spindle rotation speed are the same, the spindle displacement amount δ is zero. Here, the main axis displacement is in any direction, but the most prominent Z axis displacement in the main axis direction is referred to in this embodiment.

If the rotation speed of the next spindle is greater than or equal to the rotation speed of the front spindle, the coolant jackets 11, 13,.
Turn off the coolant supply to 15. Thereafter, the spindle is started in response to a spindle start signal, and the spindle stop time until the spindle is started is measured. The spindle stop time curve is calculated from the coolant supply delay time-spindle displacement amount curve as shown in FIG. The delay time corresponding to the previously calculated spindle displacement amount δ is calculated, and after the delay time has elapsed, the coolant supply means 17 is activated to start coolant supply.

Further, a warming-up time corresponding to the spindle displacement δ obtained previously is calculated from a warming-up time-spindle displacement amount curve as shown in FIG. 4D, and after the spindle is rotated by the warming-up time, Start processing.

If the rotation speed of the next spindle is smaller than the rotation speed of the front spindle, it is checked whether the stop time of the spindle is less than 5 minutes. If the rotation speed is less than 5 minutes, the coolant is supplied to the coolant jackets 11, 13, and 15. 4A, the spindle displacement amount δ corresponding to the spindle rotation speed difference shown in FIG. 4A, and the displacement amount δ previously obtained from the spindle stop time-spindle displacement amount curve as shown in FIG. 4C. Calculate the spindle stop time corresponding to. Even if a spindle start signal is issued, the spindle is stopped only for the calculated spindle stop time. Thereafter, the spindle is started at the next spindle rotation speed, and thereafter, in the same manner as when the next spindle rotation speed is greater than or equal to the front spindle rotation speed, the warming-up time is calculated from the warming-up time-spindle displacement amount curve, and the warming-up time elapses. Then, the processing is started.

If the spindle stop is not less than 5 minutes (more than 5 minutes), the spindle is started upon receiving a spindle start signal as in the case where the next spindle rotation speed is greater than or equal to the front spindle rotation speed. Then, the processing path on the left side of the operation flowchart of FIG. 2 is taken.

Referring to FIG. 4 further, as shown in (a), when the speed of the main shaft is changed from 20,000 to 30,000 / min, when the thermal deformation of the main shaft is stabilized, the main shaft displacement between them is δ μm. is there. Note that the spindle is 30
The same applies when shifting from 000 to 20000 / min. As shown in (b), the delay time (the time from the start of the main shaft to the start of the supply of the coolant) is obtained by using the displacement amount δ of the main shaft (when the main shaft rotation speed is low → high). As shown in (c), when the speed is changed from 30,000 to 20,000 / min, the stop time of the spindle is obtained via δ (when the spindle rotation speed changes from high to low). As shown in (d), the machining start timing after starting the spindle through δ is known.

According to the present invention, a diagram showing the relationship between the elapsed time and the displacement of the spindle in FIG. 3A showing a case where the spindle is shifted from a low rotation speed to a high rotation speed, 3 (b), which shows the case where the gearshift is performed, shows that the present invention makes it possible to stabilize the displacement of the spindle according to the present invention, as compared with the spindle displacement curve in the conventional case indicated by a dashed line in the figure. It can be clearly seen that the time for performing the operation is reduced.

[0027]

As described above, according to the present invention,
In order to stabilize the cutting edge position of the tool in a short time, it is possible to optimally control the coolant supply start timing of the spindle cooling device according to the command rotation speed at the time of starting the spindle. The position of the cutting edge is stabilized in a short time, and it is possible to secure high processing accuracy without a step in continuous processing including temporary stop of the spindle such as tool change.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing a precision machining device including a coolant supply mechanism in a spindle device of a machine tool according to an embodiment of the present invention.

FIG. 2 is an operation flowchart of a control unit in FIG. 1;

FIG. 3 is an explanatory diagram of a case where the supply of a coolant is controlled according to a spindle rotation speed.

FIG. 4 is an explanatory diagram of a spindle displacement amount caused by a change in a spindle rotation speed and a coolant supply timing.

FIG. 5 is a diagram showing a relationship between a change in spindle rotation speed, time, and spindle displacement.

[Explanation of symbols]

 1 Spindle head 3,5 Bearing 7 Spindle 9 Built-in motor 11,13,15 Cooling jacket 17 Coolant supply means 19 On-off valve 21 Coolant supply path 23 Coolant recirculation path 25 Coolant circulation path 27 NC unit 29 Control means 31 Storage means

Claims (4)

[Claims] 1. A precision machining method using a machine tool for warming up a spindle device prior to machining and starting machining of a workpiece after thermal deformation of the spindle is substantially stabilized, wherein cooling of the spindle device by cooling fluid circulation. Means is provided, and the main shaft displacement amount in each state when the thermal deformation of the main shaft is substantially stabilized with respect to each rotational speed of the main shaft is obtained and stored in advance. The respective data of the coolant supply start timing, the spindle start timing, and the machining start timing of the cooling means with respect to the spindle displacement that quickly reaches the spindle displacement when the temperature is substantially stabilized are obtained and stored in advance, and the actual machining is performed. , The coolant supply start timing, the spindle start timing, and the machining start in the machining according to the front spindle rotation speed and the next spindle rotation speed. Calculated based on the data obtained by said storing the timing, initiation of the cooling liquid supplied in the computed timing, activation of the main shaft, precision machining method and performing start processing. 2. The data of the coolant supply start timing, the spindle start timing, and the machining start timing with respect to the spindle displacement amount from the start of the spindle until the thermal deformation of the spindle is quickly stabilized are converted to the spindle stop time. In actual machining, the actual stop time of the spindle, the coolant supply start timing, the spindle start timing, and the machining start timing in the machining are stored according to the front spindle rotation speed and the next spindle rotation speed. 2. The precision processing method according to claim 1, wherein the calculation is performed based on each data. 3. A precision machining device for a machine tool in which a spindle device is warmed up prior to machining to start machining a workpiece after thermal deformation of the spindle is substantially stabilized. A coolant supply means for circulating a coolant whose temperature is controlled in the spindle or the spindle head to control the spindle displacement amount until thermal deformation of the spindle is substantially stabilized for each rotation speed of the spindle determined in advance; The timing of starting the supply of the coolant by the coolant supply means with respect to the displacement of the spindle from the start of the spindle until the thermal deformation of the spindle is quickly stabilized,
Storage means for pre-storing the data of the start-up timing of the spindle and the data of the machining start timing; in actual machining, the warm-up time of the spindle device is minimized according to the front spindle rotation speed and the next spindle rotation speed. Control means for calculating and controlling a coolant supply start timing, a spindle start timing, and a machining start timing based on the stored data. 4. The storage means further includes: data of a coolant supply start timing, a spindle start timing, and a machining start timing with respect to the spindle displacement amount from when the spindle is started to when thermal deformation of the spindle is quickly stabilized. Are set and stored according to the stop time of the spindle, and the control means performs the actual machining, the actual stop time of the spindle, the coolant supply start timing and the spindle start timing according to the front spindle rotation speed and the next spindle rotation speed. And controlling the processing start timing based on the stored data.
Precision processing equipment as described.