JPS61192446A - Correction of thermal displacement of numerical control machine tool - Google Patents

Abstract

PURPOSE:To correct the relative position between a workpiece and a tool by detecting the temperature of the heating part related to the thermal displacement and the temperature of the underground or the ground surface and calculating the thermal displacement amount corresponding to the temperature difference. CONSTITUTION:The temperature of a spindle head 5 is detected by the first temperature detector 14, and the temperature of the ground surface as standard is detected by the second temperature detector 17. A displacement-amount calculating circuit 25 calculates the thermal displacement amount DELTAZ1 due to the rise of the temperature of the spindle head 5 on the basis of each detected temperature T1, T2 and each coefficient (a1), (b1) obtained by a coefficient setting circuit 26. The thermal displacement amount DELTAZ1 is taken into a numerical control apparatus 27 by the correction allowable signal supplied from the NC apparatus 27. The NC apparatus 27 corrects the relative displacement between a tool T and a work 10 due to the rise of the temperature of the spindle head 5 on the basis of the thermal displacement amount DELTAZ1, and the work transfer amount corresponding to the temperature situation at this time is controlled. Therefore, the thermal displacement due to the temperature variation of the spindle head 5 is certainly corrected, and the working precision of the work 10 can be maintained.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a thermal displacement correction method for correcting thermal displacement that degrades the machining accuracy of a workpiece in a numerically controlled machine tool.

``Prior art'' Conventionally, this type of correction method has been used to
For example, the temperature of the spindle head) and the temperature of the base of the machine tool or the atmospheric temperature are measured, and the thermal displacement is calculated using the temperature difference-thermal displacement relational expression according to the difference between these temperatures. I don't know what to do to correct it.
3938, JP 58-132441, JP 58-160042).

"Problem to be solved by the invention" However, as mentioned above, thermal displacement is calculated and corrected according to the atmospheric temperature (room temperature) or the temperature difference between the temperature of the base part of the machine tool and the temperature of the heat generating part. In the event of
There are problems in that it is easily influenced by the environmental conditions around the machine installation location and the machine operating conditions, lacks stability, and cannot obtain sufficient correction accuracy.

Therefore, the inventors of the present invention actually measured the temperature changes in various parts of the machine tool installation location, and as a result, as shown in Figure 7, the temperature on the ground surface (or underground) is stable compared to room temperature or machine tool temperature. 9. I can see what's going on.

In addition, Fig. 7 shows the temporal change when the main shaft is rotated at 300 rpm, and shows the following two actual measurement examples. In the figure, a is the ground temperature in the actual measurement example, b is the room temperature in the actual measurement example, and 0 is the This is the actual measured machine tool temperature.

The present invention has been made in view of the above circumstances, and its purpose is to respond to temperature changes in heat generating parts without being influenced by the environmental conditions around the machine installation location or the machine operating conditions. The object of the present invention is to provide a thermal displacement correction method for a numerically controlled machine tool that can perform thermal displacement correction with high accuracy.

"Means for Solving the Problem" In order to achieve the above object, the present invention detects the temperature of the heat generating part, which is closely related to thermal displacement, and the temperature underground or on the ground surface. Then, the amount of thermal displacement is calculated according to these temperature differences, and the relative position between the workpiece and the tool is corrected based on this amount of thermal displacement6. An embodiment of the present invention will be described based on FIGS. 1 to 4.

In the figure, 1 is the pace of the machine tool 2. A column 3 is provided on this pace 1, and this column 3 is driven by a servo motor for driving the column installed at the end of the pace 1. 4, it is configured into two parts that move in two axes (left and right in FIG. 1). Further, a spindle 5 is mounted on the column 3, and the spindle head 5 is operated by a servo motor 6 installed at the top of the column 3. It is designed to move in the I direction (up and down in Figure 1).

The main shaft type 5 is provided with a main shaft 8 that is rotated by a main shaft motor 7, and this main shaft SVC is
A tool TtrS for machining a workpiece 10 on the table 9 is inserted therein. Furthermore, the above table 9
The base l is fitted into a pair of guide rails 11 and placed on a table base 12.
is moved in the X-axis direction (perpendicular to the plane of the paper in FIG. 1) by a servo motor 13 for driving the table provided on the base 1; 14 have been installed. , 17? ,,floor 1 on which the machine tool 2 is installed
In the appropriate position of 5,! As shown in the igz diagram, the recess 16
is formed, and inside this recess 16 is a temperature measurement 91 for detecting the temperature of the ground surface (underground), which is used as a reference temperature.
17 is out of stock. And this @22 temperature detector 1
The concave part 16 containing Vr heat #19 is filled with a good conductive material 18 having good thermal conductivity such as copper, and the upper surface of the concave part 16 is covered with Vr heat #19. I am a force S thrower n.

The above-mentioned 1st and 2nd detectors 14.17 each include a pair of amplifiers 21.22 and an A/D converter (
Analog Digimel converter) via 23°24, respectively n displacement! This displacement amount calculation circuit 25VC is electrically connected to the calculation circuit 25. A coefficient setting circuit 26 is connected to the displacement calculation circuit 25VC.

The y-position calculation circuit 25 then calculates the detected value T of the first temperature detector 14 inputted via the 6-device 21 degree A/D converter 23, the amplifier 22, and the A/D converter 2411r:
The detected value T2 of the second temperature detector 17 is input via
and the coefficient a + h set in the coefficient setting circuit 26
Calculation formula for sz quantity Δz1='l' C
The amount of thermal displacement is calculated by substituting T1-T2''bl.

Here, the actual amount of thermal displacement is Δ2=α・rTl−To)
- Depends on L (α is the coefficient of linear expansion 1/'as' L is the length of the object to be measured μm l, small, the above second temperature detector 1
There is little variation in the detected value of 7, and the initial temperature T. Therefore, by appropriately selecting the coefficient &1*h1, the calculated thermal displacement amount Δz1 and the actual thermal displacement amount Δ2 approximately match. Each coefficient above & 1
a b 1 is determined experimentally in advance and set in the coefficient setting circuit 26 as necessary.

The output of the displacement calculation circuit 25 calculated in this way (
The amount of correction is taken into the numerical control device 27 based on the correction permission signal from Shima et al. Next, is the numerical control device 27 commanded by tape?
This is to control the machining of the workpiece lO in automatic operation by transmitting the information to the respective parts 4, 6.7゜13. The thermal displacement correction method of the invention will be explained.

The numerical control device 27 controls each motor 4.6.7° 13 based on the tape command input in advance, inserts the workpiece 10 into the tip of the spindle 8, and inserts the workpiece 10 into the tip of the spindle 8. (F) machining (and the rotation of the spindle 8 (accompanied by
As the bearings for the spindle 8 generate heat, the temperature of the spindle head 5 begins to rise. At this time, the temperature of the spindle head 5 is
At the same time, the reference ground surface temperature is detected by the wJ2 temperature detector 17, and each temperature is detected via the amplifiers 21 and 22 and the A/D converters 23 and 24f. Detection value T1 of device 14.17 #
Since T2 is input to the displacement amount calculation circuit 25, this displacement amount calculation circuit 25 calculates each of the above detected values T1jT2.
and each coefficient a1. from the coefficient setting circuit 26. ,b,
Based on r, #1 displacement value Δ due to one rise of spindle head 5
z1 f is being calculated. Then, this thermal displacement amount Δz1
is determined by the correction permission signal from the numerical control device fi27.
Based on this thermal displacement amount (correction amount) Δz1, the numerical control device 27 adjusts the main shaft W.
The relative displacement between the tool T and the workpiece 10 due to the temperature rise of R5 is corrected, and the machining movement amount is controlled according to the one-change situation at that time.

Therefore, the thermal displacement caused by the temperature change of the spindle head 5 is reliably corrected, and the machining accuracy of the workpiece 10 does not deteriorate.

The above effect is shown in the following characteristic diagram showing the temporal change in the amount of thermal displacement in diagram wIJ4.
When rotating under the operating conditions (see Figure 3) according to the current machining state, correction is performed using the method of the present invention. As is clear from the figure, when the correction method of the present invention is used, the thermal displacement t is significantly reduced.

In addition, the above! i! In the winding example, the second temperature detector 17
9. As shown in FIG. 5, a deep detection hole 30 should be bored in the floor 15 in place of the recess 16 in the recess 16. In addition, a good conductivity member 18 covering the second temperature sensor 17 and the second temperature sensor 171 is installed at the lower part of the detection hole 30, and the upper part of the detection hole 30 is insulated through the air layer 31. As shown in FIG. 6, instead of the air layer 31 and the heat insulating material 32,
It is also possible to use a structure in which a filling member 33 made of a heat insulating material is essentially made of a material equivalent to No. 5.

"Effects of the Invention" As explained above, the present invention detects the temperature of the heat generating part, which is closely related to thermal displacement, and the temperature underground or on the ground surface, and detects the temperature according to the difference between these temperatures. This method calculates the thermal displacement fi and corrects the relative position between the workpiece and the tool based on this amount of thermal displacement. By converting the temperature difference between the heat generating part and the heat generating part based on the temperature inside or on the ground surface into the amount of thermal displacement, changes in the relative position between the workpiece and the tool inserted into the machine tool due to thermal deformation. This method has excellent effects in that it can be reliably corrected, the machining accuracy of the workpiece can be maintained in a good state, no defective products are produced, and the yield of products is improved.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram of a numerically controlled machine tool that implements the correction method of the present invention, and FIG. 2 is a sectional view showing the installation state iI of the second temperature sensor. Figure 3 is a characteristic diagram showing the operating conditions of the main shaft.
Fig. 4 is a characteristic diagram of the amount of thermal displacement under the operating conditions shown in Fig. 3, Fig. 5 is a sectional view showing the other 81 states of the second temperature sensor, and Fig. 6 is a diagram showing the other 81 states of the second temperature sensor. FIG. 7 is a sectional view showing the installation condition and track of the machine tool, and FIG. 7 is a characteristic diagram showing temporal changes in temperature of various parts of the place where the machine tool is installed. 5... Spindle head, 10... Workpiece, 1
4...tlX1 temperature sensor, 17...
Second temperature detector, T... Tool, Δz1...
...Thermal displacement amount (correction amount).

Claims (1)

[Claims] The temperature of heat-generating parts that are closely related to thermal displacement, such as the spindle head, and the temperature of the ground or the ground surface are detected, and the amount of thermal displacement is calculated according to the difference between these temperatures, and based on this amount of thermal displacement. A thermal displacement correction method for a numerically controlled machine tool, the method comprising: correcting the relative position between a workpiece and a tool.