JPH0419042A - Thermal displacement correction method for machine tools - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention: "Industrial Application Field" The present invention relates to a method for suppressing thermal displacement of machine tools. This system completely corrects the thermal displacement of the machine tool based on the spindle heat generation component due to the temperature difference between the parts and the spindle.

"Prior art and its problems" Traditionally, thermal displacement correction means for machine tools first measure the amount of thermal displacement at locations where thermal displacement is likely to occur, such as the spindle or column, and then calculate the amount of thermal displacement based on this measured value. X, Y.

There is a correction method that corrects and controls the amount of movement in step 2.0 Next, the temperature of the heat generating parts related to thermal displacement, such as the spindle head or column, and the reference temperature of stable parts, such as the bed, which are not related to thermal displacement, are detected, and the above temperature is determined. A method of correcting thermal displacement by calculating the correction amount for each axis using the relational expression between the difference and the main axis displacement was disclosed in Japanese Patent Application Laid-Open No. 58
-132441, Tokukai FF! J60-9G34, Japanese Patent Application Laid-Open No. 61192446, etc.

In the method of measuring the amount of thermal displacement of the spindle etc. using the above means and controlling the correction of this amount of displacement, there is a time lag from the temperature rise of the spindle until the thermal displacement occurs, and the thermal displacement correction currently being executed also takes some time. This is due to the influence of the heat generated previously, and cannot be said to be a correction control that immediately responds to the temperature of the heat generated. This means that the thermal displacement that is currently being corrected is a long time in the past, and the thermal displacement that will occur at the next moment will also be in the past, resulting in a follow-up thermal displacement correction method.

The method of first performing correction control has excellent responsiveness to heat generation temperatures, and has the advantage of being able to pre-read thermal displacement that occurs late and perform correction control.

However, each of the proposed thermal displacement correction means has its own problems. First, JP-A-61-19244
No. 6 is equipped with a temperature sensor on the heat-generating part of the spindle head that undergoes thermal displacement, and calculates the amount of thermal displacement according to the temperature difference with the temperature sensor placed underground or on the ground surface. Based on this amount of thermal displacement, the workpiece is This is to correct the relative position between the tool and the tool. In this method, thermal displacement is corrected only from the spindle heat generation component, and it is impossible to correct the amount of thermal displacement of the column. In addition, Pf No. 60-9634 installs a temperature sensor to detect heat generation of the main shaft, and a temperature sensor in the headstock and the column supporting it, which are affected by the outside air and the temperature rise of the headstock. The thermal displacement of the machine is quantified using an equation that approximates the thermal displacement from the heat generated during machine operation, and the coordinates of the control system are corrected using this numerical value. This method does not detect the difference in temperature from the reference temperature of the bed, etc., which is not easily affected by the outside air, and instead calculates the amount of thermal displacement from the detected value of only the spindle heat generation temperature and the heat generation temperature of the part that receives heat from the outside air or the spindle. Since the correction is performed based on the temperature, the ambient temperature and the reference temperature of the machine are ignored, and it can be said that the correction element is missing. The correction amount for each axis is calculated from the relational expression between the main shaft displacement and the reference temperature of the temperature sensor at the rear of the base, where temperature changes are small, and the thermal displacement is corrected. In this method, apart from the main shaft which has good thermal displacement against thermal changes, the thermal displacement of the column receives heat from the outside air temperature and the main shaft, but since the column shape is asymmetrical, temperature changes and thermal displacement are symmetrical. This does not occur, and the amount of displacement varies greatly depending on the position of the column. Therefore.

It is not preferable to arrange temperature sensors at appropriate positions on the column to detect thermal changes in the column. In the method of performing thermal displacement correction in each axial direction by mixing the three lateral ratio temperatures described above, uniaxial correction is performed.

Using temperature detection at several points from the spindle head or column and the relational expression between the temperature difference minus the temperature at the rear of the base and spindle displacement, the correction amount in each axis direction is calculated, and this correction data is used to select the axis. This signal is output to the NC device at the same time as the signal to correct thermal displacement of the spindle. Therefore, since the thermal displacement amount of the column includes the thermal displacement due to heat conduction from the main shaft, it is not possible to purely detect the thermal displacement of the column and process it as correction data. It can be said that it is lacking.

"Problems and Means to be Solved by the Invention" In view of the above-mentioned problems found in the conventional thermal displacement correction device, the present invention solves environmental components and environmental changes caused by the difference in temperature between a portion that is susceptible to environmental changes and a portion that is not susceptible to environmental changes. It is an object and problem to provide a correction method that completely suppresses the thermal displacement of a machine tool from the spindle heat generation component due to the temperature difference between the spindle and the spindle, which is difficult to receive.

Specific means of the present invention are as follows.

(1) A volume body with a large heat capacity and a volume body with a small heat capacity are respectively placed on a column that is susceptible to environmental @ temperature changes,
Temperature sensors are placed in each of the above volumes and output to the digital transducer, and the amount of column thermal displacement is calculated from the environmental component due to the difference in temperature between the two temperature sensors, and a multiplier for correction is applied to the amount of column thermal displacement. This is a method for correcting thermal displacement of a machine tool in which thermal displacement is corrected by the correction amount obtained by multiplication.

(2) Also, the second means of the present invention is to place a volume body with a large heat capacity and a volume body with a small heat capacity on a column that is susceptible to changes in environmental temperature, and to install a temperature sensor in each of the volume bodies. The amount of column thermal displacement is calculated from the environmental component caused by the difference in temperature between the front temperature sensors, and further temperature sensors are placed on the spindle head and on the bellow R°, which is less susceptible to environmental temperature changes, and the temperature sensor is output to the digital transducer. Output to the transducer, calculate the main shaft thermal displacement amount from the main shaft heat generation component due to the temperature difference of the front temperature sensor, and add each correction amount obtained by multiplying the above column thermal displacement amount and main shaft displacement amount by the correction multiplier. A thermal displacement correction method for machine tools that uses the calculated total correction amount to correct thermal displacement.

"Operation" According to the above two thermal displacement correction methods of the present invention, first, two volumetric bodies with different heat capacities undergo a change in environmental temperature, and the temperature difference is submitted by a sensor. The value is applied to the calculation formula for the amount, multiplied by a multiplication factor, and used as a thermal displacement correction value to drive the NC control device for correction. With this method, it is possible to stably detect a temperature difference between two volumes even in the face of unstable temperature changes and thermal displacements caused by an asymmetric column, and it is also possible to detect a temperature difference at any position on the column. .

Next, the sensor detects the column thermal displacement amount and the spindle thermal displacement amount as a temperature difference, which is applied to the calculation formula for the column and spindle thermal displacement amount, and is multiplied by each multiplier to perform the addition calculation. The NC controller is driven to correct the thermal displacement of the entire machine using the corrected thermal displacement correction value.

Embodiment FIG. 1 shows a block diagram of a machine tool and its control system for implementing the thermal displacement correction method of the present invention. In the figure, a machine tool 1o has a bed 2 and a column 1. Bed 2. A saddle placed on.

The main parts consist of a head (spindle head) 3 that engages with the vertical sliding surfaces of the table 4 and the column 1 and moves up and down, and a main shaft 5 that is visible from the underside. The spindle head 3 is thermally displaced by the heat from the heat source generated by the rotation of the spindle, and the column 1 is thermally displaced to fall toward the spindle head due to a change in environmental temperature. This column 1 generally has an asymmetrical shape and undergoes complex thermal displacements. A special temperature sensor mounting method is used for this purpose.

In the above-mentioned machine tool] 0, a volume body 6 with a large heat capacity and a volume body 7 with a small heat capacity are placed in two stacks on top of the column 1 which is susceptible to environmental temperature changes.

Temperature sensors ST, ST2 are arranged in each of the volumes 6, 7, and these sensors are connected to digital transducers DT.
Column thermal displacement C (ΔX, Δ
y, Δχ) is calculated by the column calculation unit 11, and the correction multiplication factor α is calculated by the calculation unit 11 to this column thermal displacement amount C (ΔX, Δy, Δ2).
The NC control device 14 shifts the movement system (coordinate system) of the machine tool 10 in each axis direction using the correction amount Ht (ΔX, ΔY, Δ2) obtained by multiplying by 3 to control the correction of thermal displacement. There is. The above describes a thermal displacement correction method using only the five-column thermal displacement amount.

Next, a configuration based on the combined thermal displacement amount of the column and the main shaft will be explained. Temperature sensors ST,,ST on column 1.

The mounting is similar, with a temperature sensor ST for detecting spindle temperature changes placed near the spindle 5, and a temperature sensor ST4 placed on the bed 2, which is less susceptible to environmental temperature changes.
These temperature sensors ST, S4 output to the digital transducer DT, and the temperature difference Δ from the previous temperature sensor is outputted to the digital transducer DT.
'r2 is detected. This temperature difference ΔT7 is calculated by calculating the spindle thermal displacement amount S (ΔX, Δy, Δ2) from the spindle heat generation component by the spindle calculation unit 12.
is calculated, and this spindle thermal displacement amount S (ΔX, Δy, Δ2) is multiplied by a correction multiplier β. Of course, the column thermal displacement amount C (ΔX, Δy, Δ2) is also multiplied by the correction multiplication factor α in the column calculation unit 11. The calculation unit 13 inputs the column thermal displacement amount C and the spindle thermal displacement ffi S, and performs addition operations on each to obtain a total correction amount H, (ΔX, ΔY, Δ2). This total correction amount H1 is input to the NC control device 14,
The coordinate system of the x, y, and z axes is corrected and controlled in accordance with the correction amounts (ΔX, ΔY, Δ2).

The flowchart for thermal displacement correction having the above configuration is as follows.
As shown in the figure. The column thermal displacement amount C is (a)...
・“Difference in temperature T of parts (columns) that are easily affected by the environment
, -T2 detection (environmental component)" (b)... "Difference temperature T, -T2 = ΔT, is multiplied by the correction multiplier, and the correction value H of the XYZ three axes is calculated. When correcting the thermal displacement of the machine tool 10 using only the correction data of the column thermal displacement tC, (c)... ``Transfer the correction value H2 to the NC control device'', (d)...・Write to the external workpiece coordinate system of the rNC controller. With this, thermal displacement correction in each axis direction is executed when the machine tool 10 is operated by the NC control device.

On the other hand, when incorporating the spindle heat generation component in combination, (e)... ``Detection of the difference in temperature T-T4 = ΔT2 between the part that is not easily affected by the environment and the spindle (spindle heat generation component)'' is executed in parallel. do. After this, (to)... "multiply the temperature difference ΔT2 by the correction multiplier to calculate the XYZa axis correction 1i H2".

Each of the above correction values H□ and H2 is obtained by (c)... "Both correction values H1 and H2 are subjected to one composite operation (addition operation) in the calculation section." As a result.

Write the obtained total correction value H1 into the external work coordinate system of (d)... rNC control device J, NC control device 1
4, thermal displacement correction in each axis direction is executed when the machine tool 10 is operated.

The correction effect obtained from the thermal displacement correction performed as described above will be explained for each form with reference to FIGS. 3 to 8. FIG. 3 shows the thermal displacement (when the spindle is stopped) under [Ii environmental changes] in each axis direction x1°x2. The displacements of y, y, z are shown. ” The maximum displacement was about 28 um.

FIG. 4 shows the correction method of the present invention applied to FIG. 3 above, and the maximum value is suppressed to 5 um or less.

Figure 5 shows “spindle thermal displacement in constant temperature condition (spindle rotation 60°
00 rpm) indicates the thermal displacement without correction. The thermal displacement of the J main axis in the Z-axis direction has a maximum value of 45 um, which is a large value. On the other hand, FIG. 6 shows a result in which the correction method of the present invention has been implemented, and the correction has been improved to the maximum R value of about ±2 um.

FIG. 7 shows a graph of displacement fluctuation without correction when the main shaft rotates in environment -F with a change in atmospheric decrement (10°C), showing a maximum value of 80 um in the Z-axis direction, and X1.X2.
Even in the Y direction, the maximum thermal displacement amount is 24 to 28 um. Against this.

Then, when the thermal displacement correction of the present invention is performed as shown in Fig. 8,
Even the maximum value was suppressed to 10 um or less, and its correction effect was recognized.

"Effect" When according to the present invention, l! A volume body with a large heat capacity and a volume body with a small heat capacity are each placed on a column that is susceptible to environmental temperature changes, and a temperature sensor is placed on each volume body to output the temperature to a digital transducer. The amount of column thermal displacement is calculated from the environmental components caused by the temperature difference, and temperature sensors are placed on the spindle head and the bed, which is less susceptible to environmental temperature changes, and the output is output to a digital transducer. A machine tool that calculates the spindle thermal displacement amount from the components, and corrects the thermal displacement using the total correction amount obtained by adding each correction amount obtained by multiplying the column thermal displacement amount and the spindle displacement amount by a correction multiplier. Since the thermal displacement correction method is adopted, the sensor detects the thermal displacement amount of the collar 11 and the thermal displacement amount of the main shaft as the respective temperature difference,
This is applied to the calculation formula for each of the column and spindle thermal displacement amounts, and the NC control device is corrected and driven as a thermal displacement correction value for the entire machine that is multiplied by each rider and added, and the unstable temperature caused by the asymmetric column is corrected. In response to changes and thermal displacement,
It is also possible to detect a temperature difference at any position in the upper two columns, where stable temperature difference detection is possible with the two volumes. Furthermore, the spindle thermal displacement amount and the column thermal displacement amount are detected and processed separately, and the machine tool can be corrected and controlled as a final total correction amount, providing an excellent correction effect not found in this type of conventional method. .

[Brief explanation of drawings]

FIG. 1 is a block diagram of a machine tool and its control system for carrying out the method of suppressing thermal displacement of the present invention, and FIG. 2 is a flowchart of the method of suppressing thermal displacement of the present invention. Figure 3 is a characteristic diagram showing thermal displacement of a machine tool due to environmental changes, Figure 4 is a characteristic diagram when correction control is performed in response to environmental changes, Figure 5 is a characteristic diagram showing spindle displacement in a constant temperature state, Figure 6 is a characteristic diagram when the spindle thermal displacement is corrected under a constant temperature condition, Figure 7 is a characteristic diagram of thermal displacement during spindle rotation when the ambient temperature changes, and Figure 8 is a characteristic diagram when the thermal displacement is corrected under the conditions shown in Figure 7. FIG. 1o...Machine tool, l...Column, 3...Spindle head, 5...Spindle, 6, 7...Volume body, ST1 to ST4
...Temperature sensor, DTl, DT2...Digital Melanth juicer, 4 pieces 0. ΔT2...Difference in temperature, 11, 12
．． 13... Arithmetic unit, 14... NC control device, Ho,
H,... Correction value, Hl... Total correction amount, C... Column thermal displacement amount, S... Spindle thermal displacement amount, α, β... Multiplier.

Claims (2)

[Claims] (1) A volume body with a large heat capacity and a volume body with a small heat capacity are each placed on a column that is susceptible to environmental temperature changes, and a temperature sensor is placed in each of the volume bodies and output to a digital transducer, A thermal displacement correction method for a machine tool in which a column thermal displacement amount is calculated from an environmental component due to a temperature difference between both temperature sensors, and the thermal displacement is corrected using a correction amount obtained by multiplying the column thermal displacement amount by a correction multiplier. (2) A volume body with a large heat capacity and a volume body with a small heat capacity are each placed on a column that is susceptible to environmental temperature changes, and a temperature sensor is placed in each of the volume bodies to output to a digital transducer, and The amount of column thermal displacement is calculated from the environmental component due to the difference in temperature between both temperature sensors, and temperature sensors are placed on the spindle head and the bed, which is less susceptible to environmental temperature changes, and output to a digital transducer. Calculate the spindle thermal displacement amount from the spindle heat generation component due to temperature, and calculate the thermal displacement by the total correction amount obtained by adding each correction amount obtained by multiplying the above column thermal displacement amount and spindle displacement amount by the correction multiplier. Thermal displacement correction method of the machine tool to be corrected.