阅读说明：本技术 数值控制装置 (Numerical controller ) 是由 黑原靖之 于 2019-07-17 设计创作，主要内容包括：本发明提供一种数值控制装置,其在工件上加工已决定了加工位置以及加工形状的多个加工孔,数值控制装置具备：热影响计算部,其针对各个加工孔求出以加工位置以及加工形状加工了加工孔时的工件的热分布的时间变化；加工位置决定部,其根据加工了之前的加工孔后直到加工下一个加工孔为止的经过时间、加工了之前的加工孔以及下一个加工孔时的热分布来决定工件不产生热变形的下一个加工孔；以及加工部,其加工加工孔。上述数值控制装置能够考虑热变形来决定加工位置。(The present invention provides a numerical controller for machining a plurality of machining holes in which machining positions and machining shapes are determined in a workpiece, the numerical controller including: a heat influence calculation unit that obtains, for each of the machined holes, a temporal change in a heat distribution of the workpiece when the machined hole is machined at the machining position and in the machining shape; a machining position determination unit that determines a next machined hole in which thermal deformation of the workpiece does not occur, based on an elapsed time from machining of the previous machined hole to machining of the next machined hole and a thermal distribution at the time of machining of the previous machined hole and the next machined hole; and a processing portion for processing a hole. The numerical controller can determine the machining position in consideration of the thermal deformation.)

1. A numerical controller for machining a plurality of machining holes in a workpiece, the machining positions and the machining shapes of which are determined,

the numerical controller includes:

a heat influence calculation unit that obtains, for each of the machined holes, a temporal change in a heat distribution of the workpiece when the machined hole is machined at the machining position and in the machining shape;

a machining position determination unit that determines a next machined hole in which thermal deformation of the workpiece does not occur, based on an elapsed time from machining of the previous machined hole to machining of the next machined hole, and a thermal distribution at the time of machining of the previous machined hole and the next machined hole; and

and a processing portion for processing the processing hole.

2. The numerical control apparatus according to claim 1,

the machining position determining unit determines, as the next machined hole, an unprocessed machined hole that is located closest to the previous machined hole and in which thermal deformation of the workpiece does not occur.

3. The numerical control apparatus according to claim 2,

the machining position determining unit divides the workpiece into a plurality of regions, determines the next machined hole in the same region as the previous machined hole, and determines the next machined hole in another region when machining of all the machined holes in the region is completed.

4. The numerical control apparatus according to claim 1,

the machining position determining unit determines the machining order of the machining holes so that the workpiece does not thermally deform and a path for the plurality of machining holes to travel is shortest.

5. The numerical control apparatus according to claim 1,

the heat-affected calculating unit obtains, for each of the machined holes, a temporal change in a range in which a temperature of the workpiece becomes Tt/2 when the machined hole is machined at the machining position and in the machining shape,

the machining position determination unit determines that the workpiece has thermal deformation when the range generated by machining of the previous machined hole overlaps the range generated by machining of the next machined hole,

the temperature Tt is a temperature at which the workpiece can be thermally deformed.

6. The numerical control apparatus according to claim 1,

the heat-affected calculating unit calculates a temporal change in temperature of the workpiece when the machining hole is machined at the machining position and the machining shape at a plurality of measurement points or in a small area provided in the workpiece,

the machining position determining unit determines that the workpiece has thermal deformation when a total value of heat generated by machining of a previous machined hole and heat generated by machining of a next machined hole exceeds Tr at any one of the measurement point and the small area,

the temperature Tt is a temperature at which the workpiece can be thermally deformed.

7. The numerical control apparatus according to claim 1,

the heat influence calculation unit successively obtains the heat distribution by an approximation calculation method including a finite element method.

8. The numerical control apparatus according to claim 1,

the heat influence calculation unit obtains the heat distribution by referring to a data set including a predicted value of the heat distribution, which is obtained by an approximation calculation method including a finite element method.

9. The numerical control apparatus according to claim 1,

the heat influence calculation unit obtains the heat distribution by referring to a data set including an actual measurement value of the heat distribution at the time of sampling processing.

10. The numerical control apparatus according to claim 1,

the machining unit generates a machining program for machining the machining holes in the order determined by the machining position determining unit.

Technical Field

The present invention relates to a numerical controller, and more particularly to a numerical controller for determining a machining position in consideration of thermal deformation.

Background

There is known a processing machine (hereinafter simply referred to as a processing machine or a machine) such as a punch press or a laser processing machine that performs a drilling process on a workpiece. When these machines drill holes, the temperature of the workpiece rises. In particular, as shown in fig. 1, if drilling is continuously performed in a relatively close range, the workpiece may be thermally deformed, and the machining accuracy may be lowered. Conventionally, an operator manually determines a machining procedure (see fig. 2) and creates a machining program (hereinafter simply referred to as a program) in consideration of the possibility of such thermal deformation.

In addition, several methods for automatically determining the drilling process sequence in consideration of preventing thermal deformation have been proposed. Japanese patent application laid-open No. 8-99252 discloses the following: in order to prevent the problem of thermal deformation due to the concentration of frictional heat in one region by drilling, drilling is performed at an unprocessed position farthest from the position immediately before the processing. Japanese patent No. 5162977 describes the following: in order to prevent heat accumulation, the machining region is divided into a plurality of divided regions, and machining is performed in the order of discontinuously machining adjacent divided regions. Japanese patent No. 5889606 describes the following: the distance at which the machining accuracy of the next machined hole is reduced due to the thermal influence of the immediately preceding machined hole is determined as a threshold value LM, and the machining order is arranged by using a local search method such as a 2-opt method so that the distance between the machined holes is equal to or greater than the threshold value LM and the machining path is the shortest.

The conventional method for determining a machining sequence by manual operation has the following problems: the operator takes much time to create a program in consideration of the thermal influence, and the production efficiency is impaired. In particular, when machining holes of different shapes are mixed, calculation for determining the machining order becomes complicated, and the order cannot be easily determined. In this case, since the machining order is currently determined depending on machining experience or the like, it is difficult for an operator with little experience to create a machining program.

Further, the methods described in japanese patent laid-open No. 8-99252 and japanese patent No. 5162977 are limited to automating a part of the conventional rule of thumb. In this method, the machining position is not determined by evaluating the thermal influence based on accurate data such as a predicted value, and therefore, thermal deformation may occur in some cases. The method described in japanese patent No. 5889606 is based on the premise that the shape of the machined hole is the same, because only the distance between the machined holes is considered. That is, it cannot cope with any shape of the machined hole.

Disclosure of Invention

The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a numerical controller for determining a machining position in consideration of thermal deformation.

A numerical controller according to an aspect of the present invention is a numerical controller for machining a plurality of machining holes in which machining positions and machining shapes are determined in a workpiece, the numerical controller including: a heat influence calculation unit that obtains, for each of the machined holes, a temporal change in a heat distribution of the workpiece when the machined hole is machined at the machining position and in the machining shape; a machining position determination unit that determines a next machined hole in which thermal deformation of the workpiece does not occur, based on an elapsed time from machining of the previous machined hole to machining of the next machined hole, and a thermal distribution at the time of machining of the previous machined hole and the next machined hole; and a processing portion for processing the processing hole.

In the numerical controller according to one aspect of the present invention, the machining position determining unit determines the next machined hole as the unmachined machined hole which is located at the nearest position to the previous machined hole and in which no thermal deformation of the workpiece occurs.

In the numerical controller according to one aspect of the present invention, the machining position determining unit divides the workpiece into a plurality of regions, determines the next machined hole in the same region as the previous machined hole, and determines the next machined hole in another region when machining of all the machined holes in the region is completed.

In the numerical controller according to one aspect of the present invention, the machining position determining unit determines the machining order of the machining holes so that the workpiece does not thermally deform and the path around the plurality of machining holes is the shortest.

In the numerical controller according to one aspect of the present invention, the heat-affected calculating unit obtains, for each of the machining holes, a temporal change in a range in which a temperature of the workpiece becomes Tt/2 when the machining hole is machined at the machining position and the machining shape, and the machining position determining unit determines that the workpiece is thermally deformed when the range generated by the previous machining of the machining hole overlaps the range generated by the next machining of the machining hole, and the temperature Tt is a temperature at which the workpiece can be thermally deformed.

In the numerical controller according to one aspect of the present invention, the heat-affected calculating unit obtains a temporal change in the workpiece temperature when the machined hole is machined at the machining position and the machined shape at a plurality of measurement points or in a small area provided in the workpiece, and the machining position determining unit determines that the workpiece is thermally deformed when a total value of heat generated by machining of a previous machined hole and heat generated by machining of a next machined hole at any one of the measurement points or in the small area exceeds Tr, where the temperature Tt is a temperature at which the workpiece can be thermally deformed.

In the numerical controller according to one aspect of the present invention, the thermal influence calculation unit obtains the thermal distribution by an approximate calculation method including a finite element method.

In the numerical controller according to one aspect of the present invention, the heat influence calculation unit obtains the heat distribution using a data set obtained by measuring the heat distribution at the time of sampling.

In the numerical controller according to one aspect of the present invention, the machining unit generates a machining program for machining the machined holes in accordance with the order determined by the machining position determining unit.

According to the present invention, it is possible to provide a numerical controller that determines a machining position in consideration of thermal deformation.

Drawings

The above and other objects and features of the present invention will become apparent from the following description of the embodiments with reference to the accompanying drawings. In these drawings:

fig. 1 illustrates the problem of drilling.

Fig. 2 illustrates the problem of drilling.

Fig. 3 shows an example of the maximum range of the machining hole and the thermal influence.

Fig. 4 shows the time variation of the maximum range of the thermal influence.

Fig. 5 shows an example of the finite element method heat distribution calculation.

Fig. 6 shows an example of a method for determining a machining position according to embodiment 1.

Fig. 7 shows an example of a method for determining a machining position according to embodiment 1.

Fig. 8 shows an example of a method for determining a machining position according to embodiment 1.

Fig. 9 shows an example of a method for determining a machining position according to embodiment 1.

Fig. 10 shows an example of a method for determining a machining position according to embodiment 1.

Fig. 11 is a flowchart showing an example of the operation of the numerical controller 1 according to embodiment 1.

Fig. 12 shows an example of a method for determining a machining position according to embodiment 2.

Fig. 13 shows an example of a method for determining a machining position according to embodiment 2.

Fig. 14 shows an example of a method for determining a machining position according to embodiment 3.

Fig. 15 shows an example of a hardware configuration of the numerical controller.

Fig. 16 shows an example of a functional configuration of the numerical controller.

Fig. 17 shows an example of the heat distribution of the workpiece by the drilling process.

Fig. 18 shows an example of the heat distribution of the workpiece by the drilling process.

Detailed Description

< embodiment 1>

The numerical controller 1 according to embodiment 1 of the present invention determines a machining position (a position of a machining hole) that is not affected by heat, in consideration of the thermal conductivity of the workpiece. In addition, the processing order that is not affected by heat can be determined. Further, a machining program for performing machining without being affected by heat can be automatically generated.

Fig. 15 is a schematic hardware configuration diagram showing a main part of the numerical controller 1. The numerical controller 1 is a device for controlling a machining machine. The numerical controller 1 includes a CPU11, a ROM12, a RAM13, a nonvolatile memory 14, an interface 18, a bus 10, a shaft control circuit 16, and a servo amplifier 17. The numerical controller 1 is connected to a servo motor 50 and an input/output device 60.

The CPU11 is a processor that controls the numerical controller 1 as a whole. The CPU11 reads out a system program stored in the ROM12 via the bus 10, and controls the entire numerical controller 1 in accordance with the system program.

The ROM12 stores in advance system programs for executing various controls of the processing machine.

The RAM13 temporarily stores temporary calculation data and display data, data and programs input by an operator via the input/output device 60 described later, and the like.

The nonvolatile memory 14 is supported by, for example, a battery not shown, and maintains a storage state even when the power supply of the numerical controller 1 is turned off. The nonvolatile memory 14 stores data, programs, and the like input from the input/output device 60. Programs and data stored in the non-volatile memory 14 may be deployed when executed and used within the RAM 13.

The axis control circuit 16 controls the operation axis of the processing machine. The axis control circuit 16 receives the amount of the axis movement command output from the CPU11, and outputs the axis movement command to the servo amplifier 17.

The servo amplifier 17 receives the shaft movement command output from the shaft control circuit 16 and drives the servo motor 50.

The servo motor 50 is driven by the servo amplifier 17 to move the operation axis of the processing machine. The servo motor 50 typically has a position velocity detector built therein. The position/velocity detector outputs a position/velocity feedback signal, which is fed back to the shaft control circuit 16, thereby performing feedback control of the position/velocity.

In fig. 15, only one shaft control circuit 16, one servo amplifier 17, and one servo motor 50 are shown, but in practice, the number of shafts provided in the processing machine (not shown) to be controlled is prepared in accordance with the number of shafts. For example, when controlling a processing machine having 3 axes, a total of 3 sets of the axis control circuit 16, the servo amplifier 17, and the servo motor 50 corresponding to each axis are prepared.

The input/output device 60 is a data input/output device provided with a display, hardware keys, and the like, and is typically an operation panel. The input/output device 60 displays information received from the CPU11 via the interface 18 on a display. The input/output device 60 delivers commands, data, and the like input from hardware keys and the like to the CPU11 via the interface 18. The input/output device 60 can display a program stored in the nonvolatile memory 14 on the display, for example, and can perform editing by hardware keys.

Fig. 16 is a block diagram showing a schematic functional configuration of the control device 1. The numerical controller 1 includes a thermal influence calculation unit 101, a machining position determination unit 102, and a machining unit 103.

The heat influence calculation unit 101 calculates the distribution of heat generated during machining for each of the machining holes described in the machining program. Here, each of the machining holes has a machining position (e.g., the center of the machining hole) and a machining shape (the shape of the machining hole). That is, the shape of each machined hole may be different in the present embodiment.

Fig. 17 and 18 show an example of the heat distribution (temperature distribution) of the workpiece by the drilling process. The broken line indicates the machined shape. The closed graph of the solid line is an isotherm obtained by connecting points having equal temperatures, and indicates that the isotherm located on the inner side has a higher temperature. Fig. 17 shows the heat distribution when a round hole is formed by a punch press. The heat is distributed concentrically with the center (machining position) of the circular hole as the center. Fig. 18 shows the heat distribution when the corner hole is laser-processed. Unlike the case of the circular hole, there is a distorted (non-uniform) heat distribution in which heat concentrates at the corner.

The heat influence calculation unit 101 can calculate the maximum range of the heat influence for each machined hole. The maximum range of the thermal influence is a range in which heat generated during drilling propagates to such an extent that the thermal influence affects the machining accuracy of the next machined hole. In the present embodiment, Tt is the lower limit of the temperature at which thermal deformation of the workpiece can occur (i.e., the temperature at which thermal deformation starts to occur), and Tt is the maximum range of the thermal influence, which is the range where the temperature of the workpiece passing through the machining is equal to or higher than Tt/2 degrees. Fig. 3 shows an example of the maximum range of the machining hole and the thermal influence. This indicates that the maximum range of the thermal influence is different depending on the shape of the machined hole.

The heat generated by the machining propagates to a certain range within the workpiece almost instantaneously immediately after the machining, but is gradually dissipated as time passes, so that the heat distribution changes with time so that the range surrounded by the isotherm is narrowed. As shown in fig. 5, the maximum range of the thermal influence of the workpiece after machining becomes maximum immediately after machining, and the heat dissipation decreases with time. That is, the maximum range of the thermal influence is narrowed as the moving time passes while the tool is fast-forwarded to the next machining position after machining. In other words, the maximum extent of the thermal distribution or thermal influence of the machined workpiece is expressed as a function of time.

The method of calculating the heat distribution of the heat-affected computation unit 101 is shown in 4 examples.

Calculation method of Heat distribution (1)

The heat-affected calculating unit 101 can calculate the heat distribution when each machined hole is machined, sequentially, for example, by using a known calculation method that can calculate the heat distribution, as represented by a finite element method. At this time, various constants, intrinsic values, and the like necessary for calculation are acquired or determined in advance and stored in a predetermined storage area.

The finite element method is a discretization method for approximately solving a phenomenon described by a differential equation or a partial differential equation which is difficult to solve analytically. An object having a complicated shape or property is divided into simple small regions (see fig. 4), and the behavior is calculated for each small region, thereby predicting the overall behavior.

The thermal influence calculation unit 101 combines the following thermal conduction equation with a finite element method, for example. I.e. the process is repeated. A heat conduction equation is calculated for each small region, thereby determining the temperature of each small region and the heat distribution across the workpiece at a time.

[ numerical formula 1]

Cv: product of specific heat and density (J/m)³)

T: temperature (K)

t: time (sec)

λ: thermal conductivity (J/(m sec K))

q (t): heat per unit time and unit volume (laser irradiation heat, frictional heat of press, etc.) (J/sec. m)³)

Here, Cv and λ are constants different depending on the workpiece material, and q (t) is a value specific to the laser oscillator and the like. The heat-affected calculation unit 101 performs this calculation in each small region, and thereby can obtain the workpiece temperature at the elapsed time t from the start of machining in each small region.

Calculation method of Heat distribution (2)

The heat influence calculation unit 101 can determine the maximum range of the heat influence by summarizing a small region (or a representative point thereof) in which the workpiece temperature is not less than Tt/2 over the elapsed time t in the method (1) for calculating the heat distribution. By using the maximum range of the thermal influence, whether the machining position is appropriate or not can be determined at high speed with less calculation resources, as will be described later.

Calculation method of Heat distribution (3)

According to the above-described method (1) of calculating the heat distribution, the heat distribution in an arbitrary workpiece shape, workpiece material, machining shape, and the like can be calculated, but considerable calculation resources are required. In the method (2) for calculating the heat distribution, the heat influence calculation unit 101 accumulates the calculation result obtained by the method (1) for calculating the heat distribution in the database. More specifically, for example, the workpiece temperature of the elapsed time t from the start of machining in each small region is stored in the database for each constant such as the workpiece shape, the machining shape, and Cv, λ, q (t).

Next and thereafter, when machining is performed again under the same conditions, the heat-affected-area calculating unit 101 can obtain the workpiece temperature of the elapsed time t from the start of machining for each small area by referring to the database. The heat-influence calculation unit 101 can determine the maximum range of the heat influence by summing up small regions (or representative points thereof) in which the workpiece temperature of the elapsed time t is not less than Tt/2.

Calculation method of Heat distribution (4)

The heat-influence calculation unit 101 actually performs sampling processing, and refers to the result of measuring the temperature of the workpiece using a temperature measurement means such as a temperature graph (thermal), thereby specifying the heat distribution when each processed hole is processed. For example, the temperature of a workpiece drilled in a certain machining shape is measured at a plurality of measurement points for each predetermined time period, and the measurement results are stored in a database, a numerical expression, or the like. More specifically, for example, the distance from the machining position, the elapsed time from the start of machining, and the workpiece temperature are stored in the database in association with each constant such as the workpiece shape, the machining shape, and Cv, λ, q (t).

The heat-influence calculation unit 101 can obtain the workpiece temperature at each measurement point for the elapsed time t from the start of machining by referring to the database. The thermal influence calculation unit 101 can determine the maximum range of the thermal influence (a closed graph indicating the outer edge of the maximum range) by connecting the measurement points at which the workpiece temperature at the elapsed time t is Tt/2.

The machining position determination unit 102 determines the next machining position based on the heat distribution or the maximum range of the thermal influence calculated by the thermal influence calculation unit 101 and the moving time to the next machining position. The movement time is an elapsed time from when the machining of the machined hole was performed at the previous machining position to when the machining of the machined hole was started at the next machining position.

Method for determining machining position (1)

The machining position determination unit 102 can search for the nearest unmachined position that is not affected by the heat generated in the previous machining, using the maximum range of thermal influence obtained by the above-described method (2) for calculating the heat distribution. In the method, the machining position is determined to be appropriate or not using geometrical information such as the maximum range of the thermal influence. This method is simpler in calculation than the machining position determining methods (2) to (4) described later, and can determine the machining position at high speed with less calculation resources.

Step 1: the moving time t from the last machining position to the unmachined position P is calculated. That is, it is assumed that machining is performed at the unmachined position P after the moving time t has elapsed from the previous machining position. The initial value of the unprocessed position P is set to the unprocessed position closest to the last processed position.

Step 2: the maximum range a1(t) of the thermal influence of the previous machining after the moving time t has elapsed since the previous machining is obtained by the method (2) of calculating the thermal distribution.

And step 3: the maximum range a2(t) of the thermal influence immediately after the machining, which is caused by the machining at the unmachined position P at the time point when the moving time t has elapsed, is obtained by the method (2) of calculating the thermal distribution.

And 4, step 4: it is determined whether a1(t) and a2(t) interfere, i.e., at least partially overlap. If there is interference, the process proceeds to step 6. In this case, since the workpiece temperature is not lower than Tt, the unprocessed position P is not suitable as the next processing position (thermal deformation may occur). If there is no interference (see fig. 6), the process proceeds to step 5.

And 5: the unprocessed position P is determined as the next processed position.

Step 6: the unprocessed position P is updated with an unprocessed position next to the last processed position of the unprocessed position P, and the calculation of step 1 and thereafter is repeated.

Method for determining machining position (2)

The machining position determining unit 102 can search for the nearest unmachined position that is not affected by the heat generated in the previous machining, using the heat distribution calculated by the heat distribution calculation method (1). The unprocessed position can be searched for more finely than in the above-described method (1) for determining a processed position.

Step 1: the moving time t from the last machining position to the unmachined position P is calculated. That is, it is assumed that machining is performed at the unmachined position P after the moving time t has elapsed from the previous machining position. The initial value of the unprocessed position P is set to the unprocessed position closest to the last processed position.

Step 2: the heat distribution of the workpiece after the lapse of the moving time t from the previous machining is obtained by the heat distribution calculation method (1). Specifically, the temperatures of the workpieces in a plurality of small regions set on the workpiece after the moving time t has elapsed since the previous machining are obtained.

And step 3: the thermal distribution immediately after machining at the unprocessed position P at the time point when the moving time t has elapsed is obtained by the thermal distribution calculation method (1). Specifically, the temperatures of the workpieces in a plurality of small regions set on the workpiece immediately after the machining at the unmachined position P are obtained.

And 4, step 4: at each measurement point on the workpiece, the temperature obtained in step 1 (the temperature of the previous machining) and the temperature obtained in step 2 (the temperature of the machining at the unmachined position P) are summed up, and it is determined whether or not there is a small region where the total temperature is Tt or more. If so, transfer to step 6. At this time, since the workpiece temperature is at least Tt, the unprocessed position P is not suitable as the next processed position (thermal deformation may occur). In the absence, it is transferred to step 5.

And 5: the unprocessed position P is determined as the next processed position.

Step 6: the unprocessed position P is updated with an unprocessed position next to the last processed position of the unprocessed position P, and the calculation of step 1 and thereafter is repeated.

Method for determining machining position (3)

The machining position determining unit 102 can search for the nearest unmachined position that is not affected by the heat generated in the previous machining, using the heat distribution predicted and accumulated by the above-described heat distribution calculation method (3). That is, the temperature distribution calculated under the similar conditions is reused, thereby making it possible to secure the accuracy close to the machining position determining method (2) and reduce the amount of calculation.

Step 1: the moving time t from the last machining position to the unmachined position P is calculated. That is, it is assumed that machining is performed at the unmachined position P after the moving time t has elapsed from the previous machining position. The initial value of the unprocessed position P is set to the unprocessed position closest to the last processed position.

Step 2: the heat distribution of the workpiece after the lapse of the moving time t from the previous machining is obtained by the heat distribution calculation method (3). Specifically, the temperatures of the workpiece at a plurality of measurement points set on the workpiece after the travel time t has elapsed since the previous machining are obtained.

And step 3: the thermal distribution immediately after machining at the unprocessed position P at the time point when the moving time t has elapsed is obtained by the thermal distribution calculation method (3). Specifically, the temperatures of the workpiece at a plurality of measurement points set on the workpiece immediately after the machining at the unmachined position P are obtained.

And 4, step 4: at each measurement point on the workpiece, the temperature obtained in step 1 (the temperature of the previous machining) and the temperature obtained in step 2 (the temperature of the machining at the unmachined position P) are summed up, and it is determined whether or not there is a measurement point at which the total temperature is Tt or more. If so, transfer to step 6. At this time, since the workpiece temperature is at least Tt, the unprocessed position P is not suitable as the next processed position (thermal deformation may occur). In the absence, it is transferred to step 5.

And 5: the unprocessed position P is determined as the next processed position.

Step 6: the unprocessed position P is updated with an unprocessed position next to the last processed position of the unprocessed position P, and the calculation of step 1 and thereafter is repeated.

Method for determining machining position (4)

The machining position determining unit 102 can search for the nearest unmachined position that is not affected by the heat generated in the previous machining, using the heat distribution actually measured and accumulated by the above-described heat distribution calculating method (4). That is, by reusing the temperature distribution actually measured under similar conditions, it is possible to ensure the accuracy close to the machining position determining methods (2) and (3) described above and to eliminate the amount of calculation required for predicting the value calculation.

Step 1: the moving time t from the last machining position to the unmachined position P is calculated. That is, it is assumed that machining is performed at the unmachined position P after the moving time t has elapsed from the previous machining position. The initial value of the unprocessed position P is set to the unprocessed position closest to the last processed position.

Step 2: the heat distribution of the workpiece after the lapse of the moving time t from the previous machining is obtained by the heat distribution calculation method (4). Specifically, the temperatures of the workpiece at a plurality of measurement points set on the workpiece after the travel time t has elapsed since the previous machining are obtained.

And step 3: the thermal distribution immediately after machining at the unprocessed position P at the time point when the moving time t has elapsed is obtained by the thermal distribution calculation method (4). Specifically, the temperatures of the workpiece at a plurality of measurement points set on the workpiece immediately after the machining at the unmachined position P are obtained.

And 4, step 4: at each measurement point on the workpiece, the temperature obtained in step 1 (the temperature of the previous machining) and the temperature obtained in step 2 (the temperature of the machining at the unmachined position P) are summed up, and it is determined whether or not there is a measurement point at which the total temperature is Tt or more. If so, transfer to step 6. At this time, since the workpiece temperature is at least Tt, the unprocessed position P is not suitable as the next processed position (thermal deformation may occur). In the absence, it is transferred to step 5.

And 5: the unprocessed position P is determined as the next processed position.

Step 6: the unprocessed position P is updated with an unprocessed position next to the last processed position of the unprocessed position P, and the calculation of step 1 and thereafter is repeated.

If the next machining position is determined by the machining position determining unit 102, the machining unit 103 performs drilling at the machining position.

An operation example of the numerical controller 1 will be described with reference to the flowchart of fig. 11 and fig. 7 to 10. The process numbers described below correspond to the flowchart of fig. 11.

S1: the thermal influence calculation unit 101 reads a machining program, and acquires machining positions and machining shapes of all the machined holes. The heat distribution at the time of machining is calculated or acquired for all the machined holes by using the above-described heat distribution calculation method (1) or (2). The heat influence calculation unit 101 may calculate the maximum range of the heat influence.

S2: the machining position determination unit 102 arbitrarily determines the first machining position (see fig. 7). The first machining position is typically specified by the user. The machining unit 103 performs drilling at the determined first machining position.

S3: the machining position determining unit 102 selects the unmachined position P closest to the first machining position.

S4: the machining position determination unit 102 determines whether or not thermal deformation is likely to occur when machining is performed at the unmachined position P in the order of steps 2 to 4 in any of the machining position determination methods (1) to (3). The process proceeds to step S7 when thermal deformation occurs. When the thermal deformation is not generated, the process proceeds to step S5.

Fig. 8 and 9 are schematic diagrams showing an example of processing in which the machining position determination unit 102 determines whether there is thermal deformation according to the machining position determination method (1) after the first machining. The machining position determination unit 102 determines that thermal deformation has occurred when the maximum range of the thermal influence caused by the first machining interferes with the maximum range of the thermal influence caused when machining is performed at the unprocessed position P. Fig. 8 shows an example of the disturbance that is determined to have the largest thermal influence at the unprocessed position P closest to the first processed position. Fig. 9 shows an example in which it is determined that no disturbance occurs at the unprocessed position P that is second closest to the first processed position.

Fig. 10 is a schematic diagram showing an example of processing in which the machining position determination unit 102 determines whether there is thermal deformation according to the machining position determination method (1) after the second machining at the machining position. The machining position determination unit 102 determines that thermal deformation has occurred when the maximum range of the thermal influence caused by the second machining interferes with the maximum range of the thermal influence caused when the machining is performed at the unprocessed position P. In the example of fig. 10, it is determined that the disturbance having the largest thermal influence occurs at the unprocessed position P closest to the second processed position.

S5: the machining unit 103 performs drilling at the unprocessed position P determined in S4.

S6: if an additional unprocessed position remains, the process proceeds to S7. If no unprocessed positions remain, the process proceeds to S8.

S7: when the processing shifts from S4, the unprocessed position next to the current unprocessed position P and closer to the previous processed position is selected as a new unprocessed position P, and the processing shifts again to S4.

When the processing shifts from S6, the unprocessed position closest to the current unprocessed position P (i.e., the processing position in S5) is selected as the new unprocessed position P, and the processing shifts to S4.

S8: and finishing the processing.

According to the present embodiment, if the machining program is registered in the numerical controller 1, the numerical controller 1 can perform the drilling process in the optimum machining order in consideration of the thermal deformation. This can greatly reduce the time it takes for the operator to create the machining program in consideration of the thermal deformation. Further, even an operator with little experience can perform drilling processing in consideration of thermal deformation. Therefore, the efficiency and productivity of the work can be improved.

< embodiment 2>

If the machining positions where thermal deformation does not occur are sequentially determined in the order shown in the flowchart of fig. 11 using the numerical controller 1 of embodiment 1, a predetermined machining order is formed (see fig. 12). If the machining is advanced in this machining order, a plurality of unprocessed positions distant from each other may remain in some cases, resulting in a problem in machining efficiency. In embodiment 2, such a problem is solved to improve the processing efficiency.