KR101787347B1 - Control method of numerical control machine tool - Google Patents

Abstract

A method of controlling a machine tool based on a real-time corrected reference cutting load of the present invention includes deriving a reference cutting load according to a tool type, information on a workpiece, a machining path and a feed rate, An actual cutting load measuring step of measuring the cutting load inputted to the cutting tool, a step of judging the damage of the tool in comparison with the reference cutting load and the actual cutting load, and a step of judging the damage of the tool, And controlling the operation of the machine tool in accordance with an increase or decrease in error occurring when the cutting load and the actual cutting load are compared. The step of determining the damage of the tool includes a step of determining, based on the reference cutting load, To determine the damage of the tool.

Description

Technical Field [0001] The present invention relates to a control method of a machine tool based on a reference cutting load,

The present invention relates to a method of controlling a machine tool by monitoring a tool damage of a numerically controlled machine tool, and more particularly, to a method of controlling a machine tool by detecting a tool damage based on a reference cutting load corrected in real time, To a method for controlling the operation of the apparatus.

In performing a machining operation through a numerical control machine tool, commonly referred to as an NC machine tool, the tool and the workpiece are rotated or transported in a firmly fixed state.

The numerical control device instructs the machine tool to operate in accordance with the target value, compares the target value with the detected value, and corrects the operation automatically when the target value is different from the target value.

When the tool is operated and the tool and the work are in contact with each other to perform machining, when the tool is worn or damaged, a large machining error is generated from the target value for machining.

Failure to appropriately control the operation of the machine tool in the event of abrasion or breakage of the tool can result in damage to the workpiece or lead to malfunction of the machine tool. Various monitoring methods for tool wear or breakage and control of the machine tool .

Korean Patent Application No. 1997-0033320, entitled " Quill Control Method in Automatic Depressor ", monitors the pressure conditions supplied to a quill through a solenoid valve in an automatic tailstock of a numerical control lathe, And stopping the rotation.

However, there is a disadvantage in that it can not grasp the damage of the tool related to the technology for controlling the operation of the machine tool by detecting the support state of the workpiece, and it can not grasp the state of various tools and the workpiece because it detects only the pressure drop state .

Alternatively, when chattering, which is the phenomenon of the tool shaking in the machine tool, is measured and the tool is out of the steady-state input value, methods of checking the tool by reducing the chattering or stopping the operation are performed However, it is difficult to control the machine tool by detecting the abrasion or damage directly caused by the tool due to the error.

Therefore, a method for solving such problems is required.

SUMMARY OF THE INVENTION The present invention is conceived to solve the problems of the prior art described above, and it is an object of the present invention to provide a method of accurately determining a damage of a tool by correcting a cutting load of an arithmetically calculated tool by substituting a feed rate measured in real time Accordingly, the present invention is intended to provide a method for controlling a machine tool by monitoring not only the value of the cutting load measured through the tool, but also the increase / decrease and the increase / decrease width thereof.

The problems of the present invention are not limited to the above-mentioned problems, and other problems not mentioned can be clearly understood by those skilled in the art from the following description.

In order to achieve the above object, a method of controlling a machine tool based on a real-time corrected reference cutting load of the present invention includes deriving a reference cutting load according to a tool type, information on a workpiece, a machining path and a feed rate, The actual cutting load measurement step of measuring the cutting load inputted to the tool during the machining of the workpiece, the step of judging the damage of the tool in comparison with the reference cutting load and the actual cutting load, and the step of determining the damage of the tool, And controlling the operation of the machine tool in accordance with an increase or decrease in an error occurring in comparing the reference cutting load and the actual cutting load, wherein the step of determining the damage of the tool includes determining a normal Determine damage to the tool by dividing it into zones, breakage zones, and wear zones.

The step of deriving the reference cutting load includes a step of calculating an arithmetic cutting load in consideration of the type of tool, the information of the workpiece, the machining path and the feed speed, the step of inputting the machining path and the feed speed into the machine tool, Deriving a measured conveying speed actually measured, and correcting the arithmetic cutting load in real time through the measured conveying speed.

Or, the normal zone is determined as the section within the tolerance range based on the reference cutting load including the reference cutting load, the failure zone is determined as the lower load zone than the normal zone, and the wear zone is determined as the overload zone rather than the normal zone.

And, the step of controlling the operation of the machine tool stops the operation of the machine when the actual cutting load belongs to the damaged area or the wear area and lasts for a predetermined time.

Alternatively, the step of controlling the operation of the machine tool permits the operation of the machine tool when the actual cutting load belongs to a breakage zone or a wear zone and the error produced when contrasting the reference cutting load and the actual cutting load decreases.

In the step of controlling the operation of the machine tool, the operation of the machine tool is stopped when the increase / decrease width of error occurring when comparing the reference cutting load and the actual cutting load is equal to or larger than a predetermined value.

In order to solve the above problems, a method of controlling a machine tool based on a real-time corrected reference cutting load of the present invention corrects an arithmetically calculated cutting load by reflecting a feed rate measured from an actual machine tool in real time, And the error range between the actual cutting load and the reference cutting load is increased or decreased not only in the value of the actual cutting load but also in the case of comparing the actual cutting load measured in the machining of the workpiece with the reference cutting load, The damage of the tool is determined by reflecting the increase / decrease width, and the unnecessary operation interruption of the machine tool is reduced by controlling the machine tool according to the result.

The effects of the present invention are not limited to the effects mentioned above, and other effects not mentioned can be clearly understood by those skilled in the art from the description of the claims.

1 is a perspective view showing a simplified machine tool.
2 is a flowchart illustrating a method of controlling a machine tool according to an exemplary embodiment of the present invention.
3 is a flowchart illustrating a step of calculating a reference cutting load in a method of controlling a machine tool according to an embodiment of the present invention.
4 is a graph illustrating a reference cutting load of a method of controlling a machine tool according to an embodiment of the present invention.
5 is a graph showing a criterion for determining a tool damage in a method of controlling a machine tool according to an embodiment of the present invention.
FIG. 6 is a graph showing control of a machine tool in a state where an actual cutting load is out of a normal region in a method of controlling the machine tool according to an embodiment of the present invention.
FIG. 7 is a graph illustrating a state in which a machine tool is controlled according to an abrupt increase or decrease in an actual cutting load in a method of controlling a machine tool according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. In describing the present embodiment, the same designations and the same reference numerals are used for the same components, and further description thereof will be omitted.

The method of controlling a machine tool according to the present invention can be implemented as follows.

FIG. 1 is a simplified perspective view of a machine tool, and FIG. 2 is a flowchart illustrating a method of controlling a machine tool according to an embodiment of the present invention.

1 and 2, a method of controlling a machine tool according to an embodiment of the present invention is a method for calculating a reference cutting load according to a kind of a tool 10, information on the work 20, a machining path, An actual cutting load measurement step S200 for measuring a cutting load inputted to the tool 10 when the workpiece 20 is machined through the machine tool, a step (S200) for comparing the reference cutting load with the actual cutting load, The damage judgment result of the tool 10 derived through the step S300 of judging the damage of the tool 10 and the result of judging whether the reference cutting load and the actual cutting load are generated (S400) of controlling the operation of the machine tool in accordance with an increase or decrease in error, and the step of determining damage (S300) of the tool (10) is divided into a normal region, a damaged region, and a wear region Thereby judging the damage of the tool 10.

Each of the above steps will be described in detail below.

FIG. 3 is a flowchart illustrating a step of calculating a reference cutting load in a method of controlling a machine tool according to an embodiment of the present invention. FIG. 4 is a flowchart illustrating a method of controlling a reference cutting load in a method of controlling a machine tool according to an embodiment of the present invention. FIG. 5 is a graph showing a criterion for judging tool damage in a control method of a machine tool according to an embodiment of the present invention.

Referring to FIGS. 3 to 5, step S100 of deriving the reference cutting load is as follows.

First, an arithmetic cutting load for deriving a cutting load to be applied to the tool 10 arithmetically is calculated using the information such as the tool 10 used for machining and the material of the workpiece, the machining path, Is performed.

The feed rate is the speed at which the workpiece 20 is processed in contact with the tool 10 and transported.

In order to obtain the cutting load applied to the tool 10 when the specific workpiece 20 is arithmetically worked through the machine tool, it is necessary to determine the cutting load applied to the tool 10 even if the preceding machining information can not be obtained And to control the machine tool through damage monitoring.

The arithmetic cutting load is calculated as a variable of the kind of the tool, the material of the workpiece, the amount of cutting according to the working diameter, and the feeding speed, and can be calculated as a first data set that is schematized.

This is illustrative and the first data set may be arithmetically derived using a variety of variables in accordance with an embodiment to which the invention is applied.

In order to perform the machining by inputting the machining path and the feed rate, which were used as variables in deriving the arithmetic cutting load, to the numerically controlled machine tool, the measured feed rate, which is the output value of the input target value and the actually outputted feed rate, A step of deriving a measurement transfer speed for obtaining a second data set that is set is performed.

Since the arithmetic cutting load is an arithmetically derived cutting load with the feed rate used as the target value as a variable, there is an error as much as the difference between the target value and the output value generated through the numerically controlled machine tool.

Therefore, in order to reduce this error, the arithmetic cutting load is corrected in real time based on the second data set.

Specifically, a reference cutting load is calculated (S100) through a step of real-time correction of a first data set, which is a pre-computed arithmetic cutting load, with a second data set, which is a measurement feed rate output in real time.

The reason why the reference cutting load is derived by correcting the first data set through the second data set in real time is to derive a proper cutting load value inputted to the tool 10 in real time at the time of machining a small amount of workpiece.

The actual cutting load measurement step S200 is a step of measuring the actual cutting load, which is a cutting load that is machined through the numerical control machine tool and input to the tool 10, and directly measures the cutting load directly inputted to the tool 10 And can be measured through a torque sensor or a current sensor which is applied to the tool 10.

Step S300 of judging the damage of the tool is a step of judging wear or breakage of the tool 10 in comparison with the actual cutting load measured in real time by performing the reference cutting load and machining derived in the process described above.

As shown in FIGS. 4 and 5, the allowable tolerance of the reference cutting load is determined by using the reference cutting load as a reference value to determine whether the tool is damaged.

The allowable tolerance of the reference cutting load is derived by multiplying the tolerance upper limit value and the tolerance lower limit correction factor B and the reference cutting load derived by multiplying the tolerance upper limit correction factor T and the reference cutting load as shown in FIG. The lower limit of tolerance, and this interval is defined as the normal zone.

When abrasion or foreign matter adheres to the tool 10, the cutting load inputted to the tool 10 becomes large, so the section exceeding the normal region is defined as a wear region.

In the case where at least a part of the tool 10 is lost due to breakage of the tool 10, the cutting load inputted to the tool 10 is abruptly closed, so the section under the normal section is defined as the breakage area.

Therefore, when the value of the actual cutting load belongs to the normal region, it can be recognized that the tool 10 is not damaged. If the value of the actual cutting load belongs to the wear region exceeding the normal region, It is judged that abrasion has occurred. If it is judged that the actual cutting load value belongs to the breakage section which is less than the normal section, it is judged that the tool 10 is broken.

In operation S400 of controlling the operation of the machine tool, if the actual cutting load belongs to the normal region through the step S300 of determining the damage of the tool, the controller controls the machine tool to be operated according to the inputted information, When it is judged that the wear of the tool 10 has occurred and when it is judged that the tool 10 is broken, the operation of the machine tool is stopped.

The process of stopping the operation of the machine tool can be implemented as in the following embodiments.

FIG. 6 is a graph showing control of a machine tool in a state where an actual cutting load deviates from a normal region in a method of controlling the machine tool according to an embodiment of the present invention. FIG. 7 is a graph showing the control of the machine tool according to an embodiment of the present invention FIG. 2 is a graph showing a state in which the machine tool is controlled according to a sharp increase or decrease in the actual cutting load in the method of FIG.

6, when the value of the actual cutting load measured in real time enters the damaged area or the wear area and the tool 10 is determined to be worn or damaged, the tool 10 is judged to be worn or damaged The operation of the machine tool may be stopped when the determination of the wear or breakage is maintained even after the lapse of the delay time by keeping the predetermined delay time without interrupting the operation of the machine tool.

And, if the value of the actual cutting load belongs to the damaged area or the wear area but the error value with respect to the reference cutting load is in a decreasing trend, it can be set to suspend the interruption of the machine tool.

Even if it is determined that the tool 10 is worn or damaged through the step S300 of determining the damage of the tool, the actual cutting load increases or decreases due to various factors that may occur in performing the machining, It is to cope when it can be returned to the area.

It is also intended to avoid controlling the machine tool to be interrupted in the process of returning to the normal region while the actual cutting load is temporarily attributed to the wear region or the damaged region, but the factor that influenced the actual cutting load is removed.

As shown in FIG. 7, it is possible to control the operation of the machine tool to be stopped when the increase / decrease width of the error generated in comparison with the reference cutting load and the actual cutting load abruptly changes.

This is to protect the workpiece and the machine tool by stopping the operation of the machine tool if the amount of change exceeding the increase / decrease width of the predetermined error is measured due to the sudden breakage of the tool even if the actual cutting load belongs to the normal region.

It will be apparent to those skilled in the art that the present invention can be embodied in other specific forms without departing from the spirit or scope of the invention as defined in the appended claims. It is obvious to them. Therefore, the above-described embodiments are to be considered as illustrative rather than restrictive, and the present invention is not limited to the above description, but may be modified within the scope of the appended claims and equivalents thereof.

10: Tools
20: Workpiece
30: Tool stand
T: Tolerance upper limit correction factor
B: Tolerance lower limit correction factor

Claims (6)

A control method for a numerically controlled machine tool,
Deriving a reference cutting load according to a tool type, information on a workpiece, a machining path, and a feed rate;
An actual cutting load measuring step of measuring a cutting load input to the tool when the workpiece is machined through the machine tool;
Determining a damage of the tool in comparison with the reference cutting load and the actual cutting load; And
And controlling the operation of the machine tool according to an increase or decrease in an error occurring when the reference cutting load is compared with the actual cutting load, and a damage determination result of the tool derived through the step of determining the damage of the tool ,
Wherein deriving the reference cutting load comprises:
Calculating an arithmetic cutting load in consideration of the tool type, the information on the workpiece, the machining path, and the feedrate;
Inputting the machining path and the feed rate to the machine tool to derive a measured feed rate actually measured when the workpiece is machined; And
And correcting the arithmetic cutting load in real time through the measurement transfer rate,
The step of judging damage of the tool may be divided into a normal zone, a damaged zone, and a wear zone based on the reference cutting load,
Wherein said normal zone is determined as a section within a tolerance range based on said reference cutting load including said reference cutting load, said failure zone being determined to be a lower load zone than said normal zone, said wear zone being overloaded Wherein the step of controlling the operation of the machine tool stops the operation of the machine when the actual cutting load belongs to the breakage area or the wear area and lasts for a predetermined time, A control method of a machine tool based on a real time corrected reference cutting load that permits operation of the machine tool when an error generated when the reference cutting load and the actual cutting load are included in the broken area or the abrasion area decreases .
delete delete delete delete The method according to claim 1,
Wherein controlling the operation of the machine tool comprises:
Wherein the reference cutting load and the actual cutting load are compared with each other, and the reference cutting load and the actual cutting load are compared with each other.

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