JP2013206119A - Machine tool environment and tool state diagnostic method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable the diagnosis of a machine tool environment and a tool state at low cost and without requiring special equipment.SOLUTION: A machining center 1 diagnoses environment and a tool state by respectively estimating the present ambient temperatures on the basis of detection temperatures obtained from respective temperature sensors ch1 to ch7 and comparing a difference between the present ambient temperatures estimated in at least two temperature sensors with a preset threshold.

Description

  The present invention relates to a method for diagnosing the environment and machine state of a machine tool.

  When machining with a machine tool, the structure temperature changes due to changes in room temperature or the influence of cutting fluid, resulting in machining dimension errors. In order to suppress this dimensional error, a method of estimating and correcting thermal displacement by using a conversion coefficient or the like from room temperature or a structure temperature detected by a temperature sensor installed in each part of the machine is well known. . In addition, a method of installing a machine tool in a temperature-controlled room such as a temperature-controlled room, or providing a temperature adjusting means (cooling pipe) in the vicinity of the temperature sensor as disclosed in Patent Document 1 to suppress temperature changes. Is also known.

JP 2001-54839 A

However, in the method of correcting by estimating the thermal displacement, the room temperature around each structure is not uniform due to the influence of the cover and axial movement, etc. In addition, the measured value is also an instantaneous value, so it tends to vary, and thermal displacement estimation It is a factor of error. Also, when the room temperature does not change uniformly due to the influence of instability factors such as cooling, heating, and sunlight, or when the thermal conductivity of a part of the structure changes due to the flow of wind even if the ambient temperature changes are the same In this case, a temperature distribution is generated in the structure. This temperature distribution causes thermal deformation such as warpage and torsion, apart from simple thermal expansion and contraction due to temperature change, leading to instability of processing dimensions. Furthermore, if the room temperature has changed before the start of use of the machine tool, the structure temperature will change and thermal displacement will occur even if the ambient temperature does not change. Similarly, an estimation error may occur in the diagnosis.
On the other hand, regarding the installation in a temperature-controlled room or the like and the addition of the cooling pipe to the structure as in Patent Document 1, it is obvious that the influence of the disturbance as described above is reduced but the cost is increased.
Therefore, as a premise for carrying out a method for estimating and correcting thermal displacement, it has been desired to provide a method for diagnosing the surrounding environment and state of a machine without much cost.

  Therefore, an object of the present invention is to provide a machine tool environment and machine state diagnosis method capable of diagnosing the surrounding environment and machine state at low cost without requiring special equipment.

In order to achieve the above object, according to the first aspect of the present invention, a plurality of temperature sensors are installed in each part of the structure, and the environment and machine state of the machine tool are determined from the temperature of each part of the structure detected by the temperature sensor. A method for diagnosing, wherein a current room temperature is estimated based on a detected temperature obtained from each temperature sensor, and a difference between the current room temperatures estimated in at least two temperature sensors is preset. It is characterized by comparing with a threshold value.
In order to achieve the above object, according to the second aspect of the present invention, a plurality of temperature sensors are installed in each part of the structure, and the environment and machine state of the machine tool are determined from the temperature of each part of the structure detected by the temperature sensor. A method for diagnosing, wherein an estimated temperature change of the structure is calculated from a preset time constant of each part of the structure and a change in room temperature, an allowable range is set for the calculated estimated temperature change, and the temperature sensor It is determined whether or not the temperature change of each part of the structure detected in (1) is within the allowable range of the estimated temperature change.
According to a third aspect of the present invention, in the configuration of the second aspect, the permissible range is set from an average of estimated temperature changes of two temperature sensors that are provided in the structure and are paired, and the two temperature sensors It is determined whether or not the temperature change detected in (1) is within the allowable range.
In order to achieve the above object, according to a fourth aspect of the present invention, a plurality of temperature sensors are installed in each part of the structure, and the environment and machine state of the machine tool are determined from the temperature of each part of the structure detected by the temperature sensor. A diagnostic method is characterized in that it is determined whether or not a change in temperature difference between two paired temperature sensors provided in the structure is within a preset threshold value. .
In order to achieve the above object, the invention according to claim 5 executes the diagnostic method according to claim 3 and the diagnostic method according to claim 4, respectively. When it is determined that a temperature change detected by two temperature sensors is not within the allowable range, and a change in temperature difference between the two temperature sensors is determined not to be within the threshold in the diagnosis method according to claim 4. The environment and the machine state are diagnosed as unstable.
In order to achieve the above object, according to the present invention, a plurality of temperature sensors are installed in each part of the structure, and the environment and machine state of the machine tool are determined from the temperature of each part of the structure detected by the temperature sensor. A method for diagnosing, which calculates an estimated temperature change of the structure from a preset time constant of each part of the structure and a change in room temperature, and also provides the pair of temperature sensors provided in the structure to form a pair. 5. A diagnostic method for setting an allowable range from an average of estimated temperature changes and determining whether a temperature difference between the two temperature sensors is within the allowable range and a diagnostic method according to claim 4 are executed. In the former diagnosis method, it is determined that the temperature difference between the two temperature sensors is not within the allowable range, and in the diagnosis method according to claim 4, the change in the temperature difference between the two temperature sensors is not within the threshold value. When If it is the cross-sectional, and is characterized in that the diagnosing unstable the environmental and mechanical conditions.
The invention according to claim 7 is characterized in that, in the configuration according to any one of claims 2 to 6, when the environment and the machine state are diagnosed as unstable as a result of the determination, the temperature sensor according to the determination is displayed. It is what.

According to the present invention, it is possible to inexpensively diagnose a machine state as to whether a machine has a stable thermal displacement without requiring special equipment. In addition, the surrounding environment of the machine before the start of use can be diagnosed from the temperature change of each structure.
In particular, according to the fifth and sixth aspects of the invention, in addition to the above effects, two diagnostic methods are executed and diagnosed step by step, so unnecessary interruption of processing can be avoided.
Further, according to the seventh aspect of the invention, in addition to the above effect, it is possible to know the location where the temperature change is large, which is a clue for improving the surrounding environment (air conditioning direction, sunlight, etc.).

It is explanatory drawing of the machining center of form 1. 6 is a flowchart of the diagnosis method of the first embodiment. It is a graph which shows the room temperature of form 1, and the temperature change of a structure. It is a graph which shows the room temperature of form 1, and the temperature change of a structure. It is a table | surface which shows the estimated room temperature of form 1. It is a flowchart of the diagnostic method of form 2. It is a graph which shows the room temperature change of form 2, an estimated temperature change, and its allowable range. It is a graph which shows the room temperature change of form 3, an estimated temperature change, and its allowable range. It is a graph which shows the room temperature change of form 4, a threshold value, and the change of a temperature difference.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[Form 1]
FIG. 1 is an explanatory diagram of a machining center which is an example of a machine tool. In the machining center 1, a table 3 on which a workpiece is placed and a column 4 are installed on a bed 2, and a spindle head 5 having a spindle 6 is provided in the column 4. Each of these structures is provided with temperature sensors ch1 to ch7. Among them, the temperature sensor ch1 is provided on the spindle 6, the temperature sensor ch2 is provided on the spindle head 5, and the temperature sensor ch3 is provided on the table 3, while the temperature sensors ch4 and ch5 are divided on the upper and lower sides of the table 3, respectively. Are provided separately before and after the column 4, respectively.

  Further, the machining center 1 includes a temperature measuring device 10 that converts analog signals output from the temperature sensors ch1 to ch7 into digital signals and digitizes them, and a temperature time constant of a structure set in advance from the digitized measured values. The temperature estimation device 11 that estimates the room temperature using the temperature, the change of the estimated room temperature and the temperature measurement measured by the temperature measurement device 10 are compared, the diagnosis device 12 that diagnoses the surrounding environment, and the periphery based on the diagnosis result An NC device 13 for notifying the operator of the environment and stopping the machining center 1 based on the diagnosis result is provided.

In the machining center 1 configured as described above, as shown in FIG. 2, after the temperature of each structure is measured by the temperature measurement device 10 (S1), the temperature estimation device 11 estimates the room temperature around the temperature sensor (S2). ) The diagnosis device 12 repeats the process of diagnosing the environment and the machine state (S3) at predetermined intervals (until NO in S4).
Hereinafter, room temperature estimation processing in the temperature estimation device 11 will be described.

In FIG. 3, a straight line A is a model assuming a room temperature at which the temperature T changes stepwise at time t 2 _O , and a curve a is a temperature of the structure whose temperature changes with a time constant that changes with room temperature. Here, assuming that the environmental diagnosis is started by turning on the power of the machine after time t ₁ from the room temperature change, the temperature at that time is T ₁ , and the temperature at the first environmental diagnosis cycle t ₂ is T ₂ . The current temperature T ₂ of the structure can be obtained by the following equation (1), where ΔT is a temperature difference from room temperature and k is a coefficient that takes into account the temperature time constant of each structure relative to the temperature difference from room temperature. it can.
T ₂ = ΔT × k + T ₁ (1)
Thus, the estimated room temperature Te can be obtained by calculating the temperature difference ΔT.

  Similarly, by estimating the room temperature from each temperature sensor and comparing the estimated room temperature of at least two (preferably three or more) temperature sensors in the vicinity of the surrounding environment, it is 1 when a wind such as heating is directly applied. When one temperature sensor has an estimated room temperature different from the others, the operator can be notified of an environmental abnormality.

Next, a specific diagnosis example will be described with reference to FIGS.
In FIG. 4, A ′ is a change in room temperature around a certain structure, a ′ to c ′ are structure temperatures measured at the same position in the environment, and FIG. 5 is a change in room temperature assuming power-on for 3 hours. Each structure temperature T ₁ after, temperature T ₂ after 30 minutes, and estimated room temperature at that time. That is, if the machine is turned on 3 hours after the start of the room temperature change and the environmental diagnosis is performed 3.5 hours later, the temperature difference ΔT with respect to the current room temperature is calculated by using Equation (1) from T ₁ and T _2. By calculating, an estimated room temperature from each structure can be obtained.

  And the difference of each estimated room temperature obtained is calculated, and the difference of each estimated room temperature calculated is compared with the preset threshold value. For example, if the threshold value of the estimated room temperature difference is 0.5 ° C., the estimated room temperature differences in FIG. 5 are all equal to or less than the threshold value, and therefore the surrounding environment of the compared structures is determined to be stable. . On the other hand, if the difference in estimated room temperature exceeds the threshold, it is possible to specify a local environmental change, for example, a heating wind directly hitting a structure having a higher estimated room temperature. In this case, the NC device 13 displays the comparison result and notifies the operator, and the processing is interrupted.

  As described above, according to the diagnosis method of the environment and the machine state of the machining center 1 according to the first aspect, the current room temperature is estimated based on the detected temperature obtained from each temperature sensor, and is estimated by at least two temperature sensors. By comparing the difference between the current room temperature and a preset threshold value, it is possible to inexpensively diagnose the machine state of whether the machine has a stable thermal displacement without requiring special equipment. . In addition, the surrounding environment of the machine before the start of use can be diagnosed from the temperature change of each structure.

Next, another embodiment of the present invention will be described. However, since the configuration of the machining center 1 is the same as that of the first embodiment, only different portions will be described and redundant description will be omitted.
[Form 2]
In the second embodiment, the temperature estimation device 11 of the machining center 1 estimates a temperature change using a temperature time constant of a structure set in advance from a measurement value digitized by the temperature measurement device 10. Hereinafter, a specific diagnosis method of the environment and the machine state in the second embodiment will be described by taking the temperature obtained from the temperature sensors ch6 and ch7 arranged before and after the column 4 as an example.

First, the temperature time constant of each structure is set in advance by preliminary tests or analysis where there is no influence of disturbance such as in a temperature test chamber.
Then, as shown in FIG. 6, after measuring the temperature of each part of the machine in S11, in S12, the temperature change of each part is estimated from the room temperature, and the allowable range of the estimated temperature change is calculated. Next, the diagnosis device 12 repeats the process of diagnosing the environment and machine state (S13) at predetermined intervals (until NO in S14).
Hereinafter, estimation of temperature change and setting of an allowable range in the temperature estimation device 11 will be described.

  In FIG. 7, a is a model that assumes a change in room temperature, b is an estimated temperature change calculated from the change in room temperature and the temperature time constant of the structure, and b1 and b2 are set in consideration of the effect on thermal displacement. The upper permissible range and the lower permissible range of the estimated temperature change b, and c shown by the curve are measured temperature changes of the structure measured by the temperature sensor ch6.

The estimated temperature change b obtained here is obtained by the following equation (2), where the temperature time constant of the temperature sensor ch6 is τ1, the measurement interval is t, the measurement room temperature is T, and the previous measurement temperature is T _n−1. be able to.
Estimated temperature change b = T _n−1 + (T−T _n−1 ) × t ₁ / (t 1 + τ 1) (2)
The allowable ranges b1 and b2 are set by multiplying the estimated temperature change b by a preset coefficient. For example, if the upper allowable range is 1.2 times and the lower allowable range is 0.8 times, the allowable ranges are determined by the following equations (3) and (4), respectively.
Allowable range b1 = b × 1.2 (3)
Allowable range b2 = b × 0.8 (4)

Next, diagnosis of the environment around the machine and the machine state in the diagnosis device 12 will be described.
In this diagnosis, for example, it is determined whether or not the measured temperature change c is in the allowable range above and below the estimated temperature change b depending on whether both of the following expressions (5) and (6) are satisfied. That is, when both are satisfied as shown in FIG. 7, it is determined to be stable because it is within the allowable range, and when neither is satisfied, it is determined to be unstable and the operator is notified and the machining is interrupted. .
b1-c ≧ 0 (5)
c−b2 ≧ 0 (6)

  As described above, also in the diagnosis method of the environment and the machine state of the machining center 1 according to the second aspect, the estimated temperature change of the structure is calculated from the preset time constant of each part of the structure and the room temperature change. Special equipment is required by setting an allowable range for the estimated temperature change and judging whether the temperature change of each part of the structure detected by the temperature sensor is within the allowable range for the estimated temperature change. Therefore, it is possible to inexpensively diagnose the machine state as to whether the machine has a stable thermal displacement. In addition, the surrounding environment of the machine before the start of use can be diagnosed from the temperature change of each structure.

[Form 3]
In the second aspect, a method is used for obtaining and diagnosing an estimated temperature change for one temperature sensor, but here, a method for obtaining and diagnosing an estimated temperature change for two paired temperature sensors will be described.
In FIG. 8, a shown by a straight line is a model assuming a change in room temperature, d1 and d2 are an upper allowable range obtained from an average value d of estimated temperature changes of the temperature sensors ch6 and ch7 calculated in Equation (2), and a lower limit. The allowable range on the side, c indicated by a curve, is the temperature change on the front side of the column, and e is the temperature change on the rear side of the column.

  Here, the machine state is determined based on whether or not the measured temperature changes c and e are within the allowable range. As shown in FIG. 8, since both the measured temperature changes c and e change within the allowable range of the estimated temperature change, it can be determined that the temperature change before and after the column is stable.

As described above, in the method for diagnosing the environment and the machine state of the machining center 1 according to the third aspect as well, the machine state can be diagnosed at a low cost as to whether the machine has a stable thermal displacement without requiring special equipment. It becomes. In addition, the surrounding environment of the machine before the start of use can be diagnosed from the temperature change of each structure.
In particular, here, it is diagnosed whether the surrounding environment of the position that affects the tilt or warpage of the structure is within the expected range by determining whether the measured temperature at the paired position is within the allowable range. can do.

[Form 4]
FIG. 9 shows a threshold value for the change in temperature difference before and after the column in consideration of the influence on the thermal displacement, and the change in the temperature difference f before and after the column measured by the temperature sensors ch6 and ch7 with respect to the model a assuming a change in room temperature. Represents. Here, the change in temperature difference can be calculated by the following equation (7), where Tf1 and Tr1 are the temperatures before and after the column at the start, and Tf2 and Tr2 are the temperatures before and after the column at the time of measurement, respectively.
Change in temperature difference = (Tr2−Tf2) − (Tr1−Tf1) (7)

It is determined whether or not the obtained change in temperature difference is within a threshold value. In FIG. 9, since the change of the temperature difference is within the threshold value, it can be determined as stable.
As described above, in the method for diagnosing the environment and the machine state of the machining center 1 according to the fourth embodiment, it is possible to inexpensively diagnose the machine state as to whether the machine has a stable thermal displacement without requiring special equipment. It becomes. In addition, the surrounding environment of the machine before the start of use can be diagnosed from the temperature change of each structure.

In each of the above embodiments, the diagnosis of the environment and the machine state is performed independently. However, the final diagnosis of the environment and the machine state may be performed by executing each embodiment in parallel. For example, the diagnosis methods of modes 3 and 4 are executed, respectively, and if all are determined to be stable as shown in Table 1 below, the final diagnosis is stable (determination A), and if any one of the temperature changes is unstable For example, it is considered that the final diagnosis needs attention (determination B), and if the temperature change is unstable in any case, the final diagnosis is unstable (determination C). In this case, the diagnosis result is notified to the operator, and in the case of determination C, the processing is interrupted.
If it is determined that attention is required, there may be no problem even if the processing is continued. For example, if form 3 is outside the allowable range and form 4 is within the allowable range, the temperature difference before and after the structure is small, but the temperature change is larger than the estimated value. Although there is a possibility that the balance between the front and rear is lost or the thermal displacement with time is increased, it is possible to continue the machining if the workpiece has a short machining time or a workpiece with low required accuracy.
If form 3 is within the allowable range and form 4 is outside the allowable range, the structure is tilted, but the thermal displacement is within the estimated range. However, in drilling with a drill, it is necessary to interrupt the processing because the hole may become elliptical or cause tool breakage.
In this way, depending on the required processing conditions, there are cases where the processing may be continued or bad, so that the material determined by the operator from the displayed diagnosis result, or the processing is interrupted in the case of a predetermined determination. By doing so, unnecessary processing interruptions can be avoided.

  In the third aspect, the machine state is determined based on whether the measured temperature change is within the allowable range. However, the machine state is determined based on whether the temperature difference between the two temperature sensors is within the allowable range. The state may be determined. Also in this case, the diagnosis is executed together with the diagnosis method of Form 4, and if any of them is determined to be stable, the final diagnosis is stable. If any one of the temperature changes is unstable, the final diagnosis is required. However, if the temperature change is unstable, a stepwise diagnostic method that makes the final diagnosis unstable can be adopted.

Further, in each embodiment, when it is determined that the state is unstable, a temperature sensor according to the determination may be displayed to notify the operator. If the temperature sensor diagnosed in this way is displayed, the location where the temperature change is large can be known, which is a clue for improving the surrounding environment (air conditioning direction, sunlight, etc.).
In the above embodiment, the column front-rear temperatures ch6 and ch7 are taken as an example, but the same diagnosis can be made with temperature sensors at other positions such as the bed vertical temperature ch4 and ch5.

  1 .. Machining center 2. Bed 3. Table 4 Column 5 Head spindle 6 Spindle ch1 to ch7 Temperature sensor

Claims (7)

A method of diagnosing the environment and machine state of a machine tool from the temperature of each part of the structure detected by the temperature sensor by installing a plurality of temperature sensors in each part of the structure,
A current room temperature is estimated based on a detected temperature obtained from each of the temperature sensors, and a difference between the current room temperatures estimated in at least two of the temperature sensors is compared with a preset threshold value. The machine tool environment and machine state diagnosis method. A method of diagnosing the environment and machine state of a machine tool from the temperature of each part of the structure detected by the temperature sensor by installing a plurality of temperature sensors in each part of the structure,
The estimated temperature change of the structure is calculated from the time constant and room temperature change of each part of the structure set in advance, and an allowable range is set for the calculated estimated temperature change, and the structure detected by the temperature sensor A method for diagnosing the environment and machine state of a machine tool, wherein it is determined whether or not a temperature change of each part is within the allowable range of the estimated temperature change.   The allowable range is set from an average of estimated temperature changes of two temperature sensors that are provided in the structure and are paired, and whether or not the temperature change detected by the two temperature sensors is within the allowable range. 3. The machine tool environment and machine state diagnosis method according to claim 2, wherein the determination is made. A method of diagnosing the environment and machine state of a machine tool from the temperature of each part of the structure detected by the temperature sensor by installing a plurality of temperature sensors in each part of the structure,
A method for diagnosing the environment and machine state of a machine tool, characterized in that it is determined whether or not a change in temperature difference between two paired temperature sensors provided in the structure is within a preset threshold value. .   The diagnostic method according to claim 3 and the diagnostic method according to claim 4 are respectively executed, and it is determined in the diagnostic method according to claim 3 that the temperature change detected by the two temperature sensors is not within the allowable range. When the change in temperature difference between the two temperature sensors is determined not to be within the threshold in the diagnosis method according to claim 4, the environment and the machine state are diagnosed as unstable. Diagnosis method for machine tool environment and machine condition. A method of diagnosing the environment and machine state of a machine tool from the temperature of each part of the structure detected by the temperature sensor by installing a plurality of temperature sensors in each part of the structure, and a time constant of each part of the structure set in advance An estimated temperature change of the structure is calculated from the room temperature change, and an allowable range is set based on an average of the estimated temperature changes of the two temperature sensors provided in the structure as a pair, and the two temperature sensors A diagnostic method for determining whether the temperature difference is within the allowable range;
5. The diagnostic method according to claim 4 is respectively executed, and in the former diagnostic method, it is determined that a temperature difference between the two temperature sensors is not within the allowable range, and in the diagnostic method according to claim 4, the two temperatures are determined. A diagnosis method for an environment and a machine state of a machine tool, wherein the environment and the machine state are diagnosed as unstable when it is determined that a change in temperature difference between sensors is not within the threshold value.   If the environment and the machine state are diagnosed as unstable as a result of the determination, the temperature sensor related to the determination is displayed. The environment and machine state of the machine tool according to any one of claims 2 to 6, Diagnosis method.

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