US 5,444,640 A · Numerical control method for controlling various kinds of machine tools by correcting for thermal displacement

Abstract

A numerical control method for controlling various kinds of machine tools by correcting for thermal displacement. Data relative to thermal displacement, thermal displacement sampling time, and processing cycle time is stored in memory. Before each process, the shift of an absolute position of a machine origin is measured to provide an initial value. The machine tool is energized and thermal displacement data is gathered according to a sampling time. The sampling time is varied according to the degree of thermal displacement. Processing is performed on the data to correct for the thermal displacement of the machine tool.

Claims29

Dependent claims

A numerical control method for controlling a numerical control (NC) machine having an electrical power source for providing power to operate said numerical control machine, a tool means comprising a machine tool and a drive means for effecting the machining of a workpiece, a measuring means for measuring machine tool position, a memory means for storing data including at least previous-time thermal displacement data and this-time thermal displacement data, and a processing means, said processing means being operative by periodic processing to execute a processing program, comprising the steps of:

turning on said electrical power source;
storing a thermal-displacement sampling time (Tt) and a processing cycle time (Tc), in said memory means;
selecting a measurement reference position to serve as a machine origin;
storing data identifying said machine origin with said memory means;
measuring the shift of an absolute position of said machine origin as a measurement reference position before every processing, so that said shift of said absolute position serves as an initial value;
collecting data of an amount of heat generated thermal displacement of said drive means for a duration of said stored thermal-displacement sampling time and storing said displacement data in said memory means as this-time data;
upon reaching said stored thermal displacement sampling time, concurrently (i) executing adaptation processing which changes the sampling time of the thermal displacement of said drive means, depending upon whether or not the thermal displacement of said drive means is within a range of an allowable error within said processing cycle time, and (ii) comparison computation processing of the amount of thermal displacement;
comparing said thermal displacement of said drive means and a minimum movement setting unit with each other to determine whether or not said thermal displacement is within a first allowable error;
executing a correction of said thermal displacement if said displacement is not within said first allowable error;
rewriting said previous-time thermal-displacement data as this-time data after correction of the thermal displacement;
and
executing thermal-displacement correction for said drive means.

9 more elements

A numerical control method for controlling a numerical control (NC) machine having an electrical power source for providing power to operate said numerical control machine, a tool means comprising a machine tool and a drive means for effecting the machining of a workpiece, a measuring means for measuring said machine tool position, a memory means for storing data including at least previous-time thermal displacement data and this-time thermal displacement data, and a processing means, said processing means being operative by periodic processing to execute a processing program, comprising the steps of:

turning on said electrical power source;
selecting a measurement reference position to serve as a workpiece reference position;
storing at least data of a machine origin and said workpiece reference position in said memory means;
executing zero-point correction of said measuring means;
measuring said workpiece reference position with said measuring means when said electric power source is turned on;
bringing correction values entirely to zero with a value of the measurement by said measuring means serving as an initial value;
measuring the shift of an absolute position of the workpiece reference position every processing cycle;
correcting for thermal displacement, comprising correction processing of the workpiece reference position, during possible interruptions of said program;
storing a thermal-displacement sampling time (Tt) and a processing cycle time (Tc), in said memory means;
following said turning-on of said electric power source, collecting data of an amount of heat generated thermal displacement of said drive means for a duration of said stored thermal-displacement sampling time and storing said displacement data in said memory means as this-time data;
upon reaching said stored thermal displacement sampling time, concurrently executing (i) adaptation processing in which the thermal-displacement sampling time of said drive means is changed, depending upon whether or not the thermal displacement of said drive means is within a range of a first allowable error within a processing cycle time, and (ii) comparison computation processing of the amount of thermal displacement;
and
executing correction of the thermal displacement of said drive means on the basis of a comparison of the thermal displacement error and a minimum movement setting unit with each other.

10 more elements

A numerical control method for controlling a numerical control (NC) machine having an electrical power source for providing power to operate said numerical control machine, a tool means comprising a machine tool and a drive means for effecting the machining of a workpiece, a measuring means for measuring said machine tool position, a memory means for storing data including at least previous-time thermal displacement data and this-time thermal displacement data, and a processing means, said processing means being operative by periodic processing to execute a processing program, comprising the steps of:

turning on said electrical power source;
selecting a measurement reference position to serve as a workpiece reference position;
storing at least data of a machine origin and said workpiece reference position in said memory means;
executing zero-point correction of said measuring means;
measuring said workpiece reference position with said measuring means when said electric power source is turned on;
bringing correction values entirely to zero with a value of the measurement by said measuring means serving as an initial value;
measuring the shift of an absolute position of the workpiece reference position every processing cycle;
correcting for thermal displacement, comprising correction processing of the workpiece reference position, during possible interruptions of said program;
storing the measurement sampling time (Tp) of an allowable value of a position error (D) for a machine position and a moving position in said memory means;
initializing automatic correction after measurement of a workpiece reference position;
counting the measurement sampling time of the machine position and the moving position;
upon reaching said value Tp, executing adaptation processing which changes the measurement sampling time of the machine position and the moving position if said counted sampling time is not within said time (Tp) of an allowable position error;
repeating said counting and adaptation processing of the measurement sampling time of the machine position and the moving position until an electric power source is turned off, regardless of a main processing;
executing the correction of the workpiece reference position such that the measured error and a second allowable error value per time are compared with each other to decide whether or not the workpiece reference position is required to be measured and corrected;
executing prediction of the displacement of the workpiece reference position (MwtTcf) on the basis of the following equation:
MwtTcf={.vertline.(previous time measurement)=(this time measurement.vertline./(Tp)P}.multidot.k{Tc-(processing running time until now)}P
where P is a power exponent representing heat generation with respect to heat emission;
and where k is a machining constant;
comparing a prediction value of the displacement of the workpiece reference position with a measured value until the difference is within a third allowable error;
executing at least one of a warning during the automatic operation, automatic judgment on interruption of machine halt, and machine halt on the basis of the results in which the prediction value of the displacement of the workpiece reference position and said third allowable error are compared with each other.

17 more elements

A numerical control method for controlling a numerical control (NC) machine having an electrical power source for providing power to operate said numerical control machine, a tool means and a drive means for effecting the machining of a workpiece, a measuring means for measuring machine tool position, a memory means for storing data including at least previous-time thermal displacement data and this-time thermal displacement data, and a processing means, said processing means being operative by periodic processing to execute a processing program, comprising the steps of:

turning on said electrical power source;
selecting a measurement reference position to serve as a workpiece-mounting reference-block position;
storing at least data of a machine origin and said workpiece reference position in said memory means;
executing zero-point correction of said measuring means;
measuring said workpiece-mounting reference-block position with said measuring means when said electric power source is turned on;
bringing correction values entirely to zero with a value of the measurement by said measuring means serving as an initial value;
measuring the shift of an absolute position of the workpiece-mounting reference-block position every processing cycle;
correcting for thermal displacement, comprising correction processing of the workpiece-mounting reference-block position, during possible interruptions of said program;
storing a thermal-displacement sampling time (Tt) and a processing cycle time (Tc), in said memory means;
following said turning-on of said electric power source, collecting data of an amount of heat generated thermal displacement of said drive means for a duration of said stored thermal-displacement sampling time and storing said displacement data in said memory means as this-time data;
upon reaching said stored thermal displacement sampling time, concurrently executing (i) adaptation processing in which the thermal-displacement sampling time of said drive means is changed, depending upon whether or not the thermal displacement of said drive means is within a range of a first allowable error within a processing cycle time, and (ii) comparison computation processing of the amount of thermal displacement;
executing correction of the thermal displacement of said drive means on the basis of a comparison of the thermal displacement error and a minimum movement setting unit with each other.

9 more elements

A numerical control method for controlling a numerical control (NC) machine having an electrical power source for providing power to operate said numerical control machine, a tool means and a drive means for effecting the machining of a workpiece, a measuring means for measuring machine tool position, a memory means for storing data including at least previous-time thermal displacement data and this-time thermal displacement data, and a processing means, said processing means being operative by periodic processing to execute a processing program, comprising the steps of:

turning on said electrical power source;
selecting a measurement reference position to serve as a workpiece-mounting reference-block position;
storing at least data of a machine origin and said workpiece reference position in said memory means;
executing zero-point correction of said measuring means;
measuring said workpiece-mounting reference-block position with said measuring means when said electric power source is turned on;
bringing correction values entirely to zero with a value of the measurement by said measuring means serving as an initial value;
measuring the shift of an absolute position of the workpiece-mounting reference-block position every processing cycle;
correcting for thermal displacement, comprising correction processing of the workpiece-mounting reference-block position, during possible interruptions of said program;
storing the measurement sampling time (Tp) of an allowable value of a position error (D) for a machine position and a moving position in said memory means;
initializing automatic correction after measurement of a workpiece-mounting reference-block position;
counting the measurement sampling time of the machine position and the moving position;
upon reaching said stored value Tp, executing adaptation processing which changes the measurement sampling time of the machine position and the moving position if said counted sampling time is not within said time (Tp) of an allowable position error, said adaptation processing being conducted repeatedly until said electric power source is turned off, regardless of a main processing;
executing the correction of the workpiece-mounting reference-block position such that the measured error and a first allowable error value per time are compared with each other to decide whether or not the workpiece-mounting reference-block position is required to be measured and corrected;
executing prediction of the displacement of the workpiece-mounting reference-block position (MwbtTcf) on the basis of the following equation:
MwbtTcf={.vertline.(previous time measurement)-(the time measurement).vertline./(Tp)P}.multidot.k{Tc-(processing running time until now)}P
where P is a power exponent representing heat generating with respect to heat emission;
and where k is a machining constant;
comparing a prediction value of the displacement of the workpiece-mounting reference-block position with a measured value until the difference is within a second allowable error;
executing at least one of a warning during the automatic operation, automatic judgment on interruption of machine halt, and machine halt on the basis of the results in which the prediction value of the displacement of the workpiece-mounting reference-block position and the allowable error are compared with each other.

16 more elements

A numerical control method for controlling a numerical control (NC) machining having an electrical power source for providing power to operate said numerical control machine, a tool means and a drive means for effecting the machining a workpiece, a measuring means for measuring machine tool position, an electric power source for providing power to operate said machine, a memory means for storing data including at least previous-time thermal displacement data, this-time thermal displacement data and correction values, and a processing means, said processing means being operative by periodic processing to execute a processing program, comprising the step of:

turning on said electrical power source;
storing a machine origin, a specific moving position, an allowable value of position errors, each of a plurality of thermal-displacement data, a plurality of sampling time data, and processing cycle time, in memory means;
thereupon, (i) collecting data defining an amount of heat generated thermal displacement of said drive means, (ii) counting of a sampling time of thermal displacement, and (iii) measuring the machine position, comprising one of the machine origin, the workpiece reference position, and the workpiece-mounting reference-block position;
executing adaptation processing in which the thermal-displacement sampling time of said drive means is changed, depending upon whether the thermal displacement is within a range of a first allowable error within a processing cycle time;
after measurement of said machine position, which is used as a reference position, initializing an automatic correction;
counting the measurement sampling time of the machine position and the moving position;
upon counting to a stored measurement sampling time Tp, concurrently (i) executing adaptation processing of measurement sampling time of the machine position and the moving position, (ii) executing computation processing of the displacement of the moving position and (iii) executing computation of the thermal displacement of the machine origin;
on the basis of said corresponding execution step, deciding whether or not measurement and correction of the moving position and machine position are required;
if correction of moving position is required, executing prediction of displacement of the moving position (MmtTcf) on the basis of the following equation:
MmtTcf={.vertline.(previous time measurement)-(this time measurement).vertline./(Tp)P}k{Tc-(processing running time until now)}P
where P is a power exponent representing heat generation with respect to heat emission;
and where k is a machining constant;
if correction of machine position is required, predicting the displacement of the machine position on the basis of the following equation:
machine position displacement={.vertline.(previous time measurement)-(this time measurement.vertline./(Tp)P}.multidot.k{Tc-(processing running time until now)}P
where P is a power exponent representing heat generation with respect to heat emission;
and where k is a machining constant;
if correction of machine position is requried, predicting the displacement of the machine position on the basis of the following equation:
machine position={.vertline.(previous time measurement)-(this time measurement.vertline./(Tp)P}.multidot.k{Tc.vertline.(processing running time until now)}P
where P is a power exponent representing heat generation with respect to heat emission;
and where k is a machining constant;
comparing the prediction value of the displacement of the moving position and the allowable value with each other;
executing no correction in the case where the allowable value is not exceeded;
executing at least one of warning during the automatic operation, automatic judgment of whether interruption of the measurement is possible, and measurement and correction of the displacement of the machine origin, on the basis of the results in which the prediction of the displacement of the machine origin is executed.

20 more elements

A numerical control method for controlling a numerical control (NC) machine having an electrical power source for providing power to operate said numerical control machine, a tool means and a drive means for effecting the machining of a workpiece, a measuring means for measuring machine tool position, a memory means for storing data including at least previous time thermal displacement data, this time thermal displacement data and correction values, and a processing means, said processing means being operative by periodic processing to execute a processing program, comprising the steps of:

turning-on said electric power source;
storing a machine origin, a specific moving position, an allowable value of position errors, each of a plurality of thermal-displacement data, a plurality of sampling time data, and processing cycle time, in memory means;
thereupon, (i) collecting data defining an amount of generated heat of thermal displacement of said drive means, (ii) counting of a sampling time of thermal displacement, and (iii) measuring the machine position, comprising one of the machine origin, the workpiece reference position, and the workpiece-mounting reference-block position and (iv) bringing said correction values entirely to zero and storing a value of the measurement as an initial value;
executing adaptation processing in which the thermal-displacement sampling time of said drive means is changed, depending upon whether the thermal displacement is within a range of an allowable error within a processing cycle time;
after measurement of said machine position, comprising at least one of the machine origin, the workpiece reference position and the workpiece-mounting reference-block position, which is used as a reference position, initializing an automatic correction;
counting of the measurement sampling time of the machine position and the moving position;
upon counting to a stored measurement sampling time Tp, concurrently (i) executing adaptation processing of measurement sampling time of the machine position and the moving position, and (ii) executing computation processing of the displacement of the moving position;
executing the correction of the moving position such that the error and a first allowable error value per time are compared with each other, to decide whether or not the measurement and correction of the moving position are required;
if correction of moving position is required, executing prediction of displacement of the moving position (MmtTcf) on the basis of the following equation:
MmtTcf={.vertline.(previous time measurement )-(this time measurement).vertline./(Tp)P}.multidot.k{Tc-(processing running time until now)}P
where P is a power exponent representing heat generation with respect to heat emission;
and where k is a machining constant;
comparing the prediction value of the displacement of the moving position and a second allowable value with each other;
executing no correction in the case where the prediction value does not exceed said second allowable value;
and
executing at least one of warning during the automatic operation, automatic judgment of whether interruption of the measurement is possible, and measurement and correction of the displacement of the moving position, on the basis of the results in which the prediction of the displacement of the moving position is executed.

13 more elements

Dependencies are inferred from the claim text.

Facts

Application

08/004,057Filed 13 Jan 1993

Granted

22 Aug 1995

Term ends

Not estimatedThe source records don’t support an estimate.

Classification6 codes

G05B 19/404
Numerical control [NC], i.e. automatically operating machines, in particular machine tools, e.g. in a manufacturing environment, so as to…
G05B 2219/42259
Servomotor, servo controller kind till VSS: variable sampling rate as function of thermal displacement
G05B 2219/49205
Nc machine tool, till multiple: compensate with stored values as function of machining time
G05B 2219/49207
Nc machine tool, till multiple: compensate thermal displacement using measured distance

Abstract

Claims29

Dependent claims

turning on said electrical power source;
storing a thermal-displacement sampling time (Tt) and a processing cycle time (Tc), in said memory means;
selecting a measurement reference position to serve as a machine origin;
storing data identifying said machine origin with said memory means;
measuring the shift of an absolute position of said machine origin as a measurement reference position before every processing, so that said shift of said absolute position serves as an initial value;
collecting data of an amount of heat generated thermal displacement of said drive means for a duration of said stored thermal-displacement sampling time and storing said displacement data in said memory means as this-time data;
upon reaching said stored thermal displacement sampling time, concurrently (i) executing adaptation processing which changes the sampling time of the thermal displacement of said drive means, depending upon whether or not the thermal displacement of said drive means is within a range of an allowable error within said processing cycle time, and (ii) comparison computation processing of the amount of thermal displacement;
comparing said thermal displacement of said drive means and a minimum movement setting unit with each other to determine whether or not said thermal displacement is within a first allowable error;
executing a correction of said thermal displacement if said displacement is not within said first allowable error;
rewriting said previous-time thermal-displacement data as this-time data after correction of the thermal displacement;
and
executing thermal-displacement correction for said drive means.

9 more elements

A numerical control method for controlling a numerical control (NC) machine having an electrical power source for providing power to operate said numerical control machine, a tool means comprising a machine tool and a drive means for effecting the machining of a workpiece, a measuring means for measuring said machine tool position, a memory means for storing data including at least previous-time thermal displacement data and this-time thermal displacement data, and a processing means, said processing means being operative by periodic processing to execute a processing program, comprising the steps of:

turning on said electrical power source;
selecting a measurement reference position to serve as a workpiece reference position;
storing at least data of a machine origin and said workpiece reference position in said memory means;
executing zero-point correction of said measuring means;
measuring said workpiece reference position with said measuring means when said electric power source is turned on;
bringing correction values entirely to zero with a value of the measurement by said measuring means serving as an initial value;
measuring the shift of an absolute position of the workpiece reference position every processing cycle;
correcting for thermal displacement, comprising correction processing of the workpiece reference position, during possible interruptions of said program;
storing a thermal-displacement sampling time (Tt) and a processing cycle time (Tc), in said memory means;
following said turning-on of said electric power source, collecting data of an amount of heat generated thermal displacement of said drive means for a duration of said stored thermal-displacement sampling time and storing said displacement data in said memory means as this-time data;
upon reaching said stored thermal displacement sampling time, concurrently executing (i) adaptation processing in which the thermal-displacement sampling time of said drive means is changed, depending upon whether or not the thermal displacement of said drive means is within a range of a first allowable error within a processing cycle time, and (ii) comparison computation processing of the amount of thermal displacement;
and
executing correction of the thermal displacement of said drive means on the basis of a comparison of the thermal displacement error and a minimum movement setting unit with each other.

10 more elements

A numerical control method for controlling a numerical control (NC) machine having an electrical power source for providing power to operate said numerical control machine, a tool means comprising a machine tool and a drive means for effecting the machining of a workpiece, a measuring means for measuring said machine tool position, a memory means for storing data including at least previous-time thermal displacement data and this-time thermal displacement data, and a processing means, said processing means being operative by periodic processing to execute a processing program, comprising the steps of:

turning on said electrical power source;
selecting a measurement reference position to serve as a workpiece reference position;
storing at least data of a machine origin and said workpiece reference position in said memory means;
executing zero-point correction of said measuring means;
measuring said workpiece reference position with said measuring means when said electric power source is turned on;
bringing correction values entirely to zero with a value of the measurement by said measuring means serving as an initial value;
measuring the shift of an absolute position of the workpiece reference position every processing cycle;
correcting for thermal displacement, comprising correction processing of the workpiece reference position, during possible interruptions of said program;
storing the measurement sampling time (Tp) of an allowable value of a position error (D) for a machine position and a moving position in said memory means;
initializing automatic correction after measurement of a workpiece reference position;
counting the measurement sampling time of the machine position and the moving position;
upon reaching said value Tp, executing adaptation processing which changes the measurement sampling time of the machine position and the moving position if said counted sampling time is not within said time (Tp) of an allowable position error;
repeating said counting and adaptation processing of the measurement sampling time of the machine position and the moving position until an electric power source is turned off, regardless of a main processing;
executing the correction of the workpiece reference position such that the measured error and a second allowable error value per time are compared with each other to decide whether or not the workpiece reference position is required to be measured and corrected;
executing prediction of the displacement of the workpiece reference position (MwtTcf) on the basis of the following equation:
MwtTcf={.vertline.(previous time measurement)=(this time measurement.vertline./(Tp)P}.multidot.k{Tc-(processing running time until now)}P
where P is a power exponent representing heat generation with respect to heat emission;
and where k is a machining constant;
comparing a prediction value of the displacement of the workpiece reference position with a measured value until the difference is within a third allowable error;
executing at least one of a warning during the automatic operation, automatic judgment on interruption of machine halt, and machine halt on the basis of the results in which the prediction value of the displacement of the workpiece reference position and said third allowable error are compared with each other.

17 more elements

A numerical control method for controlling a numerical control (NC) machine having an electrical power source for providing power to operate said numerical control machine, a tool means and a drive means for effecting the machining of a workpiece, a measuring means for measuring machine tool position, a memory means for storing data including at least previous-time thermal displacement data and this-time thermal displacement data, and a processing means, said processing means being operative by periodic processing to execute a processing program, comprising the steps of:

turning on said electrical power source;
selecting a measurement reference position to serve as a workpiece-mounting reference-block position;
storing at least data of a machine origin and said workpiece reference position in said memory means;
executing zero-point correction of said measuring means;
measuring said workpiece-mounting reference-block position with said measuring means when said electric power source is turned on;
bringing correction values entirely to zero with a value of the measurement by said measuring means serving as an initial value;
measuring the shift of an absolute position of the workpiece-mounting reference-block position every processing cycle;
correcting for thermal displacement, comprising correction processing of the workpiece-mounting reference-block position, during possible interruptions of said program;
storing a thermal-displacement sampling time (Tt) and a processing cycle time (Tc), in said memory means;
following said turning-on of said electric power source, collecting data of an amount of heat generated thermal displacement of said drive means for a duration of said stored thermal-displacement sampling time and storing said displacement data in said memory means as this-time data;
upon reaching said stored thermal displacement sampling time, concurrently executing (i) adaptation processing in which the thermal-displacement sampling time of said drive means is changed, depending upon whether or not the thermal displacement of said drive means is within a range of a first allowable error within a processing cycle time, and (ii) comparison computation processing of the amount of thermal displacement;
executing correction of the thermal displacement of said drive means on the basis of a comparison of the thermal displacement error and a minimum movement setting unit with each other.

9 more elements

A numerical control method for controlling a numerical control (NC) machine having an electrical power source for providing power to operate said numerical control machine, a tool means and a drive means for effecting the machining of a workpiece, a measuring means for measuring machine tool position, a memory means for storing data including at least previous-time thermal displacement data and this-time thermal displacement data, and a processing means, said processing means being operative by periodic processing to execute a processing program, comprising the steps of:

turning on said electrical power source;
selecting a measurement reference position to serve as a workpiece-mounting reference-block position;
storing at least data of a machine origin and said workpiece reference position in said memory means;
executing zero-point correction of said measuring means;
measuring said workpiece-mounting reference-block position with said measuring means when said electric power source is turned on;
bringing correction values entirely to zero with a value of the measurement by said measuring means serving as an initial value;
measuring the shift of an absolute position of the workpiece-mounting reference-block position every processing cycle;
correcting for thermal displacement, comprising correction processing of the workpiece-mounting reference-block position, during possible interruptions of said program;
storing the measurement sampling time (Tp) of an allowable value of a position error (D) for a machine position and a moving position in said memory means;
initializing automatic correction after measurement of a workpiece-mounting reference-block position;
counting the measurement sampling time of the machine position and the moving position;
upon reaching said stored value Tp, executing adaptation processing which changes the measurement sampling time of the machine position and the moving position if said counted sampling time is not within said time (Tp) of an allowable position error, said adaptation processing being conducted repeatedly until said electric power source is turned off, regardless of a main processing;
executing the correction of the workpiece-mounting reference-block position such that the measured error and a first allowable error value per time are compared with each other to decide whether or not the workpiece-mounting reference-block position is required to be measured and corrected;
executing prediction of the displacement of the workpiece-mounting reference-block position (MwbtTcf) on the basis of the following equation:
MwbtTcf={.vertline.(previous time measurement)-(the time measurement).vertline./(Tp)P}.multidot.k{Tc-(processing running time until now)}P
where P is a power exponent representing heat generating with respect to heat emission;
and where k is a machining constant;
comparing a prediction value of the displacement of the workpiece-mounting reference-block position with a measured value until the difference is within a second allowable error;
executing at least one of a warning during the automatic operation, automatic judgment on interruption of machine halt, and machine halt on the basis of the results in which the prediction value of the displacement of the workpiece-mounting reference-block position and the allowable error are compared with each other.

16 more elements

turning on said electrical power source;
storing a machine origin, a specific moving position, an allowable value of position errors, each of a plurality of thermal-displacement data, a plurality of sampling time data, and processing cycle time, in memory means;
thereupon, (i) collecting data defining an amount of heat generated thermal displacement of said drive means, (ii) counting of a sampling time of thermal displacement, and (iii) measuring the machine position, comprising one of the machine origin, the workpiece reference position, and the workpiece-mounting reference-block position;
executing adaptation processing in which the thermal-displacement sampling time of said drive means is changed, depending upon whether the thermal displacement is within a range of a first allowable error within a processing cycle time;
after measurement of said machine position, which is used as a reference position, initializing an automatic correction;
counting the measurement sampling time of the machine position and the moving position;
upon counting to a stored measurement sampling time Tp, concurrently (i) executing adaptation processing of measurement sampling time of the machine position and the moving position, (ii) executing computation processing of the displacement of the moving position and (iii) executing computation of the thermal displacement of the machine origin;
on the basis of said corresponding execution step, deciding whether or not measurement and correction of the moving position and machine position are required;
if correction of moving position is required, executing prediction of displacement of the moving position (MmtTcf) on the basis of the following equation:
MmtTcf={.vertline.(previous time measurement)-(this time measurement).vertline./(Tp)P}k{Tc-(processing running time until now)}P
where P is a power exponent representing heat generation with respect to heat emission;
and where k is a machining constant;
if correction of machine position is required, predicting the displacement of the machine position on the basis of the following equation:
machine position displacement={.vertline.(previous time measurement)-(this time measurement.vertline./(Tp)P}.multidot.k{Tc-(processing running time until now)}P
where P is a power exponent representing heat generation with respect to heat emission;
and where k is a machining constant;
if correction of machine position is requried, predicting the displacement of the machine position on the basis of the following equation:
machine position={.vertline.(previous time measurement)-(this time measurement.vertline./(Tp)P}.multidot.k{Tc.vertline.(processing running time until now)}P
where P is a power exponent representing heat generation with respect to heat emission;
and where k is a machining constant;
comparing the prediction value of the displacement of the moving position and the allowable value with each other;
executing no correction in the case where the allowable value is not exceeded;
executing at least one of warning during the automatic operation, automatic judgment of whether interruption of the measurement is possible, and measurement and correction of the displacement of the machine origin, on the basis of the results in which the prediction of the displacement of the machine origin is executed.

20 more elements

A numerical control method for controlling a numerical control (NC) machine having an electrical power source for providing power to operate said numerical control machine, a tool means and a drive means for effecting the machining of a workpiece, a measuring means for measuring machine tool position, a memory means for storing data including at least previous time thermal displacement data, this time thermal displacement data and correction values, and a processing means, said processing means being operative by periodic processing to execute a processing program, comprising the steps of:

turning-on said electric power source;
storing a machine origin, a specific moving position, an allowable value of position errors, each of a plurality of thermal-displacement data, a plurality of sampling time data, and processing cycle time, in memory means;
thereupon, (i) collecting data defining an amount of generated heat of thermal displacement of said drive means, (ii) counting of a sampling time of thermal displacement, and (iii) measuring the machine position, comprising one of the machine origin, the workpiece reference position, and the workpiece-mounting reference-block position and (iv) bringing said correction values entirely to zero and storing a value of the measurement as an initial value;
executing adaptation processing in which the thermal-displacement sampling time of said drive means is changed, depending upon whether the thermal displacement is within a range of an allowable error within a processing cycle time;
after measurement of said machine position, comprising at least one of the machine origin, the workpiece reference position and the workpiece-mounting reference-block position, which is used as a reference position, initializing an automatic correction;
counting of the measurement sampling time of the machine position and the moving position;
upon counting to a stored measurement sampling time Tp, concurrently (i) executing adaptation processing of measurement sampling time of the machine position and the moving position, and (ii) executing computation processing of the displacement of the moving position;
executing the correction of the moving position such that the error and a first allowable error value per time are compared with each other, to decide whether or not the measurement and correction of the moving position are required;
if correction of moving position is required, executing prediction of displacement of the moving position (MmtTcf) on the basis of the following equation:
MmtTcf={.vertline.(previous time measurement )-(this time measurement).vertline./(Tp)P}.multidot.k{Tc-(processing running time until now)}P
where P is a power exponent representing heat generation with respect to heat emission;
and where k is a machining constant;
comparing the prediction value of the displacement of the moving position and a second allowable value with each other;
executing no correction in the case where the prediction value does not exceed said second allowable value;
and
executing at least one of warning during the automatic operation, automatic judgment of whether interruption of the measurement is possible, and measurement and correction of the displacement of the moving position, on the basis of the results in which the prediction of the displacement of the moving position is executed.

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Numerical control method for controlling various kinds of machine tools by correcting for thermal displacement

Life of this patent

Abstract

Claims29

Numerical control method for controlling various kinds of machine tools by correcting for thermal displacement

Life of this patent

Abstract

Claims29