Method and apparatus for controlling numerically controlled machine tool

A method of controlling a numerically controlled machine tool by executing a numerical control program fetched from a read and interpret unit of a numerical control unit to control a drive means of at least one feed shaft via an execution command unit, an interpolation unit and a servo control unit, comprising the steps of:

• presetting acceleration/deceleration time constants for rapid and cutting feed operations of said feed axis, a cutting feed rate, and predetermined temperature and heat generation amount data tolerable for said drive means of said feed axis;
• computing a temperature of said drive means based on control data of said numerical control program;
• determining an amount of heat generation tolerable for said drive means in accordance with the computed temperature of said drive means;
• computing, during the cutting feed operation, a cut feed heat generation amount and a cutting load heat generation amount in response to a cutting load, based on control data of said numerical control program;
• comparing said predetermined tolerable heat generation amount with said computed cutting feed heat generation amount;
• and
• controlling a cutting feed rate of said feed axis from the result of said comparing step while taking a ratio that said computed amount of the cutting load heat generation represents of said cutting feed heat generation amount into consideration.

A method of controlling a numerically controlled machine tool by performing a numerical control program fetched from a read and interpret unit of a numerical control unit to control a drive means of at least one feed axis via an execution command unit, an interpolation unit and a servo control unit, comprising the steps of:

• presetting acceleration/deceleration time constants τr0and τC0during rapid and cutting feed operations, respectively, of said feed axis, and temperature data representing a predetermined temperature MT and heat generation amount data representing a predetermined heat generation amount Qa which are tolerable for said drive means of said feed axis;
• computing the temperature and the heat generation amount at each moment of said drive means from the current data or the torque command data output from said servo control unit to said drive means;
• determining the heat generation amount Qa tolerable within a predetermined time t of said drive means in accordance with said computed temperature at each moment;
• computing the total heat generation amount QA within said predetermined time t, the rapid feed heat generation amount QR at the time of rapid feed and the cutting feed heat generation amount QC at the time of cutting feed of said drive means from said computed heat generation amount at each moment;
• comparing said computed total heat generation amount QA within the predetermined time t with said determined tolerable heat generation amount Qa;
• computing the acceleration/deceleration time constants τr and τC for rapid feed and cutting feed, respectively, of said feed axis in accordance with the ratio which said rapid feed heat generation amount QR and said cutting feed heat generation amount QC represents of said total heat generation amount QA within said predetermined time t, in the case where the total heat generation amount QA within said predetermined time t is larger than said tolerable heat generation amount Qa;
• and
• controlling the acceleration/deceleration time constants for rapid feed and cutting feed of said feed axis by changing the set time constants τr0and τC0to said computed acceleration/deceleration time constants τr and τC, respectively.

A method of controlling a numerically controlled machine tool by performing a numerical control program fetched from a read and interpret unit of a numerical control unit to control a drive means of at least one feed axis via an execution command unit, an interpolation unit and a servo control unit, comprising the steps of:

• presetting acceleration/deceleration time constants for said feed axis, a cut feed rate, data on a predetermined tolerable temperature of said drive means of said feed axis and data on a tolerable predetermined heat generation amount;
• predictively computing temperatures of said drive means at respective moments based on control data of said numerical control program while at the same time computing heat generation amounts at the respective moments;
• comparing said computed temperatures with said set predetermined tolerable temperature data;
• controlling acceleration/deceleration time constants of said feed axis in accordance with a result of the comparing step while determining a tolerable heat generation amount of said drive means in accordance with said computed temperatures of said drive means at respective moments;
• computing a cutting feed heat generation amount during the cutting feed operation of said drive means from said computed heat generation amount at each moment;
• computing a cutting load heat generation amount corresponding to a cutting load of said drive means, based on the control data of said numerical control program;
• comparing said computed cutting feed heat generation amounts with said determined tolerable heat generation amounts;
• and
• controlling said cutting feed rate of said feed axis in accordance with the ratio which said computed cutting load heat generation amount represents of said cutting feed heat generation amount from the result of the comparing step.

A method of controlling a numerically controlled machine tool by performing a numerical control program fetched from a read and interpret unit of a numerical control unit to control a drive means of at least one feed axis via an execution command unit, an interpolation unit and a servo control unit, comprising the steps of:

• presetting acceleration/deceleration time constants of said feed axis, a cut feed rate, a curve indicating a predetermined tolerable temperature of said drive means of said feed axis and a curve indicating a tolerable predetermined heat generation amount;
• computing temperatures at respective moments of said drive means from current data or torque command data transferred from said servo control unit to said drive means to produce a temperature curve thereof and to compute a heat generation amount at the respective moments;
• comparing an inclination of said produced temperature curve with that of the temperature curve indicating said set tolerable predetermined temperature;
• computing acceleration/deceleration time constants of said feed axis from a relation between the inclination of the temperature curve indicating said set tolerable predetermined temperature and said acceleration/deceleration time constants to control said acceleration/deceleration time constants of said feed axis and to determine a tolerable heat generation amount of said drive means in accordance with said computed temperatures at the respective moments, in the case where the inclination of said produced temperature curve is larger than that of the temperature curve indicating said set tolerable predetermined temperature;
• computing a cutting feed heat generation amount at the time of cutting feed of said drive means from said computed heat generation amount at the respective moments;
• computing a cutting load heat generation amount corresponding to a cutting load of said drive means from the current data or the torque command data output from said servo control unit to said drive means;
• comparing said computed cutting feed heat generation amount with said determined tolerable heat generation amount;
• and
• controlling the cutting feed rate of said feed axis in accordance with the ratio which said computed cutting load heat generation amount represents of said cutting feed heat generation amount from the result of the afore-comparing step.

A method of controlling a numerically controlled machine tool by executing the numerical control program fetched from a read and interpret unit of a numerical control unit to control a drive means of at least one feed axis via an execution command unit, an interpolation unit and a servo control unit, comprising the steps of:

• presetting acceleration/deceleration time constants of said feed axis, a cut feed rate, data on a tolerable predetermined temperature of said drive means of said feed axis, data on a tolerable predetermined heat generation amount and tolerable number of times accelerated/decelerated per unit time;
• counting the number of times accelerated/decelerated per unit time of said drive means from a program data output from the read and interpret unit or said execution command unit of said numerical control unit;
• comparing the counted number of times accelerated/decelerated per unit time with said set tolerable number of times accelerated/decelerated per unit time;
• computing the acceleration/deceleration time constants of said feed axis from a relation between the set number of times accelerated/decelerated per unit time and the acceleration/deceleration time constants to control said acceleration/deceleration time constants of said feed axis and to compute the cutting load heat generation amount corresponding to the temperature, the heat generation amount and the cutting load at respective moments of said drive means from the current data or the torque command data transferred from said servo control unit to said drive means, in the case where said counted number of times accelerated/decelerated exceeds said tolerable number of times accelerated/decelerated;
• determining said tolerable heat generation amount of said drive means in accordance with said computed temperature at the respective moments;
• computing a cutting feed heat generation amount during the cutting feed operation of said drive means from said computed heat generation amount at the respective moments;
• comparing said computed cutting feed heat generation amount with said determined tolerable heat generation amount;
• and
• controlling said cutting feed rate of said feed axis in accordance with the ratio which said computed cutting load heat generation amount represents of said cutting feed heat generation amount from the result of the afore-comparing step.

A method of controlling a numerically controlled machine tool by executing the numerical control program fetched from a read and interpret unit of a numerical control unit to control a drive means of at least one feed axis via an execution command unit, an interpolation unit and a servo control unit, comprising the steps of:

• presetting acceleration/deceleration time constants of said feed axis, a cut feed rate, data on a predetermined tolerable temperature of said drive means of said feed axis and data on a predetermined tolerable heat generation amount;
• detecting temperatures of said drive means;
• comparing said detected temperature data with said set tolerable predetermined temperature data;
• increasing acceleration/deceleration time constants of said feed axis while computing a cutting load heat generation amount corresponding to a heat generation amount and said cutting load at respective moments of said drive means from current data or torque command data transferred from said servo control unit to said drive means, in the case where said detected temperature data is higher than said set tolerable predetermined temperature data;
• determining a tolerable heat generation amount of said drive means in accordance with said detected temperatures;
• computing a cut feed heat generation amount during the cutting feed operation of said drive means from said computed heat generation amount at the respective moments;
• comparing said computed cutting feed heat generation amount with said determined tolerable heat generation amount;
• and
• controlling the cutting feed rate of said feed axis in accordance with the ratio which said computed cutting load heat generation amount represents of said cutting feed heat generation amount from the result of the afore-comparing step.

An apparatus for controlling a numerically controlled machine tool by executing the numerical control program fetched from a read and interpret unit of a numerical control unit to control a drive means of at least one feed axis via an execution command unit, an interpolation unit and a servo control unit, comprising:

• data storage means for setting and storing acceleration/deceleration time constants for rapid and cut feed operations of the feed axis, data on a tolerable predetermined temperature of said drive means of said feed axis and data on a predetermined tolerable heat generation amount;
• temperature computing means for computing a temperature of said drive means based on a control data of said numerical control program;
• tolerable heat generation amount determining means for determining the tolerable heat generation amount of said drive means in accordance with the temperature computed by said temperature computing means;
• heat generation amount computing means for computing a total heat generation amount within a predetermined time, a rapid feed heat generation amount during the rapid feed operation of said drive means and a cutting feed heat generation amount during the cutting feed operation of said drive means based on a control data of said numerical control program;
• and
• acceleration/deceleration time constant computing means for computing and outputting said acceleration/deceleration time constant of said feed axis based on the total heat generation amount within a predetermined time computed by said heat generation computing means, the rapid feed heat generation amount, the cutting feed heat generation amount and the tolerable heat generation amount determined by said tolerable heat generation amount determining means.

An apparatus for controlling a numerically controlled machine tool by executing the numerical control program fetched from a read and interpret unit of a numerical control unit to control a drive means of at least one feed axis via an execution command unit, an interpolation unit and a servo control unit, comprising:

• data storage means for setting and storing a cutting feed rate of said feed axis, tolerable predetermined temperature data of said drive means of said feed axis, and tolerable predetermined heat generation amount data;
• temperature computing means for computing a temperature of said drive means based on a control data of said numerical control program;
• tolerable heat generation amount determining means for determining a tolerable heat generation amount of said drive means in accordance with the temperatures computed by said temperature computing means;
• heat generation amount computing means for computing a heat generation amount of said drive means based on the control data of said numerical control program;
• and
• cutting feed rate computing means for computing a cutting load of said drive means based on the control data of said numerical control program while computing and outputting the cutting feed rate of said feed axis based on the cutting load heat generation amount corresponding to said cutting load, the cutting feed heat generation amount computed by said heat generation amount computing means and the tolerable heat generation amount determined by said tolerable heat generation amount determining means.

A numerically controlled machining apparatus by executing the numerical control program fetched from a read and interpret unit of a numerical control unit to control a drive means of each feed axis via an execution command unit, an interpolation unit and a servo control unit, comprising:

• a plurality of feed axes, each including a drive means provided with a servo amplifier and a feed motor;
• a mechanical assembly including at least a mechanical element and a moving member coupled to each of said feed axes;
• and
• a control unit for controlling the operation of said mechanical assembly;
• wherein said control unit comprises:
• data storage means for setting and storing acceleration/deceleration time constants for rapid and cutting feed operations of each of said feed axes, a cut feed rate, predetermined tolerable temperature data of each of said drive means and tolerable predetermined heat generation amount data;
• temperature computing means for computing by simulation temperatures of said drive means based on the control data of said numerical control program;
• tolerable heat generation determining means for determining a tolerable heat generation amount of said drive means in accordance with the temperature computed by said temperature computing means;
• heat generation amount computing means for computing a total heat generation amount within a predetermined time of said drive means, a rapid feed heat generation amount at the time of rapid feed, a rapid feed acceleration/deceleration heat generation amount at the time of acceleration/deceleration, a cutting feed heat generation amount at the time of cutting feed and a cutting feed acceleration/deceleration heat generation amount at the time of acceleration/deceleration from control data of said numerical control unit;
• acceleration/deceleration time constant computing means for computing and outputting the acceleration/deceleration time constants of said feed axes based on the total heat generation amount within a predetermined time, the rapid feed heat generation amount, the rapid feed acceleration/deceleration heat generation amount and the cut feed heat generation amount computed by said heat generation amount computing means, and the tolerable heat generation amount determined by said tolerable heat generation determining means;
• and
• cutting feed rate computing means for computing a cutting load of each of said drive means based on control data of said numerical control program, and computing and outputting a cutting feed rate of each of said feed axes based on the cutting load heat generation amount corresponding to said cutting load, the cutting feed heat generation amount computed by said heat generation amount computing means and the tolerable heat generation amount determined by said tolerable heat generation determining means.