System for controlling machining of a part

1. A control system used in the machining of a part by a machining machine, comprising:

an acquisition module configured to acquire values of a set of input parameters relating to cutting conditions and properties of a material of said part, and

a microprocessor configured to:

determine at least one operational cutting parameter representative of a cutting signal from the machining machine by using a set of output parameters of an integrity model constructed previously in a learning phase, said integrity model linking said set of input parameters to said set of output parameters comprising specific cutting coefficients representative of a material integrity of the part, and

establish at least one fatigue threshold of said at least one operational cutting parameter, said fatigue threshold allowing a progress of cutting operations to be controlled,

wherein

the acquisition module is configured to acquire, in the learning phase, values of input parameters comprising:

macroscopic kinematic parameters comprising a cutting speed parameter, a tooth advance parameter, a parameter of axial engagement of a tool, and a parameter of radial engagement of the tool;

parameters of a geometry of the tool comprising a rake angle and a helix angle;

tribology parameters comprising a mean angle of friction; and

parameters of the material comprising a specific heat capacity, a density and a Taylor-Quinney coefficient; and

the microprocessor is configured to construct the integrity model by using physical analytical and/or empirical relationships linking said set of input parameters to said set of output parameters representative of the cutting forces.

2. The control system according to claim 1 , wherein:

said acquisition module is configured to acquire, during the machining of the part, at least one cutting signal, and

said microprocessor being configured to control the progress of the cutting operations by ensuring that a value of said at least one cutting signal is bounded by said fatigue threshold.

3. The control system according to claim 1 ,

wherein said at least one operational cutting parameter is a torque parameter representative of a torque signal from the machining machine or a power parameter representative of a power signal from the machining machine, and

wherein said at least one fatigue threshold is a torque threshold or a power threshold.

4. The control system according to claim 3 , wherein the microprocessor is configured to

calculate, by using geometrical and empirical relationships, the values of angles characteristic of an oblique cutting comprising an oblique shear angle, a normal shear angle, a normal projection angle, an oblique projection angle and a chip flow angle, as a function of values of a mean angle of friction, of a rake angle and of a helix angle, and

calculate, by using analytical and empirical relationships, values of the parameters of the orthogonal cutting comprising the thickness values of a shear band, and an asymmetry factor by using the values of a cutting speed, the normal shear angle and the rake angle.

5. The control system according to claim 4 , wherein the microprocessor is configured to

determine a shear deformation and deformation ratio values in the primary shear band as a function of the thickness values of the shear band and of the asymmetry factor, and

use a law of behavior of the material and said shear deformation and deformation ratio values as well as the parameter values of the material to determine a shear stress in the primary shear band.

6. The control system according to claim 5 , wherein the microprocessor is configured to calculate the specific cutting coefficients comprising a cutting edge tangential force coefficient, a cutting edge radial force coefficient and a cutting edge axial force coefficient, as a function of the shear stress, and the oblique shear angle, the normal shear angle, the normal projection angle, the oblique projection angle and the helix angle.

7. The control system according to claim 6 , wherein the microprocessor is configured to

calculate instantaneous machining forces comprising a cutting edge tangential force, a cutting edge radial force, and a cutting edge axial force, as a function of the specific cutting coefficients, including, a cutting edge tangential force coefficient, a cutting edge radial force coefficient, a cutting edge axial force coefficient, an engaged tooth width, and a chip thickness,

calculate the torque parameter at a spindle and the power parameter at the spindle as a function of the cutting edge tangential force, the cutting speed and the diameter of the tool, and

establish a torque threshold and a power threshold as a function of the torque and power parameters.

8. A numerically-controlled machining machine comprising the control system according to claim 1 .

9. A control method used in the machining of a part by a machining machine, comprising the following steps:

acquiring values of a set of input parameters relating to cutting conditions and material properties of said part, and

determining at least one operational cutting parameter representative of a cutting signal from the machining machine by using a set of output parameters of an integrity model constructed previously in a learning phase, said integrity model linking said set of input parameters to said set of output parameters comprising specific cutting coefficients representative of the material integrity of the part,

establishing at least one fatigue threshold of said at least one operational cutting parameter, said fatigue threshold allowing a progress of cutting operations to be controlled,

acquiring, in the learning phase, values of input parameters comprising:

macroscopic kinematic parameters comprising a cutting speed parameter, a tooth advance parameter, a parameter of axial engagement of a tool, and a parameter of radial engagement of the tool;

parameters of a geometry of the tool comprising a rake angle and a helix angle;

tribology parameters comprising a mean angle of friction; and

parameters of the material comprising a specific heat capacity, a density and a Taylor-Quinney coefficient; and

constructing the integrity model by using physical analytical and/or empirical relationships linking said set of input parameters to said set of output parameters representative of the cutting forces.