WO2007065959A1 - Method for monitoring burr formation in processes involving the drilling of parts - Google Patents

Abstract

The invention relates to a method for monitoring burr formation in processes involving the drilling of parts, which is based on internal signals which are associated with torque values that are captured from the device used to regulate the motor of the head in order to detect the formation of unwanted burrs during the drilling process. According to the invention, five characteristics of the signal are associated with the height of the burr and are relatively insensitive to the parameters of the process. Experiments were carried out on aeronautical aluminium Al 7075-T6 under high-speed conditions and a threshold-based algorithm was developed, which can be used to distinguish burrs outside of the requirements with a reliability of more than 92 % for the range of tested parameters. A suitable implementation of said algorithm can be used as a system for controlling the quality of the drilling operations. The invention is suitable for use in aeronautics.

Description

 "METHOD OF MONITORING THE FORMATION OF BURS IN THE PROCESSES OF DRILLING OF PIECES"

D E S C R I P C I Ó N

Drilling operations usually produce burrs on both the inlet and outlet surfaces. They are formed as a result of the plastic deformation, which largely depends on the ductility of the material. Burrs during drilling constitute an unavoidable obstacle in the automation of assembly processes due to the need for a deburring stage. Burrs are a source of dimensional errors and misalignments; they can cause short circuits in electrical components; reduce the fatigue life of riveted parts; and can act as initial cracking points. For these reasons, the reduction in the quality of drilling operations is a crucial problem, especially for the aeronautical and aerospace industries. In these small burrs are allowed, below a certain height that is between 100 and 150 microns.

For these reasons, in most cases the deburring phase cannot be avoided after drilling. In aeronautical assembly, for example, the components to be joined are drilled together

(multilayer), separated below to remove burrs

(deburred) and finally riveted. The deburring process involves additional work that constitutes 30% of the total cost in precision operations. Most of the problems are associated with the burr at the outlet, since it is much larger than at the inlet. For this reason,

Most of the research on this subject, and in particular this invention has focused on developing strategies to minimize the burr at the exit of the material.

On the one hand, various research groups have optimized the geometry of the tool (drill) so that the dimensions of the burr at the outlet are reduced as far as possible. On the other hand, there is also extensive research aimed at optimizing process parameters to minimize burr. Most of the work is experimental and, for example, control charts have been prepared to have maps with which to estimate the height or shape of the burr depending on the process parameters. Finite element models have also been developed to better understand the burr formation process and to predict the outcome.

The results of these works are of great importance for the optimization of the drilling process, but are not capable of ensuring the quality of the holes, since they do not take into account, for example, the wear of the tool that influences the formation of burrs or stochastic components that cannot be controlled. For these reasons, even when establishing an industrial process under optimal conditions in terms of the tool used and the process parameters, there is always a non-negligible percentage of holes that have a burr height above the customer's requirements. In the aeronautical and aerospace sectors in which the quality of the machined components is of vital importance to ensure the safety of your products, the requirements regarding the maximum permitted burr height are very rigorous. For this reason, burr holes are not allowed even though they only constitute a low percentage and the deburring phase cannot be eliminated. Furthermore, since it is not known which holes have burrs, all of them are deburred, increasing the cost of the operation without actually obtaining a benefit from all the time invested. In this invention we develop the first method for online monitoring of burrs focused on high-speed conditions, of great interest in aeronautics. With it you can avoid the deburring of all holes, reducing this operation to those holes that do not meet customer requirements. Methods for monitoring tool wear have been extensively investigated, but there is no method applied to the height of the burr.

Specifically, the method of the invention is characterized by being a method of monitoring the formation of burrs in parts drilling processes in which a drill head, the head motor regulator, is used, previously establishing a fixed process of drilling in which the value of the process variables is set under the production conditions and among them the value of one or more speeds of advance, in which in each process of drilling parts: a) the admissible height is set burr -A- b) the signal associated with the torque from the head motor regulator is captured, the "cutting zone" comprised between the point where the drill bit touches the input surface in the material is determined in said signal until The drill is again outside the hole after the recoil of the head; c) several zones are defined within the "cutting zone": the "exit point" is established as the point at which the tip of the drill bit crosses the exit surface of the hole; the "exit zone" is established as the zone immediately after the "exit point"; the "reference level" (RL) is calculated as the average value reached by the signal in the area in which the drill bit crosses the internal section of the hole in the section corresponding to the last forward speed used; d) the relative minimum value (N) is defined as the quotient between the minimum value (Minimun) reached by a signal in the "output zone" and the "reference level" (RL):

N = Minimun / RL e) the relative minimum value is calculated for the set process and a comparison relative minimum value (Nc) is established with a pre-established tolerance; f) the signal from the head motor regulator is captured during the industrial drilling process in production, the relative minimum value (N) for each hole is calculated in the "cutting zone", deciding that the height of the burr is admissible if said value (N) is less than the value of the relative minimum of comparison (Nc) with the pre-established tolerance: N <Nc. It is also characterized because: a) three fundamental quantities are defined: ai) the width value (W) of the disturbances whose height is above a pre-established value (which we will denote HP) that could appear in the "post-exit zone"; a2) the maximum height value (H) of the disturbances that may appear in the "post-exit zone"; a3) the slope value (S) calculated in the "exit zone"; b) the width, maximum height and slope values (W, H, S) are calculated for the fixed process, an HP value is set and a comparison value is established for each of the quantities (Wc, Hc, Sc ) with a pre-established tolerance; c) the signal of the head motor regulator is captured during the industrial drilling process in production, the value of width, maximum of ^* height and slope (W, H, S) is calculated in each "cutting zone" for each hole, deciding that the height of the burr is admissible if the preset tolerance is successively met:

It is also characterized because: a) the relative maximum value (M) is defined as the quotient between the maximum value (Maximun) reached by the signal in the "pre-departure zone" and the "reference level" (RL):

M = Maximun / RL b) the relative maximum value is calculated for the fixed process and a comparison relative maximum value (Mc) is established with a pre-established tolerance; c) the signal from the head motor regulator is captured during the industrial drilling process in production, calculated in

The "cutting zone" is the relative maximum value (M) for each hole, deciding that the height of the burr is admissible if said value (M) is less than the value of the relative minimum of comparison (Mc) with the pre-established tolerance: M <Mc. It is also characterized because: a) a neural network is designed and trained that uses the magnitude N defined in 1 d) as an input, the level of burr will be established as an output of the network, which may adopt different defined burr levels for the interest of the user; b) the signal from the head motor regulator is captured during the industrial drilling processes in production, the value of the magnitudes used as inputs of the neural network is calculated for each hole, the output of the neural network will indicate the level burr. It is also characterized because: a) a neural network is designed and trained that uses the magnitudes W, H, S defined in 2d as inputs, the level of burr will be established as an output of the network, which may adopt different levels of burr defined by user interest; b) the signal from the head motor regulator is captured during the industrial drilling processes in production, the value of the magnitudes used as inputs of the neural network is calculated for each hole, the output of the neural network will indicate the level burr.

It is also characterized because: a) a neural network is designed and trained that uses the magnitude M defined in 3d as an input), the level of burr will be established as an output of the network, which may adopt different levels of burr defined by the interest of the user; b) the signal from the head motor regulator is captured during the industrial drilling processes in production, the value of the magnitudes used as inputs of the neural network is calculated for each hole, the output of the neural network will indicate the level burr.

In order to better understand the object of the present invention, a preferred form of practical embodiment is shown in the drawings, susceptible to accessory changes that do not detract from its basis.

Figure 1 is a representation in torque / time coordinates of the complete signal of the regulator associated with the spindle motor.

Figure 2 are representations in torque / penetration coordinates (mm). (a) Cut-off zone of a signal before and after filtering in Fourier space. (b) Cut zone of a signal before and after filtering using Wavelets. Figure 3 is a representation in torque / time coordinates of an estimate of the point of entry of the drill bit into the material as the intersection between two lines.

Figure 4 is a representation in torque / time coordinates of the cutting zone with the pre-exit zone, exit zone, post-exit zone, exit point and reference level: a) with a forward speed b) with two forward speeds.

Figure 5 is a representation of Figure 4b with the five magnitudes sensitive or fundamental to burr formation in the specific case of using two forward speeds.

Figure 6 are four representations (a), (b), (c), (d) of torque / penetration coordinates (mm) of signals with different burr level changing the advance speed mm / rev. A non-limiting practical embodiment of the present invention is described below.

Point

In an industrial drilling process, most of the working conditions are fixed. Both the tool, as the work material, and the dimensions of the hole are well defined. Furthermore, the process parameters are also usually fixed and are determined by the cutting speed (head rotation) and the forward speed. We start from a situation like this to apply the burr monitoring method: tool, material and fixed hole dimensions, and the cutting and advance speed defined in a narrow interval. In our case, a three-axis high-speed machining center, linear motors and Fidia control have been used. Its specifications are:

N: 24000 rpm

Progress: 1 20 m / min Acceleration: 2g m / s2

Nominal power: 27 kW

Nominal torque: 1 6.97 Nm

The test material has been aluminum in its alloys used in aeronautics. Signal acquisition system

During the drilling tests, the analog output of the regulator corresponding to the spindle motor has been captured, which is associated with the torque. Internally it is a current signal in the motor loop, but externally it is presented as a voltage signal in a range between -1 0 and + 1 0 V. It is convenient to adjust the full scale to use the resolution of the measurement to the maximum.

The signal from the spindle motor is an indirect measure of torque, which compared to direct measurements has the advantage of not needing additional devices and facilitating the implementation of the monitoring method in the machine's own CNC control.

Figure 1 shows a signal captured during an example drilling test in which a single hole was made. Four different zones are clearly distinguished. The first range of large oscillations corresponds to the "Acceleration zone" of the head. Once the imposed cutting speed is reached, the torque decreases almost to zero. Then the "Approach Zone" of the tool begins until the work material. The measured torque grows in the "Cutting zone", comprised between the point where the drill bit touches the input surface in the material until the drill bit is out of the hole again after the head recoils. This area includes both the area in which the drill bit passes through the material in the direction and direction of drilling, and the backward travel of the drill bit in the reverse direction until the tip of the tool returns to the entrance surface of the hole. Finally, there is the "Deceleration zone", represented in the negative plane. As a result of the tests carried out, we have reached the conclusion that only the cutting area itself contains relevant information for monitoring burrs.

The signal from the regulator can be rescaled in torque units with the appropriate calibration. This obviously depends on the power curve of the particular machine. In our particular case, the transformation is reduced to the following equation:

5 [V) where TN = 1 6.97 N m is the nominal torque that equals 5 V.

Furthermore, for convenience and to better understand the process, it is useful to represent the signal depending on the path of the tool (regardless of whether it is forward or backward). Either a transformation from time to length can be made from the advance speeds of carriage Z, or by capturing the control signal associated with the position of carriage Z. The most useful thing is to consider the zero of Z when the tip of The bit touches the input surface of the material. Monitoring system

From the tests carried out, it is obtained as a basic result that some magnitudes of the signal in the cutting area give relevant information on the size of the burr caused, so that the essence of the invention resides in the monitoring of the process based on the quantification of said magnitudes. . a) Signal processing

Before calculating the magnitudes / attributes that interest us of the captured signal, it is essential to filter the noise and the frequencies that mask the relevant information. The information needed for the monitoring system is contained in the signal envelope in the "Cut zone".

The usual filtering can be used for this task

(window and filter application) or use a more advanced method such as the Wavelet transform. Figure 2 shows two examples of filtered signals, one in Fourier space with a filter.

Butterworth and the second by Wavelets Daubechies. b) Calculation of the magnitudes / attributes sensitive to the burr

Once the signal has been filtered, the "Cut zone" of each of the signals in the time domain, specifically the part around the tool outlet, is analyzed, since in that section the burr is formed. Different strategies can be used to locate this section. The simplest is from the position of carriage Z: it would suffice to take the zero on the input surface; the range around Z corresponding to the thickness of the material would be analyzed. In the event that the position of carriage Z is not available directly, the following procedure can be followed (Figure 3):

• The section of the signal in which the tool approaches the material is adjusted to a straight line. It will be a practically horizontal line. "The section of the signal in which the torque increases until it stabilizes in the cutting zone approaches another line.

"The point at which they intersect can be considered the point at which the tool touches the surface. This point is taken as zero." From the speed of advance the "Exit point" is estimated, converting the time into depth along the length of the hole (it is not necessary to change the sign when changing the direction of travel of the tool). Normally coincides with the point where the torque value decreases. Once the "Cutting zone" and the "Exit point" have been defined, several zones are defined within the "Cutting zone" (Figures 4 ^a and 4b):

• the "exit zone" is established as the zone immediately after the "exit point", which comprises from when the tip of the drill bit touches the exit surface of the hole until it begins to recede;

• a "post-exit zone" is established that successively includes the "exit zone" and the return of the bit until it is outside the hole; • a "pre-departure zone" is established immediately before the "departure point".

Furthermore, the "Reference level" (RL) is defined as the average value reached by the signal in the area in which the drill bit passes through the internal section of the hole in which it is approximately constant for fixed process conditions. Figure 4a shows an example in which a single forward speed has been used throughout the entire hole, while in Figure 4b two different forward speeds have been used. In the first case the reference level is calculated as the average of the value of the signal in the central part of the hole, while in the second case it is calculated as the average in the section corresponding to the second speed. It would be calculated in a similar way if 3 speeds were used along the length of the hole, only calculated in the section corresponding to the last speed. In case 4b, only the forward speed has been varied, but a similar behavior would be obtained by changing the cutting speed or both (although these are not frequent cases). According to these definitions, and according to the invention, five quantities are defined in turn that are sensitive to the formation of burr (Figure 5):

• Relative minimum (N) after leaving the tool. The minimum is measured in the "Output Zone" (Minimun) and is divided by the reference level (Reference Level).

N = Minimun / Reference Level

If this minimum is too high, it indicates that the burr is outside the requirements. This magnitude is the one that best detects the signals associated with very large burrs.

• Width (Width, W) of the disturbances in the "Post-exit zone". If it is too large it indicates a burr out of requirements. • Height (Height, H) of the disturbances in the "Post-output zone". If it is too large it indicates a burr out of requirements.

• Slope (S) of the curve during the tool exit. If it is small burr out of requirements.

The last 3 (W, H, S) are the most interesting for intermediate burrs, close to the thresholds allowed in the aeronautical sector.

• Relative maximum (M) before the exit of the tool. To calculate it, the maximum of the signal in a certain range is measured before of the tool output (Maximun) and is divided by the average of the signal during the cut-off time (Reference Level):

M = Maximun / Reference Level

If this maximum is too high, it indicates that the burr is outside the requirements.

This is the least interesting magnitude, since it is breached in a very low proportion of cases, although for very rigorous processes it is also useful.

The characteristics H and W are beyond the drilling operation itself, since the interval in which they are calculated includes the recoil of the head. Once the hole is made, the drill bit comes out a certain distance beyond the outlet surface and quickly reverses. Ideally, it should no longer cut during this section of the signal and therefore the pair should acquire values close to zero. However, on many occasions disturbances appear, indicating an undesired burr formation. Hence, it is also necessary to take into account these magnitudes. c) Calibration of the monitoring system

Once an algorithm has been developed to automatically calculate the attributes sensitive to burr formation, the monitoring system is calibrated:

• A fixed drilling process is established in which the value of the process variables is set under the conditions of production that interest the user (machine, tool, process parameters, etc.).

• The maximum permitted burr height is established based on user requirements. • A test plan is established under the conditions of the established process.

• The tests are carried out and the signal from the regulator associated with the spindle motor is captured in each of them.

• The maximum heights reached by the burr at the exit of each hole are measured by a standard direct method (roughness meter, microscope, etc.). Different levels of burr will be obtained.

• An algorithm is implemented to calculate the attributes described (N, W, H, S, M) from the signals captured in the calibration tests.

• Depending on the value of the maximum height allowed, one or more of these attributes will be due:

"If the maximum burr height requirements are not excessively rigorous, the fundamental parameter is the value of the relative minimum (N).

"If the maximum burr height requirements are very rigorous, the value of width and height of the disturbances and the slope (W, H and S) should be used. In addition, the value of the relative maximum (M), although the percentage of holes that do not meet this condition is very low.

• By comparison with the direct burr measurements in each hole, the attributes to be used are determined. • A method is designed to monitor burrs above the requirements:

"A comparison value can be established for each of the attributes chosen by different standard methods: minimum that satisfies the requirements, linear adjustment for least squares, fuzzy logic methods, etc. The burr will be acceptable if it is successively fulfilled: N <Nc , M <Mc, W <Wc, H <Ho, S> Sc, (if all attributes are not chosen, the same order is followed for the chosen ones).

"It is also possible to design and train a neural network that uses the chosen attributes as inputs, among others (it may be useful, for example, to use the process parameters as inputs in order to generalize the validity of the network to different process conditions) and The burr level will be taken as an output from the network, which can adopt various levels defined by the user's interest. Once the algorithm has been developed, it is implemented in the control. The signals are continuously captured during drilling and in the case of If any of the holes do not meet the requirements, the operator will be notified or a record will be kept to take the appropriate measures, for example, deburring only those holes with a burr height above the established requirements. Example:

• We have considered a Kennametal TF B105 drill bit with a diameter of 10mm on Al 7075-T6 aluminum plates of 12 and 25mm thicknesses. • No lubricant (dry drilling) has been used.

• The process parameter range is as follows: "Cutting speed: 150-250 m / min.

• Feed rate: 0.2-0.5 mm / rev.

• A 200% full scale has been used for the voltage signal extracted from the regulators.

• The acceptable burr height limit has been set at 1 27 microns (Hb).

• The signals with a sampling frequency of 5000 Hz have been captured. The signal has been represented as a function of the depth of the hole, that is, the time has been converted into depth (mm), taking the point where the drill bit is zero. touch the material.

• The range used to calculate the relative maximum and minimum (M and N) has been established at +/- 4mm around the exit point of the bit, equivalent to the thickness of the material. Therefore, this range includes a few millimeters before the drill bit leaves the material, the drop in voltage that coincides with the output of the tool and a section after the output. In Figure 4 this range around the "Exit point" corresponds to the "Pre-exit zone" and the "Exit zone". • The height and width of the disturbances (H and W) have been calculated in the range that goes from the "Exit point" of the bit until the head decelerates, including the recoil of the head, that is to say in the "Post- output "of Figure 4.« The slope has been adjusted by least squares in the

"Output zone", more specifically calculating the range in which the torque value decreases monotonously.

• The transformation from volts to Torque units for the machine used is: V _τ {V) - T _N {N. m)

where TN = 16.97 (N m) is the nominal torque of the machine equivalent to 5 (V) and VT is the measured voltage of the head regulator. • The established comparison values are:

"Mc = reference level + 1 (V).

A elimination algorithm has been implemented, so that they must be satisfied successively: N <Nc, M <Mc, W <Wc, H <Hc, S> Sc. If a condition is not satisfied, it is not necessary to calculate the following. With these values, the prediction capacity of the monitoring algorithm is 92%.

Figure 6 shows several examples of signals with different burr levels. a) Cutting speed = 150 m / min, feed = 0.2 mm / rev. b) Cutting speed = 150 m / min, feed = 0.3 mm / rev. c) Cutting speed = 150 m / min, feed = 0.2 mm / rev. d) Cutting speed = 1 50 m / min, feed = 0.3 mm / rev. The results obtained are as follows for each of the attributes:

Signal M N H W S HB (μm) Output

(a) 0.12 0.39 - - - 315 Bad

(b) 0.57 0.08 1.44 10.9 56 ° 148 Bad

(c) 0.31 0.03 0.52 0 35 ° 183 Bad

(d) 0.46 0.05 0.78 0 57 ° 80 OK

where HB is the burr measured in the hole and Output is the output of the monitoring algorithm.

Normally the worst levels of burr are manifested in a very irregular signal, where the minimum at output M is very high (example in Figure 6a). In that case it is no longer necessary to calculate the other attributes. Conclusions

In this invention the first method of monitoring burrs during drilling has been developed. The algorithm is based on the analysis of the signals coming from the spindle motor regulator. This facilitates and lowers the implementation of the method in the control to use it automatically. The reliability of this method is above 92% for an extensive parameter range under high speed dry drilling conditions for aluminum alloys, for example, Al 7075-T6.

Claims

1 .- Method of monitoring the formation of burrs in parts drilling processes in which a drill head is used, the head motor regulator, previously establishing a fixed drilling process in which the value is set of the variables of the process in the production conditions and among them the value of one or several speeds of advance, characterized in that in each process of drilling parts: a) the admissible height of burr is set; b) the signal associated with the torque from the head motor regulator is captured, the "cut zone" is determined in said signal between the point where the drill bit touches the input surface in the material until the drill bit is find again out of the hole after recoil of the head; c) several zones are defined within the "cutting zone": the "exit point" is established as the point at which the tip of the drill bit crosses the exit surface of the hole; the "exit zone" is established as the zone immediately after the "exit point"; the "reference level" (RL) is calculated as the average value reached by the signal in the area in which the drill bit crosses the internal section of the hole in the section corresponding to the last forward speed used; d) the relative minimum value (N) is defined as the quotient between the minimum value (Minimun) reached by a signal in the "output zone" and the "reference level" (RL): N = Minimun / RL e) the relative minimum value is calculated for the fixed process and a comparison minimum relative value (Nc) with a pre-established tolerance is established; f) the signal from the head motor regulator is captured during the industrial drilling process in production, calculated in The "cutting zone" is the relative minimum value (N) for each hole, deciding that the height of the burr is admissible if said value (N) is less than the value of the relative minimum of comparison (Nc) with the pre-established tolerance: N <Nc. 2.- Method for monitoring the formation of burrs in parts drilling processes, according to the previous claim, characterized in that in each part drilling process: a) several areas are defined within the "cutting area": the "exit point" as the point where the tip of the drill bit crosses the exit surface of the hole; the "exit zone" is established as the zone immediately after the "exit point"; a "post-exit zone" is established that successively includes the "exit zone" and the return of the bit until it is outside the hole; the "reference level" (RL) is calculated as the average value reached by the signal in the area in which the drill bit crosses the internal section of the hole in which it is approximately constant once the process variables are set; b) three fundamental magnitudes are defined: bi) the width value (W) of the disturbances whose height is above a pre-established value (which we will denote HP) that could appear in the "post-exit zone"; b2) the maximum height value (H) of the disturbances that may appear in the "post-departure zone"; D3> the slope value (S) calculated in the "exit zone"; c) the width, maximum height and slope values (W, H, S) are calculated for the fixed process, an HP value is set and a comparison value is established for each of the quantities (Wc, Hc, Sc ) with a pre-established tolerance; d) the signal from the head motor regulator is captured during the industrial drilling process in production, the value of width, maximum height and slope (W, H, S) for each hole is calculated in the "cutting zone" , deciding that the height of the burr is admissible if the preset tolerance is successively met:

3.- Method for monitoring the formation of burrs in parts drilling processes, according to previous claims, characterized in that in each part drilling process: a) several areas are defined within the "cutting area": it is established the "exit point" as the point where the tip of the drill bit crosses the exit surface of the hole; a "pre-departure zone" immediately preceding the "departure point" is established; the "reference level" (RL) is calculated as the average value reached by the signal in the area in which the drill bit crosses the internal section of the hole in which it is approximately constant once the process parameters have been set; b) the relative maximum value (M) is defined as the quotient between the maximum value (Maximun) reached by the signal in the "pre-departure zone" and the "reference level" (RL):  M = Maximun / RL c) the relative maximum value is calculated for the fixed process and a comparison relative maximum value (Mc) is established with a pre-established tolerance; d) the signal from the head motor regulator is captured during the industrial drilling process in production, the relative maximum value (M) for each hole is calculated in the "cutting zone", deciding that the height of the burr is admissible if said value (M) is less than the value of the relative minimum of comparison (Mc) with the pre-established tolerance: M <Mc. 4, - Method for monitoring the formation of burrs in parts drilling processes in which a drill head is used, the head motor regulator, previously establishing a fixed drilling process in which the value is set of the process variables in the production conditions, characterized in that in each part drilling process: a) the admissible height of the burr is set; b) the signal associated with the torque from the head motor regulator is captured, the "cut zone" is determined in said signal between the point where the drill bit touches the input surface in the material until the drill bit is find again out of the hole after recoil of the head; c) several zones are defined within the "cutting zone": the "exit point" is established as the point at which the tip of the drill bit crosses the exit surface of the hole; the "exit zone" is established as the zone immediately after the "exit point"; the "reference level" (RL) is calculated as the average value reached by the signal in the area in which the drill bit crosses the internal section of the hole in the section corresponding to the last forward speed used; d) the relative minimum value (N) is defined as the quotient between the minimum value (Minimun) reached by a signal in the "output zone" and the "reference level" (RL): N = Minimun / RL e) the relative minimum value N is calculated; f) a neural network is designed and trained that uses the magnitude N defined in 1 d) as an input, the level of burr will be established as an output of the network, which may adopt different levels of burr defined by the interest of the user ; g) the signal from the head motor regulator is captured during the industrial drilling processes in production, the value of the magnitudes that are used as inputs of the neural network is calculated for each hole, the output of the neural network will indicate the level burr. 5.- Method for monitoring the formation of burrs in parts drilling processes, according to claim 4, characterized in that in each part drilling process: a) several zones are defined within the "cutting zone": the "exit point" is established as the point at which the tip of the drill bit crosses the exit surface of the hole; the "exit zone" is established as the zone immediately after the "exit point"; a "post-exit zone" is established that successively includes the "exit zone" and the return of the bit until it is outside the hole; the "reference level" (RL) is calculated as the average value reached by the signal in the area in which the drill bit crosses the internal section of the hole in which it is approximately constant once the process variables are set; b) three fundamental magnitudes are defined: bi) the width value (W) of the disturbances whose height is above a pre-established value (which we will denote HP) that could appear in the "post-exit zone"; b2) the maximum height value (H) of the disturbances that may appear in the "post-departure zone"; b3) the slope value (S) calculated in the "exit zone"; c) a neural network is designed and trained that uses the magnitudes W, H, S defined in 2d as inputs, the level of burr will be established as an output of the network, which may adopt different levels of burr defined by the interest of the user; d) the signal of the head motor regulator is captured during the industrial drilling processes in production, the value of the magnitudes that are used as inputs of the neural network is calculated for each hole, the output of the neural network will indicate the level burr. 6.- Method for monitoring the formation of burrs in parts drilling processes, according to claims 4 and 5, characterized in that in each part drilling process: a) several areas are defined within the "cutting area": the "exit point" is established as the point at which the tip of the drill bit crosses the exit surface of the hole; a "pre-departure zone" immediately preceding the "departure point" is established; the "reference level" (RL) is calculated as the average value reached by the signal in the area in which the drill bit crosses the internal section of the hole in which it is approximately constant once the process parameters have been set; b) the relative maximum value (M) is defined as the quotient between the maximum value (Maximun) reached by the signal in the "pre-departure zone" and the "reference level" (RL):  M = Maximun / RL c) a neural network is designed and trained that uses the magnitude M defined in 3d as an input), the burr level will be established as an output of the network, which may adopt different burr levels defined by the interest of the user; d) the signal of the head motor regulator is captured during the industrial drilling processes in production, the value of the magnitudes that are used as inputs of the neural network is calculated for each hole, the output of the neural network will indicate the level burr.