DEVICE AND METHOD FOR DRILLING WITH AUTOMATIC DRILLING PARAMETERS ADAPTATION

Abstract

A drilling machine and a drilling method including drilling a first bore in a material with a drilling machine by applying a torque to a drilling tool for imparting a rotation at a first rotational speed to the drilling tool, and applying a thrust to the drilling tool for advancing the drilling tool at a first feed speed into the material, wherein a drilling parameter is measured while drilling the first bore, and a second rotational speed and a second feed speed are determined based on the drilling parameter, then drilling a second bore at the second rotational speed and at the second feed speed.

Claims

1. A drilling method comprising: drilling at least one first bore in a material with a drilling machine by: (i) applying a torque to a drilling tool to impart a rotation at a predetermined first rotational speed to the drilling tool, and (ii) applying a thrust to the drilling tool to advance the drilling tool at a predetermined first feed speed into the material, measuring at least one drilling parameter representative of at least one of the torque and the thrust while drilling the at least one first bore, determining at least one of a second rotational speed and a second feed speed based on the at least one drilling parameter measured while drilling the at least one first bore, and drilling a second bore after the drilling of the at least one first bore, by applying at least one of: (i) a torque to the drilling tool to impart rotation at the second rotational speed to the drilling tool, and (ii) a thrust to the drilling tool to advance the drilling tool at the second feed speed into the material.

2. The drilling method according to claim 1, wherein a first drilling parameter of the at least one drilling parameter is an electrical current supplied to an electrical motor of the drilling machine adapted to impart torque to the drilling tool.

3. The drilling method according to claim 1, wherein a second drilling parameter of the at least one drilling parameter is an electrical current supplied to an electrical motor of the drilling machine adapted to impart thrust to the drilling tool.

4. The drilling method according to claim 1, further comprising acquiring drilling values for a drilling parameter of the at least one drilling parameter while drilling a single bore of the at least one first bore.

5. The drilling method according to claim 1, further comprising acquiring drilling values for a drilling parameter of the at least one drilling parameter while drilling multiple ones of the at least one first bore.

6. The drilling method according to claim 5, further comprising determining at least one of the second rotational speed and the second feed speed based on the drilling values acquired from the multiple ones of the at least one first bore.

7. The drilling method according to claim 1, further comprising: mounting a new drilling tool in the drilling machine, and drilling a first series of bores using the new drilling tool in the drilling machine by applying a torque to the new drilling tool to impart rotation at the second rotational speed to the new drilling tool, and (ii) a thrust to the new drilling tool to advance the new drilling tool at the second feed speed.

8. The drilling method according to claim 1, wherein the determining at least one of the second rotational speed and the second feed speed is performed in response to fulfilment of a predetermined criteria of the operation of the drilling tool.

9. The drilling method according to claim 1, wherein a value of the second feed speed is lower than a value of the first feed speed.

10. The drilling method according to claim 1, wherein the second feed speed is proportional to the second rotational speed.

11. A drilling machine comprising: a drilling tool, a torque motor adapted to apply a torque to the drilling tool to rotate the drilling tool at a predetermined rotational speed, a thrust motor adapted to apply a thrust to the drilling tool to advance the drilling tool at a predetermined feed speed into a material, a control unit adapted to control the rotational speed of the drilling tool and the feed speed of the drilling tool, a drilling sensor adapted to measure a drilling parameter representative of at least one of the torque applied to the drilling tool by the torque motor, and the thrust applied to the drilling tool by the thrust motor, and a processing unit adapted to calculate at least one of a rotational speed for the drilling tool and a feed speed for the drilling tool based at least on the drilling parameter measured by the drilling sensor.

12. The drilling machine according to claim 11, wherein the drilling sensor is adapted to measure an electrical current supplied to the torque motor or to the thrust motor, and the drilling parameter is related to the electrical current.

13. A drilling method comprising: drilling a first bore with a drilling tool driven by a drilling machine that includes a torque motor rotates the drilling tool at a first rotational speed to form the first bore, and an advancement motor that advances the drilling tool at a first feed speed to form the first bore; measuring an electrical current during the drilling of the first bore applied to at least one of the torque motor and the advancement motor; calculating a value representative of current consumed by at least one of the torque motor and the advancement motor to perform the drilling of the first bore; calculating a second rotational speed or a second feed speed based on the value, and drilling a second bore using the drilling tool in the machine, wherein the torque motor rotates the drilling tool at the second rotational speed and the advancement motor advances the drilling tool at the second feed speed.

14. The drilling method of claim 13, further comprising: measuring an electrical current during the drilling of the second bore applied to at least one of the torque motor and the advancement motor; calculating a second value representative of current consumed by at least one of the torque motor and the advancement motor during performance of the drilling of the second bore; calculating a third rotational speed or a third feed speed based on the second value, and drilling a third bore using the drilling tool in the machine, wherein the torque motor rotates the drilling tool at the third rotational speed and the advancement motor advances the drilling tool at the third feed speed.

15. The drilling method of claim 13, wherein: the calculation of the value representative of the current includes integration of the current applied to the torque motor during the drilling of the first bore, or integration of the current applied to the advancement motor during the drilling of the first bore; and the calculation of the second rotational speed is based on the integration of the current applied to the torque motor, and the calculation of the second feed speed in based on the integration of the current applied to the feed motor.

16. The drilling method of claim 13, wherein: the measuring of the electrical current during the drilling of the first bore includes measuring the electrical current applied to the torque motor and the current applied to the advancement motor; the calculation of the value representative of the current includes integration of the current applied to the torque motor during the drilling of the first bore, and integration of the current applied to the advancement motor during the drilling of the first bore; and the calculation of the second rotational speed is based on the integration of the current applied to the torque motor, and the calculation of the second feed speed in based on the integration of the current applied to the feed motor.

17. The drilling method according to claim 13, wherein a first drilling parameter of the at least one drilling parameter is an electrical current supplied to an electrical motor of the drilling machine adapted to impart torque to the drilling tool.

18. The drilling method according to claim 13, further comprising: mounting a new drilling tool in the drilling machine, and drilling a first series of bores using the new drilling tool in the drilling machine by applying: (i) a torque to the new drilling tool to impart rotation at the second rotational speed to the new drilling tool, or (ii) a thrust to the new drilling tool to advance the new drilling tool at the second feed speed.

19. The drilling method according to claim 13, wherein a value of the second feed speed is lower than a value of the first feed speed.

20. The drilling method according to claim 13, wherein the second feed speed is proportional to the second rotational speed.

Description

SUMMARY OF DRAWINGS

[0069] Some specific exemplary embodiments and aspects of the invention are described in the following description in reference to the accompanying figures.

[0070] FIG. 1 is a schematic representation of steps of an embodiment of a drilling method according to the invention.

[0071] FIG. 2 is a schematic representation of a measurement of a drilling parameter while drilling a bore.

[0072] FIG. 3 is a schematic representation of processed measurements of a drilling parameter when drilling multiple successive bores.

[0073] FIG. 4 is a schematic representation of comparative measurements of a parameter of drilled bores.

[0074] FIG. 5 is a schematic representation of a drilling machine according to the invention.

DETAILED DESCRIPTION

[0075] In FIG. 1, illustrates a drilling method which embodies the invention. This method can be implemented on a drilling machine as represented on FIG. 5, with a drilling tool (or drill bit) 31 for drilling a predetermined material. The drilling machine 30 comprises a torque motor 32 adapted to impart a torque to the drilling to make rotate the drilling tool. The drilling machine 30 further comprises a thrust motor 33 adapted to impart an axial thrust to the drilling tool 31 to make advance the drilling tool, or at least a forward tip of the tool, towards and into the material to be drilled. The drilling machine may further comprise a control unit 34 adapted to control the rotation motor and the feed motor.

[0076] Moreover, the drilling machine 30 comprises a torque sensor 35 adapted to measure the electrical power supplied to the torque motor 32. The drilling machine 30 also comprises a thrust sensor 36 adapted to measure the electrical power supplied to the thrust motor 33. The torque sensor 35 and the thrust sensor 36 may for example be ammeters which measure electrical current such as in amperes. The torque and thrust sensors 35, 36 may be incorporated respectively with the torque motor 32 and the thrust motor 33. The sensors 35, 36 may be incorporated at other positions in other embodiments, for example in the control unit 34.

[0077] The control unit 34 may also comprise a processing unit 37 to process signals obtained from the sensors 35, 36 to implement a method such as shown in FIG. 1. The processing unit 37 may include memory storing instructions to perform the method and store data such as measurements obtained from the signals from the sensors 35, 36, values of rotational speeds to be applied to a drilling tool and values of feed speeds to be applied to the drilling tool

[0078] In step 11, set values of a first rotational speed and a first feed speed are determined. These set values may be determined based on experience or experiment. The set values may be determined by testing in laboratory. These set value may be provided by a manufacturer of the drilling tool used. In step 11, the set values are entered into the control unit,

[0079] In step 12, which follows step 11, a bore is drilled in the material at the rotational speed and feed speed determined in step 11. The electrical currents supplied to the rotation motor and feed motor are measured, e.g. by sensors 35, 36, and recorded by the control unit. As previously mentioned, the electrical current consumed by the rotation motor and the feed motor is representative of respectively of the torque and of the thrust applied to the drilling tool. In this embodiment, the electrical current measured while drilling the bore is measured during the whole length of the drilling step.

[0080] An exemplary result the measurement made in step 12 is represented on FIG. 2. Drilling values made of electrical current supplied to the feed motor while drilling a first bore are represented on the y axis. These drilling values are therefore representative of the instantaneous thrust applied to the drilling tool. The x axis represents the axial displacement of the drilling tool towards or in the material (or feed) in millimeters during this process. In particular, one may observe the feed at which the drilling tool's end first touches the material's surface, at about 14 mm, by a sudden increase of electrical current supplied to the rotation motor. One may also observe the feed at which the drilling tool's end exits the material, at about 58 mm, by a sudden drop of electrical current supplied to the rotation motor. The total feed stroke set for this drilling process would be about 63 mm. While drilling the first bore, the drilling values are within a range of 0.4-0.6, with a slight increase towards the end of the bore drilling (from 50 mm to 58 mm). These drilling values may be acquired by an ammeter, sent to a processing unit 37 of the drilling machine, and stored in a long-term or short-term memory.

[0081] In a third step 13 following step 12, a work value is calculated which is representative of a mechanical work developed to drill the first bore. A work value may be calculated for the rotation motor, and for the feed motor. The work value may be obtained by integration of the drilling values 18 acquired during step 2. The work values are calculated by the processing unit of the drilling machine based on the drilling values acquired during step 12 and as exemplarily represented in FIG. 2. The work values are stored in a long-term or short-term memory.

[0082] In a fourth step 14, the number of bores made with the drilling machine is compared with a predetermined number of first bores stored in a memory. Indeed, in some methods according to the invention, an initial series of first bores is made with a drilling tool in order to obtain sufficient initial data to adapt the rotational speed and feed speed for further drilling. As long as the number of bores drilled is inferior to the predetermined number of first bores, the steps 12, 13, 14 are repeated. A plurality of work values is thus stored in memory.

[0083] In FIG. 3, multiple work values 19 are represented in dotted lines for successive bores drilled with a same drilling tool. These work values are represented along the y axis and are representative of the total thrust obtained for the drilling stage of each bore. The successive bores drilled are numbered in their drilling order, and this numbering is reflected on the x axis. In this example a hundred and forty successive bores were made. One may observe on this graphic that the mechanical work developed for the thrust of the drilling tool increases with the number of bores drilled with a same drilling tool. In the example shown in FIG. 3, the predetermined number of first bores from an initial series without modification of the rotational speed and/or feed speed between consecutive bores is of about five. Bores drilled after that number have therefore been made with adjusted rotational speed and/or feed speed.

[0084] When the number of bores drilled reaches the predetermined number of first bores, the step 15 is implemented.

[0085] In step 15, the processing unit 37 processes the work values obtained at step 13, and determines a second rotational speed and/or a second feed speed. In the exemplary embodiment of method described in relation to the figures, the processing unit implements a linear regression, for example with a best-fitting linear algorithm, to evaluate a slope of the successive work values. This best-fitting linear algorithm may be applied to a selection of work values (for example to exclude incoherent values), and/or on a predetermined set of values (such as for example on the last thirty work values), and/or to all values since the first bore drilled with the same drilling tool. In particular, the processing unit may select a range of work value among the latest acquired (for example the latest twenty work values) when a curve inflection is detected. The processing unit may thus first apply a curvilinear best-fitting algorithm to select a proper range of value to be processed for determining a line and its slope. Alternatively, a user may determine an arbitrary number of work values to be taken into account for applying a linear regression.

[0086] In this embodiment, step 15 allows to obtain a line with a slope. This line 20 is represented with a solid line in FIG. 3.

[0087] In step 16 following step 15, the slope of the line obtained in step 15 is extracted. The slope of the line obtained as a linear regression of the successive work values is called in the whole text “adaptive factor”.

[0088] In step 17 following step 16, the processing unit 37 computes a second rotational speed and a second feed speed. The processing unit then replaces the first rotational speed stored in a memory with the second rotational speed and/or replaces the first feed speed stored in a memory with the second feed speed. The controller of the drilling machine will thus use this new set of rotational speed and feed speed as setpoint when drilling the subsequent bore.

[0089] When the adaptive factor is negative or stable, no change is made to the rotational speed and the feed speed. The second rotational speed may be equal to the first rotational speed and the second feed speed is equal to the first feed speed.

[0090] When the “adaptive factor” obtained is positive, at least one of the rotational speed and the feed speed may be reduced based on a function of an integral of the current over the course of a drilling process applied to at least one of the torque motor and the advancement motor.

[0091] By reducing the rotational spend or the feed speed for subsequent bores, the wear of the drilling tool is reduced and its life-span is extended.

[0092] Other parameters than the adaptive factor may be taken into account to modify the rotational speed and/or feed speed from one bore to another. For example, if the torque or thrust, e.g., the current applied to the thrust and advancement motors, measured during the drilling of a bore (measurement corresponding to FIG. 2) were to exceed a threshold—and more particularly if they were to briefly peak—the rotational speed and/or feed speed may be adapted consequently to avoid to reach such high values of torque or thrust when drilling the subsequent bore. In concrete terms, in such cases the rotational speed and/or feed speed may be reduced for drilling the following bore, even if the adaptive factor is negative or stable. The maximum torque and maximum thrust attained during the drilling of a bore may thus be maintained within acceptable values, such that the risk of breaking the material or the drilling tool is also reduced.

[0093] Moreover, the reduction in rotational speed and/or feed speed when the maximum torque or maximum thrust is high, or when the work required to drill successive bores is increasing, allows to maintain the same quality of the drilling step and thereby of the resulting bore, even with a worn drilling tool.

[0094] FIG. 4 shows results obtained by drilling successive bores in different conditions. On the x axis, the bores numbering is represented. On the y axis the diameter of the bores is represented as representative of the quality and homogeneity of the bores. No numbers are indicated on the y axis as the value is not relevant, but rather the variation from one bore to another.

[0095] The curves 41 and 42 were obtained by drilling bores in a titanium alloy. The curve 41 has been obtained by making use of a method according to the invention in which the rotational speed and/or feed speed is adapted from bore to bore, based on data obtained from previous bores made with the same drilling tool. On the contrary, curve 42 has been obtained by drilling bores with set rotational speed and set feed speed without variation from bore to bore. One may observe that the variation in the bores' diameters is much more limited when a method according to the invention is applied compared to when it is not: the curve 41 is “flatter” than the curve 42.

[0096] The curves 43 and 44 were obtained by drilling bores in an aluminum alloy. Similarly, the curve 43 has been obtained by making use of a method according to the invention in which the rotational speed and/or feed speed is adapted from bore to bore, based on data obtained from previous bores made with the same drilling tool. On the contrary, curve 44 has been obtained by drilling bores with set rotational speed and set feed speed without variation from bore to bore. One may observe that the variation in the bores' diameters is much more limited when a method according to the invention is applied compared to when it is not: the curve 43 is “flatter” than the curve 44.

[0097] Similar quality and homogeneity of multiple successive bores made with the same drilling tool by using a drilling method and a drilling machine according to the invention have also been measured and observed as regards to other parameters of the bores such as burr height, roughness, etc.

[0098] After step 17, the process continues for drilling further bores by following again the steps sequence 12 to 17 (excluding step 14).

[0099] In a method according to the invention, the drilling values and work values are reset each time a new drilling tool is mounted on the drilling machine.

[0100] While at least one exemplary embodiment of the present invention(s) is disclosed herein, it should be understood that modifications, substitutions and alternatives may be apparent to one of ordinary skill in the art and can be made without departing from the scope of this disclosure. This disclosure is intended to cover any adaptations or variations of the exemplary embodiment(s). In addition, in this disclosure, the terms “comprise” or “comprising” do not exclude other elements or steps, the terms “a” or “one” do not exclude a plural number, and the term “or” means either or both. Furthermore, characteristics or steps which have been described may also be used in combination with other characteristics or steps and in any order unless the disclosure or context suggests otherwise. This disclosure hereby incorporates by reference the complete disclosure of any patent or application from which it claims benefit or priority.