Drilling method for a workpiece, especially one with curved surface(s), with adjustment of the position of machining tools of a robot effector relative to the workpiece, individual non-contact measurement by laser of each tool.

Abstract

A method for drilling a workpiece, particularly one with curved surface(s), with adjustment of the position of machining tools of a robot end effector relative to the workpiece by individual non-contact laser measurement of each tool. The invention essentially consists of a method for drilling a workpiece, particularly one with curved surface(s), using drilling tools mounted in a robot end effector, which implements tool positioning steps based on laser distance sensor detection, without contact with the workpiece, instead of mechanical probes according to the prior art.Laser sensors reduce approach and clearance distances, as well as signal processing times, for the simultaneous positioning of drilling tools. Furthermore, the detections provided by the laser sensors allow for the dynamic adjustment of the axis and drilling tool guard positions relative to the actual curvature of the workpiece. See Figure 4 for abbreviations.

Description

Title of the invention: Method for drilling a workpiece, in particular with curved surface(s), with adjustment of the position of machining tools of a robot effector relative to the workpiece by individual non-contact laser measurement of each tool. technical field

[0001] The present invention relates to the field of drilling composite materials, aluminum, steel, and superalloy, and more particularly to drilling parts intended for aeronautical use, especially sound traps.

[0002] The invention aims primarily to provide a reliable and easy solution enabling a gain in drilling productivity.

[0003] Although described with reference to a preferred application of drilling a sound trap, by means of a multi-spindle effector, the invention applies to drilling any part with a robot effector.

[0004] The multi-spindle end effector can be an end effector of any robot, in particular a single- or multi-axis articulated arm and / or a Cartesian robot. Previous technique

[0005] A sound trap, also called a silencer or noise attenuator, is a device that captures sounds in an airflow and reduces the amplitude of the acoustic waves.

[0006] Sound traps, which are implemented in particular on aeronautical parts, are made by drilling areas in parts which can be made of composite material, aluminum, steel, and superalloy, according to specific patterns, determined by acousticians.

[0007] These patterns must first of all respect a percentage of openness which is the ratio between open surface and closed surface.

[0008] This ratio is directly related to the hole diameter and the distance between the holes.

[0009] Increasingly stringent constraints on aircraft noise reduction lead to: - introduce the acoustic reduction function on as many parts as possible, resulting in an increase in the number of part references, - to have significant variability in the definition of acoustic patterns.

[0010] To date, mechanical drilling technology is recognized and approved for carrying out these drillings.

[0011] For drilling sound traps, robotic arms or 5-axis machines carrying A head, also called a multi-spindle effector, incorporating drilling tools (spindles and cutting tools) arranged in line or according to a matrix, is generally used to perform simultaneous multi-drilling.

[0012] Acoustic studies demonstrate improved noise reduction by modifying the sound trap designs to maintain the same percentage of opening but with a significantly reduced hole diameter. The trend is to decrease the diameter by a factor of at least 2.

[0013] Dividing the diameter by 2 implies a number of drillings to be carried out 4 times higher and therefore 4 times more production time.

[0014] There is therefore an issue of increasing productivity, which implies drilling faster and more holes at the same time.

[0015] In the general drilling process, a relatively large amount of time is devoted to knowing the approach and clearance distances of the end effector with respect to the surface of the workpiece to be machined.

[0016] Indeed, to date, this knowledge is exclusively achieved by implementing a mechanical probing of the part using a pusher probe equipped with a contact sensor, notably described in patent FR3001645B1.

[0017] In addition to the considerable time required for probing, a mechanical probe occupies a significant amount of space around a drilling spindle. This space requirement is multiplied on the scale of a multi-spindle end effector.

[0018] There is therefore a need to speed up the operations of knowledge of the approach and clearance distances of an effector, in particular multi-spindle, in a drilling process of a workpiece, in particular with curved surface(s), such as a sound trap.

[0019] The aim of the invention is to meet at least part of this need. Description of the invention

[0020] To this end, the invention relates, in one of its aspects, to a method for drilling a workpiece, in particular one with curved surface(s), using drilling tools mounted in a robot end effector, the method comprising the following steps:

[0021] i / approach of the robot end effector with positioning of the axis (Z) of its center orthogonal to a surface point of the part predetermined by calculation, and positioning of each drilling tool at a distance, called approach guard (Ga), from a surface point of the part predetermined by calculation,

[0022] ii / advance of the axis (Z) to a distance called close guard (Gr) predetermined by calculation,

[0023] iii / once the close guard (Gr) is reached, the axis (W) of each drilling tool is set in motion at a predetermined feed rate (Vr),

[0024] iv / advance of each axis (W) of the drilling tool at the feed rate (Vr) up to a distance, called drilling guard (Gp), detected by each of the laser distance sensors and recorded,

[0025] v / once the drilling guard (Gp) is reached, change the feed rate of each drilling tool from speed Vr to a feed rate (Vt), called the working rate,

[0026] vi / drilling, simultaneous or not, of the workpiece by all the drilling tools at the working speed (Vt),

[0027] vii / removal, simultaneous or not, of all the drilling tools from the workpiece,

[0028] viii / raising of the drilling tools and return for each of them to a distance called safety guard (Gs) determined from the drilling guard (Gp) of each axis recorded in step iv / by each of the laser distance sensors.

[0029] Advantageously, the method includes, before step i / , a preliminary step of positioning each axis (W) of drilling tool, predetermined by calculation taking into account the surface of the workpiece to be machined.

[0030] According to an advantageous embodiment, the process includes a step of moving the effector to position it at another point of the workpiece, then repeating steps i / to viii / .

[0031] According to this mode, the effector is preferably that of a six-axis robot or a Cartesian robot with three linear movement axes, two rotary movement axes and one drilling axis, the movement including the movement of the effector along at least one of the six axes or the drilling axis respectively.

[0032] The process may include one or more of the following advantageous features:

[0033] - the approach guard (Ga) is less than or equal to 20 mm;

[0034] - the close guard (Gr) is less than or equal to 10 mm;

[0035] - the drilling guard (Gp) is less than or equal to 0.5 mm;

[0036] - the safety guard (Gs) is equal to the drilling guard (Gp) plus a margin of security.

[0037] According to an advantageous embodiment, the rising edge of the on / off (NOT) signal for laser distance sensor detection of the drill guard (Gp) in step iv / is directly fed to an input of the drill tool's speed controller. This embodiment eliminates the processing time of a numerical control and its PLC. Thus, the process exhibits improved responsiveness.

[0038] Advantageously, step vii / of withdrawal is carried out when the end of drilling is detected by a system for monitoring the consumption of drilling tools.

[0039] The invention also relates to a multi-pin robot end effector, in particular intended to implement the process as described above, comprising:

[0040] - a body,

[0041] - a number n of drilling tools mounted in the body forming a matrix,

[0042] - a number n of laser distance sensors, each arranged near a tool drilling, to individually detect at least one distance (Gp) between the free end of a drilling tool and a point on a workpiece.

[0043] According to an advantageous embodiment, the effector comprises a number n of linear motors, each adapted for advancing or retracting a drilling tool.

[0044] The invention also relates to the use of the method and / or effector described above for machining an aeronautical part, in particular a sound trap.

[0045] The invention finally relates to a part, in particular an aeronautical part, machined according to the process as described above.

[0046] Thus, the invention essentially consists of a method for drilling a workpiece, in particular with curved surface(s), using drilling tools mounted in a robot effector, which implements tool positioning steps based on laser distance sensor detection, without contact with the workpiece, instead of mechanical probes according to the state of the art.

[0047] Laser sensors make it possible to reduce approach and clearance distances as well as signal processing times for the simultaneous positioning of drilling tools

[0048] In addition, with the detections made by the laser sensors, this makes it possible to dynamically reappropriate the guard positions of the axes and drilling tools in relation to the actual curvature of the workpiece.

[0049] In conclusion, the invention offers numerous advantages over prior art methods, including: - a reduction in machining time for a part, particularly one with a curved surface, - an increase in the compactness of drilling tools due to the implementation of laser distance sensors which are less bulky than mechanical probes according to the state of the art and therefore an increase in the density of drilling tools on a given surface.

[0050] Other advantages and features of the invention will become clearer from the detailed description of examples of implementation of the invention given by way of illustration and not limitation with reference to the following figures. Brief description of the drawings

[0051] [Fig. 1] [Fig. 1] is a longitudinal cross-sectional view of an example of a part of a multi-spindle effector equipped with a mechanical probe around a spindle, according to the state of the art.

[0052] [Fig.2] [Fig.2] is a schematic cross-sectional view of the multi-spindle effector with mechanical probes, showing the return positioning of the spindles once drilling of a part with a curved surface has been carried out, according to the state of the art.

[0053] [Fig.3] [Fig.3] is a longitudinal sectional view of an example of a part of a multi-pin effector equipped with a laser distance sensor around a pin, according to the invention.

[0054] [Fig.4] [Fig.4] is a schematic cross-sectional view of the multi-spindle laser distance sensor effector, showing the return positioning of the pins once drilling of a part with a curved surface has been carried out, according to the invention. Detailed description

[0055] Throughout this application, the terms "front" and "rear" are to be understood by reference to a multi-spindle effector according to the invention in operating configuration, with the drilling tool at the front.

[0056] Figure [1] shows part of a multi-pin effector 1 showing a pin 10 with a mechanical probe 11 according to the state of the art.

[0057] This effector 1 is more particularly intended to carry out the drilling of small diameter holes, typically from 0.5 to 2 mm, in a part P intended for acoustic attenuation, such as a sound trap.

[0058] The mechanical probe 11 allows the actual step of drilling a hole by the spindle 12 to be initiated.

[0059] The drilling process with such an effector 1 according to the state of the art can be summarized as follows.

[0060] An approach to the end effector 1 is made using the 6 axes of a robot carrying the end effector. This approach is made until the end effector 1 is at a predefined distance from the part P to be drilled.

[0061] The actual drilling by a spindle 10 is carried out after the probe 11 is in physical contact with the part P.

[0062] At the end of the drilling, the set of pins 10 move back a predefined distance, before starting the next drilling, i.e. at another location on the part P.

[0063] If the drilling itself is satisfactory, the time required to implement the mechanical probing is relatively important.

[0064] Furthermore, as can be seen from [Fig.1], a mechanical probe 11, even well integrated into an effector 1, occupies a considerable space around the spindle 10. And therefore, the number of spindles 10 for a given surface of part P to be drilled is constrained by the cumulative space taken up by all the mechanical probes 11.

[0065] Furthermore, as illustrated in [Fig. 2], the step of raising the pins 10 according to the prior art method is not perfect, particularly when the surface of the part P is curved. The pins 10 may rise following not the actual curve of the part P but the previously calculated curve, which therefore does not perfectly match the actual curve.

[0066] To overcome the disadvantages of this process according to the state of the art with mechanical probes 11, the inventors judiciously thought of implementing a drilling process by implanting laser distance sensors 100 in place of the probes.

[0067] Fig. 3 shows part of a multi-pin effector 1 with a laser distance sensor 100 fixed next to a pin 10. Each of the pins 10 is equipped with at least one laser distance sensor 100.

[0068] The drilling process according to the invention comprises the following steps.

[0069] It is specified that the Z axis is the feed axis normal to the part P to be drilled and that this The advance is managed by the robot carrying effector 1.

[0070] The W axis is the normal feed axis to the workpiece P and this feed is controlled by the effector 1.

[0071] Step 0 / : the positioning of each axis (W) of the drilling tool is carried out, predetermined by calculation taking into account the theoretical curvature of the surface of the workpiece P to be machined.

[0072] Step i: The robot end effector is approached with its axis (Z) positioned orthogonally from its center to a predetermined surface point of the workpiece, and each drilling tool is positioned at a distance, called the approach clearance (Ga), from a predetermined surface point of the workpiece. Preferably, the approach clearance (Ga) is less than or equal to 20 mm.

[0073] Step ii: The axis (Z) is advanced to a distance called the close guard (Gr), predetermined by calculation. Preferably, the close guard (Gr) is less than or equal to 10 mm.

[0074] Step iii / once the close guard (Gr) is reached, the axis (W) of each drilling tool is set in motion at a predetermined feed rate (Vr),

[0075] Step iv / Each axis (W) of the drilling tool is then advanced at the feed rate (Vr) to a distance, called the drilling clearance (Gp), detected by each of the laser distance sensors 100. This drilling clearance (Gp) is then recorded. Preferably, the drilling clearance (Gp) is less than or equal to 0.5 mm.

[0076] Advantageously, the rising edge of the on / off (TOR) signal from the laser distance sensor detection of the drill guard (Gp) according to step iv / is directly on an input of the drill tool's speed controller. This saves time for starting up the next step v / .

[0077] Step v / : once the drilling guard (Gp) is reached, a speed change is made advance of each drilling tool from the speed Vr to a feed speed (Vt), called working speed.

[0078] Step vi / : the drilling, simultaneous or not, of the part P is then carried out by the set of drilling tools 12 at the working speed (Vt).

[0079] Step vii / : once the desired drilling has been carried out, the drilling tools 10, 12 are withdrawn from part P, simultaneously or not. This withdrawal step is advantageously carried out when the end of drilling is detected by a system for monitoring the consumption of the drilling tools 10, 12.

[0080] Step viii / : the drilling tools are then raised and returned for each of them to a distance called the safety guard (Gs) determined from the drilling guard (Gp) of each axis recorded in step iv / by each of the laser distance sensors 100. Preferably, the safety guard (Gs) is equal to the drilling guard (Gp) plus a safety margin.

[0081] Thanks to this laser detection which is individualized for each of the pins 10 and which is recorded, the raising of the pins 10 takes place according to a curve Cl which perfectly follows the actual curvature of the part as illustrated in [Fig.4].

[0082] Other variants and improvements may be envisaged without departing from the scope of the invention.

[0083] If in the illustrated example the laser distance sensor 100 is arranged next to a spindle, it can also be considered to integrate it into its body, i.e. right next to the drilling tool housing.

Claims

Demands

1. A method for drilling a workpiece, particularly one with curved surface(s), using drilling tools mounted in a robot end effector, the method comprising the following steps: i / approach of the robot end effector with positioning of the axis (Z) from its center orthogonal to a point on the surface of the workpiece predetermined by calculation, and positioning of each drilling tool at a distance, called the approach guard (Ga), from a point on the surface of the workpiece predetermined by calculation, ii / advance of the axis (Z) to a distance called the close guard (Gr) predetermined by calculation, iii / once the close guard (Gr) is reached, movement of the axis (W) of each drilling tool at a predetermined feed rate (Vr), iv / advance of each axis (W) of the drilling tool at the feed rate (Vr) to a distance, called the drilling guard (Gp), detected by each of the laser distance sensors and recorded, v / once the drilling guard (Gp) is reached,change in feed rate of each drilling tool from speed Vr to a feed rate (Vt), called the working speed, vi / drilling, simultaneous or not, of the workpiece by all the drilling tools at the working speed (Vt), vii / withdrawal, simultaneous or not, of all the drilling tools from the workpiece, viii / raising of the drilling tools and return for each of them to a distance called the safety guard (Gs) determined from the drilling guard (Gp) of each axis recorded in step iv / by each of the laser distance sensors.

2. Method according to claim 1, comprising before step i / , a preliminary step of positioning each axis (W) of drilling tool, predetermined by calculation taking into account the surface of the workpiece to be machined.

3. Method according to claim 1 or 2, comprising a step of moving the effector to position it at another point of the workpiece, then repeating steps i / to viii / .

4. The method according to claim 3, the effector being that of a six-axis robot or a Cartesian robot with three linear axes, two rotary axes, and one drilling axis, the movement

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14. including the movement of the effector along at least one of the six axes or the drilling axis. Method according to any one of the preceding claims, the approach guard (Ga) being less than or equal to 20 mm. Method according to any one of the preceding claims, the close guard (Gr) being less than or equal to 10 mm. Method according to any one of the preceding claims, the drilling guard (Gp) being less than or equal to 0.5 mm. A method according to any one of the preceding claims, wherein the safety guard (Gs) is equal to the drilling guard (Gp) plus a safety margin. A method according to any one of the preceding claims, wherein the rising edge of the on / off (ON / OFF) signal from the laser distance sensor detecting the drilling guard (Gp) according to step iv / is directly applied to an input of the drill tool's speed controller. A method according to any one of the preceding claims, step vii / of withdrawal being carried out when the end of drilling is detected by a system for monitoring the consumption of drilling tools. A multi-spindle robot effector, in particular intended to implement the method according to one of the preceding claims, comprising: - a body, - a number n of drilling tools mounted in the body forming a matrix, - a number n of laser distance sensors, each arranged near a drilling tool, to individually detect at least one distance (Gp) between the free end of a drilling tool and a point on a workpiece. Multi-spindle effector according to claim 11, comprising a number n of linear motors each adapted for advancing or retracting a drilling tool. Use of the method according to any one of claims 1 to 10 and / or of the effector according to claim 11 or 12 for machining an aeronautical part, in particular a sound trap. Part, in particular an aeronautical part, machined according to the process according to any one of claims 1 to 10.

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