Method of 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, individual measurement without contact by laser of each tool.

Abstract

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 individual measurement without contact by laser of each tool. The invention essentially consists of a method for drilling a workpiece, in particular with curved surface(s), by means of drilling tools mounted in a robot effector, which implements steps of positioning the tools from detection laser distance sensors, without contact with the workpiece, instead of mechanical probes according to the state of the art.Laser sensors allow to reduce approach and clearance distances as well as signal processing times for simultaneous positioning of drilling tools. In addition, with the detections carried out by laser sensors, this allows to dynamically reappropriate the guard positions of the axes and drilling tools in relation to the actual curvature of the workpiece. Figure for the abstract: Fig. 4.

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, individual measurement without contact by laser of each tool. Technical field

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

[0002] The invention aims mainly to propose a reliable and easy solution allowing a gain in drilling productivity.

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

[0004] The multi-spindle effector can be an effector of any robot, in particular an articulated arm with one or more axes and / or a Cartesian robot. Prior art

[0005] A sound trap, also called a silencer or noise attenuator, is a device for capturing sounds in an air flow and attenuating the amplitude of the acoustic waves.

[0006] Sound traps, which are used 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 firstly respect an opening percentage 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] The increasingly drastic constraints on aircraft noise reduction lead to: - introduce the acoustic reduction function on a maximum number of parts, which results in an increase in the number of part references, - have significant variability in the definition of acoustic patterns.

[0010] Until now, mechanical drilling technology has been recognized and approved for the production of these drillings.

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

[0012] Acoustic studies demonstrate better noise reduction by evolving the sound trap patterns towards an identical opening percentage but with a considerably 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 holes to be made 4 times higher and therefore 4 times more production time.

[0014] There is therefore a challenge of gaining in 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 effector with respect to the surface of the part to be machined.

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

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

[0018] There is therefore a need to make operations faster in knowing the approach and clearance distances of an effector, in particular multi-spindle, in a method of drilling 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. Statement of the invention

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

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

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

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

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

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

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

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

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

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

[0030] According to an advantageous embodiment, the method comprises a step of moving the effector to position it at another point on the part to be machined, then repeating steps i / to viii / .

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

[0032] The method may comprise any of the following advantageous features:

[0033] - the approach clearance (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 clearance (Gp) is less than or equal to 0.5 mm;

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

[0037] According to an advantageous embodiment variant, the rising edge of the all-or-nothing (TOR) signal for detection by laser distance sensor of the drilling guard (Gp) according to step iv / is directly on an input of the speed variator of the drilling tool. This variant makes it possible to avoid the processing time of a numerical control and that of its automaton. Thus, the method has better responsiveness.

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

[0039] The invention also relates to a multi-spindle robot effector, in particular intended to implement the method as described previously, 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 of 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 the advance or the raising of a drilling tool.

[0044] The invention also relates to the use of the method and / or the 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 method as described above.

[0046] Thus, the invention essentially consists of a method for drilling a workpiece, in particular with curved surface(s), by means of drilling tools mounted in a robot effector, which implements steps of positioning the tools based on detection by laser distance sensors, 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 simultaneous positioning of drilling tools.

[0048] Furthermore, with the detections carried out by the laser sensors, this makes it possible to dynamically reappropriate the guard positions of the axes and the drilling tools in relation to the actual curvature of the part to be machined.

[0049] Ultimately, the invention provides numerous advantages over the methods according to the state of the art, among which we can cite: - a reduction in the machining time of a part, particularly 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 characteristics of the invention will become more apparent upon reading 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.l] [Fig.l] is a longitudinal 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 sectional view of the multi-spindle effector with mechanical probes, showing the return positioning of the spindles once the 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-spindle effector provided with a laser distance sensor around a spindle, according to the invention.

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

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

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

[0057] This effector 1 is more particularly intended for drilling holes of small diameter, 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 makes it possible to initiate the actual step of drilling a hole using the spindle 12.

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

[0060] An approach to the effector 1 is carried out using the 6 axes of a robot carrying the effector. This approach is carried out until the 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, all of the 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 taken to implement the mechanical probing is relatively long.

[0064] Furthermore, as is apparent from [Fig. 1], a mechanical probe 11, even if well integrated into an effector 1, occupies a significant amount of space around the spindle 10. And therefore, the number of spindles 10 for a given surface area of ​​part P to be drilled is constrained by the cumulative dimensions of all the mechanical probes 11.

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

[0066] To overcome the drawbacks of this method according to the state of the art with mechanical probes 11, the inventors have judiciously thought of implementing a drilling method by installing laser distance sensors 100 instead of the probes.

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

[0068] The drilling method 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 advance is managed by the robot carrying effector 1.

[0070] The W axis is the feed axis normal to the part to be drilled P and this feed is managed 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 part P to be machined.

[0072] Step i / : the robot effector is approached with positioning of the axis (Z) of its orthogonal center at a surface point of the part predetermined by calculation, and a surface point of the part predetermined by calculation is positioned from each drilling tool at a distance, called approach clearance (Ga). 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 close clearance (Gr) predetermined by calculation. Preferably, the close clearance (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 speed (Vr),

[0075] Step iv / each drilling tool axis (W) is then advanced at the feed rate (Vr) up 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 all-or-nothing (TOR) signal for detection by laser distance sensor of the drilling guard (Gp) according to step iv / is directly on an input of the speed variator of the drilling tool. This saves time for starting the following step v / .

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

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

[0079] Step vii / : once the desired drilling has been carried out, the set of drilling tools 10, 12 is removed, simultaneously or not, from the part P. This removal 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 clearance (Gs) determined from the drilling clearance (Gp) of each axis recorded in step iv / by each of the laser distance sensors 100. Preferably, the safety clearance (Gs) is equal to the drilling clearance (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 rise of the pins 10 is done according to a curve Cl which perfectly matches the real curvature of the part as illustrated in [Fig.4].

[0082] Other variants and improvements may be provided 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 is also possible to envisage integrating it into its body, i.e. right next to the drilling tool housing.

Claims

Claims

1. Method for drilling a workpiece, in particular with curved surface(s), by means of drilling tools mounted in a robot effector, the method comprising the following steps: i / approaching the robot effector with positioning of the axis (Z) of its orthogonal center at a surface point of the workpiece predetermined by calculation, and positioning each drilling tool at a distance, called approach clearance (Ga), a surface point of the workpiece predetermined by calculation, ii / advancing the axis (Z) to a distance called close clearance (Gr) predetermined by calculation, iii / once the close clearance (Gr) is reached, setting in motion the axis (W) of each drilling tool at a predetermined feed rate (Vr), iv / advancing each drilling tool axis (W) at the feed rate (Vr) to a distance, called drilling clearance (Gp) detected by each of the sensors laser distance and recorded, v / once the drilling clearance (Gp) is reached,changing the feed speed of each drilling tool from speed Vr to a feed speed (Vt), called the working speed, vi / drilling, simultaneous or not, of the part by all the drilling tools at the working speed (Vt), vii / withdrawal, simultaneous or not, of all the drilling tools from the part, viii / raising the drilling tools and returning for each of them to a distance called the safety clearance (Gs) determined from the drilling clearance (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 part to be machined.

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

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

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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 one of the preceding claims, the approach clearance (Ga) being less than or equal to 20 mm. Method according to one of the preceding claims, the close guard (Gr) being less than or equal to 10 mm. Method according to one of the preceding claims, the drilling clearance (Gp) being less than or equal to 0.5 mm. Method according to one of the preceding claims, the safety clearance (Gs) being equal to the drilling clearance (Gp) plus a safety margin. Method according to one of the preceding claims, the rising edge of the on / off signal (TOR) for detection by laser distance sensor of the drilling clearance (Gp) according to step iv / being directly on an input of the speed variator of the drilling tool. Method according to one of the preceding claims, step vii / of withdrawal being carried out when the end of drilling is detected by a system for monitoring consumption of drilling tools. 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, for individually detecting 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 the advance or the raising of a drilling tool. Use of the method according to 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 method according to one of claims 1 to 10.

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