Patent Application
20220314366
The description relates to a laser-processing apparatus, comprising a set of at least two laser sources different from one another configured for providing respective laser beams having wavelengths different from one another, and a laser head, which can be operated as end tool of a laser machine tool that can be configured for carrying out at least one type of laser processing operation that can be selected from a set of types of laser processing operations, said laser head comprising a set of orientable optical components so as to provide a set of selectable optical paths for directing a laser beam supplied by a respective laser source of said set of at least two laser sources, and a control unit coupled to said set of at least two laser sources, to said set of orientable optical components, and to the laser head, which can be configured for carrying out at least one type of laser processing operation that can be selected from a set of types of laser processing operations, said control unit being configured for controlling said at least two laser sources, said set of orientable optical components, and said laser head according to the type of laser processing operation selected from said set of types of laser processing operations so as to carry out the type of laser processing operation selected, i.e., so as to supply and direct said laser beam associated to the respective type of processing operation onto a region of a work surface.
One or more embodiments regard a method for controlling the above laser-processing apparatus, and use of the apparatus, for example in a context of a machine tool or of an anthropomorphic robot.
In the field of laser processing there exist multiple systems for conveying electromagnetic radiation, which are referred to as “laser heads” and can be operated as end tools of a laser machine tool, each head being specialized for carrying out a limited number of types, usually one or two, of laser processing operations at the same time. Performing different types of processing operations with one and the same laser machine tool is possible by replacing each time a laser head specialized in a type of processing operation with another laser head specialized in the different type of processing operation that is to be carried out. However, this replacement is made at the cost of interruptions in production, thus potentially leading to very long intervals of production downtime. In fact, at each replacement of a head for a processing operation of one type with another head for a processing operation of a different type, it may be necessary to replace also a sensor cone of the head and recalibrate the machine to operate properly with the new tool installed.
In the case where the tool with which the laser head is equipped is only the laser beam, a device is known for providing a first machining tool, generated by a first source of radiation, in particular a laser source, in the form of a processing beam and at least one other machining tool of a different nature or different origin, in particular a source of radiation different from the source of radiation of the first machining tool, wherein the different machining tools can be set in contact with a workpiece so as to machine the material, and machining of the workpiece can be carried out via just one of the machining tools at each moment. A laser-processing apparatus of the type referred to above is described in the document No. US 2005/0205537 A1.
A solution which is, from certain points of view, similar is known from the document No. U.S. Pat. No. 9,180,551 B2, which describes a laser machine tool for performing laser processing via laser ablation, which comprises a dual and mobile laser head prearranged for emission of laser beams, where said dual laser head incorporates two or more laser sources, each laser source emitting a different type of laser beam, where the two or more laser sources incorporated in the dual laser head are not able to carry out simultaneously processing of a workpiece.
However, the above solutions can facilitate reduction of production down times only in the case of laser processing operations that use only the laser beam for carrying out processing. In some specific laser processing operations, such as direct-energy-deposition (DED) additive manufacturing, cladding, or (wire or powder) welding—just to cite a few examples—, nozzles are moreover used for supplying material to be directed onto a work surface together with the laser beam, for example filiform metal material in the case of wire or powder welding in the case of additive manufacturing.
There hence exists the problem of providing a laser-processing apparatus comprising a set of processing operations that include the use not only of a laser beam but also of other tools, in particular nozzles for directing materials onto the work surface.
In the field of laser-processing apparatuses of the DED additive-manufacturing type there exist solutions that use two heads, each equipped with nozzles and corresponding laser, either as replacement of one another or operating in parallel, which can facilitate processing operations of a DED type with varying characteristics. This solution presents, however, the disadvantage that the object obtained presents traces having different thicknesses set alongside and on top of one another, which leads to an increase in porosity of the object produced since it is easier for there to remain gaps in the object, for example gaps of a size given by the difference between the different thicknesses.
Use of multiple laser heads moreover also increases the costs, with a consequent increase in the investments necessary for the production line and consequently in the costs for manufacture of the objects.
Moreover, in the case where laser beams having different characteristics and different powers are used as laser processing tools, there arises the problem of maintaining good optical performance: if an optical system is used with a coating for a wavelength of for example 1070 nm during processing using a laser at a different wavelength, the quality of the processing might not meet requirements.
Furthermore, conventional additive-manufacturing apparatuses may use a frame provided with nozzles, which may limit the freedom of manoeuvre of the head for direction of the laser beam onto the work surface. Moreover, this type of limitation in the freedom of movement may render more problematical production of some parts, for example on account of the encumbrance of the frame.
Notwithstanding the vast activity in this area, as witnessed, for example, by the various documents listed previously, further improved solutions are desirable.
The object of the embodiments described herein is to improve apparatuses and methods according to the prior art, as discussed previously.
In particular, an object of the invention is to propose a laser-processing apparatus, and a method for controlling the apparatus itself, which will:
An aim of one or more embodiments is to contribute to providing such an improved solution.
Various embodiments achieve one or more of the aforesaid objects thanks to a laser-processing apparatus and to a corresponding method, having the characteristics recalled in the ensuing claims. The claims form an integral part of the technical teaching provided herein in relation to the invention.
In particular, the object of the invention is an apparatus having the characteristics referred to at the start of this description and moreover characterized in that:
said laser head comprises a set of nozzles configured for being controlled to direct at least one processing material onto said region of a work surface, said set of nozzles comprising at least one nozzle configured for directing in a controlled way jets of powder of at least one material, preferably metal powder, as well as comprising at least one of the following:
a) a first nozzle configured for directing in a controlled way a metal wire onto said region of a work surface, preferably metal wire for laser welding; and
b) a second nozzle configured for directing in a controlled way an assist gas onto said region of a work surface, preferably an assist gas for welding,
and wherein said at least one control unit is coupled to said set of nozzles and is configured for controlling at least one nozzle of said set of nozzles according to the type of laser processing operation associated to and selected from said set of types of laser processing operations in order to control said nozzles so that they will direct respective processing materials onto said region of a work surface simultaneously with direction of said laser beam associated to the type of laser processing operation selected onto said region of said work surface.
In this way, it is possible to carry out processing operations of various kinds (for example, welding, cladding, additive manufacturing, cutting, and ablation) using one and the same laser head, to carry out both laser processing of an additive type, such as the DED additive manufacturing, and laser processing of a subtractive type, such as laser cutting, as well as laser processing of some other type, such as ablation. In particular, this is facilitated by the possibility of selecting each time activation of the source and/or activation of the tools that are most convenient for carrying out the operation chosen. For instance, in the sector of additive manufacturing, it is possible to use, in particular in an alternative and not necessarily simultaneous way, a first source having a first wavelength configured for treating materials with high reflectivity (for example, copper, brass, aluminium) and a second source having a second wavelength configured for materials with low reflectivity (for example, iron, steel), thus favouring safeguarding of the properties of the optical components of the apparatus from damage due to undesired reflections.
One or more embodiments may regard a corresponding method. A method for controlling an apparatus according to the present description may be an example of such a method.
In various embodiments, the set of selectable optical paths comprises at least two optical paths for supplying a first laser beam from a first laser source to said laser head, and/or at least two types of laser processing operations of said set of types of laser processing operations are associated to at least one respective nozzle of the set of nozzles so as to render use of the head flexible in different contexts.
In particular, at least one portion of at least one of the two optical paths is obtained with dual-core optical fibre comprising at least one inner core and one outer core, where said at least one of said at least two optical paths configured for supplying a first laser beam from a first laser source to said laser head comprises an optical switch configured for directing said first laser beam, alternatively, into the inner core or into the outer core of said dual-core optical fibre.
This solution affords the possibility of selecting a (resonant) mode of the laser beam and consequently a power distribution of the laser beam, which may be Gaussian or doughnut-shaped, the latter, in particular, making it possible to carry out particular processing operations, for example during welding between joints of different sizes or also cuts with a better surface finish.
In various embodiments, the set of nozzles of the laser head is mobile between a protruding position and a recessed position, and moreover the laser head comprises:
and the control unit is coupled to the set of actuators and is configured for controlling said set of actuators to translate said nozzles between the protruding position and the recessed position according to the type of laser processing operation selected from the set of selectable types of laser processing operations.
The above solution facilitates reduction of interference between a workpiece and the nozzles during types of processing operations that do not necessarily require the aforesaid nozzles, for example during laser cutting. Moreover, advantageously, provision of mobile nozzles that can be recessed in a cavity when they are not in use prevents the nozzles from being exposed to residual heat during a process in which they are not used.
In particular, the set of types of laser processing operations that can be carried out comprises at least two types of laser processing operations, which include direct-deposition additive manufacturing with a first type of processing material in the form of powder and at least one of the following: direct-deposition additive manufacturing, which uses a second type of processing material in the form of powder different from the first; ablation; wire welding; cladding; heat treatment; and laser cutting.
In various embodiments, the set of nozzles of the apparatus comprises at least one nozzle that can be articulated about an articulated joint of its own and an electric actuator configured for orienting the nozzle with respect to the articulated joint, and moreover the control unit is configured for issuing a command to the electric actuator for it to bring said at least one articulated nozzle to assume a first, protruding, position or a second, recessed, position.
The above solution facilitates reduction of the overall encumbrance of the head, in particular in the case where the articulated nozzle comprises shape-memory material in the proximity of or in a position corresponding to the articulated joint, where the shape-memory material is configured for bringing the nozzle into one between the first orientation and the second orientation, alternatively, as a function of a value of electric current applied to the articulated joint via a cable. In particular, the aforesaid first orientation causes the nozzle to form an angle, for example an obtuse angle with an optical axis of direction of the laser beam towards said region of said work surface, whereas the second orientation causes the nozzle to be parallel to said optical axis.
Moreover, via a further electric actuator, for example a roto-translational actuator, driven by the control unit, the encumbrance of the nozzles in the processing area is reduced or eliminated in a very effective way.
In order to reduce or eliminate the encumbrance of the nozzles so as to reduce any possible interference with the laser head, in various embodiments the first nozzle, the second nozzle, and at least two nozzles configured for directing jets of powder material, preferably metal powder, set facing one another in said set of nozzles are assembled in a supporting structure in the laser head so as to form the vertices of an equilateral rhombus having its centre in the proximity of or in a position corresponding to a hole for output of the laser beam from the head so as to reduce the encumbrance of the nozzles.
In various embodiments of the apparatus, at least one nozzle for directing jets of powder material may comprise an iris diaphragm, formed by a set of blades pivoted in a rotating ring and an electric actuator coupled to said rotating ring and configured for turning the ring so as to vary an area of an aperture section of said nozzle in a direction transverse to a direction of emission of said jets of powder, consequently varying a flow rate of said jets of powder. The above actuator may be driven, for example, by the control unit.
The above mechanism of variation of the aperture section of at least one nozzle for directing jets of powder renders the production process flexible on the basis of the requirements of resolution and precision for the individual workpiece. For instance, this solution advantageously facilitates, with the use of just one laser head:
The object of the invention is also a corresponding method for controlling an apparatus according to the present description, comprising operations of:
The method may moreover envisage providing the control unit with a look-up table with which to associate to each type of laser processing operation that can be selected from said set of types of laser processing operations a set further comprising at least one parameter between a position of one or more nozzles of said set of nozzles and an orientation of one or more nozzles of said set of nozzles.
The above method affords the possibility of controlling the apparatus in a personalized way according to the production requirements, thus maintaining a high flexibility of operation of the apparatus.
One or more embodiments will now be described, purely by way of example, with reference to the annexed drawings, wherein:
In the ensuing description, one or more specific details are illustrated in order to enable an in-depth understanding of examples of embodiments of the present disclosure. The embodiments may be obtained without one or more of the specific details or with other methods, components, materials, etc. In other cases, known operations, materials, or structures are not illustrated or described in detail so that certain aspects of the embodiments will not be obscured.
Reference to “an embodiment” or “one embodiment” in the framework of the present description is intended to indicate that a particular configuration, structure, or characteristic described with reference to the embodiment is comprised in at least one embodiment. Consequently, phrases such as “in an embodiment” or “in one embodiment” that may be present in one or more points of the present description do not necessarily refer precisely to one and the same embodiment.
Moreover, particular conformations, structures, or characteristics may be combined in any adequate way in one or more embodiments.
The references used herein are provided merely for convenience and hence do not define the sphere of protection or the scope of the embodiments.
Represented in
As has been said, the laser head 20 may be configured so as to carry out at least one type of laser processing operation that can be selected from a set of types of laser processing operations, as discussed in what follows.
In particular, the apparatus 10 as exemplified in
In order to be able to carry out the above processing operations in a way that can be selected by a user so as to obtain a sort of “work centre” with which to perform each time one or more laser processing operations, the above apparatus comprises a set of at least two laser sources 12, 14, in particular sources different from one another (e.g., both as regards the wavelength and as regards the power) and configured for supplying respective laser beams having wavelengths different from one another. For instance, the set of at least two laser sources 12, 14, may comprise sources different from one another both as regards the wavelength and as regards the power; for example:
In particular, the second laser source 14 may be used in operations (such as DED additive manufacturing, cutting, and welding) in which the materials to be treated are highly reflective materials, e.g., copper, brass, or aluminium.
By “highly reflective materials” are meant those materials that tend to reflect electromagnetic radiation incident thereon, having a specific wavelength, in a percentage much higher than 50% of the incident light.
It should be noted that the above list of possible laser processing operations and the above combinations of operations for the sources are presented purely by way of example and in no way limit the types of laser processing for which the apparatus may be prearranged to operate in a flexible way.
As exemplified in
For instance, the control unit 30 can communicate commands that bring about switching-on, with consequent emission of respective laser beams, or switching-off of one or more sources, or else can drive an optical switch inside the first source to send the laser beam towards a first output or a second output. The laser beams emitted by the respective sources 12, 14 are then supplied to the laser head 20, which can be operated as end tool of a laser machine tool 90, 80 for carrying out at least one laser processing operation.
In particular, as exemplified in
As has been said, in various embodiments, where at least one portion 120 of at least one of said at least two optical paths 120, 122 for supply of the first laser beam L1 from the first laser source 12 to the laser head 20 comprises a stretch of multi-clad optical fibre 120, which includes a light-guide core 120a surrounded by at least one further layer of light-guide cladding 120b around the core 120a, and where at least one of the at least two optical paths for supply of a first laser beam from a first laser source to the laser head 20 comprises an optical switch configured for directing the first laser beam L1, alternatively, into the core 120a or into the further light-guide cladding layer 120b of said multi-clad optical fibre 120.
In various embodiments, the first laser source 12, and in particular the stretch of multi-clad fibre, may comprise a system of the type discussed in the Italian patent application No. 102018000021538 filed in the name of the present applicant. Such a system or apparatus may comprise: a multi-clad fibre, which includes a light-guide core surrounded by at least one further light-guide cladding layer around said light-guide core; an input interface comprising a first set of channels for input into said core, configured for receiving at least one first optical fibre, and a second set of channels for input into the aforesaid at least one light-guide cladding layer, configured for receiving at least one second optical fibre. The above apparatus may further comprise an optical switching module, which includes an input port, a first output port and a second output port, a first optical path between said input port and said first input channel of said first set of channels for input into the aforesaid core via said first output port, and at least one second optical path between said input port and a second input channel of said second set of channels for input into said at least one light-guide cladding layer via said second output port, said optical switching module being controllable for switching between said first optical path and said second optical path; and a set of laser modules comprising at least one first laser module and at least one second laser module, said laser modules being configured for emitting respective laser beams when they are in a respective on state, said at least one first laser module being coupled to an input channel of said first set of input channels via said at least one first optical fibre, said at least one second laser module being coupled to said optical switching module.
Optionally, the optical switch 128 can be controlled, for example with signals sent by the control unit 30, so as to assume a number of positions, for instance to assume an inclination that can range between 0° and 45° with steps of 5°, so as to guide the laser beam L1 emitted by the laser source 124 in a “fine” way towards the first output. The above solution, as has been said, helps to render the (resonant) mode in which the laser beam propagates flexible, facilitating formation, for example, of a doughnut-shaped profile of the laser beam or a Gaussian profile of the laser beam.
In an embodiment like the one exemplified in
The optical-selection module 16, as exemplified in
The aforesaid optical switches 168, 164 in the selection module 16 and the optical switch 128 in the first source 12 can be driven by the control unit 30 so as to assume:
The control unit can drive the aforesaid switch 128, 168, 164 to assume respective open/closed positions as a function of parameters of the processing operation selected by a user.
For instance, in the case where a welding operation is to be carried out, the control unit will drive the switch 128 to send the beam L1 towards the first output 127, and the optical switches 168, 164 in such a way that they are both in a closed state so as to supply to the laser head 20 the beam at output from the multi-clad optical fibre 120.
In another example, if the processing operation selected is laser cutting, then the control unit 30 drives the switch 128 to direct the beam L1 towards the second output 129 and the first switch 164 in such a way that it is open, while it drives the second switch 168 in such a way that it is closed so as to supply to the laser head 20 the beam at output from the simple optical fibre 122.
In another example, if the processing operation selected is laser ablation, then the control unit 30 drives the switch 128 and the switch 164 so that they are closed and the switch 168 so that it is open so as to supply to the laser head 20 the beam at output from the third optical fibre 140.
Table 1 below sums up what has been discussed previously in regard to the embodiment exemplified in
In one or more embodiments, use of the aforesaid method for directing the laser beam from the set of the at least two sources, thanks to the fact of providing selectable optical paths for one of the two lasers, can advantageously avoid the need to switch off and on one source or the other each time to supply the laser beam, thus reducing the processing down times and reducing degradation in performance of the sources that could be damaged by continuous on and off sequences. In general, one or more embodiments favour an improved versatility of the technological processes thanks to the integration of a number of laser sources in a single system.
As exemplified in
The control unit 30 is coupled to said light sensor 182 and can be configured for driving the laser sources 12, 14 and/or the optical switches in the selection module 16 as a function of the measurement signal V detected.
As exemplified in
The aforesaid laser head 20 is configured for transmitting the laser beam L via a set of optical components (or modules) that are orientable (i.e., mobile) 22, 24, 26, so as to direct it onto a work surface 110 while it is being translated along axes X, Y, Z via a movement structure TS. The supporting structure may be a cantilever supporting structure, as exemplified in
The aforesaid set of optical components 22, 24, 26 comprises, for example:
It should be noted that the above set of optical components 22, 24, 26 is presented purely by way of non-limiting example, it remaining on the other hand understood that in various embodiments one or more of the elements 22, 24, 26 might be different or absent according to the requirements of a user. In fact, it is advantageously possible to prearrange a variable amount and variable types of orientable optical modules, comprising optical components coupled to respective actuators, to be inserted as optical components into the set 22. This involves the possibility of prearranging the apparatus on the basis of the requirements of the types of processing operations that a user wishes to be able to carry out with the laser head 20.
In general, by “work surface” is meant the surface at the level of which the process is carried out, in particular the surface, whether this be also the surface of the support or of the element on which processing is carried out.
The laser-beam orientation module 22 may comprise an orientable mirror 220, in particular a mirror that can be oriented via one or more actuators 222, 224 to which it is coupled, for example galvanometric actuators configured for varying at least an angle of inclination thereof via an optical scanner, for example by driving the actuator 22a, or a process for imparting a dynamic movement on the laser beam L, for example by varying, with a frequency of variation co, at least an angle α between an axis normal to a reflecting surface of the mirror and a direction of propagation of the laser beam L.
In various embodiments, in particular when one of the types of processing operation selected is DED additive manufacturing, for example the actuator 222 can be controlled according to a “wobbling” process such as the one described in the Italian patent application No. 102019000004681, filed in the name of the present applicant. Such a process may comprise an additive-manufacturing process, where an additive-manufacturing head is provided configured both for directing one or more jets of powder, in particular metal powder, onto a region of a work surface, and for directing simultaneously a laser beam onto said region to form a focusing spot of the laser beam on said region, and where, during direction of said jets of powder and of said laser beam, said additive-manufacturing head is simultaneously translated in a direction transverse to the direction of the laser beam so as to give rise to a trace (MPP) obtained by melting of said powder as a result of the power transmitted to said powder by said focusing spot. During movement (V) of the additive-manufacturing head in said transverse direction, a dynamic movement imparted on the laser beam is emitted by the head, said movement being configured in such a way as to obtain a width of the trace that is independent of the size of the focusing spot of the laser beam and is equivalent to the one produced by an apparent spot having a width substantially corresponding to the width of the trace, and in such a way that the distribution of the power transmitted by the laser beam to the trace varies in the direction of width of the trace.
In various embodiments, for example, the actuator 224 can be controlled according to a process modelled on an optical scanner in itself known.
In one or more embodiments, for example, the beam-shaping lens 24 can vary the power distribution of the laser beam L so as to obtain a beam having a Gaussian distribution as exemplified in
In particular, in various embodiments, the beam-shaping lens 24 may comprise:
For instance, a power distribution, such as top-hat distribution, can be obtained using a beam-shaping lens 24 comprising diffractive optics of the “round” optics type.
In various embodiments, the aforesaid beam-shaping optics can facilitate also formation of a doughnut-shaped profile of the laser beam, as exemplified in
As has been said, in various embodiments, for example as an alternative to the use of the beam-shaping optics, the position of the optical switch 128 can be varied in such a way that the radiation emitted by the laser 124 is conveyed into the outer core 120b of the multi-clad fibre 120, facilitating formation of a doughnut profile of the laser beam, as exemplified in
It should be noted that, even though the above optical components have been described as being comprised in the head, in various embodiments they could not be present or be comprised outside the head; in particular, the laser-beam orientation module could be located at the input of the head but mechanically decoupled therefrom.
In various embodiments, the control unit 30 may comprise a numeric control unit 60, as exemplified in
Implemented in the personal computer 62 and in the servo-control card 63 are procedures for driving the apparatus 10, as discussed in what follows.
Some laser processing operations require, in addition to use of the laser beam, also provision of the materials for carrying out the process. In particular, as exemplified in
To carry out a plurality of processing operations in a flexible way, the laser head 20 may hence be equipped with a set of nozzles 40, 42, 44, 46 for carrying out the aforesaid processing operations.
For instance, the laser head 20 includes:
Optionally, two nozzles for emission of jets of powder 40, 44, which can be used for DED additive manufacturing may be advantageously set facing one another so as to emit the respective jets of powder in the proximity of or in a region corresponding to two points located at the ends of a segment passing through the central hole 70 so as to facilitate symmetrical deposition of powder on the work surface so as to achieve more accurate and improved processing.
In various embodiments, as exemplified in the portion b) of
As exemplified in
As exemplified in
In the elbow, i.e., in the intersection between the first portion 202a and the second portion 202b of the duct 202, a mirror 204 may be present, which may be either a fixed mirror or an orientable mirror, as discussed previously in relation to the laser-beam orientation module 22. The mirror 204 can be coupled to the duct 202 so as to form a right angle, i.e., an angle of 90°, with an axis R that joins the connection points between the first portion 202a and the second portion 202b of the duct 202.
The above portion 202b downstream of the elbow moreover houses further optical components, for example the beam-shaping optics 24. In particular, the beam-shaping optics 24 can be located as terminal element of the portion downstream of the elbow 202b that extends into the central body 50a of the supporting structure 50.
An outer diameter of the coupler 202 and an inner diameter of the central body 50a can be set apart by a spacer 206, for example shaped like a ring that surrounds the second portion 202b of the cylindrical tube 202.
In order to carry out processing operations according to the method discussed herein, the head 20 may, for example, be provided with cabling, for example constituted by optical fibre, for conveying the radiation emitted by one of the sources of laser radiation, set remote from the head.
The aforesaid wiring may be associated to ducts for possibly delivering also supporting gas, i.e., assist gas, such as argon or nitrogen, which supports the process of welding, cutting, or additive manufacturing. The aforesaid cabling may include a catenary comprising the aforesaid respective ducts and/or ducts for delivering powder material for additive manufacturing supplied by respective supply devices arranged remote from the head 20. Moreover, the aforesaid catenary may comprise driving and control electrical cables and possible cooling delivery pipes.
In various embodiments, the aforesaid ducts (for example, those for gas, those for powder alone, optical-fibre cables and electrical cables) may be within one and the same catenary, in which they will in any case remain insulated from one another (i.e., the gas duct cannot convey the powder and is insulated from the duct for the powder, and the same applies to all the ducts in the catenary).
In various embodiments, in particular, the device for supplying the supporting gas for laser cutting can be coupled, via a respective duct, to the terminal portion 50b of the laser head 20 in such a way that, once the aforesaid supporting gas is emitted, it will come out of a hole 70 for output of the laser beam located in the aforesaid terminal part 50b of the laser head 20, for example in a coaxial way with respect to the laser beam. The control unit can be coupled to said supply device and configured for governing emission of the assist gas for laser cutting through the terminal part 50b of the head when an operation of laser cutting is selected. The laser head 20 further comprises a set of actuators and guides 400 coupled to at least one nozzle, for example to the gas nozzle 46, of a set of nozzles 40, 42, 44, 46 in such a way that at least one of the aforesaid nozzles, or preferably all of them, is mobile or retractable, i.e., mobile continuously or in discrete steps between a protruding position and a recessed position so as to be used for carrying out a laser processing operation when it is located on the outside of the head 20 in a protruding position with respect to a central body 50a of a supporting structure 500 of the head 20, and can be brought back into the recessed position where it is received into a purposely provided cavity within the central body 50a when it is not used for carrying out processing. Advantageously, this consequently prevents any damage to the mechanical characteristics of the aforesaid nozzles, which otherwise, if they were not mobile or retractable, would risk getting damaged by being struck by the reflections of the laser beam during operations in which they are not directly used. Moreover, in the case where they these nozzles were not mobile or retractable, they could also entail an encumbrance such as to affect performance of the processing operation.
The nozzles, which can be seen in perspective view of
As exemplified in
In the view of
In various embodiments, the control unit 30 is configured for driving the set of actuators 400 so that they will translate at least one nozzle 40, 42, 44, 46 between the protruding position and the recessed position according to the type of laser processing operation that can be selected from the set of types of laser processing operations.
As has been mentioned, the control unit may comprise a numeric control unit 60, as exemplified in
It should be noted that in the solution described herein the unit 60 is moreover configured for sending further commands regarding for example the flow rate of the jets of powder to be melted, the flow rate of the supporting gas, the characteristics of the laser radiation (power, continuous mode/pulsed mode/other mode, possible frequency and duty cycle, shape of the profile of radiation, whether Gaussian, top-hat, or some other), and the characteristics of the laser beam (diameter, focusing, etc.). The aforesaid commands can be associated to the instruction sequence P so as to occur in given points and at given instants defined by the path of the head while it is being translated by the supporting structure to which it is coupled.
The commands regarding the characteristics of the laser radiation and the characteristics of the laser beam can be controlled for regulating the thermal profile, for example by varying the power and/or diameter and/or focusing of the laser spot in the stretches of processing path.
Table 2 presents below in a synthetic way an example of how it is possible to associate to different processing operations the different positions of the nozzles. The control unit 30 can drive the actuators to assume a position between a protruding position and a recessed position, for example, according to a table appearing below.
It should be noted that the aforesaid list of associations between types of processing and position of the nozzles is provided purely by way of example, it remaining on the other hand understood that other types of processing and nozzles may be used in various embodiments.
In various embodiments, as exemplified in
For instance, the control unit 30 can control the aforesaid shape-memory articulated joint by applying an electric current so that cause the articulated nozzle 40 to assume a first orientation, for example inclined so as to form an angle for example an obtuse angle as exemplified in the figure, with the direction AO of emission of the laser beam, when the nozzle 40 is in the aforesaid protruding position, or a second orientation, for example parallel to the stretch of optical axis AO of the laser beam in the second portion 202b of the duct 202, when the aforesaid nozzle is in the recessed position.
In particular, the articulated joint 45 may be made of shape-memory material configured for assuming a shape as a function of a current applied to the electrical cable driven by the aforesaid control unit. The guides located just before the entry point of the chamber have the purpose of bringing the nozzles back into the vertical position so as to enable their re-entry into their seats by mechanically deforming the articulated joint. In this way, advantageously, it is possible to reduce the encumbrance the actuator due to the presence of the articulated joint and to provide the openings for re-entry of the mechanical arms of the nozzles as simple circular holes having the same section as the arm of the respective nozzle.
The terminal part 50b of the frame 50 comprises a circular recess having a diameter, for example, approximately equal to the internal diameter of the duct 202 that terminates with a slight taper, which has a bottom wall that is optically transparent coupled to which is the focusing lens 26, which can have a diameter smaller than the maximum internal diameter of the duct 202.
The aforesaid actuator may be driven via the control unit so as to vary an area of an aperture section of the aforesaid nozzle 40 in a direction transverse to a direction of emission of the jets of powder. The aforesaid variation of the aperture section facilitates variation of a flow rate of the powder jet at output, once again making it possible to obtain production processes of DED additive manufacturing that are accurate and with properties of the process that can be controlled in a fine way, and thus in an improved way.
The movements of the beam 11b with respect to the slide 91c and of the slide 11c with respect to the guide structure 11a are also driven by motors, which are not, however, visible in
As shown in
It should be noted that what has been discussed in relation to the movement structure of
Without prejudice to the underlying principles, the details and the embodiments may vary, even appreciably, with respect to what has been described herein, purely by way of example, without departing from the sphere of protection, as defined in the annexed claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 102019000009366 | Jun 2019 | IT | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/IB2020/055648 | 6/17/2020 | WO |
