Patent Application
20120168992
The invention relates to a method according to the preamble of claim 1 as well as bending die according to the preamble of claim 11.
For a long time, the bending of workpieces has been a frequently applied and reliable method for processing workpieces by reshaping. The scope of application of bending processes is frequently limited by material properties, especially by the mechanic-technological properties. The problem concerning brittle materials like magnesium, titanium, spring steels, high-strength aluminum-alloys, high-strength steels or other materials known to be brittle is that in case of a deforming by bending, these materials do not provide sufficient plastic formability and thus other undesired deformations appear. A parameter that can indicate the respective behavior of materials is the so-called ultimate strain that means the value of the plastic deformation that a workpiece to be deformed can bear until it breaks. An alternative parameter for this behavior is also the so-called yield strength to tensile strength ratio that considers the tension required in a workpiece at the beginning of a noticeable plastic deformation in relation to the tension within the workpiece in case of breaking load.
In order to make such materials having a low ultimate strain or a high elasticity ration accessible to the application of a deformation methods, especially to bending, methods putting the workpiece into a condition providing more favorable mechanic characteristics and enabling it to be deformed by means of a bending method have been applied for a while. A known method is heating the workpiece to be bent at least in the region of the deformation zone, with the result that in this heated area the tension necessary for initiating of plastic deformation can be reduced.
As an example of such a method, the EP 0 993 345 A1 discloses a method for bending a workpiece by application of mechanic force under selective heating of the workpiece along a bending line by means of laser radiation, where one laser beam or several laser beams are formed to be an elongate radiation field and where a heating zone along the bending line of the workpiece is created by the radiation field. In this case, the device for forming the linear radiation field comprises cylindrical lenses and/or cylindrical mirrors, which are used to guide a radiation field through the opening in the bending die onto the workpiece. In the exemplary embodiment according to
This solution for the guiding of high-energy radiation in a bending die known from the EP 0 993 345 A1 is not ideally suited for the practical application with common bending machines, because the bending die provides a limited mechanical strength due to its two-piece embodiment and the press beam receiving the bending die would have to provide recesses for the beam distribution arrangement.
The objection of the invention is to provide a bending die that is applicable to a bending method according to its genre, which is better applicable for practical application.
The objection of the invention is achieved by a method according to claim 1 as well as a bending die with characteristics according to claim 10.
Due to the fact that at least one concentrated high-energy radiation beam is guided into the tool base body through at least one beam entry opening and said radiation beam is at least partially deflected, expanded in the tool base body by a beam affecting arrangement and is guided onto the workpiece through the beam exit opening, such a bending die can, on the one hand, be used at every conventional bending press or trimming press and, on the other hand, every conventional radiation source, applicable for the production of a concentrated radiation beam, can be used as radiation source for the application of the method. This is a large economic advantage, because in many production plants both a conventional bending press and an applicable radiation source, especially a laser device, are available and their fields of application can be expanded due to the application of the method according to the invention. Thus, only by the application of the method according to the invention or the bending die according to the invention, an expansion of the available production methods as well as an improved capacity utilization of the existing mechanical infrastructure is possible. The deflection, expansion and discharge of the radiation during the heating phase is in this case effected particularly temporally and locally stationary without application of mechanical moved, rotating or swinging mirrors or apertures.
The outer dimensions of such a bending die can in this case particularly correspond to these of conventional bending dies, with the result that in the application no restrictions with respect to the geometry are necessary compared to conventional bending dies.
The beam affecting arrangement comprises means to be able to deflect and/or form and/or divide concentrated beams, with the result that from a concentrated beam essentially expanding in one straight line a radiation most evenly spread in one plane, particularly a planar fanned beam, is produced. The tool base body allows the same bending methods like a conventional bending die that is applicable for air bending. At the same time, the tool base body forms a housing for the high-energy radiation, with the result that also measures concerning industrial safety are simplified.
A further embodiment of the method is that at least the one concentrated radiation beam is divided into at least two radiation beam portions by means of the beam affecting arrangement in the tool base body, and at least one of the radiation beam portions is deflected, expanded and discharged onto the workpiece through the beam exit opening. Thus, after expansion, one beam radiation portion is available for the local heating of the workpiece and a second beam radiation portion can be guided to a place distant therefrom, especially to another heating zone at the workpiece than the zone of the workpiece being irradiated by the first radiation beam portion.
The method can furthermore be supplemented in a way that at least one concentrated beam radiation portion is decoupled from the concentrated radiation beam or the concentrated radiation beam portions by means of the beam affecting arrangement and guided to an adjacent bending die through a beam transfer opening in the tool base body. Thus, the method can be used with bending dies directly aligned having only one radiation source and the application is not limited to one single bending die, with the result that also large bending dies are made accessible to the method according to the invention. For this purpose, a beam entry opening is provided in the adjacent bending die with a thereto connected beam affecting arrangement, too, which can be used to guide at least the one concentrated radiation beam guided into the further tool base body onto the workpiece along the bending recess.
The method can furthermore be embodied in the form that in case of two or more bending dies stringed together a certain part, preferably at all bending dies the same proportion or an adjustable changeable proportion adjusted to the workpiece, of the radiation performance of the radiation source is guided to the respective bending recess by means of the beam affecting arrangement, with the result that an at least approximately even power density is effected along the bending line or the power density is adjustable to the respective power requirement existing. Thereby it is ensured that each part of the deformation zone of the workpiece gets the necessary heating and that the desired bending result is obtained along the entire die length in constant quality. Due to this embodiment, at least one guided in concentrated line-shaped radiation beam is split up into at least two or more planar fanned beams that with an even distribution along the deformation zone effect an even heating of the workpiece in this region.
As a means for the distribution of the beam into several radiation beam portions, for example beam splitter plates, combinations of half-wave plates followed by polarizing filters, beam splitter cubes, polarization beam splitter or similar beam splitting optical elements are a possibility. The spreading or the expansion of the split radiation beam portions are for example effected by cylindrical lenses or convex mirrors.
An advantageous exemplary embodiment of the method is that at least two concentrated high-energy radiation beams are guided into the tool base body and one radiation beam portion is decoupled from each radiation beam portion by means of the beam affecting arrangement and transferred to an adjacent bending die. In case of such a bending die arrangement, there are thus two or several radiation beams passing through the bending dies one after another and in each bending die, one proportion of each radiation beam is deflected onto the workpiece and another proportion is transferred to the next bending die. This insertion of at least two concentrated radiation beams into the die arrangement also allows the usage of a radiation source emitting a non-polarized radiation that means for example the usage of a solid-state laser, the radiation of which is, already before the die arrangement, split into two approximately equal but different polarized radiation beams by a polarization beam splitter. Within each of the die arrangements, radiation beam portions of defined radiation intensities can be decoupled from said radiation beams and deflected onto the workpiece by using further polarization beam splitters. Thereby, also any number of congeneric bending dies can be stringed together to be a die arrangement, with the total length only being limited by the total power of the concentrated radiation beams inserted, because the power of radiation beam portions transferred gradually or progressively decrease in their course due to the parts decoupled and deflected onto the workpiece. By the insertion of two concentrated radiation beams into one bending die, particularly two uncouplings, being arranged offset one after another in the distribution direction of the radiation beams, can be effected into the direction of the workpiece, with the result that elongate planar fanned beams hit the bottom side of the workpiece in the deformation zone one after another or stringed together overlapping each other.
The beam affecting arrangement mounted in the interior of the bending die can comprise two or more beam splitter elements being arranged one after another within a beam path and having decreasing transmittances and increasing reflectances The first beam splitter element can for example have a transmittance of 50% and a second beam splitter element can have a transmittance of 0%, with the result that at the first beam splitter element 50% of the radiation power is guided onto the workpiece and at the second beam splitter element also 50% of the radiation power is guided onto the workpiece. In case of an arrangement with three beam splitter elements, the first beam splitter element has a transmittance of 66%, the second beam splitter element has a transmittance of 50% and the third beam splitter element has a transmittance of 0%, with the result that 33% of the original radiation power are decoupled towards the workpiece at every beam splitter element. The last beam splitter of such a beam affecting arrangement is thus embodied to be a 100% reflecting beam splitter or a mirror.
For the decoupling of concentrated radiation beam portions from the inserted concentrated radiation beam within the bending die, polarization beam splitter can advantageously be used, which allow to variably mutually affect the proportion of radiation beam portions having been let pass and radiation beam portions having been deflected when using polarizing filter elements or half-wave plates.
As a further means for the decoupling of beam portions, variable coated beam splitter plates with decreasing transmittances or so-called FTIR elements are possible that comprise two 45° prisms being pressed to one another by a piezo adjusting element and that have different transmittances depending on the size of an adjustable air gap between the two prisms, so as to adjust the transmission with the help of the piezo tension that will be described below.
Because a local heated workpiece can be easily deformed due to thermal warping, it is advantageous if the workpiece is clamped by a bending punch cooperating with the bending die during the application of high-energy radiation. Thus it is ensured that the workpiece stays in the position planned during the heating by high-energy radiation and the bending is carried out exactly at the bending line planned.
For the application of the method, advantageously a solid-state laser, for example a Nd:YAG laser device or a gas laser, for example a CO2 laser device, being characterized by their high beam power and already exist in many production plants, can be used as radiation source.
In order to be able to control the local heating of the workpiece to be bent better it is advantageous if the power emitted by the radiation source and/or the exposure duration of the radiation at the material and/or the geometric dimensions of the workpiece to be bent are adjustable by means of a control device. In this case, the control device used therefor can be realized by the control device of the bending press as well as the control device of the radiation source or as an own control device.
At least two beam paths can be arranged spaced apart from and parallel to one another in the bending die, and each beam path can be made of own channels or bores in the tool base body or they can also extend in a common beam channel or a corresponding hollow space in the interior of the bending die. Thus, the several beam paths for several radiation beams can follow a common beam entry opening or several own beam entry openings. Due to the fact that the beam paths are spaced apart from one another, the each of single radiation beams can be deflected to different positions of the workpiece by an own beam affecting arrangement, particularly beam splitter elements and/or beam deflectors, arranged in the respective beam path, with the result that an even distribution of the radiation power along the deformation zone of the workpiece can be effected. Preferably a prism, a mirror or a beam splitter element can be used as a beam deflector in this case.
For the widening of the beam, the beam affecting arrangement comprises preferably at least one cylindrical lens that causes that a line-shaped beam or a line-like radiation beam is expanded to be a planar fanned beam extending in a plane, preferably in the bending plane, with the result that the beam power of the single concentrated radiation beam or radiation beam portion is spread over a elongate area. The cylindrical lens can also be used to fan a beam already fanned further in the same beam plane, if the cylindrical lens has an axis of curvature perpendicular to the beam plane and thus the plane of the fanned planar fanned beam is not changed.
In a further advantageous embodiment, the beam affecting arrangement comprises at least one beam splitter element for producing at least two radiation beam portions, with the result that one proportion of the concentrated inserted radiation beam can be used for the local heating of the workpiece and the second radiation beam portion can either be used for heating the workpiece within the same bending die, too or is available to be transferred to a next bending die.
The beam splitter element in the bending die can comprise a half-wave plate that is rotatable around the optical main axis and has a motorized drive, for example in form of a stepper motor. Using this half-wave plate, the polarization plane of a concentrated, polarized radiation beam can be rotated and thus the level of decoupling can be varied. Such a variable beam splitter element for polarized radiation beams thus comprises a rotatable half-wave late and a polarization beam splitter element.
In the case of using beam splitter elements basing upon polarization, particularly polarizing beam splitter cubes, alternatively to the a half-wave plate rotated by a stepper motor, also the usage of a so-called Pockels cell, a photoelastic modulator or an optical element being mechanically energized may be suitable for checking the polarization.
A Pockels cell bases upon an electro-optical effect, with a refractive index of the medium, for example a crystal built up from lithium-niobate, being changed under the influence of a variable electric field and thus enabling a variable polarization rotation. However, for achieving this effect, relatively high voltages are necessary, which are nevertheless technically well controllable.
A photoelastic modulator bases upon the photoelastic effect that is used in photoelasticity is used to show stress conditions in transparent items. Due to mechanic stresses, the polarization effect of such a modulator can be changed. The mechanical stresses can in this case be accomplished by the optical effective element itself being designed as a piezo actuator, which causes a photoelastic effect in itself when appropriate voltage is applied. By appropriate modulation of this voltage, a high-frequency polarization modulation can be produced and thus a variable level of decoupling can be achieved.
Alternatively, also an isotropic transparent optical element can be used, which is mechanically energized by screws or piezo actuators so as to effect an artificial birefringence with an effect similar to that of a half-wave plate and a corresponding split of a polarized radiation beam due to the photoelastic effect.
All electrically controllable variants (FTIR with piezo actuator, stepper motor for half-wave plate, Pockels cell, photoelastic modulator, isotropic material under mechanical stress by piezo actuator) are well applicable for an automated control by means of a feedback circuit, which measures the intensity of a decoupled radiation beam portion and from this signal generates a control signal for the controllable beam splitter element or the polarization controlling unit connected ahead to automatically achieve an even distribution of performance between all radiation beam portions.
As a reference signal for each feedback circuit can probably serve the performance measurement of the last radiation beam portion, which is completely deflected by a reflecting beam splitter element or mirror, so that all feedback circuits try to obtain the same performance for their beam portion as in the last radiation beam portion. This of course assumes a sensible choice of regulation parameters or amplification to avoid a chaotic oscillating of said control.
Beam splitting elements that are also suitable for non-polarized radiation beams can for example be formed by using an FTIR element (frustrated total internal reflection) with a piezo actuator for adjusting the width of the slot.
Another possibility is to use as a beam splitter element a so-called Powell lens, which can also be used to decouple a radiation beam portion from a concentrated radiation beam. A Powell lens has a aspheric profile in one coordinate direction, and is flat in the coordinate orthogonal thereto so that a nearly homogenized line-shaped beam field can be formed of a radiation beam portion and used as a planar fanned beam.
By means of these optical elements the proportion of the radiation let pass and deflected decoupled radiation can be variably changed with the result that the distribution of the beam power can be adjusted to workpiece or to the combination of bending dies used in a die arrangement. By a beam splitter element of this kind, the intensities of the produced radiation beams can be mutually affected.
By a beam splitter element that, viewed in the direction of the beam distribution, comprises a half-wave plate and a following polarization splitter element, an advantageous arrangement of beam splitting stages can be formed in the following way: an entering concentrated radiation beam is brought into the non-polarized possible state by means of a depolarizer and subsequently split up into two equal linear polarized beam portions by means of a first polarization filter, if applicable already outside of the bending die. By the half-wave plate the polarization plane of the beam portions can be rotated and together with the subsequent polarization splitter element letting pass unhindered the linear polarized beams in a defined polarization plane and reflects beams perpendicular thereto, the polarization plane of the radiation beam portion can be adjusted by rotating the half-wave plate, with the result that also the proportion of the beam power reflected of let pass by the polarization splitter element can be influenced actively. Thus, the respective decoupled beam intensity can be adjusted to number of the required decouplings by the corresponding adjustment of the beam splitter elements.
The bending recess of a bending die according to the invention is formed of an elongate, in particular a V-shaped groove, with the result that the bending die can be used for the universally applicable air bending. The beam path of the concentrated and not deflected radiation beam or radiation beam portion in this case extends in the interior of the tool base body, approximately parallel to the groove. Due to this orientation of the beam path within the tool base body, bending dies of this kind can be stringed together in a simple manner to be a die arrangement that is adjusted to the dimensions of workpieces.
The beam affecting arrangement of the bending die can furthermore comprise at least one collimation lens in the beam path of at least one radiation beam or the radiation beam portions, with the result the inevitable occurring beam widening in a beam path can be compensated. Thus, the radiation beam also extends concentrated and with high energy density over longer distances.
The beam affecting arrangement arranged in the beam path of a radiation beam or a radiation beam portion preferably comprises a half-wave plate, at least one cylindrical lens as well as one prism each for forming the beam, with the half-wave plate being used for rotating the polarization plane of a decoupled or deflected radiation beam or radiation beam portion and the prism being used for deflecting and/or distributing of the planar fanned beam. By means of prisms, the fanned beam portions are deflected essentially within a common distribution plane, preferably within the bending plane to the bending line or the deformation zone of the workpiece. By this combination of optical elements the advantageous deformation of a concentrated radiation beam to at least one planar fanned beam suitable for the heating of a line-shaped deformation zone and a possible required deflection of the planar fanned beam can be realized using simple means.
The passing through at a prism is effected at least approximately to the Brewster angle, at which only a little loss of reflection occurs.
The beam affecting arrangement can also be formed in such a way as to comprise a beam splitter element, splitting up concentrated radiation beams into two or more radiation beam portions, and a beam forming element which is arranged between the beam splitter element and the beam exit opening and which spreads at least a radiation beam portion radiated by the beam splitter element into the region of the deformation zone of the workpiece. Lenses, mirrors, prisms in all suitable embodiments can be used as beam forming elements here.
To simplify the arrangement of a die arrangement made up of several bending dies it is advantageous if the beam path within the tool base body runs from the beam entry opening to the beam affecting arrangement and in the following from the latter to a beam transfer opening that can be coupled to a beam entry opening of an adjacent bending die by correspondence of the cooperating dimensions and positions. For this purpose, beam entry opening and beam transfer opening of such a bending die are preferably arranged along a straight line and the beam affecting arrangement is positioned on the connecting line in between.
An advantageous constructional embodiment of the bending die is achieved if the tool base body comprises at least two flat tool sections that are parallel to and spaced apart from one another and a beam affecting arrangement is positioned between. The beam affecting arrangement is thus extensively included within the interior of the tool base body and the beams run in the beam paths defined or limited by the tool base body, with the result that an uncontrolled emission of radiation probably endangering an operator is avoided to a large extend. Due to the flat tool sections the tool base body has an approximately U-shaped cross section, with the beam affecting arrangement being arranged in the interior of the U and the workpiece to be bent rests on the legs of the U.
The mechanical strength of the bending die according to the invention can substantially be increased if at least one spacer element and at least one clamping element clamping the tool base body against the spacer element are arranged between the beam affecting arrangements and the beam exit opening. An expansion of the bending die by the bending punch can thus be counteracted, in fact, the better, the closer the spacer element or the spacer elements are positioned at the beam exit opening or the bending recess. In the event of a failure, these spacer elements furthermore cause an additional safety from a penetration of the bending punch into the interior of the bending die, what could have the result that the latter and in particular the beam affecting arrangement could be destroyed.
In order to be able to employ a bending die according to the invention at most possible bending presses or press brakes, it is advantageous if the tool base body at its end section facing away from bending recess features a connection profile that can be accommodated in a standard tool holder. In this case, said connection profile can have additional recesses or grooves, which can probably cooperate with locking elements of the tool holder.
Due to the reason that in case of heating a workpiece heat always drains into cooler areas that are not exposed to the radiation and thus into the bending die, it is advantageous if the contact surface of the bending die is made of a material with a lower coefficient of heat-conductivity than the tool base body. For this purpose, the contact surface can for example be formed of strip-shaped PEEK-plastics elements or other heat insulating materials that are fixed to the top face of the tool base body. The lay-on points, effective after the beginning of the deformation process and cooperating with the workpiece can be positioned at the tool base body itself for stability reasons.
In order to further reduce the heat flow, at least sections of the tool base body can be formed of a metal with a low coefficient of heat conductivity. Because the heat expansion of the tool base body arising from the increase of temperature of the bending die should be furthermore kept as small as possible, it is furthermore advantageously possible to produce the tool base body of a metal with a low coefficient of thermal expansion.
Because not every workpiece covers the entire bending recess, because its bending length is shorter than the length of the bending die and an emission of high-energy radiation next to the workpiece should be avoided due to job security reasons, in case of an advantageous embodiment of the bending die at least one adjustable shielding element for covering sections not being covered by the workpiece is provided between the beam exit opening and the contact surface. Said shielding element can be embodied as a slider adjustable along the bending recess and, depending on the bending length of the workpiece, the part of the bending recess that is not covered by the workpiece is thus covered by the shielding element.
A bending die according to the invention can be such embodied that the tool base body comprises a die adaptor creating the contact surface and the bending recess, with the die adaptor being exchangeable arranged at the remaining part of the tool base body which contains the beam affecting arrangement. By exchanging the die adaptor the tool base body can thus be adjusted to different bending tasks. It is particularly possible to change the die width, which causes the range of application of such a bending die to be substantially larger. Furthermore, such a bending die being relatively expensive due to the inserted beam affecting arrangement, can be applied more frequently and thus more cost-effectively.
A constructional advantageous longitudinal dimension of a bending die according to the invention is preferably 100 mm, with the result that in the interior of the tool base body sufficient space for the mounting of common and easily obtainable optical components is given and that half-wave plates, beam splitter prisms, polarization beam splitter collimation lenses, cylindrical lenses etc. are obtainable at low prices. A bending die length of 100 mm allows at a total height of the bending die of for example 120 mm the insertion of two concentrated radiation beams from each of which one radiation beam portion can be decoupled spacially offset one behind another.
In order to deform also workpieces exceeding the length of the bending die, it is possible to connect a number of bending dies according to the invention directly adjacent and in particular variants of embodiment of bending dies with decoupling and transferring radiation beam portions are suitable, because in this case only one radiation source is required.
In case of such a die arrangement, adjacent bending dies can be axially clamped against each other by means of at least one axially effective clamping element, with the result that the stability of such a die arrangement is increased and furthermore a beam emission in the region of the front walls is reduced.
A bending die according to the invention or a die arrangement according to the invention made of several bending dies preferably comprises an interface for mechanical connecting and optical coupling with a radiation source to be able to insert a concentrated radiation beam emitted by the latter through the beam entry opening into the bending die.
The method according to the invention or a die arrangement according to the invention can advantageously be used for bending workpieces made of a material chosen from a group comprising magnesium, titanium, aluminum, steel, alloys of these metals, spring steel, glass, plastics.
For a better understanding the invention will be described in more detail by means of the following figures.
In a highly schematically simplified way:
First of all, it should be pointed out that in the variously described exemplary embodiments the same parts are given the same reference numerals and the same component names, whereby the disclosures contained throughout the entire description can be applied to the same parts with the same reference numerals and the same component names. Also details relating to position used in the description, such as e.g. top, bottom, side etc. relate to the currently described and represented figure and in case of a change in position should be adjusted to the new position. Furthermore, also individual features or combinations of features from the various exemplary embodiments shown and described may be construed as independent inventive solutions or solutions proposed by the invention in their own right.
All details relating to ranges of values in this description are to be understood in a way that any and all partial ranges therein are also included, for example the specification 1 to 10 is to be understood in a way that all partial ranges starting at the lower threshold 1 and the upper threshold 10 are included within, that means that any partial ranges start at a lower threshold of 1 or larger and end at an upper threshold of 10 or less, for example 1 to 1.7 or 3.2 to 8.1 or 5.5 to 10.
In
For bending a workpiece 2, the latter is borne against a contact surface 10 of the bending die 3 and pressed into a bending recess 11 within the contact surface 10 by means of the bending punch 5, with the result that the workpiece 2 gets a permanent deformation when stresses exceeding a stress limit or a proportional limit of the material of the workpiece appear. In the exemplary embodiment shown, the bending recess 11 is designed as a V-groove 12 and the bending die 3 thus is designed as a V-shaped die 13. The bending die 5 has a wedge-shaped cross-section, the wedge-angle of which approximately equals the angle of the V-shaped groove 12. The bending recess 11 or the tool base body 7 in general can nevertheless have also any other cross-sectional form that during the bending process allows a supported bearing of the workpiece 2 to be bent at the bending die 3 along two lines between which the bending punch 5 operates. In particular, the bending recess 11 can also have an approximately rectangular cross-section. The bending method performable with such a bending tool arrangement 1 is also called folding and can be performed as air bending or coining.
In the further description the in
Generically, in case of the method according to the invention, before or during the deformation a high-energy radiation 18 partly marked by a dotted line is, in the area of the deformation zone 16, guided through a beam exit opening 17 to the bottom side 19 of the workpiece 2 bearing against the contact surface 10, with the result that the workpiece 2 is locally heated and thus its mechanical-technological characteristics are changed in a way that the bending deformation can be effected with the necessary quality of the finished workpiece 2. The method according to the invention is preferably applied to brittle raw material, in which a reduction of the elastic limit or a proportional limit, for example of the 0.2% elastic strength, can be achieved by heating the material and the workpiece 2 can thus bear the stresses in low scopes necessary for plastic deformation without exceeding the breaking points.
In the further description of the exemplary embodiments, the high-energy radiation 18 is preferably produced by laser radiation, it is however also possible to alternatively or additionally use another kind of radiation distributing according to the laws of optics for the heating of the workpiece 2.
The high-energy radiation 18 hitting the workpiece 2 is in this case produced by a radiation source 20 arranged outside of the bending die 3 or arranged distant from the bending die 3 and is inserted through the beam entry opening 22 in the tool base body 7 into the interior of the bending die 3 in the form of at least one concentrated radiation beam 21.
The diameter of a radiation beam 21 of this kind is usually a few millimeters, concerning the method according to the invention one might assume that the diameter of the concentrated radiation beam 21 is smaller than 20 mm.
The radiation beam 21 extends in the interior of the bending die 3 along the beam path 23, which is for example made of a beam channel 24 implementing the tool base body 7. In the course of the beam path 23, the radiation beam 21 encounters a beam affecting arrangement 25 within the tool base body 7, which deflects, expands and guides the radiation beam 21 through the beam exit opening 17 to the deformation zone 16 of the workpiece 2. In the exemplary embodiment according to
In order to achieve a high level of evenness of the beam distribution and to be able to influence the latter easier for a better adjustment to the workpiece 2, it is however of advantage if the functions beam deflection and beam forming are performed by a respective own optical element. The beam deflector 27 can for example be embodied by a plane mirror, a prism, or any reflecting surface with adequate orientation, whereas the beam forming element 28 can be embodied by a lens, a convex mirror or a concave mirror whereby for the fanning out in a flat planar fanned beam 26, cylindrical optical elements can be used, which are curved in only one direction or are only slightly curved.
In
The beam splitter element 34 is formed of an optical component and splits the inserted radiation beam 21 into the second radiation beam portion 33b, which is transferred without change in direction and the first radiation beam portion 33a, which is deflected by 90°.
The beam splitter element 34 for example comprises a beam splitter plate, a polarization filter, a beam splitter cube, a Pockels cell, a photoelastic modulator, a Powell lens or optical elements that take advantage of polarization optical, photoelastic or electro-optical effects. The effect of the beam distribution can here be effected by optically active materials like for example at polarization filters or by beam splitter layers, like for example at a beam splitter cube, with which a splitting of intensity of the arriving radiation beam 21 can be achieved. Such intensity beam splitters can separate beams of light comprising a certain wavelength but also polycromatic beams of light into a transmitted and a reflected part, with the possibility of different proportions of division. Beam splitter layers can be formed of metallic layers or dielectric multilayers and dielectric multilayers based on polarization effects are well suitable for the method according to the invention.
Beam splitter plates applicable for the method according to the invention are made of a plane-parallel plate of glass, quartz or a uniaxial crystal with a dielectric or metallic coating. Due to the thickness of the beam splitter plates, the transmitting beam is subject to a slight beam displacement.
Beam splitter cubes are made of two 90°-prisms that are cemented to one another at their hypotenuses, and the beam splitting coating is applied to a hypotenuse and the transmitting beam is not subject to be displaced.
FTIR beam splitter elements work on the basis of the “Frustrated Total Internal Reflection” taking advantage of reflection and absorption effects at beam splitter cubes with an air gap between the two 90°-prisms and this form of a beam splitter is well suitable to effect an adjustable beam distribution by adjusting the air gap, for example by means of piezo actuators that can adjust the prisms of the beam splitter relatively towards each other and thus change the air gap, or by direct embodiment of the prisms of transparent piezoelectric metal, for example LiNbO3 that can be influenced concerning its dimensions by application of a voltage.
The planer fanned beams 26a and 26b formed of the radiation beam 21 by the two beam affecting arrangements 25a and 25b are such guided to the bottom side of the workpiece 2 as to overlap each other and the two radiation intensities sum up at the irradiated bending line 15. Because the radiation intensity of a radiation field frequently has a bell-shaped curved distribution, a more even distribution of the radiation along the bending line 15 can be achieved by the overlapping of border zones of adjacent planar fanned beams 26a and 26b. As already described, the first beam affecting arrangement 25 comprises a beam splitter element 34, a beam deflector 27, whereby the two latter can be formed of one single optical element, as well as a beam forming element 28. In the exemplary embodiment shown, the second beam affecting arrangement 25b does not need a beam splitter element 34, because the decoupled second radiation beam portion 33b is completely deflected onto the workpiece 2. However, it is also possible that also the second beam affecting arrangement 25b comprises a beam splitter element 34 if the latter is such adjustable as to deflect and deform the second radiation beam portion 33b completely and without decoupling a further radiation beam portion. The second beam affecting arrangement 25b can in this case be formed identically to the first beam affecting arrangement 25a, the beam splitter element 34 of which is such adjusted, as to split the power to the two radiation beam portions 33a and 33b in a proportion 50:50. Should more than two beam affecting arrangements 25a and 25b be provided in one bending die 3, the beam splitter elements 34a, 34b, 34c, . . . are to be such adjusted as to split the radiation performance of the radiation beam 21 according to the required proportion and several planer fanned beams 26a, 26b, . . . are guided onto the workpiece 2. An even distribution of performance/power between all radiation beam portions 33 reflecting into the direction of the workpiece 2 is achieved if the reflecting proportion of radiation is 1/n at each beam splitter element, with n being the numbering of the beam splitter elements starting at the last element (1=n) and increasing until the first element.
The beam guidance of a die arrangement 37 corresponds in its effect to the beam guidance in a bending die according to
For adjusting to various lengths of a workpiece 2, the shielding element 40 can advantageously be adjustable into the direction of the arrow 41 by means of an adjustment device not shown. A shielding element 40 of this kind could also be provided at the right ending of a die arrangement 37 or a single bending die 3 shown in
The bearing of the shielding element 40 at the workpiece 2 to be bent can be ensured by the fact that it is approached to the workpiece 2 with a certain minimum power, and additionally a mechanical or optical query concerning the contacting of the workpiece and thus the complete shielding of the section 39 can be ensured. This can for example be effected by the fact that the shielding element 40 has a check mark 43 at its end of the top side facing the workpiece and the check mark 43 is supervised by a camera, not shown, mounted above the die arrangement 37. In case of a relocation of the check mark 43 at the shielding element 40 below the edge of the workpiece 2, the check mark 43 cannot be detected anymore from above, from which is deducible that the shielding element 40 rests against the workpiece 2. In this case, the end section with the check mark 43 has a notch in the area of the bending line 15 to allow that it can also be irradiated by the high-energy radiation at the edge of the workpiece 2. Furthermore, in this form of embodiment, the shielding element 40 is mounted moveable into the direction of the double arrow 44, with the result that the shielding element 40 and the workpiece 2 can together be pressed into the interior of the bending recess 11 when am bending process is performed. For this purpose, the shielding element 40 can for example be mounted springy or swiveling and is located in uplifted position without the influence of the bending punch 5. A bending recess 11 with a rectangular inside cross-section simplifies the movability of the shielding element 40 into the interior of the bending recess 11.
In
After being deflected at the polarization beam splitter 50′ at the beam forming element 28a′, the decoupled radiation beam portion 33a′ is expanded within a beam plane by at least one cylindrical diverging lens or cylindrical lens 51, in this case by two cylindrical plano-concave lenses 52 and 53 following one another and, by means of a prism 54, split into two planar fanned beam portions 55L and 55R within the same beam plane with said planar fanned beam portions 55L and 55R being guided onto the workpiece 2 through the beam exit opening 17 in a crossed manner and thus two irradiation zones overlap.
The radiation beam 21″ is split, deflected and deformed by means of the second beam affecting arrangement 25a″ in an analogous manner as the radiation beam 21′.
The two beam affecting arrangements 25a′ and 25a″ furthermore each comprise between the polarization beam splitter 50 and the cylindrical lens 51 one further half-wave plate 56 each, with the help of which the polarization plane of the decoupled radiation beam portions 33a′ and 33a″ can be rotated by 90° to effect the transmission through the cylindrical lenses 51 and the following prism 54 with lowest losses possible, to increase the absorption at the workpiece and to realize that the same polarization (parallel to the drawing layer) as in the case of the last two beam portions is existent.
The position of the diagonal sides of the prisms are so chosen as to the central optical path with the highest intensity impacts on the left and on the right of the exterior edges of the two planar fanned beam portions 55L and 55R, with the result that also at the edge regions of the planar fanned beam portions sufficient high radiation intensities are achieved and in the middle region, directly above the prism 54, the two radiation beam portions 55L and 55R overlap each other with their weakened radiation intensities, with the result that the most even possible radiation intensity for the even local heating of the workpiece 2 is achieved.
In the embodiment described, an approximately even power distribution is given exactly at the bottom side 19 of the undeformed workpiece 2, what is not given during the deformation anymore. By a stronger tilting of the planar fanned beams 26, it is under certain circumstances of advantage to place said position, where the distribution of the radiation 18 is the most even, noticeably below the contact surface 10 or the bottom side 19 of the undeformed workpiece 2, in fact to a place where the bottom side 19 of the workpiece 2 is situated at the end of the bending process, because in this phase the highest stresses occur due to the high level of deformation and especially at this time, an even power input is advantageous to avoid crack formation or breakage at the workpiece 2 caused by too low temperatures at the deformation zone 16.
It is under certain circumstances furthermore of procedural advantage, to start the deformation process firstly with a little cold swing, to stop the bending punch 5 to fixate the workpiece 2 and thus to avoid a deformation caused by thermal stresses during the heating by radiation 18 or to minimize it, then to start the heating and then, after a predetermined period of time that can also be zero, or beginning when the deformation zone 16 obtains a certain temperature to continue the bending process, with also the heating is continued until the termination or short before the termination of the swinging. In case, the predetermined period of time is zero, the complete bending deformation is a continuous process during which the energy input by radiation 18 is effected. The energy input can of course also be switched on right from the start. The controlling of the applied thermal energy is then advantageously effected according to the speed of the deformation process.
The passing of the planar fanned beams 26 through the diagonal faces of the prism 54 is preferably effected close to the so-called Brewster's angle, at which the beams polarized in the plane of incidence leave the prism 54 nearly without losses without reflections within the prism 54. The previously described half-wave plates 56 after the beam splitting elements 34 cause that the polarization planes of the decoupled radiation beam portions 33a′ and 33a″ are turned into the correct orientation to achieve this effect.
Due to the position of the planar fanned beams 26 within the bending die it is furthermore possible that the tool sections 29 and 30 (see
In case of a die arrangement 37 according to the invention, several bending dies 3 of this kind with beam splitter elements 34 can be arranged one after another, if the level of decoupling at the single beam splitter elements 34 are such adjusted as to evenly distribute the total radiation power of the inserted radiation beam 21 to all decoupled radiation beam portions 33 deflected onto the workpiece 2.
At each of the last bending die 3 of a die arrangement 37 of this kind, a bending die 3b is arranged at which no transfer of one or several radiation beam portions 33 to a further bending die 3 is required and thus a beam splitter element 34 deflecting 100% of the radiation power onto the workpiece 2 or a reflective mirror 56 can be used as a beam deflector 27. The tool base body 7 of the two bending dies 3a and 3b can be embodied identically, in case suitable recesses 57 allow that the optical components to be used can be exchanged by those providing other characteristics or optionally mounted or omitted. Thus, in the exemplary embodiment shown, instead of each of the polarization beam splitters 50 mirrors 57 are mounted in the right bending die 3b and between mirror 57 and cylindrical lens 51 no half-wave plate 56 is mounted and a bending die 3b can be reconstructed to be a bending die 3a with comparatively low effort. A bending die 3a suitable for a beam transfer to an adjacent bending die 3a or 3b, can be thus referred to as intermediate die, whereas a terminal bending die 3b can be referred to as terminal die.
Because the effects that can be achieved with the help of optical elements are multiply subject to the wavelength of the used light, the optical elements used in a bending die 3 according to the invention or a die arrangement 37 according to the invention are advantageously adjusted to the composition of light of the radiation source 20 used. Thus, a radiation source 20 in form of a helium-neon laser has for example a wavelength of 633 nm, whereas a Nd:YAG laser has a wavelength of 1064 nm. A CO2 laser, also coming into consideration as an energy source, has a typical wavelength of 10600 nm.
In
The exemplary embodiments show possible variants of embodiment of the method or the bending die 3 and are not intended to limit the scope of the invention to these illustrated variants of embodiments provided herein but that there are also various combinations among the variants of the embodiments themselves and variations regarding the present invention should be executed by a person skilled in the art. All and every imaginable variants of the embodiment, arising from combining single details of the variant of embodiment illustrated and described are subject to scope of protection.
Finally, as a point of formality, it should be noted that for a better understanding of the structure of the devices according to the invention the latter and their components have not been represented true to scale in part and/or have been enlarged and/or reduced in size.
The problem addressed by the independent solutions according to the invention can be taken from the description.
Mainly the individual embodiments shown in
| Number | Date | Country | Kind |
|---|---|---|---|
| A 1012/2009 | Jun 2009 | AT | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/AT10/00236 | 6/28/2010 | WO | 00 | 3/15/2012 |
