IT202100016484A1 - MACHINE TOOL FOR MACHINING SEMI-FINISHED PRODUCTS IN ALUMINUM OR TITANIUM ALLOY - Google Patents

Description

DESCRIPTION

The present invention belongs to the machine tool sector, and in particular to the technical sector of large machine tools, such as a horizontal boring machine or a milling machine or a lathe. In particular, the object of the present invention is a machine tool suitable for machining semi-finished products in aluminum alloy or titanium alloy.

These machine tools are used to perform machining on large semi-finished products for the aeronautical, aerospace and naval industries.

Because of the critical of such industrial applications, extremely tight machining tolerances are generally required. Machine tool manufacturers are therefore constantly engaged in the research and development of solutions that can guarantee these tolerances.

In the specific case of the machining of semi-finished products in titanium alloy it is observed that, during the chip removal operations, the tool develops vibrations with a frequency between 12 and 18 Hz.

Considering that the resonance frequency of machine tools according to the state of the art ? between 14 and 16 Hz, it is evident to the person skilled in the art that the machining of titanium alloys produces vibrations in the resonance range of the machines, which in fact prevent the attainment of the tolerances required by the industrial applications where the finished piece is? intended.

On the other hand, in the specific case of machining semi-finished products in aluminum alloy, compliance with dimensional tolerances requires very long production times. ? it is clear that, by increasing the stiffness of the machine and increasing the value of the first resonant frequency, the dynamic performance of the machine tool would improve and consequently the production times could be reduced without compromising compliance with the required tolerances.

Therefore, in order to meet tolerances and/or improve dynamic performance, machine tools should be stiff enough to ensure a resonant frequency between 23 and 30 Hz.

So far, the efforts made by manufacturers have been directed towards increasing the stiffness of the machines.

Although it is possible to improve the stiffness through an increase in stiffness? of the structures of the machine, this technical prejudice, moreover justified by structural science, has not yet produced any satisfactory results.

Purpose of the present invention? that of realizing a machine tool of large dimensions capable of obviating the drawbacks described above.

That purpose? achieved with a machine tool for machining semi-finished products in aluminum alloy or titanium alloy according to the attached claim 1. The dependent claims identify further advantageous embodiments of the invention.

The characteristics and advantages of the machine tool according to the present invention will in any case become evident from the following description of preferred embodiments thereof, given by way of non-limiting example, with reference to the attached figures, in which:

- figure 1 ? a perspective view of a machine tool in one embodiment;

- figure 2 ? a perspective view of the machine tool of figure 1 from a different angle; - figure 3 ? a front view of the machine tool of figure 1;

- figure 4 ? a side view of the machine tool of figure 1;

- figure 5 ? an enlarged view of the detail V framed in figure 4;

- figure 6 ? an enlarged view of the detail VI highlighted in figure 1;

- figure 7 ? an enlarged view of detail VII highlighted in figure 1;

- figure 8 ? an enlarged view of detail VIII framed in figure 4;

- figure 9 ? a perspective view of wagon translation means actuated by a first pair of gearmotors for moving the wagon or by a second pair of gearmotors for moving the wagon; - figure 10 ? a sectional view of the wagon translation means shown in figure 9;

- figure 11 ? a sectional view of a portion of the end? of the wagon translation means which can be operated by the first pair of gearmotors for moving the wagon or by the second pair of gearmotors for moving the wagon;

- figure 12 ? an enlarged view of detail XII boxed in figure 10, e

- figure 13 ? an enlarged view of detail XIII boxed in figure 10.

In the continuation of the description, elements common to the various embodiments shown in the drawings are indicated with the same reference numerals.

With reference to the figures in the attached tables, with 1 yes ? indicated as a whole a machine tool suitable for machining semi-finished products in aluminum alloy or titanium alloy.

In a general embodiment, the machine tool 1 for machining aluminum alloy or titanium alloy semi-finished products? intended to be placed on a horizontal reference plane G, for example the ground plane. This machine tool 1 comprises a support structure 2, an upright 4, a carriage 6 and a work head 7.

The support structure 2 comprises a bench 20 and a rear support 22. The bench 20 has a prevalent extension along a longitudinal direction X, while the rear support 22 extends both along the longitudinal direction X and along a vertical direction Y.

The bench and the rear support are rigidly connected to each other, i.e. engaged and made integral. For example, the bench 20 and the rear support 22 are connected in such a way that the support structure 2 has an "L"-shaped cross section, where this cross section is understood to be obtained along a plane orthogonal to the longitudinal direction X.

The support structure 2 ? also equipped with upright translation means 3 oriented according to the longitudinal direction X.

Pillar 4? connected to the support structure 2 by means of upright translation means 3, so as to translate along the longitudinal direction X. This upright 4 ? also equipped with carriage translation means 5 oriented according to the vertical direction Y.

Chariot 6 ? connected to the post 4 by means of the carriage translation means 5, so as to be translatable along the vertical direction Y.

The working head 7 ? engaged to the carriage 6 and carries a tool holder seat 70 suitable for housing a tool for chip removal operations.

The machine tool 1 also comprises a first pair of gearmotors for moving the carriage 61, 62 and a second pair of gearmotors for moving the carriage 63, 64. These first pair 61, 62 and the second pair of gearmotors for moving the carriage 63, 64 are positioned on board of upright 4 and are engaged to the carriage translation means 5.

In one embodiment, the carriage translation means 5 comprise a first ball screw 5? and a second ball screw 5?.

According to one embodiment, the first ball screw 5? ? driven by the first pair of gearmotors for moving the carriage 61, 62, while the second ball screw 5? ? driven by the second pair of gearmotors for moving the carriage 63, 64.

Preferably, the first 5 ball screw? ? equipped with a first nut 51 and the second ball screw 5? ? equipped with a second scroll 52. In particular, these first 51 and second scroll 52 are respectively connected to opposite sides of the carriage 6.

For example, considering that the workhead 7 ? engaged to the carriage 6, the first 51 and the second 52 nut are connected to the carriage 6 so as to be arranged at the sides of the working head 7.

In accordance with an embodiment, the first pair of gearmotors for moving the carriage 61, 62 comprises a first pair of electric motors 610, 620 and a first reduction unit 615, where each electric motor of this first pair of electric motors is equipped with a first crankshaft 611; 621 which engages the first reduction unit 615. The second pair of gearmotors for moving the carriage 63, 64 in turn comprises a second pair of electric motors 630, 640 and a second reduction unit 635, where each electric motor of this second pair of electric motors ? equipped with a second crankshaft 631; 641 which engages the second reducer 635.

Preferably, the first pair of gearmotors for moving the carriage 61, 62 exclusively comprises the first pair of electric motors 610, 620 and the first reduction unit 615, while the second pair of gearmotors for moving the carriage 63, 64 exclusively comprises the second pair of electric motors 630, 640 and the second reducer 635.

In figure 11 ? illustrated the kinematic chain of engagement between the first (or second) pair of electric motors and the first (or second) reduction unit.

According to one embodiment, a main electric motor 630 belonging to the first 61, 62 or to the second pair of geared motors for moving the carriage 63, 64? a master, while the remaining three electric motors 610, 620, 640 of the first 61, 62 and of the second pair of gearmotors for moving the carriage 63, 64 are slaves.

Therefore, the actuation of the translation of the carriage 6 along the vertical direction Y ? driven by a master-slave architecture.

Preferably, upright 4 also comprises a pair of vertical guides 9 on which carriage 6 slides. For example, this pair of vertical guides 9? a pair of vertical sliding rails, i.e. oriented along the vertical Y direction.

In one embodiment, the machine tool 1 also comprises a vertical position transducer 90, for example an optical ruler, to detect the position of the carriage 6 with respect to the post 4.

Preferably, the vertical position transducer 90 is associated with a vertical guide of the pair of vertical guides 9.

In accordance with one embodiment, the vertical position transducer 90 is positioned parallel to a vertical guide of the pair of vertical guides 9. Furthermore, this vertical position transducer 90 ? arranged along the vertical direction Y, so as to be substantially vertically aligned with the main electric motor 630.

Preferably, both the first 5? that the second ball screw 5? they comprise a lower support 5a and an upper support 5b. In this case, the lower support 5a ? represented in figure 13, while the upper support 5b ? represented in figure 12.

According to one embodiment, the machine tool 1 also comprises four pairs of geared motors 81, 82, 83, 84 which are positioned on board the upright 4 and engage the upright translation means 3.

In an embodiment represented in the attached figures 6 and 7, the upright translation means 3 comprise a first pair of upright translation members 31 fixed to the bench 20 and a second pair of upright translation members 32 fixed to the rear support 22.

According to an embodiment illustrated in the attached figures 1 and 2, a first pair of gearmotors 81 and a second pair of gearmotors 82 of the four pairs of gearmotors 81, 82, 83, 84 engage the first pair of upright translation members 31. Instead , a third pair of gearmotors 83 and a fourth pair of gearmotors 84 of these four pairs of gearmotors 81, 82, 83, 84 engage the second pair of upright translation members 32.

In one embodiment, the first 81 and the third pair of gearmotors 83 are positioned on a first side 41 of the upright 4, while the second 82 and the fourth pair of gearmotors 84 are positioned on a second side 42 of the upright 4 opposite the first flank 41.

These first 41 and second sides 42 are lateral with respect to the position of the carriage translation means 5 on which the carriage 6 translates.

According to one embodiment, a first main gearmotor 831 belonging to the first 81 or to the third pair of gearmotors 83 ? a master, while the remaining three gearmotors of the first and third pair of gearmotors are slaves. Furthermore, a second main gearmotor 842 belonging to the second 82 or to the fourth pair of gearmotors 84 ? one master, while the remaining three gearmotors of the second and fourth pair of gearmotors are slaves.

Preferably, the first main gearmotor 831 belongs to the third pair of gearmotors 83 and is located near of a? extremity? top 22? of the rear support 22. The second main gearmotor 842 belongs to the fourth pair of gearmotors 84 and ? located near of? end? top 22?.

In particular, both on the first side 41 and on the second side 42 of the upright 4? present a master-slave architecture.

In one embodiment, each mast translation member of the first 31 and second pair of mast translation members 32 ? a rack. Furthermore, each geared motor of each of the four pairs of geared motors 81, 82, 83, 84 comprises an upright translation electric motor 800 and a reduction unit 802. The upright translation electric motor 800 has a drive shaft M which ? parallel to the vertical direction Y. The reducer 802 has an input engaged with the upright translation electric motor 800 and an output engaged with the rack.

In the attached figures 5-8 ? illustrated the kinematic chain, where each organ of translation uprights? a rack fixed to the support structure and where each gearmotor? fixed on the edge of upright 4 and engages the rack.

Preferably, the input and output of the reducer 802 are coaxial to the motor shaft M and the output comprises a toothed wheel which meshes with the rack.

According to one embodiment, ? there is a GANTRY control between each master and the respective slaves.

Therefore, ? a GANTRY control is present both on the first side 41 and on the second side 42 of the upright 4. Furthermore, also between the first 61, 62 and the second pair of gearmotors for moving the carriage 63, 64? there is a GANTRY control.

GANTRY control is implemented on master-slave architectures where, by means of MIMO (Multiple-Input and Multiple-Output) communication, the slave gearmotors follow the positions commanded by the master and send their feedback data to the master, so as to achieve closed-loop control. In one embodiment, the workhead 7 is rotatable about a pitch axis A and about a roll axis C.

According to an embodiment illustrated in figure 4, the tool holder seat 70 is rotatable around a tool axis T.

It is observed that, in virtue? of the type of machining to be carried out on the semi-finished product, the tool axis T pu? be collinear or incident with the roll axis C.

In one embodiment, the bench 20 also comprises a first pair of guides 201 on which the upright 4 slides.

Furthermore, the rear support 22 extends between one? lower than 22? connected to bank 20, and a? end? top 22? where, at that end? upper, the second pair of upright translation members 32 and a second guide 202 on which the upright 4 slides are positioned.

In an embodiment represented in the attached figures 1 and 2, in an intermediate position between the extremity top 22? and the? extremity? lower than 22? ? positioned at least a third guide 203 that ? fixed to the rear support 22 and upright 4 slides on it.

Preferably, this third guide 203 ? spaced vertically, i.e. along the vertical direction Y, from the second pair of upright translation members 32.

In particular, the first pair of guides 201, the second guide 202 and the third guide 203 are longitudinal sliding tracks, i.e. oriented along the longitudinal direction X.

According to an embodiment, both the first 31 and the second pair of upright translation members 32 extend along the longitudinal direction X between a first end? 3? and a second end? 3? opposite to the first 3?. At such before 3? and second end? 3? ? associated with a position transducer 30, for example an optical scale.

Innovatively, the machine tool object of the present invention fulfills the intended purpose, as it achieves such a stiffness that the first resonant frequency ? between 24 and 30 Hz.

Analytically, following software simulations for finite element analysis (FEA) of the machine tool object of the present invention, yes? calculated that the first resonant frequency ? at about 30 Hz. Considering that the value obtained ? the result of a model that represents a simplification of reality?, yes ? decided in favor of safety to consider the 80% of the calculated value. Therefore, the first conservatively calculated resonant frequency ? equal to 24 Hz, i.e. 80% of the result obtained through FEA simulations.

Advantageously, the machine tool object of the present invention ? more stiffness of machine tools according to the state of the art.

Contrary to technical prejudice, which sought to improve the stiffness of the machines by increasing only the stiffness? of the structures, in the present invention the degrees of constraint between the upright and the carriage translation means have been increased.

Furthermore, the degrees of constraint between the upright and the support structure have also been increased.

Have the increase in stiffness and in the value of the first resonant frequency been achieved when? passed from the solution with only two gearmotors meshed with the wagon translation means, contemplated by the state of the art, to the present invention in which a first and a second pair of gearmotors for moving the wagon engaged with the wagon translation means have been introduced. Therefore, yes? passed from two to four degrees of constraint between the upright and the wagon translation means.

Analytically yes? observed that the increase in the degrees of constraint between the upright and the carriage translation means produces an increase in the resonance frequency such as to be able to work the titanium alloys in absolute safety and in compliance with the required tolerances. In other words, yes? observed that by replacing each gearmotor of the state of the art with a pair of gearmotors for moving the cart more? small, the overall stiffness of the machine increases considerably and its dynamic performance improves.

According to an advantageous aspect, the machine tool object of the present invention ? safe, as it operates on frequencies far from the resonance frequency of the machine itself.

According to an even further advantageous aspect, the machine tool object of the present invention has a manufacturing cost lower than or comparable to machine tools according to the state of the art.

? it is clear that a person skilled in the art, in order to satisfy contingent needs, could make modifications to the machine tool described above, or replace elements with other functionally equivalent ones, without however departing from the scope of protection of the following claims. Each of the characteristics described as belonging to a possible embodiment can? be made independently in the other disclosed embodiments.

Claims (19)

1. Machine tool (1) suitable for machining semi-finished products in aluminum alloy or titanium alloy and intended to be placed on a horizontal reference plane (G), for example the ground plane, said machine tool comprising: - a support structure (2) comprising a bench (20) having a prevalent extension along a longitudinal direction (X), and a rear support (22) extending both along the longitudinal direction (X) and along a vertical direction (Y ), in which the bench and the rear support are rigidly connected to each other, and in which the support structure (2) ? equipped with upright translation means (3) oriented according to the longitudinal direction (X); - an upright (4) connected to the support structure (2) by the upright translation means (3) in such a way as to translate along the longitudinal direction (X), said upright (4) also being equipped with carriage translation means ( 5) oriented according to the vertical direction (Y); - a carriage (6) connected to the upright (4) by means of the carriage translation means (5) so as to be translatable along the vertical direction (Y); - a working head (7) engaged to the carriage (6) and bearing a tool holder seat (70) suitable for housing a tool for chip removal operations, wherein the machine tool also comprises a first pair of gearmotors for moving the carriage (61, 62) and a second pair of gearmotors for moving the carriage (63, 64), where said first pair (61, 62) and second pair of gearmotors for moving carriage (63, 64) are positioned on the edge of the upright (4) and engaged to the carriage translation means (5). 2. Machine tool (1) according to the preceding claim, wherein the carriage translation means (5) comprise a first ball screw (5?) and a second ball screw (5?). 3. Machine tool (1) according to the preceding claim, wherein the first ball screw (5?) ? driven by the first pair of gearmotors for moving the carriage (61, 62) and the second ball screw (5?) ? driven by the second pair of gearmotors for moving the carriage (63, 64). 4. Machine tool (1) according to claim 2 or 3, wherein the first ball screw (5?) ? equipped with a first nut (51) and the second ball screw (5?) ? equipped with a second nut (52), where said first (51) and second nut (52) are respectively connected to opposite sides of the carriage (6). 5. Machine tool (1) according to any one of the preceding claims, wherein the first pair of gearmotors for moving the carriage (61, 62) comprises a first pair of electric motors (610, 620) and a first reduction unit (615), where each electric motor of said first pair of electric motors ? equipped with a first drive shaft (611; 621) which engages the first reduction unit (615), and in which the second pair of gearmotors for moving the carriage (63, 64) comprises a second pair of electric motors (630, 640) and a second reduction unit (635), where each electric motor of said second pair of electric motors ? equipped with a second drive shaft (631; 641) which engages the second reduction unit (635). 6. Machine tool (1) according to any one of the preceding claims, wherein a main electric motor (630) belonging to the first (61, 62) or to the second pair of geared motors for moving the carriage (63, 64)? a master and the remaining three electric motors (610, 620, 640) of the first (61, 62) and of the second pair of gearmotors for moving the carriage (63, 64) are slaves. 7. Machine tool (1) according to any one of the preceding claims, wherein the upright (4) also comprises a pair of vertical guides (9) on which the carriage (6) slides. 8. Machine tool (1) according to any one of the preceding claims, also comprising a vertical position transducer (90), for example an optical ruler, for detecting the position of the carriage (6) with respect to the post (4). 9. Machine tool (1) according to any one of the preceding claims, also comprising four pairs of geared motors (81, 82, 83, 84) positioned on the edge of the upright (4) and engaged to the upright translation means (3). 10. Machine tool (1) according to any one of the preceding claims, wherein the upright translation means (3) comprise a first pair of upright translation members (31) fixed to the bench (20) and a second pair of members upright translation system (32) fixed to the rear support (22). 11. Machine tool (1) according to the preceding claim, wherein a first pair of gearmotors (81) and a second pair of gearmotors (82) of said four pairs of gearmotors (81, 82, 83, 84) engage the first pair of upright translation members (31) and where a third pair of gearmotors (83) and a fourth pair of gearmotors (84) of said four pairs of gearmotors (81, 82, 83, 84) engage the second pair of translation members upright (32). 12. Machine tool (1) according to the preceding claim, wherein the first (81) and third pair of gearmotors (83) are positioned on a first side (41) of the post (4) and wherein the second (82) and the fourth pair of gearmotors (84) are positioned on a second side (42) of the upright (4), opposite the first side (41). 13. Machine tool (1) according to the preceding claim, wherein a first main gearmotor (831) belonging to the first (81) or to the third pair of gearmotors (83) ? a master and the remaining three gearmotors of the first and third pair of gearmotors are slaves, and wherein a second main gearmotor (842) belonging to the second (82) or fourth pair of gearmotors (84) ? one master and the remaining three gearmotors of the second and fourth gearmotor pair are slaves. 14. Machine tool (1) according to any one of claims 10 to 13, wherein each mast translation member of the first (31) and second pair of mast translation members (32) ? a rack, and in which each gearmotor of the four pairs of gearmotors (81, 82, 83, 84) comprises an upright electric translation motor (800), having a motor axis (M) parallel to the vertical direction (Y) and a reduction gear (802) having input engaged with the mast translation electric motor (800), and output engaged with the rack. Machine tool (1) according to any one of the preceding claims in combination with claim 6 or 13, comprising a GANTRY control between each master and the respective slaves. 16. Machine tool (1) according to any one of the preceding claims, wherein the work head (7) is rotatable about a pitch axis (A) and a roll axis (C). 17. Machine tool (1) according to any of claims from 10 to 16, wherein the bench (20) also comprises a first pair of guides (201) on which the upright (4) slides, and wherein the rear support ( 22) extends between a? extremity? lower (22?) connected to the bank (20), and a? end? upper (22?) where, in correspondence of said extremity? superior, ? positioned the second pair of upright translation members (32) and a second guide (202) on which the upright (4) slides. 18. Machine tool (1) according to the preceding claim, wherein in an intermediate position between the end? upper (22?) and the? extremity? lower (22?) ? positioned at least a third guide (203) fixed to the rear support (22) and on which the upright (4) slides. 19. Machine tool (1) according to any one of claims 10 to 18, wherein both the first (31) and the second pair of upright translation members (32) extend along the longitudinal direction (X) between a first end ? (3?) and a second extremity? (3?) opposite the first (3?), said first (3?) and second extremity? (3?) being associated with a position transducer (30), for example an optical scale.