IT202000021970A1 - WORK CENTER - Google Patents

Description

WORK CENTER

DESCRIPTION

Background of the invention

The present invention refers to the field of numerically controlled machining centres, particularly but not exclusively belonging to the woodworking sector.

Pi? in particular, the subject of the invention are work centers for machining pieces, preferably but not necessarily wooden pieces, as well as? methods for machining pieces using the aforesaid work centres.

Related art

From document WO 2014/177997 A1 ? known a numerically controlled work center with three or more? axes comprising two piece-holding tables which can be moved parallel to each other on respective guides and along the first horizontal axis (also called y-axis), and a portal structure, arranged transversally to these guides, on whose two sides, front and rear, are arranged respective working heads equipped with one or more? tool holder spindles.

The working heads can move, for example, according to two axes, i.e. a vertical axis (also called z axis) and a second horizontal axis (also called x axis) orthogonal to the horizontal y axis of movement of the workpiece tables.

In this machining centre, by combining the movements of the piece-holder tables and the heads, it is possible to carry out machining operations on the piece present on each piece-holder table, according to three axes. According to this document, ? It is also possible that the working heads are equipped with rotation movements, for example a rotation around the z axis and a rotation around the x axis, thus obtaining machining according to 5 axes.

From document EP 3269499 ? otherwise? I know a work center comprising:

- a number N of piece-holding tables equal to or greater than three,

- a number N of first guides, which run parallel to a first direction, each table being movable along a respective one of said first guides;

- a number N-1 of second guides, which extend parallel to a second direction transversal to said first direction;

- a number N-1 of working groups, each comprising at least one working head and being movable parallel to said second direction along a respective one of said second guides;

- a number N x (N-1) of work areas in which the work groups can work on the pieces present on said tables; along each first guide, i.e. for a respective table, N-1 work zones being present, one for each work group.

In accordance with the document EP 3269499, in a work center so? configured each workgroup does not operate simultaneously on more? tables, but can? work, according to a programmed work cycle, on all the N piece-holding tables, always operating on one table at a time.

In accordance with what is described in EP 3 269 499, since there is an extra table? compared to the working groups, there would be the possibility? to program the work cycles of the machining center in such a way that one table is in the unloading and loading phase of the piece/s to be machined while the other workgroups are working on the others.

In accordance with the document EP 3269 499, finally, in a work center so? configured the unloading and loading of the pieces would take place in a ?masked? while the work takes place on the other tables, with an increase in productivity? of the work center and a time balancing of the processes.

Summary of the invention

Has the Applicant found that by using the machining center described in EP 3269 499 the objective of increasing productivity? compared to the work center for example disclosed by WO 2014/177997 A1 pu? at most be achieved only in certain circumstances, i.e., when the work groups carry out the same machining on the pieces associated with the workpiece tables (at the same time or at different times), or they carry out different machining but with substantially identical or very close machining times between them.

Otherwise, the desired optimization of machining times and reduction of dead times is somewhat limited also by providing that one table is in the unloading and loading phase of the piece/s to be machined while machining is carried out on the others by work groups. In this case, in fact, there may be one or more? working groups waiting to receive the piece to be worked according to the assigned workings while one or more? of the other working groups are still continuing with their work.

Has the Applicant perceived that ? Is it possible to further increase productivity? of a machining center of the type disclosed by EP 3 269 499 even in the case in which the machining times of the pieces associated with the piece holder tables are substantially different from each other. Has the Applicant perceived that to achieve such an increase in productivity? in the first place it is necessary to have an adequate number of work groups and, in the second place, to appropriately allocate the times for the machining foreseen on the pieces appropriately among the work groups.

In particular, has the Applicant found that the desired increase in productivity? of the work center can? be achieved by providing the work center with a number of work groups equal to the number of piece-holding tables, identifying the maximum processing time among the processing times required by the pieces to be machined and appropriately allocating the processing that requires this maximum processing time.

In particular, according to a first aspect, the present invention relates to a workpiece machining center according to claim 1.

Pi? in particular, the invention relates to a machining center comprising:

- a number N of piece-holding tables, where N ? three or four,

- a number N of first sliding guides of said piece-holding tables extending along a first direction; each piece-carrying table being movable along a respective one of said first guides;

- a number N of structurally independent working groups equal to the number of piece-holding tables, each working group comprising at least one working head and being slidably supported by a portal structure along respective sliding guides associated with said portal structure and extended along a second direction transverse to said first direction; at least two working units being slidably supported on the same side of said portal structure;

- a number N x (N-1) of work zones in which pu? at least one workpiece being carried out by at least one of said work groups on at least one piece associated with each of said piece-holding tables; along each first guide N-1 work zones being present;

- a number N of piece loading/unloading areas, one for each piece-holder table and positioned, each, at one end? of each first guide;

- a?unit? control system programmed to control the movement of the working units and/or piece-holder tables according to a machining program comprising the phases of: a) selecting at least two different machining operations to be carried out on each piece associated with each piece-holder table, each machining having a machining time tW;

b) selecting a maximum processing time (tW)max among the processing times tW of said at least two different processes;

c) dividing the maximum processing time (tW)max of each piece between two work groups of said N structurally independent work groups;

d) carry out at least two different processes on each piece associated with each piece holder table,

wherein the machining having said maximum machining time (tW)max is carried out by the two working groups of said N structurally independent working groups, between which the maximum machining time (tW)max is divided.

In the context of the present description and in the subsequent claims, the characteristic according to which at least two working units are slidably supported on one ?same side? of the portal structure? to be interpreted as meaning that at least two working groups are slidably supported on a front side or on a rear side of said portal structure.

In the context of the present description and in the subsequent claims, the terms ?front? or ?front? and ?rear? they are understood to refer to the components of the work center which, in the configuration of use of the work center, are positioned with respect to the portal structure towards the loading/unloading areas of the pieces and, respectively, on the opposite side of these areas.

In this way, ? it is advantageously possible to optimally distribute the machining to be carried out on the pieces supported by the piece-holding tables by the N structurally independent work groups of the machining center.

In accordance with this first aspect of the invention, in carrying out at least two different machining processes on each piece associated with each piece-holder table, the two work groups which carry out the machining having the maximum machining time (tW)max cooperate between very effectively reducing substantially the dead times of the machining cycle which would otherwise inevitably be created with a significant difference between the maximum machining time (tW)max and the minimum machining time (tW)min of each piece .

In the context of the present description and in the subsequent claims, with the term ?processing cycle? it is intended to indicate the sequence of operations to be performed on a given piece which includes the loading of the piece to be machined on the respective piece-holder table, the execution of the foreseen processes with the relative movements of the piece-holder table and/or of the work groups and the unloading of the worked piece from the respective piece holder table. The machining cycle therefore includes the various dead times due to the waiting times of the working groups, the moving times of the working groups and the piece-holding tables and any tool change times, if foreseen.

In particular, in accordance with this first aspect of the invention, the machining having the maximum machining time (tW)max is partly performed on a first piece associated with a first piece holder table by a first of the aforementioned two work groups between which the maximum machining time (tW)max is divided, while a second of these two working groups simultaneously carries out a different (and shorter) machining on another piece associated with a different piece-holder table.

In this way, when the second of the two working groups between which the maximum machining time (tW)max is divided has finished carrying out the machining programmed for it on the other piece, it can? be moved to the first work table cos? to continue the machining having the maximum machining time (tW)max on the first piece, while the first of the two working groups between which the maximum machining time (tW)max is divided can? start operating on a third piece associated with a different third piece holder table.

At the same time, the remaining machining group (or the two remaining machining groups in the case of a machining center with four workpiece tables and four machining groups) of the machining center can? (or they can) continue working on the remaining piece(s).

The result is an advantageous and significant increase in productivity? of the machining center with a substantial reduction in dead times within the entire process to be performed on the various pieces.

AND? it should be noted that all this is added to a ?masking? of the unloading and loading time of the pieces on the piece-holding tables once the machining foreseen on a certain piece has been completed.

It goes without saying that the advantage in terms of increased productivity? ? as much greater as greater ? the difference between the maximum machining time (tW)max and the minimum machining time (tW)min required to machine each piece, a circumstance that would be even more? penalizing in the case of a known machining center of the type described by EP 3269 499.

In accordance with a second aspect thereof, the present invention relates to a workpiece machining center according to claim 2.

Pi? in particular, in this second aspect the invention relates to a machining center comprising:

- a number N of piece-holding tables, where N ? three or four,

- a number N of first sliding guides of said piece-holding tables extending along a first direction; each piece-carrying table being movable along a respective one of said first guides;

- a number N of structurally independent working groups equal to the number of piece-holding tables, each working group comprising at least one working head and being slidably supported by a portal structure along respective sliding guides associated with said portal structure and extended along a second direction transverse to said first direction; at least two working units being slidably supported on the same side of said portal structure;

- a number N x (N-1) of work zones in which pu? at least one workpiece being carried out by at least one of said work groups on at least one piece associated with each of said piece-holding tables; along each first guide N-1 work zones being present;

- a number N of piece loading/unloading areas, one for each piece-holder table and positioned, each, at one end? of each first guide;

- a?unit? control system programmed to control the movement of the working units and/or piece-holder tables according to a machining program comprising the phases of: a) selecting at least two different machining operations to be carried out on each piece associated with each piece-holder table, each machining having a machining time tW;

b) selecting a maximum processing time (tW)max among the processing times tW of said at least two different processes;

d) carry out at least two different processes on each piece associated with each piece holder table,

wherein the machining having said maximum machining time (tW)max is completely carried out by only one of said N of structurally independent work groups.

In this way, when carrying out at least two different machining operations on each piece associated with each piece-holder table, the work group that carries out all the machining with the maximum machining time (tW)max relieves the workload on the work groups remaining work and substantially reduces the dead times of the processing cycle by limiting the number and entity? of the movements of the remaining work groups during a work cycle.

In particular, in accordance with this second aspect of the invention, the machining having the maximum machining time (tW)max is completely carried out on a first piece associated with a first piece holder table by a single work group while the remaining work groups work can simultaneously carry out different and less lengthy processes on a second and possibly on a third (or fourth) piece associated with a different second and possibly third (or fourth) piece holder table.

For example, in the case of a work center comprising three piece-holding tables and three structurally independent work groups, a second and a third work group can simultaneously carry out at least another different (and shorter) machining on a second piece and on a third piece associated with a different second and third piece holder table.

Also in this case, the result is an advantageous and significant increase in productivity? of the machining center with a substantial reduction in dead times within the entire process to be performed on the various pieces.

AND? it should be noted that also for the machining center in accordance with this second aspect of the invention what is described above is added to a ?masking? of the unloading and loading time of the pieces on the piece-holding tables once the machining foreseen on a certain piece has been completed.

Also in this case, the advantage in terms of increased productivity? ? as much greater as greater ? the difference between the maximum machining time (tW)max and the minimum machining time (tW)min necessary to work each piece so? how more? illustrated above in relation to the machining center in accordance with the first aspect of the invention. In a third aspect thereof, the present invention relates to a method for carrying out mechanical machining using a work center defined according to claim 1, comprising the steps of:

a) select at least two different processes to be carried out on each piece associated with each piece-holder table, each process having a processing time tW;

b) selecting a maximum processing time (tW)max among the processing times tW of said at least two different processes;

c) dividing the maximum processing time (tW)max of each piece between two work groups of said N structurally independent work groups;

d) carry out at least two different processes on each piece associated with each piece holder table,

wherein the machining having said maximum machining time (tW)max is carried out by two working groups of said N structurally independent working groups, between which the maximum machining time (tW)max is divided.

In its fourth aspect, the present invention relates to a method for carrying out mechanical machining using a work center defined according to claim 2, comprising the steps of:

a) select at least two different processes to be carried out on each piece associated with each piece-holder table, each process having a processing time tW;

b) selecting a maximum processing time (tW)max among the processing times tW of said at least two different processes;

d) carry out at least two different processes on each piece associated with each piece holder table,

wherein the processing having said maximum processing time (tW)max is carried out by only one of said N structurally independent working groups.

Advantageously, these working methods achieve the same technical effects as the machining centers according to the first or second aspect of the invention? described above and further illustrated in this document.

The present invention in at least one of the aforementioned aspects can exhibiting at least one of the following preferred characteristics; the latter can in particular be combined with each other as desired in order to satisfy specific application requirements.

In the context of the present description and in the subsequent claims, with the term ?work? or ?machining?, means any mechanical machining operation, with or without material removal, performed on a piece of material (of any shape), such as for example cutting, drilling, milling, squaring, shaping, profiling, contouring, sanding, or the like.

For purposes of the present invention, the shape of the workpiece is not limited except to those shapes that can be fixed, by means of suitable fixing devices, for example with a suction cup or a jaw, to the respective piece-holder table. Thus, for example, the piece to work can? have an elongated shape, for example the leg of a table, a planar shape, for example a slab or a frame of a door or window, and have a dimension in the direction orthogonal to the plane of arrangement on the piece-holder table compatible with the machining to be carried out.

For purposes of the present invention, the material of the workpiece can be be any structural material suitable for being mechanically worked with working tools, such as for example wood, metal, plastic material or any composite material, such as for example agglomerates of fibers glued together or carbon fibre. In a preferred embodiment, the aforementioned step a) provides for the selection of at least three or at least four different processes to be carried out on each piece associated with each piece-holder table.

In this way, ? Is it advantageously possible to achieve the desired increase in productivity? of the machining center together with characteristics of extreme flexibility? operational of the same.

In a preferred embodiment, the overall number of piece-carrying tables and structurally independent work groups of the work center ? three.

In an alternative preferred embodiment, the overall number of piece-holding tables and structurally independent work groups of the work center ? four. In a preferred embodiment, the workgroups are multi-spindle or single-spindle workgroups.

In this way, ? is it advantageously possible to achieve characteristics of extreme flexibility? operating center of the work by equipping the work groups with the number and type of possible tool holder attachments more? suitable according to the processing requirements.

Cos?, for example, on one or more? workgroups can be mounted ?single? (with manual or automatic tool change), ?bi-spindles? with manual or automatic tool change), groups of three, four or five spindles (with manual or automatic tool change), as well as aggregates (angular or axial heads for cutting, milling, shaping, etc.).

Preferably, the spindles of the machining center are electrospindles.

In a preferred embodiment, one of the aforementioned at least two working groups slidably supported on the same side of the portal structure? a single-spindle machining group.

In this case, ? Is it advantageously possible to achieve the desired increase in productivity? by means of a work center configuration that minimizes work center construction and management costs.

In a preferred embodiment, at least one of the aforesaid working groups comprises a working head which can be moved with respect to the piece-holding tables along a plurality of workpieces. of translation and/or rotation axes.

The movement of the working heads of the working groups with respect to the workpiece tables is preferably carried out thanks to the combination:

- the movements of the working groups with respect to the portal structure,

- the movements of the working heads with respect to the portal structure and to the working units slidingly supported on it, e

- of the movements of the workpiece tables with respect to the work groups slidingly supported on the portal structure.

Preferably, the aforementioned portal structure comprises a crosspiece which rests on uprights or other vertical support structures.

The crossbar ? fixed to the respective support structures and each working group ? mobile along the crossbar of the portal structure.

In this way, each work group and the respective work head/s can be moved along a first direction, hereinafter also referred to as axis X perpendicular to the direction of movement of the piece-holding tables.

In turn, each working group can move the respective working head/heads along a further movement direction perpendicular to the movement plane of the workpiece tables, hereinafter also referred to as the Z axis.

Preferably, each working group can move the respective work head/s around the Z axis, in practice the vertical axis, so as to present the tool associated with the work head/s at different angles with respect to the piece to be machined.

In this way, ? it is advantageously possible to carry out machining along oblique directions.

In a preferred embodiment and taking into account the possibility movement of the workpiece tables along the aforementioned axis or horizontal direction Y and in relation to the workgroups, therefore, the workhead(s) of each workgroup can/can therefore be moved with respect to the workpiece tables along three translation axes and two rotation axes.

The work center? in this case of the type with five working axes.

The translation movements of the piece-holding tables, translation and/or rotation of the working groups and of the working heads associated with the latter are preferably controlled by the unit? work center control.

In a preferred embodiment, the machining center comprises a tool holder magazine positioned laterally to one of the aforementioned first sliding guides of the piece holder tables at one end. side of the portal structure. In this way, ? advantageously possible to minimize the tool change times of the working group supported by the portal structure in a position proximal to the tool holder magazine, especially when said working group is a single-spindle machining group.

In a preferred embodiment, the maximum machining time (tW)max of the workpiece is between 1.2 and 2 times the minimum machining time (tW)min of said piece.

Within the scope of the present description and in the subsequent claims, all the numerical quantities indicating quantities, parameters, percentages, and so on via are to be intended in all circumstances preceded by the term ?about? unless otherwise indicated. Furthermore, all ranges of numerical quantities include all possible combinations of maximum and minimum numerical values and all possible intermediate ranges, in addition to those specifically indicated below.

Under these circumstances, ? is it advantageously possible to maximize the increase in productivity? of the machining center compared to a known type of machining center, for example the one described in document EP 3269 499, thanks to the marked reduction in the dead times of the machining cycle (i.e. the times in which the machining groups are waiting for the piece to work).

Advantageously, this marked reduction in downtime in the machining cycle can be achieved thanks to the fact that the machining with the maximum machining time (tW)max is carried out, in accordance with the invention, by two working groups that share this machining, or by a single working group which relieves the remaining groups of work from the processing pi? long to do.

In a preferred embodiment, the maximum machining time (tW)max of each piece is divided between the above two working groups of said N structurally independent working groups so that one of said two working groups carries out a fraction included between 20% and 80% of said maximum processing time (tW)max. Pi? Preferably, the maximum processing time (tW)max of each piece is divided between the above two working groups of said N structurally independent working groups so that one of said two working groups carries out a fraction between 40% and 60% of said maximum processing time (tW)max.

In this way, ? is it advantageously possible to maximize the increase in productivity? of the machining center with respect to a known type of machining center by distributing in an appropriate manner, and depending on the machining to be performed, the maximum machining time (tW)max of each piece between the aforementioned two machining groups of said N groups of between which the maximum machining time (tW)max is divided.

Advantageously, this division of the maximum machining time (tW)max can? be carried out in a very flexible way by appropriately programming the? unit? control of the work center cos? to satisfy the pi? diverse application needs. In a preferred embodiment, in the aforementioned step c) the maximum machining time (tW)max of each piece is divided between two work groups slidably supported on the same side of the portal structure.

In this case, the machining having the maximum machining time (tW)max is carried out by means of the two working units slidably supported on the same side of the portal structure.

In a further preferred embodiment, in the aforementioned step c) the maximum machining time (tW)max of each piece is divided between two work units slidably supported on opposite sides of the portal structure.

In this case, the machining having said maximum machining time (tW)max is carried out by means of the above two working units slidably supported on opposite sides of the portal structure.

By these preferred embodiments, ? is it advantageously possible to maximize the increase in productivity? of the work center compared to a work center of known type, restarting in the most? the maximum processing time (tW)max is appropriate according to the type of processing to be carried out.

This also taking into account any dead times necessary for moving the piece-holding table between the work areas involved in the event that the maximum machining time (tW)max of each piece is divided between two work groups slidingly supported on opposite sides of the portal structure.

In a particularly preferred embodiment, the machining having the maximum machining time (tW)max is carried out by two working units slidably supported on the same side of the portal structure on the central workpiece-holder table, or on the central workpiece-holder tables, of said N piece-holding tables of the machining centre.

In the context of the present description and in the subsequent claims, with the ?central piece-holding table? or ?tables for central pieces? it is intended to indicate the one or those of the side-by-side piece-holding tables arranged or arranged in a central position in the transversal direction of the work center or along the development of the crosspiece of the portal structure.

In this way, ? is it advantageously possible to maximize the increase in productivity? of the machining center compared to a known type of machining centre, minimizing the handling times of the workgroups supported on the same side of the portal structure and arranged side by side, to and from the workpiece table to which ? associated with the piece on which the machining must be performed having the maximum machining time (tW)max. In this preferred embodiment, moreover, ? advantageously possible to avoid that the table brings pieces to which ? associated the piece on which the machining must be performed having the maximum machining time (tW)max must be moved to a different work area positioned on the opposite side of the portal support structure achieving the maximum reduction of the dead times of the machining cycle .

In a preferred embodiment, the machining having the maximum machining time (tW)max is completely carried out by one of the aforementioned at least two working units slidably supported on the same side of the portal structure. even more preferably, the machining having the maximum machining time (tW)max is completely carried out by one of the aforementioned at least two working units slidably supported on the front side of the portal structure.

In this way, ? it is advantageously possible to minimize the movements of the piece-holder table which supports the piece on which machining is to be performed having the maximum machining time (tW)max, avoiding that it has to be moved in the work area arranged in the rear part of the machining center (accessible from working group supported on the rear side of the portal structure) thus reducing? maximum downtime in the processing cycle.

In a particularly preferred embodiment, in step d) the aforementioned at least two different processes are carried out on one of the pieces in a single work area by only one of said N structurally independent work groups. In this way, ? it is advantageously possible to avoid that the piece-holder table which supports the piece on which machining is to be carried out must be moved from the opposite side of the portal structure, thus reducing? maximum downtime in the processing cycle.

In the context of this preferred embodiment, it is even more it is preferable to carry out the aforesaid at least two different processes on one of the pieces in a single work area by means of one of the aforesaid at least two structurally independent work units slidably supported on the same side of the portal structure.

Pi? preferably, the aforesaid at least two different processes on one of the pieces are carried out in a single work area by means of one of the aforesaid at least two structurally independent work units slidably supported on the front side of the portal structure.

In this way, ? it is advantageously possible to minimize the movements not only of the piece-holder table that supports the piece on which machining must be performed, but also of the work groups, thus reducing? maximum downtime in the processing cycle.

Brief description of the figures

Further features and advantages of the present invention will be more clear from the following description of some of its preferred embodiments, made with reference to the attached drawings, given by way of non-limiting example. In such drawings:

- figure 1 ? a schematic perspective view of a work center according to a preferred embodiment from the front or workpiece loading/unloading side, in which the work volume protection barriers have been removed;

- figure 2 ? a schematic perspective view of the work center of figure 1 from the rear side of the work center;

- figure 3 ? a schematic side elevation view of the work center of figure 1;

- figure 4 ? a schematic plan view of the work center of figure 1;

- figures 5A-5I show as many basic diagrams of the arrangement of the workpiece tables and work units in successive phases of a working method implemented by means of a first preferred embodiment of the work center illustrated in figures 1-4;

- figures 6A-6G show as many basic diagrams of the arrangement of the piece-holding tables and of the working groups in successive phases of a working method implemented by means of a second preferred embodiment of the working center illustrated in figures 1-4.

Detailed description of the presently preferred embodiments of the invention With initial reference to figures 1-4, with the reference numeral 1 ? indicated as a whole a machining center for working materials, in particular, but not exclusively, wooden materials, according to a preferred embodiment of the invention.

In the preferred embodiment illustrated in the figures, the machining center 1 comprises a number N of workpiece-holding tables T1, T2 and T3 equal to three.

The workpiece tables T1, T2 and T3 are separate and independent from each other and are in particular slidably assembled, so that they per se? known, on an equal number N of first sliding guides indicated with references G1, G2 and G3 arranged parallel to each other.

The sliding guides G1, G2 and G3 extend along a first direction Y (indicated in figure 1 with reference to the central guide G2 and hereinafter also indicated as ?axis Y?) and each of the piece-holding tables T1, T2 and T3 ? movable along a respective one of said first guides G1, G2 and G3.

The development directions of each of the sliding guides G1, G2 and G3, i.e. the movement directions of the piece-holding tables T1, T2 and T3, are respectively indicated with the double arrows Y1, Y2 and Y3.

Preferably, each workpiece table T1, T2, T3 comprises a substantially plate-shaped central body 11 on which four pairs of vertical columns 12 for supporting a workpiece are mounted and each of which ? provided at one end? upper frees a respective locking member of the piece, for example of the sucker type.

In an alternative preferred embodiment, not shown, the workpiece clamping members can be of the mechanical type, such as for example the jaw type, as known in the prior art.

Preferably, the workpiece support columns 12 are mounted at opposite ends of the workpiece. of each piece-holding table T1, T2, T3 and can be positioned along respective sliding guides 13 so that they can be suitably arranged along the sliding guides 13 in a direction orthogonal to the aforementioned movement direction of the piece-holding tables Y1, Y2 and Y3. In this way, ? it is advantageously possible to support workpieces of various shapes and sizes by means of the workpiece-holding tables T1, T2, T3.

How more? exposed above, the pieces to be worked can have any shape, and develop mainly in one direction, such as for example the leg of a table, or develop mainly in two directions, such as for example the frame of a window, and have the most? various dimensions in the direction perpendicular to the horizontal plane of position on the piece-holder table as long as? compatible with the work to be carried out.

How more? described above, the pieces to be worked can be of any structural material suitable for being mechanically worked with working tools, such as for example wood, metal, plastic material or any composite material, such as for example agglomerates of fibers glued together or fiber of carbon.

The workpiece tables T1, T2 and T3 can be moved on the respective sliding guides G1, G2 and G3 and along the aforementioned movement directions Y1, Y2 and Y3 by means of movement devices per se? known and which will not be further described here for simplicity?.

In this preferred embodiment, the movement of the workpiece tables T1, T2 and T3 is numerically controlled type.

In the preferred embodiment illustrated in the figures, the work center 1 comprises a number N of work units W1, W2, W3, structurally independent, equal to the number of piece-holding tables T1, T2 and T3.

Preferably, each working group W1, W2, W3 ? slidably supported by a portal structure 14 along a respective sliding guide associated with the portal structure 14 and extended along a second transversal direction, in particular perpendicular, with respect to the first direction Y of sliding of the workpiece tables T1, T2, T3 on the respective sliding guides G1, G2 and G3.

This second direction? indicated in figure 1 with the reference X and hereinafter also indicated as ?axis X?.

In the preferred embodiment shown, the two working units W1 and W3 are slidably supported on the same front side of the portal structure 14, while the working unit W2 is supported slidingly. slidably supported on the rear opposite side of this structure 14.

The two working groups W1 and W3 will therefore also be referred to hereinafter as front or front working groups, while working group W2 will be hereinafter also referred to as the rear working group.

Preferably, the front working groups W1 and W3 are slidably supported by a same front guide 15, in turn comprising two parallel sliding tracks 16, and extended along a crosspiece 17 of the portal structure 14 in the X direction.

In accordance with a preferred embodiment, the working groups W1 and W3 each comprise a carriage 24, 25 slidably supported by the front guide 15 and provided with suitable devices for moving the working groups W1 and W3 along this guide and along the aforementioned second cross X direction.

In accordance with a preferred embodiment, the work groups W1 and W3 each comprise a slide 26, 27 associated with the mobile carriage 24, 25 and configured to allow translation of the work groups W1 and W3 along vertical movement directions indicated by Z1 and Z3.

In an analogous way and as better illustrated in figure 2, the rear working group W2 ? slidably supported by a rear guide 18, in turn comprising two sliding tracks 19, parallel to each other, and extended along the crosspiece 17 of the portal structure 14 in the X direction.

In particular, the work group W2 comprises a respective carriage 28 slidably supported by the rear guide 18 and provided with suitable devices for moving the work group W2 along this guide 18 and along the aforementioned second transversal direction X.

In accordance with a preferred embodiment, the working unit W2 comprises a respective slide 29 associated with the mobile carriage 28 and configured to allow a translation of the working unit W2 along a vertical movement direction indicated by Z2.

In this preferred embodiment, the handling of workgroups W1, W2 and W3 ? numerically controlled type.

In the preferred embodiment shown, the portal structure 14 is stationary. Pi? in particular, the portal structure 14 of the work center 1 comprises a base 20 resting on the ground and a pair of uprights 21, 22 extending vertically from the base 20 and configured to support the crosspiece 17 in a horizontal position.

In the portal structure 14 a through window 23 is therefore defined below the crosspiece 17 configured to accommodate the workpiece-holding tables T1, T2 and T3 and the respective sliding guides G1, G2 and G3.

Preferably, each work group W1, W2 and W3 comprises at least one work head or tool holder head respectively indicated with reference numbers 2, 3 and 4.

In accordance with one embodiment, each of the work heads 2, 3, 4 supports at least one tool holder spindle.

Pi? in particular, in the preferred embodiment illustrated in the figures, the working group W1 ? provided with a working head 2 able to support more? tool holder spindles, in this case four tool holder electrospindles 5, 6, 7 and 8, the latter being a so-called. ?bi-spindle? configured to be able to operate two machining tools. In the preferred embodiment illustrated in the figures, the working group W1 ? in particular provided at one of its extremities? lower part of a substantially fork-shaped support body 30 of the working head 2.

Preferably, the support body 30 is rotatably supported by the slide 26 associated with the mobile carriage 24 so as to be able to rotate about the vertical axis Z1 according to a rotation axis also referred to ?axis A? below.

Preferably, the W1 working group ? provided with a drive motor, not shown in detail, configured to rotate the support body 30 about the axis Z1. In this preferred embodiment, the working head 2 is pivoted to the support body 30 and ? movable by a respective drive motor 31 configured to rotate the working head 2 about an axis perpendicular to the vertical axis Z1 according to a rotation axis also referred to hereinafter as ?axis B?.

In this preferred embodiment, therefore, the working group W1 ? a multi-spindle machining group with two translation axes and two rotation axes.

In preferred embodiments, the working group W1 can be assigned complex and/or particularly onerous machining operations, in which case it ? which can be considered as the main working group of work center 1.

In the preferred embodiment illustrated in the figures, the working groups W2 and W3 are provided with respective working heads 3, 4 suitable for supporting a single tool holder spindle, in this case a tool holder electrospindle 9 and, respectively, a tool holder electrospindle tool 10.

In the preferred embodiment illustrated in the figures, both working groups W2, W3 are in particular provided at one end of them bottom of a respective support body 32, 33 of the working heads 3, 4.

Preferably, each support body 32, 33 comprises a suitably shaped arm 34, 35 and configured to rotatably support the respective work head 3, 4.

Preferably, each support body 32, 33 of the working heads 3, 4 is rotatably supported by the respective slide 29, 27 associated with each of the mobile carriages 28, 25 so as to be able to rotate about the vertical axes Z2, Z3 according to the axis of rotation A. Preferably, each working unit W2, W3 is? provided with a drive motor, not shown in detail, configured to rotate the support bodies 32, 33 about the axes Z2, Z3.

In this preferred embodiment, each of the working heads 3, 4? pivoted to the respective support body 32, 33 and ? movable by a respective drive motor 36, 37 configured to rotate each work head 3, 4 around an axis parallel to the horizontal X axis according to the aforementioned B axis.

In this preferred embodiment, therefore, the working groups W2 and W3 are single-spindle working groups with two translation axes and two rotation axes.

In accordance with a preferred embodiment, the tool holder spindles 5-10 of the work heads 2, 3 and 4 are configured to independently actuate respective tools, not shown for the sake of simplicity, which are therefore movable in a controlled manner with respect to the structure of each working group W1, W2 and W3.

In the preferred embodiment illustrated in the figures, the working heads 2, 3 and 4 can be moved according to 4 axes, two of which are translational along the X axes (together with the working unit W1, W2, W3 as a whole), Z1, Z2, Z3 (with respect to the corresponding working group W1, W2, W3), and two rotation axes A about the axes Z1, Z2, Z3 (together with the support bodies 30, 32, 33) and B about a perpendicular axis to the axes Z1, Z2, Z3 (with respect to the corresponding support body 30, 32, 33).

In this preferred embodiment and taking into account the movement of the workpiece tables T1, T2 and T3 along the horizontal translation axes Y1, Y2 and Y3 and in relation to the work groups W1, W2 and W3, therefore, the work heads 2 , 3 and 4 of the working groups W1, W2, W3 can therefore be moved with respect to the workpiece tables T1, T2 and T3 along three translation axes and two rotation axes.

In this preferred embodiment, the work center 1 is therefore of the type with five work axes.

In alternative preferred embodiments, not shown, the working heads 2, 3 and 4 can be moved along only the two translation axes X and Z so that, taking into account the movement of the workpiece tables T1, T2 and T3 along the horizontal translation axes Y1, Y2 and Y3, the work center 1 is in this case of the type with three work axes.

Work center 1 also includes:

- a number N x (N-1) of work zones, in this case six work zones, in which pu? at least one machining operation on at least one piece associated with each of the piece-holding tables T1, T2, T3 be carried out by at least one of the working groups W1, W2, W3; and

- a number N of piece loading/unloading zones, in this case three piece loading/unloading zones, one for each piece-holding table T1, T2, T3 and positioned, each, at one end? of each first guide G1, G2, G3.

Specifically, along each first guide G1, G2, G3 there are two work areas which are positioned, in the configuration of use of the work center 1, on opposite sides of the crosspiece 17 as better illustrated in figure 4.

For greater clarity, these six work areas are indicated in the figures with the letter L and a pair of successive numbers in which the first number corresponds to the number of the first guide G1, G2, G3 along which a piece-holder table T1 moves, T2, T3, while the second number, placed as a subscript, corresponds to the position, front or rear, with respect to crossbar 17.

Pi? in particular, the subscript 1 indicates the front or proximal position to the piece loading/unloading zones and the subscript 2 indicates the rear or distal position with respect to the piece loading/unloading zones.

In the following, these work areas will also be referred to as front work areas and, respectively, rear work areas.

Thus, for example, for the table T1 which moves along the first guide G1, the front work area will be? indicated with the reference L11, while the rear work area will be? indicated with the reference L12, with similar notations for the other work areas.

The work zones are in practice the spaces that can be occupied by the workpiece tables T1, T2, T3 and by the work groups W1, W2, W3 during the work cycle and do not correspond to a fixed position of the workpiece tables T1, T2, T3 or of the W1, W2, W3 working groups. For greater clarity, the three piece loading/unloading zones are indicated in the figures with the references S1, S2, S3.

The loading/unloading operations of the pieces can be carried out both manually and by means of automatic loading/unloading systems as known in the art.

Conveniently, there are also protective barriers surrounding the work center 1, not shown in the figures for the sake of simplicity.

Conveniently, the loading/unloading areas S1, S2, S3 are external to the protection barriers in order to be able to quickly carry out the loading and unloading operations of the pieces.

In the preferred embodiment shown in the figures, the work center 1 also comprises one or more parking zones of workgroups W1, W2, W3, positioned at one end? side of the crosspiece 17 of the portal structure 14 and externally to the area in which the sliding guides G1, G2, G3 are positioned.

Are the parking zone(s) of workgroups W1, W2, W3 preferably configured like this? to be able to accommodate, each, one of the working groups W1, W2, W3 when this group does not carry out any operation and, this, both at the beginning and during a working cycle.

In the preferred embodiment shown in the figures, the work center 1 comprises two parking zones, indicated with references P1 and P2 positioned, in the configuration of use of the work center 1, on opposite sides of the crosspiece 17 along the direction Y, as well as positioned laterally to the first sliding guide G1, cos? as best illustrated in figure 4.

Specifically, the parking zone P1 ? the one in a proximal position to the loading/unloading area of the pieces S1 and the parking area P2 ? the one in a distal position with respect to the loading/unloading area of the pieces S1.

In the preferred embodiment illustrated in the figures, therefore, the parking areas P1 and P2 are accessible from the work groups W2 and W3 positioned on opposite sides of the crosspiece 17.

In further preferred embodiments (not shown) and to satisfy specific needs, the parking zones of the workgroups W1, W2, W3 can be positioned on the opposite side with respect to the sliding guides G1, G2, G3 (that is, in the form embodiment illustrated in the figures, laterally to the third sliding guide G3 so as to be accessible to the working units W1 and W2), or positioned laterally to the sliding guides G1, G2, G3 on both sides of the latter.

In the latter case, for example, there could be four parking zones for work groups W1, W2, W3 positioned on opposite sides of the sliding guides G1, G2, G3 and of the crosspiece 17.

How much longer? described above, it follows that in the work center 1 a sort of ?matrix? of the work zones, of the loading and unloading zones of the pieces and of the parking zones, so? as for example graphically illustrated in figures 5A5I and 6A-6G with reference to possible preferred embodiments of the machining center 1 and of the method for carrying out mechanical machining according to the invention.

Specifically and with reference to figures 5A-5I and 6A-6G:

- the columns of the matrix indicate - starting from the left - the parking areas P1 and P2 which can be occupied by the work groups W3 and W2, the work areas which can be occupied by the workpiece tables T1, T2, T3 along the first guides G1, G2, G3, as well as? the loading/unloading areas of the pieces S1, S2, S3 provided at one end? of the first guides G1, G2, G3; And

- the rows of the matrix indicate - starting from the top - the parking areas P2 and P1 which can be occupied by work groups W2 and W3, the work areas which can be occupied by work groups W1, W2, W3 along the crosspiece 17 of the portal structure 14 and the loading/unloading zones of the pieces S1, S2, S3.

In accordance with the invention and how best will it appear? in the following, each working group W1, W2, W3 always operates on one table at a time and the operations to be carried out are appropriately divided among the working groups W1, W2, W3 in order to maximize productivity? of work center 1.

In the preferred embodiment illustrated in the figures, the machining center 1 further comprises accessory elements, such as for example a first tool-holder magazine, schematically indicated with the reference number 38, and a second tool-holder magazine, schematically indicated with the reference number 39 , of the or tools used by the working groups W3 and, respectively, W2 and which, as pi? shown above, are single-spindle machining units.

In the preferred embodiment shown in the figures, the tool magazines 38 and 39 are positioned close to the of the parking zones P1 and, respectively, P2, cos? to be easily accessible from the W3 and W2 single-spindle machining groups. The machining center 1 further comprises a unit? of control 40 suitably programmed to command the movement of the working groups W1, W2, W3 and of the workpiece tables T1, T2, T3 according to a machining program.

In particular, the unit? of control 40 preferably comprises a unit? of data processing that can? include one or more electronic processors, configured to execute the control programs of the machining center 1, in particular for commanding the machining groups W1, W2, W3, the workpiece tables T1, T2, T3 and all the accessories normally provided in a machining center work of this type.

In a way by itself? known, the unit? of control 40 preferably also comprises a user interface, provided for example with a keyboard 41 and a screen 42, by means of which interface ? it is possible to enter appropriate input data for the processes to be performed.

In accordance with a first preferred embodiment of the invention, the unit? of control 40 ? suitably programmed to command the movement of the work groups W1, W2, W3 and of the workpiece tables T1, T2, T3 according to a machining program including the phases of:

a) select at least two different processes to be carried out on each piece associated with each piece-holder table T1, T2, T3, each process having a processing time tW;

b) selecting a maximum processing time (tW)max among the processing times tW of said at least two different processes;

c) dividing the maximum machining time (tW)max of each piece between two working groups of said working groups W1, W2, W3;

d) perform on each piece associated with each piece holder table T1, T2, T3 the aforementioned at least two different processes,

wherein the machining having the maximum machining time (tW)max is carried out by means of the two working groups, of said working groups W1, W2, W3, between which the maximum machining time (tW)max is divided.

In a preferred embodiment, illustrated below? in detail below, phase a) provides for the selection of at least three different processes to be carried out on each piece associated with each piece-holder table T1, T2, T3.

In a preferred embodiment, the machining having the maximum machining time (tW)max can? be carried out by the working groups W1, W3 slidingly supported on the front side of the portal structure 14.

In an alternative preferred embodiment, the machining having the maximum machining time (tW)max can? be carried out partly by one of the two working groups W1 and W3 slidably supported on the front side of the portal structure 14, and partly by the working group W2 slidably supported on the rear side of the portal structure 14.

Preferably and as pi? described above, the maximum machining time (tW)max of each piece is divided among, for example, workgroups W1, W3, or between one of the workgroups W1 or W3 and workgroup W2, so that one of the two operational working groups, carry out a fraction between 20% and l?80%, pi? preferably between 40% and 60% of the maximum processing time (tW)max.

In this preferred embodiment, therefore, the working group W3 is configured as a so-called working group. ?auxiliary? structurally simple and low-cost but, at the same time, configured to absorb a substantial part of the maximum machining time (tW)max of each piece to be machined and to also carry out further machining with a significant increase in productivity? of work center 1.

The Applicant has found that the most advantages? described above in terms of increased productivity? of the machining center 1 are particularly evident in the case in which the maximum machining time (tW)max of each piece to be machined in the work zones ? between 1.2 and 2 times the minimum machining time (tW)min of said piece.

In a particularly advantageous preferred embodiment, the machining having the maximum machining time (tW)max is carried out by the two work units W1, W3 slidably supported on the front side of the portal structure 14 on the central workpiece table T2 slidably guided along the central guide G2.

In this way and how more? above? is it possible to maximize the increase in productivity? of the machining center 1 compared to a known type of machining centre, minimizing the handling times of the work units W1, W3 arranged side by side along the portal support structure 14 to and from the piece holder table T2 to which ? associated with the piece on which the machining must be performed having the maximum machining time (tW)max.

In this preferred embodiment, moreover, ? advantageously possible to avoid that the table carries pieces T2 to which ? associated the piece on which the machining must be performed having the maximum machining time (tW)max must be moved to a different work area positioned on the opposite side of the portal support structure 14 achieving the maximum reduction of dead times of the machining cycle processing.

With reference to the work center 1 according to this preferred embodiment, will now described with reference to figures 5A-5I a preferred embodiment of a method for carrying out mechanical workings on pieces, for example of wooden material, according to the invention, feasible by means of the aforementioned work center 1.

In these figures and for greater clarity, the workpiece tables that support a piece to be machined or in progress are illustrated by an empty square, while the workpiece tables in the loading/unloading phase by a full square.

Furthermore and for greater clarity, the references relating to the work areas, the loading/unloading areas and the parking areas of the work groups have been indicated only in figure 5A.

Purely by way of non-limiting example, the operations to be carried out on the pieces supported by the piece holder tables T1, T2, T3 can be the following: contouring, drilling, and sanding.

The contouring, drilling and slot milling operations are carried out using the W1 working group (multi-spindle, without tool change) and the W3 working group (single-spindle, with tool change).

The sanding process? carried out using the W2 working group (single spindle, without tool change).

With reference to figure 5A and referring to a moment of the work cycle which does not correspond to the start-up of the work center 1, in a first phase the table T3, previously moved from the loading/unloading area S3 to the work area L31 is located in this area and is interacting with the work group W1 to allow the piece loaded on it to undergo a first machining in this area.

For example, this processing can be a contouring process.

At this stage, the W2 working group ? in the respective parking zone P2, the table T1 supporting a piece awaiting machining ? in area L11, while table T2 is in work area L21 and is interacting with work group W3 which is performing the machining with the maximum machining time (tW)max on the piece supported in this area by table T2.

For example, this machining having the maximum machining time (tW)max can? be a contouring process.

In a subsequent phase, illustrated in figure 5B, the working group W3 is moved in the zone L11 so? to start a further machining on the piece supported in this area by the table T1, previously waiting.

For example, this further machining to be performed on the piece supported in the L11 area can be a contouring process.

Simultaneously, the working group W1 continues with the machining on the piece supported by the table T3 in the working area L31, for example by finishing the contouring machining and carrying out a subsequent drilling machining.

In this phase, the working group W2 continues to remain in the respective parking zone P2.

In a subsequent phase, illustrated in figure 5C, the working group W3 continues with the machining (contouring) on the piece supported by the table T1 in the area L11 while the working group W1 is moved in the area L21 so? to finish on the piece supported in this area by table T2 the machining (in this example, contouring) having the maximum machining time (tW)max.

In a preferred embodiment, the maximum processing time (tW)max is divided in zone L21 between the two work groups as follows: 40% of the maximum processing time (tW)max allocated to work group W3 and 60% of the maximum processing time (tW)max allocated to work group W1.

In this phase, the W1 working group also carries out on the piece supported in the area L21 by table T2 also a drilling operation.

In this phase, both table T3 and work group W2 are moved to area L32 as follows: to continue on the piece supported in this area by table T3 the machining to be carried out on this piece.

For example, the machining to be performed on the piece supported in the L32 area can? be a smoothing operation.

In a subsequent phase, illustrated in figure 5D, the working group W3 is moved into the respective parking area P1, the working group W1 is moved into the area L11 so? to carry out a drilling operation on the piece supported in this area by the table T1, while both the table T2 and the working group W2 are moved in the area L22 cos? to continue on the piece supported in this area by table T2 the operations, for example sanding, to be carried out on this piece.

In this phase, the table T3 is moved in the respective loading/unloading zone S3 in such a way as to be able to unload the previously machined piece from the work units W1 and W2 and load a new piece to be machined.

In a subsequent phase, illustrated in figure 5E, both table T3 - on which ? been loaded a new piece to work - both the working group W1 are moved in the area L31 cos? to start new machining operations, for example contouring and drilling, on the piece supported in this area by table T3, while work group W2 continues the machining operations, for example sanding, on the piece supported in this area by table T2 in area L22.

In this phase, table T1 remains waiting in zone L11, while work group W3 continues to remain in the respective parking zone P1.

In a subsequent phase, illustrated in figure 5F, both the table T1 - previously awaiting machining - and the working group W2 are moved in the area L12 so? to finish the machining operations, for example sanding, on the piece supported in this area by table T1, while the work group W1 continues in area L31 the machining operations on the piece supported in this area by table T3 (for example, contouring and drilling).

In this phase, the working group W3 continues to remain in the respective parking area P1, while the table T2 is moved to the respective loading/unloading area S2 in such a way as to be able to unload the previously machined piece from the working groups W1, W2 and W3 and load a new work piece.

In a subsequent phase, illustrated in Figure 5G, both table T2 - on which ? been loaded a new piece to work - is the working group W3 are moved in the area L21 cos? to start machining, for example contouring, with the maximum machining time (tW)max on the piece supported in that area by table T2, while workgroups W1 and W2 continue the machining in areas L31 and L12 (for example, W1: trimming/drilling; W2: smoothing) on the pieces supported in these areas by tables T3 and, respectively, T1.

No working group at this stage ? in parking lot and no work table ? awaiting processing.

In a subsequent phase, illustrated in figure 5H, the table T1 is moved in the respective loading/unloading area S1 in such a way as to be able to unload the previously machined piece from the W1, W2 and W3 work groups and load a new piece to be machined , while the working group W2 is moved to the respective parking area P2. In this phase, the workgroups W1 and W3 continue in areas L31 and L21 the machining of the pieces supported in this area by tables T3 and, respectively, T2 (for example, W1: contour cutting/drilling; W3: contour cutting).

With this phase the working cycle ends as with it all the workings envisaged on at least three pieces are completed.

In a subsequent phase, illustrated in figure 5I, in fact, the work center 1 returns to the configuration illustrated in figure 5A, that is to say, with the work group W3 positioned and operative in area L21 to continue with the machining having the time of maximum machining (tW)max on the piece supported in this area by the table T2 and the work group W1 positioned and operating in the work area L31 so? to continue machining on the piece supported by table T3 in that area.

In this phase, the working group W2 remains in the respective parking zone P2. In this way, can what? start again a cycle of work on three pieces by repeating the sequence of operations pi? described above.

In order to verify the entity? of the increase in productivity? of the work center 1 and of the working method according to the most preferred embodiment? described above, and in accordance with the work center and the work method object of claims 1 and 15, with respect to a work center of the known type according to EP 3269499, some simulations of three standard processes of contouring, drilling and polishing were carried out on seats of wooden chairs by means of respective tools mounted on the working groups.

Pi? in particular, these simulations were carried out with a work center 1 according to the invention provided with three work groups and three piece-holding tables, as more? described above, in which the working groups were so? configured:

- working unit W1 comprising a machining head equipped with 5 spindles configured to operate the following tools: twin-spindle milling/drilling bit, 3 spindles with respective milling cutters;

- working unit W2 comprising a working head equipped with 1 spindle configured to operate the following tools: smoothing tool;

- working unit W3 comprising a machining head equipped with 1 spindle configured to operate the following tools: contouring cutter.

Were the same type of machining simulated with a machining center according to EP 3 269 499, i.e. with a machining center like this? configured:

- a first working group W1 on one side of the support portal structure 14 comprising a working head equipped with 2 spindles each equipped with a drill bit and a milling cutter; And

- a second working unit W2 on the opposite side of the support portal structure 14 comprising a working head equipped with a smoothing tool.

The unit of control 40 ? been programmed to operate according to the sequence of operations for a machining center having three workpiece tables and two workgroups so? positioned described by EP 3269 499.

From this simulation, which the Applicant believes predicts the actual operation of the work center with excellent approximation, ? a reduction of the cycle time, i.e. of the total machining and loading/unloading time of the pieces (including any tool change times) equal to approximately 30%, was detected.

Does such a reduction appear highly significant and predictive of a substantial increase in productivity? of the machining center according to this preferred embodiment of the invention with respect to a machining center configured and operated according to the teachings of EP 3269 499.

In accordance with a second preferred embodiment of the invention, the unit? of control 40 ? suitably programmed to command the movement of the work groups W1, W2, W3 and of the workpiece tables T1, T2, T3 according to a machining program including the phases of:

a) select at least two different processes to be carried out on each piece associated with each piece-holder table T1, T2, T3, each process having a processing time tW;

b) selecting a maximum processing time (tW)max among the processing times tW of said at least two different processes;

d) perform on each piece associated with each piece holder table T1, T2, T3 the aforementioned at least two different processes,

wherein the machining having said maximum machining time (tW)max is completely carried out by only one of the structurally independent work groups W1, W2, W3.

In a preferred embodiment, the machining having the maximum machining time (tW)max is completely carried out by the working unit W3 slidably supported on the front side of the portal structure 14.

In an alternative preferred embodiment, the machining having the maximum machining time (tW)max can? be completely carried out by one of the remaining work groups W1 or W2 slidingly supported by opposing parts of the portal structure 14.

Preferably, in step d) the aforementioned at least two different processes are carried out on one of the pieces in a single work area, for example the work area L11, by only one of the work groups W1, W2, W3, for example the W3 working group. Also in this preferred embodiment, the working group W3 is configured as a so-called working group. ?auxiliary? structurally simple and low cost but, at the same time, configured to absorb all the maximum machining time (tW)max of each piece to be machined or even the overall time of the machining to be performed on a given piece with a significant increase in productivity? of the working center 1. The Applicant has found that also in this preferred embodiment the main advantages? described above in terms of increased productivity? of the machining center 1 are particularly evident in the case in which the maximum machining time (tW)max of each piece to be machined in the work zones ? between 1.2 and 2 times the minimum machining time (tW)min of said piece.

With reference to the work center 1 according to this further preferred embodiment, it will be now described with reference to figures 6A-6G a preferred embodiment of a method for carrying out mechanical workings on pieces, for example of wooden material, according to the invention, which can be implemented by means of the aforementioned work center 1.

Similarly to how much more? shown above with reference to figures 5A-5I, also in figures 6A-6G and for greater clarity, the workpiece tables that support a piece to be machined or in progress are illustrated by means of an empty square, while the workpiece tables in phase loading/unloading using a full square.

Furthermore and for greater clarity, the references relating to the work areas, the loading/unloading areas and the parking areas of the work groups have been indicated only in figure 6A.

Purely by way of non-limiting example, the operations to be carried out on the pieces supported by the piece-holding tables T1, T2, T3 are, as in the case of the previous preferred embodiment, the following: contouring, drilling, slot milling and smoothing.

The contouring, drilling and slot milling operations are also carried out in this case using the W1 working group (multi-spindle, without tool change) and the W3 working group (single-spindle, with tool change).

The sanding process? carried out using the W2 working group (single spindle, without tool change).

With reference to figure 6A and referring to a moment of the work cycle which does not correspond to the start-up of the work center 1, in a first phase the table T3 is located in the loading/unloading area S3 to carry out the operations envisaged therein unloading of a previously machined piece and loading of a new piece to be machined, while the work unit W1 and the table T2 are in the work area L21 to carry out suitable machining of the piece loaded on the table T2.

For example, these processes can be contouring and drilling operations. At this stage, the W3 working group ? in the respective parking area P1, while the work unit W2 and the table T1 are in the work area L12 to perform machining of the piece loaded on table T1.

For example, this processing can be a smoothing operation.

In a subsequent phase, illustrated in figure 6B, the table T2 remains in the area L21 waiting for the piece to be machined by the work group W2, while both the table T3 - on which it is been loaded a new piece to work - both the working group W1 are moved in the area L31 cos? to start new machining on the piece supported in this area by table T3.

For example, these processes can be contouring and drilling processes. In this phase, the working group W2 continues in the area L12 the polishing operations on the piece supported in this area by the table T1, while the working group W3 remains in the parking area P1.

In a subsequent phase, illustrated in figure 6C, both table T2 - previously awaiting processing in area L21 - and work group W2 are moved to area L22 so to carry out polishing operations on the piece supported in this area by table T2, while the work group W1 continues in area L31 the contouring and drilling operations on the piece supported in this area by table T3.

In this phase, the working group W3 continues to remain in the respective parking area P1, while the table T1 is moved to the respective loading/unloading area S1 in such a way as to be able to unload the previously machined piece from the working groups W1 and W2 and load a new work piece.

In a subsequent step, illustrated in figure 6D, both the table T1 - on which ? been loaded a new piece to work - is the working group W3 are moved in the area L11 cos? to start new machining operations, for example contouring and drilling, on the piece supported in this area by table T1, while work groups W1 and W2 continue in areas L31 and L22 the machining on pieces supported in this area by tables T3 and, respectively , T2 (for example, W1: contour cutting and drilling; W2: smoothing).

In particular, in this phase the working group W3 starts in the zone L11 and on the piece supported by the table T1 the contouring machining having the maximum machining time (tW)max.

No working group at this stage? in parking lot and no work table ? awaiting processing.

In a subsequent phase, illustrated in figure 6E, the table T2 is moved in the respective loading/unloading zone S2 in such a way as to be able to unload the previously machined piece from the W1 and W2 work units and load a new piece to be machined, while both the table T3 and the working unit W2 are moved in the working area L31 in such a way as to carry out the polishing operations on the piece supported by the table T3 in this area.

In this phase, the working group W3 continues the machining, for example of contouring, having the maximum machining time (tW)max in the L11 area on the piece supported by the table T1, while the working group W1 remains waiting for a piece to work in zone L31.

In a subsequent phase, illustrated in figure 6F, both the table T2 - on which ? been loaded a new piece to work - both the working group W1 are moved in the area L21 cos? to start new machining, for example contouring and drilling, on the piece supported in this area by table T2, while work groups W2 and W3 continue in areas L31 and L11 the machining on pieces supported in this area by tables T3 and T1 ( for example, W2: smoothing; W3: drilling).

In particular, in this phase the working group W3 ends in the area L11 and on the piece supported by the table T1 all the machining envisaged for this piece.

At this stage, no working group ? in parking lot and no work table ? awaiting processing.

With this phase the working cycle ends as with it all the workings foreseen on three pieces are completed.

In a subsequent phase, illustrated in figure 6G, in fact, the work center 1 returns to the configuration illustrated in figure 6A, i.e. with the table T3 in the loading/unloading area S3, with the work unit W1 and the table T2 in work area L21 to allow machining of the piece loaded on table T2, with work group W2 and table T1 in work area L12 to allow machining of the piece loaded on table T1 and with work group W3, who has completed the work to be carried out in the previous phase, in the respective parking area P1.

In this way, can what? start again a cycle of work on three pieces by repeating the sequence of operations pi? described above.

In order to verify the entity? of the increase in productivity? of the working center 1 and of the working method according to the further preferred embodiment last described above? above, and in accordance with the work center and the work method object of claims 2 and 16, with respect to a work center of the known type according to EP 3269 499, some simulations were carried out of four standard processes of contouring, drilling, milling of quarrying and sanding on wooden chair seats using respective tools mounted on the work groups.

Pi? in particular, these simulations were carried out with a work center 1 according to the invention equipped with three work groups and three workpiece tables, in which the work groups were configured as in the previous simulation which concerned the previous embodiment .

Were the same type of machining simulated with a machining center according to EP 3 269 499 as pi? described above and in which the unit? of control 40 ? been programmed to operate according to the sequence of operations for a machining center having three workpiece tables and two machining groups described by EP 3269 499.

From this simulation, which also in this case the Applicant considers to predict the effective functioning of the work center with excellent approximation, ? a reduction of the cycle time, i.e. of the total machining and loading/unloading time of the pieces (including any tool change times) equal to approximately 25%, was detected.

This reduction also appears highly significant and predictive of a substantial increase in productivity? of the work center according to this aspect of the invention with respect to a work center configured and operated according to the teachings of EP 3269 499.

Obviously, in the work center described above, a technician of the branch, in order to satisfy specific and contingent needs, will be able to make numerous modifications and variations, all however contained within the scope of protection of the present invention as defined by the following claims.

Claims (23)

1. Machining center (1) including: - a number N of piece-holding tables (T1; T2; T3), where N ? three or four, - a number N of first guides (G1; G2; G3) for sliding of said piece-holding tables (T1; T2; T3) extending along a first direction (Y); each piece-holding table (T1; T2; T3) being movable along a respective one of said first guides (G1; G2; G3); - a number N of structurally independent workgroups (W1; W2; W3) equal to the number of piece-holding tables (T1; T2; T3), each workgroup (W1; W2; W3) comprising at least one workhead ( 2; 3; 4) and being slidably supported by a portal structure (14) along respective sliding guides (15; 18) associated with said portal structure (14) and extending along a second direction (X) transversal to said first direction (Y); at least two working groups (W1; W3) being slidably supported on the same side of said portal structure (14); - a number N x (N-1) of work zones in which pu? be carried out by at least one of said work groups (W1; W2; W3) at least one machining operation on at least one piece associated with each of said piece holder tables (T1; T2; T3); along each first guide (G1; G2; G3) there being N-1 work zones; - a N number of loading/unloading areas (S1, S2, S3) of the pieces, one for each piece holder table (T1; T2; T3) and positioned, each, at one end? of each first guide (G1; G2; G3); - a?unit? controller (40) programmed to command the movement of the working groups (W1; W2; W3) and/or the piece-holding tables (T1; T2; T3) according to a machining program comprising the phases of: a) select at least two different processes to be carried out on each piece associated with each piece-holder table (T1; T2; T3), each process having a processing time tW; b) selecting a maximum processing time (tW)max among the processing times tW of said at least two different processes; c) dividing the maximum processing time (tW)max of each piece between two work groups of said N work groups (W1; W2; W3) structurally independent; d) carry out on each piece associated with each piece holder table (T1; T2; T3) at least two different processes, wherein the machining having said maximum machining time (tW)max is carried out by the two work groups, of said N work groups (W1; W2; W3) structurally independent, between which the maximum machining time ( tW)max. 2. Machining center (1) including: - a number N of piece-holding tables (T1; T2; T3), where N ? three or four, - a number N of first guides (G1; G2; G3) for sliding of said piece-holding tables (T1; T2; T3) extending along a first direction (Y); each piece-holding table (T1; T2; T3) being movable along a respective one of said first guides (G1; G2; G3); - a number N of structurally independent workgroups (W1; W2; W3) equal to the number of piece-holding tables (T1; T2; T3), each workgroup (W1; W2; W3) comprising at least one workhead ( 2; 3; 4) and being slidably supported by a portal structure (14) along respective sliding guides (15; 18) associated with said portal structure (14) and extending along a second direction (X) transversal to said first direction (Y); at least two working groups (W1; W3) being slidably supported on the same side of said portal structure (14); - a number N x (N-1) of work zones in which pu? be carried out by at least one of said work groups (W1; W2; W3) at least one machining operation on at least one piece associated with each of said piece holder tables (T1; T2; T3); along each first guide (G1; G2; G3) there being N-1 work zones; - a N number of loading/unloading areas (S1, S2, S3) of the pieces, one for each piece holder table (T1; T2; T3) and positioned, each, at one end? of each first guide (G1; G2; G3); - a?unit? controller (40) programmed to command the movement of the working groups (W1; W2; W3) and/or the piece-holding tables (T1; T2; T3) according to a machining program comprising the phases of: a) select at least two different processes to be carried out on each piece associated with each piece-holder table (T1; T2; T3), each process having a processing time tW; b) selecting a maximum processing time (tW)max among the processing times tW of said at least two different processes; d) carry out on each piece associated with each piece holder table (T1; T2; T3) at least two different processes, wherein the machining having said maximum machining time (tW)max is completely carried out by only one of said N structurally independent work groups (W1; W2; W3). 3. Work center (1) according to any one of the preceding claims, wherein said work groups (W1; W2; W3) are multi-spindle or single-spindle work groups. 4. Work center (1) according to claims 2 and 3, wherein one of said at least two work groups (W1; W3) slidably supported on the same side of said portal structure (14)? a single-spindle machining group. 5. Work center (1) according to any one of the preceding claims, wherein it dictates at least one work head (2; 3; 4) of at least one of said work groups (W1; W2; W3)? movable with respect to said piece-holding tables (T1; T2; T3) along a plurality? of translation and/or rotation axes, preferably along three translation axes and two rotation axes. 6. Work center (1) according to any one of the preceding claims, comprising a tool holder magazine (38) positioned laterally to one of said first guides (G1; G2, G3) for sliding the workpiece tables (T1; T2; T3) at one end? side of said portal structure (14). 7. Work center (1) according to claims 4 and 6, wherein said tool holder magazine (38) is located near of said single-spindle working group (W3). 8. Machining center (1) according to any one of the preceding claims, wherein the maximum machining time (tW)max of the piece to be machined is? between 1.2 and 2 times the minimum machining time (tW)min of said piece. 9. Machining center (1) according to claims 1 or 3-8, wherein the maximum machining time (tW)max of each piece is divided between said two work groups (W1; W3) of said N work groups (W1; W2; W3) structurally independent so that one of said two working groups (W1; W3) carries out a fraction between 20% and 80% of said maximum working time (tW)max. 10. Machining center (1) according to any one of claims 1 or 3-9, wherein in said phase c) the maximum machining time (tW)max of each piece is divided between two work groups (W1; W3) slidably supported on the same side of said portal structure (14) or between two working groups (W1; W2; W3) slidably supported on opposite sides of said portal structure (14), and in which the machining having said maximum processing (tW)max is carried out by means of said two working units slidably supported on the same side or on opposite sides of said portal structure (14). 11. Work center (1) according to any one of claims 1 or 3-10, wherein the machining having said maximum machining time (tW)max is carried out by two work groups (W1; W3) slidably supported on the same side of said portal structure (14) on the central piece-holder table (T2) or on the central piece-holder tables of said N piece-holder tables (T1; T2; T3) of the machining center (1). 12. Work center (1) according to any one of claims 2-8, wherein the machining having said maximum machining time (tW)max is carried out by one of said at least two work groups (W1; W3) slidably supported on the same side, more preferably on a front side, of said portal structure (14). 13. Machining center (1) according to any one of claims 2-8 or 12, wherein in said phase d) said at least two different processes are carried out on one of the pieces in a single work area by means of only one of said N of structurally independent working groups (W1; W2; W3). 14. Work center (1) according to claim 13, in which said at least two different processes are carried out on one of the pieces in a single work area by means of one of said at least two structurally independent work groups (W1; W3). slidingly supported on the same side, pi? preferably on a front side, of said portal structure (14). 15. Method for carrying out mechanical machining using a machining center (1) comprising: - a number N of piece-holding tables (T1; T2; T3), where N ? three or four, - a number N of first guides (G1; G2; G3) for sliding of said piece-holding tables (T1; T2; T3) extending along a first direction (Y); each piece-holding table (T1; T2; T3) being movable along a respective one of said first guides (G1; G2; G3); - a number N of structurally independent workgroups (W1; W2; W3) equal to the number of piece-holding tables (T1; T2; T3), each workgroup (W1; W2; W3) comprising at least one workhead ( 2; 3; 4) and being slidably supported by a portal structure (14) along respective sliding guides (15; 18) associated with said portal structure (14) and extending along a second direction (X) transversal to said first direction (Y); at least two working groups (W1; W3) being slidably supported on the same side of said portal structure (14); - a number N x (N-1) of work zones in which pu? be carried out by at least one of said work groups (W1; W2; W3) at least one machining operation on at least one piece associated with each of said piece holder tables (T1; T2; T3); along each first guide (G1; G2; G3) there being N-1 work zones; - a N number of loading/unloading areas (S1, S2, S3) of the pieces, one for each piece holder table (T1; T2; T3) and positioned, each, at one end? of each first guide (G1; G2; G3); - a?unit? control (40) programmed to control the movement of the work groups (W1; W2; W3) and/or the piece-holding tables (T1; T2; T3); where the method includes the steps of: a) select at least two different processes to be carried out on each piece associated with each piece-holder table (T1; T2; T3), each process having a processing time tW; b) selecting a maximum processing time (tW)max among the processing times tW of said at least two different processes; c) dividing the maximum processing time (tW)max of each piece between two work groups of said N work groups (W1; W2; W3) structurally independent; d) carry out on each piece associated with each piece holder table (T1; T2; T3) at least two different processes, wherein the machining having said maximum machining time (tW)max is carried out by the two work groups, of said N work groups (W1; W2; W3) structurally independent, between which the maximum machining time ( tW)max. 16. Method for carrying out mechanical machining using a machining center (1) comprising: - a number N of piece-holding tables (T1; T2; T3), where N ? three or four, - a number N of first guides (G1; G2; G3) for sliding of said piece-holding tables (T1; T2; T3) extending along a first direction (Y); each piece-holding table (T1; T2; T3) being movable along a respective one of said first guides (G1; G2; G3); - a number N of structurally independent working groups (W1; W2; W3) equal to the number of workpiece tables (T1; T2; T3), supported by a portal structure (14) along respective sliding guides (15; 18 ) associated with said portal structure (14) and extending along a second direction (X) transversal to said first direction (Y); at least two working groups (W1; W3) being slidably supported on the same side of said portal structure (14); - a number N x (N-1) of work zones in which pu? be carried out by at least one of said work groups (W1; W2; W3) at least one machining operation on at least one piece associated with each of said piece holder tables (T1; T2; T3); along each first guide (G1; G2; G3) there being N-1 work zones; - a N number of loading/unloading areas (S1, S2, S3) of the pieces, one for each piece holder table (T1; T2; T3) and positioned, each, at one end? of each first guide (G1; G2; G3); - a?unit? control (40) programmed to control the movement of the work groups (W1; W2; W3) and/or the piece-holding tables (T1; T2; T3); where the method includes the steps of: a) select at least two different processes to be carried out on each piece associated with each piece-holder table (T1; T2; T3), each process having a processing time tW; b) selecting a maximum processing time (tW)max among the processing times tW of said at least two different processes; d) carry out on each piece associated with each piece holder table (T1; T2; T3) at least two different processes, wherein the machining having said maximum machining time (tW)max is carried out by only one of said N of structurally independent work groups (W1; W2; W3). 17. A method according to any one of claims 15 or 16, wherein the maximum machining time (tW)max of the workpiece is between 1.2 and 2 times the minimum machining time (tW)min of said piece. 18. Method according to any one of claims 15 or 17, wherein the maximum processing time (tW)max of each piece is divided between said two work groups (W1; W2; W3) of said N work groups (W1; W2; W3) structurally independent so that one of said two working groups (W1; W2; W3) carries out a fraction between 20% and 80% of said maximum working time (tW)max. 19. Method according to any one of claims 15, 17 or 18, wherein in said phase c) the maximum processing time (tW)max of each piece is divided between two work groups (W1; W3) slidingly supported on the same side of said portal structure (14) or between two working groups (W1; W2; W3) slidably supported on opposite sides of said portal structure (14) and in which in said phase d) the machining having said machining time maximum (tW)max is carried out by means of said two working groups slidably supported on the same side or on opposite sides of said portal structure (14). 20. Method according to any one of claims 15 or 17-19, wherein the machining having said maximum machining time (tW)max is carried out by two work groups (W1; W3) slidably supported on the same side of said structure at portal (14) on the central piece-holder table (T2) or on the central piece-holder tables of said N piece-holder tables (T1; T2; T3) of the machining center (1). 21. Method according to any one of claims 16 or 17, wherein the machining having said maximum machining time (tW)max is carried out by one of said at least two working groups (W1; W3) slidably supported on the same side, pi ? preferably on a front side, of said portal structure (14). 22. Method according to any one of claims 16, 17 or 21, wherein in said step d) said at least two different processes are carried out on one of the pieces in a single work area by only one of said N of work groups (W1; W2; W3) structurally independent. 23. Method according to claim 22, wherein said at least two different processes are carried out on one of the pieces in a single working area by means of one of said at least two structurally independent working groups (W1; W3) slidably supported on the same side, more preferably on a front side, of said portal structure (14).