Tool post comprising a plurality of tool-holder spindles and numerically-controlled machine tool including such tool post

Abstract

To shorten the time for the tool acceleration and deceleration phases.SOLUTION: A tool post (10) including a body (11) extending according to an axis A-A, the latter including, at one of its ends, a base (12) for fastening to a numerically-controlled machine tool and, at the other end, a head (13) movable in rotation, the head (13) including at least two tool-holder spindles (14, 14', 14"), each being intended to receive a cutting tool (15, 15', 15") in engagement, the spindles occupying, depending on the angular position of the head (13), a working position in which they are intended to carry out a machining operation on a workpiece held in position in a fitting position, or a standby position in which they are withdrawn from the workpiece, each of the spindles being configured to be controlled independently of the other in order to immobilize or drive in rotation the cutting tool carried thereby, irrespective of the position it occupies.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The invention relates to the field of numerically controlled machine tools for machining parts, preferably micromechanical parts, and to the field of equipment for such machines.

[0002] More particularly, the present invention relates to a tool post including a spindle for multiple tool holders, and to a numerically controlled machine having such a tool post. [Background technology]

[0003] Numerically controlled machine tools are intended, inter alia, for the production of mass-produced parts by performing machining operations according to the instructions of a computer program. Such machines typically have tools mounted in a spindle of a tool holder and include a tool changer for changing the tools held in the spindle of the tool holder, the tool changer adapted to the machining operation to be performed on a part held in place on a mounting member.

[0004] When changing tools, the machine tool is unproductive in the sense that the machining operation is interrupted. Therefore, the objective is to minimize the tool change time. To this end, tool changers have been developed to do as much work as possible in the mask time, thereby minimizing the machine downtime and increasing productivity.

[0005] For example, multi-spindle tool rests are known which have a head in which several tool holder spindles are arranged, one of which is active and the others are stationary. In particular, the active tool holder spindle is engaged with the drive mechanism by a coupling system. Therefore, between two machining operations, the tool can be changed by disengaging the active tool holder spindle, i.e. the spindle holding the tool that needs to be changed, rotating the head so that the next tool holder spindle is present, and coupling this tool holder spindle to the drive mechanism.

[0006] However, this solution is not entirely satisfactory in that, although the tool change time is reduced, it is not completely masked. In fact, in this type of multi-spindle tool post, between tool changes, the tool to be changed must be decelerated before the tool change and the next tool must be accelerated to the processing rotation speed when it is coupled to the drive mechanism. Such a multi-spindle tool post also requires a certain amount of time to remove the tool to be changed, rotate the head, index the next tool, align it with the coupling system, and then couple it. Moreover, this solution is particularly complex and expensive due to the coupling system.

[0007] There are multi-spindle tool posts that address the problem of tool holder spindle acceleration and deceleration, but in these tool posts, all tools are driven to rotate simultaneously. Therefore, when a tool is changed, the next tool is already driven at the machining speed and can start machining the part. However, such multi-spindle tool posts require a lot of energy to rotate all the tools at the same time. In addition, the maximum rotation speed of the gripped tools is relatively limited by the kinematic chain of motion transmission.

[0008] Taken together, whether the tools held by the prior art are rotated individually or simultaneously, the bulkiness of prior art multi-spindle tool rests creates a high moment of inertia and increases the risk of collision between the mounting member and the tools held by the tool rest.

[0009] In addition to the aforementioned drawbacks, these solutions are not suitable for machining micromechanical parts. Summary of the Invention [Problem to be solved by the invention]

[0010] The present invention solves the aforementioned drawbacks by providing a solution that allows to completely mask the tool change times, in particular by masking the acceleration and deceleration phases of the tool. Another object achieved by the invention is to maximize the compactness of the machine tool and to reduce the moving mass. [Means for solving the problem]

[0011] To that end, the invention relates to a tool rest having a body extending along an axis AA, at one end of which is a base for fixing to a numerically controlled machine tool and at the other end of which is a rotatably movable head, the head having at least two tool holder spindles, each intended to engage and receive a cutting tool, which, depending on the angular position of the head, occupy either a working position intended to perform a machining operation on a workpiece held in a fixed position on a mounting member, or a standby position remote from the workpiece, each of said spindles being arranged to be controlled independently of the other spindles, regardless of the position it occupies, in order to stop or to rotate the cutting tool gripped therein.

[0012] Since the spindle is independently servo controlled, it is possible to accelerate and decelerate the spindle in a masked time. Thus, the present invention allows a tool change to be performed with only the wait time for the next tool to contact the workpiece reduced to the head rotation time. Due to the features of the present invention, the tool change time between tips is estimated to be in the range of a few tenths of a second.

[0013] The present invention also has the advantage that it can be adapted to any existing machine tool.

[0014] The present invention also allows the spindle to reach relatively high rotational speeds, for example 60,000 to 80,000 revolutions per minute.

[0015] In particular embodiments, the invention may further include one or more of the following features, considered individually or in any technically feasible combination:

[0016] In a particular embodiment, the axis of rotation of the head coincides with the axis AA.

[0017] In certain embodiments, the base is configured such that axis AA forms an angle of between 35 and 55 degrees with respect to the vertical axis.

[0018] These features relate to maximizing compactness of the device.

[0019] In a particular embodiment, the principal axes are preferably evenly distributed around the axis of rotation of the head and are arranged such that the axes BB, B-B' and BB" form angles of 35 to 55 degrees with the axis AA and such that the axes BB, B-B' and BB" do not intersect.

[0020] On the one hand, this feature makes it easier to remove the tool when it is at rest in order to avoid or limit the risk of collision with the mounting parts, and on the other hand, it makes it possible for all spindles to maintain the same working position, thereby ensuring that machining tolerances can be met.

[0021] In certain embodiments, the principal axes are disposed relative to one another such that projection of the longitudinal axes BB, B-B' and BB" onto a plane P perpendicular to the axis AA forms a regular polygon of degree n centered on the axis AA, where n is the number of principal axes.

[0022] In certain embodiments, the main shafts are disposed such that the longitudinal axes BB, BB' and BB'' are spaced from the axis AA by a distance greater than the radius of the main shafts.

[0023] This feature also relates to removing the tool when it is at rest to avoid or limit the risk of collision with the attachment.

[0024] In certain embodiments, each of the spindles is equipped with its own motor to rotate or stop the cutting tool held therein.

[0025] This feature makes it possible to reduce energy consumption of the tool post, since the spindles that are not performing machining operations stop rotating about their corresponding longitudinal axes.

[0026] In certain embodiments, at least one spindle is adapted to occupy at least two different working positions, each working position being determined by a predetermined angular position of the tool post head.

[0027] In certain embodiments, the at least one spindle is adapted to continuously occupy the working position as the tool rest head rotates, an arrangement that also includes continuous movement of the mounting member.

[0028] According to another object, the invention relates to a numerically controlled machine tool, preferably for machining micromechanical parts, comprising at least one tool post as described above, fixed by its base directly to a frame or to a carriage translatable in a vertical plane, whereby the axis AA forms an angle of 35 to 55 degrees with respect to the vertical axis, said machine tool further comprising a mounting member intended to hold the part to be machined in a fixed position.

[0029] In a particular embodiment, the machine tool has two tool posts disposed on either side of the mounting member.

[0030] In a particular embodiment, the machine tool has a protective wall against flying swarf and cutting fluid, the or each tool post body being fluid-tightly engaged in a corresponding opening in said protective wall.

[0031] A further aspect of the invention is a method for changing a tool in a machine tool as described above, comprising the steps of: a first cutting tool engaged with the spindle in a working position for performing a first machining step and a second cutting tool engaged with the spindle in a waiting position for performing a second machining step and is prevented from rotating; - before the end of the first machining phase, the second cutting tool rotates about the B-B' axis until it reaches a rotational speed characteristic of the second machining phase; - upon completion of the first machining stage, the head rotates about axis AA to drive the spindle holding the second cutting tool to a working position so that the second cutting tool can begin the second machining stage, and to drive the spindle holding the first cutting tool to a standby position, the first cutting tool being prevented from rotating once the spindle holding the first cutting tool has reached its standby position.

[0032] Other characteristics and advantages of the invention will become apparent from the following detailed description, given by way of non-limiting example only, and with reference to the accompanying drawings, in which: [Brief description of the drawings]

[0033] [Figure 1] FIG. 1 is a perspective view of a multi-spindle tool rest according to a preferred embodiment of the present invention. [Diagram 2] FIG. 2 is a view of the tool rest of FIG. 1 oriented along the longitudinal axis of the body of the tool rest. [Diagram 3] FIG. 2 is a side view of the tool rest of FIG. [Figure 4] FIG. 2 is a perspective view of two tool rests disposed on either side of a workpiece mounting member. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0034] Please note that the drawings are not drawn to scale for clarity.

[0035] FIG. 1 shows a tool rest 10 intended for machining components, preferably micromechanical components. The tool rest 10 has a body 11 extending along a longitudinal axis, which in the embodiment of the invention is designated "axis AA", at one end of which it has a base 12 for fixing to a numerically controlled machine tool 20 and at the other end a head 13 rotatably movable about an axis coinciding with the axis AA. The head 13 has at least two toolholder spindles 14, 14' or 14", each intended to engage and receive a cutting tool 15, 15' or 15". Depending on the angular position of the head 13, each spindle 14, 14' and 14" occupies either a working position intended to perform a machining operation on a workpiece held in a fixed position on a mounting member 21 or a standby position remote from the workpiece.

[0036] It should be noted that the tool rest 10 can be translationally driven, for example, if the base 12 is fixed to a carriage (not shown) of a machine tool 20 that is movable along at least one translational degree of freedom relative to the XYZ trihedron, and preferably three degrees of translational freedom.

[0037] Alternatively, for example, if the base 12 is fixed directly to the frame 22 of the machine tool 20, the tool rest 10 can be stopped.

[0038] Advantageously, spindles 14, 14' and 14" are arranged to be controlled independently of one another to rotate or stop a cutting tool 15, 15' or 15" held therein. This feature is particularly advantageous when changing tools. Preferably, spindles 14, 14' and 14" are motorized spindles, also known as "electronic spindles", each having its own motor to rotate or stop a cutting tool 15, 15' or 15" held therein.

[0039] In particular, in order to exchange a first cutting tool 15 for carrying out a first machining step with a second cutting tool 15' intended for carrying out a second machining step, the second cutting tool is rotated before the end of the first machining step until it reaches a rotational speed specific for the second machining step.

[0040] A first cutting tool 15 is engaged with the spindle 14 in a working position, and a second cutting tool 15' is engaged with the spindle 14' in a standby position.

[0041] When the first machining stage is completed, the head 13 moves the spindle 14, which was in the working position, to the standby position and rotates the spindle 14', which was in the standby position, to the working position. The second cutting tool 15' has reached the machining rotation speed when the engaged spindle 14' was in the standby position, so the subsequent second machining stage starts immediately. At this time, the spindle 14 gripping the first cutting tool 15 is in the standby position and the first cutting tool is stopped.

[0042] Thus, when the second cutting tool 15' rotates and the first cutting tool 15 is stopped at mask time, the cutting tools are changed with reduced waiting time only while the head is rotating.

[0043] Each spindle 14, 14' and 14" extends along a longitudinal axis, denoted "BB axis", "B-B' axis" and "BB" axis", respectively, which also forms an axis of rotation, and which is shown in Figs. 1 and 3 only for the spindle 14 in the working position. As shown in these figures, in the working position the spindle 14 is oriented such that the axis BB is parallel to a vertical axis. However, in another working position the spindle 14 can also be oriented such that the axis BB is parallel to a horizontal axis. The spindle 14 may also occupy a dynamic working position, i.e. the head 13 may rotate during a machining operation. In this case the mounting 21 may be mobile and move according to instructions in the machining program and / or the tool rest 10 may be mobile via the base 12 and move according to instructions in the machining program.

[0044] In a preferred embodiment of the present invention, as shown, the tool post 10 has three main axes 14, 14' and 14". FIG. 2 specifically shows that the main axes 14, 14' and 14" are distributed in the head 13 of the tool post 10, and the main axes 14, 14' and 14" are evenly distributed around the rotation axis of the head 13, i.e., around the axis AA in this embodiment of the present invention. The main axes 14, 14' and 14" are arranged relative to one another such that when the axes BB, B-B' and BB" are projected onto a plane P perpendicular to the axis AA, they form an n-th degree regular polygon centered on the axis AA, where n is the number of main axes. In the example shown in FIG. 2, the longitudinal axes of the main axes 14, 14' and 14" form an equilateral triangle.

[0045] Furthermore, in a preferred embodiment of the invention, the spindles 14, 14' and 14" are arranged such that the axes BB, B-B' and BB" are spaced from the axis AA by a distance greater than the radius of the spindle 14, 14' or 14", for example at least a distance equivalent to the diameter of the spindle 14, 14' or 14". This arrangement allows maximizing the clearance of the cutting tool 15' or 15" from the spindles 14' and 14" in the parked position, thereby avoiding the risk of collision between the cutting tool 15' and 15" and the mounting member 21 or the workpiece. It should be noted that, in general, the more spindles a head has, the greater the distance that the axis AA will be spaced from the spindle axes BB, B-B' and BB".

[0046] 3, tool post 10 is configured such that axis AA forms an angle of 35-55 degrees, preferably 45 degrees, with respect to the vertical axis due to the shape of base 12. Spindles 14, 14' and 14" are therefore disposed in head 13 such that axes BB, B-B' and BB" are inclined at an angle of 35-55 degrees, preferably 45 degrees, with respect to axis AA, whereby in the working position the spindles are parallel to the vertical axis as previously described.

[0047] Taken together, as can be derived from the above and from the drawings, the main shafts 14, 14' and 14" are arranged symmetrically with respect to one another along the axis AA, and the axes BB, B-B' and BB" of the main shafts 14, 14' and 14" do not intersect one another.

[0048] Furthermore, a particular arrangement of the spindles 14, 14' and 14" relative to the head 13 of the tool rest 10 makes it possible to reduce force loops. In fact, the spindles 14, 14' and 14" are fixed as close as possible to connecting elements formed, for example, by ball bearings, allowing the head 13 to rotate relative to the body 11 of the tool rest 10.

[0049] Furthermore, the machine tool 20 may have two tool rests 10 arranged on either side of the mounting member 21, as shown in Figure 4. As shown in this figure, the presence of two tool rests 10 allows two machining operations to be performed simultaneously on the same workpiece. Advantageously, the rotation axes of the spindles 14 of each tool rest 10 in the working position may be coincident.

[0050] The mounting member 21 may be in the form of a table designed to hold a workpiece in a fixed position, with varying degrees of translational and rotational mobility.

[0051] As shown in Fig. 4, the machine tool 20 may have a protective wall 23 for protection against splashes of chips and cutting fluid. In particular, the protective wall 23 is arranged liquid-tight around the body 11 of the or each tool post 10 and has an opening into which said body 1 engages for this purpose. This opening may include a wiper seal at its periphery arranged against said body 11. Furthermore, the protective wall 23 may advantageously include a bellows. The wiper sole and the bellows allow the tool post to remain liquid-tight during its movement in the XYZ triangle.

[0052] The protective wall 23 has its peripheral portion fixed to the frame 22 of the machine tool 20 .

[0053] Moreover, each protective wall 23 advantageously extends in a plane perpendicular to the axis AA, i.e. inclined with respect to the horizontal axis, thereby enabling the flow of cutting fluid and chips to be boosted. This arrangement also facilitates operator access to the mounting member 21 and the spindle 14, 14' or 14".

[0054] It should also be noted generally that the implementations and manufacturing methods discussed above have been described as non-limiting examples, and therefore other variations are conceivable. [Explanation of symbols]

[0055] 10 Tool rest 11 Main unit 12 base 13 Head 14, 14', 14” spindle 15, 15', 15” cutting tools 20 Numerical control machine tools 21 Mounting material 22 Frames 23 Protective Wall AA axis BB, B-B', BB” Longitudinal axis P plane

Claims

1. 1. A tool rest (10) having a body (11) extending along an axis A-A, at one end of said body a base (12) for fixing to a numerically controlled machine tool (20) and at the other end a rotatable head (13), said head (13) having at least two tool holder spindles (14, 4', 14"), each spindle intended to engage and receive a cutting tool (15, 15', 15"), said tool rest (10) being configured such that said spindles (14, 14', 14") are The tool rest (10) is configured such that, depending on the angular position of the head (13), it occupies either a working position intended for performing a machining operation on a workpiece held in a fixed position on a mounting member (21) or a standby position spaced from the workpiece, and each of the spindles (14, 14', 14") is controlled independently of the other spindles in order to stop or rotate the cutting tool (15, 15', 15") held therein, regardless of the position it occupies.

2. The tool rest (10) of claim 1, wherein the axis of rotation of the head (13) coincides with the axis A-A.

3. The tool rest (10) of claim 2, wherein the base (12) is configured such that the axis AA forms an angle of between 35 and 55 degrees with respect to a vertical axis.

4. 2. The tool rest (10) according to claim 1, wherein the main shafts (14, 14', 14") are distributed around a rotation axis of the head (13), and each main shaft (14, 14', 14") is arranged such that axes B-B, B-B' and B-B" form angles of 35 to 55 degrees with respect to the axis A-A, and such that axes B-B, B-B' and B-B" do not intersect each other.

5. The tool rest (10) according to claim 4, wherein the main axes (14, 14', 14") are disposed relative to one another such that, when the axes B-B, B-B' and B-B" are projected onto a plane P perpendicular to the axis A-A, they form an n-th degree regular polygon centered on the axis A-A, where n is the number of the main axes (14, 14', 14")

6. 2. The tool rest (10) of claim 1, wherein the spindle (14, 14', 14") is disposed such that the axes B-B, B-B' and B-B" are spaced from the axis A-A by a distance greater than a radius of the spindle (14, 14', 14").

7. 2. The tool post (10) of claim 1, wherein each of the spindles (14, 14', 14") has its own motor for rotating or stopping the cutting tool (15, 15', 15") held therein.

8. 2. The tool rest (10) of claim 1, wherein at least one spindle (14, 14', 14") is adapted to occupy at least two different working positions, each working position being determined by a predetermined angular position of the head (13) of the tool rest (10).

9. 2. The tool rest (10) of claim 1, wherein at least one spindle (14, 14', 14") is adapted to continuously occupy a working position during rotation of the head (13) of the tool rest (10).

10. A numerically controlled machine tool (20), preferably for machining micromechanical workpieces, comprising at least one tool rest (10) according to claim 1, fixed by said base (12) to a frame (22) or directly to a carriage translatable along an XYZ trihedron, whereby said axis A-A forms an angle of 35 to 55 degrees with respect to a vertical axis, said numerically controlled machine tool further comprising a mounting member (21) intended to hold in a fixed position a workpiece to be machined.

11. The machine tool (20) according to claim 10, further comprising two tool rests (10) disposed on either side of the mounting member (21).

12. 11. The machine tool (20) according to claim 10, comprising a protective wall (23) against splashes of chips and cutting fluid, the body (11) of the or each tool post (10) being fluid-tightly engaged in a corresponding opening in the protective wall (23).

13. A method for changing a tool of a machine tool (20) according to claim 10, comprising the steps of: a first cutting tool (15), engaged with the spindle (14) in a working position, is intended to perform a first machining step, and a second cutting tool (15'), engaged with the spindle (14') in a waiting position, is intended to perform a second machining step and is prevented from rotating; - before the end of the first machining phase, the second cutting tool (15') rotates about the axis B-B' until it reaches a rotational speed characteristic of the second machining phase; when the first machining stage is completed, the head rotates about the axis A-A to drive the spindle (14') holding the second cutting tool (15') to a working position so that the second cutting tool begins the second machining stage, and to drive the spindle (14) holding the first cutting tool (15) to a standby position, the first cutting tool being prevented from rotating when the spindle (14) holding the first cutting tool reaches the standby position.

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