Computer-controlled machine tool for the production of small workpieces

Abstract

A computer-controlled machine tool (1) for the production of small workpieces, particularly in the dental field, preferably from ceramic materials, metals, plastics, or waxes, is described. The machine tool is designed with a tool spindle (2) for holding various tools (3), with a tool motor (4) for driving the tool spindle (2), and with a workpiece holding device (5) for receiving and holding a workpiece (6) to be machined, wherein the workpiece holding device (5) can be positioned relative to the rotating tool (3) in or about three to five or more machining axes, with a frame element on which the tool motor (4) and the workpiece holding device (5) are mounted by means of linear guides, characterized in that the frame element is designed as a plane-parallel base plate (8) and two linear guides are arranged on the base plate (8) at an intersecting angle.wherein a tool spindle axis (2A) of the tool motor (4) is arranged at a wider angle to the other linear axes of the linear guides such that, by coordinated movements of the three linear axes, all points in space, at least within the intended workpiece (6), can be reached with the tool clamped in the tool spindle (2).

Description

State of the art

[0001] The invention relates to a computer-controlled machine tool for the production of small workpieces, particularly in dental technology, jewelry manufacturing and microsystems technology, preferably made of ceramic materials, metals, plastics or waxes.

[0002] CNC machine tools and machining centers with up to 5 axes have been around for some time and are used worldwide in a wide variety of configurations. A defining characteristic of this type of machine is that it is generally equipped with three linear axes and two swivel axes. All axes can be implemented "within the tool" (the workpiece remains stationary), all axes can be "within the workpiece" (the tool rotates only around its own axis, and all spatial movements are performed by the workpiece), or any combination of these axis arrangements is possible.

[0003] All common designs share the characteristic that the machine is built on a relatively complex, usually cast, frame element, which in turn requires multi-sided, precise machining to give the machine the desired and necessary precision. This frame element accounts for a significant portion of the mechanical assembly costs. An example of a machining center for the production of small workpieces in the dental field is described in DE 10 2010 035 669 A1.

[0004] WO 2009 / 100863 A2 describes a clamping device for a computer-controlled, machining machine for the production of dental workpieces with a slidably mounted holding device on which a carrier plate for receiving a mold blank is mounted, wherein the carrier plate has at least one through-opening in which the mold blank is arranged at least about an axis of rotation substantially parallel to the main plane of the carrier plate.

[0005] The object of the present invention is to provide a machine tool that is as simple and cost-effective as possible and is designed for machining small and very small workpieces. Disclosure of the invention

[0006] According to the invention, the problem is solved by the subject matter of claim 1. Advantageous further developments result from the dependent claims.

[0007] The invention relates to the creation of a computer-controlled machine tool for the production of workpieces, comprising a tool spindle for holding various rotating tools, a tool motor for driving the tool spindle, and a workpiece holding device for receiving and holding a workpiece to be machined. The workpiece holding device is positionable relative to the rotating tool in or around three to five or more machining axes. The machine includes a frame element designed as a plane-parallel base plate in the XY direction, on which the tool motor and the workpiece holding device are mounted by means of first, second, and third linear guides. The tool spindle is movable in the Z direction by means of the first linear guide perpendicular to the XY plane of the base plate, and the second and third linear guides are arranged on the base plate at an intersecting angle.This ensures that, through coordinated movements of the slides on the three linear guides, all points in space, at least within the intended workpiece, are reachable with the tool clamped in the tool spindle. This has the advantage of minimizing the force transmission paths that occur between the workpiece and the tool during machining. The machine tool thus exhibits very high inherent rigidity with minimal construction effort. Consequently, the machine tool can be designed to be resource-efficient and as lightweight as possible.

[0008] To achieve high rigidity of the frame element while minimizing force transmission paths, a window is incorporated into the frame element, within which the tool spindle axis can move in an XZ plane. The frame element therefore features a rectangular window opening. This allows the tool spindle axis to be moved through the window opening, controlled by positioning drives, for three-dimensional machining of the workpiece and to be traversed in a Z-axis.

[0009] In order to design the force flow paths as optimally and shortly as possible and thus to create a lightweight construction with high stiffness, at least one linear guide of a support, in particular a spindle support, of the workpiece holding device is arranged on a first front surface of the frame element designed as a base plate, and at least one linear guide of the support of the tool spindle is arranged on a second rear surface of the base plate, which is mirror-symmetrical to the first.

[0010] Such a machine tool can be used primarily in dental technology, but also in jewelry manufacturing and microsystems technology, and can be specifically optimized for a particular workpiece type. In dental technology, workpieces for dental prostheses such as crowns, bridges, posts, implants, etc., can be machined from pre-sintered or organically bonded ceramic blanks on all sides without reclamping. Furthermore, such machine tools can also process plastics for temporary restorations or metals for metal prostheses, and waxes, for example, for the production of gold fillings, crowns, and gold teeth using the lost-wax casting process. Likewise, the machines can, of course, also be designed and used for processing minerals, glass, and natural materials (such as wood, horn, bone, etc.)—in short, for virtually all machinable materials.Due to the small workpiece size, such machine tools can be built so small, light and handy that they can be used as a tabletop device on a normal household socket (110 - 240 VAC, I.) without any special technical or infrastructural requirements. nenn ≤ 16 A) can be operated.

[0011] To enable access to all spatial points within a preferably cuboid-shaped machining area, two or three linear axes are arranged perpendicular to each other and thus parallel to the respective spatial axes of a Cartesian coordinate system (XYZ), according to a further embodiment of the invention. This also makes the machine tool simple and cost-effective to manufacture, while minimizing and simplifying the calculation of force flow paths.

[0012] It is understood that the three linear axes of the linear guides and any additional one or two degrees of freedom of the machine tool could also be configured as axes not arranged perpendicular to each other if this offers advantages for the spatial arrangement of the machine, the design requirements, or chip removal. In this case, the machine control system handles the conversion of the axis coordinate system into a preferably Cartesian coordinate system, for example, according to DIN 66025 / ISO 6983.

[0013] To enable multi-sided machining of complex workpieces without reclamping, the workpiece holding device, viewed in its initial position, can preferably include a first pivot axis in any arbitrary axis position, which is not designed to rotate parallel to the Z-axis. Since the tool spindle axis is preferably fixed in the Z-axis, the workpiece holding device can assume any other pivot axis different from the Z-axis to achieve multi-sided machining of the workpiece.

[0014] It is further preferred that the first axis of rotation, which moves the workpiece, is arranged parallel to the XY spatial plane when viewed in the starting position. This allows the workpiece to be rotated and machined equally well from both the front and back sides.

[0015] To improve the machinability of the workpiece, it is further preferred that the workpiece holding device be pivotable about another arbitrary spatial axis, i.e., a second one, which is not parallel to the first pivot axis (40A) and is not pivoted by the first pivot axis. This creates a fifth degree of freedom with respect to the workpiece and the tool.

[0016] According to a further preferred embodiment, at least one spatial axis, in particular the Y-axis, is designed to move the workpiece holding device by means of two parallel linear guides mounted as far apart as possible. Thus, the workpiece holding device of the machine tool is designed to be movable in a Y-axis parallel to the XY plane of the frame element.

[0017] To secure and define the structure of the frame element, at least one spatial axis, in particular the X-axis, is designed to move the tool spindle using two parallel linear guides mounted as far apart as possible. Thus, the tool spindle is movable along an X-axis parallel to the XY plane of the frame element.

[0018] To ensure optimal distribution of strength, stiffness, and forces, at least one spatial axis, particularly the X-axis, is preferably designed with two parallel linear guides for the tool spindle. This allows the force paths to be guided via two linear guides, with the parallel distance between the two linear guides being at least the defined width of the window opening.

[0019] According to a further preferred embodiment, in order to distribute the forces on two linear guides, at least one spatial axis, in particular the Y-spatial axis, is preferably designed for moving the workpiece holding device with two parallel linear guides, in particular arranged at least at a defined movable distance of the X-spatial axis.

[0020] The linear guides of the workpiece holding device and a support for the tool spindle can be arranged on a common surface of the base plate of the frame element. They can also be arranged at right angles to each other, i.e., on the end face and the side face.

[0021] To improve the machining of the workpiece, in particular for machining from all sides, i.e. also the back of the workpiece, the workpiece holding device is preferably designed to be rotatable on a workpiece carrier about the X-axis when viewed in the initial position.

[0022] For improved machining, the workpiece holding device is preferably designed to be pivotable around the Y-axis parallel to the linear guide in the Y-space axis. This allows the workpiece to be machined with an additional degree of freedom.

[0023] To move the tools with high precision and thus produce a high-precision workpiece, the machine tool comprises electrically controlled drives, preferably positioning drives, servo drives, or stepper drives, for moving the tool spindle and workpiece holding device along the machining axes. These positioning drives are controlled by a computer via a control device and are preferably interpolable across multiple axes so that the tool can describe any spatial curve relative to the workpiece with a programmable path speed.The computer uses a processing program in accordance with or based on DIN 66025 / ISO 6983, which is transferred to the machine control in whole or in part before the respective processing step and is translated by the machine control in the specified sequence into the movement commands for the individual positioning drives and the speed specifications for the tool drive.

[0024] According to a further embodiment of the invention, the frame element is designed with feet for setting up the frame element in a vertical direction, wherein the X-axis in particular encompasses the vertical. Particularly advantageous chip removal and correspondingly low contamination of the spindle and the linear guides result from an arrangement in which the base plate is parallel to a horizontal plane and the Z-axis (the tool spindle) is accordingly arranged vertically (suspended). Likewise, depending on the design specifications, available space, and the requirements for chip removal and any cooling lubricants used, arrangements are also possible in which the base plate is arranged at any spatial angle to the horizontal.

[0025] To improve the capture and removal of chips and auxiliary media such as cooling lubricants, to seal the machining area to the outside, and for reasons of machine safety, the machine tool is designed with an enclosure, in particular a trough-like geometry, whereby in particular an extraction system using negative pressure and a bottom opening is provided.

[0026] To create a fully automatic machine tool, the machine tool is preferably equipped with a tool magazine, wherein the tools can be automatically removed from and placed in the tool magazine by means of a controllable collet chuck via the tool spindle, which is movable in all three spatial directions relative to the tool magazine. The tool magazine is arranged so that it can be reached by the tool spindle, thus allowing automatic tool changes without additional components. One possible arrangement of the tool magazine is shown below. Fig. 1, Fig. 3 and Fig. 4 is visible.

[0027] Preferably, the tool magazine is designed with an elastic element, in particular an elastomer element with bores that are slightly smaller than the corresponding shanks of the tools, whereby the tools stored in the tool magazine are held securely in these bores against vibration, but can also be removed or inserted by the collet chuck without the actuation of actuators in the tool magazine.

[0028] According to the invention, an expensive, complex-to-machine frame element, for example in the form of a casting, is thus dispensed with, with a plane-parallel base plate assuming the load-bearing function. The base plate is arranged perpendicular to the tool spindle axis in order to minimize the force transmission paths and increase the inherent stiffness, whereby the screwed-on linear guides of the machine tool can contribute significantly or partially to the stiffness of the plane-parallel base plate. Brief description of the drawings

[0029] The invention is explained in more detail below with reference to an exemplary embodiment and the drawings. The drawings show: Fig. 1 a schematic top view from below of the machine tool according to the invention; Fig. 2 a front view of the machine tool according to the invention; Fig. 3 a top view of the machine tool according to the invention; Fig. 4 a side view from the left of the machine tool according to the invention and Fig. 5 a side view from the right of the machine tool according to the invention. Embodiments of the invention

[0030] The Fig. Figure 1 shows an abstract representation in a top view from below of a computer-controlled machine tool 1 according to the invention for the production of workpieces, in particular for the production of dental prostheses such as crowns, bridges, post teeth, implants, and other small workpieces, for example in jewelry manufacturing or microsystems technology.

[0031] The machine tool 1 is therefore particularly well-suited for the production of workpieces from ceramic materials, metals, plastics, waxes, and also natural materials such as glass, minerals, and natural materials (especially wood, horn, bone, etc.). The machine tool 1 comprises a tool spindle 2 with a collet 9 for holding various tools 3 from a tool magazine 48, a tool motor 4 for driving the tool spindle 2, and a workpiece holding device 5 for receiving and holding a workpiece 6 to be machined. In its starting position, the tool spindle 2 is aligned with its tool spindle axis 2A perpendicular to the workpiece holding device 5. The machine tool 1 is designed with five machining axes.The tool motor 4 with the tool spindle 2 can be moved precisely on a spindle carrier 15 by means of a first linear guide 12 in a horizontal Z-space axis parallel to the alignment of the tool spindle axis 2A by means of a positioning drive 10 and a threaded spindle 13.

[0032] As in the Fig. 2 in a front view and in Fig. Figure 3, shown in a top view, depicts the tool motor 4 mounted on a spindle carrier 15 with the first linear guide 12 on the opposite side of a workpiece. A slide 14, which runs in and supports the first linear guide 12, is attached to a support 25.

[0033] The machine tool 1 comprises a frame element designed as a plane-parallel base plate 8. The plane-parallel base plate 8 is shown in the selected representation as in the Fig. 2, Fig. 4 and Fig. Figure 5 shows the tool motor 4 mounted vertically with an orientation along the vertical X-axis. In this X-axis, the tool motor 4 is movable via two parallel rails 22, 26 of a second linear guide 21 with carriages 24, 28 mounted thereon, as shown in the figure. Fig. Figure 5 is shown as a side view from the right. The respective height of the spindle carrier 15 is adjustable by means of a threaded spindle 23, which is controlled by a positioning drive 20. On a first front surface 82 of the base plate 8, the workpiece holding device 5 is displaceably arranged on a carrier with a swivel arm 44 in a Y-axis by means of a third linear guide 31. The workpiece holding device 5 is mounted on a slide 34, which runs on a rail 32 of the third linear guide 31. The exact position on the Y-axis is set by means of a positioning drive 30 and a threaded spindle 33. The two linear guides 21 with rails 22, 26 are arranged on a second rear surface 84 of the base plate 8, which is mirror-symmetrical with respect to the X-axis, as shown in the Fig. 5 is presented more clearly.

[0034] Thus, on the plane-parallel base plate 8, the second and third linear guides 21 and 31 are arranged at a 90° intersecting angle, positioned on two different, opposing surfaces: the front surface 82 and the rear surface 84. The tool spindle axis 2A, on the other hand, is parallel to the Z-axis and perpendicular to the XY plane in which the base plate 8 is oriented. This configuration minimizes the force transmission paths that occur during machining of the workpiece 6. Furthermore, the linear guides 21 and 31 provide additional rigidity to the frame element along the X-axis and along the Y-axis, respectively.

[0035] The workpiece 6, with workpiece holding direction 5, can be moved with three degrees of freedom on the front surface 82 of the base plate 8. A swivel arm holder 42 with a swivel arm 44 is mounted on the slide 34 of the linear guide 31. As shown in the Fig. As shown in Figure 2, a positioning drive 40 with a threaded spindle 43 is mounted on the swivel arm holder 42 to swivel the workpiece 6 together with the workpiece holding device 5 about the Y-axis at bearings 45 and 46 in the swivel axis 40A. In its initial position, the swivel arm 44 extends in the direction of the X-axis, as shown in Figure 2. Fig.The positioning drive 50, shown in Figure 2, rotates the workpiece holding device 5 together with the workpiece 6 about the X-axis in the swivel axis 50A. This allows the workpiece 6 to be machined from different sides, in particular from the front surface 82 and the rear surface 84, using the tool 3. The swivel movement in the bearings 45 and 46 is performed by rotating a threaded spindle 43. The workpiece holding device 5 is mounted directly on the positioning drive 50. Depending on the design, the positioning drive 50, as well as the other positioning drives 10, 20, 30, and 40, include an intermediate reduction gear.

[0036] According to the invention, the force transmission path between tool 3 and workpiece 6 is small in this machine tool and extremely short on the frame element 8. The force transmission path from tool 3 thus runs via the tool spindle axis 2A and the tool motor 4 to the spindle 13, from the spindle 13 to the carrier 25, which is mounted on slides 24 and 28 of the linear guide 21, where the forces are transmitted to the rails 22 and 26. The forces are transmitted to the rear surface 84 of the base plate 8 and, via its thickness and stiffness, to the front surface 84 of the base plate 8. From there, the forces travel via the linear guide 31 to the swivel arm holder 42, where they are again distributed to the spindle 43 and the bearings 45 and 46. These forces are then transmitted to the swivel arm 44, which transfers them to the workpiece holding device 5 and the workpiece 6.

[0037] In order for the base plate 8 to have high rigidity and for the tool spindle 2 to be movable in the spatial axes X and Z, the base plate 8 has a rectangular window 86 through which the tool spindle 2 with the tool 3 is moved and the rectangular window 86 is designed to be elongated at least in the X-spatial axis such that the maximum travel distance in the X-spatial axis can be traversed by the tool spindle 2.

[0038] For this purpose, the tool motor 4 is mounted on the spindle carrier 15 with the linear guide rail 11, which can be moved directly to the workpiece 6 through the window 86 by rotating the spindle 13 in the Z-space axis in order to machine the workpiece 6.

[0039] The tools 3 from the tool magazine 48 can be automatically removed and replaced by means of the electrically (or electropneumatically) actuated collet 9. This allows for automated tool changes to be performed programmatically by the machine control system. Thus, automatic, computer-controlled machining of the workpiece 6 is possible. The tool magazine 48 has an elastic element with bores in which the tools 3 can be stored. The tool magazine 48 is mounted laterally on the swivel arm 44 of the workpiece holder 5, with bores 49 parallel to the tool spindle axis 2A.

[0040] The base plate 8 is mounted vertically along the spatial axis X with a base having a geometric shape in the form of a trough 60. The base 60 is inclined towards an opening (not shown) in the trough 60 to allow for the removal of chips and any optionally used cooling lubricants. This removal is facilitated by a vacuum created in a discharge channel of the opening. The machine tool 1 is located within an enclosure (not shown) that serves to seal the machining area from the outside and to ensure machine safety in accordance with Directive 2006 / 42 / EC (or corresponding non-European regulations and directives). The enclosure does not have a load-bearing function.

[0041] All figures are merely schematic representations, not to scale. Furthermore, particular reference is made to the graphic representations as essential to the invention.

Claims

[1] Computer-controlled machine tool (1) for the production of small workpieces (6), particularly in the dental field, preferably made of ceramic materials, metals, plastics or waxes, comprising a tool spindle (2) for holding various tools (3), a tool motor (4) for driving the tool spindle (2) and a workpiece holding device (5) for receiving and holding a workpiece (6) to be machined, wherein the workpiece holding device (5) can be positioned relative to the rotating tool (3) in or about three to five or more machining axes to each other, comprising a frame element designed in the XY direction as a plane-parallel base plate (8) on which the tool motor (4) and the workpiece holding device (5) are mounted by means of first, second and third linear guides,wherein the tool spindle (2) is movable in the Z direction by means of a tool spindle axis (2A) perpendicular to the XY plane of the base plate (8) by means of the first linear guide (12) and second and third linear guides (21, 31) are arranged on the base plate (8) at an intersecting angle, such that all points in space, at least within the intended workpiece (6), are reachable by coordinated movements of slides on the three linear guides (12, 21, 31) with the tool clamped in the tool spindle (2), wherein a window (86) is formed in the frame element within which the tool spindle axis (2A) is movable in an XZ plane, and a support for the workpiece holding device (5) is arranged on a first front surface (82) of the frame element designed as the base plate (8), and a spindle support (15) of the tool spindle (2) is arranged on a second,is arranged in a mirror-symmetrical manner to the first front surface (82) and the rear surface (84) of the base plate (8). [2] Machine tool (1) according to claim 1, characterized by that two or three linear axes are arranged perpendicular to each other and thus parallel to the respective spatial axes of a Cartesian coordinate system (XYZ). [3] Machine tool (1) according to claim 1, characterized by , that the workpiece holding device (5) includes a first pivot axis (40A) in any arbitrary axis position, which is designed to rotate parallel to the Z-space axis. [4] Machine tool (1) according to claims 1 and 3, characterized by that the first pivot axis (40A), which moves the workpiece (6), is arranged parallel to the XY spatial plane when viewed in the starting position. [5] Machine tool (1) according to claim 1 and 3, characterized by, that the workpiece holding device (5) is pivotable about another arbitrary spatial axis, i.e. a second one, from the first pivot axis (40A) with moving pivot axis (50A), which is not designed parallel to the first pivot axis (40A). [6] Machine tool (1) according to claims 1, 3 and 4, characterized by that the second pivoting axis (50A), which pivots the workpiece (6), is particularly preferably arranged at right angles to the first pivoting axis (40A). [7] Machine tool (1) according to any one of claims 1 to 4, characterized by , that at least one spatial axis, in particular the X-spatial axis, is designed for moving the tool spindle (2) with two parallel linear guides (21) mounted as far apart as possible, wherein in particular at least one spatial axis, in particular the Y-spatial axis, is designed for moving the workpiece holding device (5) with two parallel linear guides (31) mounted as far apart as possible. [8] Machine tool (1) according to any one of claims 1 to 7, characterized by , that the machine tool (1) is equipped with electrically controllable drives (10, 20, 30, 40, 50), particularly preferably servo drives or stepper drives, for moving the tool spindle (2) and workpiece holding device (5) in the machining axes. [9] Machine tool (1) according to any one of claims 1 to 8, characterized by , that the machine tool (1) is designed with an enclosure, in particular a trough-like geometry (60), for capturing and removing chips and auxiliary media such as cooling lubricants and for sealing the machining area to the outside, wherein in particular an extraction system is provided by means of negative pressure and a bottom opening. [10] Machine tool (1) according to any one of claims 1 to 9, characterized bythat the machine tool (1) is designed with a tool magazine (48), wherein tools (3) can be automatically removed and placed from the tool magazine (48) by means of a controllable collet (9) by the tool spindle (2) which is movable in all three spatial directions relative to the tool magazine (48), wherein in particular the tool magazine (3) is designed with an elastic element, in particular an elastomer element with bores (49) which are slightly smaller than the corresponding shanks of the tools (3), whereby the tools (3) stored in the tool magazine (48) are held in these bores (49) in a vibration-proof manner, but can also be removed or inserted by the collet (9) without the actuation of actuators in the tool magazine (48), wherein in particular the tool spindle axis (2A) is designed to be movable in a spatial axis Z parallel to the XZ plane of the frame element.

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