AU6186599A

AU6186599A - Surface-area gantry system with linear direct drives

Info

Publication number: AU6186599A
Application number: AU61865/99A
Authority: AU
Inventors: Rudiger Hauschild
Original assignee: ACTech GmbH
Current assignee: ACTech GmbH
Priority date: 1998-07-23
Filing date: 1999-07-21
Publication date: 2000-02-14
Also published as: CA2338303A1; DE19833125A1; EP1098732B1; JP2002521214A; DE19981356D2; WO2000005028A3; EP1098732A2; WO2000005028A2; ATE212270T1; DE59900783D1

Abstract

The invention relates to a surface-area gantry system for machining, assembly and handling tasks, with three axes of motion in the directions X, Y and Z, where the Z axis is provided with machining or grasping mechanisms, notably for the high-speed machining of non-metallic materials. The aim of the invention is to create an especially light and stiff surface-area gantry system suitable for large machining areas and universal applications which consists of simple components and linear modules which are economical to produce even in small numbers and permits relatively high feed rates and accelerations. According to the invention the X, Y and Z axes have linear modules (2) which are driven by synchronous linear motors and consist of a hot-rolled shaped support section (12) having a rectangular or square cross-section and fitted with pair-wise, opposite secondary elements (10). The slides (3) or working slides (1) are made of cast metal in the form of integral components -hich are provided with a wrap-around element (4) for the X, Y and Z axis and contain the primary elements (5).

Description

Transtek Document No. GE1215 Area Gantry System with Linear Direct Drives The invention concerns an area gantry system with linear direct drives (linear motors) for machining, assembly and handling jobs with three axes of movement, in the x, y and z directions, which system is fastened on a supporting structure or to the machine frame, the z axis being provided with machining or gripping mechanisms, particularly for high-speed machining of nonmetallic materials. The term "area gantry system" was chosen because of the emergence in the technical literature of the term "area gantry robots," which have a comparable axis arrangement. Machine designs of this kind are referred to in other sources as cross-table structures. The area gantry system has three axes of movement, in the x, y and z directions, and is fastened to a supporting structure or a machine frame. A wide variety of machining or gripping mechanisms (z axis) with or without a pivot and swivel axis can be installed, depending on the job concerned (e.g. main spindle drives; cutting lasers; spot-welding pliers; welding, soldering, gluing, coating, grinding, bolting and riveting apparatus; etc., up to and including assembly and handling grippers of any kind). For HSC [high-speed cutting] machining, in particular, it is important to achieve high rigidity for the frame components and guide components while simultaneously keeping moved masses to a minimum. In the case of multi-axis systems, series-produced components and modules often fail to give the desired results. High machine acceleration speeds with simultaneously high rigidity must then be purchased at heavy cost, and entail many compromises. In the prior art, for example, Patent DE 43 15 762 discloses a two-dimensional drive system with intersectingly arranged guide bars, and DE 38 19 278 a double linear guide with separate guide and drive shafts mounted laterally in bearing blocks. The loading capacity and overall length of the spindles is limited, however. Furthermore, according to German Patent Application (Unexamined) 41 06 620, gantry systems for traveling slides can be composed of girder sections made from aluminum as extruded sections. The 1 Transtek Document No. GE1215 girder section, which is intended to be distinguished by an especially low weight per unit length, must be provided with the highest possible bending resistance moment -- hence with a comparatively large cross section -- and with hardened profile bar to resist the wear that must be expected. The profile bar has no beneficial effect on the resistance moment. Thus, the dimensions cannot be kept within very small limits and oscillations are not substantially reduced. The object of the invention is to provide an especially light-weight and rigid area gantry system for large machining areas, universal ranges of application, and, in particular, high-speed machining of nonmetallic materials and composites. The area gantry system is to be made of simple components and linear modules that are inexpensive to manufacture, even in small quantities. Relatively high feeds and rates of acceleration are to be achieved. According to the invention, the object is accomplished in an area gantry system in that the x, y and z axes are provided with linear modules driven by synchronous linear motors. The modules are divided into girder sections, slides and work slides. The girder sections are hot-rolled and have a rectangular or square cross section. They are provided with secondary elements mounted opposite each other in pairs. The slide or the work slide is made of cast metal as an integral unit, with wrap-arounds for the x, y and z axes, and contains the primary elements. The advantages of the invention lie in an especially light-weight, rigid, simple and compact area gantry system that can be manufactured inexpensively, even in small quantities, for large machining areas. Only one, standard design principle is needed to produce linear modules of integral construction. The dimensioning of the modules can be done on the basis of standard calculation models. The production drawings can be derived from the results of these calculations through the design of a variant. The area gantry system can thus be configured to withstand the stresses of any application. The use of identical and similar parts in the modules simplifies construction and reduces costs. The design principle utilizes the advantages of cast and welded construction and composite construction. The combined use of cast and welded parts makes for relatively few individual components and assembly units and comparatively delay-free construction of the portal 2 Transtek Document No. GE1215 system with good dimensional accuracy. The area gantry system is symmetrical in structure, thus virtually eliminating tipping problems. The especially light-weight and rigid design of the moving machine parts results in very low machine weight, thus simplifying the erection of the machine and reducing the associated costs. Keeping moved masses to a minimum produces still further effects, such as improved machine dynamics, relatively high axial accelerations and speeds with very low acceleration forces, and very low power consumption during operation. The very high forces of attraction between the primary and secondary parts of the synchronously operating linear motors are offset by the opposite arrangement of the motors. This reduces the stress on the linear guides and increases their service life. On the whole, smaller, lighter and less expensive classes of products can be used. Furthermore, the linear motors, the linear guide and the longitudinal measuring system are protected against contamination under a common bellows. In the machining of nonmetallic materials, it is not absolutely necessary for the linear motors to be protected by a bellows if they are installed in a vertical position. In such cases there is an air gap between the primary and secondary parts in the direction of the force of gravity. Deposits of removed material cannot accumulate. Dust wipers may be necessary, especially in the case of electrostatically charged dusts. The non-wearing linear motors can thus remain operable at all times. This ensures high system reliability. In contrast to conventional spindle drives, linear motors operate without wear. A further advantage can be achieved in that the slides and the work slide can be manufactured quickly and economically, in small quantities with a lot size of as little as one unit, in the form of heavily ribbed, thin-walled, low-weight, high-rigidity metal castings, via lost molds by the use of a prototype pattern set, by direct laser-sintering of Croning@ sand, or by direct milling of mold material based on CAD data. All the moving linear axes of the machine frame include a girder section made of commercially available pipe of rectangular cross section. The girder sections are of simple welded construction. Connecting flanges are welded to the ends, while braces can be attached to the unoccupied longitudinal side of the girder section. The girder section is designed in such a way as to minimize welding delays. According to a further embodiment of the invention, it is provided to increase the bending rigidity and torsional rigidity of the girder sections by complete or partial foam-filling with foamable 3 Transtek Document No. GE1215 aluminum material or another suitable foamable metal. A further increase in bending rigidity and torsional rigidity is achieved by means of an arrangement of web plates, the outer contour of the web plates being sized to the inner contour of the girder section. Web plates are available in planar and offset versions. A combination of both versions is possible. Especially rigid structures are obtained by the use of offset web plates in a tilted arrangement. Web plates can be made with holes. The web plates are arranged on one or more parallel bars, sections, pipes or special-section pipes and affixed to them by welding. The length of the arrangement corresponds to the length of the girder section to be reinforced. The spacing, number and arrangement of the web plates are determined by the stress to which the girder section will be subjected. The arrangement is placed in the girder section and a set quantity of a foamable aluminum material or other suitable foamable metal, in the form of sintered compacts, is fed into the voids between the web plates. Foamable sintered compacts are made, for example, from powdered aluminum alloy and propellant. Foam materials of prior art can be used. A fluxing agent pre-integrated into the sintered pellet or sprayed into the void before foaming can additionally be used to improve the creep behavior and contact behavior of the metal foam. With the web plate arrangement, the girder section must be completely filled with foam. Foam-filling of girder sections requires a relatively large annealing furnace or the use of induction coils. Vent bores are provided in the section. The girder section is brought to the foam temperature. The molten metal creeps into the gap between the contour surface of a web plate and the inner surfaces of the girder section under capillary action or due to the addition of a fluxing agent. The foamed metal is unable to form foam structures in the gap itself, so that after cooling the web plates remain fixed in place as in soldering. The metal foam merely serves to convey molten metal into each gap and to grip the web plates to keep them from buckling or warping. The compressive strength of the joint between the contour surface of the web plate and the inner surface of the girder section is higher than that of the foamed material. The web plates are therefore able to brace the walls of the girder section against deformation and to form an effective ribbing. According to a further embodiment of the invention, it is provided to increase the bending rigidity and torsional rigidity of the girder sections by an arrangement of web boxes composed of two or more planar or offset (holeless) web plates and spacers or composed of shaped sheet-metal parts, the outer contour of the metal sheets being sized to the inner contour of the girder section and all the components of the web boxes being joined to one another by welding. Web boxes are available in planar or offset versions. A combination of both versions is possible. The web boxes are 4 Transtek Document No. GE1215 arranged on one or more parallel bars, profile sections, pipes or special-section pipes and secured by welding. The length of the arrangement corresponds to the length of the girder section to be reinforced. The arrangement is placed in the girder section and a set quantity of a foamable aluminum material or other suitable foamable metal, in the form of sintered compacts, is fed into the voids of the web boxes. With a web box arrangement, the girder section is partially filled with foam. The metal foam serves to convey molten metal into each gap between the contour surfaces of the web box and the inner surfaces of the girder section and to form a rib together with the metal sheets of the web box, which act as a casing. The procedure for filling the voids of web boxes in girder sections with foam is similar to that used with the web plate variant. If pipes or special section pipes are integrated into the girder section, the void formed by the pipe section can be used as a conduit for energy transmission lines. According to a further embodiment of the invention, it is provided to increase the bending rigidity and torsional rigidity of the girder sections by securing in the girder section a truss that is connected to the walls of the girder section by an arrangement of web plates or web boxes. The web plates or web boxes are fastened by welding to the stringers of the truss, preferably at its joints. The truss can be composed of bars, profile sections, pipes or special-section pipes and is a welded structure that has bearing properties of its own. The length of the arrangement corresponds to the length of the girder section to be reinforced. The ends of the pipes are sealed to preserve the voids inside the pipes. The arrangement is placed in the girder section and a set quantity of a foamable aluminum material or other suitable foamable metal, in the form of sintered compacts, is fed into the voids between the web plates or into the voids of the web boxes. The web plates and web boxes are subject to the same influences as described above. The metal sheets are therefore able to brace the walls of the girder section against deformation and to transmit forces to the internal truss. A foamable aluminum material is preferably used. For this purpose, a mixture of powdered aluminum or powdered metal and a propellant, such as titanium hydride, is sintered or pressed at a temperature below the melting point to yield a semifinished product that contains the as-yet undecomposed propellant. 5 Transtek Document No. GE1215 The invention will now be described in further detail on the basis of an exemplary embodiment and with reference to drawings, wherein: Fig. 1 shows an area gantry system with a singly guided work slide, Fig. 2 shows an area gantry system with a doubly guided work slide, and Figs. 3 to 12 show various embodiments of girder sections for area gantry systems, which are reinforced by means of an arrangement of web plates or web boxes fixed in or by means of aluminum foam or another suitable metal foam. This small selection of embodiments is intended to suggest the possibilities that exist for arranging web plates or web boxes on bars, profile sections, pipes, special-section pipes or trusses and securing this arrangement in the girder section by means of a suitable metal foam. No claim to completeness is made. Figure 1 shows an area gantry system having a singly guided work slide 1 and comprising in the x direction two stationary linear modules 2 disposed at the appropriate distance from each other, on both sides of and parallel to the work area 11. The linear modules 2 are divided into girder sections 12 comprising a slide 3 or a work slide 1. The work slide 1 and the slides 3 are heavily ribbed, thin walled castings of very low weight and high rigidity. They have a bearing function and simultaneously serve as a housing for mechanical components. The girder sections 12, work slide 2 [sic] and slides 3 are FEM-optimized . Each linear module 2 is provided with two oppositely disposed, synchronous linear motors. The secondary parts 10 of the linear motors are adhered to girder section 12 in the form of rare-earth magnets or are mounted conventionally by means of carrier rails. The linear modules 2 in the x direction are operated in pairs and have the same power rating (gantry axis). Together they form the x axis. A slide 3 is guided and driven on each linear module 2 in the x direction. Said slide [3] is provided with a forked wrap-around 4 to receive the primary parts 5, the trolley 6, the clamping and shock-absorbing elements 7 and the reading head 8 for the longitudinal measurement system. A linear module 2 is disposed in the y direction at right angles to the x axis. Said linear module [2] is connected to slide 3 via a bolted-on flange 9 and spans the work area 11. Linear module 2 in the y direction carries a work slide 1. In the work slide 1, the linear modules 2 of the y and z axes are guided and driven at right angles to each other. The work slide 1 is provided with two forked wrap-arounds 4 for both axial directions. The linear module 2 in the z direction has at its end facing the work area 11 a recess 13 (not shown in further detail) for the attachment of machining or gripping mechanisms. TRANSLATOR'S NOTE: FEM = F6ddration Europ6enne de la Manutention [European Handling Federation]. 6 Transtek Document No. GE1215 Figure 2 shows an area gantry system having a doubly guided work slide 1 and comprising in the x direction two stationary linear modules 2 that are disposed at the appropriate distance from each other, on both sides of and parallel to the work area 11. Together they form the x axis. One slide 3 is guided and driven on each linear module 2 in the x direction. Said slide [3] is provided with a forked wrap-around 4 to receive the primary part 5, the trolley 6, the clamping and shock-absorbing elements 7 and the reading head 8 for the longitudinal measurement system. Two linear modules 2 are disposed in the y direction at right angles to the x axis. Said linear modules [2] are fixedly connected to the slide 3 via bolted-on flanges 9 and span the work area 11. Together they form the y axis. Linear modules 2 in the y direction carry a work slide 1. In the work slide 1, linear modules 2 of the y and z axes are guided and driven at right angles to each other. The work slide 1 is provided with forked or closed wrap-arounds 4 for both axial directions. The linear module 2 in the z direction has at its end facing the work area 11 a recess 13 for the attachment of machining or gripping mechanisms. The symmetrical design of the area gantry system virtually eliminates tipping problems. Figure 3 shows a girder section 12 containing a linear arrangement of planar web plates 14, which arrangement is fastened by welding to rods 15 and is secured in the girder section 12 by completely filling the voids 16 between the web plates 14 with foam. Figures 4, 5 and 6 show girder sections 12 with variants of a linear arrangement of bent or offset web plates 14, which arrangement is fastened by welding to rods 15 and is secured in the girder section 12 by completely filling the voids 16 between the web plates 14 with foam. Web plates 14 disposed obliquely in the girder section 12 yield a higher bending and torsional rigidity for the girder section 12 than do perpendicularly disposed web plates 14. Figure 7 shows a girder section 12 containing a linear arrangement of planar web plates 14, which arrangement is fastened by welding to pipes 17 and is secured in the girder section 12 by completely filling the voids 16 between the web plates 14 with foam. The voids 18 in the pipes 17 are preserved and can be used as a conduit for energy transmission lines or, subject to certain design prerequisites, for the storage and conveyance of liquid or gaseous media. 7 Transtek Document No. GE1215 Figure 8 shows a girder section 12 containing a linear arrangement of planar web plates 14 that are fastened by welding to rectangular or square special-section pipes 19 and are secured in the girder section 12 by completely filling the voids 16 between the web plates 14 with foam. The voids 18 in the special-section pipe 19 are preserved and can be used as a conduit for energy transmission lines. Figure 9 shows a girder section 12 containing a linear arrangement of planar web plates 14 that are fastened by welding to the stringers 12 of a truss 23, preferably at the joints 22 of said truss 23, and are secured in the girder section 12, along with the truss 23, by completely filling the voids 16 between the web plates 14 with foam. If the truss 23 is constructed of pipes 17, these are closed at their ends to preserve the voids 18 in the pipe. Figure 10 shows a girder section 12 containing a linear arrangement of planar web boxes 24 that are fastened by welding to rods 15 and are secured in the girder section 12 by completely filling the voids 25 in the web boxes 24 with foam. Figure 11 shows a girder section 12 containing a linear arrangement of offset web boxes 24 that are fastened by welding to rods 15 and are secured in the girder section 12 by completely filling the voids 25 in the web boxes 24 with foam. Web boxes 24 disposed obliquely in the girder section 12 can yield a higher bending and torsional rigidity for the girder section 12 than the perpendicularly disposed web boxes 24 of Fig. 10. Figure 12, finally, shows a girder section 12 containing a linear arrangement of planar web boxes 24 that are fastened by welding to the stringers 21 of a truss 23, preferably at the joints 22 of said truss 23, and are secured in the girder section 12, along with the truss 23, by completely filling the voids 25 between the web boxes 24 with foam. If the truss 23 is constructed of pipes 17, these are closed at their ends in order to preserve the voids 18 in the pipes 17. Further combinations for the reinforcement of girder sections 12 are possible. Figures 3 to 12 are only a few selected embodiments. 8 Transtek Document No. GE1215 After being filled with foam, the girder section 12 is finish-machined. In one set-up, insofar as possible, the mounting surfaces are milled flat and all the holes are made. Threaded holes are advantageously made in the walls of the girder section 12 by means of thread formers. In addition, machine screws must be fastened securely in the metal foam by means of dowels, threaded inserts, threaded holes or other fastening solutions. 9

Claims

1. An area gantry system with linear direct drives (linear motors) for machining, assembly and handling jobs with three axes of movement, in the x, y and z directions, which system is fastened on a supporting structure or to the machine frame, the z axis being provided with machining or gripping mechanisms, particularly for high-speed machining of nonmetallic materials, characterized in that the x, y and z axes are provided with linear modules (2) that are driven by synchronous linear motors, are composed of a hot-rolled girder section (12) of rectangular or square cross section, are provided with secondary elements (10) disposed oppositely in pairs, and comprise slides (3) and work slides (1) made of cast metal as integral units, which are realized with a wrap-around (4) for the x, y and z axes and contain the primary elements (5).

2. The area gantry system of claim 1, characterized in that in the case of a doubly-guided work slide (1) with two parallel girder sections (12), two wrap-arounds (4) are provided that surround the girder sections (12) in a fork-like manner.

3. The area gantry system of claims 1 to 2, characterized in that the slides (3) and the work slide (1) are realized as heavily ribbed, thin-walled metal castings that are distinguished by their very low weight and high rigidity and are fabricated via lost molds by the use of a prototype pattern set, by direct laser-sintering of Croning@ sand, or by direct milling of mold material based on CAD data.

4. The area gantry system of claims 1 to 3, characterized in that the rare-earth magnets of the secondary elements (10) are fastened directly on the girder section (12).

5. The area gantry system of claims 1 to 4, characterized in that the bending rigidity and torsional rigidity of the girder sections (12) of the x, y and z axes is increased by complete or partial filling with foamed metal, especially aluminum. 10 Transtek Document No. GE1215

6. The area gantry system of claims 1 to 5, characterized in that the girder section (12) contains an arrangement, secured on rods (15), pipes (17), stringers (21) or special-profile pipes (19), of precisely fitted web plates (14) of planar and/or offset design, disposed transversely to the longitudinal axis of the girder section (12), the voids (16) between the web plates (14) being filled, for purposes of reinforcement, with a set quantity of a foamable metallic or aluminum material.

7. The area gantry system of claims 1 to 5, characterized in that the girder section (12) contains an arrangement, secured on rods (15), pipes (17), stringers (12) or special-section pipes (19), of precisely fitted web boxes (24) formed of two web plates (14) of planar and/or offset design or of shaped sheet-metal parts and disposed transversely to the longitudinal axis of the girder section (12) and connected to one another via plural short spacers, thereby forming voids (25) which are filled, for purposes of reinforcement, with a set quantity of a foamable metallic or aluminum material.

8. The area gantry system of claims 1 to 5, characterized in that the girder section (12) contains a truss (23) of welded construction and composed of rods (15), profile sections, pipes (17) or special-profile pipes (19) and on whose stringers (21) are disposed, transversely to the longitudinal axis of the girder section (12), preferably at the joints (22), precisely fitted web plates (14) or web boxes (24) of planar design that connect the girder section (12) to the truss (23), the voids (16) between the web plates (14) or the voids (25) in the web boxes (24) being filled, for purposes of reinforcement, with a set quantity of a foamable metallic or aluminum material.

9. The area gantry system of claims 1 to 5, characterized in that the girder section (12) contains inserts of pipe (17) or special-section pipe (19) that form voids (18) in the longitudinal axis of the girder section (12) after it has been filled with foam, the ratio of the sums of the inner cross-sectional areas of the inserts to the inner cross-sectional area of the girder section (12) being no more than 1/2 and the distance between the inserts and between an insert and the inner surface of the girder section (12) having a lower size limit which is 1/5 to 1/10 the average length of the sides of the cross section of the girder section. 11