WO2008113453A1

WO2008113453A1 - Machine for measuring or processing workpieces, in particular a coordinate measuring instrument

Info

Publication number: WO2008113453A1
Application number: PCT/EP2008/001370
Authority: WO
Inventors: Berthold Matzkovits; Joerg Walther; Heinz Broghammer; Wolfgang Wiedmann
Original assignee: Carl Zeiss Industrielle Messtechnik Gmbh
Priority date: 2007-03-22
Filing date: 2008-02-21
Publication date: 2008-09-25
Also published as: DE102007015152A1

Abstract

The invention relates to a machine for measuring or processing workpieces and, in particular, a coordinate measuring instrument, which has a machine frame with a machine head which can be moved relative to a workpiece. The machine frame has at least one hull with a lightweight, metallic hollow structure (24'). At least one guide rail (64), for a carriage which can be moved relative to said guide rail (64), is disposed at the hull. According to one aspect of the invention, the hull has a mating surface (51) to which the guide rail (64) is fastened and which is produced from a hardened, cast material (50).

Description

Machine for measuring or machining workpieces, in particular

coordinate measuring machine

The present invention relates to a machine for measuring or processing of workpieces, in particular a coordinate measuring machine, with a machine head which is movable relative to a workpiece holder, and with a machine frame, on which at least the machine head is arranged, wherein the machine frame at least one carrier body with a having metallic lightweight hollow structure, and wherein at least one guide rail for a relatively movable carriage is arranged on the carrier body.

The invention further relates to a method for producing a carrier body for a machine frame of such a machine, comprising the steps of: Producing a metallic lightweight hollow structure, and

Attaching at least one guide rail for a relatively movable carriage on the lightweight hollow structure.

Such a machine and such a method are known for example from DE 102 33 561 Al.

A coordinate measuring machine is a machine with a measuring head, which can be moved relative to a measuring object which is arranged in a measuring volume of the machine. The measuring head is brought into a defined position relative to a measuring point on the measuring object. In the case of tactile coordinate measuring machines, the measuring point is touched, for example, with a stylus arranged on the measuring head. Subsequently, the spatial coordinates of the measuring point can be determined based on the position of the measuring head in the measuring volume. If one determines the spatial coordinates of several defined measuring points on a measurement object, one can determine geometric dimensions or even the spatial form of the measurement object. A typical field of application for such coordinate measuring machines is the measurement of workpieces for quality control.

The present invention particularly relates to coordinate measuring machines, because the measuring head must be moved in coordinate measuring machines with a very high accuracy in order to determine the spatial coordinates of the measuring points with the desired high accuracy can. In addition, however, the present invention can be applied to machine tools and other machines in which a machine head is to be moved with high accuracy relative to a workpiece or other object.

In the case of the coordinate measuring machine known from DE 103 33 561 A1, the measuring head is arranged on a so-called quill, which can be moved in the vertical direction (Z direction). The quill is in turn arranged on an arm, which in horizontal Direction (X direction) can be moved. In addition, the arm can be moved in a further horizontal direction (Y-direction). Overall, the measuring head of this coordinate measuring device can therefore be moved in three mutually perpendicular spatial directions in order to touch a measuring point on a measured object.

The arm of the known coordinate measuring device is mounted on guide rails which are fastened to a so-called box carrier. The box carrier is realized in this case with a lightweight hollow structure, which consists of a variety of cross braces, bulkhead walls and side walls. The struts and walls are made of steel or steel sheets, which have been suitably bent and joined together. The guide rails on which the box carrier is mounted, are arranged on special steel strips, which in turn are truncated on the cross struts and Rare walls of the box Trager. Thus, the entire box carrier including the shots for the guide rails made of metal, which u.a. in view of a uniform thermal expansion coefficient is advantageous.

A disadvantage of the known coordinate measuring machine is the difficulty of forming the guide rails for the box carrier with the desired straightness and precision. A particular problem is the precise design of the steel strips on which the guide rails are attached. One possibility is then to bring these steel strips by machining (in particular milling and / or grinding) in the desired shape and orientation, after the steel strips were attached to the box carrier.

As it turns out, however, the precision with which the steel strips can be machined is limited in this case. It can come to ripples, which could probably be due to the different stiffness of the box stretcher in the area of the cross struts and off of it after examination of the Applicant. Furthermore, due to the lightweight construction and as a result of the resulting low wall thickness of the sheets, thermal problems in the Edit the box girder and the steel strips result. In particular, temperature differences can result from the machining, which lead to the fact that the box girder deforms with the steel strips during machining.

In principle, one could solve these problems by using sheets with higher wall thicknesses, since in this case both the local stiffness and the thermal diffusivity would be improved. However, sheets with larger wall thicknesses lead to a higher total weight of the box girder, which is disadvantageous because of the higher mass, because stronger and therefore more expensive drives and bearings are needed.

A variety of solutions are known in the art to realize guide surfaces or guide rails for a moving machine part on a machine frame.

DD 133 201 proposes to cast those parts of a machine frame which have guide surfaces of terrazzo and then to grind to size. The machine frame itself is to be made in this case of reinforced concrete, the Terrazzo mixture is first filled into the lowest parts of the mold and the casting mold is then filled with the concrete.

EP 0 201 821 A1 proposes to produce the guide rails on a work machine made of sinterable non-metals, in particular ceramic material. The ceramic material should be glued to a machine bed made of concrete or poured into this.

DE 39 19 450 A1 and DE 102 51 228 C1 also propose casting the rail guides together with a machine bed of polymer concrete. From DE 44 41 252 Al it is known to fasten guide rails made of steel on a carrier body of mineral casting material. Again, the guide rails are to be subsequently edited and sanded.

Against this background, it is an object of the invention to provide a machine of the type mentioned, which has very precise and linear slide guides, in particular for recirculating ball slide or the like, despite lightweight construction. It is a further object of the invention to provide a method for producing a carrier body for such a machine.

According to one aspect of the invention, a machine of the type mentioned is proposed in which the carrier body has a contact surface on which the guide rail is fixed, wherein the contact surface is made of a cured cast material.

According to a further aspect of the invention, a method of the type mentioned is proposed in which a contact surface for the positionally accurate attachment of the guide rail is formed on the support body by bringing the metallic lightweight hollow structure with an initially largely liquid potting material and with a shape gauge in contact is, wherein the potting material between the form and the lightweight hollow structure is cured.

The present invention thus proposes a "material mix" in which a lightweight hollow structure of sheet steel, thin-walled cast metal and / or other metallic materials is combined with a hardenable potting material, in particular a resin-based potting material The guide rails are in preferred embodiments of steel or a ceramic material. Due to the hardenable potting material, the contact surface can be formed with a very high degree of precision without the need for thermally problematic, post-processing machining. The potting material is cast onto the metallic lightweight hollow structure with the aid of a very precise shape gauge. As a result, the contact surface (more precisely: the cast body whose outer upper side forms the contact surface) can compensate for any manufacturing inaccuracies of the lightweight hollow structure. The quality and in particular the flatness and straightness of the contact surface is determined primarily by the precision of the shape gauge, with the help of the sprue. Since the shape of the template can be produced as a "heavy" molded body regardless of the lightweight hollow structure, the contact surface of the potting material can be produced with such high quality that no post-processing with thermal problems can be eliminated Removing excess potting material at locations that are irrelevant to the accuracy of the guide rails and / or to the introduction of holes, mounting holes or the like.On the other hand, all the advantages of a metallic lightweight hollow structure can be maintained.The above object is therefore achieved.

In a preferred embodiment of the invention, the carrier body has a trough-like depression, in which the casting material is arranged. Advantageously, the trough-like depression is permanently arranged on the lightweight hollow structure. The trough-like depression can be completely closed in the bottom region and on its side walls, or it can have drainage channels for the targeted draining off of excess casting material.

In a preferred variant, the trough-like depression is formed on the lightweight hollow structure, i. The trough-like depression is part of the lightweight hollow structure.

In another variant of the method, the trough-like depression is attached only for the production of the contact surface on the lightweight hollow structure, for example by means of molded parts made of foam, plastic or the like. In the After the casting material has hardened, these molded parts can be removed from the lightweight hollow structure so that the cast body with the contact surface sits practically "on top" of the lightweight hollow structure The molded parts made of foam, plastic or the like can also serve as a basis to complement the contour formed on the lightweight hollow structure to a trough-like depression.

These embodiments of the invention allow a very accurate training of the contact surface of the lightweight hollow structure. In the event that the trough-like depression is permanently arranged on the lightweight hollow structure, the permanent fixation of the contact surface is facilitated on the hollow structure. In contrast, a trough-like depression produced only for the casting process has the advantage that the lightweight hollow structure can be constructed and manufactured more simply.

In a further embodiment of the new method, the lightweight hollow structure and the shape gauge are attached to a separate holder, wherein the separate holder carries at least the shape of teaching.

This embodiment has the advantage that the separate holder accommodates the weight of the shape gauge at least to a substantial extent, so that the lightweight hollow structure is not deformed when casting the contact surface. For the same reason, it is preferred if the lightweight hollow structure is arranged stress-free on the separate holder. This embodiment allows a particularly accurate production of the guides for the movable carriage.

In a further embodiment, the lightweight hollow structure is placed on the form of teaching.

In this embodiment, the lightweight hollow structure is arranged above the shape of the form, so that no weight due to this arrangement of the molding teaching on the lightweight hollow structure presses. This refinement is particularly advantageous if the shape gauge is very heavy (and thus dimensionally stable).

An advantage of this embodiment is that it is possible to dispense with the use of a separate holder. In principle, however, this embodiment can also be used in conjunction with a separate holder, wherein the risk of deformation of the lightweight hollow structure is further reduced by the form of teaching.

In a further embodiment of the invention, the potting material forms a cast body which is glued to the carrier body. In a preferred variant of this embodiment, the cast body already adheres to the metallic lightweight hollow structure due to the potting material used. Alternatively or additionally, an additional or separate adhesive may be used.

The embodiment has the advantage that the position and position of the precisely produced contact surface also during transport and handling of the lightweight hollow structure, in particular before attaching the guide rails, is maintained. The handling of the intermediate product is simplified.

In principle, however, it is possible that the cast body "loosely" rests on the lightweight hollow structure and, for example, is fixed by fixing the guide rail in its position.

In a further embodiment, the cast body has a thickness perpendicular to the contact surface, which lies in the range between about 1 mm and about 20 mm. Preferably, the thickness of the cast body is between about 1 mm and about 5 mm, which does not necessarily depend on the exact compliance with the specified limits. Rather, in this embodiment, the casting body is relatively thin in comparison to the carrier body and to the guide rails. The cast body essentially acts as a thin intermediate layer or "underlay" which is arranged between the guide rail and the lightweight hollow structure, to provide a flat and accurately formed contact surface for attaching the guide rail. The thinner the cast body, the more advantageous it is with regard to the thermal expansion coefficients of the materials used.

The lower limit for the thickness of the cast body depends in an advantageous embodiment of the invention above all on how large the manufacturing tolerances of the lightweight hollow structure over the length of the guide rail. In other words, the thickness of the cast body mainly depends on the order of magnitude of the ripples and / or other shape deviations of the lightweight hollow structure, which are to be compensated with the aid of the cast body.

In a further embodiment, the contact surface has openings through which the guide rail is screwed to the carrier body.

This embodiment is advantageous because the contact surface or the cast body with the contact surface is held in a very simple and cost-effective manner permanently and stably in position. On the other hand, the cast body in this embodiment, no or only very small holding forces of the guide rail record. This makes it possible to form the contact surface or the cast body very thin.

In a further embodiment, the contact surface has a step profile, which forms a contact edge for the guide rail.

The contact edge is a perpendicular to the contact surface structure, which allows a very simple and precise mounting of the guide rail on the contact surface.

In a further embodiment, the contact surface is largely congruent to the guide rail. In this embodiment, the contact surface has a surface area which corresponds approximately to the surface area of the guide rail in a projection onto the contact surface. Preferably, the surface area of the contact surface is slightly larger than the corresponding surface extent of the guide rail in order to obtain a certain tolerance margin and a full-surface support of the guide rail. Regardless, the limitation of the contact surface on the corresponding surface extent of the guide rail has the advantage that the intermediate layer of potting material is used only where it is needed. This saves costs and weight. Another advantage is that several parallel guide rails are better decoupled from each other, which is advantageous in terms of thermal expansions of the potting material.

In a further embodiment, the contact surface is a closed surface on which the guide rail rests over its entire surface.

As an alternative to this embodiment, the contact surface could consist of several sections, which are arranged as a kind of support points below the guide rail. In contrast, the preferred embodiment allows a more stable and precise fastening of the guide rail.

In a further embodiment, the carrier body has a largely closed outer wall, on which the contact surface is arranged.

In this embodiment, the outer wall distributes the weight of the carriage running on the guide rail over a larger area. This avoids or reduces local deformations in the operation of the machine. In addition, this embodiment allows a very simple and inexpensive attachment of the guide rail through the cast body through by the guide rail is screwed to the outer wall. In a further embodiment, the potting material is a resin composition with an embedded filler material. In a preferred embodiment, the resin composition is an epoxy resin and the filler is a fine-grained and / or powdery filler which provides high pressure stability and low shrinkage upon cure. In contrast, the tensile stability of the potting material can be low since the cast body essentially serves as a high-precision underlay under the guide rail. A resin-based potting material can be easily and inexpensively processed and has led to very good results in practical experiments of the Applicant.

It is understood that the features mentioned above and those yet to be explained below can be used not only in the particular combination given, but also in other combinations or in isolation, without departing from the scope of the present invention.

Embodiments of the invention are illustrated in the drawings and are explained in more detail in the following description. Show it:

1 shows an exemplary embodiment of the new machine in the form of a coordinate measuring device with a horizontal measuring arm,

Figure 2 shows a carrier body in lightweight hollow structure for producing the

Measuring arm of Figure 1, wherein the carrier body is clamped in a holder for producing the contact surface,

FIG. 3 shows the carrier body from FIG. 2 with a top-mounted shape gauge,

Figure 4 shows the carrier body of Figure 3 after removing the form of teaching and screwing of guide rails, and Figure 5 is a simplified cross-sectional view of the carrier body of Figure 4 in the region of one of the guide rails.

In Figure 1, a coordinate measuring machine in its entirety is designated by the reference numeral 10. The coordinate measuring machine 10 is here a horizontal arm measuring device. However, the invention is not limited thereto and can advantageously also be applied to coordinate measuring devices in gantry or bridge construction or in a different construction. Furthermore, the invention could be used in the same way in machine tools or other machines in which machine parts must be moved with the highest possible precision on guide rails.

The coordinate measuring machine 10 has a base 12 _; on which a pillar 14 is arranged. The column 14 is seated on guide rails 16 and can be moved in the direction of the arrow 17. The movement axis 17 is usually referred to as X-axis. In a preferred embodiment, the column 14 is mounted on the guide rails 16 by means of recirculating ball slides, and it is moved in the direction of the movement axis 17 by means of a motor drive (not shown separately here)

The reference numeral 18 denotes a cross slide, which is arranged on the column 14. The cross slide 18 can be moved by means of a drive on guide rails 20 in the direction of arrow 21. The movement axis 21 is usually referred to as Z-axis. In a preferred embodiment, the cross slide 18 by means of recirculating ball slide (not shown in detail) is mounted on the guide rails 20.

The cross slide 18 has a support 22 on which a horizontal arm 24 is mounted. The arm 24 can be moved by means of a drive 26 in the direction of the arrow 28. The movement axis 28 is commonly referred to as Y-axis. In a gantry or bridge coordinate measuring machine, the Y-axis is demge Often the movement axis for the portal or the bridge, while the X-axis indicates the position of the carriage on the traverse of the portal or the bridge.

At the right free end of the horizontal arm 24, a measuring head 30 is arranged, which carries a stylus 32 here. The stylus 32 is used to touch a defined measuring point on a measuring object (not shown), which is arranged in the measuring volume 33 of the coordinate measuring machine 10. The measuring volume 33 is defined here by the maximum travel paths of the measuring head 30 along the three axes of movement 17, 21, 28. Within the measuring volume, a table or another workpiece holding receptacle can be arranged. In the present case, the workpiece holding receptacle is the bottom area within the measuring volume 33.

In the coordinate measuring apparatus 10, the arm 24 moves relative to the support fixed in the Y direction. In this case, the drive 26 is arranged on the support 22 and the arm 24 has guide rails, as explained below with reference to FIGS 2 to 5. In a preferred exemplary embodiment, the guide rails each run in a recirculating ball slide (not shown here), which is fastened to the support 22. Alternatively, the guide rails could be arranged on the support 22, while the recirculating ball slide are attached to the Hoπzontalarm 24. Ultimately, it is only important for the present invention that the guide rails serve to provide a - preferably linear - guide for a relative to the guide rails movable body.

The horizontal arm 24 is here a Tragerkorper, which is formed with a lightweight hollow structure according to the present invention. In contrast, in the present exemplary embodiment, the machine base 12 and the stand 14 are "solid." In principle, however, the teaching of the present invention can also be applied to these frame parts. In Figure 2, the horizontal arm is shown in an intermediate stage of the new manufacturing process and designated for differentiation by the reference numeral 24 '. The arm 24 'is here clamped between two holders 40a, 40b, which keep the arm 24' in a defined position stress-free. The arm 24 'here has a box-shaped profile with a total of four side walls, of which in Figure 2, the side walls 42 and 44 are designated. The side wall 44 points up here. At the right and left edges of the side wall 44 (seen in the longitudinal or extension direction of the arm 24), two trough-like depressions 46a, 46b are arranged here. As an alternative to the substantially closed side walls 42, 44 shown in Figure 2, the horizontal arm could also have a truss-like structure and / or the side walls 42, 44 in turn could have holes to achieve further weight reduction.

In the illustrated embodiment, the trough-like recesses 46 are milled out of a respective metal strip, wherein the metal strips were welded after the milling operation on the side wall 44 of the arm 24 '. Alternatively, the trough-like recesses 46 could be milled out of the sheet metal for the side wall 44, for example, or they could first be attached to the side wall 44 as solid metal strips and then milled out. In addition, the trough-like depressions 46 could in principle also be produced from bent metal sheets or in some other way.

In the illustrated embodiment, each trough-like recess 46 along its longitudinal direction has a plurality of evenly spaced bores 48, in each of which a thread is formed. The drill holes 48 are later used to screw metallic guide rails for the recirculating ball slide on the horizontal arm 24.

The reference numeral 50 denotes a potting material, the surface 51 after curing forms a contact surface for the guide rails (see Figure 4 and 5). For reasons of clarity, the potting material 50 is here only in one Part of the trough-like depression 46b shown. It is understood that both trough-like depressions 46a, 46b are filled with the potting material 50.

After filling the depressions 46a, 46b, a forming jig 54 is arranged on the height alarm 24 "(FIG. 3). In a preferred exemplary embodiment, the shape gauge has two projections 56 which are placed on the holders 40a, 40b so that the holders 40a, 40b largely absorbs the weight of the forming jig 54. The forming jig 54 has two forming surfaces 58, which form a negative impression of the contact surface 51. As can be seen in Figure 3, the negative impression transfers to the potting material 50. In a preferred embodiment The molding material 54 brings the potting material 50 into a precisely defined shape After the potting material 50 has hardened, the mold 54 is removed upwards with the aid of the ring sockets 60. Subsequently, the molding material 54 is removed can conventional metallic guide rails 64 on the abutment surfaces 51 plat decorated and screwed to the horizontal arm 24 '". By way of example, a screw in Figure 4 is designated by the reference numeral 66.

As indicated at reference numeral 68, the arm 24 '"has an opening and a cavity located therefrom which is traversed by internal transverse struts (not shown here). In a preferred embodiment, the arm 24' '' is made from steel sheets Wall thick approx. 2 mm. Depending on the desired and achievable bending and torsional rigidity, thicker or thinner sheets may also be used. Only in the region of the guide rails, in a preferred embodiment, a thicker sheet material is used to form the threads for securing the guide rails 64. This can be seen in the simplified cross-sectional illustration in FIG. Like reference numerals designate the same elements as before.

The material thickness di of the sheet for the side wall 44 is here about 6 mm. The material thickness d _{2 of} the cast body of the potting material 50 is about 5 mm. In the illustrated embodiment, however, the cast body has no thorough Going constant material thickness Λi, but instead it has a thicker material portion 72 which forms a lateral abutment edge for the guide rails 64 together with the contact surface 51.

As an alternative to the procedure illustrated in FIGS. 2 to 4, in another exemplary embodiment the shape gauge 54 is arranged below the horizontal arm 24. The potting material 50 is filled into a correspondingly formed depression on the forming jig 54. Subsequently, the arm 24 is placed with the lightweight hollow structure from above on the Formlehre 54. In this embodiment, it is possible to dispense with the holders 40a, 40b, although corresponding holders may nevertheless be used. This alternative approach is particularly useful when the shape gauge 54 is much heavier and stiffer than the arm 24.

In both embodiments, it may be necessary to remove an excessive portion of the potting material after curing. However, due to the described method, such excess material components are at most located laterally of the abutment surface 51, so that this machining of the cast body is relatively easy and problem-free, without influencing the accuracy of the carriage guides.

Instead of a lightweight hollow structure of bent and / or welded sheets, the carrier body could also be made of a thin-walled metal casting, in particular in a truss-like structure. A preferred casting material for this implementation is cast iron with embedded nodular graphite (known as ductile iron).

In order to obtain a defined contact pressure of the forming jig 54 on the potting material 50, it may be advantageous in embodiments of the new method if the forming jig 54 and the carrier body are clamped together, which is advantageously possible with the aid of the holders 40a, 40b. In all preferred embodiments, the guide rail 64 is completely against the contact surface 51. In this case, the contact surface 51 is advantageously a closed surface, which is arranged largely congruently under the guide rail 64.

Claims

claims

1. Machine for measuring or processing of workpieces, in particular coordinate measuring machine (10), with a machine head (30) which is movable relative to a workpiece holder (33), and with a machine frame (12, 14, 24) on which at least the Machine head (30) is arranged, wherein the machine frame (12, 14, 24) at least one support body (24) having a metallic lightweight hollow structure (24 '), and wherein on the support body (24) at least one guide rail (64) for a relatively movable carriage (22) is arranged, characterized in that the carrier body (24) has a bearing surface (51) on which the guide rail (64) is fixed, wherein the contact surface (51) made of a hardened potting material (50) is made.

2. Machine according to claim 1, characterized in that the carrier body (24) has a trough-like depression (46), in which the potting material (50) is arranged.

3. Machine according to claim 1 or 2, characterized in that the potting material (50) forms a cast body, which is glued to the carrier body (24).

4. Machine according to claim 3, characterized in that the cast body has a thickness (d ₂ ) perpendicular to the contact surface (51) which is in the range between about 1 mm and about 20 mm.

5. Machine according to one of claims 1 to 4, characterized in that the abutment surface (51) has openings (48) through which the guide rail (64) with the carrier body (24) is screwed.

6. Machine according to one of claims 1 to 5, characterized in that the abutment surface (51) has a step profile which forms a contact edge (72) for the guide rail (64).

7. Machine according to one of claims 1 to 6, characterized in that the contact surface (51) is largely congruent to the guide rail (64).

8. Machine according to one of claims 1 to 7, characterized in that the abutment surface (51) is a closed surface on which the guide rail (64) completely rests.

9. Machine according to one of claims 1 to 8, characterized in that the carrier body (24) has a substantially closed outer wall (44) on which the contact surface (51) is arranged.

10. Machine according to one of claims 1 to 9, characterized in that the potting material (50) is a resin composition with an embedded filler.

11. A method for producing a carrier body (24) for a machine frame (12, 14, 24) of a machine (10) for measuring or machining workpieces, comprising the steps of:

Producing a lightweight metallic hollow structure (24 '), and

Securing at least one guide rail (64) for a relatively movable carriage to the lightweight hollow structure (24 '"),

characterized in that on the carrier body (24) a contact surface (51) for the positionally accurate attachment of the guide rail (64) is formed by the metallic lightweight hollow structure (24 ') with a first substantially liquid potting material (50) and with a forming jig (54) is brought into contact, wherein the potting material (50) between the forming jig (54) and the lightweight hollow structure (24 ') is cured.

12. The method according to claim 11, characterized in that on the lightweight hollow structure (24 ') a trough-like recess (46) for receiving the potting material (50) is formed.

13. The method according to claim 11 or 12, characterized in that the lightweight hollow structure (24 ') and the form gauge (54) are fastened to a separate holder (40), wherein the separate holder (40) at least the shape gauge (54) wearing.

14. The method according to any one of claims 11 to 13, characterized in that the lightweight hollow structure (24 ') is placed on the form gauge (54).