DE10148954B4 - Device for compensation of deformations on clamping surfaces of machines - Google Patents

Abstract

The present invention is an apparatus for compensating deformations on clamping surfaces (1) of machines (2). This device is characterized by at least one compensating element (4) arranged in the region of the clamping surfaces (1). This compensating element (4) has at least two location-dependent different moduli of elasticity (εA, εB). The size of these respective moduli of elasticity (εA, εB) can be adapted to the location-dependent expected surface pressure (P1, P2) in such a way that the total deformation (tges) of the machine (2) including compensating element (4) over the entire loaded clamping surface (1) Seen location independent within predetermined limits is the same.

Description

The invention relates to a device for compensation of deformations on clamping surfaces of machines, in particular to compensate for deformation-related gap formations on Werkzeugaufspannflächen of presses, hydroforming machines, injection molding machines, etc ..

In such machines high tool clamping forces must be applied. The introduction of force usually takes place via fixed and movable machine spars, against which associated tools (usually two tool halves) are supported.

As a result of the high forces to be transferred, the machine spars lying in the force flow deform elastically because of the transverse forces to be transmitted by shear deformation. In addition, bending moments to be transmitted lead to bending deformation. Consequently, in the past, the relevant machine spars have been designed for maximum rigidity. This is expensive.

In addition, the opening up of the two mold halves in the closing level, for example, in hydroforming machines and (plastic) injection molding machines must be avoided at all costs. Otherwise, there is a risk that the material to be formed flows out of the associated separating gap or swells out. This results in injection molding tools to an undesirable burr formation on the workpiece. In the worst case, conditional tool damage can not be prevented. Therefore, in practice, attempts have been made to avoid the described opening up by "overpressing" the associated tool. For this purpose, locking forces must be applied, which are ultimately much larger than would be required if no deformation. Such an approach increases the plant engineering effort and thus the costs.

Although it has been tried in the past to avoid the inclination of an associated ram when pressing. Such a ram parallelism on a multi-point press with hydraulic pressure pad is, for example, in the DE 196 42 587 A1 described. Here, the individual spring strips in the pressure points can be changed so that occurring as a result of eccentric load different longitudinal deformations of frame and connecting rod can be compensated by reducing the stiffness of the associated pressure pad or. The respective pressure pad is connected to a pressure accumulator and is supplied with gas pressure and also has an oil pad. Such measures can not be used universally, let alone retrofitted. Also, the associated technological effort is considerable. - Here the invention aims to provide a total remedy.

The invention is based on the technical problem of specifying such a device for compensation of deformations on clamping surfaces of machines, which is simple and inexpensive and can be easily retrofitted.

To solve this problem is the subject of the invention is a device for compensating deformations on clamping surfaces of machines, in particular to compensate for deformation-related gap formations on Werkzeugaufspannflächen of presses, hydroforming machines, injection molding machines, etc., wherein at least one arranged in the clamping surfaces compensating element, which is substantially transversely to the direction of force - depending on location - has at least two different moduli of elasticity whose respective size is adapted to the location-dependent expected surface pressure in such a way that the total deformation of the machine including compensating element over the entire loaded clamping surface seen anywhere within predetermined limits is the same and
the compensating element is designed as a solid body in the longitudinal direction, sandwiched by two or more layers of different materials with different moduli of elasticity and with optionally varying thickness,
or
the compensating element is embodied as a body made of a single material predetermined modulus of elasticity with inserted cavity for reducing the associated modulus of elasticity at this point, wherein the cavity is completely or partially filled with a support core.

D. h., The clamping surfaces move under load within predetermined limits parallel to each other. The limits in question take into account the respective requirements of the machine equipped with the compensating element.

Ideally, of course, you will try to set the limits as close as possible or to achieve a zero variation. In practice, however, it is quite possible to accept deviations from the parallelism of the clamping surfaces, which is reflected in the relevant marginal information. It is also permitted that within this range the total deformation of the machine including compensation element is settled.

The expected surface pressure and the resulting design of the compensation element can be empirically determined by experiments. It can, for example, on a - im Compared to the machine to be equipped - similarly constructed reference machine used and determined the force distribution on the clamping surfaces with corresponding transducers and evaluated. From the respective values for the surface pressure conclusions can then be drawn on the design of the compensation element with respect to the respective location-dependent modulus of elasticity. Thus, the compensation element is usually dimensioned so that in the region of a locally high surface pressure and deformation a high rigidity ("hard material" with high modulus of elasticity) of the compensation element is set, while a low surface pressure and low deformation meets a softer spring characteristic. This ensures the bottom line that the total deformation of the compensating element including the machine, taking into account the location-dependent different surface pressures and deformations over the entire surface seen equal values (within the specified limits) occupies.

This has the consequence that the clamping surface or the adjoining tool usually adjoining the compensating element is also acted upon without deformation and undergoes a homogeneous force introduction, from which the desired parallel displacement of associated tool halves then results.

The compensating element may be an adapter inserted between the (movable) machine part and the associated clamping surface (eg tool surface). However, it is also conceivable to integrate the compensating element directly into the machine part (for example, in the upper and / or lower rail of a press). Such a procedure is recommended when redesigning and rebuilding an associated machine or press, while the adapter solution is predestined for retrofitting.

In particular, the compensating element may be a solid body of two or more materials having different moduli of elasticity. In this case, the invention recommends sandwiching the compensating element in the transverse direction of force or in its longitudinal direction from two or more layers of different materials with optionally varying thickness. This sandwich structure of the compensation element thus extends in a plane on which the vectors of the introduced force are substantially perpendicular. Consequently, the location-dependent different surface pressures of each changing layer sequences and / or thicknesses of the individual materials are added, so that it is immediately apparent how this can represent the desired changing spring stiffness with the different degrees of deformation.

Because each level segment of the compensation element has a characteristic layer structure. This results in a certain degree of deformation, which depends on the modulus of elasticity of the material present at the point and its thickness.

As materials for the representation of the massive compensation element, the invention recommends, for example, iron material and a high-strength plastic. This combination of materials can be easily realized because iron materials and associated plastics can be combined with one another without difficulty by means of injection molding or encapsulation. D. h., The production of a thus constructed compensating element is inexpensive.

As an alternative to a massive embodiment of the compensating element, the invention also recommends a variation in such a way that the compensating element is a body made with a hollow space made of a single material of elasticity. This cavity extends advantageously in the areas that experience a lower surface pressure locally. Because with the cavity is known to reduce the associated modulus of elasticity connected at this point.

Of course, it is also possible to introduce a plurality of cavities into the compensating element in the manner of a column. As a result, in the context of this variant, location-dependent surface pressures can also be taken into account. Finally, the cavity can advantageously be completely or partially filled with a support core. Then even elasticity modules can be realized at this point, which initially (when the material expands into the remaining cavity) decrease and then increase again during deformation of the support core. In the same way, a progressive course of the modulus of elasticity or the associated spring constant can thereby be represented. The same applies to a degressive course.

Usually, the different moduli of elasticity of the materials or cavity formations within the compensation element are designed so that a preset relationship is achieved. For example, ratios of 10: 1 to 100: 1 are conceivable. Of course, the compensation element can also be composed of several segments with different spring characteristics. Such an approach is required, for example, when in a press the associated tool halves in the longitudinal and transverse directions (x and y direction) to each different fissures tend. Then it is necessary to work with a suitably adapted course of the spring characteristics in the x-direction and independently thereof in the y-direction. The resulting modulus of elasticity thus represents a function of the x and y coordinates, thus assuming the shape of a surface in three-dimensional space.

Either way, the compensation element can be characterized by a locally varying replacement modulus of elasticity, which is adapted to the total loads to be expected there from, for example, by bending, shear deformation, compression, etc. As a result, an idea-level tool clamping surface can be realized even under load, because bending and shear deformations are completely compensated.

Usually, the compensation element and an associated tool, in particular clamping tool, form a unit. Taking into account the required actuating forces, this unit has a fixed (location-independent) overall deformation and can thus be used independently of the machine. In other words, with knowledge of the attacking actuating forces, the unit including the compensating element can be calibrated and used on various other machines.

As a result, a device for compensating deformations on clamping surfaces of machines with an associated compensation element is provided, which is initially simple and inexpensive. Because in the compensation element is usually a mostly cuboid body made of two or more materials of different moduli of elasticity. Likewise, a regular cuboid body can be realized with introduced at the desired location cavity.

Because the layers of the different materials for the representation of the sandwich-like structure of the compensating element are constructed and arranged differently, a spatially changing course of the self-adjusting substitute elastic modulus can be represented, in both the x and y directions. If the moduli of elasticity are approximately constant under compressive stress (linear stress-strain curve), a uniform lowering of the workbench can be achieved, regardless of the magnitude of the external load. This linear lowering can also be fixed by hydraulic locking cylinders. Further advantages and measures of the invention will be explained with reference to the following description of the figures.

Show it:

1a . 1b schematically a 4-pillar / 2-Holmpressmaschine with the occurring there bends and gaps, in perspective ( 1a ) and schematically in section ( 1b )

2a . 2 B a 2-pillar / 2-bar press in comparable presentation,

3 a stress-strain diagram for two different materials,

4 a longitudinal section through a compensating element in a first variant,

5a . 5b two different sections through the object 4 along the lines CC (cf. 5a ) and DD (cf. 5b )

6 a second variant of the compensating element in section,

7 the calculated design of a compensation element for a machine according to 2 .

8th Half cuts through 7 in z, y plane of the areas X ₀ to X ₅ and

9 Half cuts through 7 in z, x-plane of the areas Y ₀ to Y ₅ schematically.

In the figures, a device for compensating deformations on clamping surfaces 1 of machines 2 shown. In the context of the embodiment, it is about the compensation of deformation-related gap formations 3 at associated clamping surfaces or Werkzeugaufspannflächen 1 of presses 2 , Of course, differently designed machines 2 be equipped with the device to be described below. These include, for example, hydroforming machines, injection molding machines, etc.

According to the invention, at least one in the region of the clamping surfaces 1 arranged compensation element 4 provided, whose placement is schematically in the 2a can be seen. There are two different compensation elements 4 realized, which are each designed as an adapter, which between an associated machine part 6 and the clamping surface 1 is inserted. At the machine part 6 it is a machine superstructure 6 with two upper bars 7 , which in combination with a machine substructure 8th with two Unterholmen 9 ensures the application of the required pressing forces (cf. 1 and 2 ).

Based on 4 and 5 you realize that the compensation element 4 essentially transversely to the direction of force F (z-direction), ie in the x and / or y direction with at least two location-dependent different moduli of elasticity ε _A and ε _{B is} equipped. The size of these moduli of elasticity ε _A and ε _B is adapted to the location-dependent expected surface pressure P ₁ and P ₂ and the resulting changing deformation.

The associated surface pressures P ₁ and P ₂ can best be determined by the 2 B recognize and result from the inadequately compensated back pressure of a compact, which leads to the avoidable gap formation 3 leads. The different size of the surface pressures P ₁ and P ₂ manifests itself on the basis of the respective different lengths of the associated vectors.

In this case, the location-dependent varying elastic moduli ε _A and ε _{B are} shaped to the respective surface pressures 21 and P ₂ adapted that the total deformation t _{ges of} the machine 2 including compensating element 4 over the entire loaded clamping surface 1 Seen location independent within predetermined limits is the same. This has the consequence that the respective clamping surfaces 1 move under load within the given limits parallel to each other and not (more) to the gap formation 3 comes.

The respective different surface pressures P ₁ and P ₂ can be detected empirically by experiments using a reference machine. In the same way simulations can be made. These take into account all expected deformations on the machine by means of the Finite Element Method (FEM) 2 as part of a computer-aided calculation model. On the other hand, the empirical values can be determined by pressure or force sensors or determined using, for example, a stress-optical model.

As described, the compensation element is 4 around an adapter, which is between the machine part 6 . 8th and the clamping surface 1 is inserted. But it is also possible, the compensation element 4 directly into the upper beam 7 and / or in the lower beam 9 to integrate. - Evidently the 4 is it in the compensation element 4 around a solid body of two materials, namely the material A and B. The modulus of elasticity ε _{A of} the material A is much larger than the modulus of elasticity ε _{B of} the material B formed. Ratios of ε _A : ε _B ≈ 10: 1 to 100: 1 are conceivable here.

One recognizes that the compensation element 4 sandwiched in the longitudinal direction of two or more layers of different materials A and B is formed. In addition, the materials A and B still have a location-dependent varying thickness t _A and t _B In the embodiment, it is the material A to a "hard" iron material, while the material B is designed as a "soft" plastic material. Their respective stress-strain diagrams are in 3 shown, wherein the solid line corresponds to the material A, while the dotted line refers to the material B.

The 5 makes it clear that at a cut through the 4 along the line CC ( 5a ) a different composition of the material pairing AB is present in comparison to a section along the line DD (see. 5b ). In fact, the (hard) material A has in the area of the section after the 5a over a small thickness t _AC , while on the other hand, the (soft) material B occupies the majority t _BC . When cutting in the 5b the conditions are reversed.

As a result, the compensation element 4 is formed in the region of the section CC "softer" overall, since there is a greater thickness proportion t _{BC of} the softer material B ( 5a ). In contrast, the compensation element 4 when approaching the section DD after the 5b increasingly "harder", since the thickness proportion t _{AD of} the harder material A in comparison to the thickness portion t _{BD of} the soft material B increases.

In the event that same surface pressures P on the compensation element 4 Consequently, in the illustrated regions CC or DD, different deformations t _{gesC result} compared to t _gesD . In fact, the total thickness is in the range of 5a smaller than the one after the cut 5b ie: _{not gesD}

Around 5a So is a greater elastic pressure compression compared to the situation after the 5b in front.

It must, of course, be taken into account and ensured that the respective materials A and B are evidently the same 3 deform only in the elastic range. Otherwise, additional non-linearities would have to be taken into account, which is a reasonable interpretation of the compensation element 4 to make impossible. As a result, ultimately, the "softer" of the two materials A, B, in the example of the material B, the maximum elastic range of use NB of the entire compensation element 4 firmly. Because this maximum utilization range NB according to the 3 extends only over the linear range of the associated modulus of elasticity ε _B compared to the applied compression or surface pressure σ.

For the compensation element after the 4 and 5 a substitute elastic modulus ε _{e can be} specified. In practice, courses of the replacement elastic modulus ε _e (x, y) are conceivable, as shown schematically in FIGS 7 to 9 are shown. One recognizes a kind of "saddle surface", which corresponds to location-dependent varying moduli of elasticity in both the x and y directions and thus is capable of complex crevices 3 to master tool halves, as exemplified in the 2a are shown.

Instead of the compensation element 4 made of two materials A and B, it is also possible to use only a single material A, as in 6 is shown. In this case, the resulting substitute elastic modulus ε _e (x, y) is varied as a function of location, such that a cavity 10 given expansion in the material A is introduced. Usually one will work at this point with a "hard" material A, while the cavity 10 is either "empty" or - as in the embodiment - inside a "soft" support core of the material B receives. So the compensation element 4 between a clamping surface 1 or an associated worktop and the machine construction 8th or the lower beam 9 the location-dependent different surface pressures P _i (x, y), i = 1, 2, 3, ... is able to follow, has the compensation element 4 each outside on a Einfederspalt 11 with end stop. This one is split by two 11 limiting core holders 12 formed between them the cavity 10 take up. The same structure after 6 joins in the right part along a symmetry axis S. This also applies to the 4 ,

In the compensation element 4 it can also be a two-dimensional matrix, which is made up of different segments, each with different spring characteristics. In other words, the invention also includes embodiments such that these segments are constructed as shown in FIGS 4 and 5 respectively. 6 is shown. These individual segments can be joined together in the manner of a matrix, so that a course of the replacement elastic modulus ε _e can be represented, as exemplified by the subject matter of FIGS 7 is. One recognizes by means of the 7 that the compensation element 4 in this way has a locally varying substitute elastic modulus ε _e (x, y), which assumes different values in both the x and y directions. Consequently, the replacement elastic modulus ε _e (x, y) can be adapted to the locally expected total loads from, for example, deflection, shear deformation, compression, etc.

These total loads can also be expressed in a matrix by associated surface pressure values P _i (x, y) with _i = 1, 2, 3, 4. 1a ). The compensation element 4 and an associated tool usually form a unit. This unit can be used flexibly on different machines after a "calibration". As part of this calibration, the required actuation forces and the resulting deformations are defined and the interpretation of the associated compensation element 4 , - Finally, based on the 7 to 9 clearly that the respective substitute elastic modulus ε _e (x, y) can have both a progressive, degressive and linear arts-dependent course.

Claims (8)

Device for compensating deformations on clamping surfaces ( 1 ) of machines ( 2 ), wherein at least one in the region of the clamping surfaces ( 1 ) arranged compensating element ( 4 ), which has at least two location - dependent different moduli of elasticity (ε _A , ε _B , ε _e ) whose respective size is adapted to the expected different surface pressure (P ₁ , P ₂ ) in such a way that the total deformation (t _ges ) of Machine ( 2 ) including compensating element ( 4 ) over the entire loaded clamping surface ( 1 ) is formed within predetermined limits the same, wherein the compensation element ( 4 ) as between machine part ( 6 . 8th ) and clamping surface ( 1 ) inserted adapter ( 4 ) or in the machine part ( 6 ) integrated component is formed and wherein the compensation element ( 4 ) is formed as a solid body in the longitudinal direction of a sandwich of two or more layers of different materials (A, B) with different moduli of elasticity (ε _A , ε _B ) and with optionally varying thickness (t _A , t _{B '} ), or the compensating element ( 4 ) made as a single material (A) predetermined modulus of elasticity (ε _A ) manufactured body with introduced cavity ( 10 ) for reducing the associated modulus of elasticity (ε _B ) is carried out at this point, wherein the cavity ( 10 ) is completely or partially filled with a support core. Apparatus according to claim 1, characterized in that the expected surface pressure (P ₁ , P ₂ ) is empirically determined by experiments or by means of simulations location-dependent and from these results, the respective location-dependent elastic modulus (ε _A , ε _B , ε _e ) is derived. Apparatus according to claim 1 or 2, characterized in that in a sandwich-type compensating element ( 4 ) as material (A, B) Iron material (A) and a plastic (B) high strength use find. Device according to one of claims 1 to 3, characterized in that the different moduli of elasticity (ε _A , ε _B ) have a preset relationship to one another. Device according to one of claims 1 to 4, characterized in that the compensating element ( 4 ) is constructed of segments with different modulus of elasticity (ε _A , ε _B ). Device according to one of claims 1 to 5, characterized in that the compensating element ( 4 ) has a locally varying replacement elastic modulus (ε _e (x, y)) which is adapted to the total loads or surface pressures (P _i (x, y)) to be expected there. Apparatus according to claim 6, characterized in that the spring characteristic of the compensating element ( 4 ) is described by the substitute elastic modulus (ε _e (x, y)) which, depending on the design, has a progressive, degressive or linear location-dependent course, both in one direction (x) and in one plane (x-, y-plane). Device according to one of claims 1 to 9, characterized in that the compensating element ( 4 ) and an associated tool form a unit which, taking into account the required actuating forces has a defined deformation and thus can be used independently of the machine.

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