Patent Application
20070193644
The invention relates to a method for producing a wire rope.
Furthermore the invention relates to an application of such a method.
The invention has the object to design a wire rope with new properties.
According to the invention, this object is met in that the wires are already made in the rope configuration by means of layer composition.
The wire rope created in this way does not have the tensile strength of a normal wire rope. It is only used for special purposes. Its advantage lies in that fact that it is neither influenced by quality fluctuations of the primary material nor by fluctuations of the production parameters. The wire rope may be deployed in cases where its absolute evenness can be exploited.
The normal wire ropes are subject to fluctuations in material and in the diameter of the wires as well as fluctuations of a great number of production parameters ranging from the wires, to the strands, and to the rope, where applicable, the core rope and terminal rope.
The wires can come from different steel charges and furthermore from other reduction steps with various cross-section reductions and thus have or incur various compositions, initial strengths, longitudinal stretching and increases in strength.
As a result of fluctuations in machine settings, such as preforming, spooling deceleration, straightening roller settings and reversed rotation both during the strand production and, where applicable, the multi-stage rope production, differing properties pertaining to diameter, elongation, twisting and torque performance as well as internal stresses, can have arisen to a non-negligible degree across the entire length of the wire rope.
During the production of samples for the development of the rope, one aims to at least use wires from the same producer. However, even in this case there are occasionally variations. Over the course of production the manufacturer may be switched repeatedly which can again lead to further changes in the wire rope.
In cases in which only short wire ropes are required and uniformity is a decisive factor, the wire ropes according to the invention thus have an advantage.
The most significant advantage results from the design that the wires are respectively molded directly to the coupling pieces located at the end of the wire rope.
The normal wire ropes are furnished with press sleeves or fanned out and fused. The discontinuity of the rope structure at these places has an effect far into the wire rope. Short ropes are therefore particularly irregular, while the sockets made by the hand at the ends lead to additional unavoidable inaccuracies and their related effects.
If, for example, several short wire ropes must interact absolutely evenly, for instance for control purposes in astronautics, the wire ropes according to the invention with molded coupling pieces are positively an advantage in spite of high production costs.
The production of samples for obtaining raw data for an optimization of a wire rope design is an important application area of the method according to the invention, wherein samples of a core rope and/or rope having an essentially identical rope structure, however different wire diameter and/or lay lengths of the strands are made and the properties of interest can be ascertained.
In order to find, for example, the best lay length for the core rope and the best lay length for the rope, i.e. the subsequent stranded outer strand position, for a multi-layer wire rope, a number of sample ropes with different core rope lay lengths and different rope lay lengths are made.
Five to nine samples, for example, are then cut with lengths of 1 to 20 m, in order to determine the E-modulus, breaking strength and overstraining in a pull test; further common tests include the torque test, the rotation angle test, the flexibility test, the bending stress test and the pulsating tensile stress test.
An otherwise desirable larger number of variations is not possible due to the size of the costs.
The costs, as already mentioned above, are again increased by means of the interference of the rope interconnection in the end areas of the sample ropes.
Based on the method according to the invention, the samples can be made in the shape of one-piece test pieces, in which the wires are respectively molded directly to the coupling pieces located at the ends.
The test pieces made in this way having a length of for example only 10 to 20 cm and the metal structure and surface of the wires, cannot however be equated with the samples of wire ropes which are made by means of stranding pulled wires. Different absolute values are found in the tests.
In relation to the values, however, the influences of geometry, i.e. of the wire diameter and of the lay length changes, can also be identified herein. A comparison of values found in samples made according to customary mode of production, can reveal, for example, correction values which could be taken into account.
The test pieces can be utilized in combination with a correspondingly reduced number of common rope samples for an optimization problem.
The small length of the test pieces is not a disadvantage. In all mentioned tests with the exception of the bending stress test, the length of the sample either had no impact or an impact which is computable.
The advantages achieved on the other hand are considerable.
The measurement results for conventional test ropes not only depend on the change of the rope parameters, but they are also superimposed by the above mentioned variances from production. As generally known, this can lead to big errors given an unfavorable concurrence of events. In contrast, the differences in measurement results can almost entirely be attributed to parameter changes using the uniform test pieces according to the invention.
The problem of wire availability and diameter tolerances which is associated with the conventional production of test ropes is completely omitted.
The interference of the rope structure at both the ends is only minimal and largely negligible. The wires are not bent a priori at the end by the holder or deformed in their cross section. They merge into the coupling piece on their entire cross section in the same material.
The already mentioned advantages, however, would likewise apply to test pieces made according to the invention without the molded coupling pieces.
According to a further embodiment of the invention, the composition of the wires is started in a wire position relative to each other which corresponds to or approximates the contact pressure of the wires onto each other under load of the wire rope, and the wires are fanned out on a subsequent short section to such an extent that they can then be built up separately from each other if necessary. At the end the process proceeds accordingly.
In this way a small discontinuity of the rope structure at the ends, possibly even occurring according to the invention, is mitigated and its impact into the length of the wire rope is shortened:
The wires built separately from each other press against each other under load on their length, however are kept at the original distance at the ends. This distance is larger without the preceding measure, so that a fanning out of the wires toward the end results.
The proposed reversed fanning out closes, on the other hand, under load and a slight bending of the wires, and the rope geometry remains constant to the end.
Inasmuch as interference from the bending of the wires is detected, it is possible to implement the measure only to a limited extent and still find an advantageous compromise between the corresponding bending of the wires and the fanning out of the wires toward the end.
Analogously, the composition of the wires can be started at an angle of the wires to the cross sectional plane of the wire rope, which is equal to or approximates the angle when loading the wire rope; the wires are then deflected at that angle which is designed to be without load.
The mentioned position of the wires relative to each other which corresponds to the contact pressure means that the wires are joined together in that position. The wire rope thereby receives cohesion, even if the wires are not molded to coupling pieces.
In a position at a distance from each other, the wire ends could be connected by means of webs that are built up between them.
Coupling pieces could also be welded or molded, if necessary also glued, to such ends of a wire rope.
On the one hand, one will generally aim to keep the test piece as short as possible, so that the aspect ratios (wire diameter to height) for the layer structure do not get too high. On the other hand, the test pieces should after all have a length of at least the biggest lay length of a strand, a core rope or of a rope contained in the test pieces, so that a rope-characteristic performance is achieved.
The slender wire ropes allow, according to a further embodiment of the invention, for a number, preferably a multitude of wire ropes to be produced in the same work step.
However, this not only implies the obvious rationalization associated therewith. Production variances resulting from deviations between different work steps are additionally eliminated, which again, in this case however, only occur to a very minor extent.
The material cannot be comparable to that of real wires. The usually present metallurgic possibilities do not exist; the textures created by milling and pulling of the wires can be reproduced.
According to the material applications known within the scope of selective laser meltings, a single component material, and therefore steel, however, can be selected, and the steel powder can be completely melted on locally by means of a laser beam, so that the material of the produced wires essentially presents a continuum. Approximately half of the tensile strength of normal wires is achieved.
If necessary the test piece can still undergo metallurgic heat treatments as a whole.
Titanium may also be considered as a material.
The wire rope could also only comprise a single strand.
The technique of the layer composition is known in several variations. A repetitive process cycle comprising 3 steps is the common principle. First, a vertically traveling building platform is lowered by the amount which is predetermined by the layer thickness. Then, a material layer, for example, powder is applied such that the preceding layer is completely covered at the hardened places as well as at places which are not hardened. In a final step the component data of the most recent layer provided in a 3D CAD is transferred to the material by means of energy radiation, in order to harden it in places. The steps are repeated until the component is built. Several systems are known which differ in the materials to be processed, the energy source, and in additional process steps.
Selective laser melting is applied for producing identical prototypes in batches, inserts with contour-fitted cooling ducts for tool and mold making as well as for other components with a hollow structure; and furthermore, single components such as medical individual implants and small batches.
In contrast, neither parts usable in a standard way nor parts which are exactly identical in form to such parts are made by applying the method according to the invention.
The test pieces are entities of their own which are only designed and usable for determining the property values in correlation with certain geometries, wherein these results can not yet be used directly and only lead to construction data which is of practical use after considering similarity correlations.
The invention is illustrated in the drawings which are described in detail as follows:
A raisable and lowerable platform 2 is arranged as a base in a duct 1, so that a chamber 3 having a variable depth is formed. The chamber 3 merges at its top side into a process chamber 4 having a greater cross section. A powder application device 5 located in the process chamber 3 which is filled with a protective gas is movable above the length of chamber 3. The powder application device 5 itself is to be filled by means of a feeding device 6 connected to a storage container.
A laser beam source 9 with a control device for the laser beam 10 which is steered from a CAD system onto the X-Y coordinate is arranged over a fixture 8 of the process chamber 4 which is equipped with a coupling window 7.
In the chamber 3, three wire ropes 12 which are in the process of being built, extend at the height of the chamber in a metal powder pour 11.
The cross section of the wire rope 12 is shown on a larger scale in
The powder application device 5 moves above the chamber 3 and evenly applies a layer with a thickness of, for example, 20μ over the metal powder pour 11 and the wire cross sections.
The metal powder for example consists of tool steel 1.2343, high-grade steel 1.4404 or steel 42 TrMo4. It has a grain size of <45μ, but could also be even finer.
After the first layer is laid the laser beam, for example, with a chart speed of 100 mm/sec is guided on parallel paths over the metal powder pour 11 and the metal powder layer resting on the wire. It is, however, only activated on those cross section sections in which the wires are to be built. The appropriate geometry data is provided in the shape of a 3D CAD model in the CAD system. The CAD model is dissected by means of special software into layers with the appropriate layer thickness. The laser beam source and the control of the laser beam are steered accordingly.
The laser beam has an effectiveness of, for example, a diameter of 200μ in its surrounding area. Accordingly, the mentioned % paths are located next to each other at a distance of 100μ. The effective depth of the laser beam is approximately equal to the layer thickness, i.e., for example, 20μ.
At the borders of the wire cross sections the activating of the laser beam source is delayed and the turning off is accelerated according to the effectiveness diameter of the laser beam in order to exactly produce a wire diameter of, for example, 1.5 to 2 mm.
After extracting the finished wire ropes 12, the metal powder located in their hollow spaces is removed by shaking, knocking, blowing, washing and/or the like is removed down to minor residue.
For this purpose, the short wire rope can also be expanded slightly in the elastic deformation area by twisting and/or compression. These can be alternately expanded slightly where lay directions are in opposition to each other in different cross section areas by tightening the other area more intensely.
Axial outlet ducts may be recessed at least in the extension of the strand gusset areas in molded coupling pieces.
| Number | Date | Country | Kind |
|---|---|---|---|
| 103 42 209.9 | Sep 2003 | DE | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP04/09891 | 9/4/2004 | WO | 11/3/2006 |
